1999 Vol. 17, No. 4
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Display Method:
1999, 17(4): 499-508.
Abstract:
Permian sequence stratigraphy in different kinds of sedimentary basins in South China is discussed in this paper,which is based on the great geological investigation on a large scale and analyses of previous works. Eleven depositional sequences S1 S11 are recognized in Permian in most Parts of South China,in which the S1 S3,S4 S6,S7 9 are determined in Qixia Stage,Maokou Stage and Wujiaping Stage respectively,and the S 10 S 11 are limited in Changxiny Stage.of them,the depositional sequences S1,S6,S7,S11 have a feature of the type-Ⅰ sequence boundary surface,and others have a feature of the type-Ⅱ surface.S 1 or S 2 depositional sequences could not be deposited somewhere between the Carboniferous and Permian,also S3 or S5 could not be between the Lower and Upper Permian. There are variable indicators for distinguishing the boundary surface types in all of the upper,middle and lower Yangtze Craton accoriding to comparison in South China.Clay layers with high Fe and Al,paleokarst fills with meteoric dolomite,and dolomitic caps are easily found on both type-Ⅰand type-Ⅱ boundary surfaces in the upper Yangtze Craton and its margins,and isolated carbonate platform.There are little exposure markers on boundary surfaces of most depositional sequences in the middle and lower Yangtze Craton except the basal boundary surface of the S7 in the middle craton and the S9 in the lower eraton.We think it might be related to the different tectonic settings of sedimentary basins. Loss of depositional sequences is also characterized by another way. S3 to S5 depositional sequences are difficult to be found out in most basins nearby paleocontinents.One example is that S4 or S5 in the S7 S11 could not be tracked at Hechi,Guangxi,and Xishui,Guizhou in the north of the Daxin paleocontinent.It is proposed that this could be the result of the Dongwu Movement,which leaded to the formation of Daxin Paleocontinent,South Yangtze River Paleocontinent and Yunkai Paleocontinent. It is supposed that the HSTTST pattern of depositional sequences in Yangtze Craton and its margins.western Cathayan Craton margin was influenced by tectonism of the Pacific tectonic field.And the HSTTST pattern in Youjiang Basin and Qingzhou-Haifang Strike-slip Basin,and host Cathayan Craton to a great extent was controlled by the Tethys tectonic field. It can be correlative on the amount,hierarchy,and boundary surface of the depositional sequences in the Lower Permian among North America,Russia,and South China,but not be the depositional sequences in the Upper Permian among them.It is inferred that the divergence of Pangea could be responsible for the situation.Any of the depositional sequences in South China has no analogues in North China.
Permian sequence stratigraphy in different kinds of sedimentary basins in South China is discussed in this paper,which is based on the great geological investigation on a large scale and analyses of previous works. Eleven depositional sequences S1 S11 are recognized in Permian in most Parts of South China,in which the S1 S3,S4 S6,S7 9 are determined in Qixia Stage,Maokou Stage and Wujiaping Stage respectively,and the S 10 S 11 are limited in Changxiny Stage.of them,the depositional sequences S1,S6,S7,S11 have a feature of the type-Ⅰ sequence boundary surface,and others have a feature of the type-Ⅱ surface.S 1 or S 2 depositional sequences could not be deposited somewhere between the Carboniferous and Permian,also S3 or S5 could not be between the Lower and Upper Permian. There are variable indicators for distinguishing the boundary surface types in all of the upper,middle and lower Yangtze Craton accoriding to comparison in South China.Clay layers with high Fe and Al,paleokarst fills with meteoric dolomite,and dolomitic caps are easily found on both type-Ⅰand type-Ⅱ boundary surfaces in the upper Yangtze Craton and its margins,and isolated carbonate platform.There are little exposure markers on boundary surfaces of most depositional sequences in the middle and lower Yangtze Craton except the basal boundary surface of the S7 in the middle craton and the S9 in the lower eraton.We think it might be related to the different tectonic settings of sedimentary basins. Loss of depositional sequences is also characterized by another way. S3 to S5 depositional sequences are difficult to be found out in most basins nearby paleocontinents.One example is that S4 or S5 in the S7 S11 could not be tracked at Hechi,Guangxi,and Xishui,Guizhou in the north of the Daxin paleocontinent.It is proposed that this could be the result of the Dongwu Movement,which leaded to the formation of Daxin Paleocontinent,South Yangtze River Paleocontinent and Yunkai Paleocontinent. It is supposed that the HSTTST pattern of depositional sequences in Yangtze Craton and its margins.western Cathayan Craton margin was influenced by tectonism of the Pacific tectonic field.And the HSTTST pattern in Youjiang Basin and Qingzhou-Haifang Strike-slip Basin,and host Cathayan Craton to a great extent was controlled by the Tethys tectonic field. It can be correlative on the amount,hierarchy,and boundary surface of the depositional sequences in the Lower Permian among North America,Russia,and South China,but not be the depositional sequences in the Upper Permian among them.It is inferred that the divergence of Pangea could be responsible for the situation.Any of the depositional sequences in South China has no analogues in North China.
1999, 17(4): 509-520.
Abstract:
Based on the research on sequence stratigraphy of Permian in the south China with the purpose of oil-gas exploration,11 sequence-based lithofacies and paleogeography maps of Permian in the south china have been drawn up by ways of condensation and instantenity with mapping units of sedimentary systems tracts and key sequence boundary surfaces.In the light of sequence-based lithofacies and paleogeography maps,the characteristics and evolution of Permian sequence-based lithofacies and paleogeography have also been discussed in detail.The authors suggest that the evolution of sequence-based lithofacies and paleogeography of Permian bave obvious characteristics of inheritance,inhomogeneity,phase,orientation and synchronism.Inheritance is that the distrbutive feature of sea and land area.the extension direction and distrbutive precipitation of sedimentary facies zone of each stage of Lower Permian are approximately consistent with the tectonic setting and paleogeographic framework of Devonian and Carboniferous.The inhomogeneity shows that there are different characteristics and development process in different sedimentary basin.The phase indicates that the evolution of sequence-based lithofacies and paleogeography can be divided into 2 phases and 11 stages.The tectonic setting,basin feature and paleogeography of Upper Permian are different from that of Lower Permian,but in different depositional area,the development stags is similar.The paleogeography feature of Upper Permian is related to that of Lower Permian,and the evolution and development of biota approximately keep consistence with that of paleogeography. Compared to traditional lithofacies and paleogeography map sequence-based lithofacies and paleogeography map owns distinct advantages fo accuracy,isochronity,genetic succession and exploratory practicality etc.It deeply reflects the sedimentation,tectonic movement,sea-level change,distribution and evolution of sea and land, volcanic action and oil-formation etc.It also reasonably discloses the relationship of corrosion exposure field of old landmass and the development of sedimentary system with sea-level change and synsedimentary tectonic movement,and vividly describes the special distrbution and evolution of the sedimentary facies zone of coverage area.especially potential oil source,reservoir and cover,Clearly,sequence-based lithofacies and paleogeography map not only objectively and dynamically reflects the basin forming,development and evolution process but also have significant practical significance oil-gas exploration.
Based on the research on sequence stratigraphy of Permian in the south China with the purpose of oil-gas exploration,11 sequence-based lithofacies and paleogeography maps of Permian in the south china have been drawn up by ways of condensation and instantenity with mapping units of sedimentary systems tracts and key sequence boundary surfaces.In the light of sequence-based lithofacies and paleogeography maps,the characteristics and evolution of Permian sequence-based lithofacies and paleogeography have also been discussed in detail.The authors suggest that the evolution of sequence-based lithofacies and paleogeography of Permian bave obvious characteristics of inheritance,inhomogeneity,phase,orientation and synchronism.Inheritance is that the distrbutive feature of sea and land area.the extension direction and distrbutive precipitation of sedimentary facies zone of each stage of Lower Permian are approximately consistent with the tectonic setting and paleogeographic framework of Devonian and Carboniferous.The inhomogeneity shows that there are different characteristics and development process in different sedimentary basin.The phase indicates that the evolution of sequence-based lithofacies and paleogeography can be divided into 2 phases and 11 stages.The tectonic setting,basin feature and paleogeography of Upper Permian are different from that of Lower Permian,but in different depositional area,the development stags is similar.The paleogeography feature of Upper Permian is related to that of Lower Permian,and the evolution and development of biota approximately keep consistence with that of paleogeography. Compared to traditional lithofacies and paleogeography map sequence-based lithofacies and paleogeography map owns distinct advantages fo accuracy,isochronity,genetic succession and exploratory practicality etc.It deeply reflects the sedimentation,tectonic movement,sea-level change,distribution and evolution of sea and land, volcanic action and oil-formation etc.It also reasonably discloses the relationship of corrosion exposure field of old landmass and the development of sedimentary system with sea-level change and synsedimentary tectonic movement,and vividly describes the special distrbution and evolution of the sedimentary facies zone of coverage area.especially potential oil source,reservoir and cover,Clearly,sequence-based lithofacies and paleogeography map not only objectively and dynamically reflects the basin forming,development and evolution process but also have significant practical significance oil-gas exploration.
1999, 17(4): 528-535.
Abstract:
Sequence stratigraphy is an important method of basin analysis.Permian is an important evolution stage of Hercynian-Indo-Chinese Basin in the South China.The tectonic environment of the basin is under an extensional condition as a whole and the sedimentary basin can be divided into two classes including craton basin and extension rift basin.After the Dongwu movement,there exist squeezing foreland basin and arc rear basin due to partial basin environment changes.There are special characteristics in sequence stratigraphy of different sedimentary basin because the structural site sedimentation rate and geometry are different and they influence and control the sea level change.Permian system in the south China consists of eleven sequences corresponding to 3rd order cvcle and two supersequences corresponding to 2nd order cycle.Supersequence of Lower Permian is a complete cycle.Qixia epoch is composed of three sequences (S1-S3) corresponding to sea level rising stage of 2nd order cycle,Maokou epoch also consists of three sequences (S4-S6) corresponding to sea level descending period.The largest transgression period is in Lower Maokou epoch.The supersequence of Upper Permian is not complete only corresponding to a sea level rising period of 2nd order cycle The characteristics of sequences or supersequences are different not only in material constitution and geometry,but also in structure,composition and the boundary surface form,and it demonstrates that the types,evolution and characters of the basin have tightly inherent relationship. According to tectonic role,sedimentary characteristics,sea level change,sequence stratigraphy texture and paleogeography,the evolution of Hercynian Indo Chinese sedimentary basin in the south China can be divided into five stages and respectively corresponding to five 2nd order sea level change cycles.It indicates a process from the basin forming,developing to consuming with clear rhythm.The evolution of Permian sedimentary basin is in the transition process from mature stage to consuming stage.The basin in the south China comes into holaspid period in Lower Permian.The main proofs are:(a) the transgression field of the sea is the largest in this stage;(b) the deep water area of the extension basin is the largest;(c) there is the strongest basic volcanic activity of Hercynian Indo during Dongwu movement stage,and it cause this area to be protruded and disintergrated,the transgression field of the sea shortened and finally the property of some basin changed.The basic characteristics of the Permian basin are that a northwest extension basin is between two large cratons Yangzi and Huaxia and the development of the two cratons are not balanced.The central tension basin is formed by rifting again along Caledonian junction belt.This palaogeography framework is very similar to that of Caledonian.Therefore,we consider that the tectonic environment of Upper Palaeozoic era basin in the south China is not a stable craton environment.
Sequence stratigraphy is an important method of basin analysis.Permian is an important evolution stage of Hercynian-Indo-Chinese Basin in the South China.The tectonic environment of the basin is under an extensional condition as a whole and the sedimentary basin can be divided into two classes including craton basin and extension rift basin.After the Dongwu movement,there exist squeezing foreland basin and arc rear basin due to partial basin environment changes.There are special characteristics in sequence stratigraphy of different sedimentary basin because the structural site sedimentation rate and geometry are different and they influence and control the sea level change.Permian system in the south China consists of eleven sequences corresponding to 3rd order cvcle and two supersequences corresponding to 2nd order cycle.Supersequence of Lower Permian is a complete cycle.Qixia epoch is composed of three sequences (S1-S3) corresponding to sea level rising stage of 2nd order cycle,Maokou epoch also consists of three sequences (S4-S6) corresponding to sea level descending period.The largest transgression period is in Lower Maokou epoch.The supersequence of Upper Permian is not complete only corresponding to a sea level rising period of 2nd order cycle The characteristics of sequences or supersequences are different not only in material constitution and geometry,but also in structure,composition and the boundary surface form,and it demonstrates that the types,evolution and characters of the basin have tightly inherent relationship. According to tectonic role,sedimentary characteristics,sea level change,sequence stratigraphy texture and paleogeography,the evolution of Hercynian Indo Chinese sedimentary basin in the south China can be divided into five stages and respectively corresponding to five 2nd order sea level change cycles.It indicates a process from the basin forming,developing to consuming with clear rhythm.The evolution of Permian sedimentary basin is in the transition process from mature stage to consuming stage.The basin in the south China comes into holaspid period in Lower Permian.The main proofs are:(a) the transgression field of the sea is the largest in this stage;(b) the deep water area of the extension basin is the largest;(c) there is the strongest basic volcanic activity of Hercynian Indo during Dongwu movement stage,and it cause this area to be protruded and disintergrated,the transgression field of the sea shortened and finally the property of some basin changed.The basic characteristics of the Permian basin are that a northwest extension basin is between two large cratons Yangzi and Huaxia and the development of the two cratons are not balanced.The central tension basin is formed by rifting again along Caledonian junction belt.This palaogeography framework is very similar to that of Caledonian.Therefore,we consider that the tectonic environment of Upper Palaeozoic era basin in the south China is not a stable craton environment.
1999, 17(4): 542-546.
Abstract:
The carbon,oxygen and strontium isotope composition of marine carbonate is mainly controlled by global events,such as relative amount of organic accumulation and oxidation,orogenic events,glacial activity,changes in seafloor spreading rate and palaeoclimate variation.The evolution tendency of isotopes with the same stratigraphy interval is similar.This is the fundamental principle of isotope stratigraphy.However,carbonate sediments are normally absent in deep sea environment,we could not obtain the data of carbon and oxygen isotopes,but the deep sea sediments with few fossils specially need the supports of isotope stratigraphy.For this reason,we collected siliceous rock samples from deep sea environment,researched their strontium isotope and set up evolution curves to seek after their application foreground in isotope stratigraphy. The deep sea siliceous rock samples studied here were collected from the sedimentary section from Earlier Carboniferous to Earlier Permian,Qinzhou,Guangxi.Based on the analysis of X ray diffraction and cathodoluminescence of the collected samples,they should be chemical precipitation from seawater.After age correction based on the Rb/Sr ratio,we obtained the original 87Sr/86Sr values and set up the evolution curve which is similar to that of shallow water carbonate from the same age in Upper Yangtze Platform.It supports the notion of a global consistency in strontium isotope composition of marine interior sediments.However,because we could not eliminate effect from terrigenous clastics with higher 87 Sr content,the average of 87Sr/86Sr values form siliceous rocks is observably higher than that from carbonate rocks.Additionally the lower 87Sr/86Sr ratio record of carbonate in Earlier Permian was probably caused by substantial basalt eruptions on Upper Yangtze Platform at the time.The strontium data exhibit three intervals of relatively low 87Sr/86Sr ratio in Earlier Carboniferous,earlier stage of Late Carboniferous,and Earlier Permian,corresponding to global eustatic high sea level stands.The strontium data exhibit one intervals of relatively high 87Sr/86Sr ratio in Late stage of Late Carboniferous corresponding to global eustatic lower sea level stands.
The carbon,oxygen and strontium isotope composition of marine carbonate is mainly controlled by global events,such as relative amount of organic accumulation and oxidation,orogenic events,glacial activity,changes in seafloor spreading rate and palaeoclimate variation.The evolution tendency of isotopes with the same stratigraphy interval is similar.This is the fundamental principle of isotope stratigraphy.However,carbonate sediments are normally absent in deep sea environment,we could not obtain the data of carbon and oxygen isotopes,but the deep sea sediments with few fossils specially need the supports of isotope stratigraphy.For this reason,we collected siliceous rock samples from deep sea environment,researched their strontium isotope and set up evolution curves to seek after their application foreground in isotope stratigraphy. The deep sea siliceous rock samples studied here were collected from the sedimentary section from Earlier Carboniferous to Earlier Permian,Qinzhou,Guangxi.Based on the analysis of X ray diffraction and cathodoluminescence of the collected samples,they should be chemical precipitation from seawater.After age correction based on the Rb/Sr ratio,we obtained the original 87Sr/86Sr values and set up the evolution curve which is similar to that of shallow water carbonate from the same age in Upper Yangtze Platform.It supports the notion of a global consistency in strontium isotope composition of marine interior sediments.However,because we could not eliminate effect from terrigenous clastics with higher 87 Sr content,the average of 87Sr/86Sr values form siliceous rocks is observably higher than that from carbonate rocks.Additionally the lower 87Sr/86Sr ratio record of carbonate in Earlier Permian was probably caused by substantial basalt eruptions on Upper Yangtze Platform at the time.The strontium data exhibit three intervals of relatively low 87Sr/86Sr ratio in Earlier Carboniferous,earlier stage of Late Carboniferous,and Earlier Permian,corresponding to global eustatic high sea level stands.The strontium data exhibit one intervals of relatively high 87Sr/86Sr ratio in Late stage of Late Carboniferous corresponding to global eustatic lower sea level stands.
1999, 17(4): 553-559.
Abstract:
The Wuliyasitai faulted basin,a typical faulted basin in Erlian basin group,is bounded by a listric normal fault on the northwestern side of the basin,with very thick marginal fan complexes indicating contemporaneous sedimentation along the faults.It is infilled with Jurrasic and Early Cretaceous sediments of up to 5 000 m in thickness which a series of different scale hiatuses and tectonic events have been discerned during hydrocarbon exploration in the basin.In this present paper the principle and method of high-resolution sequence stratigraphy are adopted to deal with seismic reflection profiles and well logs data.the various orders of sequence boundaries have been identified and the sequence stratigraphic framework of Wuliyasitai faulted basin has been reconstructed.According to regional and local unconformity and corresponding conformities,the basin infillings of the basin may be subdivided into two tectonic sequences,represented by J 1～J 2 (TC1)and K 1(TC2)rifting type filling sequences,respectively,which constituted two proto-type basins developing in two rifting stages,among which the major infilling sequence TC2 may be further subdivided into four sequence sets and eleven sequences.Generally,the boundaries of tectonic sequences were regional unconformities,and the unconformity boundaries of sequence sets can be traced on a basin scale,while the unconformity boundaries of sequences only developed in basin margins or intrabasin uplift,which merged into conformity boundaries toward center part of basin.Based on the sequence stratigraphic framework,sequence system tracts that are characterized by one-lay type system tract,often developed in initial and final evolution phrases of basin,and the two-lay type system tracts consisting of fining-upward tract,i.e,expanding lacustrine system tract and coarsening upward tract,i.e,contraction lacustrine system tract have been reconstructed.Unlike depositional systems of sea basin, in lacustrine basin like the Wuliyasitai faulted basin subaqueous fan, deep lake turbidite fan and fan delta developed generally in highstand phrase of lake level. Basin tectonic subsidence rate and total subsidence rate computed by backstripping method show three changes from fast to slow,which corresponds with three sequence sets stated above,indicating that the basin underwent thee stretching episodes during synrifting stage,which have been interpreted asa result of a multiple stretching of the lithosphere.The episodic tectonism of the basin,showing clear relationship to depositional fillings of the basin,is a major controlling factor of the formation of higher-order sequences in the basin,such as tectonic sequence and sequence sets,and controlled the development of sequences to a certain content.The conclusions have been applied to the prospect of reservoir and hydrocarbon source-rock distribution and lithologic-stratigraphic traps in this basin,and proved to be effective.
The Wuliyasitai faulted basin,a typical faulted basin in Erlian basin group,is bounded by a listric normal fault on the northwestern side of the basin,with very thick marginal fan complexes indicating contemporaneous sedimentation along the faults.It is infilled with Jurrasic and Early Cretaceous sediments of up to 5 000 m in thickness which a series of different scale hiatuses and tectonic events have been discerned during hydrocarbon exploration in the basin.In this present paper the principle and method of high-resolution sequence stratigraphy are adopted to deal with seismic reflection profiles and well logs data.the various orders of sequence boundaries have been identified and the sequence stratigraphic framework of Wuliyasitai faulted basin has been reconstructed.According to regional and local unconformity and corresponding conformities,the basin infillings of the basin may be subdivided into two tectonic sequences,represented by J 1～J 2 (TC1)and K 1(TC2)rifting type filling sequences,respectively,which constituted two proto-type basins developing in two rifting stages,among which the major infilling sequence TC2 may be further subdivided into four sequence sets and eleven sequences.Generally,the boundaries of tectonic sequences were regional unconformities,and the unconformity boundaries of sequence sets can be traced on a basin scale,while the unconformity boundaries of sequences only developed in basin margins or intrabasin uplift,which merged into conformity boundaries toward center part of basin.Based on the sequence stratigraphic framework,sequence system tracts that are characterized by one-lay type system tract,often developed in initial and final evolution phrases of basin,and the two-lay type system tracts consisting of fining-upward tract,i.e,expanding lacustrine system tract and coarsening upward tract,i.e,contraction lacustrine system tract have been reconstructed.Unlike depositional systems of sea basin, in lacustrine basin like the Wuliyasitai faulted basin subaqueous fan, deep lake turbidite fan and fan delta developed generally in highstand phrase of lake level. Basin tectonic subsidence rate and total subsidence rate computed by backstripping method show three changes from fast to slow,which corresponds with three sequence sets stated above,indicating that the basin underwent thee stretching episodes during synrifting stage,which have been interpreted asa result of a multiple stretching of the lithosphere.The episodic tectonism of the basin,showing clear relationship to depositional fillings of the basin,is a major controlling factor of the formation of higher-order sequences in the basin,such as tectonic sequence and sequence sets,and controlled the development of sequences to a certain content.The conclusions have been applied to the prospect of reservoir and hydrocarbon source-rock distribution and lithologic-stratigraphic traps in this basin,and proved to be effective.
1999, 17(4): 566-571.
Abstract:
Debris flow sedimentary strata consisted of mixed deposites of sands and conglomerates are the most significant oil and gas reservoir in alluvial fans developed along the steep-slope in Mesozoic-Cenozoic Fault Basins, Eastern China. Based on a case study of cores through Yong-an alluvial fan, Dongying Basin, the lithological characteristics of deberis flow deposits were firstly generalized,which are (1)conglomerate with a complex component,a poor degree of sorting and a very poor roundness;(2)a typical matrix support texture with the gravel axis directed randomly;(3)the common gravity structures as the massive,the fiamme and the deformation bedding ect.,the common bottom surface consisted of well developed erosion surface. Three types of vertical sequence of debris flow sedimentary unit were recognized and modelized,and they are(1) the fining upward sequence mainly developed in the upper fan area,with the fining upward either gradually or in a multicycle way;(2)the nongraded sequence typically formed in the main channels in the upper fan facies and (3)the composite graded sequences combined with a lower corsing upward interval and an upper fing upward interval and,this type of sequence is hardly well developed due to the strong erosion in the alluvial fan area. Bsed on the studies above,a complete sequence model of alluvial fan unit was suggested.This complete unit was composed of three intervals,that is (1)the lower coarsing upward sand fine gravel interval which was deposited in the first debris forming stage,(2)the thick middel upper fining upward interval that was formed in the typical debris developing stage and (3)the upper sandy interval seposited in the water channels during the past flood time.Futhermore,the lower interval can be recognized into two subintervals named ?sandy part formed in normal tractive current channels before flood and the fine gravel part deposited in the low dense debris at the first stage of flood;the middle upper interval can also be devided into two subintervals,that is the thick middle lower coarse conglomorate as a result of normal debris;?the fine conglomerate corresponding to the late stage of a flood;the upper interval is right the subinterval ?Because of the strong erossion process,the complete sequence of ,were not common in strata record,contrastly,the sequences like, ect.were very common.Understanding the sequuence model would be of significance to sedimentological and reservoir studies of alluvial fan in lacustrine basins.In order to understand the permeability structure of a commplete debris unit in profile,a corresponding reservoir characteristic model was finally established based on a number of core permeability test in lab,and the testsshowed that the thin subinterals ?and ?be well permeable,the was relative poor,and the ?? have a great range.So,the high remindering oil should tend to be formed in a debris reservoir unit.
Debris flow sedimentary strata consisted of mixed deposites of sands and conglomerates are the most significant oil and gas reservoir in alluvial fans developed along the steep-slope in Mesozoic-Cenozoic Fault Basins, Eastern China. Based on a case study of cores through Yong-an alluvial fan, Dongying Basin, the lithological characteristics of deberis flow deposits were firstly generalized,which are (1)conglomerate with a complex component,a poor degree of sorting and a very poor roundness;(2)a typical matrix support texture with the gravel axis directed randomly;(3)the common gravity structures as the massive,the fiamme and the deformation bedding ect.,the common bottom surface consisted of well developed erosion surface. Three types of vertical sequence of debris flow sedimentary unit were recognized and modelized,and they are(1) the fining upward sequence mainly developed in the upper fan area,with the fining upward either gradually or in a multicycle way;(2)the nongraded sequence typically formed in the main channels in the upper fan facies and (3)the composite graded sequences combined with a lower corsing upward interval and an upper fing upward interval and,this type of sequence is hardly well developed due to the strong erosion in the alluvial fan area. Bsed on the studies above,a complete sequence model of alluvial fan unit was suggested.This complete unit was composed of three intervals,that is (1)the lower coarsing upward sand fine gravel interval which was deposited in the first debris forming stage,(2)the thick middel upper fining upward interval that was formed in the typical debris developing stage and (3)the upper sandy interval seposited in the water channels during the past flood time.Futhermore,the lower interval can be recognized into two subintervals named ?sandy part formed in normal tractive current channels before flood and the fine gravel part deposited in the low dense debris at the first stage of flood;the middle upper interval can also be devided into two subintervals,that is the thick middle lower coarse conglomorate as a result of normal debris;?the fine conglomerate corresponding to the late stage of a flood;the upper interval is right the subinterval ?Because of the strong erossion process,the complete sequence of ,were not common in strata record,contrastly,the sequences like, ect.were very common.Understanding the sequuence model would be of significance to sedimentological and reservoir studies of alluvial fan in lacustrine basins.In order to understand the permeability structure of a commplete debris unit in profile,a corresponding reservoir characteristic model was finally established based on a number of core permeability test in lab,and the testsshowed that the thin subinterals ?and ?be well permeable,the was relative poor,and the ?? have a great range.So,the high remindering oil should tend to be formed in a debris reservoir unit.
1999, 17(4): 578-583.
Abstract:
It is generally recognized that depositional bodies in high energy environment are favorable sedimentary facies for reservoir to form and evolve,but to carbonate deposits,depositional bodies in high energy environment are only one of fundamental factors which are suitable to the reservoir development,and influence of diagenesis in later stage may be more obvious,diagenesis can change depositional bodies in high energy environment which were dominated by primary porosity in early stage into dense one or into reservoir dominated by secondary porsity, so prediction and study on carbonate reservoir should integrate the study on sedimentary facies and diagenesis. According to macro and micro characteristics of cores from seven wells in Dengying Formation,Ziyang Sichuan,combining with data of physical property,the authors studied in detail the types of bank facies depositional bodies,features of the assemblages,main diagenetic events and the influence on reservoir property.The study indicates that nine micro lithofacies deposited in high to relatively high energy environment were developed within the the depositional bodies in Dengying Formation,which are sparry dolarenite,sparry spongiostromata dolarenite,grain bound dolostone,algal bound crumb dolostone and sparry oolitic dolostone etc.,vertically and laterally,the lithofacies overlap to form intraclast bank,spongiostromata clast bank,algal bound grain bank and oollitic shoal,the bank facies bodies superimposed other related ones to form five types of lithofacies assemblage which was related to bank facies deposition:the single bed of the bank facies bodies and related lithofacies assemblages are of small scale and thickness,vertically,the beds appeared as lens-like and laminate ones repeatedly occur in middle and upper parts of Dengying member Two and middle and lower parts of Dengying member Three,laterally,it is difficult to trace and correlate the single bed in a long distance within the wells,on plane,they distribute at all wells,but there is a great difference in the types of bank bodies and degree of development.Before and after diagenesis,there is an apparent change of reservoir property of the bank facies bodies;the change is tightly related to textural composition characteristics of bank facies bodies and cementation,recrystallization and burial dissolution happened during diagenesis.In the bank facies bodies,although most of primary intergrain porosity and algal bound bank are hardly preserved as pore space,depositional facies will help to form favorable environment for reservoir to form and evolution because of lack of undissolved residues such as algal and clay,which are suitable to recrystallization and burial dissoluteness to develop more secondary porosity;and such dark-colored banks as gray-dark algal bound grain bank contain more undissolved residues,the primary porosity in which will vanish after cementation by multi-phase sparry dolomite,and there is only a weak later stage diagenesis,the banks turn to non-reservoir facies.The light-colored bank facies bodies which are favorable for the formation and evolution of reservoir are mainly distributed in the area centralized by Zi Well 3,Zi Well 7,from the area,favorable facies bodies get thinner and the reservoir property poorer and poorer.
It is generally recognized that depositional bodies in high energy environment are favorable sedimentary facies for reservoir to form and evolve,but to carbonate deposits,depositional bodies in high energy environment are only one of fundamental factors which are suitable to the reservoir development,and influence of diagenesis in later stage may be more obvious,diagenesis can change depositional bodies in high energy environment which were dominated by primary porosity in early stage into dense one or into reservoir dominated by secondary porsity, so prediction and study on carbonate reservoir should integrate the study on sedimentary facies and diagenesis. According to macro and micro characteristics of cores from seven wells in Dengying Formation,Ziyang Sichuan,combining with data of physical property,the authors studied in detail the types of bank facies depositional bodies,features of the assemblages,main diagenetic events and the influence on reservoir property.The study indicates that nine micro lithofacies deposited in high to relatively high energy environment were developed within the the depositional bodies in Dengying Formation,which are sparry dolarenite,sparry spongiostromata dolarenite,grain bound dolostone,algal bound crumb dolostone and sparry oolitic dolostone etc.,vertically and laterally,the lithofacies overlap to form intraclast bank,spongiostromata clast bank,algal bound grain bank and oollitic shoal,the bank facies bodies superimposed other related ones to form five types of lithofacies assemblage which was related to bank facies deposition:the single bed of the bank facies bodies and related lithofacies assemblages are of small scale and thickness,vertically,the beds appeared as lens-like and laminate ones repeatedly occur in middle and upper parts of Dengying member Two and middle and lower parts of Dengying member Three,laterally,it is difficult to trace and correlate the single bed in a long distance within the wells,on plane,they distribute at all wells,but there is a great difference in the types of bank bodies and degree of development.Before and after diagenesis,there is an apparent change of reservoir property of the bank facies bodies;the change is tightly related to textural composition characteristics of bank facies bodies and cementation,recrystallization and burial dissolution happened during diagenesis.In the bank facies bodies,although most of primary intergrain porosity and algal bound bank are hardly preserved as pore space,depositional facies will help to form favorable environment for reservoir to form and evolution because of lack of undissolved residues such as algal and clay,which are suitable to recrystallization and burial dissoluteness to develop more secondary porosity;and such dark-colored banks as gray-dark algal bound grain bank contain more undissolved residues,the primary porosity in which will vanish after cementation by multi-phase sparry dolomite,and there is only a weak later stage diagenesis,the banks turn to non-reservoir facies.The light-colored bank facies bodies which are favorable for the formation and evolution of reservoir are mainly distributed in the area centralized by Zi Well 3,Zi Well 7,from the area,favorable facies bodies get thinner and the reservoir property poorer and poorer.
1999, 17(4): 591-595.
Abstract:
The secondary pores account for a great proportion in the late Jurassic to the early Cretaceous (J3-K1) reservoir. The main types of secondary pores in the reservoirs are divided into four types as follows: inter-granular pores, intragranula pores, moldic pores, intracement pores and fracture and so on. The development mechanisms may have four kinds: the first one relates to the thermal evolution of organic matter in mudstones. R.C.Surdam and T.J.Crossey's experiments indicate that the thermal degradation makes kerogens seperate from the outer oxygen-functional groups such as carboxy groups, keto-groups, phenol and so on to produce a large amount of organic acid before it goes into the oil windows. When temperature arrives at 80℃—120℃, the consistency of the organic acid is in the highest degree. The secondary pores are developed after the organic acid solved in the water removing with the pore fluids from the source rocks, and entered into the sandstone reservoirs, and dissolved the unstable elements. This process mainly occurs at the stage of low maturation to maturation of the organic matter. Most of the secondary pores in our area firstly developed at A period of the late diagenesis stage and secondly at B period of early or late diagenesis stage, relating to the thermal evolution of the organic matter, and being identical with the expelling stage of organic acid. The second one relates to the infiltration of the surface and subsurface water. This can be seen in the north of Wuerxun down-faulted depression and Majiapu buildup of the Luxi depression. The distribution was directly controlled by the deposition break, also related to the composition of source region. The conditions of the reservoir of arkose derived from part of the granite are better than the lithic sandstone or lithic subarkose from volcanic rocks or sedimentary rocks. When the buried depth is deep enough, the porosity and permeability will be improved because of the seperating of organic acid and piling up of the secondary pores. The third one relates to the late volcanism. the volcanic movement makes the geothermal gradient rise and so it accelarates the speed of organic matter evolution of the source rocks and sandstone diagenesis. Therefore, we can hope to look for the development of the secondary pore zones in shallow depth,to develop a favourable reservoir with the primary pores piling up in the shallow depth. Volcanic eruption or magma intrusion are always accompanied by the hydrothermal movement. On the one hand, the hydrothermal movement made the veins inject the inter granular pore spaces and reduce the porosity and permeability of the sandstone greatly, on the other hand, the CO 2 given off by the hydrothermal liquid might be the factor of the development of the secondary pores in the deep buried zones with high geotemperature The forth one relates to the tectonic movement and diagenesis. The low porosity and permeability may be the main characteristics of the reservoirs in the late Jurassic to the early Cretaceous down-faulted basins in the northeastern China. The fissure plays an important rol in the reservoirs, especially in the compacted sandstone reservoirs and some special reservoirs, and become not only the effective paths of fluids but accumulative spaces as well. According to the fissure occurence, the fissures can be divided into microfissures and macrofissures, and by the origins, the fissures may be divided into tectonic fissures and diagenetic fissures.The tectonic fissures mainly possess a certain direction, penetrating (or not) the strata and extending faraway, and the fissure planes may be flat and straight.The observed diagenetic fissures of core are mainly irregular, and in the shape of the root of a tree. From the observation of a thin section, the fractur system appears multidimensional, including the grain fissures formed in the c
The secondary pores account for a great proportion in the late Jurassic to the early Cretaceous (J3-K1) reservoir. The main types of secondary pores in the reservoirs are divided into four types as follows: inter-granular pores, intragranula pores, moldic pores, intracement pores and fracture and so on. The development mechanisms may have four kinds: the first one relates to the thermal evolution of organic matter in mudstones. R.C.Surdam and T.J.Crossey's experiments indicate that the thermal degradation makes kerogens seperate from the outer oxygen-functional groups such as carboxy groups, keto-groups, phenol and so on to produce a large amount of organic acid before it goes into the oil windows. When temperature arrives at 80℃—120℃, the consistency of the organic acid is in the highest degree. The secondary pores are developed after the organic acid solved in the water removing with the pore fluids from the source rocks, and entered into the sandstone reservoirs, and dissolved the unstable elements. This process mainly occurs at the stage of low maturation to maturation of the organic matter. Most of the secondary pores in our area firstly developed at A period of the late diagenesis stage and secondly at B period of early or late diagenesis stage, relating to the thermal evolution of the organic matter, and being identical with the expelling stage of organic acid. The second one relates to the infiltration of the surface and subsurface water. This can be seen in the north of Wuerxun down-faulted depression and Majiapu buildup of the Luxi depression. The distribution was directly controlled by the deposition break, also related to the composition of source region. The conditions of the reservoir of arkose derived from part of the granite are better than the lithic sandstone or lithic subarkose from volcanic rocks or sedimentary rocks. When the buried depth is deep enough, the porosity and permeability will be improved because of the seperating of organic acid and piling up of the secondary pores. The third one relates to the late volcanism. the volcanic movement makes the geothermal gradient rise and so it accelarates the speed of organic matter evolution of the source rocks and sandstone diagenesis. Therefore, we can hope to look for the development of the secondary pore zones in shallow depth,to develop a favourable reservoir with the primary pores piling up in the shallow depth. Volcanic eruption or magma intrusion are always accompanied by the hydrothermal movement. On the one hand, the hydrothermal movement made the veins inject the inter granular pore spaces and reduce the porosity and permeability of the sandstone greatly, on the other hand, the CO 2 given off by the hydrothermal liquid might be the factor of the development of the secondary pores in the deep buried zones with high geotemperature The forth one relates to the tectonic movement and diagenesis. The low porosity and permeability may be the main characteristics of the reservoirs in the late Jurassic to the early Cretaceous down-faulted basins in the northeastern China. The fissure plays an important rol in the reservoirs, especially in the compacted sandstone reservoirs and some special reservoirs, and become not only the effective paths of fluids but accumulative spaces as well. According to the fissure occurence, the fissures can be divided into microfissures and macrofissures, and by the origins, the fissures may be divided into tectonic fissures and diagenetic fissures.The tectonic fissures mainly possess a certain direction, penetrating (or not) the strata and extending faraway, and the fissure planes may be flat and straight.The observed diagenetic fissures of core are mainly irregular, and in the shape of the root of a tree. From the observation of a thin section, the fractur system appears multidimensional, including the grain fissures formed in the c
1999, 17(4): 601-607.
Abstract:
There exists a sub-recent buried tidal sandbody system among standplain muddy deposit areas,with a fanshape stretching towards east from Dongtai and similar to that of the radial tidal sand ridge pattern in the southern Yellow Sea.The area of subaerial tidal sandbody system is about 3 000 km\+2.Tidal sedimentary structures,such as muddy streak,flaser structure and bi-direction cross-bedding,show tidal genesis of the sandbody system.The tidal sand strata are underlain by littoral unit or terrigenous hard clay and overlain by tidal flat deposits.\;Magnetic fabrics are measured and analyzed at two representative drilling cores,Tongshang and Xinhai,which have penetrated tidal flat strata,tidal sand body and hard clay.Two drilling cores ard sampled successively.The samples are measured and magnetic fabric parameters K、P、F、L and q are calculated,then successive curves of these magnetic fabric parameters are acquired.These curves show that K、P、F、L and q of the tidal sand body demonstrate an apparent difference from those of underlain paleosol and overlain strata,and lower and upper boundaries of the tidal sand body can be defined by the curves.There are abrupt changes of K、P and F at the boundary between tidal sand strata and the underlying paleosol,with sharply increasing of these parameters in the tidal sand strate.Thus.it can be inferrd that environmental energy in the tidal sand strata is abruptly increased.Under the strong and stable tidal current,the deposition is coincided with hydrodynamics and most of q is less than 0.5 in the tidal sand strata.However the hard clay(paleosol) formed in low energy environment of floodplain contains a lot of sedimentary units with q higher than 0.7,which corresponds to a quick deposition The tidal sand body unit transits gradunally upward to tidal flat deposits,but the boundary between them is still cleraly discernable by the magnetic fabric curves.Smaller K and P reflect hydrodynamic decline from the tidal sand body unit to tidal flat deposts.\;Abrupt variation of K and P within the tidal sand strata may reflect superimposition of sand ridge and tidal current trough depositional units in vertical profile,which shows micro-hydrodynamic changes on the tidal ridge and in the trough.Horizontally,that values of P、K in core Xinhai are higher than those in core Tongshang shows variations of hydrodynamics matching the convergent-divergent tidal current field in the study area.Contents of heavy minerals also show the similar tendency of tidal current changes.Besides,variations of K and content of varied magnetic minerals among heavy mineral also indicate multi-provenance of the study area,with“the Yellow River source” prominent at north and “the Changjiang Rover source” at south.
There exists a sub-recent buried tidal sandbody system among standplain muddy deposit areas,with a fanshape stretching towards east from Dongtai and similar to that of the radial tidal sand ridge pattern in the southern Yellow Sea.The area of subaerial tidal sandbody system is about 3 000 km\+2.Tidal sedimentary structures,such as muddy streak,flaser structure and bi-direction cross-bedding,show tidal genesis of the sandbody system.The tidal sand strata are underlain by littoral unit or terrigenous hard clay and overlain by tidal flat deposits.\;Magnetic fabrics are measured and analyzed at two representative drilling cores,Tongshang and Xinhai,which have penetrated tidal flat strata,tidal sand body and hard clay.Two drilling cores ard sampled successively.The samples are measured and magnetic fabric parameters K、P、F、L and q are calculated,then successive curves of these magnetic fabric parameters are acquired.These curves show that K、P、F、L and q of the tidal sand body demonstrate an apparent difference from those of underlain paleosol and overlain strata,and lower and upper boundaries of the tidal sand body can be defined by the curves.There are abrupt changes of K、P and F at the boundary between tidal sand strata and the underlying paleosol,with sharply increasing of these parameters in the tidal sand strate.Thus.it can be inferrd that environmental energy in the tidal sand strata is abruptly increased.Under the strong and stable tidal current,the deposition is coincided with hydrodynamics and most of q is less than 0.5 in the tidal sand strata.However the hard clay(paleosol) formed in low energy environment of floodplain contains a lot of sedimentary units with q higher than 0.7,which corresponds to a quick deposition The tidal sand body unit transits gradunally upward to tidal flat deposits,but the boundary between them is still cleraly discernable by the magnetic fabric curves.Smaller K and P reflect hydrodynamic decline from the tidal sand body unit to tidal flat deposts.\;Abrupt variation of K and P within the tidal sand strata may reflect superimposition of sand ridge and tidal current trough depositional units in vertical profile,which shows micro-hydrodynamic changes on the tidal ridge and in the trough.Horizontally,that values of P、K in core Xinhai are higher than those in core Tongshang shows variations of hydrodynamics matching the convergent-divergent tidal current field in the study area.Contents of heavy minerals also show the similar tendency of tidal current changes.Besides,variations of K and content of varied magnetic minerals among heavy mineral also indicate multi-provenance of the study area,with“the Yellow River source” prominent at north and “the Changjiang Rover source” at south.
1999, 17(4): 620-626.
Abstract:
The coal type gas resource of Mesozoic mainly concentrates on the North China where the Northwest area is the most favorable region, and the gas source rocks are almost Jurassic coal series.The Turpan Basin is a typical coal type gas basin where C1/C1-5 value of HongTai 2 gas pool is 0.887,and its δ13C1-4 values and 40Ar/ 36Ar ratio are -39.1‰,-26.5‰,-25.4‰,-25.2‰ and 571,respectively.And these indicate that the Middle Jurassic series are self generated and self reservoired coal type gas pools,and the reversion of tectonic environment is the special structural condition for source rock to generate and concentrate coalbed gases. The coal type gas resource of Cenozoic mainly concentrates on the rift valleys of continental shelf along the seawest of the East China,and the Upper Tertiary coal series and their chief source rocks,The Ya 13 1 gas field located in the South of HaiNan Province is also a typical one that its δ13C1,value varies from -39.9‰ to -35.5‰,δ13C2 value varies from -26.8‰ to -24‰,and its gas belongs to pyrolysis genesis.The high temperature tectonic environment (thermal gradient of the Earth exceeds 4℃/100 m)is the favorable factor for the Tertiary to generate hydrocarbon,however,anticline and fault trap is the most helpful structural condition of concentration and reservation.
The coal type gas resource of Mesozoic mainly concentrates on the North China where the Northwest area is the most favorable region, and the gas source rocks are almost Jurassic coal series.The Turpan Basin is a typical coal type gas basin where C1/C1-5 value of HongTai 2 gas pool is 0.887,and its δ13C1-4 values and 40Ar/ 36Ar ratio are -39.1‰,-26.5‰,-25.4‰,-25.2‰ and 571,respectively.And these indicate that the Middle Jurassic series are self generated and self reservoired coal type gas pools,and the reversion of tectonic environment is the special structural condition for source rock to generate and concentrate coalbed gases. The coal type gas resource of Cenozoic mainly concentrates on the rift valleys of continental shelf along the seawest of the East China,and the Upper Tertiary coal series and their chief source rocks,The Ya 13 1 gas field located in the South of HaiNan Province is also a typical one that its δ13C1,value varies from -39.9‰ to -35.5‰,δ13C2 value varies from -26.8‰ to -24‰,and its gas belongs to pyrolysis genesis.The high temperature tectonic environment (thermal gradient of the Earth exceeds 4℃/100 m)is the favorable factor for the Tertiary to generate hydrocarbon,however,anticline and fault trap is the most helpful structural condition of concentration and reservation.
1999, 17(4): 633-637.
Abstract:
The ty pical rhy thmic bedding limestone and marl of upper Jurassic M alm in southern Germany were d4posited in typical epicontinental platfo rm envirnment. The rocks in the sectio n were bed by bed sampled, their residues were obtained by isolation with monochlo acid (CH2ClOO H). The mineral assemblage in residues m ainaly consists of quartz, K-feldspar and clay minerals according to X-ray diffraction analy sis. The analy sis of residues bo th in mineral assemblage and in chemical composition show s that the non-carbo nate m a-terials in limestone and in marl are no essential difference. The geochemical analy sis with XRFS (X -ray Fluo-rescence Spectrometry) w as taken both on rocks and on the residues. SiO2, Al2O3, Fe2O3, K2O and TiO2 are related to detritus, and demonstrate the same relationships in limestone and in marl, moreover, they all have a g ood positive relationship to the residues content and are classified to the so-called detritus elements group. They rem ained in the sediments and had no change after deposition. Their different concentrations in lime-stonse and in marl are only due to the effect of carbonate sediments, dilution during deposition. The elements Sr, Zn, Mn, and Mg are controlled by diagenesis. They exist fi rstly in the carbonate form, but change much in the period of diagenesis. Dolomitization in some posme posi tion of the section leads to high Mg-content in the rocks. These elements are classified to the group of diagenesis elements. The elements in this g roup have no clear relationship to the residues-contents. However, the behavio r of elements such as S, Ba, Rb and P is be-tween the two groups of elements. They were controlled partly by the detritus and partly by the diagenesis, and they are somerelationship to the residues-contents. The fo rmation of rhy thmic bedding limes tone and marl is the result result of the variation of carbo nate sedimentation rat and then compressed w ith pressure solution. But the differences of them are only in residues content but not essentially in the mineral assemblage and geo-chemical composition of non-carbo nate material in the rocks.
The ty pical rhy thmic bedding limestone and marl of upper Jurassic M alm in southern Germany were d4posited in typical epicontinental platfo rm envirnment. The rocks in the sectio n were bed by bed sampled, their residues were obtained by isolation with monochlo acid (CH2ClOO H). The mineral assemblage in residues m ainaly consists of quartz, K-feldspar and clay minerals according to X-ray diffraction analy sis. The analy sis of residues bo th in mineral assemblage and in chemical composition show s that the non-carbo nate m a-terials in limestone and in marl are no essential difference. The geochemical analy sis with XRFS (X -ray Fluo-rescence Spectrometry) w as taken both on rocks and on the residues. SiO2, Al2O3, Fe2O3, K2O and TiO2 are related to detritus, and demonstrate the same relationships in limestone and in marl, moreover, they all have a g ood positive relationship to the residues content and are classified to the so-called detritus elements group. They rem ained in the sediments and had no change after deposition. Their different concentrations in lime-stonse and in marl are only due to the effect of carbonate sediments, dilution during deposition. The elements Sr, Zn, Mn, and Mg are controlled by diagenesis. They exist fi rstly in the carbonate form, but change much in the period of diagenesis. Dolomitization in some posme posi tion of the section leads to high Mg-content in the rocks. These elements are classified to the group of diagenesis elements. The elements in this g roup have no clear relationship to the residues-contents. However, the behavio r of elements such as S, Ba, Rb and P is be-tween the two groups of elements. They were controlled partly by the detritus and partly by the diagenesis, and they are somerelationship to the residues-contents. The fo rmation of rhy thmic bedding limes tone and marl is the result result of the variation of carbo nate sedimentation rat and then compressed w ith pressure solution. But the differences of them are only in residues content but not essentially in the mineral assemblage and geo-chemical composition of non-carbo nate material in the rocks.
1999, 17(4): 651-654.
Abstract:
TSP is one of the most important forms of air pollution,in which harmful organic matter can be absorbed and enter the human body resulting in different disease.In this paper,distribution characteristics of organic matter of TSP in Taiyuan city was originally researched.After analysed the samples collected in different function zones of Taiyuan city during heating and non heating seasons.the concentration and distribution of the organic matters in TSP including saturated hydrocarbon,aromatics,non hydrocarbons and asphaltenes are obtained,which shows that: 1)the concentration of organic matter during heating seasons is higher than that during non heating ones.2) the concentration of organic matter is various in different function zones,i.e.,industrial zonecommercial and living zonechemical industry and culture zone.3) the order of concentration of organic compositions is asphaltenesaromaticsnon hydrocarbonssaturated hydrocarbon.4)pollution in Taiyuan city is mainly attributed to burning of coal,gas and industrial release. Since the air pollution of Taiyuan city mainly results from coal burning,which is more serious in winter than in summer,so it is necessary to take efficient measures such as collective heating supply and efficient dust removing methods to control it.Among functional zones,the industrial area of the steel plant is the most seriously polluted region where heavy industrial plants such as the steel plant and the mine machinery factory releasing waste gases to pollute air should be controlled.In addition,little stoves or boiler must be restricted.As the highest content of asphaltene in four organic compositions,the high efficient coat washing equipment should be adopted to retrieve asphat and tar before its trasportation and burning.During transportation,coal should be tightly packed.More efforts should be made in constructing artificial woods to improve the air quality of Taiyuan city.
TSP is one of the most important forms of air pollution,in which harmful organic matter can be absorbed and enter the human body resulting in different disease.In this paper,distribution characteristics of organic matter of TSP in Taiyuan city was originally researched.After analysed the samples collected in different function zones of Taiyuan city during heating and non heating seasons.the concentration and distribution of the organic matters in TSP including saturated hydrocarbon,aromatics,non hydrocarbons and asphaltenes are obtained,which shows that: 1)the concentration of organic matter during heating seasons is higher than that during non heating ones.2) the concentration of organic matter is various in different function zones,i.e.,industrial zonecommercial and living zonechemical industry and culture zone.3) the order of concentration of organic compositions is asphaltenesaromaticsnon hydrocarbonssaturated hydrocarbon.4)pollution in Taiyuan city is mainly attributed to burning of coal,gas and industrial release. Since the air pollution of Taiyuan city mainly results from coal burning,which is more serious in winter than in summer,so it is necessary to take efficient measures such as collective heating supply and efficient dust removing methods to control it.Among functional zones,the industrial area of the steel plant is the most seriously polluted region where heavy industrial plants such as the steel plant and the mine machinery factory releasing waste gases to pollute air should be controlled.In addition,little stoves or boiler must be restricted.As the highest content of asphaltene in four organic compositions,the high efficient coat washing equipment should be adopted to retrieve asphat and tar before its trasportation and burning.During transportation,coal should be tightly packed.More efforts should be made in constructing artificial woods to improve the air quality of Taiyuan city.
1999, 17(4): 659-662.
Abstract:
Xixia basin is situated at the southeast margin of Henan province,China.It is one of the most important localities of the dinosaur eggs fossil in the world.It is famous for its abundant egg-bearing horizons,the vast quantity,the varied categories and the well preserved original states.The dinosaur eggs fossil included 19 species,assigned to 10 genera and belonged to 7 families. Up to now,several ten thousand dinosaur eggs fossils have been excavated,and most of them are in single.They are associated with Hadrosaurs,Tyrannosaurs,Sauropods,Charophytes,sporopollen and trace fossils, etc..Red clastic sediments mixed sand,gravel,mud and lime-mud occured within the late Cretaceous Xixia basin.A detailed study on this basin has made it possible to establish the normal stratigraphical sequence.The subdivision of red beds includes the Gaogou,Majiacun and Sigou Formations from bottom to top.The sequence is based on the type of dinosaur fossil eggs and their distribution,lithology,sedimentary facies,microfossils,formation and evolution of the basin,and absolute age dating,etc.. It is found that a little organism,asphalt,remaining in the dinosaur eggshell fossils,appears yellowish-brown or light dark under the microscope,and gives off asphalt foul smell and cracking sound on the eggshells when being burned,and gives off pungent smell on reacting with thick hydrochloric acid.Rock-Eval analysis reveals that S 1+S 2 varies from 0.44% to 2.77%,indicating that a little organism remains in the dinosaur eggshell fossils. The thirteen dinosaur eggshell fossils of the Late Cretaceous Period from Xixia Bsain and some surrounding rocks have been investigated by ICP-AES.In the elemental composition of the dinosaur eggshell fossils from Xixia Basin,the main element is Ca,next is Al,Mg,Fe,Na,K and Ti,and the microelement is mainly Sr,Mn,Ba,La,Zn etc.. By analyzing the thirteen dinosaur eggshell fossils,it is found that the content of strontium varies from 1 962 ×10-6 to 11 010×10-6,averaging 5 532×10-6,and is one to several times higher than that in the shells of ancient brachiopods or modern ones,being a quantity level higher than that of the earth's crust.Obviously,the dinosaur eggshell fossils show the clear strontium superhigh anomaly. The strontium is a kind of widely-distributed microelement.Its ionic radium is close to that of Caion and Kion.As a result,it easily displaces Ca2+ and K+ so as to enter the carbonate minerals.According to the result of research at present,the biomineral is deposited in the impure solution.Other ions in solution enter the main crystal,resulting in the crystal growth and change of the from and chemical property of the crystal.When the main crystal ion is replaced in isomorph by ion with the same size and similar electric charge,the main crystal composition is worse-distributed because of the different relative density of ions deposition in different period.At the same time, different ions prefer different main crystal lattices,for example,Mg2+ prefers the calcite lattice,Sr2+ prefers the aragonite lattice.Thus it can be seen that the aragonite is rich in Sr,the content of which is much higher than that of the other carbonate minerals.So we can infer that a quantity of aragonite once existed in the dinosaur eggshell fossils.Due to the little stability of the aragonite,it could be changed into calcite gradually during its evolution.So there is no aragonite in the eggshells at present, however,the strontium was remained.It is indicated that the eggshells of terrestrial reptile are similar to the shells of marine organisms,in which there are aragonite and calcite at the same time.
Xixia basin is situated at the southeast margin of Henan province,China.It is one of the most important localities of the dinosaur eggs fossil in the world.It is famous for its abundant egg-bearing horizons,the vast quantity,the varied categories and the well preserved original states.The dinosaur eggs fossil included 19 species,assigned to 10 genera and belonged to 7 families. Up to now,several ten thousand dinosaur eggs fossils have been excavated,and most of them are in single.They are associated with Hadrosaurs,Tyrannosaurs,Sauropods,Charophytes,sporopollen and trace fossils, etc..Red clastic sediments mixed sand,gravel,mud and lime-mud occured within the late Cretaceous Xixia basin.A detailed study on this basin has made it possible to establish the normal stratigraphical sequence.The subdivision of red beds includes the Gaogou,Majiacun and Sigou Formations from bottom to top.The sequence is based on the type of dinosaur fossil eggs and their distribution,lithology,sedimentary facies,microfossils,formation and evolution of the basin,and absolute age dating,etc.. It is found that a little organism,asphalt,remaining in the dinosaur eggshell fossils,appears yellowish-brown or light dark under the microscope,and gives off asphalt foul smell and cracking sound on the eggshells when being burned,and gives off pungent smell on reacting with thick hydrochloric acid.Rock-Eval analysis reveals that S 1+S 2 varies from 0.44% to 2.77%,indicating that a little organism remains in the dinosaur eggshell fossils. The thirteen dinosaur eggshell fossils of the Late Cretaceous Period from Xixia Bsain and some surrounding rocks have been investigated by ICP-AES.In the elemental composition of the dinosaur eggshell fossils from Xixia Basin,the main element is Ca,next is Al,Mg,Fe,Na,K and Ti,and the microelement is mainly Sr,Mn,Ba,La,Zn etc.. By analyzing the thirteen dinosaur eggshell fossils,it is found that the content of strontium varies from 1 962 ×10-6 to 11 010×10-6,averaging 5 532×10-6,and is one to several times higher than that in the shells of ancient brachiopods or modern ones,being a quantity level higher than that of the earth's crust.Obviously,the dinosaur eggshell fossils show the clear strontium superhigh anomaly. The strontium is a kind of widely-distributed microelement.Its ionic radium is close to that of Caion and Kion.As a result,it easily displaces Ca2+ and K+ so as to enter the carbonate minerals.According to the result of research at present,the biomineral is deposited in the impure solution.Other ions in solution enter the main crystal,resulting in the crystal growth and change of the from and chemical property of the crystal.When the main crystal ion is replaced in isomorph by ion with the same size and similar electric charge,the main crystal composition is worse-distributed because of the different relative density of ions deposition in different period.At the same time, different ions prefer different main crystal lattices,for example,Mg2+ prefers the calcite lattice,Sr2+ prefers the aragonite lattice.Thus it can be seen that the aragonite is rich in Sr,the content of which is much higher than that of the other carbonate minerals.So we can infer that a quantity of aragonite once existed in the dinosaur eggshell fossils.Due to the little stability of the aragonite,it could be changed into calcite gradually during its evolution.So there is no aragonite in the eggshells at present, however,the strontium was remained.It is indicated that the eggshells of terrestrial reptile are similar to the shells of marine organisms,in which there are aragonite and calcite at the same time.
1999, 17(4): 508-614.
Abstract:
The fluid inclusion aqueous solutions and gas composition is important material evidence for genesis of ore deposits,which is direct participant of mineralization and closely related to depostional mechanisms.The paper has studied the characters of fluid inclusion gas composition,gaseous hydrocarbon composition and carbon isotope of gas from 18 samples in Huayuan Mississippi Valley-type Lead-Zinc deposits which occured in algal limestone oolitic-limestone and muddy limestone of Lower Cambrian Qingxudong Formation.The characters are that: 1.There are a little organic inclusion in ores which has been comfirmed with fluorescence microscope that a few circular organic inclusion or organic remains give out bright yellow or green-blue fluorescence. 2.Most analyzed inclusions consist of H2O with CO2 (average 5.0mol%),gaseus hydrocarbon (average 1.1mol% ) and smaller amounts of CO and,H2,etc.The content of H2O is stable and the content of CO2and hydrocarbon is various in inclusion.Gas composition of inclusion is the same between sulfides and gangue minerals,but in sulfide with different characters. 3.Methane (CH4) is the main part in hydrocarbon composition of the most inclusionsbut the content is notgreater than 95% (average 84.89%),in inclusion of sphalirite at different host rocks,which is difference,the methane content in inclusion of spharilith at light gray limestone (averge 92.65%) is more than the spharilite at gray muddy limestone (average 84.89%). 4. δ13C of methane in inclusion of main mineralization stage ranges from -27.97‰ to -26.13‰,average -27.08‰ (PDB),δ13C of CO2 in inclusion of main mineralization stage can be distinctly divided into two parts,the chief one in the main mineralization stage ranges from -19.43‰ to -14.5‰,average -17.28‰(PDS),the second one at the same time and that in the late mineralization stage are rather large (-8.12‰～3.0‰,average -3.71‰), suggesing that the main origin of CO2 in inclusion is related to the thermal degradation of organic matter. Above-mentioned characters of inclusion gas composition suggest that the organic matter really occurred in the gas composition of inclusion,the gaseous hydrocarbon and CO2 is organic origin in fluid inclusion;the hydrocarbon possibly has some source bed,and the depositional mechanism is possibly related to mixture of aqueous solutions with a pre-existing old oil-gas accumulation at the sites of deposition.
The fluid inclusion aqueous solutions and gas composition is important material evidence for genesis of ore deposits,which is direct participant of mineralization and closely related to depostional mechanisms.The paper has studied the characters of fluid inclusion gas composition,gaseous hydrocarbon composition and carbon isotope of gas from 18 samples in Huayuan Mississippi Valley-type Lead-Zinc deposits which occured in algal limestone oolitic-limestone and muddy limestone of Lower Cambrian Qingxudong Formation.The characters are that: 1.There are a little organic inclusion in ores which has been comfirmed with fluorescence microscope that a few circular organic inclusion or organic remains give out bright yellow or green-blue fluorescence. 2.Most analyzed inclusions consist of H2O with CO2 (average 5.0mol%),gaseus hydrocarbon (average 1.1mol% ) and smaller amounts of CO and,H2,etc.The content of H2O is stable and the content of CO2and hydrocarbon is various in inclusion.Gas composition of inclusion is the same between sulfides and gangue minerals,but in sulfide with different characters. 3.Methane (CH4) is the main part in hydrocarbon composition of the most inclusionsbut the content is notgreater than 95% (average 84.89%),in inclusion of sphalirite at different host rocks,which is difference,the methane content in inclusion of spharilith at light gray limestone (averge 92.65%) is more than the spharilite at gray muddy limestone (average 84.89%). 4. δ13C of methane in inclusion of main mineralization stage ranges from -27.97‰ to -26.13‰,average -27.08‰ (PDB),δ13C of CO2 in inclusion of main mineralization stage can be distinctly divided into two parts,the chief one in the main mineralization stage ranges from -19.43‰ to -14.5‰,average -17.28‰(PDS),the second one at the same time and that in the late mineralization stage are rather large (-8.12‰～3.0‰,average -3.71‰), suggesing that the main origin of CO2 in inclusion is related to the thermal degradation of organic matter. Above-mentioned characters of inclusion gas composition suggest that the organic matter really occurred in the gas composition of inclusion,the gaseous hydrocarbon and CO2 is organic origin in fluid inclusion;the hydrocarbon possibly has some source bed,and the depositional mechanism is possibly related to mixture of aqueous solutions with a pre-existing old oil-gas accumulation at the sites of deposition.
1999, 17(4): 521-527.
Abstract:
The patterns of thime evolution and space distribtion of the Permian sequence stratigraphy in South China,which are recognized as in the paper by Wang et al.in this period of the journal,are well confined by the research on sequence fills of the eleven depositional sequences. It is proposed that two stages of depositional sequence fills can be classified,i.e.,(1)Fills by carbonate ramp and platform depositional sequences could have been undertaken during early Permian,into which sub fills could have been done by carbonate ramp and platform depositional sequences respectively.(2)Fills could have been completed by depositional sequences in dominant terrigenous clastics environments mixed by volcanic clastics during late Permian.It can be subclassified into two subdivisions as sediments with coal in wet climate in the Wujiaping Stage and as coarse clastics in extensional pull aparting faults during the Changxing Stage. It is supposed that the four type I sequence boundary surfaces in Permian could be directly relevant to the tectonic upwarding events.The basal boundary surface of the S 1 might have been controlled by the Yunnan Movement (or named of Guizhou Guangxi Movement) that had taken roles in the middle Yangtze Craton and on the western margin of the Cathayan Craton.The boundary surface of the S 6 might have been in fluenced by the first episode of the Dongwu Movement (also called Dachang Movement) which had acted similar areas as the S 1 The S 7 boundary surface had ever widespread related to the Dongwu Movement all over the South China during the gap between the Early and Upper Permian.And the boundary surface on the S 1 base might have been under impacts by the Guiyang Movement almost the yangtze Craton. One of the most characteristically depositional sequence fills is volcanic clastics in some horizons in the TST of late Permian,during which a few horizons of the transgressive systems tracts (TST) had ever been filled by volcanic clastics.There is a typical sequence pattern of sedimentary facies in the TST with volcanic clastics.It is common that the sequence from calsiclastic turbidite facies to volcanic turbidite facies,to marlstone facies in the TST.The other is the delta system along the margins of paleolands.Most of the delta systems constitute the high systems tracts (HST),and/or few shelf marginal systems tracts (SMT) or lowest systems tracts (LST). Reefal fills can be found in the upper and middle Yangtze Cratons and Youjiang Basin,and four types of reefal fills can be differentiated in the depositional sequence fills.They are TST type,HST type,LST type,and SMT type,in which TST type and HST type are predominant along the synsedimentologicall strike slip faults.Reefs in high abundance and diversity filled in the TSTs had been lived in deep water,mostly in slope,deep ramp,and/or inter platform.Reefs in the HSTs are of low abundance and diversity of species and community,and they had been lived in shallow sea such as carbonate platform,shore,shelf and isolated platform
The patterns of thime evolution and space distribtion of the Permian sequence stratigraphy in South China,which are recognized as in the paper by Wang et al.in this period of the journal,are well confined by the research on sequence fills of the eleven depositional sequences. It is proposed that two stages of depositional sequence fills can be classified,i.e.,(1)Fills by carbonate ramp and platform depositional sequences could have been undertaken during early Permian,into which sub fills could have been done by carbonate ramp and platform depositional sequences respectively.(2)Fills could have been completed by depositional sequences in dominant terrigenous clastics environments mixed by volcanic clastics during late Permian.It can be subclassified into two subdivisions as sediments with coal in wet climate in the Wujiaping Stage and as coarse clastics in extensional pull aparting faults during the Changxing Stage. It is supposed that the four type I sequence boundary surfaces in Permian could be directly relevant to the tectonic upwarding events.The basal boundary surface of the S 1 might have been controlled by the Yunnan Movement (or named of Guizhou Guangxi Movement) that had taken roles in the middle Yangtze Craton and on the western margin of the Cathayan Craton.The boundary surface of the S 6 might have been in fluenced by the first episode of the Dongwu Movement (also called Dachang Movement) which had acted similar areas as the S 1 The S 7 boundary surface had ever widespread related to the Dongwu Movement all over the South China during the gap between the Early and Upper Permian.And the boundary surface on the S 1 base might have been under impacts by the Guiyang Movement almost the yangtze Craton. One of the most characteristically depositional sequence fills is volcanic clastics in some horizons in the TST of late Permian,during which a few horizons of the transgressive systems tracts (TST) had ever been filled by volcanic clastics.There is a typical sequence pattern of sedimentary facies in the TST with volcanic clastics.It is common that the sequence from calsiclastic turbidite facies to volcanic turbidite facies,to marlstone facies in the TST.The other is the delta system along the margins of paleolands.Most of the delta systems constitute the high systems tracts (HST),and/or few shelf marginal systems tracts (SMT) or lowest systems tracts (LST). Reefal fills can be found in the upper and middle Yangtze Cratons and Youjiang Basin,and four types of reefal fills can be differentiated in the depositional sequence fills.They are TST type,HST type,LST type,and SMT type,in which TST type and HST type are predominant along the synsedimentologicall strike slip faults.Reefs in high abundance and diversity filled in the TSTs had been lived in deep water,mostly in slope,deep ramp,and/or inter platform.Reefs in the HSTs are of low abundance and diversity of species and community,and they had been lived in shallow sea such as carbonate platform,shore,shelf and isolated platform
1999, 17(4): 536-541.
Abstract:
On the basis of sequence stratigraphy,fills and evolution of sedimentary basin,a primary research on the Permian sea level and eustatic changes,rise and fall events in South China have been studied in this paper. Eleven cycles of relative sea level rising falling,which is equal to the depositional sequences,are recognized in Permian in South China.Of them,two patterns of the relative sea level rising falling are distinguished out.The first is a change tendency of continuously slower rising→faster falling that is dominated in the Yangtze Craton,and the second is vice versa that is common in most parts of Cathayan Craton,especially in eastern shallow Cathayan Craton.The two patterns of relative sea level rising falling are just in symmetric tendency. Also the changing patterns of the second order eustasy are divided into “One and half" type and “Single" type through the Permian which are the representatives of Yangtze Craton and Cathayan Craton respectively.Here,the “One and half"type means that there are on complete second order cycle and less than half cycle in Permian in Yangtze Craton and western margin of the Cathayan Craton.And the “Single"type shows that there is just one complete rising falling cycle in the same period in the eastern shallow Cathayan Craton. There are five events of sea level rising and falling,i.e.,the rising event in early Qixia stage,the highest sea level stand event at the earliest Maokou stage,the lowest sea level stand event at the terminal Maokou stage,the rising event in primary Wujiaping stage,and the falling event at middle Changxing stage separately.It is proposed that most of the sea level rising and falling events are relevant to the regional tectonics superposed by the second eustasy. The patterns of sea level and eustatic changes are distinctly different from those in Euramerica.The time of the highest eustatic stand is aged as the earliest Maolou Stage,which approximately equals to the early Artinskian in Europe,to the early Leonardian in North America.But it is showed in the late Maolou Stage on the Vail Curve in 1977,and in the terminal Carboniferous in the Gondwana Land in the T R cycles by Ross and Ross in 1985.The lowest eustatic stand in the Yangtze Craton lies in the terminal Early Permian (latest Maokou Stage),but displays in earliest Permian on the Vil Curve (1977),and in latest Permian in the T R cycles by Ross and Ross in 1985.The total tendency of eustatic change in the Cathayan Craton is similar to that on the Vail Curve although the highest eustatic stand of the former formed earlier than the later.It is supposed that the controls are probably different in variable tectonic settings becaus the Yangtze Craton and western Cathayan Craton belong to the Tethyan tectonic field,and the eastern Cathayan Craton,Euramerica to the Pacific tectonic field.
On the basis of sequence stratigraphy,fills and evolution of sedimentary basin,a primary research on the Permian sea level and eustatic changes,rise and fall events in South China have been studied in this paper. Eleven cycles of relative sea level rising falling,which is equal to the depositional sequences,are recognized in Permian in South China.Of them,two patterns of the relative sea level rising falling are distinguished out.The first is a change tendency of continuously slower rising→faster falling that is dominated in the Yangtze Craton,and the second is vice versa that is common in most parts of Cathayan Craton,especially in eastern shallow Cathayan Craton.The two patterns of relative sea level rising falling are just in symmetric tendency. Also the changing patterns of the second order eustasy are divided into “One and half" type and “Single" type through the Permian which are the representatives of Yangtze Craton and Cathayan Craton respectively.Here,the “One and half"type means that there are on complete second order cycle and less than half cycle in Permian in Yangtze Craton and western margin of the Cathayan Craton.And the “Single"type shows that there is just one complete rising falling cycle in the same period in the eastern shallow Cathayan Craton. There are five events of sea level rising and falling,i.e.,the rising event in early Qixia stage,the highest sea level stand event at the earliest Maokou stage,the lowest sea level stand event at the terminal Maokou stage,the rising event in primary Wujiaping stage,and the falling event at middle Changxing stage separately.It is proposed that most of the sea level rising and falling events are relevant to the regional tectonics superposed by the second eustasy. The patterns of sea level and eustatic changes are distinctly different from those in Euramerica.The time of the highest eustatic stand is aged as the earliest Maolou Stage,which approximately equals to the early Artinskian in Europe,to the early Leonardian in North America.But it is showed in the late Maolou Stage on the Vail Curve in 1977,and in the terminal Carboniferous in the Gondwana Land in the T R cycles by Ross and Ross in 1985.The lowest eustatic stand in the Yangtze Craton lies in the terminal Early Permian (latest Maokou Stage),but displays in earliest Permian on the Vil Curve (1977),and in latest Permian in the T R cycles by Ross and Ross in 1985.The total tendency of eustatic change in the Cathayan Craton is similar to that on the Vail Curve although the highest eustatic stand of the former formed earlier than the later.It is supposed that the controls are probably different in variable tectonic settings becaus the Yangtze Craton and western Cathayan Craton belong to the Tethyan tectonic field,and the eastern Cathayan Craton,Euramerica to the Pacific tectonic field.
1999, 17(4): 547-552.
Abstract:
The excellent outcrops developped in Guiyang and Zhengfeng area,Guizhou Province in early and middle Triassic.In the context of the tectonic setting,Guiyang and Zhengfen area,Guizhou province,is situated at the northwestern basinal margin of the Nanpanjiang basin in early and middle Triassic.The sedimentary characteristic of the deep water carbonate developed in this area was made up of in situ and allochthonous carbonates.Furthermore,the allochthonous carbonates were divided into four types,i.e.,debris flow,density modified grain flow,turbidity and sedimentary slumping. The in situ carbonate was characteristic of gray dark gray thin bedded micritic limestone with the sparse faecal pellets and bioturbated structures,indicating the background deposits of the deep water carbonates. The debris flow deposit was a primary type among the allochthonous carbonates,and composed of the floating brecciola and brecciola. The turbidity flow deposit primarily possessed the Bouma sequence T bc and T ab,and sparsely the whole sequence of T abced which occurred in the middle Triassic. The sedimentary slumping formed the slumpong rock.It possessed not only the partial features of the brecciola,but also retained the primitive character with little matrix.It primarily occurred in upper part of the Qinai Formation (middle Triassic) as the thin bedded micritic limestone. And the deep water carbonate slopes developped into the three kinds of models including homocline ramp,sedimentary slope and by pass slope.In the context of the eustatic sea level rise in early middle Triassic epoch,the evolution of the carbonate slope was mainly controlled by the tectonic activity.With the passive margin,development of Nanpanjiang basin in early Triassic,the carbonate slope evolved from the ramp into the prograding sedimentary slope.And in the middle Triassic,accompanying with the development of the peripheral foreland basin,the evolution of the carbonate slope was affected with the flexural extension in the basin.As a result,the carbonate slope developed into the by pass slope with the evolution from the stepping to successive retreat.
The excellent outcrops developped in Guiyang and Zhengfeng area,Guizhou Province in early and middle Triassic.In the context of the tectonic setting,Guiyang and Zhengfen area,Guizhou province,is situated at the northwestern basinal margin of the Nanpanjiang basin in early and middle Triassic.The sedimentary characteristic of the deep water carbonate developed in this area was made up of in situ and allochthonous carbonates.Furthermore,the allochthonous carbonates were divided into four types,i.e.,debris flow,density modified grain flow,turbidity and sedimentary slumping. The in situ carbonate was characteristic of gray dark gray thin bedded micritic limestone with the sparse faecal pellets and bioturbated structures,indicating the background deposits of the deep water carbonates. The debris flow deposit was a primary type among the allochthonous carbonates,and composed of the floating brecciola and brecciola. The turbidity flow deposit primarily possessed the Bouma sequence T bc and T ab,and sparsely the whole sequence of T abced which occurred in the middle Triassic. The sedimentary slumping formed the slumpong rock.It possessed not only the partial features of the brecciola,but also retained the primitive character with little matrix.It primarily occurred in upper part of the Qinai Formation (middle Triassic) as the thin bedded micritic limestone. And the deep water carbonate slopes developped into the three kinds of models including homocline ramp,sedimentary slope and by pass slope.In the context of the eustatic sea level rise in early middle Triassic epoch,the evolution of the carbonate slope was mainly controlled by the tectonic activity.With the passive margin,development of Nanpanjiang basin in early Triassic,the carbonate slope evolved from the ramp into the prograding sedimentary slope.And in the middle Triassic,accompanying with the development of the peripheral foreland basin,the evolution of the carbonate slope was affected with the flexural extension in the basin.As a result,the carbonate slope developed into the by pass slope with the evolution from the stepping to successive retreat.
1999, 17(4): 560-565.
Abstract:
As a result of tectonic activites,sea level changes and sediment supply rate etc., West Tarim has formed many depositional hiatuses with different forms and orders during its Paleozoic geological evolution,and its product uncomformites becomes the key element to establish the sequence stratigraphic framework in the study area.It is believed that the Paleozoic has undergone such a depositional cycles as transgrssion( O)→retrogression(S D)→transgression(C)→retrogression(P),which formed a variety of sequences with different features. The research shows that I order unconformities (sequence boundary) involve the Presinian top boundary, Ordovician top boundary and Paleozoic top bundary. According to the data of section,well and seism,as well as the characterisics and orders of different boundaries or uncomformities, two Ⅰ order sequences,six Ⅱ order sequences and twelve Ⅲ order sequences have been recognizaed for the first time.Ⅰ order sequence is formed under different tectonic settings and depositonal conditions,and Ⅱ order sequence are generally composed of four kinds of basic superimposing forms,i.e.,regression,progradation,aggradation and onlap.Ⅲ order sequence consists usually of system tracts limited by sequence boundary,transgression surface and MFS,in which TST and HST are frequently present, SMST and LST occasionally observed.In the study area,the transgressire system tracts(TST)are formed as the sea water become deeper step by step.As the sediments deposit towards the basin and,at the same time,the coast line retreats gradually,it is a sedimentary background that the highstand system tracts(HST)are formed.Different system tracts and sedimentary facies have controlled the distribution of source,reservoire and cap rocks.TST has a close relationship to the formation of source rock and reservoir and HST is generally related to the cap rock as well as reservoirs.
As a result of tectonic activites,sea level changes and sediment supply rate etc., West Tarim has formed many depositional hiatuses with different forms and orders during its Paleozoic geological evolution,and its product uncomformites becomes the key element to establish the sequence stratigraphic framework in the study area.It is believed that the Paleozoic has undergone such a depositional cycles as transgrssion( O)→retrogression(S D)→transgression(C)→retrogression(P),which formed a variety of sequences with different features. The research shows that I order unconformities (sequence boundary) involve the Presinian top boundary, Ordovician top boundary and Paleozoic top bundary. According to the data of section,well and seism,as well as the characterisics and orders of different boundaries or uncomformities, two Ⅰ order sequences,six Ⅱ order sequences and twelve Ⅲ order sequences have been recognizaed for the first time.Ⅰ order sequence is formed under different tectonic settings and depositonal conditions,and Ⅱ order sequence are generally composed of four kinds of basic superimposing forms,i.e.,regression,progradation,aggradation and onlap.Ⅲ order sequence consists usually of system tracts limited by sequence boundary,transgression surface and MFS,in which TST and HST are frequently present, SMST and LST occasionally observed.In the study area,the transgressire system tracts(TST)are formed as the sea water become deeper step by step.As the sediments deposit towards the basin and,at the same time,the coast line retreats gradually,it is a sedimentary background that the highstand system tracts(HST)are formed.Different system tracts and sedimentary facies have controlled the distribution of source,reservoire and cap rocks.TST has a close relationship to the formation of source rock and reservoir and HST is generally related to the cap rock as well as reservoirs.
1999, 17(4): 572-577.
Abstract:
Characterized by large area, shallow water, gentle slope, wide wave influencing belt, and weak energy, the SongLiao basin deposited a distinct large river delta in its northern depositional system. The delta is different from other marine delta in vertical sequence, types of framework sandbody and scale etc.. Instead, it presents more characteristics of shallow water delta. The delta is highly constructive fluvial dominated, characterized by directional ribbon like sandbody in front facies, and fluvial deposition can influences more than 20～30 kilometers under shoreline. Vertically, its sequence is discontinuous without three structure of typical delta. The thickness of sandbody is thin, with that of subaqueous channel 2～5m, and that of sheet sand less than 2m. In general, facies belts are well developed in which front facies usually covers more than 30～40 kilometers, and the inner front including the microfacies of subaqueous and sheet sand,and the outer front facies including only the sheet sand can be subdivided. Various kinds of sandbody association are formed because of frequently transgression and regression. The above characteristics have resulted in corresponding sandbody types in various stratigraphy section and subfacies area. Distinct framework models are formed while each kind of sandbody associate with mud in 3D space, these provides a sound genetic basis for establishing framework model. Based on the quantitative parameters such as density of sandbody, density of barrier, and coefficient of net sand,combining with the genetic features of sandbody associations and facies location, 5 types of framework models such as isolated channel pattern, stacked channel pattern, stable inter bedded pattern, unstable inter bedded pattern and isolated thin layer pattern are put forward. The sandbody in isolated channel pattern is very narrow, and shows puzzled shape in 3D space, so it is easy to form small ribbon like or lump like oil bearing area resulting from incompletely water driver under the condition of large well distance. Characterized by well developped subaqueous channel and main sheet sand, large sandbody density, good reservoir quality and connectivity between sandbodies, most of recovery oil in stacked channel pattern has been produced. The main features of unstable inter bedded pattern are its narrow subaqueous channel width and incised sheet sand, which result in good communication in later and poor connectivity in vertical. Remaining oil only exists in small area caused by local poor reservoir quality. For the stable inter bedded pattern, sandbody covers large horizontal area, sand layer and mud layer alternate in vertical. The sandbody possesses good connectivity in later and poor connectivity in vertical, some relative large area remaining oil exists resulting from poor reservoir quality. The sandbody of isolated thin layer pattern distribute on outer front facies of various types of delta, because of its very small sandbody density, the connectivity between sandbodies is very poor in 3D space, remaining oil can be produced only by density well pattern.
Characterized by large area, shallow water, gentle slope, wide wave influencing belt, and weak energy, the SongLiao basin deposited a distinct large river delta in its northern depositional system. The delta is different from other marine delta in vertical sequence, types of framework sandbody and scale etc.. Instead, it presents more characteristics of shallow water delta. The delta is highly constructive fluvial dominated, characterized by directional ribbon like sandbody in front facies, and fluvial deposition can influences more than 20～30 kilometers under shoreline. Vertically, its sequence is discontinuous without three structure of typical delta. The thickness of sandbody is thin, with that of subaqueous channel 2～5m, and that of sheet sand less than 2m. In general, facies belts are well developed in which front facies usually covers more than 30～40 kilometers, and the inner front including the microfacies of subaqueous and sheet sand,and the outer front facies including only the sheet sand can be subdivided. Various kinds of sandbody association are formed because of frequently transgression and regression. The above characteristics have resulted in corresponding sandbody types in various stratigraphy section and subfacies area. Distinct framework models are formed while each kind of sandbody associate with mud in 3D space, these provides a sound genetic basis for establishing framework model. Based on the quantitative parameters such as density of sandbody, density of barrier, and coefficient of net sand,combining with the genetic features of sandbody associations and facies location, 5 types of framework models such as isolated channel pattern, stacked channel pattern, stable inter bedded pattern, unstable inter bedded pattern and isolated thin layer pattern are put forward. The sandbody in isolated channel pattern is very narrow, and shows puzzled shape in 3D space, so it is easy to form small ribbon like or lump like oil bearing area resulting from incompletely water driver under the condition of large well distance. Characterized by well developped subaqueous channel and main sheet sand, large sandbody density, good reservoir quality and connectivity between sandbodies, most of recovery oil in stacked channel pattern has been produced. The main features of unstable inter bedded pattern are its narrow subaqueous channel width and incised sheet sand, which result in good communication in later and poor connectivity in vertical. Remaining oil only exists in small area caused by local poor reservoir quality. For the stable inter bedded pattern, sandbody covers large horizontal area, sand layer and mud layer alternate in vertical. The sandbody possesses good connectivity in later and poor connectivity in vertical, some relative large area remaining oil exists resulting from poor reservoir quality. The sandbody of isolated thin layer pattern distribute on outer front facies of various types of delta, because of its very small sandbody density, the connectivity between sandbodies is very poor in 3D space, remaining oil can be produced only by density well pattern.
1999, 17(4): 584-590.
Abstract:
The diagenetic environment of clastic reservoirs of different period in the southwest depression of Tarim basin have undergone a change from acidic to alkalic one. Such a change of geochemistry nature of diagenetic environments has directly controlled the characteristics of fluid-rock interaction in clastic system.The acidic environment formed during the most active period of organic-inorganic reaction in source-reservior rock system, which mainly distributed in A and B period of early diagenetic stage and A period of late diagenetic stage with geotemperature less than 90℃ and R o value ranging from 0.5% to 1.3%, and acidic pore fluid could dissolve and alter the framework grains and precipitate SiO2. When the geotemperature reached over 90℃ and R o ranging from 1.3% to 2%,organic acid began to decompose, and dehydroxyl-base ceased, the source of CO2 decreased and resulted in the nature of pore fluid changing from acidic to alkalic to form the alkalic environment. During this period, the late Fe-bearing carbonate replacement was the most active reaction, simultaneously resulting in the precipitation of authigenic illite and chlorite, recrystallisation of terrigenous illite and kaolinite changing to illite and chlorite,etc.. During the evolution of diagenetic environment, the change of pore fluid destroyed the physicochemistry equilibrium of diagenetic environment leading to the end of the old diagenetic reactions and beginning of new diagenetic reactions and forming lots of alteration-replacement-dissolution-precipitation processes which could produce the differences of reservoir rock texture and pore assemblage features.
The diagenetic environment of clastic reservoirs of different period in the southwest depression of Tarim basin have undergone a change from acidic to alkalic one. Such a change of geochemistry nature of diagenetic environments has directly controlled the characteristics of fluid-rock interaction in clastic system.The acidic environment formed during the most active period of organic-inorganic reaction in source-reservior rock system, which mainly distributed in A and B period of early diagenetic stage and A period of late diagenetic stage with geotemperature less than 90℃ and R o value ranging from 0.5% to 1.3%, and acidic pore fluid could dissolve and alter the framework grains and precipitate SiO2. When the geotemperature reached over 90℃ and R o ranging from 1.3% to 2%,organic acid began to decompose, and dehydroxyl-base ceased, the source of CO2 decreased and resulted in the nature of pore fluid changing from acidic to alkalic to form the alkalic environment. During this period, the late Fe-bearing carbonate replacement was the most active reaction, simultaneously resulting in the precipitation of authigenic illite and chlorite, recrystallisation of terrigenous illite and kaolinite changing to illite and chlorite,etc.. During the evolution of diagenetic environment, the change of pore fluid destroyed the physicochemistry equilibrium of diagenetic environment leading to the end of the old diagenetic reactions and beginning of new diagenetic reactions and forming lots of alteration-replacement-dissolution-precipitation processes which could produce the differences of reservoir rock texture and pore assemblage features.
1999, 17(4): 596-600.
Abstract:
Based on the studies of geology and geochemistry,the Qinling orogenic belt is characterized by three plates subduction and collision along the Shangdan suture zone and MianLue suture zone during major orogenic period.The Danfeng arc volcanic rocks and the Erlangping ophiolite indicate the existence of trench-arc-basin system along the North China plate.The Erlangping Group is composed of the northern Sishuyuan clastic sedimentary assemblages.intermediate ophiolite and the southern Xiaozhai clastic sedimentary assemblages,and represents the relicts of the Erlangping back-arc basin which was an important part of the active continental margin of the North China Plate in the Palaeozoic. The Xiaozhai metamorphic sedimentary assemblages consist of two different rock associations,including mica-schist,mica-quartz-schist and mica-schist,issite rocks.Based on the analysis of protolithes and geochemistry of the Xiaozhai metamorphic assemblages,the most of the two rock associations are sandstones and mud stones except part of the issite rocks.Research on the texture of sandstones show that the clast is mainly made up of feldspar, lithic fragment and little quartz,and the matrix content in sandstones is high,Both the compositional maturity and the textural maturity in the sandstones are low,so the rock types belong to detritic sandstone and feldspathic graywacke.The Xiaozhai sedimentary assemblages exist a series of sedimentary structures such as cross-beddings,horizontal beddings,evenly beddings and graded beddings,these different structures and rock types consist of Bouma sequence and can be clearly observed in weak deformation regimes.The study of sedimentary setting indicates that the Xiaozhai sedimentary assemblages set their position in sea-trench or trench-slope,which is related to the subduction of the Erlangping back-arc basin.The paleowater direction and sediment analysis verified that the Xiaozhai sedinentary assemblages clastics derived from the southern Qinling island arc. The structural deformation analysis have revealed that the Xiaozhai sedimentary assemblages had undergone four different deformation stages.These stages represented the tectonic evolution of the Erlangping back-arc basin.Firstly,fold deformation at deep-middle tectonic level,resulted in isoclined foldings,taking the primary bedding as deformation stratification and axial-plane clevages is rigional penetrative schistosity. Secondly,thrust ductile deformation formed in the deep-middle tectonic level.and show the deformation characteristic of major subduction stage.Finally,brittle shearing and strike-slip shearing dominated the sedimentary assemblages in the intracontinental stage.The subductional granites,tectonic melange and high pressure metamorphic zone in the south of the Xiaozai sedimentany assemblages which were formed in Hercynian-Indosinian epoch indicate that the Erlangping bock-arc basin subducted beneath the Qinling island arc during the major orogenic period. In the light of the comprehesive study of the Xiaozai sedimentary setting,metamorphism,deformation and magmatism,the evolution processes of Erlangping back-arc basin can be recognized as three stages,i.e., spreading stage(Pt 2-O 2),subduction-collision stage(O 2-T 2) and intracontinental stage (T 3-Q).
Based on the studies of geology and geochemistry,the Qinling orogenic belt is characterized by three plates subduction and collision along the Shangdan suture zone and MianLue suture zone during major orogenic period.The Danfeng arc volcanic rocks and the Erlangping ophiolite indicate the existence of trench-arc-basin system along the North China plate.The Erlangping Group is composed of the northern Sishuyuan clastic sedimentary assemblages.intermediate ophiolite and the southern Xiaozhai clastic sedimentary assemblages,and represents the relicts of the Erlangping back-arc basin which was an important part of the active continental margin of the North China Plate in the Palaeozoic. The Xiaozhai metamorphic sedimentary assemblages consist of two different rock associations,including mica-schist,mica-quartz-schist and mica-schist,issite rocks.Based on the analysis of protolithes and geochemistry of the Xiaozhai metamorphic assemblages,the most of the two rock associations are sandstones and mud stones except part of the issite rocks.Research on the texture of sandstones show that the clast is mainly made up of feldspar, lithic fragment and little quartz,and the matrix content in sandstones is high,Both the compositional maturity and the textural maturity in the sandstones are low,so the rock types belong to detritic sandstone and feldspathic graywacke.The Xiaozhai sedimentary assemblages exist a series of sedimentary structures such as cross-beddings,horizontal beddings,evenly beddings and graded beddings,these different structures and rock types consist of Bouma sequence and can be clearly observed in weak deformation regimes.The study of sedimentary setting indicates that the Xiaozhai sedimentary assemblages set their position in sea-trench or trench-slope,which is related to the subduction of the Erlangping back-arc basin.The paleowater direction and sediment analysis verified that the Xiaozhai sedinentary assemblages clastics derived from the southern Qinling island arc. The structural deformation analysis have revealed that the Xiaozhai sedimentary assemblages had undergone four different deformation stages.These stages represented the tectonic evolution of the Erlangping back-arc basin.Firstly,fold deformation at deep-middle tectonic level,resulted in isoclined foldings,taking the primary bedding as deformation stratification and axial-plane clevages is rigional penetrative schistosity. Secondly,thrust ductile deformation formed in the deep-middle tectonic level.and show the deformation characteristic of major subduction stage.Finally,brittle shearing and strike-slip shearing dominated the sedimentary assemblages in the intracontinental stage.The subductional granites,tectonic melange and high pressure metamorphic zone in the south of the Xiaozai sedimentany assemblages which were formed in Hercynian-Indosinian epoch indicate that the Erlangping bock-arc basin subducted beneath the Qinling island arc during the major orogenic period. In the light of the comprehesive study of the Xiaozai sedimentary setting,metamorphism,deformation and magmatism,the evolution processes of Erlangping back-arc basin can be recognized as three stages,i.e., spreading stage(Pt 2-O 2),subduction-collision stage(O 2-T 2) and intracontinental stage (T 3-Q).
1999, 17(4): 615-619.
Abstract:
The deep sequence of Xujiaweizi includes the first number and second number of Quntou Formation,Denglouku Formation,and Jurassic.The deep sequence has its own particular source rock and reservoir,and the gas in it has the special character different from the oil type gas from shallow horizon.We investigated the carbon isotope of methane,and the value of which ranges from-15‰ to -34‰,indicating that the deep gas is relative to deep mudstone.According to addtional data,the author believes that the deep gas is formed by coal.We also investigated the age of the deep gas,which is similar to deep source rocks,but is different from source rock of shallow sequence.The source rock of deep sequence has the value of Pr/Ph above 1.This is the character of coal system.And it is formed in late diagenesis with the Ro ranging from 1.25% to 2.25%,the organic matter is cracked under the temperature above 500℃ during the stage of wet gas and dry gas. The source rocks are controlled by sedimentary facies.The deep scquence has the following sedimentary facies:the fluvial fan,river channel,delta system and lake system,but the source rocks(mudstone)mainly belong to lake system.During the stage of Hushiling,the mudstone only developed in Yingshan subsidence.During the Shahezi stage,the lake system extended to Xingshan sag and Miaotaizi.During the period of Yingchen Formation,sediments extended further,the lake facies produced in the centre of the subsidence. The reservoir rocks and cover rocks are also controlled by sedimentary facies.The reservoir rocks developed in Denglouku Formation,Quantou Formation and Jurassic.The gas reservoirs are formed in sandstones,erosion crust and fracture zone of volcanic rocks.The reservoir is mainly controlled by the sedimentary facies and volcanic fracture zone.The sandstone of Denglouku Formation,Quantou Formation and Jurassic can be good reservoir of gas,and the conglomerate of Jurassic and the volcanic zone can also be good reservoir.The reservoir developed in the region where both the tectonic unit and the sedimentary facies are suitable for gas preservation.The porosity of deep sequence is not good,but some revervoirs have the good condition.For example,in Denglouku Formation,the porosity increases with the depth,sandstone percentage also increased.The grains became coarser.In the third number of Dengluolu Fm.good reservoir developed there. As for the cover rocks,there are three series of cover rocks developed there.The mudstone and siltstone developed there,with the porosity of 1% and permeability of 0.05×10 -3 μm 2.In the Xujiaweizi subsidence,the cover rocks developed in Quantou Formation,the second number of Denglouku Formation and the Jurassic. We also dealt with the trap type of reservoir and the prospects of gas exploration in this region. There are seven types of trap in deep sequence according to the shape of trap,the ratio of length to width, the style of tectonic and fracture aswellas combination type.These trap types included anticline,fracture nose like rise,fracture step,fracture platform and fracture block. The favorable regions include the Zaozhou-Anda anticline belt,Zaodong-Chaoyanggou anticline belt,Chang wu-Zao dong nose-like structure,we expect to find a big gas trap there. The Anda-Zaozhou anticline belt developed in the northern part of central rise.It is 114km long along the North-south direction,and 21-41 km along the west-east direction with an area of 3 040km 2,there four boreholes which produce gas,these drilling wells includes the Fangsheng-1,Fangsheng-2,Fangsheng-4 and Zao sheng-1,The gas is found in the Denglouku Formation,base erosion crust.Cover rocks are the first and second number of Quantou Formation,and the mudsone of Denglouku Formation. Zaodong-Chaoyanggou anticline belt located in the middle part of the Xujiaweizi subsidence,extending there north-east,with an area of 2 590km 2.There are seven boreholes,only one of them produce gas.This anticline belt locates between Xujiaweizi subsidence and Yingshan subsidence.There are sandy conglomera.
The deep sequence of Xujiaweizi includes the first number and second number of Quntou Formation,Denglouku Formation,and Jurassic.The deep sequence has its own particular source rock and reservoir,and the gas in it has the special character different from the oil type gas from shallow horizon.We investigated the carbon isotope of methane,and the value of which ranges from-15‰ to -34‰,indicating that the deep gas is relative to deep mudstone.According to addtional data,the author believes that the deep gas is formed by coal.We also investigated the age of the deep gas,which is similar to deep source rocks,but is different from source rock of shallow sequence.The source rock of deep sequence has the value of Pr/Ph above 1.This is the character of coal system.And it is formed in late diagenesis with the Ro ranging from 1.25% to 2.25%,the organic matter is cracked under the temperature above 500℃ during the stage of wet gas and dry gas. The source rocks are controlled by sedimentary facies.The deep scquence has the following sedimentary facies:the fluvial fan,river channel,delta system and lake system,but the source rocks(mudstone)mainly belong to lake system.During the stage of Hushiling,the mudstone only developed in Yingshan subsidence.During the Shahezi stage,the lake system extended to Xingshan sag and Miaotaizi.During the period of Yingchen Formation,sediments extended further,the lake facies produced in the centre of the subsidence. The reservoir rocks and cover rocks are also controlled by sedimentary facies.The reservoir rocks developed in Denglouku Formation,Quantou Formation and Jurassic.The gas reservoirs are formed in sandstones,erosion crust and fracture zone of volcanic rocks.The reservoir is mainly controlled by the sedimentary facies and volcanic fracture zone.The sandstone of Denglouku Formation,Quantou Formation and Jurassic can be good reservoir of gas,and the conglomerate of Jurassic and the volcanic zone can also be good reservoir.The reservoir developed in the region where both the tectonic unit and the sedimentary facies are suitable for gas preservation.The porosity of deep sequence is not good,but some revervoirs have the good condition.For example,in Denglouku Formation,the porosity increases with the depth,sandstone percentage also increased.The grains became coarser.In the third number of Dengluolu Fm.good reservoir developed there. As for the cover rocks,there are three series of cover rocks developed there.The mudstone and siltstone developed there,with the porosity of 1% and permeability of 0.05×10 -3 μm 2.In the Xujiaweizi subsidence,the cover rocks developed in Quantou Formation,the second number of Denglouku Formation and the Jurassic. We also dealt with the trap type of reservoir and the prospects of gas exploration in this region. There are seven types of trap in deep sequence according to the shape of trap,the ratio of length to width, the style of tectonic and fracture aswellas combination type.These trap types included anticline,fracture nose like rise,fracture step,fracture platform and fracture block. The favorable regions include the Zaozhou-Anda anticline belt,Zaodong-Chaoyanggou anticline belt,Chang wu-Zao dong nose-like structure,we expect to find a big gas trap there. The Anda-Zaozhou anticline belt developed in the northern part of central rise.It is 114km long along the North-south direction,and 21-41 km along the west-east direction with an area of 3 040km 2,there four boreholes which produce gas,these drilling wells includes the Fangsheng-1,Fangsheng-2,Fangsheng-4 and Zao sheng-1,The gas is found in the Denglouku Formation,base erosion crust.Cover rocks are the first and second number of Quantou Formation,and the mudsone of Denglouku Formation. Zaodong-Chaoyanggou anticline belt located in the middle part of the Xujiaweizi subsidence,extending there north-east,with an area of 2 590km 2.There are seven boreholes,only one of them produce gas.This anticline belt locates between Xujiaweizi subsidence and Yingshan subsidence.There are sandy conglomera.
1999, 17(4): 627-632.
Abstract:
The chemical compositions of gases released from sedimentary rocks by acidolysis, canned head-space gases of rocks and commercial natural gases, which were collected from different areas of various oil/gas bearing basins in China, were analyzed. Combined with natural gas generation and geological evolution of Ordos basin, Tarim basin, Ying-Qun basin and Huanghua depression, the chemical composition change resulted from natural gas migration was discussed in this paper. As a result of the obvious fractionation in the chemical composition during gas migration through porous sedimentary rock, the evidence that the molecular of methane will preferentially migrate to heavier gaseous hydrocarbons and normal butane to isobutane was recognized. 1. acidolysis gases released from sendimentary rock The compositional ratios of C1/C2+ and C1/C total of the gases released from sedimentary rocks by acidolysis, which were collected from 3 080～3 560 m section of well Chenchuan-1 in Ordos basin, decrease with increasing of the buried depth (as shown in Fig. 1 ). The organic matter in this section is from condensate to over-mature and three gas producing layers are found in brown sandstone with TOC values less than 0.3%. However, above two ratios resulted from thermal gas generation from organic matter should tend to increase with depth corresponding to its thermal maturation. This suggests that the molecular methane preferentially transfer to heavier gaseous hydrocarbons during gas migration. 2. canned head-space gases The methane concentration and heavier gaseous hydrocarbons concentration of canned head-space gases from reservoir rocks are far greater than those from source rocks (Fig. 2a), which are collected from 3 600～4 438 m section of well Chenchuan-1. And the ratio of C1/(C2+C3) is much bigger in the reservoir rock than source rock and becomes bigger and bigger with the depth (Fig. 2b). C1and C2+ concentration in the source rock of 6th to 10th section of Majiagou Ⅴ group are obviously larger than those of Majiagou Ⅰ group to Ⅳ group and the C1/(C2+C3) ratio becomes bigger with buried depth, indicating that natural gases generated in the 6th to 10th section of Majiagou Ⅴ group is migrated and trapped in the reservoir. 3. commercial natural gases The natural gases with the same origin identified by δ13C1 andδ13C2 values are trapped in different reservoirs, which are distributed in Donghetan reservoir of Tarim basin, Dongfang1-1 and Luodong15-1 reservoirs of Ying-Qun basin and Qikou sag of Huanghua depression. Their chemically compositional change of C1/C 2+, C1/C total and C total gaseous hydrocarbons /C total non-hydrocarbons in the vertical also reveals that the molecular of methane preferentially migrate to heavier gaseous hydrocarbons and hydrocarbons to non-hydrocarbons. As a result of migrational fractionation, the natural gas with much more methane than heavier hydrocarbons is trapped in relatively shallow reservoirs.
The chemical compositions of gases released from sedimentary rocks by acidolysis, canned head-space gases of rocks and commercial natural gases, which were collected from different areas of various oil/gas bearing basins in China, were analyzed. Combined with natural gas generation and geological evolution of Ordos basin, Tarim basin, Ying-Qun basin and Huanghua depression, the chemical composition change resulted from natural gas migration was discussed in this paper. As a result of the obvious fractionation in the chemical composition during gas migration through porous sedimentary rock, the evidence that the molecular of methane will preferentially migrate to heavier gaseous hydrocarbons and normal butane to isobutane was recognized. 1. acidolysis gases released from sendimentary rock The compositional ratios of C1/C2+ and C1/C total of the gases released from sedimentary rocks by acidolysis, which were collected from 3 080～3 560 m section of well Chenchuan-1 in Ordos basin, decrease with increasing of the buried depth (as shown in Fig. 1 ). The organic matter in this section is from condensate to over-mature and three gas producing layers are found in brown sandstone with TOC values less than 0.3%. However, above two ratios resulted from thermal gas generation from organic matter should tend to increase with depth corresponding to its thermal maturation. This suggests that the molecular methane preferentially transfer to heavier gaseous hydrocarbons during gas migration. 2. canned head-space gases The methane concentration and heavier gaseous hydrocarbons concentration of canned head-space gases from reservoir rocks are far greater than those from source rocks (Fig. 2a), which are collected from 3 600～4 438 m section of well Chenchuan-1. And the ratio of C1/(C2+C3) is much bigger in the reservoir rock than source rock and becomes bigger and bigger with the depth (Fig. 2b). C1and C2+ concentration in the source rock of 6th to 10th section of Majiagou Ⅴ group are obviously larger than those of Majiagou Ⅰ group to Ⅳ group and the C1/(C2+C3) ratio becomes bigger with buried depth, indicating that natural gases generated in the 6th to 10th section of Majiagou Ⅴ group is migrated and trapped in the reservoir. 3. commercial natural gases The natural gases with the same origin identified by δ13C1 andδ13C2 values are trapped in different reservoirs, which are distributed in Donghetan reservoir of Tarim basin, Dongfang1-1 and Luodong15-1 reservoirs of Ying-Qun basin and Qikou sag of Huanghua depression. Their chemically compositional change of C1/C 2+, C1/C total and C total gaseous hydrocarbons /C total non-hydrocarbons in the vertical also reveals that the molecular of methane preferentially migrate to heavier gaseous hydrocarbons and hydrocarbons to non-hydrocarbons. As a result of migrational fractionation, the natural gas with much more methane than heavier hydrocarbons is trapped in relatively shallow reservoirs.
1999, 17(4): 638-643.
Abstract:
Lower Ordovician carbonate in the Ordos basin is characteristed by its low organic matter content and high maturity, and its low residual TOC (total organic carbon) value can be not only regarded as its own initial feature but also contributed to the high maturity and high hydrocarbon potential. So whether it can be regarded as main source rock of the weathering-crust gas reservoir beneath the Upper Carboniferous/ Lower Ordovician parallel unconformity is still debatable. In this paper, the authors studied the hydrocarbon potential of Ordovician carbonates from the view of organic facies. Geochemical feature of different depositional environments includes: (1) Over 600 sample shows that carbonate formed in continental slope has a maximum average TOC value of 0.26%wt, then is that formed in gypsum lagoon (0.22%wt) and gypsodolomitic flat (0.21%); those deposited in dolomitic flat and open sea have lower TOC content (0.15%wt and 0.16%,respectively). TOC in carbonates formed in beach is minimum (0.15%). Even if taking the decrease of organic matter during maturity into account, the initial TOC value in the carbonate in its low-mature stage is still as little as in organic C～D proposed by Jones. (2) H/C and O/C atomic ratios of 20 kerogen samples all drop on the right part of the Van Krevelen chart. High O/C value indicates that the low H/C of organic matter in the carbonate is the feature during its formation instead the result of hydrocarbon generation, low H/C ratio also indicate a poor organic facies. (3) Mean Fe3+ /Fe2+ value is the highest of 33 carbonate samples formed in beach (8.55), then 5 open sea carbonate samples (0.78), 3 gypsum lagoon and gypsodolomitic plat carbonate samples (0.36). They are all higher than those in hydrocarbon generation or reservoir strata of Carboniferous-Permian (mean 0.05 of 12 samples) and Ordovician weathering crust (mean 0.07 of 15 samples), showing the lack of hydrocarbon and high oxidation potential. (4) Lithology and fossil feature also show a bad condition for the preservation of organic matter (oxidation and consumption of fauna). So most depositional environments of Lower Ordovician carbonate in the Ordos Basin (open sea, beach, dolomitic and gypsodolomitic flat) belong to organic facies C～D, with low hydrocarbon potential. Organic facies B can only exist in part of continental slope and part of gypsum lagoon, which is rather narrow. Organic facies study disproved the lower Ordovician carbonates to be good source rock in the Ordos Basin.
Lower Ordovician carbonate in the Ordos basin is characteristed by its low organic matter content and high maturity, and its low residual TOC (total organic carbon) value can be not only regarded as its own initial feature but also contributed to the high maturity and high hydrocarbon potential. So whether it can be regarded as main source rock of the weathering-crust gas reservoir beneath the Upper Carboniferous/ Lower Ordovician parallel unconformity is still debatable. In this paper, the authors studied the hydrocarbon potential of Ordovician carbonates from the view of organic facies. Geochemical feature of different depositional environments includes: (1) Over 600 sample shows that carbonate formed in continental slope has a maximum average TOC value of 0.26%wt, then is that formed in gypsum lagoon (0.22%wt) and gypsodolomitic flat (0.21%); those deposited in dolomitic flat and open sea have lower TOC content (0.15%wt and 0.16%,respectively). TOC in carbonates formed in beach is minimum (0.15%). Even if taking the decrease of organic matter during maturity into account, the initial TOC value in the carbonate in its low-mature stage is still as little as in organic C～D proposed by Jones. (2) H/C and O/C atomic ratios of 20 kerogen samples all drop on the right part of the Van Krevelen chart. High O/C value indicates that the low H/C of organic matter in the carbonate is the feature during its formation instead the result of hydrocarbon generation, low H/C ratio also indicate a poor organic facies. (3) Mean Fe3+ /Fe2+ value is the highest of 33 carbonate samples formed in beach (8.55), then 5 open sea carbonate samples (0.78), 3 gypsum lagoon and gypsodolomitic plat carbonate samples (0.36). They are all higher than those in hydrocarbon generation or reservoir strata of Carboniferous-Permian (mean 0.05 of 12 samples) and Ordovician weathering crust (mean 0.07 of 15 samples), showing the lack of hydrocarbon and high oxidation potential. (4) Lithology and fossil feature also show a bad condition for the preservation of organic matter (oxidation and consumption of fauna). So most depositional environments of Lower Ordovician carbonate in the Ordos Basin (open sea, beach, dolomitic and gypsodolomitic flat) belong to organic facies C～D, with low hydrocarbon potential. Organic facies B can only exist in part of continental slope and part of gypsum lagoon, which is rather narrow. Organic facies study disproved the lower Ordovician carbonates to be good source rock in the Ordos Basin.
1999, 17(4): 655-658.
Abstract:
Based on the simulation experiment it is discovered that the generation of fluorene series compounds on the biological precursors with the same structure. At a certain temperature, β carotene can transform into fluorene series and the reaction of sulphur with chain organic compounds can form more abundant fluorene series. While aromatizing, some changes such as methyl coming off, methyl removing and hydrogen of methyl coming off may take place in β carotene, which will form a great deal of free radicals, and the fluorene series will be formed when the free radicals form bond; The diphenyl methanes formed by β carotene may transform into fluorene series compounds; The reaction of sulphur with chain compounds forms possibly some diphenyl methanes at first, then sulphur acts on the products and seizes the α H of the two aromatic nuclei to form free radicals. When the free radical of one aromatic nucleus combines another one's, fuorene is formed. Although flourene series have the biological carbon skeleton, they should not be referred to as biomarkers for they were mainly formed by geochemical synthesis.
Based on the simulation experiment it is discovered that the generation of fluorene series compounds on the biological precursors with the same structure. At a certain temperature, β carotene can transform into fluorene series and the reaction of sulphur with chain organic compounds can form more abundant fluorene series. While aromatizing, some changes such as methyl coming off, methyl removing and hydrogen of methyl coming off may take place in β carotene, which will form a great deal of free radicals, and the fluorene series will be formed when the free radicals form bond; The diphenyl methanes formed by β carotene may transform into fluorene series compounds; The reaction of sulphur with chain compounds forms possibly some diphenyl methanes at first, then sulphur acts on the products and seizes the α H of the two aromatic nuclei to form free radicals. When the free radical of one aromatic nucleus combines another one's, fuorene is formed. Although flourene series have the biological carbon skeleton, they should not be referred to as biomarkers for they were mainly formed by geochemical synthesis.
