2000 Vol. 18, No. 2
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Display Method:
2000, 18(2): 165-171.
Abstract:
In the light of sequence-basin-earth theory in conjunction with previou s stra tigraphy,sedimentology,basin analysis and sequence stratigraphy,the sequence fil ling dyna mics of Youjiang Basin has been studied in detail.Fi ve hierachies of sequence boundaries and corresponding five hierachies of deposi tional sequences,1 super-order sequence,4 1st-order sequences,6 2nd-order sequen ces,11 sequence sets,47 3rd-order sequences and a certain amount of 4th-and 5th- order seq uences have been recognized for the first time.Relationship between sequence bo un dary and geological events,and that of sequence hierachy and basin type have bee n discusse d,and then sequence stratigraphic framework of Youjiang Basin has also been established.By the cognition that sequence development of rifting basin is mai nly controlled by synsedimentary fault and fundamental subsidence,relationship b etween sequence genesis and basin structure has been set up. The sequence f ramework and filling proccess are obviously distinct within different genetic ba sins. Finally,the author delibr ated the sequence filling dynamic process and related basin evolution of the You jiang Basin.On the basis of the research result mentioned above,this paper sugg e sts that the sequence filling process of the Youjiang Basin can be subdivided in to four stages:intracontinental rifting,marginal rifting,retroarc rifting and fo reland basin,constituting a complete tectonic cycles during Hercynian-In dosinian stage.
In the light of sequence-basin-earth theory in conjunction with previou s stra tigraphy,sedimentology,basin analysis and sequence stratigraphy,the sequence fil ling dyna mics of Youjiang Basin has been studied in detail.Fi ve hierachies of sequence boundaries and corresponding five hierachies of deposi tional sequences,1 super-order sequence,4 1st-order sequences,6 2nd-order sequen ces,11 sequence sets,47 3rd-order sequences and a certain amount of 4th-and 5th- order seq uences have been recognized for the first time.Relationship between sequence bo un dary and geological events,and that of sequence hierachy and basin type have bee n discusse d,and then sequence stratigraphic framework of Youjiang Basin has also been established.By the cognition that sequence development of rifting basin is mai nly controlled by synsedimentary fault and fundamental subsidence,relationship b etween sequence genesis and basin structure has been set up. The sequence f ramework and filling proccess are obviously distinct within different genetic ba sins. Finally,the author delibr ated the sequence filling dynamic process and related basin evolution of the You jiang Basin.On the basis of the research result mentioned above,this paper sugg e sts that the sequence filling process of the Youjiang Basin can be subdivided in to four stages:intracontinental rifting,marginal rifting,retroarc rifting and fo reland basin,constituting a complete tectonic cycles during Hercynian-In dosinian stage.
2000, 18(2): 181-189.
Abstract:
Sedimentary suite, which deposited from littoral to neritic environments and wer e mainly composed of carbonate rocks, developed on the southern margin of the up per Yangtze craton basin during the middle Devonian Epoch to the Carboniferous P eriod. This set of suite, which was the products of transgression and regression processes of plaeo marine water with the condition of stable tectonics, recorde d the changing processes of plaeo sea-level precisely. The study of sea-level change is helpful to the division of sequence、the research of sequence stacking patterns and the foundation of sequence time-space pattern through the analysi s of high-frequency sequences. The middle Devonian series to Carboniferous system strata high-frequency sequ ences in the study area may be distinguished from three orders corresponding to the terminology of sequence stratigraphy. Sixth-order sequence is corrsponding to the cyclothems, the fifth-order sequence to the parasequence and the fourth -order sequence to the parasequence set. Composite sea-level changes with th e different frequences and cycles which are caused by the Milankovitch cycles co ntrol the formation of high-frequency sequences of the different orders. Sixt h-order sequence is equal to the meter-scale cyclic sequence. Its genetic mech anism is punctuated-aggradational allocyclic mechanism which is related to high -frequence cyclic sea-level changes resulted from the Milankovitch cycle. Th e criteria for recognition of sixth-order sequence include the rock types,bou ndary surface nature and sedimentary environments. In the study area there are 1 116 sixth-order sequences, belonging to three types including carbonate rock type,clastic rock type and hybrid sediment type. All these sixth-order sequen ces are represented by progradational sequence consisting of an upward thickenin g, shallowing and coarsening rocks, and bounded by puncturated-deeping bounda ry or eroding surfaces. The upward stacks of two or more sixth-order sequence s form fifth-order sequence, whose bottom or top boundary surfaces are more cl ear eroding surfaces or abrupt lithofacies change surfaces, and whose number is 434 in the study area. The upward stacks of four or less fifth-order sequences inform fourth-order sequence, whose number is 134 in the study area. The development of high-frequency sequences are controled by the changes of sea-level,provenance,environment,weather,tectonic subsidence. Sixth-order, fifth-order and fourth-order sequences are the products of high-frequency and short cycle sea-level changes control ed by low-frequency and long cycle se a-level changes. So,through the analysis of the high-frequency sequences with the different characteristics and cycle stacking patterns, the low-frequency and long cycle sea-level changes may be explained. In the craton basin margin environment, during the rising stages of low-frequency sea-level changes, th e high frequency sequences are characterized by the "drowning band", while by th e "exposing band" in the standstill and fall stages.
Sedimentary suite, which deposited from littoral to neritic environments and wer e mainly composed of carbonate rocks, developed on the southern margin of the up per Yangtze craton basin during the middle Devonian Epoch to the Carboniferous P eriod. This set of suite, which was the products of transgression and regression processes of plaeo marine water with the condition of stable tectonics, recorde d the changing processes of plaeo sea-level precisely. The study of sea-level change is helpful to the division of sequence、the research of sequence stacking patterns and the foundation of sequence time-space pattern through the analysi s of high-frequency sequences. The middle Devonian series to Carboniferous system strata high-frequency sequ ences in the study area may be distinguished from three orders corresponding to the terminology of sequence stratigraphy. Sixth-order sequence is corrsponding to the cyclothems, the fifth-order sequence to the parasequence and the fourth -order sequence to the parasequence set. Composite sea-level changes with th e different frequences and cycles which are caused by the Milankovitch cycles co ntrol the formation of high-frequency sequences of the different orders. Sixt h-order sequence is equal to the meter-scale cyclic sequence. Its genetic mech anism is punctuated-aggradational allocyclic mechanism which is related to high -frequence cyclic sea-level changes resulted from the Milankovitch cycle. Th e criteria for recognition of sixth-order sequence include the rock types,bou ndary surface nature and sedimentary environments. In the study area there are 1 116 sixth-order sequences, belonging to three types including carbonate rock type,clastic rock type and hybrid sediment type. All these sixth-order sequen ces are represented by progradational sequence consisting of an upward thickenin g, shallowing and coarsening rocks, and bounded by puncturated-deeping bounda ry or eroding surfaces. The upward stacks of two or more sixth-order sequence s form fifth-order sequence, whose bottom or top boundary surfaces are more cl ear eroding surfaces or abrupt lithofacies change surfaces, and whose number is 434 in the study area. The upward stacks of four or less fifth-order sequences inform fourth-order sequence, whose number is 134 in the study area. The development of high-frequency sequences are controled by the changes of sea-level,provenance,environment,weather,tectonic subsidence. Sixth-order, fifth-order and fourth-order sequences are the products of high-frequency and short cycle sea-level changes control ed by low-frequency and long cycle se a-level changes. So,through the analysis of the high-frequency sequences with the different characteristics and cycle stacking patterns, the low-frequency and long cycle sea-level changes may be explained. In the craton basin margin environment, during the rising stages of low-frequency sea-level changes, th e high frequency sequences are characterized by the "drowning band", while by th e "exposing band" in the standstill and fall stages.
2000, 18(2): 198-204.
Abstract:
The study area included Sichuan,Yunnan,Guizhou and Guangxi, there, the strata of lower and middle Triassic are widely distributed and well dev eloped, it is one of important areas can be used to study the sequence division, correlation and framework of Triassic system. Therefore, the paper based on th esequence stratigraphy theory, discussed in detail the characteristics of thes equence boundary surface which included uncomformity surface, lithologic-charac ter and facies change surface, karst surface and errosion surface, etc. Among them, the uncomformlty surface, errosion surface and karst surface are type-Ⅰ bo undary surface, and lithologic-character and facies change surface are type-Ⅱ boundany surfaces. Based on the above, the paper divided lower and middle Triassic into six third order seauences, which are namedas S The study area included Sichuan,Yunnan,Guizhou and Guangxi, the re, the strata of lower and middle Triassic are widely distributed and well dev eloped, it is one of important areas can be used to study the sequence division, correlation and framework of Triassic system. Therefore, the paper based on th e sequence stratigraphy theory, discussed in detail the characteristics of the s equence boundary surface which included uncomformity surface, lithologic-charac ter and facies change surface, karst surface and errosion surface, etc. Among th em, the uncomformlty surface, errosion surface and karst surface are type-Ⅰ bo undary surface, and lithologic-character and facies change surface are type-Ⅱ boundany surfaces. Based on the above, the paper divided lower and middle Triassic into six third order seauences, which are namedas S1 to S6, In the view of geologic time, it is known that early Triassic period prolonged 3.9 Ma, S0 S1,S2 and S3 prolonged 1.3 Ma respectively, and middle Tras sic period prolonged 6.1 Ma, S4,S5 and S6 prolonged 2.03 Ma respectively. From the point of sequence boundary surface characteristics, S2,S3,S4 and S5 are type-Ⅰ sequences, and S1 and S6 are type-Ⅱ sequences. The n the paper correlated each sequence from the study area, and built the sequence stratigraphy framework of lower and middle Triassic which showed the evolution of patterns and their relationship of different system tract.1 to S6, In the view of geologic time, it is known that early Triassic period prolonged 3.9 Ma, S0 S1,S2 and S3 prolonged 1.3 Ma respectively, and middle Tras sic period prolonged 6.1 Ma, S4,S5 and S6 prolonged 2.03 Ma respectively. From the point of sequence boundary surface characteristics, S2,S3,S4 a nd S5 are type-Ⅰ sequences, and S1 and S6 are type-Ⅱ sequences. The n the paper correlated each sequence from the study area, and built the sequence stratigraphy framework of lower and middle Triassic which showed the evolution of patterns and their relationship of different system tract.
The study area included Sichuan,Yunnan,Guizhou and Guangxi, there, the strata of lower and middle Triassic are widely distributed and well dev eloped, it is one of important areas can be used to study the sequence division, correlation and framework of Triassic system. Therefore, the paper based on th esequence stratigraphy theory, discussed in detail the characteristics of thes equence boundary surface which included uncomformity surface, lithologic-charac ter and facies change surface, karst surface and errosion surface, etc. Among them, the uncomformlty surface, errosion surface and karst surface are type-Ⅰ bo undary surface, and lithologic-character and facies change surface are type-Ⅱ boundany surfaces. Based on the above, the paper divided lower and middle Triassic into six third order seauences, which are namedas S The study area included Sichuan,Yunnan,Guizhou and Guangxi, the re, the strata of lower and middle Triassic are widely distributed and well dev eloped, it is one of important areas can be used to study the sequence division, correlation and framework of Triassic system. Therefore, the paper based on th e sequence stratigraphy theory, discussed in detail the characteristics of the s equence boundary surface which included uncomformity surface, lithologic-charac ter and facies change surface, karst surface and errosion surface, etc. Among th em, the uncomformlty surface, errosion surface and karst surface are type-Ⅰ bo undary surface, and lithologic-character and facies change surface are type-Ⅱ boundany surfaces. Based on the above, the paper divided lower and middle Triassic into six third order seauences, which are namedas S1 to S6, In the view of geologic time, it is known that early Triassic period prolonged 3.9 Ma, S0 S1,S2 and S3 prolonged 1.3 Ma respectively, and middle Tras sic period prolonged 6.1 Ma, S4,S5 and S6 prolonged 2.03 Ma respectively. From the point of sequence boundary surface characteristics, S2,S3,S4 and S5 are type-Ⅰ sequences, and S1 and S6 are type-Ⅱ sequences. The n the paper correlated each sequence from the study area, and built the sequence stratigraphy framework of lower and middle Triassic which showed the evolution of patterns and their relationship of different system tract.1 to S6, In the view of geologic time, it is known that early Triassic period prolonged 3.9 Ma, S0 S1,S2 and S3 prolonged 1.3 Ma respectively, and middle Tras sic period prolonged 6.1 Ma, S4,S5 and S6 prolonged 2.03 Ma respectively. From the point of sequence boundary surface characteristics, S2,S3,S4 a nd S5 are type-Ⅰ sequences, and S1 and S6 are type-Ⅱ sequences. The n the paper correlated each sequence from the study area, and built the sequence stratigraphy framework of lower and middle Triassic which showed the evolution of patterns and their relationship of different system tract.
2000, 18(2): 210-214.
Abstract:
Nowadays the research of sequence stratigraphy h as become a hot spot problem in geology. But, it is very difficult to use the se quence stratigraphy theory to divide the sequence of deep water basin sedimentar y layer, this is because that the lithologic-character of deep water basin sedi mentary layer is very monotonous. In study area, from Devonian Period to Triassi c P eriod the strata of the deep water basin sediments are very well developed whi ch included turbidite and siliceous-mudstone sediment. So the paper discussed i n detail the sequence characteristics of deep water basin sedimentary layer. The results showed that the sequ ence boundary surface characteristic of turbidite sediments was obvious,which di splayd that the surface was irregular and the bottom of LST sandstones developed many different erosion surface, etc, and the sequence evolution of t urbidite was related to the turbidite fan's evolution. The sequence division of s iliceous-mudstone sediment can be identified through the analyses of content pr oportion and origin of mudstone.
Nowadays the research of sequence stratigraphy h as become a hot spot problem in geology. But, it is very difficult to use the se quence stratigraphy theory to divide the sequence of deep water basin sedimentar y layer, this is because that the lithologic-character of deep water basin sedi mentary layer is very monotonous. In study area, from Devonian Period to Triassi c P eriod the strata of the deep water basin sediments are very well developed whi ch included turbidite and siliceous-mudstone sediment. So the paper discussed i n detail the sequence characteristics of deep water basin sedimentary layer. The results showed that the sequ ence boundary surface characteristic of turbidite sediments was obvious,which di splayd that the surface was irregular and the bottom of LST sandstones developed many different erosion surface, etc, and the sequence evolution of t urbidite was related to the turbidite fan's evolution. The sequence division of s iliceous-mudstone sediment can be identified through the analyses of content pr oportion and origin of mudstone.
2000, 18(2): 221-226.
Abstract:
Based on the theory of comparative sedimentology, this paper gives the detailed description of both the modern anastomosed river (Qiqihaer Nenjiang s ection) and the corresponding ancient ones(Huanghua depression and Qaidam basin ). The paper presents the depositional processes,characteristics of sedimentary rhythm,geometry and heterogeneity of the modern anastomosed river with a ref erence material home and abroad, and generalizes the depesitiomal model. The river in Qiqihaer has the following features, that is, low slope gradient, small with/depth ratio, fast aggradation rate, the channel anastomosed, and conf ined lateral migration, and soon. The river can be divided into six sub-facies s uch as anastomosed channel, natural levee, crevasse splay, river beach, inter-r iver lake, and swamp. All provide the basis for the analysis of ancient correspo nding reservoir quality sand bodies. The ancient anastomosed river, influenced by post-depositional physical or che mical reaction such as diagenesis, presents relative difference compared with th e modern one, but both have similar sedimentary characteristics in morphology, e nvironments, sand body structure, rhythm, and so on. It is this similarity that provides the basis of comparative sedimentology and its application. The authors discuss the formation mechanism on the anastomosed river so as to put forward a general discipline as a direction for further study. The river's formation is controlled by various factors, the authors explore that it is relat ed to the low slope gradient, massive vegetation, flood development, and the u niform development. Sometimes the anastomosed river can be transformed from bra ided river. With the knowledge and comparative study on both the modern and ancient anastomo sing river, we can analyse geometry, continuity, and heterogeneity of undergroun d related sand bodies, which is very important in the course of exploration and development of petroleum.
Based on the theory of comparative sedimentology, this paper gives the detailed description of both the modern anastomosed river (Qiqihaer Nenjiang s ection) and the corresponding ancient ones(Huanghua depression and Qaidam basin ). The paper presents the depositional processes,characteristics of sedimentary rhythm,geometry and heterogeneity of the modern anastomosed river with a ref erence material home and abroad, and generalizes the depesitiomal model. The river in Qiqihaer has the following features, that is, low slope gradient, small with/depth ratio, fast aggradation rate, the channel anastomosed, and conf ined lateral migration, and soon. The river can be divided into six sub-facies s uch as anastomosed channel, natural levee, crevasse splay, river beach, inter-r iver lake, and swamp. All provide the basis for the analysis of ancient correspo nding reservoir quality sand bodies. The ancient anastomosed river, influenced by post-depositional physical or che mical reaction such as diagenesis, presents relative difference compared with th e modern one, but both have similar sedimentary characteristics in morphology, e nvironments, sand body structure, rhythm, and so on. It is this similarity that provides the basis of comparative sedimentology and its application. The authors discuss the formation mechanism on the anastomosed river so as to put forward a general discipline as a direction for further study. The river's formation is controlled by various factors, the authors explore that it is relat ed to the low slope gradient, massive vegetation, flood development, and the u niform development. Sometimes the anastomosed river can be transformed from bra ided river. With the knowledge and comparative study on both the modern and ancient anastomo sing river, we can analyse geometry, continuity, and heterogeneity of undergroun d related sand bodies, which is very important in the course of exploration and development of petroleum.
2000, 18(2): 234-240.
Abstract:
The Western Yunnan Plateau (WYP) is located at the southeastern Qinghai- Tib et plateau.The Yinggehai at the southeast termination of the Red River Fault Zo ne is a new (mainly Neogene) strike-slip basin which is one of the peripheral b asins of the WYP.The WYP uplift results in not only sharply increasing of sedime ntation rate and sedimentation flux in the Yinggehai basin,discordance of se qu ence interface,violently increasing of clastic supplying volume from the WYP,but also increasing of sedimentation rate in the interior plateau basins,changing o f filling sequence and uplift-denudation peridically.The history of tectonic su bsidence is very similiar in both Yinggehai basin and interior plateau basin s and,t hey kept basically the same pace in tectonic subsidence.The marks such as the ac cumu lation peak period in Yinggehai basin and interior plateau basins,the denuda tio n period of interior plateau basins,the peak period of clastic supplying from WY P denuded,respond to a rapid upliftiong of WYP.The lower accumulation rate and t h e reduction steeply of clastic supplying from WYP denuded respond to relative st able period of WYP.Based on these marks respond to uplift,we reconstruct uplifti n g history of WYP,including initial uplifting (23～19 Ma),rapid uplifting (16.2 ～11 Ma),denudation planation(11～5.3 Ma),accelerated denudation and uplift(1.6～0 Ma).T he WYP was formed basically in 5.3～1.6 Ma,the average relative to uplifting rat e wa s 0.5～0.57mm/a and maximmum in 2.5 Ma.The altitude above sea-level of WYP was uplifted regionally about 610～700 m in past 1.6 Ma.
The Western Yunnan Plateau (WYP) is located at the southeastern Qinghai- Tib et plateau.The Yinggehai at the southeast termination of the Red River Fault Zo ne is a new (mainly Neogene) strike-slip basin which is one of the peripheral b asins of the WYP.The WYP uplift results in not only sharply increasing of sedime ntation rate and sedimentation flux in the Yinggehai basin,discordance of se qu ence interface,violently increasing of clastic supplying volume from the WYP,but also increasing of sedimentation rate in the interior plateau basins,changing o f filling sequence and uplift-denudation peridically.The history of tectonic su bsidence is very similiar in both Yinggehai basin and interior plateau basin s and,t hey kept basically the same pace in tectonic subsidence.The marks such as the ac cumu lation peak period in Yinggehai basin and interior plateau basins,the denuda tio n period of interior plateau basins,the peak period of clastic supplying from WY P denuded,respond to a rapid upliftiong of WYP.The lower accumulation rate and t h e reduction steeply of clastic supplying from WYP denuded respond to relative st able period of WYP.Based on these marks respond to uplift,we reconstruct uplifti n g history of WYP,including initial uplifting (23～19 Ma),rapid uplifting (16.2 ～11 Ma),denudation planation(11～5.3 Ma),accelerated denudation and uplift(1.6～0 Ma).T he WYP was formed basically in 5.3～1.6 Ma,the average relative to uplifting rat e wa s 0.5～0.57mm/a and maximmum in 2.5 Ma.The altitude above sea-level of WYP was uplifted regionally about 610～700 m in past 1.6 Ma.
2000, 18(2): 248-252.
Abstract:
The braided delta front is developed in WM oilfield, Turpan-Hami Basin, which is composed of the underwater distributary channels, mouth bars, distal sands, sh eet-like sands, and interchannel muds microfacies. The deposition features of t he braided deltas are low sedimentary maturation and abundant current structures caused by the traction current. The underwater distributary channels have an er osion surface in the channel bottom, and are fining upward from conglomerates in the base to fine-sandstones in the top of the channels. They are 2.5m in rhythm, and 4～10 m in complicate rhythms, and are 200～400 meters in width. The para llel bedding are well developed in the sandstones. While the mouth bars are cour sing upward from siltstones to sandstones, and are large than 4 m in thickness. The sheet-like sands are mainly sandstones, fine to medium grained, well sorted and rounded, and are mostly coursing upward. They are 3-4m in thickness. The rivers in the braided delta are strong, so that the distributary channels s till erode downwards after entering lake,and forms underwater distributary cha nnels as a result of water flow in the bottom of the lake, The underwater distri butary channels can frequently migrate laterally so as to form sheet-like sandb odies (complicated sandbodies of the distributary channels). Some uneroded inter channel muds are scatterd in the inner of complicated sandbodies of the distrib utay channels, and will be flowing barriers. The volumes of the mouth bars depend directly on the amounts of sediments carrie d by underwater distributary channels,while the shapes are partly influenced by the waves of the lake. The mouth bars may be ellipsoid parallel to underwater d istributary channels (i.e. perpendicular to the shore of lake),but may become fa n-like and even ellipsoid parallel to the shore of the lake by the modification of the waves. The nine kinds of relationship between the underwater distributary channels and the mouth bars are proposed according to the strength of the curr ents in the distributary channels and the strength of the waves in the lake. It has concluded the shapes of the mouth bars in the Sanjianfang Formation, WM Oilf ield, Turpan-Hami Basin. The underwater distributary channels of next stage may flow by the franks of the former mouth bars and develop forward; as a result,th e mouth bars are presented along with the franks of the underwater distributary channels. The underwater distributary channels of next stage, however, may flow on the top of the former mouth bars and erode them. They may cut part of the mou th bar deposits and may form composed sand bodies of the mouth bar (upper) and u nderwater distributary channel (lower) if erosion is weak. They way cut all the mouth bar as the latter is never presented if the erosion is strong and the form er mouth bar is too thin. A kind of thin-beded, fine-grained, lenticular sand bodies, which is called dis tal sands microfacies in the paper, is deposited in inter bars, shallow lakes in the weak wave region by the reworking of deposits of the mouth bars and underwa ter distributary channels by the weak waves or other currents in the lake. Howev e r, in the region of strong waves, the sediments of the underwater distributary c hannels and the mouth bars are by strong waves and migrated laterally to form co ntinuos, large scaled sheet-like sands. When the accomodation space of the lake basin is smaller, the braided deltas are well developed, and inter channel mud deposits are eroded by the underwater dis tributary channels in braided deltas, so as to form sheet-like sandbodies (compl icated sandbodies of the distributary channels). When the accomodation space of the lake basin is larger, the braided deltas are less developed, and the underwa ter distributary channels can not stretch too far away and channels sandbodies a re much more isolated, while the mouth bars are relatively more developed.
The braided delta front is developed in WM oilfield, Turpan-Hami Basin, which is composed of the underwater distributary channels, mouth bars, distal sands, sh eet-like sands, and interchannel muds microfacies. The deposition features of t he braided deltas are low sedimentary maturation and abundant current structures caused by the traction current. The underwater distributary channels have an er osion surface in the channel bottom, and are fining upward from conglomerates in the base to fine-sandstones in the top of the channels. They are 2.5m in rhythm, and 4～10 m in complicate rhythms, and are 200～400 meters in width. The para llel bedding are well developed in the sandstones. While the mouth bars are cour sing upward from siltstones to sandstones, and are large than 4 m in thickness. The sheet-like sands are mainly sandstones, fine to medium grained, well sorted and rounded, and are mostly coursing upward. They are 3-4m in thickness. The rivers in the braided delta are strong, so that the distributary channels s till erode downwards after entering lake,and forms underwater distributary cha nnels as a result of water flow in the bottom of the lake, The underwater distri butary channels can frequently migrate laterally so as to form sheet-like sandb odies (complicated sandbodies of the distributary channels). Some uneroded inter channel muds are scatterd in the inner of complicated sandbodies of the distrib utay channels, and will be flowing barriers. The volumes of the mouth bars depend directly on the amounts of sediments carrie d by underwater distributary channels,while the shapes are partly influenced by the waves of the lake. The mouth bars may be ellipsoid parallel to underwater d istributary channels (i.e. perpendicular to the shore of lake),but may become fa n-like and even ellipsoid parallel to the shore of the lake by the modification of the waves. The nine kinds of relationship between the underwater distributary channels and the mouth bars are proposed according to the strength of the curr ents in the distributary channels and the strength of the waves in the lake. It has concluded the shapes of the mouth bars in the Sanjianfang Formation, WM Oilf ield, Turpan-Hami Basin. The underwater distributary channels of next stage may flow by the franks of the former mouth bars and develop forward; as a result,th e mouth bars are presented along with the franks of the underwater distributary channels. The underwater distributary channels of next stage, however, may flow on the top of the former mouth bars and erode them. They may cut part of the mou th bar deposits and may form composed sand bodies of the mouth bar (upper) and u nderwater distributary channel (lower) if erosion is weak. They way cut all the mouth bar as the latter is never presented if the erosion is strong and the form er mouth bar is too thin. A kind of thin-beded, fine-grained, lenticular sand bodies, which is called dis tal sands microfacies in the paper, is deposited in inter bars, shallow lakes in the weak wave region by the reworking of deposits of the mouth bars and underwa ter distributary channels by the weak waves or other currents in the lake. Howev e r, in the region of strong waves, the sediments of the underwater distributary c hannels and the mouth bars are by strong waves and migrated laterally to form co ntinuos, large scaled sheet-like sands. When the accomodation space of the lake basin is smaller, the braided deltas are well developed, and inter channel mud deposits are eroded by the underwater dis tributary channels in braided deltas, so as to form sheet-like sandbodies (compl icated sandbodies of the distributary channels). When the accomodation space of the lake basin is larger, the braided deltas are less developed, and the underwa ter distributary channels can not stretch too far away and channels sandbodies a re much more isolated, while the mouth bars are relatively more developed.
2000, 18(2): 259-261.
Abstract:
Kunyang Group of Mesoproterozoic in central Yunnan province consists of 4 Formations: Yinmin Formation, Luoxue Formation, Etouchang Formation and Luzhi j iang Formation. Yinmin Formation is composed of clastic stone with the sedimenta ry structures developed characteristically in storm deposits, which includes gut ter casts, hummocky or sunken cross bedding, and graded bedding. The storm depos its consist of 4 types of lithofacies: a-sandstone with gutter casts and graded bedding, b-sandstone with hummocky or sunken cross bedding, c-siltstone and muds tone with homogeneous bedding, and d-argillite with horizontal bedding. These l ithofacies represent respectively deposits of storm current (a), deposits of sto rm wave(b), rapid suspended sediment (event deposits, c) and slow suspended sed iment (background deposits, d). These lithofacies constitute various sedimentary sequences of storm deposits. Sequence 1 is an assemblage upward of graded sands tone with gutter casts, sandstone with hummocky or sunken cross bedding, siltsto ne and mudstone with homogeneous bedding, and argillite with horizontal bedding. Sequence 2 is of graded sandstone with scouring casts, sandstone with parallel bedding, sandstone with wave ripple cross bedding and siltstone and mudstone wit h homogeneous bedding and horizontal bedding. Sequence 3 is of sandstone with hu mmocky or sunken cross bedding, fine sandstone with wave ripple cross bedding, a nd siltstone and mudstone with homogeneous bedding and horizontal bedding. The d iscovery of tempestite in Yinmin Formation, Kunyang Group of Mesoproterozoic in central Yunnan province reflects that the atmosphere, hydrosphere and their inte raction in Mesoprotozoic are similar to those in nowadays. The central Yunnan Pr ovince in Mesoprotozoic located in the area of low latitude（5°～30°） where deve loped storm. Meanwhile,the discovery of the storm deposits has important significance to explain the genesis of the sandstone with grade bedding and interpret the sequence of Kunyang Group.
Kunyang Group of Mesoproterozoic in central Yunnan province consists of 4 Formations: Yinmin Formation, Luoxue Formation, Etouchang Formation and Luzhi j iang Formation. Yinmin Formation is composed of clastic stone with the sedimenta ry structures developed characteristically in storm deposits, which includes gut ter casts, hummocky or sunken cross bedding, and graded bedding. The storm depos its consist of 4 types of lithofacies: a-sandstone with gutter casts and graded bedding, b-sandstone with hummocky or sunken cross bedding, c-siltstone and muds tone with homogeneous bedding, and d-argillite with horizontal bedding. These l ithofacies represent respectively deposits of storm current (a), deposits of sto rm wave(b), rapid suspended sediment (event deposits, c) and slow suspended sed iment (background deposits, d). These lithofacies constitute various sedimentary sequences of storm deposits. Sequence 1 is an assemblage upward of graded sands tone with gutter casts, sandstone with hummocky or sunken cross bedding, siltsto ne and mudstone with homogeneous bedding, and argillite with horizontal bedding. Sequence 2 is of graded sandstone with scouring casts, sandstone with parallel bedding, sandstone with wave ripple cross bedding and siltstone and mudstone wit h homogeneous bedding and horizontal bedding. Sequence 3 is of sandstone with hu mmocky or sunken cross bedding, fine sandstone with wave ripple cross bedding, a nd siltstone and mudstone with homogeneous bedding and horizontal bedding. The d iscovery of tempestite in Yinmin Formation, Kunyang Group of Mesoproterozoic in central Yunnan province reflects that the atmosphere, hydrosphere and their inte raction in Mesoprotozoic are similar to those in nowadays. The central Yunnan Pr ovince in Mesoprotozoic located in the area of low latitude（5°～30°） where deve loped storm. Meanwhile,the discovery of the storm deposits has important significance to explain the genesis of the sandstone with grade bedding and interpret the sequence of Kunyang Group.
2000, 18(2): 268-272.
Abstract:
Based on the study of characterislies of reservoir petrology and sedimentology in target strata,the authors have put forward that the depositional environment of the Sha-3 member is river-shore shallow lake environment,the sedimentary sy stem belongs to lakeshore depositional system,and the sedimentary facies of the reservoir are braided river delta facies. The Sha-3(1) member is one of the most important reservoirs in Chengdao oilfiel d,sedimentary characteristics of which are very important for the rolling deve lopment and the evaluation of prospecting areas.The study concludes:(1) The rese rvoir of Sha-3(1) member is a set of coarse grain detrital sediment,belonging to river-shallow lake side depositional system with hraided river delta facies.(2) Massive gritstone,trough cross-stratification fine-middle sandstone,wave cross-s tratification fine sandstone and parallel-stratification fine sandstone are the most favourable petrofacies for petroleum accumilation;The combinations of Sf→M m,Sm→Mm,St→Mm and Sr→Sh are the most developed petrofacies combination type,and also the most favourable for petroleum accumulation.(3)The sedimentary der ivation is mainly northeast and southwest. The strelch of sedimentary facies,whi ch is under control of leetonics,goes north-northwest and south-southeast. The s edimentary province is geographically high in the west and low in the east,and high in the south and low in the north.
Based on the study of characterislies of reservoir petrology and sedimentology in target strata,the authors have put forward that the depositional environment of the Sha-3 member is river-shore shallow lake environment,the sedimentary sy stem belongs to lakeshore depositional system,and the sedimentary facies of the reservoir are braided river delta facies. The Sha-3(1) member is one of the most important reservoirs in Chengdao oilfiel d,sedimentary characteristics of which are very important for the rolling deve lopment and the evaluation of prospecting areas.The study concludes:(1) The rese rvoir of Sha-3(1) member is a set of coarse grain detrital sediment,belonging to river-shallow lake side depositional system with hraided river delta facies.(2) Massive gritstone,trough cross-stratification fine-middle sandstone,wave cross-s tratification fine sandstone and parallel-stratification fine sandstone are the most favourable petrofacies for petroleum accumilation;The combinations of Sf→M m,Sm→Mm,St→Mm and Sr→Sh are the most developed petrofacies combination type,and also the most favourable for petroleum accumulation.(3)The sedimentary der ivation is mainly northeast and southwest. The strelch of sedimentary facies,whi ch is under control of leetonics,goes north-northwest and south-southeast. The s edimentary province is geographically high in the west and low in the east,and high in the south and low in the north.
2000, 18(2): 279-283.
Abstract:
Reservoir's recovery percentage of oil is equal to the injected water's swe eping efficiency in macro and the oil displacement efficiency of the injected w ater in micro. So the final reservoir's recovery percentage of oil can be affected by the oil displacement effecency. Ansai oilfield is a typical low permeability oilfield. It's reservoir is Yanchan g formation of Triassic system,and the oil is mainly reserved in Chang6 reservoir of Yanchang ormation.Pingqiao and Wangyao are located in the north and the sou th of Ansai oilfield.The study about the oil displacement efficiency of Chang6 r eservoir in the two areas has practical significances. According to the study it can be seen that the differenct petrologic feature leads to the difference in pore structure and petrophysical property between the two areas under the later diageneses. The results are that the heterogeneity of pore structure in Pingqiao is more serious than in Wangyao,and the petrophysical property in Wangyao is better than in Pingqiao. The natural sandstone micromodels are made with sampled cores.Using the micromod els,the displacement experiments of oil and water have been done. Experimental results indicate that oil displacement efficiency of the Chang6 reservoir in Wang yao (40.34%) is higher than in Pingqiao (30.48%). The difference of pore structu re, especially the difference of heterogeneity of pore structure is the reason that leads to the great difference of oil displacement efficiency between Wangyao and Pingqiao.
Reservoir's recovery percentage of oil is equal to the injected water's swe eping efficiency in macro and the oil displacement efficiency of the injected w ater in micro. So the final reservoir's recovery percentage of oil can be affected by the oil displacement effecency. Ansai oilfield is a typical low permeability oilfield. It's reservoir is Yanchan g formation of Triassic system,and the oil is mainly reserved in Chang6 reservoir of Yanchang ormation.Pingqiao and Wangyao are located in the north and the sou th of Ansai oilfield.The study about the oil displacement efficiency of Chang6 r eservoir in the two areas has practical significances. According to the study it can be seen that the differenct petrologic feature leads to the difference in pore structure and petrophysical property between the two areas under the later diageneses. The results are that the heterogeneity of pore structure in Pingqiao is more serious than in Wangyao,and the petrophysical property in Wangyao is better than in Pingqiao. The natural sandstone micromodels are made with sampled cores.Using the micromod els,the displacement experiments of oil and water have been done. Experimental results indicate that oil displacement efficiency of the Chang6 reservoir in Wang yao (40.34%) is higher than in Pingqiao (30.48%). The difference of pore structu re, especially the difference of heterogeneity of pore structure is the reason that leads to the great difference of oil displacement efficiency between Wangyao and Pingqiao.
2000, 18(2): 290-296.
Abstract:
The paper have studied the characteristics of organic geochimestry of Low er Cambrian and relavant mineralization of Lead-Zinc ore deposits in western Hu nan and eastern Guizhou province.The lower Cambrian is located at the passive co ntinental margin of Yangtze landmass in southeast,and divided into three units f rom lower to upper,i.e.,Niutitang Formation,Balong Formation and Qingxudong Form ation,which belong to basin,shelf and ramp to margin reef-band facies of carbon ate platform respectively.Algal limestone,grey-dark muddy limestone and overlyin g oolite limestone are host rocks of Huayuan MVT Lead-Zinc ore deposits in Qingx udong Formation. There are three beds richin organic matter:black shale in lower part of Ni utitang Formation,zebra muddy limestone in lower part and grey-dark muddy limes ton in middle part of Qingxudong Formation,and the black shale is much higher (75%) than other beds (0.2%～0.4%).On the basis of the GC-MS of organic matter t racts and Rock-Eval Py,Py-GC analysis,their characteristics of normal paraffin i s higher carbon number range,single peak at the back,higher carbon number of mai n peak (27～31),weak odd-even predominance,and Pr/Ph＜1，but the charact eristics of biomarker of sterane and terpane are different between them.Ischoles tane is predominant in sterane of black shale(C29 is main(=34.33%),C29 αββ/ααα=2.18) and in grey-dark muddy limestone,cholestane is predominant (C29=42.2%,C29αββ/ααα=0.42).Tricycline terpane is predomenant in terpane of black shale(65.65%),Tm/Ts=1.14,and in grey-dark muddy limestone,ho pane is predominant(=66.2%),Tm/Ts=1.22.Above mentioned characteristics suggest t hat the precursor origin of organic matter among all beds is blue algal and bact eria in Cambrian sea,and deposited on the reduction to weakly redaction environm ents.The evolution level of organic matter is different among them,they have pas sed oil-window and the black shale is higher than other,but it is still not beyo nd the end stage of evolution. Some data evidence that the evolution level of altered grey-dark muddy limestone is not only related to diagenisis but also to hot ore-forming fluid.Therefore,they can result in obvious change of group composits,biomarker,pyrolysis T[ WTBZ〗maxand pyrolysis parameters.In massive muddy limestone,chloroform bit umen “A”=0.004%,saturated hydrocarbon=11.80%～41.1%，aromatic hydrocarbon=15.0 7% ～5.45%,asphaltene=31.00%～50.94%,Zn＜0.1%,but in interbedded rocks,Zn＞1.0%, chloroform bitumen “A”increased to 0.0112%,saturated hydrocarbon rise to 42.18 %～57.06%,aromatic hydrocarbon to 9.7%～21.47%,and asphaltene decrease to 7.36% ～14.55%,pyrolysis Tmaxfrom massive rock's 397℃ increase to interbedded rock's 510℃,and with increase of mineralization there occur the decrease in free hydrocarbon (S1),pyrolysis hydrocarbon (S2),hydrogen index (HI),oxygen index (OI) and hydrocarbon index (S1/TOC) of grey-dark muddy lime stone,All these suggest that there are close relationship between the organic co mposition and mineralization,and some organic composition may be directly precipitate during mineralization.
The paper have studied the characteristics of organic geochimestry of Low er Cambrian and relavant mineralization of Lead-Zinc ore deposits in western Hu nan and eastern Guizhou province.The lower Cambrian is located at the passive co ntinental margin of Yangtze landmass in southeast,and divided into three units f rom lower to upper,i.e.,Niutitang Formation,Balong Formation and Qingxudong Form ation,which belong to basin,shelf and ramp to margin reef-band facies of carbon ate platform respectively.Algal limestone,grey-dark muddy limestone and overlyin g oolite limestone are host rocks of Huayuan MVT Lead-Zinc ore deposits in Qingx udong Formation. There are three beds richin organic matter:black shale in lower part of Ni utitang Formation,zebra muddy limestone in lower part and grey-dark muddy limes ton in middle part of Qingxudong Formation,and the black shale is much higher (75%) than other beds (0.2%～0.4%).On the basis of the GC-MS of organic matter t racts and Rock-Eval Py,Py-GC analysis,their characteristics of normal paraffin i s higher carbon number range,single peak at the back,higher carbon number of mai n peak (27～31),weak odd-even predominance,and Pr/Ph＜1，but the charact eristics of biomarker of sterane and terpane are different between them.Ischoles tane is predominant in sterane of black shale(C29 is main(=34.33%),C29 αββ/ααα=2.18) and in grey-dark muddy limestone,cholestane is predominant (C29=42.2%,C29αββ/ααα=0.42).Tricycline terpane is predomenant in terpane of black shale(65.65%),Tm/Ts=1.14,and in grey-dark muddy limestone,ho pane is predominant(=66.2%),Tm/Ts=1.22.Above mentioned characteristics suggest t hat the precursor origin of organic matter among all beds is blue algal and bact eria in Cambrian sea,and deposited on the reduction to weakly redaction environm ents.The evolution level of organic matter is different among them,they have pas sed oil-window and the black shale is higher than other,but it is still not beyo nd the end stage of evolution. Some data evidence that the evolution level of altered grey-dark muddy limestone is not only related to diagenisis but also to hot ore-forming fluid.Therefore,they can result in obvious change of group composits,biomarker,pyrolysis T[ WTBZ〗maxand pyrolysis parameters.In massive muddy limestone,chloroform bit umen “A”=0.004%,saturated hydrocarbon=11.80%～41.1%，aromatic hydrocarbon=15.0 7% ～5.45%,asphaltene=31.00%～50.94%,Zn＜0.1%,but in interbedded rocks,Zn＞1.0%, chloroform bitumen “A”increased to 0.0112%,saturated hydrocarbon rise to 42.18 %～57.06%,aromatic hydrocarbon to 9.7%～21.47%,and asphaltene decrease to 7.36% ～14.55%,pyrolysis Tmaxfrom massive rock's 397℃ increase to interbedded rock's 510℃,and with increase of mineralization there occur the decrease in free hydrocarbon (S1),pyrolysis hydrocarbon (S2),hydrogen index (HI),oxygen index (OI) and hydrocarbon index (S1/TOC) of grey-dark muddy lime stone,All these suggest that there are close relationship between the organic co mposition and mineralization,and some organic composition may be directly precipitate during mineralization.
2000, 18(2): 302-309.
Abstract:
The Yaha negative inversion fault belt,which include main Yaha fault,Ya N o.1 fault and Ya No.2 fault,is located at the north uplift of Tarim basin. The fault belt is the boundary between the north Tarim uplift and Kuche depression.The main Yaha fault,elongating more than 200 km.is a listric fault that trends NE E and dipps southward,and the dip angle of the fault plane is steep in the shall ow strata and become flat in the deep strata.Ya No.1 fault,dipping northward and elongating 35 km,is on the south of main Yaha fault.Ya No.2 fault, dipping nort h ward and elongating about 38 km,is on the south of main Yaba fault and Ya No.1 f ault.Ya No.1 and No.2 faults are also negative inversion faults,controlling"grab en-type"fault-blocks with main Yaha fault.Yaha fault belt is developed along pre -existing basement faults or weak zones.The evolution of the fault belts has the characteristics of thrustion in the early phase(pre-Cretaceous)and negative in version in the late stage(Cretaceous-Tertiary). The characteristics of geomety,kinematics,main inversion phase and hydreocarbonc o ntrolling of Yaha negative inversion fault belt,north Tarim uplift,are discussed in this paper according to the analysis of sequence thickness,displacement-dist ance plot,inflection point,null point and fault growth index.The point of change from thrusting to negative inverstion faulting in the displacement-distance plo t is the inflection point which represents the main inversion phase.And the poi nt of transformation from net compression to net extension is the null point.The inflection point of displacement-distance plot of main Yaha fault is at the bot tom of Lower Cretaceous,indicating that the negative inversion of main Yaha faul t began at the initial Early Cretaceous.The main negative inversion phase is at the Early Cretaceous,henceforth the negative inversion weakens gradually.The sec ondary inversion phases exist in the late Cretaceous-Paleogene,Suwiyi and Kanchu n epoch of Miocene.Fault growth index of main Yaha fault in the main inversion p hase of Lower Cretaceous is about 1.44～1.54.And the growth index in the seconda ry inversion phase is about 1.25～1.28.The negative inversion terminates at the Kanchun epoch of Miocene and Kuche epoch of Pliocene. The inflection point of displacement-distance plot of Ya No.1 fault is at the bottom of Suwiyi Formation of Miocene,indicating that the main inversion phase of the fault is at the Suwiyi epoch of Miocene,and the growth index of the fault at this time is about 1.1～1.69. The inflection point of displacement-distance plot of Ya No.2 fault is at the bottom of Upper Cretaceous-Lower Paleogene,indicating that the main inversion phas e of the fault is at the Late Cretaceous-Paleogene,and the growth index of the f ault at this time is about 1.1～1.18. A series of local structures.including fault-blocks,fault-anticlines and buried- h ill-drapes,are developed along Yaha fault belts.The formation of these structure s has a rerationship to negative inversion of the fault belt at the late Yanshan and Himalayan.The Yaha fault belt has the excellent hydrocarbon accumulation con ditions because of matched time of main inversion,trap formation,petroleum migra tion and accumulation.
The Yaha negative inversion fault belt,which include main Yaha fault,Ya N o.1 fault and Ya No.2 fault,is located at the north uplift of Tarim basin. The fault belt is the boundary between the north Tarim uplift and Kuche depression.The main Yaha fault,elongating more than 200 km.is a listric fault that trends NE E and dipps southward,and the dip angle of the fault plane is steep in the shall ow strata and become flat in the deep strata.Ya No.1 fault,dipping northward and elongating 35 km,is on the south of main Yaha fault.Ya No.2 fault, dipping nort h ward and elongating about 38 km,is on the south of main Yaba fault and Ya No.1 f ault.Ya No.1 and No.2 faults are also negative inversion faults,controlling"grab en-type"fault-blocks with main Yaha fault.Yaha fault belt is developed along pre -existing basement faults or weak zones.The evolution of the fault belts has the characteristics of thrustion in the early phase(pre-Cretaceous)and negative in version in the late stage(Cretaceous-Tertiary). The characteristics of geomety,kinematics,main inversion phase and hydreocarbonc o ntrolling of Yaha negative inversion fault belt,north Tarim uplift,are discussed in this paper according to the analysis of sequence thickness,displacement-dist ance plot,inflection point,null point and fault growth index.The point of change from thrusting to negative inverstion faulting in the displacement-distance plo t is the inflection point which represents the main inversion phase.And the poi nt of transformation from net compression to net extension is the null point.The inflection point of displacement-distance plot of main Yaha fault is at the bot tom of Lower Cretaceous,indicating that the negative inversion of main Yaha faul t began at the initial Early Cretaceous.The main negative inversion phase is at the Early Cretaceous,henceforth the negative inversion weakens gradually.The sec ondary inversion phases exist in the late Cretaceous-Paleogene,Suwiyi and Kanchu n epoch of Miocene.Fault growth index of main Yaha fault in the main inversion p hase of Lower Cretaceous is about 1.44～1.54.And the growth index in the seconda ry inversion phase is about 1.25～1.28.The negative inversion terminates at the Kanchun epoch of Miocene and Kuche epoch of Pliocene. The inflection point of displacement-distance plot of Ya No.1 fault is at the bottom of Suwiyi Formation of Miocene,indicating that the main inversion phase of the fault is at the Suwiyi epoch of Miocene,and the growth index of the fault at this time is about 1.1～1.69. The inflection point of displacement-distance plot of Ya No.2 fault is at the bottom of Upper Cretaceous-Lower Paleogene,indicating that the main inversion phas e of the fault is at the Late Cretaceous-Paleogene,and the growth index of the f ault at this time is about 1.1～1.18. A series of local structures.including fault-blocks,fault-anticlines and buried- h ill-drapes,are developed along Yaha fault belts.The formation of these structure s has a rerationship to negative inversion of the fault belt at the late Yanshan and Himalayan.The Yaha fault belt has the excellent hydrocarbon accumulation con ditions because of matched time of main inversion,trap formation,petroleum migra tion and accumulation.
2000, 18(2): 314-318.
Abstract:
It is considered that the structures control the sediment of gas-oil bearing basins and migration and accumulation and the heat is the main energy of formin g hydrocarbons on the traditional oil-gas geology. Recently, more and more geolo gical and geo-chemical datum show that structural activity is emphasized on mech anochemistral function for organic matter directly generating hydrocarbon during forming hydrocarbon. Then, We simulated mechanochemistral function generating h ydrocarbon to different kinds of low mature organic source matters by a new meth od on systemically analyzing high-molecular mechanochemistral function and givin g basic mechanochemistral characteristics in order to attest mechanical energy s tructural activity generating to mechanochemistral function on forming hydrocarb on. And the result shows, under low temperature shear stress. The sapropelic mat ters apparently presented transformation from non-hydrocarbon to hydrocarbon and total hydrocarbon ratio of samples simulated is clearly added. The humic matter s took on the transformation not only from non-hydrocarbon and bituman to total hydrocarbon in soluble organic matters but also from large molecule to small mol ecule. It shows that the energy for organic matters generating hydrocarbon large ly derived from mechanical energy and the mechanochemistral function is one of t he mechanisms in organic matters early forming hydrocarbon.
It is considered that the structures control the sediment of gas-oil bearing basins and migration and accumulation and the heat is the main energy of formin g hydrocarbons on the traditional oil-gas geology. Recently, more and more geolo gical and geo-chemical datum show that structural activity is emphasized on mech anochemistral function for organic matter directly generating hydrocarbon during forming hydrocarbon. Then, We simulated mechanochemistral function generating h ydrocarbon to different kinds of low mature organic source matters by a new meth od on systemically analyzing high-molecular mechanochemistral function and givin g basic mechanochemistral characteristics in order to attest mechanical energy s tructural activity generating to mechanochemistral function on forming hydrocarb on. And the result shows, under low temperature shear stress. The sapropelic mat ters apparently presented transformation from non-hydrocarbon to hydrocarbon and total hydrocarbon ratio of samples simulated is clearly added. The humic matter s took on the transformation not only from non-hydrocarbon and bituman to total hydrocarbon in soluble organic matters but also from large molecule to small mol ecule. It shows that the energy for organic matters generating hydrocarbon large ly derived from mechanical energy and the mechanochemistral function is one of t he mechanisms in organic matters early forming hydrocarbon.
2000, 18(2): 324-326.
Abstract:
Production crude oils are analyzed by geofina hydrocarbon meter(GHM).The oils come from different stages in the process of water expelling simulation ex periment. In addition, the change rule of crude oil components is studied. and the internal relations between crude oil components and production degrees are also researched. The experiments indicate that a regular connection is formed between production degree of crude oil and the PV number of fluid.The carbon number range or the peak carbon number of normal alkanes in crude oils shift behi nd and the light/heavy hydrocarbons ratio exists decreasing direction along with the increase of production degree. The another conclusion is proved by experim ent that some isoprenoid alkane molecules are easier to expel from reservoir than the normal alkane molecules of close carbon number because of their column st ructure in space. Therefore, this investigation has practice significance in res earching expelled mechanics from microcosmic points of view and increasing production ratio of crude oils.
Production crude oils are analyzed by geofina hydrocarbon meter(GHM).The oils come from different stages in the process of water expelling simulation ex periment. In addition, the change rule of crude oil components is studied. and the internal relations between crude oil components and production degrees are also researched. The experiments indicate that a regular connection is formed between production degree of crude oil and the PV number of fluid.The carbon number range or the peak carbon number of normal alkanes in crude oils shift behi nd and the light/heavy hydrocarbons ratio exists decreasing direction along with the increase of production degree. The another conclusion is proved by experim ent that some isoprenoid alkane molecules are easier to expel from reservoir than the normal alkane molecules of close carbon number because of their column st ructure in space. Therefore, this investigation has practice significance in res earching expelled mechanics from microcosmic points of view and increasing production ratio of crude oils.
2000, 18(2): 172-179.
Abstract:
Based on key sequence boundary, sedimentary system tracts, in conjunc tion with bio-stratigraphy, sequence stratigraphy during the Devonian in the Yo ujiang Basin has been studied in detail. 17 3rd-order sequences have been recog nized for the first time, 7 sequences in the Lower, 5 sequences in the Middle an d 5 sequences in the Upper Devonian, including 10 Ⅰ-type sequences and 7 Ⅱ-t ype sequences, representing 17 3rd-order relative sea level changes. Moreover, sequences in different sedimentary backgruonds have been correlated and then cor responding seqence stratigaphic framework has also been established. This paper demonstrated that sequence internal architecture and genetic framework within va rious sedimentary facies zones are obviously different, but they can be correlat ed and traced because of the same control factor-relative sea level changes. The Devonian transgression in this area extended from south to north overlappe d in the formation of the transgression-type sequences. These sequences were co ntrolled by sea-level change and tectonic activities. At least three 2nd-order rising sea level stages have been distinguished. During the basin evolution, the late stage of Early and Middle Devonian and the early of Late Devonian correspo nd to the eustatic change of sea level. During these periods the tectonic, volca nism and sedimentary differentiation might be very strong. Devonian basin can be subdivided into stability and riftplatform. the former distributes in Lochkovian, Pragian, Eifelian, Frasnian and Famenian, and the latter in Emrian and Givetian. In the stability age, sequences can be correlated one by one. But in tectonic area period, sequences are clearly different. The r esult of research shows that Devonian sequence of stabilized platform area is ma inly controlled by sea ieel change and tectonic movement of the globe or the r egion, and the sequence of the rift trough in the platform is controlled by the basement tectonics of the basin and the episodic subsidence.
Based on key sequence boundary, sedimentary system tracts, in conjunc tion with bio-stratigraphy, sequence stratigraphy during the Devonian in the Yo ujiang Basin has been studied in detail. 17 3rd-order sequences have been recog nized for the first time, 7 sequences in the Lower, 5 sequences in the Middle an d 5 sequences in the Upper Devonian, including 10 Ⅰ-type sequences and 7 Ⅱ-t ype sequences, representing 17 3rd-order relative sea level changes. Moreover, sequences in different sedimentary backgruonds have been correlated and then cor responding seqence stratigaphic framework has also been established. This paper demonstrated that sequence internal architecture and genetic framework within va rious sedimentary facies zones are obviously different, but they can be correlat ed and traced because of the same control factor-relative sea level changes. The Devonian transgression in this area extended from south to north overlappe d in the formation of the transgression-type sequences. These sequences were co ntrolled by sea-level change and tectonic activities. At least three 2nd-order rising sea level stages have been distinguished. During the basin evolution, the late stage of Early and Middle Devonian and the early of Late Devonian correspo nd to the eustatic change of sea level. During these periods the tectonic, volca nism and sedimentary differentiation might be very strong. Devonian basin can be subdivided into stability and riftplatform. the former distributes in Lochkovian, Pragian, Eifelian, Frasnian and Famenian, and the latter in Emrian and Givetian. In the stability age, sequences can be correlated one by one. But in tectonic area period, sequences are clearly different. The r esult of research shows that Devonian sequence of stabilized platform area is ma inly controlled by sea ieel change and tectonic movement of the globe or the r egion, and the sequence of the rift trough in the platform is controlled by the basement tectonics of the basin and the episodic subsidence.
2000, 18(2): 190-197.
Abstract:
The Carboniferous strata extensively distributes in Sichuan,Yunnan,Guizhou and Guangxi provinces. It has the characteristicse of clear stratigraphic division and correlation, plentiful sediment types and better outcrops. It is suitable to have the sequence stratigraphy research in these areas. This paper has focused on the accurate researches of the exposure sequence str atigraphy of the Carboniferous strata based on the detailed sedimentological stu dy and accurate stratigraphic division and correlation of the Carboniferous stra ta in Sichuan,Yunnan,Guizhou and Guangxi provinces with the aid of the theor y and studying means of the exposure sequence stratigraphy. Sequences are divide d mainly by the characteristics of the key boundary surfaces,regional correla tion,sedimentary facies sequence changes,parasequence stacking patterns,facies a ssemblage and sedimentary geochemistry. It has expounded in detail the outcrop signs of the sequence division and various boundary surfaces. The Carboniferous strata in the study area are divided into 10 third-scale se quences, which are named from sequence 1 to 10, with the upper series of Carboni ferous strata having 5 sequences and the lower series also. In the lower series of Carboniferous strata, Yanguan stage are composed of sequence 1 to 2, and Data ng stage from sequences 3 to 5. In the upper series, Huashiban stage are compos ed of sequence 6 and Dala stage of sequence 7, and Maping stage from sequence 8 to 10. According to the features of the bottom boundary surface, 10 sequences ar e classified into two sorts of sequences, which are type Ⅰ sequence (S1,S3,S6,S9,S10) and type Ⅱ sequence(S2,S4,S5,S7,S8). The bottom boundary surfaces of type Ⅰ sequence all have clear signs including the strong paleokarst,the different thickness eluvial facies,the strata disconti nutity,the immense changes of sedimentary patterns and traits,the regional rev ival of river,the disappearence and abrupt changes of organism evolution and the huge and sudden alternation of carbon,oxygen and strontium isotope values. On t he other hand, the bottom boundary surfaces of type Ⅱ sequence are character iz ed by the transient exposure,the weak erosion and the lithoface texture transfor mation. So it is discerned more difficultly than the bottom boundary surface of type Ⅰ sequence. This paper also has expounded in detail the sedimentary features of the first transgressive surfaces and condensed sections of sequences in the different sedi mentary environments and basins. It has summarized the sedimentary characteristi cs of the different system tracts in the different facies and basins. On the ba sis of these researches, this paper has probed the sequence correlation in the different sedimentary facies and basins from the ways of the sequence number s,boundary surface traits and system tract structures and has founded the time -space pattern diagram of the Carboniferous sequence strata in the study area.
The Carboniferous strata extensively distributes in Sichuan,Yunnan,Guizhou and Guangxi provinces. It has the characteristicse of clear stratigraphic division and correlation, plentiful sediment types and better outcrops. It is suitable to have the sequence stratigraphy research in these areas. This paper has focused on the accurate researches of the exposure sequence str atigraphy of the Carboniferous strata based on the detailed sedimentological stu dy and accurate stratigraphic division and correlation of the Carboniferous stra ta in Sichuan,Yunnan,Guizhou and Guangxi provinces with the aid of the theor y and studying means of the exposure sequence stratigraphy. Sequences are divide d mainly by the characteristics of the key boundary surfaces,regional correla tion,sedimentary facies sequence changes,parasequence stacking patterns,facies a ssemblage and sedimentary geochemistry. It has expounded in detail the outcrop signs of the sequence division and various boundary surfaces. The Carboniferous strata in the study area are divided into 10 third-scale se quences, which are named from sequence 1 to 10, with the upper series of Carboni ferous strata having 5 sequences and the lower series also. In the lower series of Carboniferous strata, Yanguan stage are composed of sequence 1 to 2, and Data ng stage from sequences 3 to 5. In the upper series, Huashiban stage are compos ed of sequence 6 and Dala stage of sequence 7, and Maping stage from sequence 8 to 10. According to the features of the bottom boundary surface, 10 sequences ar e classified into two sorts of sequences, which are type Ⅰ sequence (S1,S3,S6,S9,S10) and type Ⅱ sequence(S2,S4,S5,S7,S8). The bottom boundary surfaces of type Ⅰ sequence all have clear signs including the strong paleokarst,the different thickness eluvial facies,the strata disconti nutity,the immense changes of sedimentary patterns and traits,the regional rev ival of river,the disappearence and abrupt changes of organism evolution and the huge and sudden alternation of carbon,oxygen and strontium isotope values. On t he other hand, the bottom boundary surfaces of type Ⅱ sequence are character iz ed by the transient exposure,the weak erosion and the lithoface texture transfor mation. So it is discerned more difficultly than the bottom boundary surface of type Ⅰ sequence. This paper also has expounded in detail the sedimentary features of the first transgressive surfaces and condensed sections of sequences in the different sedi mentary environments and basins. It has summarized the sedimentary characteristi cs of the different system tracts in the different facies and basins. On the ba sis of these researches, this paper has probed the sequence correlation in the different sedimentary facies and basins from the ways of the sequence number s,boundary surface traits and system tract structures and has founded the time -space pattern diagram of the Carboniferous sequence strata in the study area.
2000, 18(2): 205-209.
Abstract:
Based on the research of marine facies sequence stratigraphy in Youjiang basin area, 44 sequences can be distingui shed uhich can be divided into 6 ultrasequences,and they respond well to the e volution of the Youjiang ba sin as well as to basin-mountain transformation during the Devonian to the ear ly Triassic. The surface of sequence boundary is a negative sedimentary record w h ich depends on the physical property of the sediments below and above the bounda ries and/or on the different sedimentary structure. Every sequence surface of bo undary represents each sedimentation and tectonic movements in the sedimentary b a sin because the tectonic movement can enhance or weaken the marks for sequence b oundaries. According to the sequence stratigraphy and basin evolution in Youjia ng basin, 4 genetic sequence boundaries can be reconstructed during the Devonian to the early Triassic, which suggest different basin evolution stage. They are uplift erosional sequence unconformity, transgressive onlap sequence unconformit y, the exposed sequence unconformity and the orogenic erosional sequence uncon formity. Uplift erosional sequence unconformity is caused by tectonic uplifting or by s e a-level falling. This unconformity represents isochronous surface of boundary w hi ch show the new basin genesis or basin-basin transformation. Transgressive onla p sequence unconformity is a transgressive surface which show synchronism bewtee n tectonic subsidence of basin and sea-level rising. The exposed sequence u nc onformity take place in the steady tectonism stage. The orogenic erosional uncon f ormity means that the sequence boundaries may be highlighted by tectonism in the course of the transformation of the basin systems into the orogenic processes.
Based on the research of marine facies sequence stratigraphy in Youjiang basin area, 44 sequences can be distingui shed uhich can be divided into 6 ultrasequences,and they respond well to the e volution of the Youjiang ba sin as well as to basin-mountain transformation during the Devonian to the ear ly Triassic. The surface of sequence boundary is a negative sedimentary record w h ich depends on the physical property of the sediments below and above the bounda ries and/or on the different sedimentary structure. Every sequence surface of bo undary represents each sedimentation and tectonic movements in the sedimentary b a sin because the tectonic movement can enhance or weaken the marks for sequence b oundaries. According to the sequence stratigraphy and basin evolution in Youjia ng basin, 4 genetic sequence boundaries can be reconstructed during the Devonian to the early Triassic, which suggest different basin evolution stage. They are uplift erosional sequence unconformity, transgressive onlap sequence unconformit y, the exposed sequence unconformity and the orogenic erosional sequence uncon formity. Uplift erosional sequence unconformity is caused by tectonic uplifting or by s e a-level falling. This unconformity represents isochronous surface of boundary w hi ch show the new basin genesis or basin-basin transformation. Transgressive onla p sequence unconformity is a transgressive surface which show synchronism bewtee n tectonic subsidence of basin and sea-level rising. The exposed sequence u nc onformity take place in the steady tectonism stage. The orogenic erosional uncon f ormity means that the sequence boundaries may be highlighted by tectonism in the course of the transformation of the basin systems into the orogenic processes.
2000, 18(2): 215-220.
Abstract:
Based on the sequence stratigraphy, in conjunction with the res ult of petroleum exploration, the correlation model of sequence stratigraphic framewor k and oil & gas source-reservoir-cap rock association has been established. Em phasi zed on Nanpanjiang depression and Shiwandashan basin, this paper deals with the genetic type and distribution pattern of source-reservoir-cap rock strata with in different hierarchies of sequence stratigraphic frameworks in the Youjiang Basin, and then discusses on their genesis and development model. Various sequence frameworks in different genetic basins contain different hydr ocarbon prospects. In general, transgressive system tracts (TST), condensed sec t ion (CS), highstand system tracts (HST) and lowstand system tracts (LST) of inte rplatform basin, deep-water basin are generally impo rtant source rocks and significant cap rocks, and coal-bearing carbonate formations of hi ghstand system tract in cratonic basin and carbonate platform. Highstand system tracts and lowstand system tracts in cratonic basin and carbon ate platform are important reservoins,and karst reservoir is developped along s equence boundary.Reservoirs maimly include all kinds of favoura ble sandbodies within different system tracts:①basin floor and slope fans, del ta front, alluvial fan, channel sandbodies, progradation complex, shoal-bioher m -reef complex, calcareous and mixed clastic turbidites within lowstand system tract; ②sandbodies of barrier beach, shoal, estuary, tide-controlled delta, fandelt a, turbidity fan, lag sediment, bioherm-reef complex, pyroclast turbidite withi n transgressiue system tract; ③river and wave dominated deltatic sandbodies, a lluvial-fan-channel sandbodies, fandelta, turbidity fan, terrigenous and car bonate shales, bioherm-reef complex, calcareous-clastic beach-bioherm-reef complex, calcareous clastic turbidite and dolostone within highstand system tra ct; and ④paleokarst reservoir dominated by sequence boundary.
Based on the sequence stratigraphy, in conjunction with the res ult of petroleum exploration, the correlation model of sequence stratigraphic framewor k and oil & gas source-reservoir-cap rock association has been established. Em phasi zed on Nanpanjiang depression and Shiwandashan basin, this paper deals with the genetic type and distribution pattern of source-reservoir-cap rock strata with in different hierarchies of sequence stratigraphic frameworks in the Youjiang Basin, and then discusses on their genesis and development model. Various sequence frameworks in different genetic basins contain different hydr ocarbon prospects. In general, transgressive system tracts (TST), condensed sec t ion (CS), highstand system tracts (HST) and lowstand system tracts (LST) of inte rplatform basin, deep-water basin are generally impo rtant source rocks and significant cap rocks, and coal-bearing carbonate formations of hi ghstand system tract in cratonic basin and carbonate platform. Highstand system tracts and lowstand system tracts in cratonic basin and carbon ate platform are important reservoins,and karst reservoir is developped along s equence boundary.Reservoirs maimly include all kinds of favoura ble sandbodies within different system tracts:①basin floor and slope fans, del ta front, alluvial fan, channel sandbodies, progradation complex, shoal-bioher m -reef complex, calcareous and mixed clastic turbidites within lowstand system tract; ②sandbodies of barrier beach, shoal, estuary, tide-controlled delta, fandelt a, turbidity fan, lag sediment, bioherm-reef complex, pyroclast turbidite withi n transgressiue system tract; ③river and wave dominated deltatic sandbodies, a lluvial-fan-channel sandbodies, fandelta, turbidity fan, terrigenous and car bonate shales, bioherm-reef complex, calcareous-clastic beach-bioherm-reef complex, calcareous clastic turbidite and dolostone within highstand system tra ct; and ④paleokarst reservoir dominated by sequence boundary.
2000, 18(2): 227-232.
Abstract:
High-sinuosity river are low-sinuosity river aye two chief meandering r ivers.Taking Jingjiang river for example,the article expounds sedimentary unit and chara cteristic of two different kinds of meandering river with comparing sedimentolog y me thod.Because of difference in river nature,flow and boundary condition,①up and down stream of Jing Jiang take the shape of point bar,but the disparities exist in shape,distributive spot,maturity,grain size,sedimentary structure,s e ction texture,micro-morphologic unit.②many river islands exist in up an d down stream of Jingjiang river,but their cause of formation,scale,evolution nat ure an d sedimentary texture are different,③crevasse splay is only formed in up strea m of Jingjiang river and development degree is within equality two banks.The dow n stream of Jingjiang river and development degree is within equality two banks.The dow n stream of Jingjiang river don't exist crevasse splay.④ox-bow lakes exist only in d own st ream of Jingjiang river and northern bank is mainly distributive spot of ox-bow lake.
High-sinuosity river are low-sinuosity river aye two chief meandering r ivers.Taking Jingjiang river for example,the article expounds sedimentary unit and chara cteristic of two different kinds of meandering river with comparing sedimentolog y me thod.Because of difference in river nature,flow and boundary condition,①up and down stream of Jing Jiang take the shape of point bar,but the disparities exist in shape,distributive spot,maturity,grain size,sedimentary structure,s e ction texture,micro-morphologic unit.②many river islands exist in up an d down stream of Jingjiang river,but their cause of formation,scale,evolution nat ure an d sedimentary texture are different,③crevasse splay is only formed in up strea m of Jingjiang river and development degree is within equality two banks.The dow n stream of Jingjiang river and development degree is within equality two banks.The dow n stream of Jingjiang river don't exist crevasse splay.④ox-bow lakes exist only in d own st ream of Jingjiang river and northern bank is mainly distributive spot of ox-bow lake.
2000, 18(2): 241-247.
Abstract:
This paper analyses the forming process of point bar,hydrodynamic regime and sc oure-and-fill mechanism of flood event,and combines the vertical sequence of p oint bar,the type of lateral accretion body(LAB),lithofacies,granularity, porosity and permeability,sets up the tranverse and vertical depositional model and the sedimentary stack of LAB in point bar,3-D architecture of point bar, and the heterogeneous model. At a stage in a flood event,the velocity of rich-sand helical bottom flow from concave bank to convex bank decreasing makes that depositional grain thins,beddi ng form changes and bedding scale becomes smaller,tranverse lithofacies variatio n (eg.pebbly Crs.Grn.sand→parallel-bedding Med.Grn.sand→trough cross-bedding fine Grn.sand→ripple cross-lamination silt)forms。At different stage in a flo odevent,different hydrodynamic regime forms different lithofacies in vertical,th ese can constitute 4 types of rhythm:I.Fining-upwards rhythm(FUR)of Rising-flo od Scouring(RS)and Falling-flood Depositing(FD);Ⅱ.Coarsening-upwards rhythm(C UR) of RD & FS;Ⅲ.CUR of RD & FUR of FD;Ⅳ.no or little sediments of RS & FS.The transverse and vertical models of LAB constitute the depositiomal model of LAB. It is the product in whole process of a flood event. Many wedge-form and lunate-shape LABs deposited in different flood events late rally stack in imbricated shape and constitute point bar.This is the sedimentary stack of LABs.and The vertical succession of PI2 point bar in well GJ-45 con sists of 8 LABs,there is 5-15cm thickness lateral accretion mudstone between LA Bs. According to above forming process and mechanism of point bar,fivefold hierarch y bounding surface(BS) and solid body between BSs are divided in a point bar san dstone body (PBSB),sets up 3-D architecture of point bar which reveals geometri c external form,the controlling frame,hierarchy,rule and spatial characteristic of inter nal structure in sandstone-body and heterogeneity of point bar.This me thod of heterogeneous study is better than mathematical method.5th BS controls r elatively independent oil-water moving unit;4th and 3th BS controls the frame o f very thin lateral accretion mudstone and sandstone,the sedimentary stack of L ABs is the key to study spatial distribution permeability of in PBSB;2th BS and depositional model of LAB are the key to study spatial distribution permeabili ty of in LAB.
This paper analyses the forming process of point bar,hydrodynamic regime and sc oure-and-fill mechanism of flood event,and combines the vertical sequence of p oint bar,the type of lateral accretion body(LAB),lithofacies,granularity, porosity and permeability,sets up the tranverse and vertical depositional model and the sedimentary stack of LAB in point bar,3-D architecture of point bar, and the heterogeneous model. At a stage in a flood event,the velocity of rich-sand helical bottom flow from concave bank to convex bank decreasing makes that depositional grain thins,beddi ng form changes and bedding scale becomes smaller,tranverse lithofacies variatio n (eg.pebbly Crs.Grn.sand→parallel-bedding Med.Grn.sand→trough cross-bedding fine Grn.sand→ripple cross-lamination silt)forms。At different stage in a flo odevent,different hydrodynamic regime forms different lithofacies in vertical,th ese can constitute 4 types of rhythm:I.Fining-upwards rhythm(FUR)of Rising-flo od Scouring(RS)and Falling-flood Depositing(FD);Ⅱ.Coarsening-upwards rhythm(C UR) of RD & FS;Ⅲ.CUR of RD & FUR of FD;Ⅳ.no or little sediments of RS & FS.The transverse and vertical models of LAB constitute the depositiomal model of LAB. It is the product in whole process of a flood event. Many wedge-form and lunate-shape LABs deposited in different flood events late rally stack in imbricated shape and constitute point bar.This is the sedimentary stack of LABs.and The vertical succession of PI2 point bar in well GJ-45 con sists of 8 LABs,there is 5-15cm thickness lateral accretion mudstone between LA Bs. According to above forming process and mechanism of point bar,fivefold hierarch y bounding surface(BS) and solid body between BSs are divided in a point bar san dstone body (PBSB),sets up 3-D architecture of point bar which reveals geometri c external form,the controlling frame,hierarchy,rule and spatial characteristic of inter nal structure in sandstone-body and heterogeneity of point bar.This me thod of heterogeneous study is better than mathematical method.5th BS controls r elatively independent oil-water moving unit;4th and 3th BS controls the frame o f very thin lateral accretion mudstone and sandstone,the sedimentary stack of L ABs is the key to study spatial distribution permeability of in PBSB;2th BS and depositional model of LAB are the key to study spatial distribution permeabili ty of in LAB.
2000, 18(2): 253-258.
Abstract:
There are 14 layers of sedimentogenic conglomerates in Late Paleozoic strata fro m Daqingshan coalfield, in which 8 layers of conglomerates belong to Late Carbon iferous strata and 6 layers belong to Permian strata. Based on the outcrop measu rement, petrologic and minerologic determination and the other analysis to these conglomerates, it and that almost all conglomerates in Late Carbonifero us strata are stable single-component conglomerates, the content of quartz sands tone and flint pebbles is higher than 93%. The biggest flat faces of all pebbles dip to the south and dip angle is between 5°-10°. The coarse quartz sandston e associated with conglomerates develop big low angle double directional cross b edding, and the environmental discriminant parameters show that the conglomerate s in Late Carboniferous was deposited in coastal environment. The pebbles in Permian are mainly complex component, especially the pebbles of two conglomerat e layers formed in the late time of Earlier-Permian and early time of Late-Permi an are as many as 15 kinds which are mainly that of medium-acidic volcanics and volcaniclastic rock, and also contain more pebbles of metamorphic rock and mediu m-acidic intrusive rock. The characteristics of all the conglomerate layers show that the conglomerates of Permian are the products of river deposit. The sedime ntary conglomerates in Late Paleozoic from Daqingshan coalfield was tightly rela ted to the rising of northern orogenic zone and deposited in foreland basin.
There are 14 layers of sedimentogenic conglomerates in Late Paleozoic strata fro m Daqingshan coalfield, in which 8 layers of conglomerates belong to Late Carbon iferous strata and 6 layers belong to Permian strata. Based on the outcrop measu rement, petrologic and minerologic determination and the other analysis to these conglomerates, it and that almost all conglomerates in Late Carbonifero us strata are stable single-component conglomerates, the content of quartz sands tone and flint pebbles is higher than 93%. The biggest flat faces of all pebbles dip to the south and dip angle is between 5°-10°. The coarse quartz sandston e associated with conglomerates develop big low angle double directional cross b edding, and the environmental discriminant parameters show that the conglomerate s in Late Carboniferous was deposited in coastal environment. The pebbles in Permian are mainly complex component, especially the pebbles of two conglomerat e layers formed in the late time of Earlier-Permian and early time of Late-Permi an are as many as 15 kinds which are mainly that of medium-acidic volcanics and volcaniclastic rock, and also contain more pebbles of metamorphic rock and mediu m-acidic intrusive rock. The characteristics of all the conglomerate layers show that the conglomerates of Permian are the products of river deposit. The sedime ntary conglomerates in Late Paleozoic from Daqingshan coalfield was tightly rela ted to the rising of northern orogenic zone and deposited in foreland basin.
2000, 18(2): 263-267,272.
Abstract:
Gangdong oil field,claiming a history of 30 years, locates in Huanghua depressio n of Gulf of Bohai basin. Reservoirs of the oil field are to the fluvial facies deposits, and is extremely heterogeneous and layered. The reservoir mostly consists of small striped channel deposits interbedded with flood-plain. It is v ery difficult to correlate reservoirs. High-resolution sequence stratigraphic an alysis can serve directly to high-resolution stratigraphic framework. Fir st fault block, the second area of Gangdong oil fields is selected as the study area. Based on the principle of base-level cycles, two scales of stratigraphic c ycles (short-and intermediate-term) are recognized through the combination of cores and logs data in the area. The short-term stratigraphic cycles, which may be not relate to base-level cycle, are the result of channel avulsion autocyclic process, Five type of channel avulsion auto-cycles are identified. The intermed iate-term stratigraphic cycles correspond to change of base-level cycle, and dif ferent types of the short-term cycles occur in different position of the interme diate-term base-level cycle. The same microfacies has different architecture in different position of the base-level cycle. The base-level cycle directly contro ll the channel reservoir geometry, Within an intermediate-term base-level cycl e, during periods of low accommodation, channel deposits is mostly lateral agg radation, and channel reservoirs superpose and connecte each other. As accomm odation increased, channel reservoirs become progressively isolated within flood -plain mudstone. According to that characterization, high-resolution sequence st ratigraphic framework has been established based on intermediate-term base-level cycle, and using the high-resolution correlation to identify reservoir continui ty and heterogeneities that could divide reservoirs into fluid flow compartments and are the most important factots in controlling the rates and pathways of flu id flow through reservoir.
Gangdong oil field,claiming a history of 30 years, locates in Huanghua depressio n of Gulf of Bohai basin. Reservoirs of the oil field are to the fluvial facies deposits, and is extremely heterogeneous and layered. The reservoir mostly consists of small striped channel deposits interbedded with flood-plain. It is v ery difficult to correlate reservoirs. High-resolution sequence stratigraphic an alysis can serve directly to high-resolution stratigraphic framework. Fir st fault block, the second area of Gangdong oil fields is selected as the study area. Based on the principle of base-level cycles, two scales of stratigraphic c ycles (short-and intermediate-term) are recognized through the combination of cores and logs data in the area. The short-term stratigraphic cycles, which may be not relate to base-level cycle, are the result of channel avulsion autocyclic process, Five type of channel avulsion auto-cycles are identified. The intermed iate-term stratigraphic cycles correspond to change of base-level cycle, and dif ferent types of the short-term cycles occur in different position of the interme diate-term base-level cycle. The same microfacies has different architecture in different position of the base-level cycle. The base-level cycle directly contro ll the channel reservoir geometry, Within an intermediate-term base-level cycl e, during periods of low accommodation, channel deposits is mostly lateral agg radation, and channel reservoirs superpose and connecte each other. As accomm odation increased, channel reservoirs become progressively isolated within flood -plain mudstone. According to that characterization, high-resolution sequence st ratigraphic framework has been established based on intermediate-term base-level cycle, and using the high-resolution correlation to identify reservoir continui ty and heterogeneities that could divide reservoirs into fluid flow compartments and are the most important factots in controlling the rates and pathways of flu id flow through reservoir.
2000, 18(2): 273-278,289.
Abstract:
The regional groundwater flow in Taibei depression of Tu-Ha basin is the gravit y-induced cross-formational groundwater flow. There are two gravity-induced cross-formational groundwater flow systems in Taibei depression. One is in Sheng bei sag and the other is in Qiudong and Xiaocaohu sags. The groundwater in the groundwater systems flows from north to south. The recharge area of the groundwater is in the Bogeda mountainous terrain north Taibei depression and the drainage is in the north border of the central faulted zone in Taibei depression. There is ve rti cally good hydraulic connection among the different formation waters. Since the Jurassic period，there have been three different stages of the groundwater hydro dynamic evolution. The early stage (Jurassic period) is the stage of the compacted groundwater flow，in which the compacted flow caused the large-scale oil -gas reservoir to distribute within effective source rocks around the sags of the generating hydrocarbon. In the middle stage(Cretaceous Period-Miocene Epoch)，the groundwater flow is the compacted and gravity-induced flow and it had adjusted the reservoir formed in the early stage of hydrodynamic evolution. The groundwat er caused oil and gas to accumulate in the mixed zone of the compacted and gravi ty-induced groundwater flows. In the late stage(Pliocene Epoch to now)，the grou nd water flow is driven by topography and it had the interface of oil/water，the oil saturation of reservoir and the oil-gas-bearing formation and location chang edsignificantly along regional groundwater flow.
The regional groundwater flow in Taibei depression of Tu-Ha basin is the gravit y-induced cross-formational groundwater flow. There are two gravity-induced cross-formational groundwater flow systems in Taibei depression. One is in Sheng bei sag and the other is in Qiudong and Xiaocaohu sags. The groundwater in the groundwater systems flows from north to south. The recharge area of the groundwater is in the Bogeda mountainous terrain north Taibei depression and the drainage is in the north border of the central faulted zone in Taibei depression. There is ve rti cally good hydraulic connection among the different formation waters. Since the Jurassic period，there have been three different stages of the groundwater hydro dynamic evolution. The early stage (Jurassic period) is the stage of the compacted groundwater flow，in which the compacted flow caused the large-scale oil -gas reservoir to distribute within effective source rocks around the sags of the generating hydrocarbon. In the middle stage(Cretaceous Period-Miocene Epoch)，the groundwater flow is the compacted and gravity-induced flow and it had adjusted the reservoir formed in the early stage of hydrodynamic evolution. The groundwat er caused oil and gas to accumulate in the mixed zone of the compacted and gravi ty-induced groundwater flows. In the late stage(Pliocene Epoch to now)，the grou nd water flow is driven by topography and it had the interface of oil/water，the oil saturation of reservoir and the oil-gas-bearing formation and location chang edsignificantly along regional groundwater flow.
2000, 18(2): 284-289.
Abstract:
The comparison of sedimentary geochemistry for mud areas on the East China Sea continental shelf (ECSCS) was carried out based on the contents of elements of surface sediments and concentrations of total suspended sediments (TSS) in the seawater from mud areas and their ambient sand areas. The results show that the processes of sedimentary geochemistry of different mud areas on ECSCS are very different. The surface sediments from the Zhejiang Coastal Mud Area (ZCMA) occupy high contents of Fe, Mn, Zn and low contents of Na, Sr, Al and Ca. The geoch emical characters of surface sediments from ZCMA have a very close correspondence to those of Changjiang (Yangtze River) sediments, indicating that almost all s ources of sediments in ZCMA are from modern Changjiang discharge sediments in ad dition to alittle bit biogenic sediments. The modern Changjiang sediments to th e sea are deposited in the Zhejiang Coast because of the obstruction of Taiwan W arm Current. Whereas, the surface sediments from the Southwestern Cheju Island M ud Area (SCIMA) are characterized with high contents of Na, Sr, relative highco ntents of Al, Ca and low contents of Fe, Mn, Zn. The geochemical characters of s urface sediments from SCIMA have a good relation to those of Huanghe (Yell ow River) source. But there are somewhat mixed characters including biogenic and other source sediments in SCIMA. It is indicated that the main source of sedime nts in SCIMA is from fine-grained sediments of Huanghe source. The Huanghe sourc e sediments are chiefly from the resuspended sediments in the old Huanghe estuar y located in the Northern Jiangsu province. Then, the Huanghai (Yellow Sea) Coas tal Current transports the fine-grained sediments from old Huanghe estuary to the SCIMA. Therefore, the controlling factors for the sedimentary geochemistry of different mud areas on ECSCS are the current system in the East China Sea and the source of sediments. Especially, the Taiwan Warm Current plays a key role to the sedimentary geochemistry division between ZCMA and SCIMA in the study area.
The comparison of sedimentary geochemistry for mud areas on the East China Sea continental shelf (ECSCS) was carried out based on the contents of elements of surface sediments and concentrations of total suspended sediments (TSS) in the seawater from mud areas and their ambient sand areas. The results show that the processes of sedimentary geochemistry of different mud areas on ECSCS are very different. The surface sediments from the Zhejiang Coastal Mud Area (ZCMA) occupy high contents of Fe, Mn, Zn and low contents of Na, Sr, Al and Ca. The geoch emical characters of surface sediments from ZCMA have a very close correspondence to those of Changjiang (Yangtze River) sediments, indicating that almost all s ources of sediments in ZCMA are from modern Changjiang discharge sediments in ad dition to alittle bit biogenic sediments. The modern Changjiang sediments to th e sea are deposited in the Zhejiang Coast because of the obstruction of Taiwan W arm Current. Whereas, the surface sediments from the Southwestern Cheju Island M ud Area (SCIMA) are characterized with high contents of Na, Sr, relative highco ntents of Al, Ca and low contents of Fe, Mn, Zn. The geochemical characters of s urface sediments from SCIMA have a good relation to those of Huanghe (Yell ow River) source. But there are somewhat mixed characters including biogenic and other source sediments in SCIMA. It is indicated that the main source of sedime nts in SCIMA is from fine-grained sediments of Huanghe source. The Huanghe sourc e sediments are chiefly from the resuspended sediments in the old Huanghe estuar y located in the Northern Jiangsu province. Then, the Huanghai (Yellow Sea) Coas tal Current transports the fine-grained sediments from old Huanghe estuary to the SCIMA. Therefore, the controlling factors for the sedimentary geochemistry of different mud areas on ECSCS are the current system in the East China Sea and the source of sediments. Especially, the Taiwan Warm Current plays a key role to the sedimentary geochemistry division between ZCMA and SCIMA in the study area.
2000, 18(2): 297-301.
Abstract:
The Jurassic of the northern Qaidam basin is widely recognized as the nonmar ine sediments, and interpreted as alluvial-delta and lacustrine depositional system. The depositional sequence of the Tianshuigou Fm. within the lower Jura ss ic mainly composed of the alluvial system at the base and lower and the deep lac ustrine system in the upper. Geochemical and optical analyses were undertaken on the minor cyclothems, a progradationally coarsening-and shallowing-upward paraseque nce (cycle) within the major lacustrine deposits in which Type III land-plant derived kerogen is overwhelming. The total organic carbon cont ent of the fine-grainned lithology increases upwards through the parasequence and is positively correlated with silt content, presumably due to the hydrodynam ic equivalence and common alluvial source of phytoclasts and silt particles. The section is marginally mature ( about 0.57% vitrinite reflectance). The distri bution of pyrite and siderite is apparently related to sediment accumulation rate,with frequent appearance of siderite in the lower part of the para sequence. The lacustri ne flooding surface at the base of the parasequence is overlain by black shale, and thought to have been terminated by an abrupt and major rise in relative lac ustrine level,which may be perhaps the result of tectonically driven changes in subsidence.
The Jurassic of the northern Qaidam basin is widely recognized as the nonmar ine sediments, and interpreted as alluvial-delta and lacustrine depositional system. The depositional sequence of the Tianshuigou Fm. within the lower Jura ss ic mainly composed of the alluvial system at the base and lower and the deep lac ustrine system in the upper. Geochemical and optical analyses were undertaken on the minor cyclothems, a progradationally coarsening-and shallowing-upward paraseque nce (cycle) within the major lacustrine deposits in which Type III land-plant derived kerogen is overwhelming. The total organic carbon cont ent of the fine-grainned lithology increases upwards through the parasequence and is positively correlated with silt content, presumably due to the hydrodynam ic equivalence and common alluvial source of phytoclasts and silt particles. The section is marginally mature ( about 0.57% vitrinite reflectance). The distri bution of pyrite and siderite is apparently related to sediment accumulation rate,with frequent appearance of siderite in the lower part of the para sequence. The lacustri ne flooding surface at the base of the parasequence is overlain by black shale, and thought to have been terminated by an abrupt and major rise in relative lac ustrine level,which may be perhaps the result of tectonically driven changes in subsidence.
2000, 18(2): 310-313,318.
Abstract:
The combined gas chromatograph-isotope ratio mass spectrometry(GC-IRMS) was employed to measure compound-specific isotope ratio of hopanes in five peat samples from Guangdong province and 3 oil samples from northwestern margin of Junggar basin. It is shown from the result that the isotopic ratio of carbon for hopanes in peats are -21.7‰～-34.4‰,which are relatively enriched in13C compared to that of the lacustrine Messel shale, Green River shale and the oils of Jun ggar basin, indicating that biological bacteria sourced hopanes of peats are di fferent from that of lacustrine shales and oils. It is also found from the result that the hopanes with different carbon number and configuration in peat XLI ha ve significant difference in isotopic composition of carbon, e.g. the δ13C values of C27β hopane is -23.2‰,whereas the δ13C value of C29β β hopanes is -34. 4‰. This demonstrates that various biological bacteria sourced hopanes may be present in the same depositional environment. As C29βα, C29ββ, C 31βα hopanes found in peats are isotopically lighter than that of their C29αβ, C 30αβ co unterparts, it is suggested that C29βα, C29ββ, C31βα hop anes are sourced f rom methanotrophic bacteria and that C29αβ, C30αβ hopans are sou rced from che moautotrophic bacteria. The aim to measure carbon isotopic composition of hopane s in oils of the northwestern margin, Junggar basin in this study is to explore δ13C values of hopanes for oils correlation because that the oils are pr odu ced from various strata in the northwestern margin area and that the strata are developed with many faults. As a result, it was found that δ13C values of oils fr om the west of northwestern margin area are quit different from that of the east of northwestern margin, i.e. δ13C value of hopanes for oils in the west of no rthwestern margin are -39.9‰～-53.4‰, whereas δ13C values of hopanes fo r oils in the east of northwestern margin are -33.1‰～-31‰.Since isotopic ratio of h opanes may be enriched in13C with increase of their thermal maturation, it is s uggested from this study that the age of rock sourced oils in the east of northwestern margin should be older than that sourced oils in the west of nort hwestern margin, i.e. the oils from the east of northwestern margin may be sourc ed from Permian, whereas oils from the west of northwestern margin may be sourc ed from Triassic and Jurassic.
The combined gas chromatograph-isotope ratio mass spectrometry(GC-IRMS) was employed to measure compound-specific isotope ratio of hopanes in five peat samples from Guangdong province and 3 oil samples from northwestern margin of Junggar basin. It is shown from the result that the isotopic ratio of carbon for hopanes in peats are -21.7‰～-34.4‰,which are relatively enriched in13C compared to that of the lacustrine Messel shale, Green River shale and the oils of Jun ggar basin, indicating that biological bacteria sourced hopanes of peats are di fferent from that of lacustrine shales and oils. It is also found from the result that the hopanes with different carbon number and configuration in peat XLI ha ve significant difference in isotopic composition of carbon, e.g. the δ13C values of C27β hopane is -23.2‰,whereas the δ13C value of C29β β hopanes is -34. 4‰. This demonstrates that various biological bacteria sourced hopanes may be present in the same depositional environment. As C29βα, C29ββ, C 31βα hopanes found in peats are isotopically lighter than that of their C29αβ, C 30αβ co unterparts, it is suggested that C29βα, C29ββ, C31βα hop anes are sourced f rom methanotrophic bacteria and that C29αβ, C30αβ hopans are sou rced from che moautotrophic bacteria. The aim to measure carbon isotopic composition of hopane s in oils of the northwestern margin, Junggar basin in this study is to explore δ13C values of hopanes for oils correlation because that the oils are pr odu ced from various strata in the northwestern margin area and that the strata are developed with many faults. As a result, it was found that δ13C values of oils fr om the west of northwestern margin area are quit different from that of the east of northwestern margin, i.e. δ13C value of hopanes for oils in the west of no rthwestern margin are -39.9‰～-53.4‰, whereas δ13C values of hopanes fo r oils in the east of northwestern margin are -33.1‰～-31‰.Since isotopic ratio of h opanes may be enriched in13C with increase of their thermal maturation, it is s uggested from this study that the age of rock sourced oils in the east of northwestern margin should be older than that sourced oils in the west of nort hwestern margin, i.e. the oils from the east of northwestern margin may be sourc ed from Permian, whereas oils from the west of northwestern margin may be sourc ed from Triassic and Jurassic.
2000, 18(2): 319-323.
Abstract:
Nitrogen,like carbon and oxygen,is one of important elements in Organic matt er cor molecule In the oil an d gas-bearing rocks, with the maturation and formation of into hydrocarbon from organic matters, nitrogen is released into pore fluids to form NH+4 and interact s w ith diagenetic minerals(e.g.authigenic clay minerals). The most important mechan ism that is NH+4 substitutes for K+ in interlayer sites of clay minerals ( e.g. illite, ilite/smectite) and forms the NH4-bearing minerals. The significant ch anges of the geochemical properties of nitrogen have taken place during the diag enetic process. The concentrations of fixed-NH4 in the NH4-bearing minerals is closely related to maturation of organic matter and mig ration of hydrocarbon. The fixed-NH4 concentration of authigenic clay minerals increase gradually with the organic maturation. The diagenetic clay minerals al ong the hydrocarbon migration pathways were able to “catch” more NH+4 duri ng hydrocarbon migration and accumulation, and thus its fixed-NH4 concentration is higher than other places.By means of many studies of the nitrogen lithogeochem isty and its influenced factors during diagenesis and hydrocarbon formation, migrati on as well as accumulaton, it shows that the new and potential use of fixed-NH4 co ncentration as an indicator of organic maturity and hydrocarbon migration pathways.
Nitrogen,like carbon and oxygen,is one of important elements in Organic matt er cor molecule In the oil an d gas-bearing rocks, with the maturation and formation of into hydrocarbon from organic matters, nitrogen is released into pore fluids to form NH+4 and interact s w ith diagenetic minerals(e.g.authigenic clay minerals). The most important mechan ism that is NH+4 substitutes for K+ in interlayer sites of clay minerals ( e.g. illite, ilite/smectite) and forms the NH4-bearing minerals. The significant ch anges of the geochemical properties of nitrogen have taken place during the diag enetic process. The concentrations of fixed-NH4 in the NH4-bearing minerals is closely related to maturation of organic matter and mig ration of hydrocarbon. The fixed-NH4 concentration of authigenic clay minerals increase gradually with the organic maturation. The diagenetic clay minerals al ong the hydrocarbon migration pathways were able to “catch” more NH+4 duri ng hydrocarbon migration and accumulation, and thus its fixed-NH4 concentration is higher than other places.By means of many studies of the nitrogen lithogeochem isty and its influenced factors during diagenesis and hydrocarbon formation, migrati on as well as accumulaton, it shows that the new and potential use of fixed-NH4 co ncentration as an indicator of organic maturity and hydrocarbon migration pathways.
