1996 Vol. 14, No. 2
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Display Method:
1996, 14(2): 12-20.
Abstract:
The marine oils derived from Cambrian-Ordovician source rocks of Lower Palaeozoic al-ways contain low-middle wax in Tarim Basin. The kerogen of bower Palaeozoic marine strata are mainly composed of amorphous matter decomposed from bacteria and algae, and are high mature, There is a higher content of C+21n-alkanes in the pyrolysates by kerogen's PY-GC analysis, Associating with petroleum migration, we can conclude the genesis model of middle wax marine oils,in which the bacterium source in high maturity is a main factor, And the model breaks through the concept that the oils with higher wax are only derived from organic matters of high plants.
The marine oils derived from Cambrian-Ordovician source rocks of Lower Palaeozoic al-ways contain low-middle wax in Tarim Basin. The kerogen of bower Palaeozoic marine strata are mainly composed of amorphous matter decomposed from bacteria and algae, and are high mature, There is a higher content of C+21n-alkanes in the pyrolysates by kerogen's PY-GC analysis, Associating with petroleum migration, we can conclude the genesis model of middle wax marine oils,in which the bacterium source in high maturity is a main factor, And the model breaks through the concept that the oils with higher wax are only derived from organic matters of high plants.
1996, 14(2): 47-55.
Abstract:
Based on the analytical data of aromatics of the crude from dun 5 Well in Tarim basin,the oils of this well were thought to be in an excellent homogeneity,and there was the same source for oils from different parts of the reservoir. The Qun 5 Well oils are highly mature and are thought to be generated from the Cambrian一Ordovician carbonates which were formed in marine environment with a strongly reducing condition, A long一distance migration had oc- curred to the oils which were accumulated in Bachu formation of the lower Carboniferous.
Based on the analytical data of aromatics of the crude from dun 5 Well in Tarim basin,the oils of this well were thought to be in an excellent homogeneity,and there was the same source for oils from different parts of the reservoir. The Qun 5 Well oils are highly mature and are thought to be generated from the Cambrian一Ordovician carbonates which were formed in marine environment with a strongly reducing condition, A long一distance migration had oc- curred to the oils which were accumulated in Bachu formation of the lower Carboniferous.
1996, 14(2): 66-74.
Abstract:
The Pemian reefs in Ziyun County,Guizhou, are among the best developed reefs in South China. The horizon of these reefs ranges from the Middle Permian Maokun to the uppermost Permian Changxingian. Except the Upper Permian Wujiapingian coral biostromes, the main reef building organisms include calcisponges, hydrozoans, blyozoans, and the enerusting alga Archaeolithoporella. The facies difference is very distinct. Especially the Changxingian reef complex,including backreef skeletal sand facies, reefcore facies, forereef slope facies, and basin f acies, can be observed in a distance less than fi kilometers from north to south. Well de-veloped reefs exist in the highstand systems tracts of each depositional sequence. Relative changes of sealevel and paleoclimate are believed to be the fundamental control factors on the development of the reefs.
The Pemian reefs in Ziyun County,Guizhou, are among the best developed reefs in South China. The horizon of these reefs ranges from the Middle Permian Maokun to the uppermost Permian Changxingian. Except the Upper Permian Wujiapingian coral biostromes, the main reef building organisms include calcisponges, hydrozoans, blyozoans, and the enerusting alga Archaeolithoporella. The facies difference is very distinct. Especially the Changxingian reef complex,including backreef skeletal sand facies, reefcore facies, forereef slope facies, and basin f acies, can be observed in a distance less than fi kilometers from north to south. Well de-veloped reefs exist in the highstand systems tracts of each depositional sequence. Relative changes of sealevel and paleoclimate are believed to be the fundamental control factors on the development of the reefs.
1996, 14(2): 82-88.
Abstract:
Many sedimentary siliceous rock beds are found in Late Sinian to Late Paleozoic in Yangtze platform. It is difficult to clarify the origin and silicon sources of these siliceous rocks because of diagenetic changes,although some studies have been conducted on the rocks in dif-ferent aspects. However,silicon isotope of siliceous rocks is of fected little by diagenesis. It may be better to use silicon isotope to reflect the original sedimentary geochemical con-dition and silicon sources of siliceous rock,We here report 20 silicon isotope ratio results of siliceous rocks which deposited in differ-ent geological background. Combined with other geochemical features related to origin of siliceous rock,such as Al/(Al+Fe+Mn)and Fe/Ti,and features of bio一organism in the rocks, the silicon isotope results are compared and discussed. These results may provide a refe-pence for the application of silicon isotope in sedimentary siliceous rock study.
Many sedimentary siliceous rock beds are found in Late Sinian to Late Paleozoic in Yangtze platform. It is difficult to clarify the origin and silicon sources of these siliceous rocks because of diagenetic changes,although some studies have been conducted on the rocks in dif-ferent aspects. However,silicon isotope of siliceous rocks is of fected little by diagenesis. It may be better to use silicon isotope to reflect the original sedimentary geochemical con-dition and silicon sources of siliceous rock,We here report 20 silicon isotope ratio results of siliceous rocks which deposited in differ-ent geological background. Combined with other geochemical features related to origin of siliceous rock,such as Al/(Al+Fe+Mn)and Fe/Ti,and features of bio一organism in the rocks, the silicon isotope results are compared and discussed. These results may provide a refe-pence for the application of silicon isotope in sedimentary siliceous rock study.
1996, 14(2): 95-101.
Abstract:
Raoyang Sag is located in central part of Jizhong Depression, Bohaiwan basin. Since the discovery of "buried hill" carbonate hydrocarbon reservoir in 1975,overall regional petroleum exploration activities have been carried out. Eogene sandstone reservoirs followed the Yre-Mesozoic carbonates have become the new petroleum exploration targets.This paper has discussed the origin,type,vertical distribution of sandstone reservoir porosity in Eogene in Raoyang Sag. The evolution and vertical distribution of sandstone porosi-ty have been classified into 5 phase through mechanical and chemical diagenesis study:1)Shal-low buried(<2000 m) primary porosity phase,2)Mixed primary and dissoived secondary porosity phass(2000--2800 m),3)Pure dissolved secondary porosity phase ( 2800-4000m),4) Inter crystal residual and dissolved secondary porosity phase (4000-4599 m),and 5)Micro-fissure storage phase (>4500 m). Meanwhile the authors have quantitatively described and predicted the reservoir storage capacity in different porosity evolution stages.Now the discovered hydrocarbon accumulations in Eogene in Raoyang sag are concentrat-ed between 2000-3500 m interval. This study has discussed the existence possibilities of deep buried sandstone hydrocarbon reservoirs:1)Sufficient and abundant hydrocarbon sources.Depth of the maximum hydrocarbon expulsion of Eogene petroleum source rocks in Raoyan ranges from 3800 m to 5300 m,2 ) Deep buried sandstone reservoirs show 'the tendency of ab-normal pressure,which is favorable for the preservation of various origin porosity,3)Corelaboratory analysis data indicate that in deep burial domain,the sandstone reservoirs still pos-sess the storage capability of porosity value 5%15%and permeability value <0. O1一50X10-3.μm2. 4)In deep burial domain(>3800 m ) the content of illite and montmorillonite mixed一layer clay mineral in sandstone bodies has been extinct,but the shale in same burial do- main still posses illite and montmorillonte mixed-layer that has 12%montmorillonite layer,which may bring about the forming of subtle entrapment.
Raoyang Sag is located in central part of Jizhong Depression, Bohaiwan basin. Since the discovery of "buried hill" carbonate hydrocarbon reservoir in 1975,overall regional petroleum exploration activities have been carried out. Eogene sandstone reservoirs followed the Yre-Mesozoic carbonates have become the new petroleum exploration targets.This paper has discussed the origin,type,vertical distribution of sandstone reservoir porosity in Eogene in Raoyang Sag. The evolution and vertical distribution of sandstone porosi-ty have been classified into 5 phase through mechanical and chemical diagenesis study:1)Shal-low buried(<2000 m) primary porosity phase,2)Mixed primary and dissoived secondary porosity phass(2000--2800 m),3)Pure dissolved secondary porosity phase ( 2800-4000m),4) Inter crystal residual and dissolved secondary porosity phase (4000-4599 m),and 5)Micro-fissure storage phase (>4500 m). Meanwhile the authors have quantitatively described and predicted the reservoir storage capacity in different porosity evolution stages.Now the discovered hydrocarbon accumulations in Eogene in Raoyang sag are concentrat-ed between 2000-3500 m interval. This study has discussed the existence possibilities of deep buried sandstone hydrocarbon reservoirs:1)Sufficient and abundant hydrocarbon sources.Depth of the maximum hydrocarbon expulsion of Eogene petroleum source rocks in Raoyan ranges from 3800 m to 5300 m,2 ) Deep buried sandstone reservoirs show 'the tendency of ab-normal pressure,which is favorable for the preservation of various origin porosity,3)Corelaboratory analysis data indicate that in deep burial domain,the sandstone reservoirs still pos-sess the storage capability of porosity value 5%15%and permeability value <0. O1一50X10-3.μm2. 4)In deep burial domain(>3800 m ) the content of illite and montmorillonite mixed一layer clay mineral in sandstone bodies has been extinct,but the shale in same burial do- main still posses illite and montmorillonte mixed-layer that has 12%montmorillonite layer,which may bring about the forming of subtle entrapment.
1996, 14(2): 110-116.
Abstract:
The kinetic model of clay mineral transformation and is uses are studied in this paper. The model can be applied to:(1)Determination of paleoheat flux;(2) Modeing of diagenetic his-tory;(3) Predictation of the diagenetic stages of the formation in the region without drilling wells.With the increase of burial depth and temperature, clay mineral smectite in the formations transform into illite,which leads the smectite layers (5%)in the smectite/ illite mixed layers (I/S) become fewer and fewer. The transformation of smectite to illite obeys first一order ki-netics. 5% in I/S is a function of temperature and time,and the measured 5% in I/S is a comprehensive effect of temperacare and time during geological history, So the paleoheac fluX can be determined using mcasured S% in I/S, We derermined the palnoheat flux of Well Changcan一1 in geological history using this modelra. So the diagenetic history of scraca can be modals by computing S% in IIS dung geologi-cal history. We modeled diegcnelic history of Well Tangcan一1 in Yi一Shu Graben using mea-surcd S%in I/S as well as paleocemperacure and vitrinire refleccancc R%.The isogram of S% in I/S can be made on the base of modeing the burial history and thcrmal history of all the drieng wells and ficticious weds,then the diagenctic stage of the for-mation can be predicted, We diuided the diageaecic stage of Eb2 formarion in Tegyuan Fault-ed Basin,Yi一Shu Grabea using S% in I/S contour map and R%contour map.
The kinetic model of clay mineral transformation and is uses are studied in this paper. The model can be applied to:(1)Determination of paleoheat flux;(2) Modeing of diagenetic his-tory;(3) Predictation of the diagenetic stages of the formation in the region without drilling wells.With the increase of burial depth and temperature, clay mineral smectite in the formations transform into illite,which leads the smectite layers (5%)in the smectite/ illite mixed layers (I/S) become fewer and fewer. The transformation of smectite to illite obeys first一order ki-netics. 5% in I/S is a function of temperature and time,and the measured 5% in I/S is a comprehensive effect of temperacare and time during geological history, So the paleoheac fluX can be determined using mcasured S% in I/S, We derermined the palnoheat flux of Well Changcan一1 in geological history using this modelra. So the diagenetic history of scraca can be modals by computing S% in IIS dung geologi-cal history. We modeled diegcnelic history of Well Tangcan一1 in Yi一Shu Graben using mea-surcd S%in I/S as well as paleocemperacure and vitrinire refleccancc R%.The isogram of S% in I/S can be made on the base of modeing the burial history and thcrmal history of all the drieng wells and ficticious weds,then the diagenctic stage of the for-mation can be predicted, We diuided the diageaecic stage of Eb2 formarion in Tegyuan Fault-ed Basin,Yi一Shu Grabea using S% in I/S contour map and R%contour map.
1996, 14(2): 124-130.
Abstract:
Based on the study of sedimentary megafacies and subfacies made by former researchers,the authors have studied the automatic distinguishing of lithology and microfacies by grey clus-tering,which is the process of determining decisio一making matrix,white functio equations,cluster weight,and cluster coefficient. In this study,the second sandstone section in the third member of Qingshankou formation of ringtai area in Songliao Basin is taken as an example. First,parameters sensible to lithology such as lateral log (Rt ),sonic moveout (Ac),and natu-ral gammary (ER) and those sensible to microfacies, like thickness of sandstone, rnudstone,and the transitional rocks of these two and the sandstone pereentage,are chosen as the work-ing variables. Second,by studying 9 core holes that are representative to the fades change in Yingtal region,the varying ranges of the logging results to different lithosomes have been ob-tamed with respect to Rt,AC,and ER. The statistical thickness ranges of sandstone, mud-stone,and the transitional rocks and the perentage of sandstone have also been made. Finally,the logs of Rt,Ac,and ER in 60 holes are changed into numerical values by computer in each depth interval of 0. 2 m. And the automatic distinguishing of lithology and microfacies has heen conducted by grey clustering. Three different lithosomes such as sandstone,mudstone,and the transitional rocks (argillaceous sandstone,sandy mudstone ) can be recognized. The distinguishable microfacies by this method are braided river course,channel一mouth har,river island,and sheet bar. The results made by grey clustering are basically the same as those ob-tained by common geoloic analysis.
Based on the study of sedimentary megafacies and subfacies made by former researchers,the authors have studied the automatic distinguishing of lithology and microfacies by grey clus-tering,which is the process of determining decisio一making matrix,white functio equations,cluster weight,and cluster coefficient. In this study,the second sandstone section in the third member of Qingshankou formation of ringtai area in Songliao Basin is taken as an example. First,parameters sensible to lithology such as lateral log (Rt ),sonic moveout (Ac),and natu-ral gammary (ER) and those sensible to microfacies, like thickness of sandstone, rnudstone,and the transitional rocks of these two and the sandstone pereentage,are chosen as the work-ing variables. Second,by studying 9 core holes that are representative to the fades change in Yingtal region,the varying ranges of the logging results to different lithosomes have been ob-tamed with respect to Rt,AC,and ER. The statistical thickness ranges of sandstone, mud-stone,and the transitional rocks and the perentage of sandstone have also been made. Finally,the logs of Rt,Ac,and ER in 60 holes are changed into numerical values by computer in each depth interval of 0. 2 m. And the automatic distinguishing of lithology and microfacies has heen conducted by grey clustering. Three different lithosomes such as sandstone,mudstone,and the transitional rocks (argillaceous sandstone,sandy mudstone ) can be recognized. The distinguishable microfacies by this method are braided river course,channel一mouth har,river island,and sheet bar. The results made by grey clustering are basically the same as those ob-tained by common geoloic analysis.
1996, 14(2): 137-143.
Abstract:
Xinjiang is the largest arid emiarid saltforming region in China,its natural environment has a geographic character of "two basins surrounded by three mountains". Many fresh lake and salt lakes are distributed in this region. It is one of the four large salt lake distribution re-gions in China. There are snore than 100 salt lakes in the region with a area of about 10,655.99 Km2. According to the geological structure condition and natural geographic environment,five salt lake zones can be divided,l. e. Allay innermountain basin,Jungar Basin,Tianshan innermountain basins,Tarim Basin and Kunlun -Artun innermountain basins. There are Whale Lake with the altitude of 5000 m a. s. 1., and aydingkol Lake whose altitude is 155 m below the sea level and the famous salt lake playa一Lop Nur.The formation and evolution of salt lakes in Xinjiang have undwergone two stages non salt 一forming stage and salt一forming stage. There are three sedimentary types in the lacustrine deposits一elastic sediments,clay sediments and evaporate sediments. The elastic sediments represent the lacustrine sediments in the early non salt一forming stage of the salt lake forma-tion. Evaporate sediments is the lacustrine sediment in salt forming stage of salt lake forma-tion. In the evaporate sediments,there are about 38 kinds of salt minerals including carbon-ates, sulphates ,borates,chlorides such as potash and magnesium salts and nitrates .The ni-traces salt deposits is the characteristic salt deposits in salt lakes in Xinjiang.The salt一{arming stags。{salt lakes in Xinjiang began in late pleistocene一middle Holocene,14C 25 X 104-5,000 a B. P.,it can be taken as the f first salt一forming stags,salt deposits can only been found in Tarpon Pasin and Lop Nur, The second salt一forming stage starts f ram middle Holocene to prcscnt with the vast salt deposits formcd in the region.The depth of the salt deposits varies from 10 to 30 m;the scdiementary sediernentary speed in-creased f ram cast to west,from north to south, The sedimentary dif f erentiatian of potash magnesium salt and nitrate salt is not obvious, sedimentary sequence is very clear, and is charactcrised by simple and multi sedimentation sequences.
Xinjiang is the largest arid emiarid saltforming region in China,its natural environment has a geographic character of "two basins surrounded by three mountains". Many fresh lake and salt lakes are distributed in this region. It is one of the four large salt lake distribution re-gions in China. There are snore than 100 salt lakes in the region with a area of about 10,655.99 Km2. According to the geological structure condition and natural geographic environment,five salt lake zones can be divided,l. e. Allay innermountain basin,Jungar Basin,Tianshan innermountain basins,Tarim Basin and Kunlun -Artun innermountain basins. There are Whale Lake with the altitude of 5000 m a. s. 1., and aydingkol Lake whose altitude is 155 m below the sea level and the famous salt lake playa一Lop Nur.The formation and evolution of salt lakes in Xinjiang have undwergone two stages non salt 一forming stage and salt一forming stage. There are three sedimentary types in the lacustrine deposits一elastic sediments,clay sediments and evaporate sediments. The elastic sediments represent the lacustrine sediments in the early non salt一forming stage of the salt lake forma-tion. Evaporate sediments is the lacustrine sediment in salt forming stage of salt lake forma-tion. In the evaporate sediments,there are about 38 kinds of salt minerals including carbon-ates, sulphates ,borates,chlorides such as potash and magnesium salts and nitrates .The ni-traces salt deposits is the characteristic salt deposits in salt lakes in Xinjiang.The salt一{arming stags。{salt lakes in Xinjiang began in late pleistocene一middle Holocene,14C 25 X 104-5,000 a B. P.,it can be taken as the f first salt一forming stags,salt deposits can only been found in Tarpon Pasin and Lop Nur, The second salt一forming stage starts f ram middle Holocene to prcscnt with the vast salt deposits formcd in the region.The depth of the salt deposits varies from 10 to 30 m;the scdiementary sediernentary speed in-creased f ram cast to west,from north to south, The sedimentary dif f erentiatian of potash magnesium salt and nitrate salt is not obvious, sedimentary sequence is very clear, and is charactcrised by simple and multi sedimentation sequences.
1996, 14(2): 151-154.
Abstract:
More and more research results indicate that secondary pores of sandstone devclope during dissolution of silicate, especially aluminosilicate minerals, instead of carbonate cements. Decay boxylation of organic matter in the process of maturation increases the anion density of organic acid in pore water solution,and promotes the dissolution of aluminosilicate minerals. The essence of dissolution is mobility of aluminium. Based on experiments,this paper studied the organic-inorganic interaction, solubility of different minerals under the effect of organic acid,and pointed out the dynamics factor which influence the mobility of aluminium. The authors disscused the forming mechanism of secondary pores as well.
More and more research results indicate that secondary pores of sandstone devclope during dissolution of silicate, especially aluminosilicate minerals, instead of carbonate cements. Decay boxylation of organic matter in the process of maturation increases the anion density of organic acid in pore water solution,and promotes the dissolution of aluminosilicate minerals. The essence of dissolution is mobility of aluminium. Based on experiments,this paper studied the organic-inorganic interaction, solubility of different minerals under the effect of organic acid,and pointed out the dynamics factor which influence the mobility of aluminium. The authors disscused the forming mechanism of secondary pores as well.
1996, 14(2): 41-46.
Abstract:
Tarim hasin, which is located in the northwest area of China, is the largest intracratonic petroliferous basin in China. There are strong energy seismic waves intercalated between Tg5;Tg5 seismic reflecting layers (the Middle and Upper Ordovician) in the most seismic sections of southern Mangar Sag in the basin. The abnormal reflected waves are present not only in north一south sections,but also in west一east ones. Closed net tracing correlation can be conducted in Mangar area with a size of about 30,000 square kilometers, indicating that these geological interfaces do exist underground.Based on the analysis of seismic reflection characteristics, geodynamic aspects of this basin,and the theory about under current of deoCearl,it is considered that the Lower Paleo-zoic eroxional valley of Mangar Sag in Tarim basin was caused by the erosion truncation of un-der current of deep ocean. Dnder current of deep ocean is another kind of current of deep wa-ier besides turhidity one. "hhc under current may erode most area of continental rise,and trun-Fate deep gullet and even much older sediments. In the large erosional valley,it may be de-posited various kinds of sediments,including a small scale volcanic rock. Wells Tazh ong 31and 33,which take anomaly body as the drilling object,penetrated the formation (Tg5 wave group) of a deep water sediment of dark gray shale with interhedded thin fine sand and silt,and thin (only 10 miters)andesite. Mangar sag is one oI the most important hydrocarbon一bearing depressions in the basin,and recent一year一exploration has proved that Cambrian and Ordovician are the most important source rocks in cast Tarim basin. So the crosional valley is located at perspective position near the oil source. It is possible to form lithologic deposits. Bi-tuminous sand and oil tract have been shown from siliirian to Llpper Ordovician in wells Tazhong 31 and 33.and a little dense oil has been got in well Tazhong 31.Above all,petroleum geological conditions of the erosional valley are extremely supprior and it may become an important ob.lect of oil and gas exploration in Tarim basin.
Tarim hasin, which is located in the northwest area of China, is the largest intracratonic petroliferous basin in China. There are strong energy seismic waves intercalated between Tg5;Tg5 seismic reflecting layers (the Middle and Upper Ordovician) in the most seismic sections of southern Mangar Sag in the basin. The abnormal reflected waves are present not only in north一south sections,but also in west一east ones. Closed net tracing correlation can be conducted in Mangar area with a size of about 30,000 square kilometers, indicating that these geological interfaces do exist underground.Based on the analysis of seismic reflection characteristics, geodynamic aspects of this basin,and the theory about under current of deoCearl,it is considered that the Lower Paleo-zoic eroxional valley of Mangar Sag in Tarim basin was caused by the erosion truncation of un-der current of deep ocean. Dnder current of deep ocean is another kind of current of deep wa-ier besides turhidity one. "hhc under current may erode most area of continental rise,and trun-Fate deep gullet and even much older sediments. In the large erosional valley,it may be de-posited various kinds of sediments,including a small scale volcanic rock. Wells Tazh ong 31and 33,which take anomaly body as the drilling object,penetrated the formation (Tg5 wave group) of a deep water sediment of dark gray shale with interhedded thin fine sand and silt,and thin (only 10 miters)andesite. Mangar sag is one oI the most important hydrocarbon一bearing depressions in the basin,and recent一year一exploration has proved that Cambrian and Ordovician are the most important source rocks in cast Tarim basin. So the crosional valley is located at perspective position near the oil source. It is possible to form lithologic deposits. Bi-tuminous sand and oil tract have been shown from siliirian to Llpper Ordovician in wells Tazhong 31 and 33.and a little dense oil has been got in well Tazhong 31.Above all,petroleum geological conditions of the erosional valley are extremely supprior and it may become an important ob.lect of oil and gas exploration in Tarim basin.
1996, 14(2): 56-65.
Abstract:
Donghe Sandstone in Iarim Basin is a set of fine elastic reservoir rocks which deposited on the regional unconformity of early Hercy progeny. The origional basin where the Donghe Sandstone deposited is an intracratonic depressional basin. The basin with the characterstiris of shallow water and low slope was formed by the compression between the north and south plates.basin.The Tazhong area located in the east part is one of the components in the origional The sequence stratigraphy of longhe Sandstone within a depressional basin was depicted in this paper on the basis of study of seismic data,well logging 70-120 m,while and drilling materials. The thickness of Donghe Sandstone vanes between the maximum thickness is more than 165 m,it overlaped eastward and on the buried hill. The Donghe Sandstone is a standard type 1 sequence,including lowstand system tract,transgressive system tract and highstand system tract. It is analogous to the stratigraphyic unit formed by the third order cu-static fluctuation. Compared to the passive continental margin sequence stratigraphic model, the lowstand tract of this sequence only developed the fluvial deposits on land and lacked the early submarine fan,slope wedge,progradational complex and incised valleys which developed on shelf. There is no condensed sections in the transgressive system tract owing to the plenty of source materials and adjacent to the source area. Because of the transgression,the delta and estuary are the main depositional system which formed in the different locations and periods from the east to the west. The parasequences have the stackingg patterns from slight retrogra elation to aggradation. The highstand system tract which is mainly littoral depositional system is widely distributed,its parasequences have the progradational stacking pattern. During the late stage of highstand system tract,the infiiling of deposits and falling of sealevel lead to the basinward movement of estuary line and equlibrium point, which accounts for new land accom-mondation and developed the fluvial and alluvial deposits.
Donghe Sandstone in Iarim Basin is a set of fine elastic reservoir rocks which deposited on the regional unconformity of early Hercy progeny. The origional basin where the Donghe Sandstone deposited is an intracratonic depressional basin. The basin with the characterstiris of shallow water and low slope was formed by the compression between the north and south plates.basin.The Tazhong area located in the east part is one of the components in the origional The sequence stratigraphy of longhe Sandstone within a depressional basin was depicted in this paper on the basis of study of seismic data,well logging 70-120 m,while and drilling materials. The thickness of Donghe Sandstone vanes between the maximum thickness is more than 165 m,it overlaped eastward and on the buried hill. The Donghe Sandstone is a standard type 1 sequence,including lowstand system tract,transgressive system tract and highstand system tract. It is analogous to the stratigraphyic unit formed by the third order cu-static fluctuation. Compared to the passive continental margin sequence stratigraphic model, the lowstand tract of this sequence only developed the fluvial deposits on land and lacked the early submarine fan,slope wedge,progradational complex and incised valleys which developed on shelf. There is no condensed sections in the transgressive system tract owing to the plenty of source materials and adjacent to the source area. Because of the transgression,the delta and estuary are the main depositional system which formed in the different locations and periods from the east to the west. The parasequences have the stackingg patterns from slight retrogra elation to aggradation. The highstand system tract which is mainly littoral depositional system is widely distributed,its parasequences have the progradational stacking pattern. During the late stage of highstand system tract,the infiiling of deposits and falling of sealevel lead to the basinward movement of estuary line and equlibrium point, which accounts for new land accom-mondation and developed the fluvial and alluvial deposits.
1996, 14(2): 75-81.
Abstract:
Middle and late Devonian developed best in Guilin area. FromGivetian to Frasnian,reef and shoal Groped out in the different subfacies,moreover,in the different periods,the features of the reefal organisms are changable. Beginning in the late Devonian,stromatoporoids and corals were replaced by thriving algae which played an important role in reef communities. In Houshan,located in 5 km west of Guilin,however, the coral biostrome developed well besides algal-tromatoporoid reefs in out back一reef along inner platform margin. We seldom see such coral biostrome in the late Devonia strata. The coral biostrome are made of fasciculate Smithiphyllum guilinense packed by micrite. lts growth height can be up to 1 m,and it often exhibits low diversity. Other reefal organisms are algae and a few stromatoporoids,the attach-ing一reefal organisms are main brachiopods. Vertically,reefal sequences are composed of(1)cryptalgal micrite microfacies, (2)sand一sice algal intraclastic limestone,( 3 ) cryptalgal mi-crite with zebra structure microfacies and (4) coral biostrome microfacies. Laterally,the reef complex can be recognized with(1)back一reef subfacies,(2) reef flat and margin subfacies,(3) marginal fore一slope subfacies. According to inference from reefal organism,microfacies character and diagenesis of reef and relations with periphery environments,it is not barrier reef but a coral biostromc located the out back一reef nearer platform margin.
Middle and late Devonian developed best in Guilin area. FromGivetian to Frasnian,reef and shoal Groped out in the different subfacies,moreover,in the different periods,the features of the reefal organisms are changable. Beginning in the late Devonian,stromatoporoids and corals were replaced by thriving algae which played an important role in reef communities. In Houshan,located in 5 km west of Guilin,however, the coral biostrome developed well besides algal-tromatoporoid reefs in out back一reef along inner platform margin. We seldom see such coral biostrome in the late Devonia strata. The coral biostrome are made of fasciculate Smithiphyllum guilinense packed by micrite. lts growth height can be up to 1 m,and it often exhibits low diversity. Other reefal organisms are algae and a few stromatoporoids,the attach-ing一reefal organisms are main brachiopods. Vertically,reefal sequences are composed of(1)cryptalgal micrite microfacies, (2)sand一sice algal intraclastic limestone,( 3 ) cryptalgal mi-crite with zebra structure microfacies and (4) coral biostrome microfacies. Laterally,the reef complex can be recognized with(1)back一reef subfacies,(2) reef flat and margin subfacies,(3) marginal fore一slope subfacies. According to inference from reefal organism,microfacies character and diagenesis of reef and relations with periphery environments,it is not barrier reef but a coral biostromc located the out back一reef nearer platform margin.
1996, 14(2): 89-94.
Abstract:
Diffusion of molecule is Irec;uent in the nature,diffusion of natural gas is importarlt migra-tory mechanisms "The natural gas in reservoir may diffuse through caprock. The key to the quantitative evaluation of aealing ability of caprock is to make out the quantity of diffusion through caprock, The mechanism and the method of evaluate quantitativly the concentration seal of raprock arc put forward in this paper. T'he main caprocks in Qiong Dong Nan basin are studied using the method.
Diffusion of molecule is Irec;uent in the nature,diffusion of natural gas is importarlt migra-tory mechanisms "The natural gas in reservoir may diffuse through caprock. The key to the quantitative evaluation of aealing ability of caprock is to make out the quantity of diffusion through caprock, The mechanism and the method of evaluate quantitativly the concentration seal of raprock arc put forward in this paper. T'he main caprocks in Qiong Dong Nan basin are studied using the method.
1996, 14(2): 102-109.
Abstract:
In sandstone carbonate cementation is an important porosity reduction prcxess. Timing of carbonate precipitation and dissolution influences on development and evolution of porosity di-rectly. In Liaohe Basin Low一Tertiary sandstones carbonate cement average content is 10%,the maximum can be to 30% . The extent of carbonate cement distribution varies widely with present depth from 1300 m to 3700 m, and species of carbonate cement are calcite,ferriferous calcite,dolomite and ferriferous dolomite.The SEM,cathodoluminescene emission,oxyen and carbon stable isotopes,etc. analyti-cal methods are adopted in the research of the development mechanism of the carbonate cement in Liaohe Basin reservoir sandstones. Through research,the author indicates that(1)there were two episodes carbonate cementation took place ire sandstones,and the formation of car-bonate cement is related to the sandstone composition,evolution of organic matter and the characteristics of water;(2)there are different influence of two episodes carbonate cementa-tion nn porosity,and effect on the emplacement of hydrocarbon. Early episode precipitated carbonate cement caused pore loss and provided a condition for dissolution secondary porsity,and emplacement of hydrocarbon,late episode carbonate cement precipitation is related to CO2 generated by deoxidation of organic matter and repecipitated in the dissolution porosity,so that a large amount of porosity lost in the B episode of Mid一diagenesis.
In sandstone carbonate cementation is an important porosity reduction prcxess. Timing of carbonate precipitation and dissolution influences on development and evolution of porosity di-rectly. In Liaohe Basin Low一Tertiary sandstones carbonate cement average content is 10%,the maximum can be to 30% . The extent of carbonate cement distribution varies widely with present depth from 1300 m to 3700 m, and species of carbonate cement are calcite,ferriferous calcite,dolomite and ferriferous dolomite.The SEM,cathodoluminescene emission,oxyen and carbon stable isotopes,etc. analyti-cal methods are adopted in the research of the development mechanism of the carbonate cement in Liaohe Basin reservoir sandstones. Through research,the author indicates that(1)there were two episodes carbonate cementation took place ire sandstones,and the formation of car-bonate cement is related to the sandstone composition,evolution of organic matter and the characteristics of water;(2)there are different influence of two episodes carbonate cementa-tion nn porosity,and effect on the emplacement of hydrocarbon. Early episode precipitated carbonate cement caused pore loss and provided a condition for dissolution secondary porsity,and emplacement of hydrocarbon,late episode carbonate cement precipitation is related to CO2 generated by deoxidation of organic matter and repecipitated in the dissolution porosity,so that a large amount of porosity lost in the B episode of Mid一diagenesis.
1996, 14(2): 117-123.
Abstract:
Geological studies indicate that humic acids exsit in the total process of bauxite mineraliza-lion. In order to clarify the action of humic acids in the bauxite mineralization,in this paper in-lite clay rocks and aluminoferric rock are regarded as samples of mother rock of mineralization and red bauxixe respectively. Dissolution of Al203,SiO2 and Fe203 in the above rocks in the hu-mic acid-CO2一H2O systems of different conditions is studied experimentally. Significance of humic acid in the processes of desilication and deferridization forming red bauxite from mineral-izing mother rocks in the superfical oxidizing environment,and that of deferridization and de-silication forming white bauxite from red bauxite in swamp reducing environment are illustrat-silication forming white bauxite from red bauxite in swamp reducing environment are illustrat-ed. Importance of humic acids in mineralising gelatinous bausite is disscussed.
Geological studies indicate that humic acids exsit in the total process of bauxite mineraliza-lion. In order to clarify the action of humic acids in the bauxite mineralization,in this paper in-lite clay rocks and aluminoferric rock are regarded as samples of mother rock of mineralization and red bauxixe respectively. Dissolution of Al203,SiO2 and Fe203 in the above rocks in the hu-mic acid-CO2一H2O systems of different conditions is studied experimentally. Significance of humic acid in the processes of desilication and deferridization forming red bauxite from mineral-izing mother rocks in the superfical oxidizing environment,and that of deferridization and de-silication forming white bauxite from red bauxite in swamp reducing environment are illustrat-silication forming white bauxite from red bauxite in swamp reducing environment are illustrat-ed. Importance of humic acids in mineralising gelatinous bausite is disscussed.
1996, 14(2): 131-136.
Abstract:
Studied samples were collected from the Gannan marsh,southern Gansu Provice,where the climate is cold and moist,and organism consists mainly of herbs,for example,kobresia Humilis and Festuca sp. Peat distribution is wide and the mean peat thickness is about 4 m in this region. Sedimentary medium is acidic with a pH value of 5-5. 4. We here have studied chemical properties and geochemical significance of humic acids and kerogens by analyses of element and infrared spectra. Results show as follows:(1)The humic acids in the Gannan marsh sediment contain higher carbon content and lower hydro-gen and nitrogen contents as compared with those isolated from marine sediments. In-frayed spectra of humic acids in the studied samples show aromatic一rich and aliphatic一poor characteristics relative to those isolated from marine sediments. Those above indicate the features of land一marsh sedimentary enviroment. (2) With increasing depth,H/C,N/C and O/C atomic ratios and the carbohydrate content of infrared spectra for humic acids decrease,and the aromatic content of infrared spectra for humic acids increases,which shows an increase of condensation and aromaticity of humic acids with burial depth.(3) In the plot of O/C vs H/C atomic ratios,hmic acids and kerogens fall on the very im-mature region of maturation pathway of Type Ⅲ kerogen,while kerogens fall toward higher maturation than the corresponding humic acids. Infrared spectra show that kero-gens have a lower carbohydrate content and higher aromatic content relative to humic acids. Those above indicate the transformation of humic acids to kerogens,which under-ges condensation and aromaticity reactions.
Studied samples were collected from the Gannan marsh,southern Gansu Provice,where the climate is cold and moist,and organism consists mainly of herbs,for example,kobresia Humilis and Festuca sp. Peat distribution is wide and the mean peat thickness is about 4 m in this region. Sedimentary medium is acidic with a pH value of 5-5. 4. We here have studied chemical properties and geochemical significance of humic acids and kerogens by analyses of element and infrared spectra. Results show as follows:(1)The humic acids in the Gannan marsh sediment contain higher carbon content and lower hydro-gen and nitrogen contents as compared with those isolated from marine sediments. In-frayed spectra of humic acids in the studied samples show aromatic一rich and aliphatic一poor characteristics relative to those isolated from marine sediments. Those above indicate the features of land一marsh sedimentary enviroment. (2) With increasing depth,H/C,N/C and O/C atomic ratios and the carbohydrate content of infrared spectra for humic acids decrease,and the aromatic content of infrared spectra for humic acids increases,which shows an increase of condensation and aromaticity of humic acids with burial depth.(3) In the plot of O/C vs H/C atomic ratios,hmic acids and kerogens fall on the very im-mature region of maturation pathway of Type Ⅲ kerogen,while kerogens fall toward higher maturation than the corresponding humic acids. Infrared spectra show that kero-gens have a lower carbohydrate content and higher aromatic content relative to humic acids. Those above indicate the transformation of humic acids to kerogens,which under-ges condensation and aromaticity reactions.
1996, 14(2): 144-150.
Abstract:
The carbonate of Lower Permain in south Sichuan is typical fractures storage .and it in-eludes many types pores and fractures. No doubt fractures caused by structure activities take an important part in gas traps,but some other types of secondary pores and fractures are very significant too. Pried on the analysis of sediments and diagenesis of lower Permain series (slices aid cores of Weh Yang 52,Si 18 and Lai 4;sections of Gusong,Xinwen and Hongqiao in south Sichuan,the authors studied systematically all types of pores and f racturcs including structure Sichuan),the authors studied systemetically all types of pores and fractures including structure fissurcs,secondary corrosion cavities,cantract pores and crevices, unlaaded f lssures,regionah rifts, crush cracks (mcchanical,hydralic and oil一gas divulsional),separate fissures in layers,collapse brcccias clinks and seaming lines, etc.lay researching thcir mechanism and signif iw cance to fractures system,the gores ( general) causal classification of Lower Permain Series was presented,Although so many types pores exist,the gas reservior constructures in south Sichuan were formed in Xishan Activeity Period,so the combination of fractures by structures and cor-rusion cavities by structural period karstification and other pores formed in the same period is most important.
The carbonate of Lower Permain in south Sichuan is typical fractures storage .and it in-eludes many types pores and fractures. No doubt fractures caused by structure activities take an important part in gas traps,but some other types of secondary pores and fractures are very significant too. Pried on the analysis of sediments and diagenesis of lower Permain series (slices aid cores of Weh Yang 52,Si 18 and Lai 4;sections of Gusong,Xinwen and Hongqiao in south Sichuan,the authors studied systematically all types of pores and f racturcs including structure Sichuan),the authors studied systemetically all types of pores and fractures including structure fissurcs,secondary corrosion cavities,cantract pores and crevices, unlaaded f lssures,regionah rifts, crush cracks (mcchanical,hydralic and oil一gas divulsional),separate fissures in layers,collapse brcccias clinks and seaming lines, etc.lay researching thcir mechanism and signif iw cance to fractures system,the gores ( general) causal classification of Lower Permain Series was presented,Although so many types pores exist,the gas reservior constructures in south Sichuan were formed in Xishan Activeity Period,so the combination of fractures by structures and cor-rusion cavities by structural period karstification and other pores formed in the same period is most important.
1996, 14(2): 155-162.
Abstract:
The sedimentary characteristics and forming processes of sedimentary bed of Late GZuater-nary in the Zhujiang (Pearl) River Delta have been studied based on the data of drilling in this paper.The Zhujiang River Delta is located in subtropical zone of South China,where a great deal of mud and sand is accumulated in the Zhujiang River Estuary carried by the Xijiang,Uonjiang and Beijiang Rivers. Paleontology,sporo-pollen,clay mineral,geochemical and radiocarbon dating of Late Quaternary sediments be divided into Late Pleistocene Series in the Zhujiang River Delta have shown that strata may and Holocene Series and each may farther be divided in to three layers. Middle Late Pleistocene and Middle Holocene contain a lot of forminifera,marive osthacoda, brackish water diatoms, Corbula sp. and Ostrea sp. ,the average ratio of illite/kaolinite> 1.5 and that of Ca/(Ca+Fe) in sedimentary phosphate>0. 40,especially early Middle Holocene is characterized by containing an abundance of shallow sea fades micropaleon-tology,its compound differential degree is similar to that of prodelta in the Zhujiang River Es-tuary,the average ratio of illite/kaolinite is higher (2. 04) and that of Ca/
The sedimentary characteristics and forming processes of sedimentary bed of Late GZuater-nary in the Zhujiang (Pearl) River Delta have been studied based on the data of drilling in this paper.The Zhujiang River Delta is located in subtropical zone of South China,where a great deal of mud and sand is accumulated in the Zhujiang River Estuary carried by the Xijiang,Uonjiang and Beijiang Rivers. Paleontology,sporo-pollen,clay mineral,geochemical and radiocarbon dating of Late Quaternary sediments be divided into Late Pleistocene Series in the Zhujiang River Delta have shown that strata may and Holocene Series and each may farther be divided in to three layers. Middle Late Pleistocene and Middle Holocene contain a lot of forminifera,marive osthacoda, brackish water diatoms, Corbula sp. and Ostrea sp. ,the average ratio of illite/kaolinite> 1.5 and that of Ca/(Ca+Fe) in sedimentary phosphate>0. 40,especially early Middle Holocene is characterized by containing an abundance of shallow sea fades micropaleon-tology,its compound differential degree is similar to that of prodelta in the Zhujiang River Es-tuary,the average ratio of illite/kaolinite is higher (2. 04) and that of Ca/
