1995 Vol. 13, No. 1
column
Display Method:
1995, 13(1): 1-6.
Abstract:
Long-chain methyl and ethyl alkenones (C37-C40) containing 2- 4 double bonds have been detected in sediments from Qinghai lake cores (QE, Q-16A and QG).This is the first report of the long-chain ketones in lake sediments deposited under a variety of salinity conditions (Erhai,fresh water ;Qinghai lake, brackish; Gabal, saline).The C37 unsaturated ketone mixture consisted of the C37: 4, C37: 3 and C37: 2 isomers; The C38 unSaturated ketone mixture generally comPOsed the C38: 4,C38: 3 and C38: 2isomers, whereas the C39 unsaturated ketones were dominated in most cases by asingle C39: 3 isomer.A small numbe of samples in all the cores also contained low concentrations of the C40: 3 isomer.C37 and C39 ketones were recognized as methyl alkenones on the basis of their molecular ions, characteristic fragment ions at M-15, M-18, M-33, M-44 and M-58,and bAse peak at either m/z 43.81 or 95/96.The C38 and C40 isomers were recognized as ethyl alkenones from thediagnostic fragment ions at M-15, M-18, M-29,M-47,M-57 and M-72, and base peak at m/z 57.The C37-C40 alkenones are tentatively suggested to be derived from Chromulina sp in the lake.Differences in the abundance and unsaturated patterns of these alkenones in the sediments probably reflect compositional variations in the original algal input, and also reflect variations in salinity and temperature at time of deposition.With additional study, the alkenones in lacustrine environments may ultimately be useful for paleoclimate studies in manner analogous to that used in marine environmentS after additional calibration is made.
Long-chain methyl and ethyl alkenones (C37-C40) containing 2- 4 double bonds have been detected in sediments from Qinghai lake cores (QE, Q-16A and QG).This is the first report of the long-chain ketones in lake sediments deposited under a variety of salinity conditions (Erhai,fresh water ;Qinghai lake, brackish; Gabal, saline).The C37 unsaturated ketone mixture consisted of the C37: 4, C37: 3 and C37: 2 isomers; The C38 unSaturated ketone mixture generally comPOsed the C38: 4,C38: 3 and C38: 2isomers, whereas the C39 unsaturated ketones were dominated in most cases by asingle C39: 3 isomer.A small numbe of samples in all the cores also contained low concentrations of the C40: 3 isomer.C37 and C39 ketones were recognized as methyl alkenones on the basis of their molecular ions, characteristic fragment ions at M-15, M-18, M-33, M-44 and M-58,and bAse peak at either m/z 43.81 or 95/96.The C38 and C40 isomers were recognized as ethyl alkenones from thediagnostic fragment ions at M-15, M-18, M-29,M-47,M-57 and M-72, and base peak at m/z 57.The C37-C40 alkenones are tentatively suggested to be derived from Chromulina sp in the lake.Differences in the abundance and unsaturated patterns of these alkenones in the sediments probably reflect compositional variations in the original algal input, and also reflect variations in salinity and temperature at time of deposition.With additional study, the alkenones in lacustrine environments may ultimately be useful for paleoclimate studies in manner analogous to that used in marine environmentS after additional calibration is made.
1995, 13(1): 18-26.
Abstract:
Cycles of mid-cretuceous in southern Tibet are divided into four ciders by cyclic characteristics.The first order is shown in the up-and-down of sea level.The second order is represented by pelaeoproductivity and redo and five cycles of which periods (2Ma) obtained by the methed of AR-FFT corresPOnding in theoretically orbital parameter (2.03Ma) Caculated by Berser (1988) are due to rhythmical changes of polaeocurrent.The third cycle is represented by con pletS (Limestone / Marl and black shale / limestone ), and three im portan t periods of cycles are 43,52 and 92 thousand years respectively, which corresponds to the periods of obliquity and eccentricity and were origined from palaeoproduotivity and dilution by climatic variations which are resulted from the changes of orbital paameters.The fourth order cycle is represented by fine horizontal laminations caused by seasonal variations.
Cycles of mid-cretuceous in southern Tibet are divided into four ciders by cyclic characteristics.The first order is shown in the up-and-down of sea level.The second order is represented by pelaeoproductivity and redo and five cycles of which periods (2Ma) obtained by the methed of AR-FFT corresPOnding in theoretically orbital parameter (2.03Ma) Caculated by Berser (1988) are due to rhythmical changes of polaeocurrent.The third cycle is represented by con pletS (Limestone / Marl and black shale / limestone ), and three im portan t periods of cycles are 43,52 and 92 thousand years respectively, which corresponds to the periods of obliquity and eccentricity and were origined from palaeoproduotivity and dilution by climatic variations which are resulted from the changes of orbital paameters.The fourth order cycle is represented by fine horizontal laminations caused by seasonal variations.
1995, 13(1): 32-40.
Abstract:
During recent decades exploration, it has been proved that a cerium amount of condensate (or light oil) exists in many natural gas reservoires from most of the oil/gas bearing bssins.The condensate (or light oil)can be divided into three types according to their organic matter in source rock, i.e.,the condensate formed by sapropel organic matter of marine factes, the condensate originated from humic organic matter in coal-bearing strain, and the condensate generated by mixed organic matter of terrestrial sedimentary rock.Detailed discussion is presented in this Paper on the foraging mechanic characteristics of the three types of condensates which originated from different ways.The condensate generated from marine sapropel organic matter is generally formed by the splitting of kerogcn or the high molecular liquid hydrocarbon formed formerly, only the thermal evolution reaches high maturation to over maturation stage (the range of R0 is about 1.3% to 2.0% ).In coal-bearing strata, from immaturation (R00.6%) to over mauration stages, the liquid hydrocarbons formed by the humic organic matter generally are in the from of condensates (ot lightoil) and accompany with natural gases.The condensate might also be formed low to high maturation stage by the mixed organic matter of terrestrial source rock.In order to understand the maturation of the condensates from different bssins in China.The paraffin index and heptane values are calculated by the compositions of condensates.The maturation of the condensate which are estimated by paraffin indexI and heptan values are almost in line with the real geological settings, which shows that the thermal evolution of source rock for the condensates in China ranges from immature to over mature.Some differences are found among the three types of condensates on the aspect of geochemicalcharacteristics.As for their composition,the condensate formed by the humic organic matter of coalbearing strata is relatively rich in aromatic hydrocarbons which is generally 16.2% to 23.5%,and saturation/aromatic ratios range from 3.2 to 5.2, morever, its Pr/Ph ratios are comparatively high (generally higher than 3).The condensalte formed by the marine sapropel organic matter is relatively lower than 1.The mentioned ratios of condensate formed by terrestrial mixed organic matter range between the former two types.The composition of aromatic fraction (naphthanten series, bi-benzene series, and fluoreneseries),low molecular bimarkers (terpane), carbon isotopic composition of alkane and aromatic hydrocarbons are obviously different among the three type of condensates.Based on the above geochemical characteristics the maturity and genetic type of condensate can be identified effectively,and finally to confirm the origin and source of the natural gase associating with them.
During recent decades exploration, it has been proved that a cerium amount of condensate (or light oil) exists in many natural gas reservoires from most of the oil/gas bearing bssins.The condensate (or light oil)can be divided into three types according to their organic matter in source rock, i.e.,the condensate formed by sapropel organic matter of marine factes, the condensate originated from humic organic matter in coal-bearing strain, and the condensate generated by mixed organic matter of terrestrial sedimentary rock.Detailed discussion is presented in this Paper on the foraging mechanic characteristics of the three types of condensates which originated from different ways.The condensate generated from marine sapropel organic matter is generally formed by the splitting of kerogcn or the high molecular liquid hydrocarbon formed formerly, only the thermal evolution reaches high maturation to over maturation stage (the range of R0 is about 1.3% to 2.0% ).In coal-bearing strata, from immaturation (R00.6%) to over mauration stages, the liquid hydrocarbons formed by the humic organic matter generally are in the from of condensates (ot lightoil) and accompany with natural gases.The condensate might also be formed low to high maturation stage by the mixed organic matter of terrestrial source rock.In order to understand the maturation of the condensates from different bssins in China.The paraffin index and heptane values are calculated by the compositions of condensates.The maturation of the condensate which are estimated by paraffin indexI and heptan values are almost in line with the real geological settings, which shows that the thermal evolution of source rock for the condensates in China ranges from immature to over mature.Some differences are found among the three types of condensates on the aspect of geochemicalcharacteristics.As for their composition,the condensate formed by the humic organic matter of coalbearing strata is relatively rich in aromatic hydrocarbons which is generally 16.2% to 23.5%,and saturation/aromatic ratios range from 3.2 to 5.2, morever, its Pr/Ph ratios are comparatively high (generally higher than 3).The condensalte formed by the marine sapropel organic matter is relatively lower than 1.The mentioned ratios of condensate formed by terrestrial mixed organic matter range between the former two types.The composition of aromatic fraction (naphthanten series, bi-benzene series, and fluoreneseries),low molecular bimarkers (terpane), carbon isotopic composition of alkane and aromatic hydrocarbons are obviously different among the three type of condensates.Based on the above geochemical characteristics the maturity and genetic type of condensate can be identified effectively,and finally to confirm the origin and source of the natural gase associating with them.
1995, 13(1): 48-58.
Abstract:
Daihai lake is located in central inner Mongolia and is a modern faulted basin of terrestrial factes.This modern basin is well comparative with the faulted basin of Meozoic and Cenozoic era in the eastern part of China.Deltas is often important infilling sandbodies in faulted basin of terrestrial factes.Therefore, this peper is mainly emphasized on the analysis and Study on the depeitional processes and the favorable reservior sandbodies on different sedimentary scales of two delays in the direction of short axis in Daihai lake basin.One delta, called Yuanzigou delay, is located in thenorthern steep slope of the lake basin, while another one, Bulianghe detla, in the sourthen gentle slope of the lake basin.Both are fluvial-dominated braided deltuic system with coarse deceits.Provenances of two delays are varying form eath other.Yuanzigou river is a short distance ephemeral braided stream and Bulianghe river a long distance ephemeral braided stream.Through element analysis of lithology, grain size, sedimentary structures, thickness of sandbeds, clastic components and color etc., the description and interpretation of the depositional features of two delays are provided.12 lithofacies or genetic factes form two delays have been defined.Their mutual assemblages in verprofile make up different type of lithofaices assemblages or vertical sedimentary sequences, each corresponding to a cerium depeitional process and subenvironment.Therefore, nine sedimentury sequences have been recognized which reflect depositztional features in different perts of two btaided delays.The four sedimentary sub environments or sedimentary factes zones of each delay were distinguished by depeitional features,that is, (1) upper delta plain, (2) lower delta plain, (3) delta front slope and (4) pre-delta.The two delay have been modelled.There are both similarities and differences of depositional features among Yuanzigen delta and Bulianghe delay.Moreever depositional precesses and features between fan delta and braided delta have been discussed in this paper.There exists apparent control of depeitional processes and sedimentary factes zones on the reservoir of two delays.The deltas of the steep and gentle slope in the direction of short axis in the faulted barn have some different features of sedimentary and geometry shape of sandbodies.Finally,through sedimentary sequences, porosity zones and sandbodies geometry of two delays, the sketch model of two delays,sandbody at 3-D sauce extension in each sedimentary zones have been set up.
Daihai lake is located in central inner Mongolia and is a modern faulted basin of terrestrial factes.This modern basin is well comparative with the faulted basin of Meozoic and Cenozoic era in the eastern part of China.Deltas is often important infilling sandbodies in faulted basin of terrestrial factes.Therefore, this peper is mainly emphasized on the analysis and Study on the depeitional processes and the favorable reservior sandbodies on different sedimentary scales of two delays in the direction of short axis in Daihai lake basin.One delta, called Yuanzigou delay, is located in thenorthern steep slope of the lake basin, while another one, Bulianghe detla, in the sourthen gentle slope of the lake basin.Both are fluvial-dominated braided deltuic system with coarse deceits.Provenances of two delays are varying form eath other.Yuanzigou river is a short distance ephemeral braided stream and Bulianghe river a long distance ephemeral braided stream.Through element analysis of lithology, grain size, sedimentary structures, thickness of sandbeds, clastic components and color etc., the description and interpretation of the depositional features of two delays are provided.12 lithofacies or genetic factes form two delays have been defined.Their mutual assemblages in verprofile make up different type of lithofaices assemblages or vertical sedimentary sequences, each corresponding to a cerium depeitional process and subenvironment.Therefore, nine sedimentury sequences have been recognized which reflect depositztional features in different perts of two btaided delays.The four sedimentary sub environments or sedimentary factes zones of each delay were distinguished by depeitional features,that is, (1) upper delta plain, (2) lower delta plain, (3) delta front slope and (4) pre-delta.The two delay have been modelled.There are both similarities and differences of depositional features among Yuanzigen delta and Bulianghe delay.Moreever depositional precesses and features between fan delta and braided delta have been discussed in this paper.There exists apparent control of depeitional processes and sedimentary factes zones on the reservoir of two delays.The deltas of the steep and gentle slope in the direction of short axis in the faulted barn have some different features of sedimentary and geometry shape of sandbodies.Finally,through sedimentary sequences, porosity zones and sandbodies geometry of two delays, the sketch model of two delays,sandbody at 3-D sauce extension in each sedimentary zones have been set up.
1995, 13(1): 69-74.
Abstract:
In 1947 Urey presented a poper concerning the thermodynamics of isotopic systems and suggested that variations in the temperature of precipitation of calcium carbonate from water should lead to measurable varistions in the O/O ratio of the calcium carbonate.He Postulated that the determination of temperature of the ancient oceans should be possible, in principle, by measuring the O-content of fossil calcite shells.In 1950 McCrea concluded that isotopic fidelity was optimally obtained by utilizing a procedure in which 100% phosphoric acid at 25℃ dissolved the carbonate.Shortly afterwards, with the recognition of consistent isotopic signals in the sedimentary records of many different areas, Emiliani (1955, 1966 ) defined isotopic stages.Since then geochemistry of stable isotope of carbonate has widely been used in the Studies of paleoclimate.In recent years, with the deepgoing of global change research, many scientists try to obtain more derail information on poleoclimatic variations through the study of isotope of carbonates in loess sediments by the t6chnique of phosphoric acid decomposition.However, the carbonates in loess sediments are a mixture of primary carbonates and secondary carbonates.In the mixture, only secondary carbonates can provide the poleoclimatic information during deposition.Unfortunately, no effective technique can, so far, separate the secondary carbonates from samples and the carbon and oxygen isotopic compeitions measured by the technique of phosphoric acid decompeition are those of total Carbonates in loess sediments.In order to study the relationship between isotope of carbonates in loess sediments and Paleoclimate,stepwise heating technique was used.The resultS show that the carbonates ftom different sources and different genesises have different carbon and oxygen isotopic compeitions and also different tracer significance.The carbon isotopic composition of 700-800℃is more sensitive to paleoclimatic change than that of phosphoric acid decomposition technique.Therefore, phosphoric acid decompeition technique is not fit to analyse the isotopic compositions of carbonates in loess sediments.
In 1947 Urey presented a poper concerning the thermodynamics of isotopic systems and suggested that variations in the temperature of precipitation of calcium carbonate from water should lead to measurable varistions in the O/O ratio of the calcium carbonate.He Postulated that the determination of temperature of the ancient oceans should be possible, in principle, by measuring the O-content of fossil calcite shells.In 1950 McCrea concluded that isotopic fidelity was optimally obtained by utilizing a procedure in which 100% phosphoric acid at 25℃ dissolved the carbonate.Shortly afterwards, with the recognition of consistent isotopic signals in the sedimentary records of many different areas, Emiliani (1955, 1966 ) defined isotopic stages.Since then geochemistry of stable isotope of carbonate has widely been used in the Studies of paleoclimate.In recent years, with the deepgoing of global change research, many scientists try to obtain more derail information on poleoclimatic variations through the study of isotope of carbonates in loess sediments by the t6chnique of phosphoric acid decomposition.However, the carbonates in loess sediments are a mixture of primary carbonates and secondary carbonates.In the mixture, only secondary carbonates can provide the poleoclimatic information during deposition.Unfortunately, no effective technique can, so far, separate the secondary carbonates from samples and the carbon and oxygen isotopic compeitions measured by the technique of phosphoric acid decompeition are those of total Carbonates in loess sediments.In order to study the relationship between isotope of carbonates in loess sediments and Paleoclimate,stepwise heating technique was used.The resultS show that the carbonates ftom different sources and different genesises have different carbon and oxygen isotopic compeitions and also different tracer significance.The carbon isotopic composition of 700-800℃is more sensitive to paleoclimatic change than that of phosphoric acid decomposition technique.Therefore, phosphoric acid decompeition technique is not fit to analyse the isotopic compositions of carbonates in loess sediments.
1995, 13(1): 82-87.
Abstract:
There is a lot of geological information in dipmeters.Not only can lithological boundaries be respondded, but also bedding planes of time equivalent can be detected by dipmet6rs.In other woads,when sedimentary structure of a zone chanses, the dip angle and azimuth of the zone wil change.According tO the relationship of dip vectors with depth, five grouch of dip Patterns (color Patterns)are defined on odpole plot, i.e., blue pattern, red pattern, green pattern, yellow pattern, and white pattern.These patterns stand for different sedimentary structures.Sand bodies contsin three major groupe of dip patterns: peleocurrent indscatort (current boding, downsttea accration and progradation); thalweg indicators (lateral accretion and erosional contact); and topogtsphic indicators (compection).Paieocurrent and thalweg indicators are used in current domiinant sand bodies such as fluvial channes and deltas.The compaction indicators used in defining topograhic features such as reefs and bars.The following edimentolodcal features can be studied by integrated analysis of tadpole plots, azimuth plots, and Pad resistivity curves with correlation lines:(1) Bed shape: bed thickness, lateral dimension of beds, and bedding Plane.(2) Nature of bed boundries:the transition from one lager to another can either be abrupt or gradual.(3) Bedding factores, several types of internal organization can be recognized, such as massive bedding,laminated bedding, and imbricated bedding.(4) Rhythms and cycles.(5)Paleocurrent direction and thicking direction of sand body.(6) Major sand bodies.When sedimentary environment (such as delta) is known, sandbodies (distributary channel or mouth bar sands, etc.) can be recognized.
There is a lot of geological information in dipmeters.Not only can lithological boundaries be respondded, but also bedding planes of time equivalent can be detected by dipmet6rs.In other woads,when sedimentary structure of a zone chanses, the dip angle and azimuth of the zone wil change.According tO the relationship of dip vectors with depth, five grouch of dip Patterns (color Patterns)are defined on odpole plot, i.e., blue pattern, red pattern, green pattern, yellow pattern, and white pattern.These patterns stand for different sedimentary structures.Sand bodies contsin three major groupe of dip patterns: peleocurrent indscatort (current boding, downsttea accration and progradation); thalweg indicators (lateral accretion and erosional contact); and topogtsphic indicators (compection).Paieocurrent and thalweg indicators are used in current domiinant sand bodies such as fluvial channes and deltas.The compaction indicators used in defining topograhic features such as reefs and bars.The following edimentolodcal features can be studied by integrated analysis of tadpole plots, azimuth plots, and Pad resistivity curves with correlation lines:(1) Bed shape: bed thickness, lateral dimension of beds, and bedding Plane.(2) Nature of bed boundries:the transition from one lager to another can either be abrupt or gradual.(3) Bedding factores, several types of internal organization can be recognized, such as massive bedding,laminated bedding, and imbricated bedding.(4) Rhythms and cycles.(5)Paleocurrent direction and thicking direction of sand body.(6) Major sand bodies.When sedimentary environment (such as delta) is known, sandbodies (distributary channel or mouth bar sands, etc.) can be recognized.
1995, 13(1): 94-101.
Abstract:
It is a fundamental work to study sedimentary factes or micro factes in reservoir description.In order to reveal the sizes and distribution of the reservoirs and to help the oil development,this Paper emphasizes that it is very important to apply integratedly geological,seismic, lOgging information to identify the depositional environments, factes or microfacies types of the reservoirs by means of computer program.However, the consideration and methods of sedimentary factes are different in the reservoir descriptions at different singes of Petroleum exploration or development.Because the reservoir description at the exploration stage is carried on under the situation that only a few drilled wells and their logging are available in which the industrial discovery has been found, the description is made mainly on seismic information.At this stage, study of sedimentary factes is first to establish the seismic sequences by the terminal characteristics of the reflections, toset up sequencial stratigraphic framework, to identify seismic factes types by structural nature of the reflections with each seismic sequence,then to transform the seismic factes into sedimentaey factes by the velocity spectrum,at last to classify the types of dePOsitional systems and to determine the distribution of the structural lithofacies belts.After a large number of geological, seismic and logging data has been received in the programming exploration, the reservoir description is conducted on some problems from the oil exploration and development.At this sarge the sedlimentary factes analysis is to integrate all the available information to reveal all the sub-factes and micro factes and their distribution in the seismic sub-sequence and then to correlate the micro factes of the sandbodies and the hydrocarbon accumulations.The reservoirs in Es of the Niuzhuang Oil field, the Dongying Depression, vary greatly in the lithology and factes, which leads to alternative recognizations in the stratigraphy correlation, sandbody genesis and distribution.In the study on the Oilfield, the authors firstly classified the Esi into 12 seismic factes and corresponding sedimentary factes,outlined six sand lobesof the delay, and then studied the formation and arrangement of the iso-chronous lobe and concluded that each lobe consisted of the main-fan,marginal fan, inter fan and slip zone.The main-fan controlled the distribution of oil and gas.The study of sedimentary factes in the reservoir description at the development stage represents fully using large volumes of drilling and logging data to analyse the microfacies of each sandbody in the devaloping sequences so that expound the anisotropy of the sandbody.In the research at the Zaoyuan Oilfield,the authors applied the pattern identification for the first time to auto classifying and correlating the reservoirs, then carried on the logging factes analysis and mapped sandbody distributions for the 48 layers in the 9 reservoir groups by means of the combination of the single-well factes analysis map, the cross-well section correlation,the iso-lines of sand/mud ratio and isopach map of the sandstones.Therefore, the research has established the sizes and distribution of all the sandbodies in the developing sequences and made solid foundation for enhancement of oil recovery.
It is a fundamental work to study sedimentary factes or micro factes in reservoir description.In order to reveal the sizes and distribution of the reservoirs and to help the oil development,this Paper emphasizes that it is very important to apply integratedly geological,seismic, lOgging information to identify the depositional environments, factes or microfacies types of the reservoirs by means of computer program.However, the consideration and methods of sedimentary factes are different in the reservoir descriptions at different singes of Petroleum exploration or development.Because the reservoir description at the exploration stage is carried on under the situation that only a few drilled wells and their logging are available in which the industrial discovery has been found, the description is made mainly on seismic information.At this stage, study of sedimentary factes is first to establish the seismic sequences by the terminal characteristics of the reflections, toset up sequencial stratigraphic framework, to identify seismic factes types by structural nature of the reflections with each seismic sequence,then to transform the seismic factes into sedimentaey factes by the velocity spectrum,at last to classify the types of dePOsitional systems and to determine the distribution of the structural lithofacies belts.After a large number of geological, seismic and logging data has been received in the programming exploration, the reservoir description is conducted on some problems from the oil exploration and development.At this sarge the sedlimentary factes analysis is to integrate all the available information to reveal all the sub-factes and micro factes and their distribution in the seismic sub-sequence and then to correlate the micro factes of the sandbodies and the hydrocarbon accumulations.The reservoirs in Es of the Niuzhuang Oil field, the Dongying Depression, vary greatly in the lithology and factes, which leads to alternative recognizations in the stratigraphy correlation, sandbody genesis and distribution.In the study on the Oilfield, the authors firstly classified the Esi into 12 seismic factes and corresponding sedimentary factes,outlined six sand lobesof the delay, and then studied the formation and arrangement of the iso-chronous lobe and concluded that each lobe consisted of the main-fan,marginal fan, inter fan and slip zone.The main-fan controlled the distribution of oil and gas.The study of sedimentary factes in the reservoir description at the development stage represents fully using large volumes of drilling and logging data to analyse the microfacies of each sandbody in the devaloping sequences so that expound the anisotropy of the sandbody.In the research at the Zaoyuan Oilfield,the authors applied the pattern identification for the first time to auto classifying and correlating the reservoirs, then carried on the logging factes analysis and mapped sandbody distributions for the 48 layers in the 9 reservoir groups by means of the combination of the single-well factes analysis map, the cross-well section correlation,the iso-lines of sand/mud ratio and isopach map of the sandstones.Therefore, the research has established the sizes and distribution of all the sandbodies in the developing sequences and made solid foundation for enhancement of oil recovery.
1995, 13(1): 110-116.
Abstract:
The Bolhinur Mt.Formation of the Upper Silurian is widely distributed in the Bolhinur Mt.region.The Formation was formed in the closing stage of the Bolhinur Early Palaeozoic Aulacogen and is famous for its purplish red sediments.Having analysed sedimentologic，petrologic and petrochemical features, the author probes into the tectonic setting of the Bolhinur Mt.Formation of the Upper Silurian and concludes that the Fomation was turbidity current sediments and formed in close relationship with an active continental margin.The source area of the Fomation was mainly southern"Yining oldland",which had certain continental crust and middle maturity.
The Bolhinur Mt.Formation of the Upper Silurian is widely distributed in the Bolhinur Mt.region.The Formation was formed in the closing stage of the Bolhinur Early Palaeozoic Aulacogen and is famous for its purplish red sediments.Having analysed sedimentologic，petrologic and petrochemical features, the author probes into the tectonic setting of the Bolhinur Mt.Formation of the Upper Silurian and concludes that the Fomation was turbidity current sediments and formed in close relationship with an active continental margin.The source area of the Fomation was mainly southern"Yining oldland",which had certain continental crust and middle maturity.
1995, 13(1): 126-132.
Abstract:
Grain-Size Analysis Expert System for Sedimentary Rock consistS of knowledge base,inference engine, data base, acquiring knowledge, user interface and daal pre-handling.According tO the reserch result about grain-size analysis for sedimentary rock in recent years,we have stored the knowledge and experience in the Knowledse Base in IF-THEN rules.There are 210 rules in the knowledge base.They can be classified into two typeS, which are used to definename of sedimentary rock in 80 rules, and determine its environment and factes in other rules.Its inference engine that was provided by Expert Develoment tool Vp-Expert nas backward,forward chainining and method of confidence factor.It can automatically choose the knowledge in rules, then records the conclusion and informes the user, or queries or explains about the question to the user during consultation process.In order to acquire a lot of knowledge and experience about gum-size analysis for sedimentary rock from user and make it more flexible, dBASE files or Foxbase files are used as its information base.By means of accessing and inputing daal stored in the information base, we have designed some programs that can actually modify data during consultation process.Therefore, this system has the ability to learn from experience or acquire knowledge from user during consultation process.The model of data pre-handling can be used to calculate some statistical P8rameters and dtaw some statistical graphs of grain-size analysis results.In brief, this system has better user interface, and can handle about data, define itS name and distinguish one from 7 different sedimentary environment or factes when sedimentary rock was formed according to results of grain-size analysis for sedimentary rock.
Grain-Size Analysis Expert System for Sedimentary Rock consistS of knowledge base,inference engine, data base, acquiring knowledge, user interface and daal pre-handling.According tO the reserch result about grain-size analysis for sedimentary rock in recent years,we have stored the knowledge and experience in the Knowledse Base in IF-THEN rules.There are 210 rules in the knowledge base.They can be classified into two typeS, which are used to definename of sedimentary rock in 80 rules, and determine its environment and factes in other rules.Its inference engine that was provided by Expert Develoment tool Vp-Expert nas backward,forward chainining and method of confidence factor.It can automatically choose the knowledge in rules, then records the conclusion and informes the user, or queries or explains about the question to the user during consultation process.In order to acquire a lot of knowledge and experience about gum-size analysis for sedimentary rock from user and make it more flexible, dBASE files or Foxbase files are used as its information base.By means of accessing and inputing daal stored in the information base, we have designed some programs that can actually modify data during consultation process.Therefore, this system has the ability to learn from experience or acquire knowledge from user during consultation process.The model of data pre-handling can be used to calculate some statistical P8rameters and dtaw some statistical graphs of grain-size analysis results.In brief, this system has better user interface, and can handle about data, define itS name and distinguish one from 7 different sedimentary environment or factes when sedimentary rock was formed according to results of grain-size analysis for sedimentary rock.
1995, 13(1): 7-17.
Abstract:
In order to evaluate the effect of organic acids on the dissolution of feldspar at different burial temperatures，perthite dissolution by acetic acid experiments were run at 650C，2 OMpa;75℃， 3 OMpa;95℃，30Mpa and 1300C，30Mpa.The experimental results are as follows: 1)Postassium，sodium and aluminium were preferentially released，but silicon was last released in feldspar dissolution. 2)Under the conditions of relatively low temperature，the ratio of released cations was far from the chemical composition of dissolved feldspar，but when increasing temperature，it was gradually close to the composition. 3 ) In perthite，albite is more easily to be decomposed than K一feldspar. 4)Temperature effect of silicon is 5.4，8.6 and 9.2 times as large as sodium，aluminium and potassium，respectively. 5)Compared with aluminium，most silicon released at relatively high temperature (more than 95℃).It implies that the precipitation of authigenic SiO2 minerals which blocked up most of porosity occurred at the burial depth with geotemperature mare than 95 C.
In order to evaluate the effect of organic acids on the dissolution of feldspar at different burial temperatures，perthite dissolution by acetic acid experiments were run at 650C，2 OMpa;75℃， 3 OMpa;95℃，30Mpa and 1300C，30Mpa.The experimental results are as follows: 1)Postassium，sodium and aluminium were preferentially released，but silicon was last released in feldspar dissolution. 2)Under the conditions of relatively low temperature，the ratio of released cations was far from the chemical composition of dissolved feldspar，but when increasing temperature，it was gradually close to the composition. 3 ) In perthite，albite is more easily to be decomposed than K一feldspar. 4)Temperature effect of silicon is 5.4，8.6 and 9.2 times as large as sodium，aluminium and potassium，respectively. 5)Compared with aluminium，most silicon released at relatively high temperature (more than 95℃).It implies that the precipitation of authigenic SiO2 minerals which blocked up most of porosity occurred at the burial depth with geotemperature mare than 95 C.
1995, 13(1): 27-31.
Abstract:
Based on the study on element ratios of Mn0/TiO2, Al/(Al十Fe-Mn) and corrlation Chart of Fe/Ti一Al/ (Al十Fe-+Mn)，Triangle Diagram of Al一Fe一Mn as well as atomic weight of silicolites in Yaluzangbu suture belt, Tibet，this paper discusses the genesis of the silicolites and the formation as well as evolutionary history of the suture belt.
Based on the study on element ratios of Mn0/TiO2, Al/(Al十Fe-Mn) and corrlation Chart of Fe/Ti一Al/ (Al十Fe-+Mn)，Triangle Diagram of Al一Fe一Mn as well as atomic weight of silicolites in Yaluzangbu suture belt, Tibet，this paper discusses the genesis of the silicolites and the formation as well as evolutionary history of the suture belt.
1995, 13(1): 41-47.
Abstract:
This peper tubes the Haizhou outcrop sandally in Fuxin Basin as an example.Four main sandboies and some supplementary sandbodies are practically measured in a large scale and sampled densely.According to four basical principles of the establishment of reservoir geological model,based on the reserches of sedimentuny sequence.diagenesis and pete evolution.physical property andbeterogeneity, one-dimensional reservoir geological models of 60m .20m .10m.30m.1m (A-typeand B-type) grades are established.Combined with architeCtural-element analysis.sedimentary model.disgenesis model and Physical model, four two-dimensional reservoir geological models of fan, fanend and front-fan braided stream are established.The models established are of unified lithologies and physical Properties.Thus, they are prototype models or concept models.
This peper tubes the Haizhou outcrop sandally in Fuxin Basin as an example.Four main sandboies and some supplementary sandbodies are practically measured in a large scale and sampled densely.According to four basical principles of the establishment of reservoir geological model,based on the reserches of sedimentuny sequence.diagenesis and pete evolution.physical property andbeterogeneity, one-dimensional reservoir geological models of 60m .20m .10m.30m.1m (A-typeand B-type) grades are established.Combined with architeCtural-element analysis.sedimentary model.disgenesis model and Physical model, four two-dimensional reservoir geological models of fan, fanend and front-fan braided stream are established.The models established are of unified lithologies and physical Properties.Thus, they are prototype models or concept models.
1995, 13(1): 59-68.
Abstract:
The "Taojiang-type manganese" is situated at the slope-basin margin factes zone of Modaoxi Formation, Middle Odivician in Central Hunan Province.The manganese-bearing series consists of manganese ore,black carbonaceous mudrock and mass clayrock.The manganese ore bed shows a lot of graded bedding, parallel bedding, small scale cross-bedding, horizontal bedding,braccisted structure and scour mark Structure ......etc.,with ABCE or ABE Bouma sequence,which may berecognized as carbonate gravity flow deposits (turbidite).The formation of manganese ore was affected and controlled by tectonics, sedimentary facies and pelaeogeography, sedimentary geological events and physicochemical condition of medium and so on.There are evidences of sedimentology and geochemistry Showing that the manganese originates from hydrothermal exhalation and extrusion at the spreading sea-noor.The mechanism of manganese ore is divided into two Stugds:first stage is Mn2+ migration in anoxic water;second stage is Mn2+ precipitation and replacing carbonate ooze.The higher content manganese ore is formed to benefit by recrystallization in the fate diasensis sarge of the sedimentary rock.
The "Taojiang-type manganese" is situated at the slope-basin margin factes zone of Modaoxi Formation, Middle Odivician in Central Hunan Province.The manganese-bearing series consists of manganese ore,black carbonaceous mudrock and mass clayrock.The manganese ore bed shows a lot of graded bedding, parallel bedding, small scale cross-bedding, horizontal bedding,braccisted structure and scour mark Structure ......etc.,with ABCE or ABE Bouma sequence,which may berecognized as carbonate gravity flow deposits (turbidite).The formation of manganese ore was affected and controlled by tectonics, sedimentary facies and pelaeogeography, sedimentary geological events and physicochemical condition of medium and so on.There are evidences of sedimentology and geochemistry Showing that the manganese originates from hydrothermal exhalation and extrusion at the spreading sea-noor.The mechanism of manganese ore is divided into two Stugds:first stage is Mn2+ migration in anoxic water;second stage is Mn2+ precipitation and replacing carbonate ooze.The higher content manganese ore is formed to benefit by recrystallization in the fate diasensis sarge of the sedimentary rock.
1995, 13(1): 75-81.
Abstract:
The main environment from Middle to Upper Cambrian is anopen epicontinental sea in Liujiang Basin, Hebei.ooidal bank and gravel bank are widely distributed on the shallow sea area.Under the influence of environment, algal colony forms vary with the horizon from Zhangxia Formation to Gushan Formation and Changshan Formation in which there are lots of algal bioherms.A perfect sequence is formed by all bioherms in evolution.There are three kinds of biolithites coming from the all bioherms.Each of biolithites is built up by a certain algae.It is easy to recognize these biolithites in outcrop.The principal features are described as follows.Epiphyton bafflestone is mainly distributed in the upper of Zhangxia Formation and the lower of Gushan Formation.They are ofen made up of mounds, of which the scale varies from 2 to 3 m in width and from 1 to 3 m in height.Thrombolite bindstone is mainly distributed in the middle of Gushan Formation.The shapes of the thrombolite mound and Epiphyton mound are very much alike.Stromatolites biolithite is mainly distributed in the upper of Gushan Formation and the lower of Changshan Formation, of which the shapes are thick bedded (Fig.1).Moreover,algal bioherms are closely related with oolite limestone, mud-stripe limestone and calcrirudite.All the mounds and the reefs that are made up of by three kinds of algal limestone mentioned above occur in 8 horizons from the middle to upper Cambrian in this area.From bottom to top they are Epiphiton baffling mounds, thrombolite mounds and stromatolites reefs.Each of the all bioherms is distributed in similar sequences in lithofacies.About 8 sedimentary rhythms are made of all sequences, in which every one begins at rudite that is distributed widely and uncontinuously in horizon, and then the algal mound and reef are built up on the convex part of the rudite bed.There is a clear bounbsry surface between the bioherm and rudite.The top of sequence is oolite limestone.This is a remarkable assemblage in lithofacies that makes rudite, bioherm and oolite which forms an organic whole.There are two clues to recognize the bioherms evolution in this area, one is that the skeleton calcareous algae evolving toward blue-green algae of non-skeleton while the shape of bioherms maintain the Same (R1-R5); and the other is that the massive algae mounds evolve toward stromatolites reefs of thick bedded while algal contents maintain the same (R4--R8) (Fig.2).Each kind of biolithites formed in a cerium environment.The Epiphiton bafflestone is suitable to deeper water on the front of coldal bank.This environment corresponds to the lower part of subtidal.The thrombolite bindstone is suitable to shallower water on the front of coldal bank.This environment corresponds to the upper part of subtidal.The stromatolites biolithite relates mainly to restricted environment on the back of ooidal bank.The evolutionary sequence of algal bioherms noted the geological process that the sedimentary .environment evolved from deeper water on the front of the ooidal bank, setting margin of a carbonate platform,to restricted environment on the back of ooldal bank.
The main environment from Middle to Upper Cambrian is anopen epicontinental sea in Liujiang Basin, Hebei.ooidal bank and gravel bank are widely distributed on the shallow sea area.Under the influence of environment, algal colony forms vary with the horizon from Zhangxia Formation to Gushan Formation and Changshan Formation in which there are lots of algal bioherms.A perfect sequence is formed by all bioherms in evolution.There are three kinds of biolithites coming from the all bioherms.Each of biolithites is built up by a certain algae.It is easy to recognize these biolithites in outcrop.The principal features are described as follows.Epiphyton bafflestone is mainly distributed in the upper of Zhangxia Formation and the lower of Gushan Formation.They are ofen made up of mounds, of which the scale varies from 2 to 3 m in width and from 1 to 3 m in height.Thrombolite bindstone is mainly distributed in the middle of Gushan Formation.The shapes of the thrombolite mound and Epiphyton mound are very much alike.Stromatolites biolithite is mainly distributed in the upper of Gushan Formation and the lower of Changshan Formation, of which the shapes are thick bedded (Fig.1).Moreover,algal bioherms are closely related with oolite limestone, mud-stripe limestone and calcrirudite.All the mounds and the reefs that are made up of by three kinds of algal limestone mentioned above occur in 8 horizons from the middle to upper Cambrian in this area.From bottom to top they are Epiphiton baffling mounds, thrombolite mounds and stromatolites reefs.Each of the all bioherms is distributed in similar sequences in lithofacies.About 8 sedimentary rhythms are made of all sequences, in which every one begins at rudite that is distributed widely and uncontinuously in horizon, and then the algal mound and reef are built up on the convex part of the rudite bed.There is a clear bounbsry surface between the bioherm and rudite.The top of sequence is oolite limestone.This is a remarkable assemblage in lithofacies that makes rudite, bioherm and oolite which forms an organic whole.There are two clues to recognize the bioherms evolution in this area, one is that the skeleton calcareous algae evolving toward blue-green algae of non-skeleton while the shape of bioherms maintain the Same (R1-R5); and the other is that the massive algae mounds evolve toward stromatolites reefs of thick bedded while algal contents maintain the same (R4--R8) (Fig.2).Each kind of biolithites formed in a cerium environment.The Epiphiton bafflestone is suitable to deeper water on the front of coldal bank.This environment corresponds to the lower part of subtidal.The thrombolite bindstone is suitable to shallower water on the front of coldal bank.This environment corresponds to the upper part of subtidal.The stromatolites biolithite relates mainly to restricted environment on the back of ooidal bank.The evolutionary sequence of algal bioherms noted the geological process that the sedimentary .environment evolved from deeper water on the front of the ooidal bank, setting margin of a carbonate platform,to restricted environment on the back of ooldal bank.
1995, 13(1): 88-93.
Abstract:
During sediments to be overlaid, a series of geological events occured.Especially when the underground water took partal, they become very complex.In these events, a large amount of minerals generated or converted and some minerals or elastics dissolved, which resulted in lots of secondary pores generation.It is not only important to improve the properties of reservior rock, but also to form diagenetic trap.Therefore, studying the complex diagenetic events is not only a Part of lithology and sedimentology, but also a part of Petroleum geology and reservior geology.In this paper, all of those geological events occured in underground environment assumed to be a series of physicochemical reactions.Those reactions alwayas follow Thermodynamic-Second Law and Third-Law.According to those assumptions, a method is derived which can be used to determine the diagenetic sequences by calculating the reaction Gibbs energy.The method is more logical and more reliable than the traditional method by which the sequences are determined use of identifying the concocts and shapes of secondary minerals.At last this method is verified by two examples which are from two models of oil fields (China and American).This poper presents a good demonstration for how to research reservior rock development history quantitatively.
During sediments to be overlaid, a series of geological events occured.Especially when the underground water took partal, they become very complex.In these events, a large amount of minerals generated or converted and some minerals or elastics dissolved, which resulted in lots of secondary pores generation.It is not only important to improve the properties of reservior rock, but also to form diagenetic trap.Therefore, studying the complex diagenetic events is not only a Part of lithology and sedimentology, but also a part of Petroleum geology and reservior geology.In this paper, all of those geological events occured in underground environment assumed to be a series of physicochemical reactions.Those reactions alwayas follow Thermodynamic-Second Law and Third-Law.According to those assumptions, a method is derived which can be used to determine the diagenetic sequences by calculating the reaction Gibbs energy.The method is more logical and more reliable than the traditional method by which the sequences are determined use of identifying the concocts and shapes of secondary minerals.At last this method is verified by two examples which are from two models of oil fields (China and American).This poper presents a good demonstration for how to research reservior rock development history quantitatively.
1995, 13(1): 102-109.
Abstract:
From the viewPOint of dynamic stratigraphy,and on the basis of series (55 sheets) isopach maPS of coal seam and sandbody in the coal region of Hou County, Shanxi, this study reveals that the prOCess of the development of coal-bearing basin's structure is very clear and is of obvious heredity.Form Benxi annnd Taiyuan age of Late catboniferous Shanxi age of Early Permian, the arrangement direction of all sedimentary bodies in this region is NE-NEE.It is well observed not only on the sand bodies with better orientation, but also on the limestones with worse orientation.This paper introduces 4 isopach maPS, indicating the arrangement of Benxi limestone and sandstone,Taiyuan sandstone under cpal seam No.11 and limestone K2, K3, K4, Shanxi coal seam No.2 and sand they under coal seam No.2.On the basis of the heredity of coal-bearing basin's structure development the derailed analysis and correlation of lotS of isopach maps of coal seam ash content and the isopach maPS of the thickness of sand body under each of the coal seam reveal that the areaof hasher ash'content in all coal seams and the area of each underlying sand they with greaterthickness are in staggered position, in other words, the former is on the thinner belts of the latter or on the POints of disapperance of the latter, for example, the main workable coal seam No.10 and No.11 in the lower pert of Taiyuan FOrmation, the main workable coal seam No.2 and the partly workable coal seam No.1 and corresponding underlying sand theies are the cases.This relationship is even discovered in foreisn reference, for example, in 2 maPS cited by Galloway (1983) fromGairneros(1980), which were redrawn by the authors.It is suggested that the abated relationship depend on the difference of mini relief caused by the existence of underlying sand they in the opt-forming swamp, and the difference of mini relief caused the difference of underground water debit, which flowed through the swamp and brought the fine suspension of clast into it.As for the majority of sand theies and coal seams in the environment of the fluvial channel and the distributary channel of delay, the flood basin beyond the sand body hed a lower relief, so that the groundwater debit, which flowed through the swamp, was greater,and the suspension of clast,which was brought into the swamp, was also more.As discussed above that in these environments the area with thicker coal seam and with thicker sand body are arranged in staggered position, so that in such a case coal ash content in thicker coal seam is higher than in thiner coal seam.As for the coal seam formed on the basis of tidal flat barrier the thicker belt of coal seam and the underlying thicker sand body are in superimPOsed POsition.But in this case high ash content area was located in the place with lower relief far from the tidal flat barrier, where the groundwater debit was greater.The difference in the latter environment is that the higher ash content and underlying sand body by all appearance will have positive effect on the prediction of coal ash content in coal prospecting and is a useful auxiliary mark for the environment recognition.
From the viewPOint of dynamic stratigraphy,and on the basis of series (55 sheets) isopach maPS of coal seam and sandbody in the coal region of Hou County, Shanxi, this study reveals that the prOCess of the development of coal-bearing basin's structure is very clear and is of obvious heredity.Form Benxi annnd Taiyuan age of Late catboniferous Shanxi age of Early Permian, the arrangement direction of all sedimentary bodies in this region is NE-NEE.It is well observed not only on the sand bodies with better orientation, but also on the limestones with worse orientation.This paper introduces 4 isopach maPS, indicating the arrangement of Benxi limestone and sandstone,Taiyuan sandstone under cpal seam No.11 and limestone K2, K3, K4, Shanxi coal seam No.2 and sand they under coal seam No.2.On the basis of the heredity of coal-bearing basin's structure development the derailed analysis and correlation of lotS of isopach maps of coal seam ash content and the isopach maPS of the thickness of sand body under each of the coal seam reveal that the areaof hasher ash'content in all coal seams and the area of each underlying sand they with greaterthickness are in staggered position, in other words, the former is on the thinner belts of the latter or on the POints of disapperance of the latter, for example, the main workable coal seam No.10 and No.11 in the lower pert of Taiyuan FOrmation, the main workable coal seam No.2 and the partly workable coal seam No.1 and corresponding underlying sand theies are the cases.This relationship is even discovered in foreisn reference, for example, in 2 maPS cited by Galloway (1983) fromGairneros(1980), which were redrawn by the authors.It is suggested that the abated relationship depend on the difference of mini relief caused by the existence of underlying sand they in the opt-forming swamp, and the difference of mini relief caused the difference of underground water debit, which flowed through the swamp and brought the fine suspension of clast into it.As for the majority of sand theies and coal seams in the environment of the fluvial channel and the distributary channel of delay, the flood basin beyond the sand body hed a lower relief, so that the groundwater debit, which flowed through the swamp, was greater,and the suspension of clast,which was brought into the swamp, was also more.As discussed above that in these environments the area with thicker coal seam and with thicker sand body are arranged in staggered position, so that in such a case coal ash content in thicker coal seam is higher than in thiner coal seam.As for the coal seam formed on the basis of tidal flat barrier the thicker belt of coal seam and the underlying thicker sand body are in superimPOsed POsition.But in this case high ash content area was located in the place with lower relief far from the tidal flat barrier, where the groundwater debit was greater.The difference in the latter environment is that the higher ash content and underlying sand body by all appearance will have positive effect on the prediction of coal ash content in coal prospecting and is a useful auxiliary mark for the environment recognition.
1995, 13(1): 117-125.
Abstract:
On the bests of study of geochemical behavior of sin81e elements,the paper has established a mathematic model for linear relationships between elementS in the chemical sedimentary process of a semi-closed system:which is very similar to that of magmatic fractional crystallization (Wan Yusheng, 1990).In the formula, C C and C C represent the contents of elements x and y in original saturated solution and reSidual satuxated solution respectively, Dx and Dy are bulk distribution coefficentS of x and y ,Fi is reSidual ratio of saturated solution, and t is solute proPOrtion in saturated solution.Example shave also been given to show how to apply the method to research on saline sedimentation.Following are some main conclusions:1) The regression line representS the result of the linear regression of a cutve with lesscurvature.Foe an incompatible element-fair, the more similar the properties of two elements andthe smaller their bulk distribtition coefficientS are, the better the regresion line is.2)The nit6rcept and slope of the regression line have clearly geochemical significance.Both ofthem are constituted by the P8rametCrs C,C, Dx, Dy, t and Fl.If x and y are incompatible, then the slope of the line will be active and the line will intersect a relatively compatible element axis.When D values of x and y are similar, the intercept and slope of the regression line are close to zeroand C/C respectively.3)There could be different degrees of linear correlations between two elements of elementpair at different stages of evolution of the saline water, resulting from asynchronous variations ofthe bulk diStribution coefficients of the elements.And in different saline water systems, the sameelement-pairs can represent different degrees of linear correlations, so the chemical compositions of the systems will strongly influence the geochemical behaviors of the elements.
On the bests of study of geochemical behavior of sin81e elements,the paper has established a mathematic model for linear relationships between elementS in the chemical sedimentary process of a semi-closed system:which is very similar to that of magmatic fractional crystallization (Wan Yusheng, 1990).In the formula, C C and C C represent the contents of elements x and y in original saturated solution and reSidual satuxated solution respectively, Dx and Dy are bulk distribution coefficentS of x and y ,Fi is reSidual ratio of saturated solution, and t is solute proPOrtion in saturated solution.Example shave also been given to show how to apply the method to research on saline sedimentation.Following are some main conclusions:1) The regression line representS the result of the linear regression of a cutve with lesscurvature.Foe an incompatible element-fair, the more similar the properties of two elements andthe smaller their bulk distribtition coefficientS are, the better the regresion line is.2)The nit6rcept and slope of the regression line have clearly geochemical significance.Both ofthem are constituted by the P8rametCrs C,C, Dx, Dy, t and Fl.If x and y are incompatible, then the slope of the line will be active and the line will intersect a relatively compatible element axis.When D values of x and y are similar, the intercept and slope of the regression line are close to zeroand C/C respectively.3)There could be different degrees of linear correlations between two elements of elementpair at different stages of evolution of the saline water, resulting from asynchronous variations ofthe bulk diStribution coefficients of the elements.And in different saline water systems, the sameelement-pairs can represent different degrees of linear correlations, so the chemical compositions of the systems will strongly influence the geochemical behaviors of the elements.
1995, 13(1): 133-141.
Abstract:
Wang Qi; Shi Jian; Wen Changqing;Ma Baoling(Lanzhou Institute of Geology, Chinese Acedemy of Sciences, 730000) Gas- bearing measure, defined as a complete series of rock assemblage which is favorable for the gas generation, is the geological base of discussing gas formation.It is mainly composed of source rock, reservior and cap rock.Source rock of gas can be generally divided into three types in terms of lithology: Pelite,carbonate and coal rock.According to pete types, gas reservior can be divided into primary POre-type, dissolution pore-type and fissure-type reservior.Generally, conditions of cap rock required for gas accumulation are extremely strict.Considering lithology, cap rOCk can be also divided into three types, that is, polite, gypsum rockand tight carbonate rock.Because of lithologic differences, gas-bearing measures can be classified into four assemblagetypes, namely, Pelite-Sandstone-Pelite, Pelite-limestone-Pelite, limestone-limestone-Pelite and limestone-limestone-gypsum.The assemblage type and distribution characteristics of gas-bearing measures are changed along with their geosraphic location and chronology.Formation of gas-bearing measure has a close relation to the depositional enviroment,ofwhich the most fayorabale one is generally thane sites with shallow water body, including bothmarine and continental factes tract.Sedimentary factes in favor of formation of gas-bearingmeasure in marine tract are as follows:1) coastal marsh coal-bearing elastic rock factes;2) tidal platform carbonate rock factes;dibsrrier platform carbonate-gypsum rock factes;②.confined platform carbonate rock factes;3) deep and shallow water open platform carbonate factesIn continental basins favorable enviroments include:1) semi-deep lacustrine to deep lacustrine elastic rock factes;2) shallow-lacustrine elastic rock factes;3) fluvial and lacustrine delta elastic rock fscies;4) fluvial and lake shore elastic rock factes.The most favorable depositional environments forming source, reservior and cap rock of gasbearing.measures are coastal marsh to shallow plate form in marine basin and the shallow lacustrinefactes in continental basin.In other words, formation of gas-bearing measure does not need deepwater environment, and shallow semi-reduced one is enough.Usually, gas-bearing measures arecompounds of different factes which overlapped and repeated to form complex rock assemblage andregular sequences.This is particularly necessary to the formation of gas source, reservior and caprock assemblage.The valuable formation procedure of three basic elements mentioned above is,firstly the formation of reservior,secondly cap rock and finally the evolution of organic matter insource rock.From the reseach of several cases, the procedure is considered as the most importantand decisive factor to the formation of gas field.
Wang Qi; Shi Jian; Wen Changqing;Ma Baoling(Lanzhou Institute of Geology, Chinese Acedemy of Sciences, 730000) Gas- bearing measure, defined as a complete series of rock assemblage which is favorable for the gas generation, is the geological base of discussing gas formation.It is mainly composed of source rock, reservior and cap rock.Source rock of gas can be generally divided into three types in terms of lithology: Pelite,carbonate and coal rock.According to pete types, gas reservior can be divided into primary POre-type, dissolution pore-type and fissure-type reservior.Generally, conditions of cap rock required for gas accumulation are extremely strict.Considering lithology, cap rOCk can be also divided into three types, that is, polite, gypsum rockand tight carbonate rock.Because of lithologic differences, gas-bearing measures can be classified into four assemblagetypes, namely, Pelite-Sandstone-Pelite, Pelite-limestone-Pelite, limestone-limestone-Pelite and limestone-limestone-gypsum.The assemblage type and distribution characteristics of gas-bearing measures are changed along with their geosraphic location and chronology.Formation of gas-bearing measure has a close relation to the depositional enviroment,ofwhich the most fayorabale one is generally thane sites with shallow water body, including bothmarine and continental factes tract.Sedimentary factes in favor of formation of gas-bearingmeasure in marine tract are as follows:1) coastal marsh coal-bearing elastic rock factes;2) tidal platform carbonate rock factes;dibsrrier platform carbonate-gypsum rock factes;②.confined platform carbonate rock factes;3) deep and shallow water open platform carbonate factesIn continental basins favorable enviroments include:1) semi-deep lacustrine to deep lacustrine elastic rock factes;2) shallow-lacustrine elastic rock factes;3) fluvial and lacustrine delta elastic rock fscies;4) fluvial and lake shore elastic rock factes.The most favorable depositional environments forming source, reservior and cap rock of gasbearing.measures are coastal marsh to shallow plate form in marine basin and the shallow lacustrinefactes in continental basin.In other words, formation of gas-bearing measure does not need deepwater environment, and shallow semi-reduced one is enough.Usually, gas-bearing measures arecompounds of different factes which overlapped and repeated to form complex rock assemblage andregular sequences.This is particularly necessary to the formation of gas source, reservior and caprock assemblage.The valuable formation procedure of three basic elements mentioned above is,firstly the formation of reservior,secondly cap rock and finally the evolution of organic matter insource rock.From the reseach of several cases, the procedure is considered as the most importantand decisive factor to the formation of gas field.
