Due to limited data on the geochemical properties of natural gas,estimations are needed for the effective gas source rock in evaluating gas potential.However,the pronounced heterogeneity of mudstones in lacustrine suc...Due to limited data on the geochemical properties of natural gas,estimations are needed for the effective gas source rock in evaluating gas potential.However,the pronounced heterogeneity of mudstones in lacustrine successions complicates the prediction of the presence and geochemical characteristics of gas source rocks.In this paper,the Liaohe Subbasin of Northeast China is used as an example to construct a practical methodology for locating effective gas source rocks in typical lacustrine basins.Three types of gas source rocks,microbial,oil-type,and coal-type,were distinguished according to the different genetic types of their natural gas.A practical three-dimensional geological model was developed,refined,and applied to determine the spatial distribution of the mudstones in the Western Depression of the Liaohe Subbasin and to describe the geochemical characteristics(the abundance,type,and maturation levels of the organic matter).Application of the model in the subbasin indicates that the sedimentary facies have led to heterogeneity in the mudstones,particularly with respect to organic matter types.The effective gas source rock model constructed for the Western Depression shows that the upper sequence(SQ2)of the Fourth member(Mbr 4)of the Eocene Shahejie Formation(Fm)and the lower and middle sequences(SQ3 and SQ4)of the Third member(Mbr 3)form the principal gas-generating interval.The total volume of effective gas source rocks is estimated to be 586 km^(3).The effective microbial,oil-type,and coal-type gas source rocks are primarily found in the shallow western slope,the central sags,and the eastern slope of the Western Depression,respectively.This study provides a practical approach for more accurately identifying the occurrence and geochemical characteristics of effective natural gas source rocks,enabling a precise quantitative estimation of natural gas reserves.展开更多
Hydrocarbon expulsion occurs only when pore fluid pressure due to hydrocarbon generation in source rock exceeds the force against migration in the adjacent carrier beds.Taking the Middle-Upper Ordovician carbonate sou...Hydrocarbon expulsion occurs only when pore fluid pressure due to hydrocarbon generation in source rock exceeds the force against migration in the adjacent carrier beds.Taking the Middle-Upper Ordovician carbonate source rock of Tarim Basin in China as an example,this paper proposes a method that identifies effective carbonate source rock based on the principles of mass balance.Data from the Well YW2 indicate that the Middle Ordovician Yijianfang Formation contains effective carbonate source rocks with low present-day TOC.Geological and geochemical analysis suggests that the hydrocarbons in the carbonate interval are likely self-generated and retained.Regular steranes from GC-MS analysis of oil extracts in this interval display similar features to those of the crude oil samples in Tabei area,indicating that the crude oil probably was migrated from the effective source rocks.By applying to other wells in the basin,the identified effective carbonate source rocks and non-source rock carbonates can be effectively identified and consistent with the actual exploration results,validating the method.Considering the contribution from the identified effective source rocks with low present-day TOC(TOC_(pd))is considered,the long-standing puzzle between the proved 3 P oil reserves and estimated resources in the basin can be reasonably explained.展开更多
There have been different views on the origins of gas reservoirs of Ordovician Majiagou Fm in the Ordos Basin,but none of them supports the opinion that there are scale source rocks(TOC>0.5%)in the Majiagou Fm.In t...There have been different views on the origins of gas reservoirs of Ordovician Majiagou Fm in the Ordos Basin,but none of them supports the opinion that there are scale source rocks(TOC>0.5%)in the Majiagou Fm.In this paper,a series of analysis was made on cores and cutting samples taken from recent newly-drilled wells in the Ordovician reservoirs in the centraleeastern areas of the Ordos Basin.Accordingly,the organic abundance features of different types of source rocks in the Majiagou Fm were presented,and for the first time,it was discovered and verified that there are effective scale source rocks with high organic abundance.Based on these analysis and studies,the following results were achieved.First,the effective source rocks of Majiagou Fm are composed of thinethick layered dark dolomite-bearing mudstones,dolomitic mudstones and argillaceous dolomites,and their enrichment and distribution are obviously controlled by sedimentary facies.During the sedimentation of Majiagou Fm,the effective scale source rocks developed better at the regressive stage than at the transgressive stage.The effective source rocks are primarily distributed in the upper part of Ma 5 Member(especially concentrated in the third and fourth sub-members)and secondly in Ma 3 Member,Ma 1 Member and the middleelower part of Ma 5 Member.Second,the effective source rocks are areally distributed in a dual-girdle form around the Mizhi Salt Depression,and those in the secondary depressions are mediumethick layered,with a large total thickness and high organic abundance.Third,the effective source rocks in the center of Mizhi Depression and the secondary uplifts are thin-layered,with a small total thickness and low organic abundance.And fourth,the organic abundance of the effective source rocks varies from 0.30% to 8.45%.Phytoplankton and Acritarchs are the main parent materials of hydrocarbon,and organic matters are of sapropel or sapropel prone type.To sum up,the Ordovician effective source rocks in the Ordos Basin are generally at an over-mature stage and they contribute greatly to the natural gas in the Majiagou Fm.In these effective source rocks,dry gas is mainly generated at a high rate.展开更多
Objective The distribution characteristics and formation mechanism of rearranged hopanes in hydrocarbon source rocks are affected by various geological conditions.Among these geological conditions,thermal action has a...Objective The distribution characteristics and formation mechanism of rearranged hopanes in hydrocarbon source rocks are affected by various geological conditions.Among these geological conditions,thermal action has an important influence on the formation of rearranged hopanes,which has been however little documented previously.展开更多
The present paper mainly studies the petroleum system of the Sufyan Depression in the Muglad Basin of central Africa and analyzes its control of hydrocarbon accumulation. On the basis of comprehensive analysis of effe...The present paper mainly studies the petroleum system of the Sufyan Depression in the Muglad Basin of central Africa and analyzes its control of hydrocarbon accumulation. On the basis of comprehensive analysis of effective source rock, reservoir bed types and source-reservoir-seal assemblages, petroleum system theory has been used to classify the petroleum system of the Sufyan Depression. Vertically, the Sufyan Depression consists of two subsystems. One is an Abu Gabra subsystem as a self generating, accumulating and sealing assemblage. The other subsystem is composed of an Abu Gabra source rock, Bentiu channel sandstone reservoir and Darfur group shale seal, which is a prolific assemblage in this area. Laterally, the Sufyan Depression is divided into eastern and western parts with separate hydrocarbon generation centers more than 10 000 m deep. The potential of the petroleum system is tremendous. Recently, there has been a great breakthrough in exploration. The Sufyan C-1 well drilled in the central structural belt obtained high-yielding oil flow exceeding 100 tons per day and controlled geologic reserves of tens of millions of tons. The total resource potential of the Sufyan Depression is considerable. The central structural belt is most favorable as an exploration and development prospect.展开更多
文摘Due to limited data on the geochemical properties of natural gas,estimations are needed for the effective gas source rock in evaluating gas potential.However,the pronounced heterogeneity of mudstones in lacustrine successions complicates the prediction of the presence and geochemical characteristics of gas source rocks.In this paper,the Liaohe Subbasin of Northeast China is used as an example to construct a practical methodology for locating effective gas source rocks in typical lacustrine basins.Three types of gas source rocks,microbial,oil-type,and coal-type,were distinguished according to the different genetic types of their natural gas.A practical three-dimensional geological model was developed,refined,and applied to determine the spatial distribution of the mudstones in the Western Depression of the Liaohe Subbasin and to describe the geochemical characteristics(the abundance,type,and maturation levels of the organic matter).Application of the model in the subbasin indicates that the sedimentary facies have led to heterogeneity in the mudstones,particularly with respect to organic matter types.The effective gas source rock model constructed for the Western Depression shows that the upper sequence(SQ2)of the Fourth member(Mbr 4)of the Eocene Shahejie Formation(Fm)and the lower and middle sequences(SQ3 and SQ4)of the Third member(Mbr 3)form the principal gas-generating interval.The total volume of effective gas source rocks is estimated to be 586 km^(3).The effective microbial,oil-type,and coal-type gas source rocks are primarily found in the shallow western slope,the central sags,and the eastern slope of the Western Depression,respectively.This study provides a practical approach for more accurately identifying the occurrence and geochemical characteristics of effective natural gas source rocks,enabling a precise quantitative estimation of natural gas reserves.
基金financially supported by the Science Foundation of China University of Petroleum,Beijing(Grant No.2462020BJRC005)the Joint Funds of National Natural Science Foundation of China(Grant No.U19B6003-02)。
文摘Hydrocarbon expulsion occurs only when pore fluid pressure due to hydrocarbon generation in source rock exceeds the force against migration in the adjacent carrier beds.Taking the Middle-Upper Ordovician carbonate source rock of Tarim Basin in China as an example,this paper proposes a method that identifies effective carbonate source rock based on the principles of mass balance.Data from the Well YW2 indicate that the Middle Ordovician Yijianfang Formation contains effective carbonate source rocks with low present-day TOC.Geological and geochemical analysis suggests that the hydrocarbons in the carbonate interval are likely self-generated and retained.Regular steranes from GC-MS analysis of oil extracts in this interval display similar features to those of the crude oil samples in Tabei area,indicating that the crude oil probably was migrated from the effective source rocks.By applying to other wells in the basin,the identified effective carbonate source rocks and non-source rock carbonates can be effectively identified and consistent with the actual exploration results,validating the method.Considering the contribution from the identified effective source rocks with low present-day TOC(TOC_(pd))is considered,the long-standing puzzle between the proved 3 P oil reserves and estimated resources in the basin can be reasonably explained.
基金Project supported by the S&T Project of PetroChina Exploration&Production Company“Evaluation on Ordovician source rocks in the Ordos Basin”(No.:2012-011)“Characteristics and comprehensive evaluation of Ordovician gas sources and optimization of favorable zones in the Ordos Basin”(No.:2014-008).
文摘There have been different views on the origins of gas reservoirs of Ordovician Majiagou Fm in the Ordos Basin,but none of them supports the opinion that there are scale source rocks(TOC>0.5%)in the Majiagou Fm.In this paper,a series of analysis was made on cores and cutting samples taken from recent newly-drilled wells in the Ordovician reservoirs in the centraleeastern areas of the Ordos Basin.Accordingly,the organic abundance features of different types of source rocks in the Majiagou Fm were presented,and for the first time,it was discovered and verified that there are effective scale source rocks with high organic abundance.Based on these analysis and studies,the following results were achieved.First,the effective source rocks of Majiagou Fm are composed of thinethick layered dark dolomite-bearing mudstones,dolomitic mudstones and argillaceous dolomites,and their enrichment and distribution are obviously controlled by sedimentary facies.During the sedimentation of Majiagou Fm,the effective scale source rocks developed better at the regressive stage than at the transgressive stage.The effective source rocks are primarily distributed in the upper part of Ma 5 Member(especially concentrated in the third and fourth sub-members)and secondly in Ma 3 Member,Ma 1 Member and the middleelower part of Ma 5 Member.Second,the effective source rocks are areally distributed in a dual-girdle form around the Mizhi Salt Depression,and those in the secondary depressions are mediumethick layered,with a large total thickness and high organic abundance.Third,the effective source rocks in the center of Mizhi Depression and the secondary uplifts are thin-layered,with a small total thickness and low organic abundance.And fourth,the organic abundance of the effective source rocks varies from 0.30% to 8.45%.Phytoplankton and Acritarchs are the main parent materials of hydrocarbon,and organic matters are of sapropel or sapropel prone type.To sum up,the Ordovician effective source rocks in the Ordos Basin are generally at an over-mature stage and they contribute greatly to the natural gas in the Majiagou Fm.In these effective source rocks,dry gas is mainly generated at a high rate.
基金supported by the National Natural Science Foundation of China (grant No.41272170)the National Oil and Gas Major Project (grant No.2016ZX05007-001)
文摘Objective The distribution characteristics and formation mechanism of rearranged hopanes in hydrocarbon source rocks are affected by various geological conditions.Among these geological conditions,thermal action has an important influence on the formation of rearranged hopanes,which has been however little documented previously.
基金supported by the CNPC Science and Technology Study Financing Project (EDR/CN-01-102)
文摘The present paper mainly studies the petroleum system of the Sufyan Depression in the Muglad Basin of central Africa and analyzes its control of hydrocarbon accumulation. On the basis of comprehensive analysis of effective source rock, reservoir bed types and source-reservoir-seal assemblages, petroleum system theory has been used to classify the petroleum system of the Sufyan Depression. Vertically, the Sufyan Depression consists of two subsystems. One is an Abu Gabra subsystem as a self generating, accumulating and sealing assemblage. The other subsystem is composed of an Abu Gabra source rock, Bentiu channel sandstone reservoir and Darfur group shale seal, which is a prolific assemblage in this area. Laterally, the Sufyan Depression is divided into eastern and western parts with separate hydrocarbon generation centers more than 10 000 m deep. The potential of the petroleum system is tremendous. Recently, there has been a great breakthrough in exploration. The Sufyan C-1 well drilled in the central structural belt obtained high-yielding oil flow exceeding 100 tons per day and controlled geologic reserves of tens of millions of tons. The total resource potential of the Sufyan Depression is considerable. The central structural belt is most favorable as an exploration and development prospect.
