The geochemical analysis and experimental simulation are comprehensively used to systematically study the hydrocarbon generation material,organic matter enrichment and hydrocarbon generation model of Paleogene source ...The geochemical analysis and experimental simulation are comprehensively used to systematically study the hydrocarbon generation material,organic matter enrichment and hydrocarbon generation model of Paleogene source rock in the Western Qaidam Depression,Qaidam Basin,NW China.Three main factors result in low TOC values of saline lacustrine source rock of the Qaidam Basin:relatively poor nutrient supply inhibits the algal bloom,too fast deposition rate causes the dilution of organic matter,and high organic matter conversion efficiency causes the low residual organic carbon.For this type of hydrogen-rich organic matter,due to the reduction of organic carbon during hydrocarbon generation,TOC needs to be restored based on maturity before evaluating organic matter abundance.The hydrocarbon generation of saline lacustrine source rocks of the Qaidam Basin is from two parts:soluble organic matter and insoluble organic matter.The soluble organic matter is inherited from organisms and preserved in saline lacustrine basins.It generates hydrocarbons during low-maturity stage,and the formed hydrocarbons are rich in complex compounds such as NOS,and undergo secondary cracking to form light components in the later stage;the hydrocarbon generation model of insoluble organic matter conforms to the traditional“Tissot”model,with an oil generation peak corresponding to Ro of 1.0%.展开更多
Based on the oil and gas exploration in western depression of the Qaidam Basin,NW China,combined with the geochemical,seismic,logging and drilling data,the basic geological conditions,oil and gas distribution characte...Based on the oil and gas exploration in western depression of the Qaidam Basin,NW China,combined with the geochemical,seismic,logging and drilling data,the basic geological conditions,oil and gas distribution characteristics,reservoir-forming dynamics,and hydrocarbon accumulation model of the Paleogene whole petroleum system(WPS)in the western depression of the Qaidam Basin are systematically studied.A globally unique ultra-thick mountain-style WPS is found in the western depression of the Qaidam Basin.Around the source rocks of the upper member of the Paleogene Lower Ganchaigou Formation,the structural reservoir,lithological reservoir,shale oil and shale gas are laterally distributed in an orderly manner and vertically overlapped from the edge to the central part of the lake basin.The Paleogene WPS in the western depression of the Qaidam Basin is believed unique in three aspects.First,the source rocks with low organic matter abundance are characterized by low carbon and rich hydrogen,showing a strong hydrocarbon generating capacity per unit mass of organic carbon.Second,the saline lake basinal deposits are ultra-thick,with mixed deposits dominating the center of the depression,and strong vertical and lateral heterogeneity of lithofacies and storage spaces.Third,the strong transformation induced by strike-slip compression during the Himalayan resulted in the heterogeneous enrichment of oil and gas in the mountain-style WPS.As a result of the coordinated evolution of source-reservoir-caprock assemblage and conducting system,the Paleogene WPS has the characteristics of“whole process”hydrocarbon generation of source rocks which are low-carbon and hydrogen-rich,“whole depression”ultra-thick reservoir sedimentation,“all direction”hydrocarbon adjustment by strike-slip compressional fault,and“whole succession”distribution of conventional and unconventional oil and gas.Due to the severe Himalayan tectonic movement,the western depression of the Qaidam Basin evolved from depression to uplift.Shale oil is widely distributed in the central lacustrine basin.In the sedimentary system thicker than 2000 m,oil and gas are continuous in the laminated limy-dolomites within the source rocks and the alga limestones neighboring the source kitchen,with intercrystalline pores,lamina fractures in dolomites and fault-dissolution bodies serving as the effective storage space.All these findings are helpful to supplement and expand the WPS theory in the continental lake basins in China,and provide theoretical guidance and technical support for oil and gas exploration in the Qaidam Basin.展开更多
基金Supported by the PetroChina Science and Technology Project(2021DJ1808).
文摘The geochemical analysis and experimental simulation are comprehensively used to systematically study the hydrocarbon generation material,organic matter enrichment and hydrocarbon generation model of Paleogene source rock in the Western Qaidam Depression,Qaidam Basin,NW China.Three main factors result in low TOC values of saline lacustrine source rock of the Qaidam Basin:relatively poor nutrient supply inhibits the algal bloom,too fast deposition rate causes the dilution of organic matter,and high organic matter conversion efficiency causes the low residual organic carbon.For this type of hydrogen-rich organic matter,due to the reduction of organic carbon during hydrocarbon generation,TOC needs to be restored based on maturity before evaluating organic matter abundance.The hydrocarbon generation of saline lacustrine source rocks of the Qaidam Basin is from two parts:soluble organic matter and insoluble organic matter.The soluble organic matter is inherited from organisms and preserved in saline lacustrine basins.It generates hydrocarbons during low-maturity stage,and the formed hydrocarbons are rich in complex compounds such as NOS,and undergo secondary cracking to form light components in the later stage;the hydrocarbon generation model of insoluble organic matter conforms to the traditional“Tissot”model,with an oil generation peak corresponding to Ro of 1.0%.
基金Supported by the PetroChina Science and Technology Special Project(2021DQ0405,2023ZZ15)National Natural Science Foundation of China(42090025)。
文摘Based on the oil and gas exploration in western depression of the Qaidam Basin,NW China,combined with the geochemical,seismic,logging and drilling data,the basic geological conditions,oil and gas distribution characteristics,reservoir-forming dynamics,and hydrocarbon accumulation model of the Paleogene whole petroleum system(WPS)in the western depression of the Qaidam Basin are systematically studied.A globally unique ultra-thick mountain-style WPS is found in the western depression of the Qaidam Basin.Around the source rocks of the upper member of the Paleogene Lower Ganchaigou Formation,the structural reservoir,lithological reservoir,shale oil and shale gas are laterally distributed in an orderly manner and vertically overlapped from the edge to the central part of the lake basin.The Paleogene WPS in the western depression of the Qaidam Basin is believed unique in three aspects.First,the source rocks with low organic matter abundance are characterized by low carbon and rich hydrogen,showing a strong hydrocarbon generating capacity per unit mass of organic carbon.Second,the saline lake basinal deposits are ultra-thick,with mixed deposits dominating the center of the depression,and strong vertical and lateral heterogeneity of lithofacies and storage spaces.Third,the strong transformation induced by strike-slip compression during the Himalayan resulted in the heterogeneous enrichment of oil and gas in the mountain-style WPS.As a result of the coordinated evolution of source-reservoir-caprock assemblage and conducting system,the Paleogene WPS has the characteristics of“whole process”hydrocarbon generation of source rocks which are low-carbon and hydrogen-rich,“whole depression”ultra-thick reservoir sedimentation,“all direction”hydrocarbon adjustment by strike-slip compressional fault,and“whole succession”distribution of conventional and unconventional oil and gas.Due to the severe Himalayan tectonic movement,the western depression of the Qaidam Basin evolved from depression to uplift.Shale oil is widely distributed in the central lacustrine basin.In the sedimentary system thicker than 2000 m,oil and gas are continuous in the laminated limy-dolomites within the source rocks and the alga limestones neighboring the source kitchen,with intercrystalline pores,lamina fractures in dolomites and fault-dissolution bodies serving as the effective storage space.All these findings are helpful to supplement and expand the WPS theory in the continental lake basins in China,and provide theoretical guidance and technical support for oil and gas exploration in the Qaidam Basin.
