Reservoirs in the Xing＇anling Group in the Suderte Oil Field,Hailar Basin exhibit ultra-low to low permeability and high tuffaceous material content.This study comprehensively analyzed diagenesis and quality evolutio...Reservoirs in the Xing＇anling Group in the Suderte Oil Field,Hailar Basin exhibit ultra-low to low permeability and high tuffaceous material content.This study comprehensively analyzed diagenesis and quality evolution of these low-permeability reservoirs using thin sections,SEM samples,rock physical properties,pore water data,as well as geochemical numerical simulations.Calcite and analcite are the two main types of cements precipitated in the eodiagenetic stage at shallow burial depths in the reservoirs.These two cements occupied significant primary intergranular pores and effectively retarded deep burial compaction.Petrography textures suggest selective dissolution of massive analcite and little dissolution of calcite in the mesodiagenetic stage.Chemical calculations utilizing the Geochemist＇s Workbench 9.0indicated that the equilibrium constant of the calcite leaching reaction is significantly smaller than that of the analcite leaching reaction,resulting in extensive dissolution of analcite rather than calcite in the geochemical system with both minerals present.Numerical simulations with constraints of kinetics and pore water chemistry demonstrated that the pore water in the Xing＇anling group is saturated with respect to calcite,but undersaturated with analcite,leading to dissolution of large amounts of analcite and no dissolution of calcite.Significant secondary intergranular pores have formed in analcite-cemented reservoirs from selective dissolution of analcite in the mesodiagenetic stage;the analcite dissolution formed preferential flow paths in the reservoirs,which promoted feldspar dissolution;and dissolution of such minerals led to the present reservoirs with medium porosity and low permeability.Calcite-cemented tight reservoirs have not experienced extensive dissolution of cements,so they exhibit ultra-low porosity and permeability.展开更多
The positive structure belts surrounding the Taibei Sag,Turpan-Hami Basin,have been the main targets for oil and gas exploration for years and are now left with remaining resources scattering in reservoirs adjacent to...The positive structure belts surrounding the Taibei Sag,Turpan-Hami Basin,have been the main targets for oil and gas exploration for years and are now left with remaining resources scattering in reservoirs adjacent to source rocks in the sag,where the Shuixigou Group with substantial oil and gas potential constitutes the primary focus for near-source exploration.Consequently,characterization of development and key controlling factors of reservoir space becomes a must for future exploration in the area.This study investigates the development traits,genesis,and controlling factors of the Xishanyao and Sangonghe formations in the Shengbei and Qiudong Sub-sags of the Taibei Sag with techniques such as cast thin-section observation,porosity and permeability tests,high-pressure mercury injection,and saturation fluid NMR analysis of reservoir rocks.The findings reveal that the Shuixigou Group in the Taibei Sag consists of lithic sandstone.Reservoirs in the group are mostly poor in terms of physical properties,with undeveloped primary pores dominated by intergranular dissolved pores as a result of a strong compaction.Comparative analysis of key controlling factors of the Sangonghe Formation reveals significant distinctions in sandstone particle size,sand body thickness,genesis and distribution,provenance location,and source rock type between the Qiudong area and Shengbei area.Vertically,the coal seams of the Xishanyao Formation exhibit heightened development with shallower burial depth and lower maturity compared to those of the Sangonghe Formation.Consequently,this environment fosters the formation of organic acids,which have a stronger dissolution effect on minerals to develop secondary dissolution pores,and ultimately resulting in better reservoir physical properties.Overall,the reservoirs within the Qiudong area of the Taibei Sag demonstrate superior characteristics compared to those in the Shengbei area.Furthermore,the reservoir physical properties of the Xishanyao Formation are better than those of the Sangonghe Formation.The research findings will provide valuable guidance for the exploration and development of lithological oil and gas reservoirs within the Taibei Sag.展开更多
Based on a large number of field outcrops and cores taken systematically from boreholes,by microscopic observa-tion,physical property analysis,mineralogy analysis,geochemical analysis etc.,reservoir characteristics of...Based on a large number of field outcrops and cores taken systematically from boreholes,by microscopic observa-tion,physical property analysis,mineralogy analysis,geochemical analysis etc.,reservoir characteristics of the first member of Middle Permian Maokou Formation in Sichuan Basin("Mao 1 Me mber"for short)are analyzed.(1)Rhythmic limestone-marl reservoirs of this member mostly exist in marl layers are a set of tight carbonate fracture-pore type reservoir with low porosity and low permeability,with multiple types of storage space,mainly secondary dissolution pores and fissures of clay minerals.(2)The clay minerals are mainly diagenetic clay minerals,such as sepiolite,talc and their intermediate products,aliettite,with hardly terrigenous clay minerals,and the reservoir in different regions have significant differences in the types of clay minerals.(3)The formation of high quality tight carbonate reservoir with limestone-marl interbeds is related to the differential diagene-sis in the early seawater burial stage and the exposure karstification in the early diagenetic stage.It is inferred through th e study that the inner ramp of southwestern Sichuan Basin is more likely to have sweet spots with high production,while the outer ramp in eastern Sichuan Basin is more likely to have large scale contiguous reservoir with low production.展开更多
基金financially supported by the National Science and Technology Special Grant (No. 2011ZX05009003)China Postdoctoral Science Fund (2015M580617)+1 种基金Shandong Postdoctoral Innovation Fund (201502028)2014 Innovation Project of China University of Petroleum (YCX2014002)
文摘Reservoirs in the Xing＇anling Group in the Suderte Oil Field,Hailar Basin exhibit ultra-low to low permeability and high tuffaceous material content.This study comprehensively analyzed diagenesis and quality evolution of these low-permeability reservoirs using thin sections,SEM samples,rock physical properties,pore water data,as well as geochemical numerical simulations.Calcite and analcite are the two main types of cements precipitated in the eodiagenetic stage at shallow burial depths in the reservoirs.These two cements occupied significant primary intergranular pores and effectively retarded deep burial compaction.Petrography textures suggest selective dissolution of massive analcite and little dissolution of calcite in the mesodiagenetic stage.Chemical calculations utilizing the Geochemist＇s Workbench 9.0indicated that the equilibrium constant of the calcite leaching reaction is significantly smaller than that of the analcite leaching reaction,resulting in extensive dissolution of analcite rather than calcite in the geochemical system with both minerals present.Numerical simulations with constraints of kinetics and pore water chemistry demonstrated that the pore water in the Xing＇anling group is saturated with respect to calcite,but undersaturated with analcite,leading to dissolution of large amounts of analcite and no dissolution of calcite.Significant secondary intergranular pores have formed in analcite-cemented reservoirs from selective dissolution of analcite in the mesodiagenetic stage;the analcite dissolution formed preferential flow paths in the reservoirs,which promoted feldspar dissolution;and dissolution of such minerals led to the present reservoirs with medium porosity and low permeability.Calcite-cemented tight reservoirs have not experienced extensive dissolution of cements,so they exhibit ultra-low porosity and permeability.
基金funded by the National Natural Science Foundation of China(No.U22B6002)the“14th Five-Year”Forward-looking Basic Science and Technology Project of China National Petroleum Company Limited(No.2022DJ2107).
文摘The positive structure belts surrounding the Taibei Sag,Turpan-Hami Basin,have been the main targets for oil and gas exploration for years and are now left with remaining resources scattering in reservoirs adjacent to source rocks in the sag,where the Shuixigou Group with substantial oil and gas potential constitutes the primary focus for near-source exploration.Consequently,characterization of development and key controlling factors of reservoir space becomes a must for future exploration in the area.This study investigates the development traits,genesis,and controlling factors of the Xishanyao and Sangonghe formations in the Shengbei and Qiudong Sub-sags of the Taibei Sag with techniques such as cast thin-section observation,porosity and permeability tests,high-pressure mercury injection,and saturation fluid NMR analysis of reservoir rocks.The findings reveal that the Shuixigou Group in the Taibei Sag consists of lithic sandstone.Reservoirs in the group are mostly poor in terms of physical properties,with undeveloped primary pores dominated by intergranular dissolved pores as a result of a strong compaction.Comparative analysis of key controlling factors of the Sangonghe Formation reveals significant distinctions in sandstone particle size,sand body thickness,genesis and distribution,provenance location,and source rock type between the Qiudong area and Shengbei area.Vertically,the coal seams of the Xishanyao Formation exhibit heightened development with shallower burial depth and lower maturity compared to those of the Sangonghe Formation.Consequently,this environment fosters the formation of organic acids,which have a stronger dissolution effect on minerals to develop secondary dissolution pores,and ultimately resulting in better reservoir physical properties.Overall,the reservoirs within the Qiudong area of the Taibei Sag demonstrate superior characteristics compared to those in the Shengbei area.Furthermore,the reservoir physical properties of the Xishanyao Formation are better than those of the Sangonghe Formation.The research findings will provide valuable guidance for the exploration and development of lithological oil and gas reservoirs within the Taibei Sag.
基金Supported by the Scientific and Technological Research Projects of Sinopec(P20059-3)Scientific and Technological Research Projects of Southwest Branch Company(KJ-633-2103).
文摘Based on a large number of field outcrops and cores taken systematically from boreholes,by microscopic observa-tion,physical property analysis,mineralogy analysis,geochemical analysis etc.,reservoir characteristics of the first member of Middle Permian Maokou Formation in Sichuan Basin("Mao 1 Me mber"for short)are analyzed.(1)Rhythmic limestone-marl reservoirs of this member mostly exist in marl layers are a set of tight carbonate fracture-pore type reservoir with low porosity and low permeability,with multiple types of storage space,mainly secondary dissolution pores and fissures of clay minerals.(2)The clay minerals are mainly diagenetic clay minerals,such as sepiolite,talc and their intermediate products,aliettite,with hardly terrigenous clay minerals,and the reservoir in different regions have significant differences in the types of clay minerals.(3)The formation of high quality tight carbonate reservoir with limestone-marl interbeds is related to the differential diagene-sis in the early seawater burial stage and the exposure karstification in the early diagenetic stage.It is inferred through th e study that the inner ramp of southwestern Sichuan Basin is more likely to have sweet spots with high production,while the outer ramp in eastern Sichuan Basin is more likely to have large scale contiguous reservoir with low production.
