Objective At present, there is controversy regarding the existence of marine-terrestrial transitional facies that can act as a source of shale gas. This detailed study of Carboniferous-Permian age geological data from...Objective At present, there is controversy regarding the existence of marine-terrestrial transitional facies that can act as a source of shale gas. This detailed study of Carboniferous-Permian age geological data from the northern Shaanxi area （China） provides new insight for this type of shale gas. In addition, a new deposition and accumulation pattern for this type of shale gas is established.展开更多
Based on core description,thin section identification,X-ray diffraction analysis,scanning electron microscopy,low-temperature gas adsorption and high-pressure mercury intrusion porosimetry,the shale lithofacies of Sha...Based on core description,thin section identification,X-ray diffraction analysis,scanning electron microscopy,low-temperature gas adsorption and high-pressure mercury intrusion porosimetry,the shale lithofacies of Shan23 sub-member of Permian Shanxi Formation in the east margin of Ordos Basin was systematically analyzed in this study.The Shan23 sub-member has six lithofacies,namely,low TOC clay shale(C-L),low TOC siliceous shale(S-L),medium TOC siliceous shale(S-M),medium TOC hybrid shale(M-M),high TOC siliceous shale(S-H),and high TOC clay shale(C-H).Among them,S-H is the best lithofacies,S-M and M-M are the second best.The C-L and C-H lithofacies,mainly found in the upper part of Shan23 sub-member,generally developed in tide-dominated delta facies;the S-L,S-M,S-H and M-M shales occurring in the lower part of Shan23 sub-member developed in tide-dominated estuarine bay facies.The S-H,S-M and M-M shales have good pore struc-ture and largely organic matter pores and mineral interparticle pores,including interlayer pore in clay minerals,pyrite inter-crystalline pore,and mineral dissolution pore.C-L and S-L shales have mainly mineral interparticle pores and clay mineral in-terlayer pores,and a small amount of organic matter pores,showing poorer pore structure.The C-H shale has organic mi-cro-pores and a small number of interlayer fissures of clay minerals,showing good micro-pore structure,and poor meso-pore and macro-pore structure.The formation of favorable lithofacies is jointly controlled by depositional environment and diagen-esis.Shallow bay-lagoon depositional environment is conducive to the formation of type II2 kerogen which can produce a large number of organic cellular pores.Besides,the rich biogenic silica is conducive to the preservation of primary pores and en-hances the fracability of the shale reservoir.展开更多
China is highly dependent on foreign oil and gas,and the exploration and exploitation of shale gas is an important way to alleviate the energy and environmental pressure of China.Although a series of significant progr...China is highly dependent on foreign oil and gas,and the exploration and exploitation of shale gas is an important way to alleviate the energy and environmental pressure of China.Although a series of significant progress has been made in a short time,China is still at the crossroads of shale gas exploration direction.Therefore,this paper systematically reviews the particularity of shale gas geological conditions in China,and points out China's exploration direction of shale gas in different fields combined with the research achievements of shale gas accumulation mechanism.The following results were obtained.(1)China's shale gas exploration fields can be divided into three major parts,i.e.,marine,continental and marineecontinental transitional facies.The geological characteristics of shale gas in North China,Yangtze and Tarim plates are different.The interaction of multiple factors,including tectonic and sedimentary evolution,shale gas accumulation,late-stage transformation and etc.,has led the complexity of the geological distribution and the diversity of exploration fields of shale gas in China.(2)The organic pores and fractures of marine shale are developed.The Ordovician Wufeng-Silurian Longmaxi Formation will still be the primary target of shale gas exploration in future.Meanwhile,the Cambrian Niutitang and Sinian Doushantuo Formation in the Yangtze region,the Devonian Luofu and Carboniferous Jiusi Formation in the Yunnan-Guizhou-Guangxi region,the Jixianian Hongshuizhuang and Mesoproterozoic Xiamaling Formation will be the targets of strategic breakthrough in shale gas exploration.(3)The structural deep and slope of middle-large basins and the sedimentation centers of small-middle basins are the main directions of continental shale gas exploration.Inter-laminar cracks and intergranular pores are well developed in continental shale.The coupling of various organic matter types and thermal evolution results in the symbiosis of shale oil and shale gas,which will become an important field for further exploration of continental shale gas.(4)The marineecontinental transitional shale,which mainly formed in Late Carboniferous-Permian,is characterized by cyclic association with sandstone,mudstone,coal and carbonate.Diagenetic fractures are well developed in transitional shale.The favorable structural and diagenetic preservation are the two major factors for the enrichment of this type of shale gas.The flat-lagoon and delta sedimentary systems,middle-large superimposed and smallmiddle residual basins,and deep layers with quality caprock and good structural preservation are the favorable directions for shale gas exploration in transitional facies.展开更多
The Sichuan Basin is rich in shale oil and gas resources,with favorable geological conditions that the other shale reservoirs in China cannot match.Thus,the basin is an ideal option for fully"exploring petroleum ...The Sichuan Basin is rich in shale oil and gas resources,with favorable geological conditions that the other shale reservoirs in China cannot match.Thus,the basin is an ideal option for fully"exploring petroleum inside source kitchen"with respect to onshore shale oil and gas in China.This paper analyzes the characteristics of shale oil and gas resources in the United States and China,and points out that maturity plays an important role in controlling shale oil and gas composition.US shale oil and gas exhibit high proportions of light hydrocarbon and wet gas,whereas Chinese marine and transitional shale gas is mainly dry gas and continental shale oil is generally heavy.A comprehensive geological study of shale oil and gas in the Sichuan Basin reveals findings with respect to the following three aspects.First,there are multiple sets of organic-rich shale reservoirs of three types in the basin,such as the Cambrian Qiongzhusi Formation and Ordovician Wufeng Formation-Silurian Longmaxi Formation marine shale,Permian Longtan Formation transitional shale,Triassic Xujiahe Formation lake-swamp shale,and Jurassic lacustrine shale.Marine shale gas enrichment is mainly controlled by four elements:Deep-water shelf facies,moderate thermal evolution,calcium-rich and silicon-rich rock association,and closed roof/floor.Second,the"sweet section"is generally characterized by high total organic carbon,high gas content,large porosity,high brittle minerals content,high formation pressure,and the presence of lamellation/bedding and natural microfractures.Moreover,the"sweet area"is generally characterized by very thick organic-rich shale,moderate thermal evolution,good preservation conditions,and shallow burial depth,which are exemplified by the shale oil and gas in the Wufeng-Longmaxi Formation,Longtan Formation,and Daanzhai Member of the Ziliujing Formation.Third,the marine,transitional,and continental shale oil and gas resources in the Sichuan Basin account for 50%,25%,and 30%of the respective types of shale oil and gas geological resources in China,with great potential to become the cradle of the shale oil and gas industrial revolution in China.Following the"Conventional Daqing-Oil"(i.e.,the Daqing oilfield in the Songliao Basin)and the"Western Daqing-Oil&Gas"(i.e.,the Changqing oilfield in the Ordos Basin),the Southwest oil and gas field in the Sichuan Basin is expected to be built into a"Sichuan-Chongqing Daqing-Gas"in China.展开更多
基金funded by the Geological Survey Project of China Geological Survey(No.1212011085516)Geological Survey Level 2 Project(No.121201103000150011)Basic Research Professional Expenses of CAGS(No. YYWF201609)
文摘Objective At present, there is controversy regarding the existence of marine-terrestrial transitional facies that can act as a source of shale gas. This detailed study of Carboniferous-Permian age geological data from the northern Shaanxi area （China） provides new insight for this type of shale gas. In addition, a new deposition and accumulation pattern for this type of shale gas is established.
基金China National Science and Technology Major Project(2017ZX05035).
文摘Based on core description,thin section identification,X-ray diffraction analysis,scanning electron microscopy,low-temperature gas adsorption and high-pressure mercury intrusion porosimetry,the shale lithofacies of Shan23 sub-member of Permian Shanxi Formation in the east margin of Ordos Basin was systematically analyzed in this study.The Shan23 sub-member has six lithofacies,namely,low TOC clay shale(C-L),low TOC siliceous shale(S-L),medium TOC siliceous shale(S-M),medium TOC hybrid shale(M-M),high TOC siliceous shale(S-H),and high TOC clay shale(C-H).Among them,S-H is the best lithofacies,S-M and M-M are the second best.The C-L and C-H lithofacies,mainly found in the upper part of Shan23 sub-member,generally developed in tide-dominated delta facies;the S-L,S-M,S-H and M-M shales occurring in the lower part of Shan23 sub-member developed in tide-dominated estuarine bay facies.The S-H,S-M and M-M shales have good pore struc-ture and largely organic matter pores and mineral interparticle pores,including interlayer pore in clay minerals,pyrite inter-crystalline pore,and mineral dissolution pore.C-L and S-L shales have mainly mineral interparticle pores and clay mineral in-terlayer pores,and a small amount of organic matter pores,showing poorer pore structure.The C-H shale has organic mi-cro-pores and a small number of interlayer fissures of clay minerals,showing good micro-pore structure,and poor meso-pore and macro-pore structure.The formation of favorable lithofacies is jointly controlled by depositional environment and diagen-esis.Shallow bay-lagoon depositional environment is conducive to the formation of type II2 kerogen which can produce a large number of organic cellular pores.Besides,the rich biogenic silica is conducive to the preservation of primary pores and en-hances the fracability of the shale reservoir.
基金Project supported by the National Natural Science Foundation of China“Key Parameter Test and Intelligent Evaluation System for Gas-bearing Shale”(No.41927801)“Genetic mechanism of pyrite and its Significance in Diagenetic Environment in the Niutitang Formation Shale in the Cengong Block of Guizhou”(No.42002156)Major Scientific and Technological Project of Henan Province“Henan Shale Gas Exploration and Development and Demonstration Application Research”(No.151100311000).
文摘China is highly dependent on foreign oil and gas,and the exploration and exploitation of shale gas is an important way to alleviate the energy and environmental pressure of China.Although a series of significant progress has been made in a short time,China is still at the crossroads of shale gas exploration direction.Therefore,this paper systematically reviews the particularity of shale gas geological conditions in China,and points out China's exploration direction of shale gas in different fields combined with the research achievements of shale gas accumulation mechanism.The following results were obtained.(1)China's shale gas exploration fields can be divided into three major parts,i.e.,marine,continental and marineecontinental transitional facies.The geological characteristics of shale gas in North China,Yangtze and Tarim plates are different.The interaction of multiple factors,including tectonic and sedimentary evolution,shale gas accumulation,late-stage transformation and etc.,has led the complexity of the geological distribution and the diversity of exploration fields of shale gas in China.(2)The organic pores and fractures of marine shale are developed.The Ordovician Wufeng-Silurian Longmaxi Formation will still be the primary target of shale gas exploration in future.Meanwhile,the Cambrian Niutitang and Sinian Doushantuo Formation in the Yangtze region,the Devonian Luofu and Carboniferous Jiusi Formation in the Yunnan-Guizhou-Guangxi region,the Jixianian Hongshuizhuang and Mesoproterozoic Xiamaling Formation will be the targets of strategic breakthrough in shale gas exploration.(3)The structural deep and slope of middle-large basins and the sedimentation centers of small-middle basins are the main directions of continental shale gas exploration.Inter-laminar cracks and intergranular pores are well developed in continental shale.The coupling of various organic matter types and thermal evolution results in the symbiosis of shale oil and shale gas,which will become an important field for further exploration of continental shale gas.(4)The marineecontinental transitional shale,which mainly formed in Late Carboniferous-Permian,is characterized by cyclic association with sandstone,mudstone,coal and carbonate.Diagenetic fractures are well developed in transitional shale.The favorable structural and diagenetic preservation are the two major factors for the enrichment of this type of shale gas.The flat-lagoon and delta sedimentary systems,middle-large superimposed and smallmiddle residual basins,and deep layers with quality caprock and good structural preservation are the favorable directions for shale gas exploration in transitional facies.
基金supported by the National Oil and Gas Major Project(Grant Nos.2017ZX05035&2016ZX05046)。
文摘The Sichuan Basin is rich in shale oil and gas resources,with favorable geological conditions that the other shale reservoirs in China cannot match.Thus,the basin is an ideal option for fully"exploring petroleum inside source kitchen"with respect to onshore shale oil and gas in China.This paper analyzes the characteristics of shale oil and gas resources in the United States and China,and points out that maturity plays an important role in controlling shale oil and gas composition.US shale oil and gas exhibit high proportions of light hydrocarbon and wet gas,whereas Chinese marine and transitional shale gas is mainly dry gas and continental shale oil is generally heavy.A comprehensive geological study of shale oil and gas in the Sichuan Basin reveals findings with respect to the following three aspects.First,there are multiple sets of organic-rich shale reservoirs of three types in the basin,such as the Cambrian Qiongzhusi Formation and Ordovician Wufeng Formation-Silurian Longmaxi Formation marine shale,Permian Longtan Formation transitional shale,Triassic Xujiahe Formation lake-swamp shale,and Jurassic lacustrine shale.Marine shale gas enrichment is mainly controlled by four elements:Deep-water shelf facies,moderate thermal evolution,calcium-rich and silicon-rich rock association,and closed roof/floor.Second,the"sweet section"is generally characterized by high total organic carbon,high gas content,large porosity,high brittle minerals content,high formation pressure,and the presence of lamellation/bedding and natural microfractures.Moreover,the"sweet area"is generally characterized by very thick organic-rich shale,moderate thermal evolution,good preservation conditions,and shallow burial depth,which are exemplified by the shale oil and gas in the Wufeng-Longmaxi Formation,Longtan Formation,and Daanzhai Member of the Ziliujing Formation.Third,the marine,transitional,and continental shale oil and gas resources in the Sichuan Basin account for 50%,25%,and 30%of the respective types of shale oil and gas geological resources in China,with great potential to become the cradle of the shale oil and gas industrial revolution in China.Following the"Conventional Daqing-Oil"(i.e.,the Daqing oilfield in the Songliao Basin)and the"Western Daqing-Oil&Gas"(i.e.,the Changqing oilfield in the Ordos Basin),the Southwest oil and gas field in the Sichuan Basin is expected to be built into a"Sichuan-Chongqing Daqing-Gas"in China.
