Based on the current research status of shale oil exploration and development at home and abroad,through field observations,dissection of typical shale oil regions,analysis and testing of organic-rich shale samples,et...Based on the current research status of shale oil exploration and development at home and abroad,through field observations,dissection of typical shale oil regions,analysis and testing of organic-rich shale samples,etc.,we compare the differences in geological and engineering characteristics of shale oil reservoirs in marine and continental basins in China and the United States,put forward several issues worthy of attention in the exploration and development of lacustrine shale oil in typical basins of China,including the concept of tight oil and shale oil,vertical permeability and horizontal permeability,differences between continental and marine shale oil reservoirs,medium-low maturity and medium-high maturity,source-reservoir and source-caprock,geology and engineering,selection criteria of favorable areas and“sweet spots”,basic scientific research and application research.By comparing and analyzing organic-rich shales in the Triassic Yanchang Formation of the Ordos Basin,the Permian Lucaogou Formation in the Jimsar Sag of the Junggar Basin,the Permian Fengcheng Formation in the Mahu Sag,the Cretaceous Qingshankou&Nenjiang Formation in the Songliao Basin and the Paleogene Kongdian&Shahejie Formation in the Bohai Bay Basin,we believe that three key scientific issues must be studied in-depth from shale oil exploration to development in the future:(1)the physical,chemical and biological processes during the deposition of terrestrial fine-grained sediments and the formation mechanism of terrestrial organic-rich shale;(2)the dynamic evolution of diagenesis-hydrocarbon generation-reservoir formation,and the mechanisms of hydrocarbon formation and accumulation;(3)the fracturing mechanisms of terrestrial shale layers in different diagenetic stages and the multi-phase and multi-scale flow mechanism of shale oil in shale layers of different maturities.In addition,we should clarify the main controlling factors of shale oil reservoir characterization,oil-bearing properties,compressibility and fluidity of shale oil with展开更多
Based on the production curves,changes in hydrocarbon composition and quantities over time,and production systems from key trial production wells in lacustrine shale oil areas in China,fine fraction cutting experiment...Based on the production curves,changes in hydrocarbon composition and quantities over time,and production systems from key trial production wells in lacustrine shale oil areas in China,fine fraction cutting experiments and molecular dynamics numerical simulations were conducted to investigate the effects of changes in shale oil composition on macroscopic fluidity.The concept of“component flow”for shale oil was proposed,and the formation mechanism and conditions of component flow were discussed.The research reveals findings in four aspects.First,a miscible state of light,medium and heavy hydrocarbons form within micropores/nanopores of underground shale according to similarity and intermiscibility principles,which make components with poor fluidity suspended as molecular aggregates in light and medium hydrocarbon solvents,such as heavy hydrocarbons,thereby decreasing shale oil viscosity and enhancing fluidity and outflows.Second,small-molecule aromatic hydrocarbons act as carriers for component flow,and the higher the content of gaseous and light hydrocarbons,the more conducive it is to inhibit the formation of larger aggregates of heavy components such as resin and asphalt,thus increasing their plastic deformation ability and bringing about better component flow efficiency.Third,higher formation temperatures reduce the viscosity of heavy hydrocarbon components,such as wax,thereby improving their fluidity.Fourth,preservation conditions,formation energy,and production system play important roles in controlling the content of light hydrocarbon components,outflow rate,and forming stable“component flow”,which are crucial factors for the optimal compatibility and maximum flow rate of multi-component hydrocarbons in shale oil.The component flow of underground shale oil is significant for improving single-well production and the cumulative ultimate recovery of shale oil.展开更多
Successful breakthroughs have been made in shale oil exploration in several lacustrine basins in China,indicating a promising future for shale oil exploration and production.Current exploration results have revealed t...Successful breakthroughs have been made in shale oil exploration in several lacustrine basins in China,indicating a promising future for shale oil exploration and production.Current exploration results have revealed the following major conditions of lacustrine shale oil accumulation:(1)stable and widely distributed shale with a high organic abundance and appropriate thermal maturity acts as a fundamental basis for shale oil retention.This shale exhibits several critical parameters,such as total organic carbon content greater than 2%,with optimal values ranging from 3% to 4%,kerogen Ⅰ and Ⅱ_(1) as the dominant organic matter types,and vitrinite reflectance(R_(o))values greater than 0.9%(0.8% for brackish water environments).(2)Various types of reservoirs exhibiting brittleness and a certain volume of micro-nanoscale pores are critical conditions for shale oil accumulation,and these reservoirs have porosities greater than 3% to 6%.Moreover,when diagenesis is incipient,pure shales are not favorable for medium-to-high maturity shale oil enrichment,whereas tight sandstone and hybrid rocks with clay content less than 20% are favorable;however,for medium-to-late-stage diagenesis,pure shales with a clay content of 40% are favorable.(3)The retention of a large amount of high-quality hydrocarbons is the factor that best guarantees shale oil accumulation with good mobility.Free hydrocarbon content exceeding a threshold value of 2 mg/g is generally required,and the optimum value is 4 mg/g to 6 mg/g.Moreover,a gas-oil ratio exceeding a threshold value of 80 m^(3)/m^(3) is required,with the optimal value ranging from 150 m^(3)/m^(3) to 300 m^(3)/m^(3).(4)High-quality roof and floor sealing conditions are essential for the shale oil enrichment interval to maintain the overpressure and retain a sufficient amount of hydrocarbons with good quality.Lacustrine shale oil distributions exhibit the following characteristics:(1)major enrichment areas of shale oil are located in semi-deep to deep lacustrine depositional areas with ex展开更多
Based on the comparison of basic geological conditions and enrichment characteristics of shale oil plays, the heterogeneity of source and reservoir conditions and differential enrichment of medium-high maturity contin...Based on the comparison of basic geological conditions and enrichment characteristics of shale oil plays, the heterogeneity of source and reservoir conditions and differential enrichment of medium-high maturity continental shale oil plays in China have been confirmed.(1) Compared with the homogeneous geological settings and wide distribution of marine shale oil strata in North America, the continental medium and high maturity shale oil plays in China are significantly different in geological conditions generally;continental multi-cyclic tectonic evolution forms multiple types of lake basins in multi-stages, providing sites for large-scale development of continental shale oil, and giving rise to large scale high-quality source rocks, multiple types of reservoirs, and diverse source-reservoir combinations with significant heterogeneity.(2) The differences in sedimentary water environments lead to the heterogeneity in lithology, lithofacies, and organic material types of source rocks;the differences in material source supply and sedimentary facies belt result in reservoirs of different lithologies, including argillaceous and transition rocks, and tight siltstone, and complex source-reservoir combination types.(3) The heterogeneity of the source rock controls the differentiation of hydrocarbon generation and expulsion, the diverse reservoir types make reservoir performance different and the source-reservoir configurations complex, and these two factors ultimately make the shale oil enrichment patterns different. Among them, the hydrocarbon generation and expulsion capacity of high-quality source rocks affect the degree of shale oil enrichment. Freshwater hydrocarbon source rocks with TOC larger than 2.5% and saline hydrocarbon source rocks with TOC of 2% to 10% have a high content of retained hydrocarbons and are favorable.(4) High-abundance organic shale is the basis for the enrichment of shale oil inside the source. In addition to being retained in shale, liquid hydrocarbons migrate along laminae, diagenetic fractu展开更多
文摘Based on the current research status of shale oil exploration and development at home and abroad,through field observations,dissection of typical shale oil regions,analysis and testing of organic-rich shale samples,etc.,we compare the differences in geological and engineering characteristics of shale oil reservoirs in marine and continental basins in China and the United States,put forward several issues worthy of attention in the exploration and development of lacustrine shale oil in typical basins of China,including the concept of tight oil and shale oil,vertical permeability and horizontal permeability,differences between continental and marine shale oil reservoirs,medium-low maturity and medium-high maturity,source-reservoir and source-caprock,geology and engineering,selection criteria of favorable areas and“sweet spots”,basic scientific research and application research.By comparing and analyzing organic-rich shales in the Triassic Yanchang Formation of the Ordos Basin,the Permian Lucaogou Formation in the Jimsar Sag of the Junggar Basin,the Permian Fengcheng Formation in the Mahu Sag,the Cretaceous Qingshankou&Nenjiang Formation in the Songliao Basin and the Paleogene Kongdian&Shahejie Formation in the Bohai Bay Basin,we believe that three key scientific issues must be studied in-depth from shale oil exploration to development in the future:(1)the physical,chemical and biological processes during the deposition of terrestrial fine-grained sediments and the formation mechanism of terrestrial organic-rich shale;(2)the dynamic evolution of diagenesis-hydrocarbon generation-reservoir formation,and the mechanisms of hydrocarbon formation and accumulation;(3)the fracturing mechanisms of terrestrial shale layers in different diagenetic stages and the multi-phase and multi-scale flow mechanism of shale oil in shale layers of different maturities.In addition,we should clarify the main controlling factors of shale oil reservoir characterization,oil-bearing properties,compressibility and fluidity of shale oil with
基金Supported by the National Natural Science Foundation of China(U22B6004)Scientific Research and Technological Development Project of RIPED(2022yjcq03)Technology Research Project of PetroChina Changqing Oilfield Company(KJZX2023-01)。
文摘Based on the production curves,changes in hydrocarbon composition and quantities over time,and production systems from key trial production wells in lacustrine shale oil areas in China,fine fraction cutting experiments and molecular dynamics numerical simulations were conducted to investigate the effects of changes in shale oil composition on macroscopic fluidity.The concept of“component flow”for shale oil was proposed,and the formation mechanism and conditions of component flow were discussed.The research reveals findings in four aspects.First,a miscible state of light,medium and heavy hydrocarbons form within micropores/nanopores of underground shale according to similarity and intermiscibility principles,which make components with poor fluidity suspended as molecular aggregates in light and medium hydrocarbon solvents,such as heavy hydrocarbons,thereby decreasing shale oil viscosity and enhancing fluidity and outflows.Second,small-molecule aromatic hydrocarbons act as carriers for component flow,and the higher the content of gaseous and light hydrocarbons,the more conducive it is to inhibit the formation of larger aggregates of heavy components such as resin and asphalt,thus increasing their plastic deformation ability and bringing about better component flow efficiency.Third,higher formation temperatures reduce the viscosity of heavy hydrocarbon components,such as wax,thereby improving their fluidity.Fourth,preservation conditions,formation energy,and production system play important roles in controlling the content of light hydrocarbon components,outflow rate,and forming stable“component flow”,which are crucial factors for the optimal compatibility and maximum flow rate of multi-component hydrocarbons in shale oil.The component flow of underground shale oil is significant for improving single-well production and the cumulative ultimate recovery of shale oil.
基金Major Project of National Natural Science Foundation of China(42090020,42090025)Major Project of CNPC(2019E-2601)。
文摘Successful breakthroughs have been made in shale oil exploration in several lacustrine basins in China,indicating a promising future for shale oil exploration and production.Current exploration results have revealed the following major conditions of lacustrine shale oil accumulation:(1)stable and widely distributed shale with a high organic abundance and appropriate thermal maturity acts as a fundamental basis for shale oil retention.This shale exhibits several critical parameters,such as total organic carbon content greater than 2%,with optimal values ranging from 3% to 4%,kerogen Ⅰ and Ⅱ_(1) as the dominant organic matter types,and vitrinite reflectance(R_(o))values greater than 0.9%(0.8% for brackish water environments).(2)Various types of reservoirs exhibiting brittleness and a certain volume of micro-nanoscale pores are critical conditions for shale oil accumulation,and these reservoirs have porosities greater than 3% to 6%.Moreover,when diagenesis is incipient,pure shales are not favorable for medium-to-high maturity shale oil enrichment,whereas tight sandstone and hybrid rocks with clay content less than 20% are favorable;however,for medium-to-late-stage diagenesis,pure shales with a clay content of 40% are favorable.(3)The retention of a large amount of high-quality hydrocarbons is the factor that best guarantees shale oil accumulation with good mobility.Free hydrocarbon content exceeding a threshold value of 2 mg/g is generally required,and the optimum value is 4 mg/g to 6 mg/g.Moreover,a gas-oil ratio exceeding a threshold value of 80 m^(3)/m^(3) is required,with the optimal value ranging from 150 m^(3)/m^(3) to 300 m^(3)/m^(3).(4)High-quality roof and floor sealing conditions are essential for the shale oil enrichment interval to maintain the overpressure and retain a sufficient amount of hydrocarbons with good quality.Lacustrine shale oil distributions exhibit the following characteristics:(1)major enrichment areas of shale oil are located in semi-deep to deep lacustrine depositional areas with ex
基金Supported by the National Natural Science Foundation of China (42072186)China National Oil and Gas Major Project (2016ZX05046-001)PetroChina Scientific Research and Technology Project (2021-DJ2203)。
文摘Based on the comparison of basic geological conditions and enrichment characteristics of shale oil plays, the heterogeneity of source and reservoir conditions and differential enrichment of medium-high maturity continental shale oil plays in China have been confirmed.(1) Compared with the homogeneous geological settings and wide distribution of marine shale oil strata in North America, the continental medium and high maturity shale oil plays in China are significantly different in geological conditions generally;continental multi-cyclic tectonic evolution forms multiple types of lake basins in multi-stages, providing sites for large-scale development of continental shale oil, and giving rise to large scale high-quality source rocks, multiple types of reservoirs, and diverse source-reservoir combinations with significant heterogeneity.(2) The differences in sedimentary water environments lead to the heterogeneity in lithology, lithofacies, and organic material types of source rocks;the differences in material source supply and sedimentary facies belt result in reservoirs of different lithologies, including argillaceous and transition rocks, and tight siltstone, and complex source-reservoir combination types.(3) The heterogeneity of the source rock controls the differentiation of hydrocarbon generation and expulsion, the diverse reservoir types make reservoir performance different and the source-reservoir configurations complex, and these two factors ultimately make the shale oil enrichment patterns different. Among them, the hydrocarbon generation and expulsion capacity of high-quality source rocks affect the degree of shale oil enrichment. Freshwater hydrocarbon source rocks with TOC larger than 2.5% and saline hydrocarbon source rocks with TOC of 2% to 10% have a high content of retained hydrocarbons and are favorable.(4) High-abundance organic shale is the basis for the enrichment of shale oil inside the source. In addition to being retained in shale, liquid hydrocarbons migrate along laminae, diagenetic fractu
