The electrophysical property of saturated rocks is very important for reservoir identification and evaluation. In this paper, the lattice Boltzmann method （LBM） was used to study the electrophysical property of rock...The electrophysical property of saturated rocks is very important for reservoir identification and evaluation. In this paper, the lattice Boltzmann method （LBM） was used to study the electrophysical property of rock saturated with fluid because of its advantages over conventional numerical approaches in handling complex pore geometry and boundary conditions. The digital core model was constructed through the accumulation of matrix grains based on their radius distribution obtained by the measurements of core samples. The flow of electrical current through the core model saturated with oil and water was simulated on the mesoscopic scale to reveal the non-Archie relationship between resistivity index and water saturation （I-Sw）. The results from LBM simulation and laboratory measurements demonstrated that the I-Sw relation in the range of low water saturation was generally not a straight line in the log-log coordinates as described by the Archie equation. We thus developed a new equation based on numerical simulation and physical experiments. This new equation was used to fit the data from laboratory core measurements and previously published data. Determination of fluid saturation and reservoir evaluation could be significantly improved by using the new equation.展开更多
Brittleness is pivotal in predicting shale reservoir quality and designing hydraulic fracturing strategies.However,intricate diagenetic environment of shale,characterized by distinct bedding structures,challenges the ...Brittleness is pivotal in predicting shale reservoir quality and designing hydraulic fracturing strategies.However,intricate diagenetic environment of shale,characterized by distinct bedding structures,challenges the isotropic-based brittleness assessment methods.This study introduces a new quantitative approach to assess shale brittleness anisotropy,integrating anisotro pic elastic responses and tensile fracturing mechanisms.The proposed model effectively reduces uncertainty in the causal relationship between Young's modulus and brittle failure.Comprehensive experimental validation encompassed 18samples from six groups of Chang 7 terrestrial shale in Ordos Basin.The optimal anisotropic tensile strength criterion(N-Z criterion,error<5%)was identified,enhancing the theoretical accuracy of the proposed model.Comparative experimental results demonstrate that the model adeptly predicts brittleness strength and directional variation characteristics across variations in mineral type,content and microstructure,underscoring its effectiveness.Additionally,theoretical predictions on shale samples with different organic matter reveal that brittleness strength and its anisotropy across varying OM are not monotonously decreasing.The research highlights that brittleness characteristics are influenced by both mineral type/content and microstructural distribution.Notably,the prevalence of isotropic brittle minerals is the primary determinant of brittleness strength,positively correlated.Conversely,ductile mineral conte nt(striped skeletal support-type OM and clay)negatively corre lates with brittlene ss strength,acting as se condary controlling factors.The impact of pore-filled OM on brittleness appears negligible.Rock physical modeling base d on equivalent media theory for shale with pore-filled and/or striped OM further elucidates the mechanisms driving these variations.These findings attach great importance in assessment of terrestrial shale geological and engineering"sweet-spots".展开更多
The shale oil reservoir within the Yanchang Formations of Ordos Basin harbors substantial oil and gas resources and has recently emerged as the primary focus of unconventional oil and gas exploration and development.D...The shale oil reservoir within the Yanchang Formations of Ordos Basin harbors substantial oil and gas resources and has recently emerged as the primary focus of unconventional oil and gas exploration and development.Due to its complex pore and throat structure,pronounced heterogeneity,and tight reservoir characteristics,the techniques for conventional oil and gas exploration and production face challenges in comprehensive implementation,also indicating that as a vital parameter for evaluating the physical properties of a reservoir,permeability cannot be effectively estimated.This study selects 21 tight sandstone samples from the Q area within the shale oil formations of Ordos Basin.We systematically conduct the experiments to measure porosity,permeability,ultrasonic wave velocities,and resistivity at varying confining pressures.Results reveal that these measurements exhibit nonlinear changes in response to effective pressure.By using these experimental data and effective medium model,empirical relationships between P-and S-wave velocities,permeability and resistivity and effective pressure are established at logging and seismic scales.Furthermore,relationships between P-wave impedance and permeability,and resistivity and permeability are determined.A comparison between the predicted permeability and logging data demonstrates that the impedance–permeability relationship yields better results in contrast to those of resistivity–permeability relationship.These relationships are further applied to the seismic interpretation of shale oil reservoir in the target layer,enabling the permeability profile predictions based on inverse P-wave impedance.The predicted results are evaluated with actual production data,revealing a better agreement between predicted results and logging data and productivity.展开更多
基金sponsored by the project No.50404001 from the National Natural Science Foundation of Chinathe National Key Fundamental Research & Development Project(Grant No.2007CB209601)+1 种基金the China National PetroleumCorporation Fundamental Research Program (Grant No.06A30102)the China Postdoctoral Science Foundation(Project No.2004035350)
文摘The electrophysical property of saturated rocks is very important for reservoir identification and evaluation. In this paper, the lattice Boltzmann method （LBM） was used to study the electrophysical property of rock saturated with fluid because of its advantages over conventional numerical approaches in handling complex pore geometry and boundary conditions. The digital core model was constructed through the accumulation of matrix grains based on their radius distribution obtained by the measurements of core samples. The flow of electrical current through the core model saturated with oil and water was simulated on the mesoscopic scale to reveal the non-Archie relationship between resistivity index and water saturation （I-Sw）. The results from LBM simulation and laboratory measurements demonstrated that the I-Sw relation in the range of low water saturation was generally not a straight line in the log-log coordinates as described by the Archie equation. We thus developed a new equation based on numerical simulation and physical experiments. This new equation was used to fit the data from laboratory core measurements and previously published data. Determination of fluid saturation and reservoir evaluation could be significantly improved by using the new equation.
基金supported by the National Natural Science Foundation of China(42274175)Sichuan Provincial Joint Fund Project for Science,Technology and Education(2025NSFSC2035)Innovative Experimental Project at Institutions of Higher Education in Sichuan Province(Advanced Quantitative Rock Physics Investigations on the"Acoustic,Electrical,and Mechanical"Characte ristics of Unco nventional Reservoirs Subjected to Extre meHigh Temperature and High Pressure Environments)。
文摘Brittleness is pivotal in predicting shale reservoir quality and designing hydraulic fracturing strategies.However,intricate diagenetic environment of shale,characterized by distinct bedding structures,challenges the isotropic-based brittleness assessment methods.This study introduces a new quantitative approach to assess shale brittleness anisotropy,integrating anisotro pic elastic responses and tensile fracturing mechanisms.The proposed model effectively reduces uncertainty in the causal relationship between Young's modulus and brittle failure.Comprehensive experimental validation encompassed 18samples from six groups of Chang 7 terrestrial shale in Ordos Basin.The optimal anisotropic tensile strength criterion(N-Z criterion,error<5%)was identified,enhancing the theoretical accuracy of the proposed model.Comparative experimental results demonstrate that the model adeptly predicts brittleness strength and directional variation characteristics across variations in mineral type,content and microstructure,underscoring its effectiveness.Additionally,theoretical predictions on shale samples with different organic matter reveal that brittleness strength and its anisotropy across varying OM are not monotonously decreasing.The research highlights that brittleness characteristics are influenced by both mineral type/content and microstructural distribution.Notably,the prevalence of isotropic brittle minerals is the primary determinant of brittleness strength,positively correlated.Conversely,ductile mineral conte nt(striped skeletal support-type OM and clay)negatively corre lates with brittlene ss strength,acting as se condary controlling factors.The impact of pore-filled OM on brittleness appears negligible.Rock physical modeling base d on equivalent media theory for shale with pore-filled and/or striped OM further elucidates the mechanisms driving these variations.These findings attach great importance in assessment of terrestrial shale geological and engineering"sweet-spots".
基金supports from the National Natural Science Foundation of China(42104110,41974123,42174161,and 12334019)the Natural Science Foundation of Jiangsu Province(BK20210379,BK20200021)+1 种基金the Postdoctoral Science Foundation of China(2022M720989)the Fundamental Research Funds for the Central Universities(B210201032).
文摘The shale oil reservoir within the Yanchang Formations of Ordos Basin harbors substantial oil and gas resources and has recently emerged as the primary focus of unconventional oil and gas exploration and development.Due to its complex pore and throat structure,pronounced heterogeneity,and tight reservoir characteristics,the techniques for conventional oil and gas exploration and production face challenges in comprehensive implementation,also indicating that as a vital parameter for evaluating the physical properties of a reservoir,permeability cannot be effectively estimated.This study selects 21 tight sandstone samples from the Q area within the shale oil formations of Ordos Basin.We systematically conduct the experiments to measure porosity,permeability,ultrasonic wave velocities,and resistivity at varying confining pressures.Results reveal that these measurements exhibit nonlinear changes in response to effective pressure.By using these experimental data and effective medium model,empirical relationships between P-and S-wave velocities,permeability and resistivity and effective pressure are established at logging and seismic scales.Furthermore,relationships between P-wave impedance and permeability,and resistivity and permeability are determined.A comparison between the predicted permeability and logging data demonstrates that the impedance–permeability relationship yields better results in contrast to those of resistivity–permeability relationship.These relationships are further applied to the seismic interpretation of shale oil reservoir in the target layer,enabling the permeability profile predictions based on inverse P-wave impedance.The predicted results are evaluated with actual production data,revealing a better agreement between predicted results and logging data and productivity.
