Marine shale gas in the southern Sichuan Basin is the most successful area of shale gas exploration and development in China.In order to open up new shale gas fields and search for new shale gas reserves and productio...Marine shale gas in the southern Sichuan Basin is the most successful area of shale gas exploration and development in China.In order to open up new shale gas fields and search for new shale gas reserves and production replacement blocks,it is necessary to continuously establish and complete the standards on shale gas reservoir evaluation and area selection under different structural settings.The early exploration practice shows that shale in the mountainous complex structural area along the southwestern margin of the Sichuan Basin varies greatly in the gas bearing property,so systematical analysis and study on the shale gas enrichment mechanisms in this area is of great significance to searching for new shale gas exploration areas.Based on drilling data of 5 wells in the mountainous complex structural area along the southwestern margin of the Sichuan Basin,the main factors controlling the shale gas bearing property and the shale gas enrichment model were discussed based on the systematical experiments and analysis of the outcrops,cores and cuttings of Longmaxi Formation shale from the aspects of organic geochemistry,physical property,gas content,hydrocarbon generation history and pore evolution history,so as to lay a solid geological basis for the birth of a new shale gas area.And the following research results were obtained.First,the shale of the first submember of first Member of Longmaxi Formation(S1l11)in the mountainous complex structural area along the southwestern margin of the Sichuan Basin has an average TOC of 3.02%–4.97%and Ro of 2.38%–3.37%,and the average total gas content in local enrichment zones is up to 4.62 m^(3)/t,so it is classified as quality shale.Second,the detailed studies on hydrocarbon generation history indicate that the shale has the characteristics of“low thermal evolution rate and low maturity”.It is characterized by late hydrocarbon generation,low thermal evolution rate,low current maturity and short late diffusion time,which are favorable for shale gas enrichment.Third,the pore evolution history reveals that shale pore evolution can be divided into six stages,i.e.,sharp pore reduction,pore reduction,organic pore formation,pore preservation,organic pore dissipation and karstification,and organic pore and TOC are the most direct control factors of shale gas content.Fourth,favorable shelf facies belt is conducive to the formation of large-scale reservoir space and effective pores,and diversities of preservation conditions under different structural styles and at different structural positions control different pore evolution stages.The shale gas in the mountainous complex structural area is characterized by horizontal zoning and differential enrichment.“Low thermal evolution rate and low maturity”and“slow structural uplifting”are beneficial to the long-term enrichment and preservation of shale gas.In conclusion,the mountainous complex structural area along the southwestern margin of the Sichuan Basin has a shale gas enrichment model of“sedimentation controlling source rocks,diagenesis controlling reservoirs and structure controlling preservation”.This research result provides idea and reference for searching for new shale gas areas and fields.展开更多
Multiple sets of marine shale sequences occur in western Hubei Province and its adjacent areas within the Middle-Upper Yangtze region,offering substantial resource potential.However,their shale gas preservation condit...Multiple sets of marine shale sequences occur in western Hubei Province and its adjacent areas within the Middle-Upper Yangtze region,offering substantial resource potential.However,their shale gas preservation conditions differ significantly due to the heterogeneous porosity and fracture system resulting from multistage tectonic reworking.This necessitates developing region-specific evaluation systems and exploitation techniques.Drawing on previous application cases and guided by the research paradigm of geology-engineering integration,this study presents key technologies potentially applicable to shales in western Hubei Province,spanning from reservoir and sweet spot evaluation to fractu ring scheme design and fracturing perfo rmance monitoring.Several insights are gained accordingly.In terms of pore evaluation,the pore heterogeneity caused by compaction and rebound can be quantified using ideal shape coefficients and fractal dimensions,both of which are influenced by structural deformations,thereby guiding reservoir classification.For seismic data interpretation,pre-stack elastic inversion and azimuthal anisotropy inversion can be employed as core techniques,overcoming the limitation of individual post-stack attributes in typically detecting only major faults.Furthermore,the inversion boundaries are constrained using log-seismic joint quality control and geomechanical simulation,contributing to enhanced reliability of sweet spot evaluation and efficient exploration in areas with complex structures.For fracturing scheme design,scientifically formulated well shut-in strategies,tailored to regional geological characteristics,are essential to activate the fracture-matrix imbibition effect.Parameters with vastly different scales used in the design,such as meter-scale fracture halflength and millidarcy-scale fracture conductivity,can be co-optimized using artificial intelligence(AI)algorithms such as the genetic algorithm(GA)and the simultaneous perturbation stochastic approximation(SPSA)algorithm.Dynamic monitoring of fracturing performance can be achieved using trace chemical tracer technology,thereby reducing target ambiguity caused by structural complexity.Research on shale gas in the structurally complex areas of western Hubei faces multiple challenges,spanning from basic geological understanding to development engineering.These challenges create an urgent need for deep interdisciplinary collaboration.Therefore,this study highlights research into geology-engineering integration,aiming to enhance the efficiency of shale gas exploration and development in western Hubei.展开更多
基金supported by the National Major Science and Technology Project“Test and application of reconnaissance and evaluation technologies for shale gas”(No.:2016ZX05034004)the Project of China Geological Survey“Basic geologic survey of Lower Paleozoic marine shale gas in Sichuan Basin”(No.:DD20160176)+1 种基金“Survey on strategic zone of shale gas in Longmaxi Formation,Sichuan Basin”(No.:DD20160193)“Survey on shale gas enrichment conditions in Sichuan Basin”(No.:12120114071401).
文摘Marine shale gas in the southern Sichuan Basin is the most successful area of shale gas exploration and development in China.In order to open up new shale gas fields and search for new shale gas reserves and production replacement blocks,it is necessary to continuously establish and complete the standards on shale gas reservoir evaluation and area selection under different structural settings.The early exploration practice shows that shale in the mountainous complex structural area along the southwestern margin of the Sichuan Basin varies greatly in the gas bearing property,so systematical analysis and study on the shale gas enrichment mechanisms in this area is of great significance to searching for new shale gas exploration areas.Based on drilling data of 5 wells in the mountainous complex structural area along the southwestern margin of the Sichuan Basin,the main factors controlling the shale gas bearing property and the shale gas enrichment model were discussed based on the systematical experiments and analysis of the outcrops,cores and cuttings of Longmaxi Formation shale from the aspects of organic geochemistry,physical property,gas content,hydrocarbon generation history and pore evolution history,so as to lay a solid geological basis for the birth of a new shale gas area.And the following research results were obtained.First,the shale of the first submember of first Member of Longmaxi Formation(S1l11)in the mountainous complex structural area along the southwestern margin of the Sichuan Basin has an average TOC of 3.02%–4.97%and Ro of 2.38%–3.37%,and the average total gas content in local enrichment zones is up to 4.62 m^(3)/t,so it is classified as quality shale.Second,the detailed studies on hydrocarbon generation history indicate that the shale has the characteristics of“low thermal evolution rate and low maturity”.It is characterized by late hydrocarbon generation,low thermal evolution rate,low current maturity and short late diffusion time,which are favorable for shale gas enrichment.Third,the pore evolution history reveals that shale pore evolution can be divided into six stages,i.e.,sharp pore reduction,pore reduction,organic pore formation,pore preservation,organic pore dissipation and karstification,and organic pore and TOC are the most direct control factors of shale gas content.Fourth,favorable shelf facies belt is conducive to the formation of large-scale reservoir space and effective pores,and diversities of preservation conditions under different structural styles and at different structural positions control different pore evolution stages.The shale gas in the mountainous complex structural area is characterized by horizontal zoning and differential enrichment.“Low thermal evolution rate and low maturity”and“slow structural uplifting”are beneficial to the long-term enrichment and preservation of shale gas.In conclusion,the mountainous complex structural area along the southwestern margin of the Sichuan Basin has a shale gas enrichment model of“sedimentation controlling source rocks,diagenesis controlling reservoirs and structure controlling preservation”.This research result provides idea and reference for searching for new shale gas areas and fields.
基金supported by the Excellence Research Group Program of the Hubei Provincial Natural Science Foundation(originally termed Basic Science Center Program)(JCKXXM202500016)the Key Program of the National Natural Science Foundation of China(42230812)the National Natural Science Foundation of China(42073068)。
文摘Multiple sets of marine shale sequences occur in western Hubei Province and its adjacent areas within the Middle-Upper Yangtze region,offering substantial resource potential.However,their shale gas preservation conditions differ significantly due to the heterogeneous porosity and fracture system resulting from multistage tectonic reworking.This necessitates developing region-specific evaluation systems and exploitation techniques.Drawing on previous application cases and guided by the research paradigm of geology-engineering integration,this study presents key technologies potentially applicable to shales in western Hubei Province,spanning from reservoir and sweet spot evaluation to fractu ring scheme design and fracturing perfo rmance monitoring.Several insights are gained accordingly.In terms of pore evaluation,the pore heterogeneity caused by compaction and rebound can be quantified using ideal shape coefficients and fractal dimensions,both of which are influenced by structural deformations,thereby guiding reservoir classification.For seismic data interpretation,pre-stack elastic inversion and azimuthal anisotropy inversion can be employed as core techniques,overcoming the limitation of individual post-stack attributes in typically detecting only major faults.Furthermore,the inversion boundaries are constrained using log-seismic joint quality control and geomechanical simulation,contributing to enhanced reliability of sweet spot evaluation and efficient exploration in areas with complex structures.For fracturing scheme design,scientifically formulated well shut-in strategies,tailored to regional geological characteristics,are essential to activate the fracture-matrix imbibition effect.Parameters with vastly different scales used in the design,such as meter-scale fracture halflength and millidarcy-scale fracture conductivity,can be co-optimized using artificial intelligence(AI)algorithms such as the genetic algorithm(GA)and the simultaneous perturbation stochastic approximation(SPSA)algorithm.Dynamic monitoring of fracturing performance can be achieved using trace chemical tracer technology,thereby reducing target ambiguity caused by structural complexity.Research on shale gas in the structurally complex areas of western Hubei faces multiple challenges,spanning from basic geological understanding to development engineering.These challenges create an urgent need for deep interdisciplinary collaboration.Therefore,this study highlights research into geology-engineering integration,aiming to enhance the efficiency of shale gas exploration and development in western Hubei.
