Predictions of fluid distribution,stress field,and natural fracture are essential for exploiting unconventional shale gas reservoirs.Given the high likelihood of tilted fractures in subsurface formations,this study fo...Predictions of fluid distribution,stress field,and natural fracture are essential for exploiting unconventional shale gas reservoirs.Given the high likelihood of tilted fractures in subsurface formations,this study focuses on simultaneous seismic inversion to estimate fluid bulk modulus,effective stress parameter,and fracture density in the tilted transversely isotropic(TTI)medium.In this article,a novel PP-wave reflection coefficient approximation equation is first derived based on the constructed TTI stiffness matrix incorporating fracture density,effective stress parameter,and fluid bulk modulus.The high accuracy of the proposed equation has been demonstrated using an anisotropic two-layer model.Furthermore,a stepwise seismic inversion strategy with the L_(P) quasi-norm sparsity constraint is implemented to obtain the anisotropic and isotropic parameters.Three synthetic model tests with varying signal-to-noise ratios(SNRs)confirm the method's feasibility and noise robustness.Ultimately,the proposed method is applied to a 3D fractured shale gas reservoir in the Sichuan Basin,China.The results have effectively characterized shale gas distribution,stress fields,and tilted natural fractures,with validation from geological structures,well logs,and microseismic events.These findings can provide valuable guidance for hydraulic fracturing development,enabling more reliable predictions of reservoir heterogeneity and completion quality.展开更多
The East China Sea Shelf Basin,especially the Xihu depression in its northeastern region,has long been regarded as an important target area for oil and gas exploration in China.Since the development of the late Cretac...The East China Sea Shelf Basin,especially the Xihu depression in its northeastern region,has long been regarded as an important target area for oil and gas exploration in China.Since the development of the late Cretaceous,this region has experienced complex and multistage tectonic movements,such as extensional faulting and compressional inversion,forming its current unique geological structure pattern.As one of the largest Mesozoic–Cenozoic sedimentary basins offshore China,the East China Sea Shelf Basin not only contains abundant oil and gas resources but also occupies a key strategic position.In addition,it is gradually becoming an important base and strategic core area for China's oil and gas resource development.Although remarkable progress has been achieved in oil and gas exploration,seismic exploration in the Xihu depression still faces many challenges.Especially in deep target layers,weak seismic reflection energy,low signal-to-noise ratio,and poor wave group continuity seriously affect the efficiency and accuracy of oil and gas exploration.In addition,given the considerable influence of folds and faults in the East China Sea Xihu Basin,transverse anisotropy is widespread,which causes difficulty for conventional imaging technologies based on isotropic assumptions to achieve accurate imaging.Therefore,to address these challenges and meet the need for accurate imaging of complex structures in the Xihu depression of the East China Sea Basin,it is essential to advance research on anisotropic imaging technologies.This study responds to that need by integrating the reverse time migration method under a tilted transversely isotropic(TTI)medium model and applying it to the imaging of the Xihu depression.The imaging profiles based on the TTI medium can substantially improve the imaging accuracy and signal-to-noise ratio,effectively improve the imaging quality of the fault systems and mid-deep strata in the area,and provide new technical support and progress momentum for oil and gas exploration in the Xihu depression of the East China Sea.展开更多
基金financially supported by the Natural Science Foundation of Sichuan Province(Grant Nos.2023NSFSC0767 and2024NSFSC0809)the China Postdoctoral Science Foundation(Grant No.2024MF750281)the Postdoctoral Fellowship Program of CPSF(Grant No.GZC20230326)。
文摘Predictions of fluid distribution,stress field,and natural fracture are essential for exploiting unconventional shale gas reservoirs.Given the high likelihood of tilted fractures in subsurface formations,this study focuses on simultaneous seismic inversion to estimate fluid bulk modulus,effective stress parameter,and fracture density in the tilted transversely isotropic(TTI)medium.In this article,a novel PP-wave reflection coefficient approximation equation is first derived based on the constructed TTI stiffness matrix incorporating fracture density,effective stress parameter,and fluid bulk modulus.The high accuracy of the proposed equation has been demonstrated using an anisotropic two-layer model.Furthermore,a stepwise seismic inversion strategy with the L_(P) quasi-norm sparsity constraint is implemented to obtain the anisotropic and isotropic parameters.Three synthetic model tests with varying signal-to-noise ratios(SNRs)confirm the method's feasibility and noise robustness.Ultimately,the proposed method is applied to a 3D fractured shale gas reservoir in the Sichuan Basin,China.The results have effectively characterized shale gas distribution,stress fields,and tilted natural fractures,with validation from geological structures,well logs,and microseismic events.These findings can provide valuable guidance for hydraulic fracturing development,enabling more reliable predictions of reservoir heterogeneity and completion quality.
基金the Major Science and Technology Project of CNOOC Limited Project‘Exploration Direction and Key Technology Study of Large and Medium-Sized Gas Fields in Haixi Sag,East China Sea’(No.KJZX-2023-0101)the China National Offshore Oil Corporation(CNOOC)during the‘14th Five-Year Plan’(No.KJGG2022-0104)+1 种基金the National Natural Science Foundation of China(Nos.42074138,42206195)the Science and Technology Innovation Project of the LaoShan Laboratory(No.2021WHZZB0703)。
文摘The East China Sea Shelf Basin,especially the Xihu depression in its northeastern region,has long been regarded as an important target area for oil and gas exploration in China.Since the development of the late Cretaceous,this region has experienced complex and multistage tectonic movements,such as extensional faulting and compressional inversion,forming its current unique geological structure pattern.As one of the largest Mesozoic–Cenozoic sedimentary basins offshore China,the East China Sea Shelf Basin not only contains abundant oil and gas resources but also occupies a key strategic position.In addition,it is gradually becoming an important base and strategic core area for China's oil and gas resource development.Although remarkable progress has been achieved in oil and gas exploration,seismic exploration in the Xihu depression still faces many challenges.Especially in deep target layers,weak seismic reflection energy,low signal-to-noise ratio,and poor wave group continuity seriously affect the efficiency and accuracy of oil and gas exploration.In addition,given the considerable influence of folds and faults in the East China Sea Xihu Basin,transverse anisotropy is widespread,which causes difficulty for conventional imaging technologies based on isotropic assumptions to achieve accurate imaging.Therefore,to address these challenges and meet the need for accurate imaging of complex structures in the Xihu depression of the East China Sea Basin,it is essential to advance research on anisotropic imaging technologies.This study responds to that need by integrating the reverse time migration method under a tilted transversely isotropic(TTI)medium model and applying it to the imaging of the Xihu depression.The imaging profiles based on the TTI medium can substantially improve the imaging accuracy and signal-to-noise ratio,effectively improve the imaging quality of the fault systems and mid-deep strata in the area,and provide new technical support and progress momentum for oil and gas exploration in the Xihu depression of the East China Sea.
