Response Characteristics Analysis Of Seismic Physical Simulation Of Fractured Shale Reservoir And Fracture Prediction

The Wufeng-Longmaxi Formation shale in southern Sichuan Basin is rich in shale gas resources,which is an important area for shale gas exploration and production.The development of fractures is of great significance to the reservoir and development of shale gas.A complex fracture system is developed in the Wufeng-Longmaxi Formation shale in Luzhou area,southern Sichuan,but its seismic response is not clear,therefore,it is great meaningful to study the seismic response characteristics of fractures and the applicability of fracture prediction methods.Based on the actual demand of shale gas exploration and production in Luzhou area of southern Sichuan,this study uses physical simulation method to explore the seismic response characteristics of fractures with different parameters in thin reservoirs,and focuses on the response characteristics of fractures with different parameters in post-stack properties and pre-stack elastic parameters.In terms of physical simulation,firstly,combined with the actual geological characteristics of the Luzhou working area in southern Sichuan,a 3D seismic physical model based on the Fuji synclinal spacer structure was designed and constructed.Secondly,the fractured rock samples with different fracture densities,opening degrees and dip angles were produced by thin section simulation method and placed in the target layer.Finally,high density 3D seismic physical model data are obtained through simulated seismic acquisition.In the study of fracture seismic response,three seismic attribute analysis methods which are coherent volume,curvature volume and ant-tracking volume,are firstly applied to physical simulation of post-stack seismic data.It is shown that three methods can achieve clear characterization of large-scale faults(strike length is more than 1000 m,fault distance is more than 60 m),however it is difficult to describe the smaller-scale fractures(horizontal scale is 400 m and vertical scale is 20 m)through comparative analysis.Furthermore,13 elastic parameters are obtained by prestack seismic inversion,and corresponding sensitive elastic parameters are optimized for fracture systems with different parameters.This research provides an important theoretical basis for the fracture prediction of the Wufeng-Longmaxi formation shale reservoirs of the southern Sichuan area.