Fracture Detection In Shale Reservoirs Using 3d Post-stack Seismic Attributes And Pre-stack Anisotropic Technology In The OVT Domain

China is abundant in shale gas resources.However,complex geology structures and unstable depositional environments result in the exploration risks.In the early stage of exploration,verifications of shale gas 'sweet spots' are critical for enhancing the success rate and reducing costs in the exploration and development.Fracture is one of a crucial governing factor of ‘sweet spots',determining crack connectivity and reservoir productivity.Therefore,it is of great significance to detect fractures in shales.In this paper,we firstly concluded and analyzed conceptions and applicable conditions of 3 dimensional post-stack fracture prediction technologies such as coherency,curvature,automatic Fault Extraction as well as multi-attribute feature fusion.Then,we introduced Offset Vector Tile(OVT)and its related conceptions,key processing technologies and advantage analysis.Based on the characteristics in the OVT domain,we conducted a study on pre-stack P-wave azimuthal anisotropy fracture prediction technologies,demonstrating that their elliptical fitting can be more accurate.In the end,we comprehensively analyzed fracture prediction results respectively based upon 3 dimensional post-stack seismic attributes and pre-stack P-wave anisotropy characteristics in OVT domain.Afterwards,we conducted interactive analysis and confirmation between the predicted results and micro-seismic indicated area.According to real data of the survey area in Sichuan,post-stack fracture prediction methods have better prediction for larger scale faults,while pre-stack fracture methods based on the OVT domain are more accurate and have capacities of recognizing smaller scale fractures.And the prediction results mentioned above are well validated by micro-seismic data.