Joint application of seismic multi-attribute in multi-scale fracture prediction of LZ shale gas block, Sichuan Basin, China

Abstract

The fractures that develop in the Sichuan Basin exhibit multiple characteristics, including various stages, scales, types, and strike directions. Due to the varying impacts of fractures on shale gas storage, migration, development, fracturing, and construction, it is crucial to provide a detailed characterization of the multi-scale fractures. A combination of three post-stack seismic attributes was initially used to predict fractures: the variance, the maximum curvature, and the ant tracking based on generalized S-transform spectrum analysis. Subsequently, the detected fractures were divided into distinct scales by establishing appropriate sub-scale thresholds for the ant tracking value. The study reached two conclusions. Firstly, ant tracking based on generalized S-transform spectrum analysis can identify smaller-scale fractures more effectively than the traditional ant tracking methods. Secondly, combining these attributes establishes a fracture prediction method that progressively enhances accuracy, transitioning from large to small scales. For the combined seismic attributes, the study conducted sub-scale fracture predictions for the Longmaxi–Wufeng Formation in the LZ shale gas block, obtaining three scales of fracture prediction results that provide a robust data foundation for subsequent stages of fracture modeling and shale gas development.