In situ stress inversion and fracture characteristics around local fault in deep heterogeneous strata

Abstract

The southeast Sichuan in China is a key area for deep shale gas exploration. However, shale gas exploration in deep heterogeneous strata is greatly affected by in situ stress. Faults caused by tectonic movement strongly change the distribution of in situ stress. Inversion and prediction of in situ stress have become an important research hotspot in the field of resource exploitation. Based on the geological structure evolution and experimental data, the boundary stress iterative inversion method is used to inverse the in situ stress field of deep heterogeneous strata containing shale gas reservoirs, and the fracture characteristics around local fault are analyzed by fracture mechanics theory. The research shows that the stress field has the characteristics of non-uniform distribution under the influence of fault, and there is obvious stress concentration and deflection of principal stress direction around the fault. And magnitude and direction of stress are affected by the internal friction angle of the fault zone and the formation depth in different tectonic periods. Through the analysis and calculation of the plastic strain and stress intensity factors, it can be inferred that the cracks will propagate at the terminal portion of the fault. The research is important to guide engineering for the adjustment of resource exploitation scheme.