Three-dimensional inversion of geostress in Xinchang gas field, Western Sichuan Sag

According to the formation lithology, geological structure and structure evolution of Xinchang area and its vicinity in the Western Sichuan Sag, the geologic model of research area was established, combining with the analysis results of drilling core fracture development characteristics, well reports, geostress and crack analysis. Geostress data were obtained from the analysis of borehole breakout data, drilling-induced fracture, hydraulic fracturing curve and rock Kaiser effect test. Those data were used as modern geostress reference values during model boundary conditions computing and geostress field inversion. The research results show that generally the maximum horizontal principal stress is nearly NEE-SWW. But it is apparently deflected near to the faults. And main subject orientation and regional tectonic stress are in the same direction. On the whole, main stress value increases with depth, and it has a good linear relationship with depth. Since fault structures developed in every stratum in the second member of the Xujiahe Formation, stress field shows obvious discontinuity, which makes geostress change in values and direction. There are obvious maximum principal stress and shear stress concentration phenomenon in fault ends and turning parts. However, stress dissipating appears in both sides of fault.