川西凹陷新场气田三维地应力场反演分析

根据川西凹陷新场地区及邻区已有的地层岩性、地质构造及其演化等资料,结合深部岩体钻井岩心裂缝发育特征编录、完井报告、录井测井地应力和裂缝分析成果,建立了研究区的地质模型。利用已有的井孔崩落、钻井诱导缝分析、水压致裂曲线分析、岩石Kaiser效应测试等技术所获得的地应力资料,作为计算模型的应力边界条件和地应力场反演的井段现今地应力参考值,采用三维数值模拟技术对川西凹陷新场气田进行了三维地应力场反演分析。研究结果表明,总体上最大水平主应力以近NEESWW向为主,但在断层附近主应力方向发生明显偏转,主体方位与区域构造应力作用主方向一致。各主地应力值总体上随深度的增加而变大,与深度之间有较好的线性相关关系,由于新场须二段各目的层均发育较多断裂构造,因此其应力场表现出明显的不连续性,使地应力值和方向发生局部变化,在断层端部和转折部位表现出较明显的最大主应力和剪应力集中现象,而在断层两盘部位则出现应力消散特点。

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.