昭通页岩储层非均质地应力场数值模拟

Numerical simulation on the heterogeneous earth stress field of shale reservoir in Zhaotong

储层地应力场是页岩气开发井网布置、井眼轨道设计、压裂设计的重要参考因素。其形成机理复杂,具有较强非均匀性,地应力的实测数据有限且具有局部性。为准确求取云南昭通黄金坝YS108区块页岩气储层的地应力场,通过研究分析储层地应力场的平面分布,利用多元线性回归方法求解页岩气储层地应力场,并在传统方法上增加三角分布载荷,模拟了储层非均质地应力,以提高地应力场的计算精度;同时建立页岩气储层平面的几何模型,利用Abaqus有限元软件和该区4口井的地应力实测资料,运用多元线性回归方法求解,得出了整个页岩气储层地应力场。结论认为:该方法计算精度较高,相对误差在8%以内,能较为合理地模拟出页岩储层的地应力场;根据得出的储层地应力场,水平井轨迹应沿最小主应力方向设计,压裂射孔位置应设计在最大主应力方向且两向地应力差较小的区域。

The earth stress field of reservoirs is the important reference factor of well pattern arrangement, wellbore trajectory design and fracturing design for shale gas development. Earth stress field is of stronger heterogeneity and its formation mechanisms are com- plicated, so the measured data is limited and localized. To calculate accurately the earth stress field of shale gas reservoir in Huang- jinba YS108 Block in Zhaotong, Yunnan, the plane distribution of earth stress field in the reservoir was analyzed, and the earth stress field in the shale gas reservoir was calculated by means of multivariate linear regression method. Besides, the traditional method was added with the triangle distribution loading to simulate the heterogeneous earth stress so as to increase the calculation accuracy of earth stress. Then, the geometric model for the plane of shale gas reservoir was established. Finally, by virtue of the multivariate linear regression method, the earth stress field of the whole shale gas reservoir was calculated using the Abaqus finite element software and the measured earth stress data of 4 wells in this area. It is indicated that this method has higher calculation accuracy with relative error lower than 8%, and it can simulate rationally the earth stress field of shale reservoirs. According to the calculated earth stress field, It is determined that the trajectory of horizontal well shall be designed along the direction of minimum major stress and the fracturing perforation shall be arranged in the zone with smaller maximum/minimum earth stress difference along the direction of maximum ma- jor stress.