川西彭州地区雷四段地层区域应力场分布规律及应用

Distribution Law of Regional Stress Field in Lei 4th Member in Pengzhou Area,Western Sichuan

由于对川西彭州地区雷四段地应力分布规律认识不足,井壁失稳问题频发。基于地震解释成果建立了区域三维地质模型,采用室内实验和测井资料确定了模型的岩石力学参数,运用有限元方法模拟了研究区目的层地应力场。结果表明,最小水平主应力为87.30~136.43 MPa,最大水平主应力为122~190.57 MPa;高应力主要集中在研究区西南部和背斜两翼,由于断层应力得到释放,应力最小,而断层周围因岩石变形但未破碎,表现为应力集中;断层区域的地应力方向发生了偏转,断层走向越接近地应力方向,应力方向偏转程度越小。以7-1D井为例,结合地应力预测结果,绘制了该井坍塌压力方位变化图,为井壁稳定性评价提供参考。研究成果能为川西彭州地区雷四段地层的井壁失稳防治和施工提供有效指导。

Due to the lack of understanding of the geostress distribution law of Lei-4 member in Pengzhou area,western Sichuan,the problem of wellbore instability occurs frequently.Based on the results of seismic interpretation,a regional 3D geological model was established,and the rock mechanics parameters of the model were determined using laboratory experiments and logging data.The ground stress field of the target layer in the study area was simulated using the finite element method.The results show that the minimum horizontal principal stress is 87.30~136.43 MPa,and the maximum horizontal principal stress is 122~190.57 MPa.The high stress is mainly concentrated in the southwest of the study area and the two wings of the anticline.As the fault stress is released,the stress is minimal,while the rock around the fault is deformed but not broken,showing stress concentration.The geostress direction in the fault area is deflected.The closer the fault strike is to the geostress direction,the less the deflection of the stress direction is.Taking well 7-1D as an example,combined with the prediction results of geostress,the azimuth variation diagram of collapse pressure of the well is drawn to provide reference for the evaluation of wellbore stability.The research results can provide effective guidance for wellbore instability prevention and construction of Lei-4 formation in Pengzhou area,western Sichuan.