基于CBIL回波时间图像识别地应力方向

Identification of earth stress direction based on CBIL echo time image.

常规测井资料在地应力的计算中已发挥了重要的作用,但难于准确地确定地应力的方向。井周声波成像测井(CBIL)回波时间图像能够直观地反映储层应力作用下的井壁表现如井眼崩落、裂缝等,根据这些应力响应特征可以判断储层的应力方向。回波时间最长的方向为最小地应力方向,最大地应力方向与之垂直。采用最小二乘法回归井径与回波时间的线性刻度系数,通过回波时间图像刻度成井径图像确定井眼崩落的方位,从而确定最小地应力的方位。结果表明,该方法能够有效地识别地应力的方向。

Conventional log data has played an important role in cal- culation of earth stress,but they are unable to determine direc- tions of earth stresses accurately.The echo time image of cir- cumferential borehole imaging log(CBIL)can visually depict the behaviors of borehole wall such as wellbore avalanche, fracturing under reservoir bed stress.Directions of earth stres- ses then can be determined according to the characteristics of earth stress responses.The direction of longest echo time is the direction of minimum earth stress,and the direction of greatest earth stress is perpendicular to it.We calculated the linear scaling coefficients for borehole diameter and echo time by the least square regression,and inferred the orientation of minimum earth stress by scaling echo time into borehole diame- ter.Real data tests showed that the directions of earth stresses were effectively determined by the proposed method.