斜直井段套管-水泥环组合系统受力特性分析

为分析斜直井条件下套管-水泥环-地层组合系统的受力特性,将地层主应力通过坐标变换转换到井眼轴线与垂直于井眼轴线平面所确定的坐标系上,将变换后的应力张量进行分解,得到3个新的应力张量,以3个新应力张量为边界条件建立相应的线性方程组,并计算地层主应力3种条件下斜直井中系统各接触表面的应力分布,对比不同井斜角条件下的应力分布规律。结果表明:地层3个主应力大小关系不同时得到的斜直井下套管-水泥环界面的径向接触应力随井斜角的变化规律不同,在某些地层下水平井的套管抗外挤能力大于同等条件下直井的套管抗外挤能力,而在另一些地层下直井的套管抗外挤能力大于同等条件下水平井的套管抗外挤能力。

Mechanical analysis of casing-cement ring under non-uniform in-situ stress during inclined well drilling

In order to perform the mechanical analysis of the casing, cement ring and nearby formation in an inclined well drilling, the three principal formation stresses were transformed into a new coordinate system constituted of the borehole axis and the plane perpendicular to the axis. Under the new coordinate system, three new stress tensors were obtained, which can be used as the basis for the boundary condition to establish the relevant control equations. The stress distributions on the interfaces between casing, cement and formation in the inclined well system were calculated using the new three principal formation stress relationships, along with the variations of the stress distribution with different deviation angles. Analysis results show that the variations of the stress distribution with the deviation angle are different because of the differences in the three principal formation stress relationships. Under certain geological conditions, the anti-collapse capability of the casing in a horizontal well can be greater than that in a vertical well, and vice versa, if the geological condition changes.