热采水平井套管应力分析的摄动有限元方法

开采稠油更多地用水平井注蒸汽方式进行热采 ,而热采水平井套管的应力分析是一个复杂的三维力学问题 ,采用通用有限元程序进行分析的计算量大、机时长。为了有效地解决这个问题 ,针对水平井的几何和结构特点 ,先从普适的弹性力学方程出发 ,导出水平井套管在自然坐标系下的弹性力学方程。然后 ,利用摄动方法把三维问题转化为类轴对称问题 ,并采用环向有限单元的剖分方式 ,建立起相应的有限元方程 ,简化了问题的求解。同时 ,还揭示了热采水平井条件下剪切应力和轴向位移的变化规律 ,给出了水平井井口隆起等现象的合理解释

Perturbation finite element method for stress analysis of horizontal well casing during thermal production

The stress analysis of the horizontal well casing in petroleum recovery is a three dimensional problem which would require large amount of CPU time using a general finite element method (FEM) program. A more efficient method is developed using a combination of perturbation methods and finite element methods. The geometric and structural characteristics of the horizontal well are used to develop a group of general control elastic mechanical equations for the horizontal well using natural coordinates. Then the perturbation method is introduced to simplify the problem from three dimensional to two dimensional with a radius relative non dimensional parameter. Finally, the structure is separated into circumferential finite elements using new FEM equations. A software procedure is then developed and applied to analyze practical horizontal well stress conditions. The analysis method not only simplifies the problem but also reveals the variation mechanism of the shearing stress and the axial displacement of the horizontal well due by thermal effects, and explains why the ground part of the horizontal well is uplifted during thermal production.