关键词: 定向井, 套管应力, 地应力, 井眼轨迹, 有限元分析

Abstract: A 3D finite element model for calculating the casing stress in the directional wells was developed based on the theory of coordinate conversion. The rock laboratory tests and conventional casing sizes in the field were used to calculate the maximum effective stress varying with deviation angle and azimuth angle under different combinations of in-situ stresses and formation property. Three different situations were considered for the in-situ stress. (1) The overburden stress is the maximum principal one, and the horizontal stresses are uniform. (2) Similar to situation (1), but the horizontal stresses are non-uniform. (3) The overburden stress is the middle principal one. It is found that the casing stress in the directional well is significantly affected by the complex in-situ stress field, well track and the formation property. An optimal well track exists for any combination of these factors. All these factors should be carefully considered in the casing design process.

Key words: directional well, casing stress, insitu stress, wellbore track, finite element analysis