基于三维地应力的水平井轨道优化及钻井液密度窗口分析

Trajectory optimization of horizontal well and design of drilling fluid density window based on 3D ground stress

准噶尔盆地南缘区域断层多、背斜构造明显,地应力分布复杂,主应力方向随位置变化较大,不利于水平井轨道优化及钻井液密度窗口设计。为此,在三维地应力场计算模型建立过程中考虑了背斜构造对局部应力的影响,数值求解得到的地应力分量值比采用解析法得到的地应力值更准确;相应地,在此基础上计算得到的钻井液密度窗口值比利用解析法得到的钻井液密度窗口值更准确。首先对区块内的高探1井进行单井实测及单井地应力分析,然后对目标区块三维地应力场进行精细化有限元建模计算,从而得到区块的三维地应力场数值解;根据三维地应力场中主应力的方向角分布情况,优化水平井轨道,并计算出相应的安全钻井液密度窗口,为高泉区块安全优快钻井提供理论依据和准确的参考数据。研究表明基于三维地应力的水平井轨道优化及钻井液密度窗口计算模型是准确的、实用的。

Along the southern margin of the Junggar Basin,there are many faults and anticlinal structures are obvious,so the distribution of ground stress is complicated and the direction of the principal stress varies greatly with the position,which is unbeneficial to the trajectory optimization of horizontal well and the design of drilling fluid density window.To this end,the influence of anticlinal structure on local stress is considered while the 3D ground stress field calculation model is established.The ground stress component calculated by the numerical method is more accurate than that obtained by the analytical method.And correspondingly,the drilling fluid density window calculated by the numerical method is more accurate than that obtained by the analytical method.In this paper,single-well measurement and single-well ground stress analysis were firstly carried out on Well Gaotan 1 in this block.Then,fine finite element modeling and calculation was performed on the 3D ground stress field in the target block,so as to obtain the numerical solution of the 3D ground stress field in the block.Finally,based on the distribution of the directional angle of the principal stress in the 3D ground stress field,the trajectory of horizontal well was optimized and the corresponding safety drilling fluid density window was calculated,so as to provide theoretical basis and accurate reference data for the optimized,safe and fast drilling in Gaoquan Block.In conclusion,the model for the trajectory optimization of horizontal well and the calculation of drilling fluid density window based on 3D ground stress is accurate and practical.