压裂过程中考虑井眼曲率对套管应力的影响  

Influence of Borehole Curvature on Casing Stress during Fracturing

作　　者：杨钊[1] 孙锐 王鹏[2] 邱森淼 葛薇 苏子龙 Yang Zhao;Sun Rui;Wang Peng;Qiu Senmiao;Ge Wei;Su Zilong(School of Petroleum Engineering,Northeast Petroleum University;Daqing Oilfield Production Technology Institute)

机构地区：[1]东北石油大学石油工程学院 [2]中国石油大庆油田有限责任公司采油工程研究院

出　　处：《石油机械》2022年第8期132-139,148,共9页China Petroleum Machinery

基　　金：中石油科技创新基金项目“致密气藏注热气体提高采收率机理研究”(2019D-5007-0205)。

摘　　要：受井眼曲率变化影响,套管存在弯曲现象,在进行大规模压裂时套损情况严重。为研究井身结构变化对套管应力的影响,基于有限元分析方法,建立了不同井眼曲率半径下全管柱套管-水泥环-地层三维有限元力学分析模型,综合考虑地层弹性模量、套管内壁压力以及地应力场对套管应力分布的影响,并针对徐深气田实际井眼轨迹进行实例分析。分析结果表明:随着曲率半径增大,套管应力呈现减小趋势,套管受力变形集中在造斜点和入靶点初始位置;随着岩石弹性模量不断增加,套管应力呈现减小趋势,当岩石弹性模量大于35 GPa时,套管应力下降幅度大大减缓,岩石弹性模量15 GPa为风险值;施工压力低于74 MPa时,地层弹性模量较高对套管保护作用更为显著;大于40 m的曲率半径钻井可以有效减轻施工压力和地应力共同作用对套管的破坏;在套管的造斜点位置采用高强度材质管柱可以降低套损风险。研究结果对现场预防压裂套管损坏有一定的参考。The change of borehole curvature results in casing bending,and casing damage is serious during large-scale fracturing.In order to study the influence of different casing programs on the casing stress,based on the finite element analysis method,a three-dimensional finite element mechanical analysis model of full string casing-cement sheath-formation with different borehole curvature radius was established.The influences of formation elastic modulus,casing inner wall pressure and in-situ stress field on the casing stress distribution were all considered.The actual borehole trajectory in Xushen Gas Field was analyzed as an example.The results show that with the increase of curvature radius,the casing stress decreases;and the casing stress and deformation concentrate on the initial position of the kick-off point and the target point.With the increase of rock elastic modulus,the casing stress decreases.When the rock elastic modulus is greater than 35 GPa,the decrease of casing stress slows down greatly,and the rock elastic modulus of 15 GPa is the risk value.When the operation pressure is lower than 74 MPa,the higher elastic modulus of the formation has a more significant effect on casing protection.Drilling with radius of curvature greater than 40 m can effectively reduce the casing damage caused by the combination of operation pressure and in-situ stress.The risk of casing damage can be reduced by using high-strength material casing at the kick-off point.The research results have some references for preventing the damage of fracturing casing.

关 键 词：压裂套管 地应力 套管内壁压力 岩石弹性模量 曲率半径 

分 类 号：TE934[石油与天然气工程—石油机械设备]