水力压裂过程中直井段B环空水泥环完整性分析  

Integrity Analysis of Cement Sheath in Annulus B of Vertical Section during Hydraulic Fracturing

作　　者：曾波[1] 王冬 宋毅[1] 连威 李军 Zeng Bo;Wang Dong;Song Yi;Lian Wei;Li Jun(PetroChina Southwest Oil and Gas Field Company;Sichuan Changning Gas Development Co.,Ltd.;China University of Petroleum(Beijing)at Karamay;China University of Petroleum(Beijing))

机构地区：[1]中国石油西南油气田公司 [2]四川长宁天然气开发有限责任公司 [3]中国石油大学(北京)克拉玛依校区 [4]中国石油大学(北京)

出　　处：《石油机械》2022年第8期89-95,共7页China Petroleum Machinery

基　　金：国家自然科学基金联合基金重点项目“页岩气水平井井筒完整性失效机理与控制方法”(U1762211);国家自然科学基金-企业创新发展联合基金课题“海相深层油气富集机理与关键工程技术基础研究-构造应力集中区页岩气井套管载荷模型及结构完整性失效机理”(U19B6003-05-04-02);中国石油天然气集团有限公司重大工程技术现场试验项目“深层页岩气有效开采关键技术攻关与试验”(2019F-31);中石化工程公司项目“威荣区块深层页岩气井筒完整性关键技术研究”(SG18-29K)。

摘　　要：我国页岩气开发过程中井筒环空带压现象普遍,严重影响了页岩气井的井口安全和生命周期。以某实钻页岩气井为例,结合地层岩石力学参数剖面和地应力参数剖面,建立了不同开次条件下套管-水泥环-地层组合体数值计算模型,计算了B环空水泥环的周向/径向应力剖面,利用摩尔库伦准则对水泥环的完整性进行了判定,在此基础上分析了水泥环弹性模量、泊松比和井口泵压对水泥环周向、径向应力以及完整性的影响。研究结果表明:随着井深的增加,水泥环承受的最大径向应力不断增加,周向应力则逐渐降低,甚至由受拉变为受压;表层套管鞋以上的水泥环易发生周向拉伸破坏,以下的水泥环则易发生径向压缩破坏;降低水泥环弹性模量可以降低水泥环的周向/径向应力及摩尔库伦判定值。增加水泥环的泊松比有利于降低其周向应力,但对径向应力几乎没有影响;不同泵压条件下水泥环周向/径向应力及摩尔库伦判定值剖面基本平行,降低泵压有利于水泥环的完整性,压裂过程中应采取技术手段降低页岩的起裂压力。所得结果可为环空带压的控制提供借鉴。In the process of shale gas development in China,the phenomenon of sustained casing pressure(SCP)is widespread,which seriously affects the wellhead safety and life cycle of shale gas wells.Taking a shale gas well as an example,combined with the rock mechanics parameter profile and the in-situ stress parameter profile,the numerical calculation model for the combination of casing-cement sheath-formation under the conditions of different spuddings was established.The circumferential/radial stress profile of cement sheath in annulus B was calculated and the integrity of cement sheath was judged by using the Mohr-Coulomb criterion.On this basis,the influences of elastic modulus and Poisson s ratio of cement sheath and wellhead pump pressure on the circumferential/radial stress and integrity of cement sheath were analyzed.The results show that with the increase of well depth,the maximum radial stress of cement sheath increases,while the circumferential stress decreases gradually,even changing from tension to compression.The cement sheath above the surface casing shoe is prone to circumferential tensile failure,while the cement sheath below it is prone to radial compressive failure.Reducing the elastic modulus of cement sheath can reduce the circumferential/radial stress of cement sheath and the Mohr-Coulomb criterion value.Increasing Poisson s ratio can reduce the circumferential stress of cement sheath,but it has little influence on the radial stress.Under different pump pressure conditions,the circumferential/radial stress of cement sheath and the Mohr-Coulomb criterion profile are basically parallel.Reducing pump pressure is beneficial to the integrity of cement sheath.During fracturing,technical measures should be taken to reduce the fracturing pressure of shale.The results provide reference for the control of sustained casing pressure.

关 键 词：页岩气 环空带压 B环空 周向应力 径向应力 摩尔库伦准则 

分 类 号：TE934[石油与天然气工程—石油机械设备]