高温高压井水泥环缺失对多层套管应力影响规律

The Influence of Cement Sheath Loss on Multi-layer Casing Stress in High Temperature and High Pressure Wells

宋琳 舒振辉 吴彦先 练章华 史君林

SONGLin SHUZhenhui WUYanxian LIANZhanghua SHIJunlin

中国石油新疆油田公司工程技术研究院, 新疆 克拉玛依 834000 中国石油新疆油田公司工程技术处, 新疆 克拉玛依 834000 油气藏地质及开发工程全国重点实验室·西南石油大学, 四川 成都 610500

Engineering Technology Research Institute, Xinjiang Oilfield Company, PetroChina, Karamay, Xinjiang 834000, China Engineering Department, Xinjiang Oilfield Company, PetroChina, Karamay, Xinjiang 834000, China National Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu, Sichuan 610500, China

由于高温高压井中，固井工况复杂，套管与水泥环之间会出现缺失现象，导致套管损坏，尤其多层套管时上述问题更为突出而复杂。针对上述问题，以准噶尔盆地南缘某高温高压高产气井为研究对象，建立了套管-水泥环缺失-套管-水泥环-套管-地层轴对称有限元模型，模型中水泥环缺失处采用圈闭流体单元，岩石和水泥环采用EDP本构模型，相互界面间用接触力学有限元模型。研究结果表明，该模型能够准确分析复杂条件下水泥环缺失套管受力情况，解决了以前的模型无法模拟水泥环缺失处流固耦合问题；当套管环空出现环状缺失时，水泥环缺失的交界面附近应力最大且水泥环缺失处液体性质对套管强度有较大影响。为保证其井筒完整性，在深井、超深井中，建议优化水泥环返高，使水泥环不返到井口，减小固井段长度，消除水泥环缺失问题。

Due to the complex cementing conditions in high temperature and high-pressure wells, there will be a loss between casing and cement sheath, resulting in casing damage and major accidents, especially in the case of the multi-layer casing. Taking a high-temperature high pressure and high quantity gas well in the southern margin of Junggar Basin as the research object, Based on the finite element principle and method of nonlinear contact problem of the discontinuous medium, the axisymmetric finite element model of casing cement sheath loss casing cement sheath casing formation is established by using ANSYS finite element analysis software, In this model, the hydrostatic fluid element is used at the missing part of the cement sheath, the Extended Drucker Prager constitutive model is used for the rock and cement sheath, and the contact mechanics finite element model is used for all the interfaces. The research results show that: the newly established finite element of cement sheath loss can accurately analyze the stress of cement sheath loss casing under complex conditions, and solve the problems of fluid-solid coupling at the cement sheath loss where the previous model can not simulate; when there is the annular loss between Casing and cement sheath, The maximum stress occurs near the interface where the cement sheath is missing. The lack of cement sheath and the nature of the liquid have a great impact on the casing. In deep and ultra-deep wells, it is recommended to optimize the return height of the cement sheath so that the cement sheath does not return to the wellhead, reduce the length of cementing section, eliminate the problem of cement sheath loss and ensure its wellbore integrity. In addition, maintaining reasonable internal pressure during mining is also one of the effective measures to prevent and control cement sheath loss.

10.11885/j.issn.1674-5086.2021.12.21.01