热固耦合作用下水泥环缺失对套管强度的影响分析  

Analysis of the Influence of Cement Sheath Loss on Casing Strength under Thermal-solid Coupling

作　　者：曹银萍[1] 杜恒 陈刚 窦益华[1] 杨亚龙 Cao Yinping;Du Heng;Chen Gang;Dou Yihua;Yang Yalong(Mechanical Engineering College,Xi’an Shiyou University,Xi’an 710065,China;Panlong Gas Production Plant of Yanchang Petroleum Co.,Ltd.,Yan’an,Shaanxi 716000,China)

机构地区：[1]西安石油大学机械工程学院,西安710065 [2]延长石油股份有限公司蟠龙采气厂,陕西延安716000

出　　处：《机电工程技术》2025年第2期93-99,共7页Mechanical & Electrical Engineering Technology

摘　　要：固井过程中由于井下地形复杂,水泥浆往往难以完全顶替钻井液,致使套管和井眼环空之间形成不完整的固井水泥环,影响套管的强度安全性。为此,在热固耦合的作用下分析水泥环缺失位置、径向缺失厚度、环向缺失角度的差异对套管强度的影响至关重要。通过有限元方法建立套管-水泥环-地层组成的井筒模型,考虑生产过程中产生的热应力、热位移及地层的非均匀地应力,模拟水泥环缺失段套管的Von-Mises等效应力分布情况。结果表明:相较于第二胶结面缺失和水泥环内部缺失,第一胶结面缺失对套管的应力分布影响最大;当缺失角度为30°、第一胶结面缺少厚度比达到1/5时,N80管材套管的最大等效应力为696.7 MPa,已大于管材的最小屈服强度;当水泥环第二胶结面和水泥环内部发生缺失时,套管的等效应力增幅较为平缓,且无应力突变;当水泥环环向缺失角度发生变化时,套管的应力会在75°达到峰值,随着角度继续增大,应力值会逐渐减小。所得结论可为现场评价套管强度提供理论依据。During the cementing process,the complex downhole terrain is often encountered,making it difficult for the cement slurry to completely displace the drilling fluid.This results in an incomplete cement sheath between the casing and the borehole annulus,affecting the strength and safety of the casing.Therefore,the impact of differences in the location,radial thickness,and circumferential angle of cement sheath absence on casing strength under thermal-solid coupling conditions is analyzed.A wellbore model consisting of a casing,cement sheath,and formation is established using the finite element method.The model accounts for thermal stress,thermal displacement,and the nonuniform in-situ stress of the formation during production.It simulates the Von-Mises equivalent stress distribution in the casing for sections with absent cement sheath.The results indicate that the absence of the primary bonding interface has the greatest impact on casing stress distribution compared to the absence of the secondary bonding interface and the internal cement sheath.When the absence angle is 30°and the missing thickness of the primary bonding interface reaches 1/5,the maximum equivalent stress of the N80 steel casing is 696.7 MPa,exceeding the material′s minimum yield strength.When the cement sheath′s secondary bonding interface and internal sections are missing,the equivalent stress increase in the casing is relatively moderate,without stress spikes.As the circumferential angle of the cement sheath absence varies,the stress in the casing peaks at 75°and gradually decreases as the angle increases further.The conclusions obtained in this study provide a theoretical basis for field evaluation of casing strength.

关 键 词：套管 强度安全性 热固耦合 水泥环缺失 有限元分析 

分 类 号：TE256[石油与天然气工程—油气井工程]