Determination of the Cement Sheath Interface and the Causes of Failure in the Completion Stage of Gas Wells

作     者：Xuesong Xing Renjun Xie Yi Wu Zhiqiang Wu Huanqiang Yang 

作者机构：CNOOC Research InstituteBeijing100027China Yangtze UniversityWuhan430100China 

出 版 物：《Fluid Dynamics & Materials Processing》 (流体力学与材料加工（英文）)

年 卷 期：2022年第18卷第6期

页      面：1719-1735页

核心收录：

学科分类：07[理学] 0817[工学-化学工程与技术] 070204[理学-等离子体物理] 0703[理学-化学] 0814[工学-土木工程] 0702[理学-物理学] 

基　　金：The authors gratefully acknowledge the CNOOC scientific research project“Study of risk assessment and countermeasures of well drilling and completion under ultrahigh temperature and high pressure”and“Research on development feasibility of LS25-1 gas field”(Grant Nos.YXKY-ZX-09-2021 2020FS-08). 

主　　题：Gas well completion cement sheath sealing failure interfacial bonding strength damage plasticity model 

摘      要：The bonding quality of the cement sheath interface decreases during well completion because of the change in the casing pressure.To explore the root cause of such phenomena,experiments on the mechanical properties and interface bonding strength of a cement sheath have been carried out taking the LS25-1 high-temperature and high-pressure(HTHP)gas field as an example.Moreover,a constitutive model of the cement sheath has been defined and verified both by means of a full-scale HTHP cement sheath sealing integrity evaluation experiment and three-dimensional finite element simulations.The results show that the low initial cementing surface strength is the root cause of cement sheath interface bonding failure.When the pressure in the casing exceeds a certain limit,the stress caused by the change in the internal pressure in the casing is transmitted to the cement sheath,resulting in the degradation of the interface stiffness of the cement sheath.However,with an increase in the casing wall thickness,the stress transmission capacity decreases.Therefore,it is concluded that improving the interfacial cementing strength,appropriately increasing the casing wall thickness and increasing the initial stress of the cement sheath are the keys to ensuring the sealing integrity of the cement sheath in high-temperature and high-pressure gas wells.