水泥环孕育机理及其压裂工况下密封力学分析  

Cement ring gestation mechanism and seal mechanical analysis with fracturing conditions

作　　者：张承武 武月荣[1,2] 王坤 ZHANG Chengwu;WU Yuerong;WANG Kun(Technology&Engineering Research Institute CCDC,Xi′an Shaanxi 710018,China;National Engineering Laboratory of Low-Permeability Oil&Gas Fields Exploration and Development,Xi′an Shaanxi 710018,China)

机构地区：[1]中国石油川庆钻探工程有限公司工程技术研究院,陕西西安710018 [2]低渗透油气田勘探开发国家工程实验室,陕西西安710018

出　　处：《油气井测试》2024年第1期6-13,共8页Well Testing

基　　金：中国石油集团科研项目“集团公司侧钻井技术示范与推广”(2019D-4209)。

摘　　要：在油气井压裂过程中,压裂液的高压和降温作用存在破坏水泥环密封性的风险,对于多级压裂或者重复压裂,井筒压力和温度的交替作用加剧了水泥环的破坏,影响多级压裂的效果。研究了水泥环的孕育机理,利用有限元软件对套管—水泥环—地层系统进行了全尺寸等效建模和力学仿真,对多级压裂水泥环的变形和破坏规律进行了定量分析。结果表明,井下水泥环的先天环境压力不同于养护压力,应当归属于水泥环的材料属性;压裂时水泥环表现为环向拉应力破坏,且内侧比外侧更容易破坏;压裂停泵时,水泥环残余变形导致一界面产生剥离应力,如果剥离应力大于一界面的粘结强度,一界面将出现剥离破坏;提高水泥石的抗拉强度和降低弹性模量可提升水泥环的密封性能。该分析为油气井水泥材料的研究提出改进方向,为多级压裂的参数优化提供参考。High pressure and cooling of fracturing fluid produce the risk of destroying the sealability of cement sheath in the process of oil and gas well fracturing.Alternating effect of casing pressure and temperature exacerbates the destruction of cement sheath for multi-stage fracturing or refracturing.It will affect the effect of multistage fracturing.It studied the gestation mechanism of cement sheath,and the full-scale equivalent modeling and mechanical simulation of the casing-cement sheath-formation system are carried out by the finite element software.It quantitatively analyzed the deformation and failure rules of multistage fracturing cement ring.The results show that the inborn environmental pressure of downhole cement sheath is different from maintenance pressure,that should be attributed to material properties of cement sheath;during fracturing,the cement sheath exhibits hoop tensile stress failure,and the inside is easier to break than the outside;when fracturing stops,the residual deformation of cement sheath causes peeling stress at the first interface,if the peel stress is greater than the bond strength of the first interface,the first interface will be stripped;increasing tensile strength and reducing elastic modulus can improve sealability of cement sheath.This analysis provides the improvement direction for the research of cement materials in oil and gas wells and provides reference for parameter optimization of multistage fracturing.

关 键 词：水泥环 密封性 孕育机理 多级压裂 全尺寸建模 力学分析 剥离应力 完整性分析 

分 类 号：TE357[石油与天然气工程—油气田开发工程]