体积压裂套管剪切变形载荷分析及强度设计  

Casing Shear Deformation Load and Strength Design during Volume Fracturing

作　　者：曾义金 孟胡[3] 周仕明 葛洪魁 陶谦[1,2] 王小琼[3] ZENG Yi-jin;MENG Hu;ZHOU Shi-ming;GE Hong-kui;TAO Qian;WANG Xiao-qiong(State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development, Beijing 100083, China;Research Institute of Petroleum Engineering, SINOPEC, Beijing 100101, China;Unconventional Oil and Gas Science & Technology Institute, China University of Petroleum(Beijing), Beijing 102249,China)

机构地区：[1]页岩油气富集机理与有效开发国家重点实验室,北京100083 [2]中国石油化工股份有限公司石油工程技术研究院,北京100101 [3]中国石油大学(北京)非常规油气科学技术研究院,北京102249

出　　处：《科学技术与工程》2021年第29期12529-12535,共7页Science Technology and Engineering

基　　金：中石化页岩油气富集机理与有效开发国家重点实验室开放基金。

摘　　要：页岩气开发过程中井筒穿越天然裂缝/断层,体积压裂时天然裂缝/断层容易被激活,导致套管剪切变形,套管内径缩小,井下工具无法下入。目前对套管剪切变形条件下的受力分析较少,现有研究主要采用套管Mises应力屈服准则判断套管失效,该准则对于套管大剪切变形问题已不适用。为探究天然裂缝/断层滑移导致的套管剪切变形问题,建立套管-水泥环-地层组合体有限元模型,对位移载荷作用下的套管力学行为进行研究。分析了各因素对套管受力及缩径量的影响,并提出套管缩径量与应力相结合的套管外载设计方法。研究结果表明:套管剪应力及Mises应力随地层滑移量增大而增大,在10 mm滑移量作用下,套管Mises应力已超过屈服强度,建议采用剪切载荷进行强度校核;套管缩径量主要集中在距离滑移面1 m范围内,套管局部区域出现膨胀现象;考虑套管变形量的载荷设计可以有效防止体积压裂过程中套管变形导致压裂工具无法下入的问题。In the process of shale gas development,the wellbore crosses natural fracture/fault,which are easily activated during volume fracturing,resulting in casing shear deformation,casing inner diameter reduction,and the failure of downhole tools to enter.At present,few stress analyses have been conducted on casing shear deformation.Existing researches mainly adopt the Mises stress yield criterion to judge casing failure,which is not suitable for large shear deformation of casing.To research the casing shear deformation caused by natural fracture/fault slip,a finite element model of casing-cement sheath-formation was established,and the mechanical behavior of casing under displacement load was studied.The various factors on casing stress and shrinkage were analyzed,and a casing load design method combining the reduction of diameter and stress was proposed.The results shou that casing shear stress and Mises stress increase with the slip distance of formation,and the casing Mises stress has exceeded the yield strength under the 10 mm slip distance.It is recommended to use shear load to check the strength.Casing shrinkage is mainly concentrated within 1 m distance from the slip surface,and the casing expansion occurs in the local area.Load design considering the casing deformation can effectively avoid the failure of fracturing tools to run normally during volume fracturing.

关 键 词：体积压裂 地层滑移 套管剪切变形 外载设计 

分 类 号：TE243[石油与天然气工程—油气井工程]