体积压裂时套管弯曲应力放大计算分析  

CALCULATING CASING BENDING STRESS AMPLIFICATION DURING SRV FRACTURING

作　　者：董文涛[1,2] 吴萌 张弘 申瑞臣[3] 付利 DONG Wentao;WU Meng;ZHANG Hong;SHEN Ruichen;FU Li(Research Institute of Petroleum Exploration&Development,Beijing 100083,China;Panjin Industrial Technology Research Institute of Dalian University of Technology;CNPC Engineering Technology Research Institute,Beijing 102206,China)

机构地区：[1]中国石油勘探开发研究院 [2]大连理工大学盘锦产业技术研究院 [3]中国石油集团工程技术研究院有限公司

出　　处：《钻采工艺》2018年第5期9-11,15,131,共5页Drilling & Production Technology

基　　金：中石油集团公司项目"页岩气钻采工程现场试验-浙江油田昭通示范区页岩气钻采工程技术现场试验"(编号:2014F-4702-05)

摘　　要：页岩气井体积压裂过程中套管所处力学环境复杂,体积压裂中套管受力情况目前尚未得到清晰的解释。针对此力学问题,研究认为存在套管应力放大的问题,文章系统阐述了体积压裂过程中套管弯曲应力放大诱因,建立了轴向拉力下套管弯曲应力放大模型,推导了弯曲应力放大计算公式。结果表明,轴向拉力和狗腿角是影响体积压裂中套管弯曲应力放大的主要因素,水泥环虚空段长度影响较小。此外,拉-弯应力与泵压联合作用使套管抗外挤强度降幅达23. 7%,套管抗外挤安全系数已经低于三轴安全系数规定值,严重威胁套管安全,极易在体积压裂中诱发套变。最后,文章提出规避体积压裂套管弯曲应力放大的技术对策。During the SRV fracturing in shale gas well,casing is under a complex mechanical environment which is still unknown by us.In this paper the mechanism of casing bending stress amplification during SRV fracturing is systematically demonstrated.A bending stress amplification model and related calculation formula are set up based on the theory of mechanics of materials and differential equations of the space curve.The results show that axial tension and dogleg pose a huge impact on the bending stress amplification,while the cement void length does little effect.In this paper the collapse resistance of casing in shale gas well during SRV fracturing is also calculated with bending stress amplification model.The results show that casing collapse resistance is reduced about 23.7%under the tension-bending stress and pump pressure,the casing collapse resistance safe factor is already lower than the triaxial safe factor standard.This can easily induce casing failure during fracturing.Measures for casing bending stress amplification during SRV fracturing are given in this paper.

关 键 词：弯曲应力放大 体积压裂 计算模型 套管强度 

分 类 号：TE931.2[石油与天然气工程—石油机械设备]