气井环空带压对水泥环力学完整性的影响  

The Effect of Sustained Casing Pressure on the Mechanical Integrity of Cement Sheath in Gas Wells

作　　者：张智[1] 许红林[2] 刘志伟[1] 李巍 施太和[1] 

机构地区：[1]"油气藏地质及开发工程"国家重点实验室.西南石油大学,四川成都610500 [2]重庆科技学院石油与天然气工程学院,重庆沙坪坝401331 [3]中国石油川庆钻探工程有限公司钻采工程技术研究院,四川广汉618300

出　　处：《西南石油大学学报（自然科学版）》2016年第2期155-161,共7页Journal of Southwest Petroleum University(Science & Technology Edition)

基　　金：国家自然科学基金(51244007);四川省科技厅项目(2016JQ0010);四川省省属高校科技创新团队建设计划(13TD0026)

摘　　要：受井下作业、油套管或封隔器泄漏等因素产生的井口环空带压,使高温高压气井水泥环密封完整性面临巨大挑战。为此,基于弹性力学多层厚壁圆筒理论和摩尔库仑失效准则,建立了水泥环应力和失效计算模型,研究了环空带压对水泥环胶结面应力和失效的影响。结果表明,环空带压将增大水泥环胶结面的切向拉应力,过大的切向拉应力将导致水泥环失效。与此同时,井筒温度增加产生的切向拉应力也会增大水泥环失效风险。环空带压越大,水泥环安全系数越低,且温度效应对安全系数的影响较小。对高温高压气井,可根据井身结构(地层-水泥环-套管)参数建立水泥环安全系数图版,从而为确定合理的最大允许环空带压值提供依据,研究结果对提高气井井筒安全性、延长开采寿命具有重要意义。Sustained casing pressure （SCP）, resulted from downhole operations, the leakage of casing and oil tube or packer poses great challenges to the sealing integrity of cement sheath in HTHP gas wells. Thus, we estasblished the failure calculation model and the stresses of cement sheath, and studied the influences of SCP on the stresses and failure of cement sheath, based on the multi-layer thick wall cylinder theory of elastic mechanics and Mort-Coulomb failure criterion. Results show that the SCP problem will make cement sheath sustain overlarge tangential tensile stress which is the principal factor for its failure. Besides, the tangential tensile stress that is resulted from the increasing temperature in wellbore will increase the risk of the failure of cement sheath. The larger the SCP value, the lower the safety factor of cement sheath, and the influence of temperature effect on the safety factor is not clear. For high temperature and high pressure gas wells, a safety factor diagram of cement sheath can be drawn according to parameters of well construction （formation-cement sheath-casing）, which gives the basis for determining proper allowable maximum SCP value and is of great guiding significance to increase the wellbore safety and to extend the working life of gas well production.

关 键 词：气井 高温高压 水泥环 解析模型 环空带压 应力 失效 

分 类 号：TE256[石油与天然气工程—油气井工程]