基于分步有限元法的多级压裂过程中套管应力敏感性分析

发布时间：2018-01-16 22:27

本文关键词：基于分步有限元法的多级压裂过程中套管应力敏感性分析　出处：《科学技术与工程》2017年16期 　论文类型：期刊论文

【摘要】：目前中国四川地区页岩气开发大多采用大排量分段压裂工艺技术,部分页岩气井在施工过程中出现套管变形的现象,导致后续施工改造无法顺利进行,严重影响了页岩气井的正常生产。因此准确了解压裂过程中套管应力的变化规律具有重要意义。区别于传统模型,基于分步有限元方法,考虑了钻井、完井、压裂整个施工过程,构建了页岩各向异性下套管-水泥环-地层组合体有限元分析模型,模拟多级压裂过程中组合体应力以及温度场随时间的变化特征。分析了两种模型下注液温度、套管内压、地应力变化、地层孔隙压力变化、水泥环弹性模量以及地层弹性模量等因素对套管受力状态的影响。研究结果表明:(1)压裂过程中,采用传统模型会低估套管应力的增大程度;(2)大排量压裂施工过程中,井筒内温度震荡变化,注液温降导致套管应力明显升高;(3)地应力分均匀性以及孔隙压力的增大会导致套管应力有所增加;(4)页岩各向异性对套管应力的影响较小,其中地层性质的下降会导致套管损坏的几率增加。因此在今后的页岩气压裂改造过程中,有必要采用分步有限元模型,综合考虑这些影响因素,合理优化相关的压裂作业参数,从而确保后续压裂完井作业的正常进行。
[Abstract]:At present, most of shale gas development in Sichuan area in China adopts fracturing technology with large displacement, and some shale gas wells appear casing deformation in the process of construction, which leads to the failure of subsequent reconstruction. Therefore, it is very important to understand the variation of casing stress in fracturing process. Different from the traditional model, drilling and completion are considered based on step finite element method. In the whole process of fracturing, the finite element analysis model of casing cement ring-formation combination under shale anisotropy is established. The variation characteristics of stress and temperature field with time in multistage fracturing are simulated. The changes of injection temperature, casing pressure, in-situ stress and pore pressure are analyzed. The influence of elastic modulus of cement sheath and formation elastic modulus on casing stress state. The results show that the traditional model can underestimate the increase of casing stress in the process of fracturing. 2) in the process of large displacement fracturing, the casing stress is obviously increased due to the temperature fluctuation in the wellbore and the temperature drop of the injection fluid; (3) the uniformity of in-situ stress and the increase of pore pressure will lead to the increase of casing stress. (4) the anisotropy of shale has little effect on casing stress, and the decrease of formation property will increase the probability of casing damage. It is necessary to adopt the stepwise finite element model, consider these influencing factors synthetically, and optimize the relevant fracturing operation parameters reasonably, so as to ensure the normal operation of the subsequent fracturing and completion operations.
【作者单位】：中国石油大学(北京)石油与天然气工程学院;北京工业大学;
【基金】：中国石油西南油气田公司页岩气开发事业部科研项目(XNS21JS2014-04) 国家自然科学基金重点项目(51334003) 中国石油科技创新基金研究项目(2012D-5006-0303)资助
【分类号】：TE377
【正文快照】： 科研项目(XNS21JS2014-04)、国家自然科学基金重点项目(51334003)、中国石油科技创新基金研究项目(2012D-5006-0303)资助引用格式:范明涛,李军,柳贡慧.基于分步有限元法的多级压裂过程中套管应力敏感性分析[J].科学技术与工程,2017,17(16):50—55Fan Mingtao,Li Jun,Liu Gongh

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