第40卷第2期
天然气勘探与开发
气井重复压裂前应力场分析
杨林12卢聪1朱鹏2
1.西南石油大学石油与天然气工程学院2.中国石油川庆钻探工程公司井下作业公司
“用并发
重复压裂是针对初次压裂作用失效，或具备提高油气产量潜力的并进行再次压裂改造的工艺措施。研究重复压裂造
摘要
缝机理及裂缝转向机理可以提高重复压裂的成功率和大幅度提高油气井产量。四川盐地川西地区作为重要的天然气生产基地，目前有相当多的压聚井失去了增产功能，需要重复压裂提高气井产能。为此，基于应力场分布理论，以川西地区某并为例，结合气井地质特征，采用有限元分析方法建立模型对并简周图应力场、初次人工聚缝产生的诱导应力场以及生产过程中孔隙压力改变产生的诱导应力场进行仿真，结果表明：①诱导应力集中位于裂缝尖端，高裂缝越远诱导应力越低；①不考虑流固耦合情况下，孔隙压力增大，应力转向距高减小；①并眼周图应力场转向范图随着原地应力差的增大面减小；①生产压差越大越容易产生地应力转向：④续宽越大、裂续越长越容易发生地应力转向。本模型可快速模拟井筒及裂缝周图应力场转向范图，确定重复压裂是否产
生新裂缝和重复压裂的最佳时机，对优化压聚施工设计、提高重复压聚成功率具有十分重要的作用。关键词气井重复压聚应力场
应力场转向模型计算
有限元分析法孔隙压力
人工裂缝
DOI: 10.12055/gaskk.issn.1673-3177.2017.02.012
Analysisofstressfieldbeforerefracturingofgaswells
Yang Lin'2, Lu Cong',ZhuPeng
(1.School of Oil &Natural Gas Engineering.Southwest Petroleum University, Chengdu,Sichuan 610500,China; 2.Downhole Operation Company,CNPC ChuanqingDrillingEngineering Company Limited,Chengdu,Sichuan 710000, China)
Abstract: Refracturing is a treatment that repeated fracturing is conducted in the well which fails in fracturing or has the potential in increasing oil and gas production. The study of fracture-creating mechanism and fracture-diverting mechanism in refracturing can help to increase the success rate of refracturing and greatly enhance the production of oil and gas wells, In the western Sichuan Basin, as an important natural gas production base, a considerable number of fracturing wells are disabled for increasing production, and accord-ingly refracturing is necessary to improve gas production, Based on the theory of stress field distribution and taking a well in western Sichuan Basin as an example, a model was built through finite element analysis to simulate the stress field around the wellbore, the induced stress field produced by the initial artificial fractures, and the induced stress field produced by the change of pore pressure during the production process. The results show that the stress is concentrated at the tip of the fractures, and the induced stress be-comes gradually lower as it is farther away from the fractures. Regardless of the fluid-solid coupling, the pore pressure increases and the stress diverting distance decreases. The diverting range of the stress field around the wellbore decreases with the increase of the in-situ stress difference., The greater the production pressure difference is, the more likely the in-situ stress diverting will occur. The greater the width and length of the fractures, the more likely the in-situ stress diverting will occur. The model can quickly simuiate the diverting range of the stress field around the wellbore and the fractures, and determine whether refracturing produces new fractures and the best time for refracturing. It is very important to optimize the fracturing design and improve the success rate of refracturing. Keywords: Gas well; Refracturing; Stress field; Finite element analysis; Pore pressure; Artificial fractures; Stress field divert ing; Model calculation
随着初次压裂气井增产能力的逐渐降低，重复压裂技术的应用成为油气开采的重要增产措施。国外在重复压裂方面已具备较深的认识，Dowell 公司在实验和模拟的基础上得出初次裂缝对井眼
附近的地应力场将产生影响、新裂缝将垂直于老裂缝起裂的结论：随后美国很多油气田的重复压裂现场测试也证实了重复压裂新裂缝偏离初次裂缝方位起裂和延伸的规律。国内的大部分油气田也实施
基金项目：国家科技重大专项“低渗砂岩储层提高压裂裂缝复杂程度工艺技术研究”（编号：2016ZX05006002-005)。
第一作者：杨林，1985年生，工程师，硕士研究生：主要从事油气层改造及增产机理方面的研究工作。地址：（610500）四川省成都市新都区新都大道8号西南石油大学石油与天然气工程学院。电话；18113167286，E-mail:359257200@qq.com
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