井壁稳定性评价准则分析  

Analysis of failure criterions on wellbore stability prediction

作　　者：冯永存[1] 邓金根[1] 李晓蓉[1] 蔚宝华[1] 

机构地区：[1]中国石油大学(北京)石油工程教育部重点实验室,北京102249

出　　处：《断块油气田》2012年第2期244-248,共5页Fault-Block Oil & Gas Field

基　　金：国家科技重大专项"大型油气田及煤层气开发"子课题"煤层气钻井工程技术及装备研制"(2008ZX05036)

摘　　要：井壁坍塌失稳大多由于井周岩石的剪切破坏造成,而剪切破坏准则的选择是井壁稳定性预测的关键因素。通常使用的Mohr-Coulomb准则和Drucker-Prager准则都存在明显的缺点,致使井壁稳定性预测结果不准确。于是,引进了一种新的破坏准则——Mogi-Coulomb准则。该准则较为合理地考虑了中间主应力对岩石强度的影响,使强度预测结果更加准确。为验证其优势,利用岩石真三轴试验数据对3种准则的强度预测结果进行了对比分析。结果表明:在真三轴应力状态下,Mogi-Coulomb准则预测岩石强度的精度要高于Mohr-Coulomb准则和Drucker-Prager准则,且具有表达简单、使用方便、预测结果准确等优点。因此,建议推广使用Mogi-Coulomb准则预测井壁稳定性。Wellbore collapse is mostly caused by the shear failure of the rock around borehole. One of the key considerations on wellbore stability prediction is the choice of shear failure criterion. The commonly used Mohr-Coulomb and Drucker-Prager failure criterions have obvious shortcomings, which leads to the unrealistic predicting resnhs. Therefore, a new failure criterion, Mogi- Coulomb criterion, is introduced in this paper. The advantage of this criterion is that it properly evaluates the effect of intermediate principal stress on rock strength, thus it has more accurate prediction result. In order to present its advantage, the prediction results of rock strength predicted by the three criterions above are compared based on true triaxial test data. The results indicate that, under true triaxial stress state, it is more precise to predicate rock strength using the Mogi-Coulomb criterion rather than using the Mohr- Coulomb and Drucker-Prager failure criterions. In view of the advantages of the Mogi-Coulomb criterion, such as simple expression, easy to use and high prediction accuracy, it is highly recommended to use the shear failure criterion in the analysis of future wellbore stability.

关 键 词：破坏准则 Mogi—Coulomb准则 中间主应力 真三轴试验数据 井壁稳定性 

分 类 号：TE21[石油与天然气工程—油气井工程]