实验分析泥岩水化膨胀应力与力学参数之间的关系徐力群1刘厚彬.docVIP

实验分析泥岩水化膨胀应力与力学参数之间的关系 徐力群 刘厚彬 孟英峰 （1．“油气藏地质及开发工程”国家重点实验室 西南石油大学） 摘要：在钻井的过程中，泥页岩地层一旦与水基钻井液接触后，便会发生水化膨胀作用，在地层压力和上覆岩层压力的约束下产生膨胀应力，岩石强度降低，井壁稳定性下降。因此，研究水化膨胀作用与力学参数之间的关系是研究泥岩井壁稳定的关键内容之一。本文基于泥页岩的水化作用机理，通过室内实验分析了水基钻井液中的离子类型及其浓度对水化膨胀应力的影响，并且测量了岩样水化后的力学参数。实验结果表明泥岩水化膨胀应力与离子类型和浓度有关；水化后泥岩的含水量越大，产生的线膨胀应力越大，力学参数越小；线膨胀应力与泥岩水化后的力学参数之间具有较好的指数递减关系。 关键词：泥岩；线膨胀应力；含水量；力学参数 Experiment Study on Relationship between Swelling Pressure and Mechanical Parameters XU Liqun LIU Houbin MENG Yingfeng (State-key laboratory of oil and gas reservoir geology and exploitation, southwest petroleum university, Chengdu) Abstract: Wellbore instability in mudstone formation often occurs when mudstone contacts with the water based drilling fluid. Therefore, the research on the influence of mudstone hydration on rock strength is one of key contents in the study of the wellbore stability of mudstone formation. This laboratory experiment measured swelling pressure in different ion types and contents. Moreover，axial compressive tests were performed to investigate the impact of water content on compressive strength of mudstone. The results show that the ion types and the content had an influence on the swelling pressure of mudstone. In addition, it is shown that the swelling pressure increased with the water content increasing, however, mechanical parameters decreased with the water content increasing. Also, results show that there was a good exponential decay relationship between the swelling pressure and mechanical parameters. Key words: mudstone; swelling pressure; water content; mechanical parameters 0 前言 据统计[1]在油气开采的过程中约有90%的地层是泥页岩地层，并且75%的钻井事故都与泥页岩地层有关。由于泥页岩地层水敏性强，一旦与水基钻井液接触后容易发生井壁失稳事故。而井壁失稳是油气田开发过程中最复杂并且花费最高的事故[2]。因此国内外学者[3,4,5,6,7]针对泥页岩水化导致井壁失稳做了大量研究。其中Chenevert和Yew[8,9]利用实验和热弹性理论模拟研究了水化作用对岩石强度的影响，其研究结果表明岩石的弹性模量和吸水量成较好的线性关系。孟英峰等[10,11]利用扩散双电层理论和范德华理论定量分析了泥页岩水化作用对岩石强度的影响，其研究结果表明泥页岩水化后岩石强度降低的根本原因是粘土矿物之间的作用力减弱。黄荣樽[12]利用大庆油田泥页岩天然岩心得出岩石的弹性模量与吸水量成指数关系，并且得出了内聚力和内摩擦角与含水量之间的经验关系。本文结合前人的研究成果，通过室内实验系统的测量了水基钻井液中不