欠平衡钻井井底岩石的应力状态  

Stress state of bottom-hole rocks in underbalanced drilling

作　　者：李士斌[1] 窦同伟 董德仁 张海军 王敏[2] 刘天恩 

机构地区：[1]东北石油大学提高油气采收率教育部重点实验室,黑龙江大庆163318 [2]中国石油大港油田公司钻采工艺研究院,天津300280

出　　处：《石油学报》2011年第2期329-334,共6页Acta Petrolei Sinica

基　　金：黑龙江省教育厅科学研究项目(11541005)"调整井岩石可钻性预测及应用技术研究"资助

摘　　要：欠平衡钻井较常规钻井钻速高,这与其井底待破碎岩石所处的应力状态有着密不可分的关系,而井底岩石的应力状态受地层孔隙压力和温度的共同影响。基于流-固-热三场全耦合基本理论,根据欠平衡钻井中井底待破碎岩石所处的实际状态,对耦合控制方程加以简化,结合与井底岩石应力状态分析相适应的边界条件,利用有限单元法研究了欠平衡钻井过程中地层孔隙压力和地层温度对井底岩石应力状态的影响机理。研究结果表明,随着钻井液液柱压力和井底岩石温度的降低,井底岩石的各个主应力均在减小,降低程度与压差和温差有关:压差和温差越大,井底岩石的各个主应力减小幅度越大。降低速率与岩石渗透率和热传导率有关,渗透率和热传导率越大,井底岩石的各个主应力变化越快,地层孔隙压力辅助破岩的效率越低。Compared with conventional drilling,the higher speed of underbalanced drilling correlates closely to the stress state of bottom-hole rocks to be broken up,and the stress is co-affected by both pore pressure and temperature of strata.Based on the theory of a fully coupled thermal-hydro-mechanical field,the present paper simplified coupled equations according to the actual state of bottom rocks to be broken up in underbalanced drilling,and with the combination of boundary conditions corresponding to the stress analysis of bottom-hole rocks,it used the finite element method to explore the mechanism of influence exerted by pore pressure and temperature of strata on the stress state of bottom-hole rocks.The results showed that every principal stress of bottom rocks decreased with decreasing the drilling fluid pressure and temperature of bottom rocks,in which the reducing degree was related with differences in pressure and temperature,the more the differences,the greater the reducing degree of each principal stress of bottom rocks,moreover,the reducing rate was related with the permeability and thermal conductivity of rocks,the higher the permeability and thermal conductivity,the faster the change of each principal stress of bottom rocks,while the efficiency of breaking rocks assisted by pore pressure of strata was relatively lower.

关 键 词：欠平衡钻井 流-固-热三场全耦合 井底岩石应力状态 有限单元法 数值模拟 

分 类 号：TE249[石油与天然气工程—油气井工程]