基于渗流-应力-损伤耦合模型的泥页岩井壁稳定性研究  

Analysis of borehole stability based on seepage-stress-damage coupling model

作　　者：冉小丰[1] 王越之[2] 贾善坡[3] 易先中[1] 

机构地区：[1]长江大学地热资源开发研究所,湖北荆州434023 [2]长江大学石油工程学院,武汉430100 [3]长江大学城市建筑学院,湖北荆州434023

出　　处：《中国科技论文》2015年第3期370-374,共5页China Sciencepaper

基　　金：国家自然科学基金资助项目(51174036);高等学校博士学科点专项科研基金资助项目(20134220110002)

摘　　要：石油钻井过程中,泥页岩地层井壁稳定性研究十分复杂。本文在连续损伤力学理论基础上,将塑性损伤演化及渗流相互耦合的概念引入Mohr-Coulomb破坏准则,建立了基于等效塑性应变的损伤演化模型,给出了泥岩的渗透性的演化方程。以中国西部某油田实际钻井过程为例,建立了井壁稳定分析模型。计算过程中考虑了围岩损伤引起的弹性模量、黏聚力和渗透系数的变化,得到了井壁围岩损伤、渗透系数、应力、塑性应变、孔隙压力和位移的分布规律。结果表明,井壁附近岩石的损伤演化对围岩塑性区的塑性应变和应力分布有明显影响。钻井液密度的高低,会造成井壁在水平最小主应力方向上的剪切损伤或在水平最大主应力方向上的拉伸损伤。当损伤达到极限时,会造成井壁围岩的破坏。In oil drilling,one of the most complicated problems is borehole stability of shale.Based on the theory of continuum damage mechanics,the concept of coupling plastic damage evolution and seepage stress was introduced into Mohr-Coulomb failure criterion.Meanwhile,the damage evolution model which based on equivalent plastic strain was established and the permeability evolution equation of shale was provided.The physical model of borehole rock for a well in China western oilfield was set up and the evolution of elastic modulus,cohesive force and permeability coefficient caused by rock damage was considered during computation,and the distribution of damage,permeability,stress,plastic strain and displacement was obtained.The results show that the rock damage evolution has significant effects on the plastic strain and stress in plastic zone.Different drilling fluid height will cause the shear damage in minimum principle stress direction or tensile damage in maximum principle stress direction in horizontal plane.When the damage reaches its limit,the failure of the borehole will be occurred.

关 键 词：钻井 井壁稳定 损伤 耦合 有限元 

分 类 号：TE28[石油与天然气工程—油气井工程]