摘要
以用岩石力学来定量分析应力敏感性的思路作为切入点,利用煤岩的弹塑性本构方程,推导出了地层压力变化与割理宽度变化的关系式以及应力集中与割理宽度变化的关系式。并讨论了它们在欠平衡压力钻井和过平衡压力钻井中的应用情况。并以割理宽度为桥梁,分析了孔隙压力变化和应力集中两者与储层渗透率的关系。最后通过实例,分析了整套理论在实际中的应用情况。得到的结论是:应力集中会导致储层渗透率下降;压力敏感性试验中,渗透率的部分恢复主要是由于裂隙充填物结构破坏引起的,而不是由于煤产生的塑性变化引起的;欠平衡压力钻井会导致渗透率下降;过平衡压力钻井中,若过压值太大,煤层割理宽度会增加,使得井壁稳定性变差。
With the quantitative analysis of stress sensitivity as the cutting point, the relation between the change of formation pressure and cleat width, and the relation stress concentration and cleat width were developed based on plasto-elasticity constitution equation of coal cleat. The application in under-balanced drilling and over balanced drilling were discussed. The relation between formation permeability and pore pressure and stress concentration were analyzed. The application of this theory in field was analyzed using some examples. The conclusions are the formation permeability will decrease with the stress concen- tration. In the pressure sensitivity studies, the partial recovery of the formation permeability is due to the structure damage of the fracture not the plasto change of coal. The formation permeability reduces in the under-balanced drilling. If the pressure difference is over high in over-balanced drilling, the cleat width will increase and cause the wellbore stability to become worse.
出处
《石油钻探技术》
CAS
北大核心
2007年第5期68-71,共4页
Petroleum Drilling Techniques
基金
中国石油集团建设煤层气重点项目"煤层气钻井关键技术研究"(编号:06A20202)部分成果
关键词
煤层
孔隙压力
渗透率
应力分析
井眼稳定
coal bed
pore pressure
permeability
stress analysis
hole stabilization
