摘要
在煤层气井排采过程中,为了揭示剪切破坏产生煤粉的机理,基于弹性力学理论构建了诱导应力场的计算模型。基于剪切破坏准则,提出了煤岩失稳的判断方法。研究结果表明:地层压力越小,孔弹效应产生的诱导应力越大;地层压力低于临界解吸压力后,煤岩发生收缩形变,产生诱导应力。地层压力下降形成的诱导应力等于煤基质收缩的诱导应力与孔弹效应的诱导应力之和,随着地层压力降低,煤层剪切失稳的可能性上升,是形成煤粉的重要因素。
To demonstrate if coal fines can be induced by shear failure during desorption process,elasticity mechanics theory was used to construe the altered stresses in the formation far away from the hydraulic fracture. The possibility of shear failure was also calculated from the failure envelope. When lowering formation pressure,Poro-elasticity is appropriate for predicting changes of stresses due to small changes of strain. Meanwhile,desorption-induced shrinkage also explain the extra stress. Desorption can lead to a decrease of effective horizontal stress and large changes of deviatoric stress that can take the coal to shear failure,which leads to rock fragmentation and fines production that can plug conductive fractures.
出处
《钻采工艺》
北大核心
2017年第6期66-69,共4页
Drilling & Production Technology
基金
十三五国家重大专项"大型油气田及煤层气开发"(编号:2016ZX05066003-003)资助
关键词
煤层气
地层压力
诱导应力
剪切失稳
coal bed methane
formation pressure
induced stress
shear failure
