低渗透储层存在强应力敏感吗?——回应窦宏恩先生

Are low permeability reservoir rocks strongly stress sensitive?——Reply to Mr Dou Hong-en

低渗透储层属于致密介质,孔隙度小,压缩系数低,应力敏感性也极其微弱。但是,Hall图版曲线却显示了错误的逻辑关系,即孔隙度越低,岩石的压缩性越强。Hall图版的逻辑错误,是由实验中的表皮效应所致。根据弹性模量法测量的岩石压缩系数显示了正确的逻辑关系,即孔隙度越高,压缩系数越大,且压缩系数的数值非常低,低于地层流体的压缩系数。岩石的应力敏感与岩石的压缩性存在密切的关系,低渗透储层的压缩性低,应力敏感必然很弱。低渗透储层的强应力敏感现象,是由实验的系统误差所导致的,而非岩石自身的性质。

Low permeability reservoir rocks are tight media, which porosity, compressibility and stress sensitivity are all quite low. However the Hall＇s plot shows a wrong logic relationship of rock compressibility with porosity, which is that lower porosity rocks are more compressible. The wrong logic of Hall＇s plot is resulted by the skin effect of core analysis. The compressibility data by the elastic modulus method display a correct relationship, which is that higher porosity rocks are more compressible, and also the rock com- pressibility is lower than that of reservoir fluids. The stress sensitivity of rock is strongly related to its compressibility. Due to the low compressibility of low permeability （porosity） rocks, the stress sensitivity of low permeability （porosity） rocks must be quite weak. The strong stress sensitivity of low permeability （porosity） rocks is resulted by the systematical error in core analysis, and is not the property of rocks themselves.