储层岩石的压缩问题

Discussion on the compression of reservoir rock

岩石的应力敏感与岩石的压缩性密切相关。为了搞清岩石的应力敏感程度,深入分析了岩石的压缩问题。岩石孔隙体积的压缩是因为骨架体积的压缩所致,因此孔隙压缩系数与孔隙度和骨架性质有关。因存在系统误差,体积法测量的孔隙压缩系数数值偏高,且存在逻辑反转现象。弹性模量法消除了系统误差,测量结果符合科学逻辑。岩石孔隙、骨架和外观体积的压缩系数定义的压力不同,不能互相替代。孔隙度为0时,孔隙压缩系数为0,骨架压缩系数和外观体积压缩系数皆不为0,且骨架压缩系数等于外观体积压缩系数。岩石的应力敏感指数可由岩石的孔隙压缩系数求出。由于致密岩石的孔隙压缩系数极低,因此,低渗透储层的应力敏感程度极弱,生产过程可将其忽略。

The stress sensitivity of rock is closely related with the compressibility of rock.In order to clarify the stress sensitivity of reservoir rock,compression of reservoir rock was deeply studied.The compression of pore volume of rock is caused by the compression of skeleton of rock.So the compressibility of pore volume is related to the porosity of rock and the property of skeleton.Due to systematic error,the abnormally-high compressibilities are usually measured by the volume method,and the compressibilities measured show the reversal logic.The method of elastic modulus removed the systematic error of measurement,and the measurements conform to the scientific logic.The compressibilities of pore,skeleton and bulk volumes of rock are defined based on different pressures,so they can not be substituted for each other.As porosity is 0,the pore compressibility is also 0,but the compressibilities of skeleton and bulk volume are all not 0,and the skeleton compressibility equals to the bulk compressibility.The stress sensitivity index of rock can be determined from pore compressibility of rock.Due to the low value of pore compressibility of tight rock,the stress sensitivity of low permeability is very weak,and can be neglected in production of reservoir.