基于岩石物理的致密气层识别方法研究

Tight gas reservoir recognition method based on the rock physics model

致密储层声波性质受骨架矿物组成及孔隙类型影响较大,为更准确进行气层识别,本文给出了一种综合模型,和利用纵横波速度信息进行致密气层识别的方法:其首先利用Voigt-Reuss-Hill平均模型,求取岩石骨架等效弹性模量,消除岩性影响;根据综合模型和岩石剪切模量计算孔L隙纵横比(或裂隙密度),消除孔隙性质影响;利用DEM和K-T模型计算干燥岩石弹性模量,得到不受孔隙流体性质影响的弹性模量;将实测岩石弹性模量减去干燥岩石弹性模量定义为含气性因子;同时利用最小二乘法和体积模量,进行气层识别。本文含气分析方法考虑因素全面,干燥岩石纵横波速度比非定值,为具有复杂岩性和低孔低渗等特征的致密岩石气层识别提供技术支持。

Taking into consideration the effect of lithology and porosity, a tight gas reservoir recognition method using both compressional and shear wave velocities is presented. First, the Voigt-Reuss-Hill model is used to calculate the equivalent elastic modulus in order to eliminate the effect of lithology. Second, the DEM and K-T model is taken to get aspect ratio of pore （or crack density）. Then, the elastic modulus of dry rock which is not affected by pore fluid is obtained. At last, a gas reservoir recognition factor which is defined by the difference between the actual elastic modulus and dry rock elastic modulus is computed, and the gas saturation is obtained. The new method is complete and suitable for the tight gas reservoir whose porosity, permeability, and lithology are complex. The example of its application shows the validitv of this method.