Investigation of sensitivity of shale elastic properties to rock components based on a digital core technology and finite element method

Abstract

Elastic properties of rock are being used to help evaluate reservoir properties. Distinctive properties of shale, such as low porosity and permeability, anisotropy, and complicated mineral components, limit the application of traditional petrophysical experimental method. The elastic properties of shale are not easy to obtain. In this work, we proposed a workflow and used an advanced Markov Chain Monte Carlo (MCMC) method to reconstruct 3D digital cores of rocks in a shale reservoir. Then, we used a finite element method (FEM) to calculate the equivalent static elastic moduli of shale of the 3D digital cores. This method overcomes the limitation of the direct elastic property measurement. The equivalent bulk and shear moduli of cores with different compositions are obtained. The result reveals that the moduli are anisotropic and have different sensitivities to different components. Equivalent moduli linearly decrease in three cases, namely (a) with the increase of clays, (b) with the increase of porosity, and (c) with the increase of organic matter content. On the other hand, equivalent moduli linearly increase in three cases, namely (a) with the increase of plagioclase content, (b) with the increase of calcite content, and (c) with the increase of pyrite content. For different clays, the equivalent moduli of the rocks vary with the elastic moduli of the clay in the form of power functions. Meanwhile, the bulk modulus can be affected by the type of pore fluid and the shear modulus is insensitive.