Real gas transport in shale matrix with fractal structures

Abstract

A real gas transport model in shale matrix with fractal structures is established to bridge a pore size distribution and multiple transport mechanisms. This model is well validated with experiments. Results indicate that different pore size distributions lead to various transport efficiencies of shale matrix. A larger fractal dimension of the pore size and a smaller minimum pore size yield higher frequency of occurrence of small pores and a lower free gas transport ratio, which further results in lower transport efficiency. Gas transport efficiency due to pore size distribution parameters (a fractal dimension and a minimum pore size) varies with different porosities and pressures. Increasing fractal dimension and decreasing minimum pore size result in a higher contribution of Knudsen diffusion to the total gas transport. Decreased pressure and increased porosity enhance the sensitivity of gas transport efficiency to a pore size distribution. The relationship between apparent permeability and porosity based on different pore size distributions is also established for industrial application.