Multiscale fractal-power-law model for shale extraction with water reflux case

Abstract

After the shale reservoir is hydraulically fractured, the shale gas is transported to the horizontal well through various media. Hydraulic fracturing produces hydraulic fractures and generates secondary fractures. The hydraulic fractures and fracture induction areas are filled with gas and water phases. In this work, using power-law fracture distribution and porous media fractal theory, as well as accounting for seepage mechanisms in both the water and gas phases, a shale multi-scale mining model is constructed. The results of the study demonstrated that: (1) The degree of hydraulic fracturing is determined by a number of factors. An appropriate degree of hydraulic fracturing is more conducive to improving gas production. There is a competitive relationship between shale gas seepage and water reflux. Either above or below the moderate interval may lead to excessive water reflux and affect gas production. (2) Various properties of the water phase also influence the production results and pore structure evolution. A moderate maximum relative permeability of water and non-wetting phase entry pressure can contribute to a good pore structure progression and a more desirable gas production. (3) The contribution of hydraulic fracturing porosity to pore structure evolution is greater than the initial relative permeability of water and non-wetting phase entry pressure.