NUMERICAL SIMULATION OF GAS AND WATER FILTRATION IN POROUS MEDIUM MICROMODELS

Abstract

To select and justify effective compositions for limiting water inflow into gas wells, an understanding of the behavior of the multiphase system on the scale of individual pores is necessary. In turn, capillary forces depend on the interfacial tension and wettability of the pore surface. As part of this work, computational microfluidics methods were used using the OpenFOAM platform to analyze the effect of rock wettability on the features of two-phase filtration of water and gas in a T-shaped micromodel of a porous medium, which is a crack connected to an element of a porous matrix. A mathematical model was chosen that allows you to describe the movement of fluid in a fracture by the Navier-Stokes equation, and in elements of a porous matrix by the Darcy equation. A grid of a T-shaped micromodel of a porous medium was generated using a GMSH grid generator. The displacement of water by gas from the fracture and porous matrix was simulated. Multivariable analysis of water displacement by gas for hydrophobic and hydrophilic surface was carried out by varying wetting angles. The dependencies of the residual water of the micromodel on the contact angle and flow modes were conducted. It has been found that at low filtration rates, water enters the fracture from the porous medium, which blocks the direct flow of gas through the fracture. In the case of a hydrophilic surface, the water inflow from the porous matrix is greater than in the case of a hydrophobic surface, since blocking the fracture results in gas filtration through the porous medium and displacement of water therefrom. The proposed approach can be used to rank effective bottomhole treatment agents and select optimal filtration modes to limit water inflow into gas wells.