Modelling the surface effect of multi-wet pores in reservoirs rocks

Modelling multiphase flow in source rocks (e.g. gas shale and coal-bed seams) has been a challenge due to their complex structures of tight pores and heterogeneous matrix mineral compositions, which give rise to complex flow behaviours. Since pores are rarely confined by sediments with a ‘uniform’ surface wettability, even for those formed within organic matters due to hydrocarbon generation, there is a need to understand the effect of multi-wet pores on the multiphase fluid dynamics, and the impact on the prediction of macroscopic flow properties when simpler assumptions on the surface wettability are made. Moreover, conventional models of relative permeability cannot be applied to unconventional rocks without considering multi-wettability characteristics. This work uses a Rothman and Keller (RK) multiphase Lattice-Boltzmann model to study the effect of dual-wettability on gas-water flow in pores bounded by organic and inorganic minerals. Simulations were run to comprehend the physics of these processes at different saturation profiles at low capillary numbers. Results show the phase mobility and configurations are affected by different mineral configurations at submicron pores and the characteristics of phase displacements that suggest what pore filling mechanisms should be included when the effect of the dual-wettability is important.