Lattice Boltzman Method Assisting WAG Hysteresis and Trapped Non-Wetting Phase Simulations

The numerical formulation of an oil reservoir is a formidable task that requires the contribution of several areas of expertise, often unrelated, at different scales. Since this is a hierarchical problem, errors introduced in one step will interfere with the next step, increasing inaccuracies. Our objective is to use predictive numerical methods in different simulation scales to study the oil-trapping relationship which is influenced by wettability, flow rate, interfacial tension, and saturation histories during WAG (Water Alternate Gas) process. This complex behavior requires rigorous models to considering the simultaneous flow of all three phases and, in addition, the reversibility of drainage and imbibition scanning curves is removed. The three-phase hysteresis model implemented during numerical reservoir simulation is based on the work of Larsen and Skauge and comparative scenarios were done for parameters that came from the Lattice Boltzmann method and typical values of literature. The Lattice Boltzmann method is used to simulate two-phase flow of water-oil and oil-gas through a porous medium in order to determine capillary pressure and relative permeability curves in a pore network. Molecular simulation of fluid properties (PVT, viscosity and interfacial tension) are performed to ensure the accuracy of the state equations used in the model. In this scale, density x pressure curves and viscosity x pressure curves similar to those obtained in experimental tests of differential liberation (1 to 400 bar) of reservoir fluids were obtained through molecular simulation models. Besides, the effect of the density ratio between the fluids and contact angle on the shape of the capillary pressure and relative permeability curves are investigated in the porous scale. Hysteresis is observed in all studied cases, becoming more apparent with large density differences. The density ratio is found to influence the pressure required to remove fluids from porous media and the volume of residual fluids trapped in it. The results are important for the study of these curves of a reservoir and confirm that the multi-component Lattice Boltzmann method can supply mesoscale information to take effect at the macroscale studies using reservoir simulation software.