Modified cell-to-cell method for slim tube test simulation considering the porous media effect

Miscible gas injection into oil reservoirs is one of the most effective methods to enhance oil recovery. In this process, the minimum miscibility pressure (MMP), which is the minimum pressure at which the two phases of oil and gas are completely miscible together, is the key parameter in the gas injection operation. Various laboratory and calculation methods were used to determine the MMP. The slim tube displacement test is the most reliable in the oil industry among the laboratory methods. Among the calculation methods, cell-to-cell simulation is currently the most efficient method for MMP approximation, because of its high calculation speed and simplicity. In this study, laboratory studies and modeling were conducted to estimate the MMP between an injected hydrocarbon gas and a live oil sample. The slim tube displacement test was completed. In addition to laboratory studies, cell-to-cell simulation (CCS) has been used for slim tube simulation. Modifications have been made to the cell-to-cell simulation by applying corrections, including the Peng-Robinson equation of state adjustment for a porous medium, improvement to the critical properties shift equation, the incorporation of capillary pressure effects in the vapor-liquid equilibrium (VLE) calculations, and changes to the fluid transfer criteria within the cell-to-cell method. The permeability-to-porosity ratio is used to account the effect of the porous medium on phase behavior. The results of investigating the effect of the porous medium on the MMP indicate that a reduction in the permeability-to-porosity ratio leads to a decrease in the MMP. This phenomenon is particularly pronounced in tight oil reservoirs with permeability-to-porosity ratios lower than 10, meaning that miscibility can be achieved more easily in these reservoirs compared to conventional ones.