Numerical Simulation Study for Analyzing the Factors Affecting Microbial Enhanced Oil Recovery
Primary and secondary recovery methods are usually not sufficient to maximize the oil recovery. In many cases, more than 40% of the Oil Initially in Place (OIIP) is left in the reservoir after implementing these recovery methods. To resolve the issue at hand, petroleum engineers have at their disposition a plethora of tertiary recovery methods such as chemical flooding, thermal recovery, and microbial enhanced oil recovery (MEOR). In this study, we propose the use of MEOR: a technique that uses naturally occurring microbes in the reservoir or injected microbes to enhance the oil recovery. This approach is particularly attractive because it is inexpensive and most importantly environmentally friendly. The MEOR process is governed by several mechanisms such as viscosity reduction, wettability alteration, interfacial tension reduction, and other reaction-induced system changes such as pressurization. This study investigates the impact of these mechanisms on the hydrocarbon production by conducting a numerical simulation using the in-house MEOR numerical simulator which is developed from the seed code of TOUGH+ and TOUGH2 family of codes. We conduct a sensitivity analysis to evaluate the impact of factors affecting MEOR to the system responses and production behavior. We investigate the factors as follows: changing relative permeability of oil and water affected by MEOR (to analyze the impact of wettability alteration), changing capillary pressure between oil and water affected by MEOR (to analyze the impact of interfacial tension alteration), and microbial reaction parameters such as yield coefficient of microbes (Y), maximum microbial growth rate (µmax), maximum temperature for microbial growth (Tmax), and microbial death rate (δ) (to analyze the impact of reaction-induced system changes). The system responses include the pressure, temperature, oil viscosity, phase saturations, production rates, and cumulative productions of fluid phases. The simulation results can provide the relative impacts of factors affecting the performance of MEOR, which subsequently can suggest the most important factors to be investigated to reliably predict the improvement of oil production through MEOR. Unlike other MEOR simulator, our in-house simulator models the impact of microbial parameters on fluid production.