Mechanisms of Additional Flow Resistance Induced by Gas Bubbles during the Crude Oil Degassing Process in Fractured-Porous Carbonate Reservoirs

Carbonate reservoirs have emerged as key targets for hydrocarbon development owing to their substantial reserves and widespread distribution. During depressurization, gas bubbles form as the reservoir pressure declines below the saturation threshold. The emergence of a gas phase introduces additional flow resistance, further hindering reservoir development. This study thoroughly investigates the mechanisms of additional flow resistance induced by gas bubbles during crude oil degassing, using a combination of experimental and theoretical approaches. Experimental results reveal that gas bubble accumulation in narrow pores can obstruct flow paths, significantly increasing resistance and diminishing oil mobility. Microscopic visualization experiments further confirm the presence of gas bubbles in various pore structures, where they form a discontinuous phase in smaller pores. This process not only exacerbates reservoir heterogeneity but also impedes the efficient development of carbonate systems. Moreover, the impact of gas bubbles on water flooding has been quantitatively assessed through a numerical simulation approach. Simulation results indicate that with increased degassing, fracture relative conductivity is enhanced, leading the water phase to preferentially flow through fractures rather than the matrix. Incorporating degassing-induced resistance leads to earlier water breakthrough and exacerbates water channeling phenomena. Additionally, cumulative oil production declines as gas bubble-induced resistance increases, further validating the influence of degassing on reservoir dynamics. This study offers both theoretical foundations and practical insights for improving recovery in carbonate reservoirs, proposing innovative strategies for more efficient development.