Evaluation of Steam-Foam Flooding in Multi-Layered Heterogeneous Reservoir

Abstract

Steamflooding, one of the Enhance Oil Recovery (EOR) techniques to perform with heavy oil, provides physical displacement, helps maintain reservoir pressure and delivers heat to oil, resulting in decreasing of oil viscosity and oil is readily to flow. However, steam tends to override the reservoir due to its lighter density compared to oil, leaving bottom part of reservoir non-displaced and therefore, causing poor vertical sweep efficiency. Steam-foam enhances flow properties of steam by creating higher viscosity displacing material, resulting in better sweeping. This study attempts to analyze effects of operational parameters and reservoir heterogeneity. A base case model is constructed as homogeneous model. Operating parameters including foam stability, foam quality, steam quality and steam injection rate are identified. Later, selected operating parameters are performed in various heterogeneity values quantified by Lorenz coefficient to observe effects of reservoir heterogeneity. Simulation results indicate that steam-foam flooding with appropriate adjustment of operating parameters yields beneficial results compared to conventional steamflooding due to enhanced vertical sweeping front. In terms of operating parameters, optimum range of foam half-life which is an indicator for foam stability is suggested to be in between 0.25 and 1 day to avoid low fluid injectivity in foam with high stability and steam overriding in foam with low stability. In case of high foam quality, steam can be injected easily. Condensing steam tends to move downward and leaves certain amount of oil in shallow zone. Whereas low foam quality with higher portion of surfactant solution behaves closer to water and moves slower, leading to low injectivity of the injector. Optimum foam quality is found to be around 0.90. Different steam quality values do not significantly affect oil production but higher steam quality requires more energy to achieve latent heat of steam. Higher steam injection rate yields higher oil recovery which is desirable. However, water also breakthrough earlier, leading to high water-cut in earlier stage of production. In terms of reservoir heterogeneity, fining upward reservoir provides better results than coarsening upward reservoir because low permeability layers on top of reservoir can mitigate steam overriding, leading to better vertical sweeping profile. Moreover, different heterogeneous degree in typical range of Lorenz coefficient values from 0.20 to 0.30 does not provide significantly different results.