رضا آذین

Gas-assisted gravity drainage (GAGD) is known as an important enhanced oil recovery (EOR) method. Detailed understanding of multiphase fluid flow mechanisms in fractured porous media is one of the challenging issues in reservoir engineering. In this paper, the most effective parameters on the GAGD recovery factor (RF) in fractured porous media are investigated using a new experimental fractured sand pack. The Taguchi method as an effective approach for design of experiments and optimization of design parameters is employed to evaluate impacts of various process variables such as sand particle size, type of wetting and non-wetting phases, gas injection rate, dip angle, and fracture position on oil RF under gravity drainage mechanism. During the experiments, distilled water and condensate are utilized as the wetting-phase. Nitrogen and carbon dioxide are also used as the non-wetting phase. Moreover, an analysis of variance (ANOVA) is conducted to find the most significant parameters affecting GAGD recovery factor. Also, the process variables are optimized to maximize oil RF. The results reveal that the type of wetting phase is the most effective parameter in the GAGD processes. The mean sand size and fracture position are the second and third influencing parameters followed by the injection rate, dip angle, and type of non-wetting phase. The optimum conditions for maximizing RF of the GAGD are identified in the following order: wetting phase of condensate, mean sand size of 300 μm, non-wetting phase of N2, fractures at the number of 3, dip angle equal to 0o (vertical model), and injection rate of 20 cm3/min. According to this research, the average recovery factor of condensate as a wetting phase is found to be around 12% higher than the water case. Also, N2 as an immiscible injected gas causes a higher average recovery factor compared to CO2. Increasing the mean sand size, injection rate, or the number of fractures can enhance the GAGD RF. The dip angle experiments de