Speaker
Description
As a significant component of unconventional oil and gas resources, fractured-vuggy reservoirs are characterized by the complex connectivity between fractures and cavities, as well as strong heterogeneity. These factors lead to elusive flow patterns and intricate mechanisms of residual oil formation during reservoir development. Using custom-designed artificial fractured-vuggy cores, this study revealed the influences of fracture occurrence, drainage pressure, and cavity filling on flow patterns during water and gas injection. Moreover, fluid distributions within fractures and cavities were systematically analyzed through visualization experiments, and variations of displacement efficiency were quantitatively described. Experimental results demonstrate that vertical fractures connected to cavities tend to form more residual oil, and gravitational differentiation decreases sweep range in fractures during water and gas injections, while horizontal fractures significantly enhance displacement efficiency. Although drainage pressure has no effect on displacement efficiency, and single-phase flow is observed during low-pressure displacement, oil-gas two-phase flow occurs during gas injection under high pressure. Furthermore, the efficiency of water displacement is notably higher than that of gas injection. The presence of a cavity filled with particles decreases water displacement efficiency due to the formation of complex flow paths and two-phase flow. Visualization experiments further demonstrate that wider fracture apertures, larger cavity diameters, and higher injection velocities hinder the accumulation of the displacement front in the vertical direction. However, the displacement efficiencies in fractures and cavities increase significantly with higher oil viscosity.
| Country | China |
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