Abstract:

In the development of water-flooded oil fields entering the high water-cut stage, the remaining oil often accumulates at the top of structural high positions or thick oil layers, areas not effectively covered by the existing well network. Utilizing the intrinsic characteristics of the reservoir to inject CO₂ and form a gas cap drive can effectively improve development outcomes and achieve CO₂ sequestration. However, the suitability of specific reservoirs for gas cap drive development requires further study. This study delves into the effectiveness of CO₂ gas cap drive in high water-cut reservoirs by examining the movement of the oil-gas interface during the gas cap drive process, using both numerical and physical simulations. Key evaluation metrics include enhanced oil recovery rate, oil displacement efficiency, time to reach the critical gas-oil ratio, and gas retention rate. The research assesses how various reservoir characteristics, such as formation dip angle, crude oil density, viscosity, reservoir confinement, permeability, and the strength of water drive, influence the efficiency of CO₂ gas cap drive for both oil displacement and sequestration. Focusing on these main evaluation criteria, the study identifies that the suitability of CO₂ gas cap drive in reservoirs during the high water-cut phase is significantly influenced by factors such as reservoir confinement, formation dip angle, crude oil viscosity, permeability, and reservoir thickness. These findings aim to provide a foundation for broadening the application of CO₂ flooding techniques. crude oil viscosity, reservoir permeability, and thickness, to provide a basis for expanding the application range of CO₂ flooding.

Key words: high water content, CO₂ artificial gas cap, sensitivity factors, dip angle, hydrodynamic strength, gas storage rate