Study on the Flow Properties in Carbonate Reservoirs with a Cavern Drilled into Based on the Flow Field and Seepage Field Coupled Model

Well understanding of fluid flow properties in reservoirs is a prerequisite for efficient development of oil reservoirs. However, the information of fluid flow properties in fractured-cavern carbonate reservoirs is few, primarily because there exists seepage in stroma and free flow in cavern. fluid flow properties in carbonate reservoirs with a single cavern drilled into were studied based on the flow field and seepage field coupled model in which the Navier-Stokes equation (N-S equation) and the Darcy´s law were set as the governing equation of oil flow in cavern and stroma respectively, and the Brinkman equation was set in padded zone of cavern and the transition zone between stroma and cavern. Simulation results found just a small change in pressure in the cavern except the place very nearby the bottom of well. Pressure in the unpadded cavern and the half-padded cavern was almost the same and equaled the bottom-hole pressure, while the pressure in padded cavern was 2 MPa higher than others. These results indicate that pressure in unpadded or half-padded cavern falls quickly to the bottom-hole pressure across the cavern at the initial stage of reservoirs development, and cavern can be treated as a constant pressure body at the middle and later stage to simplify engineering calculation.