Establishment of Stability Evaluation Criteria for the Oil-Gas Interface during Gas-Cap Gravity Flooding in Oil Reservoirs with Strong Edge-Water Drive.

A three-dimensional (3D) experimental model considering the influence of water energy is established to innovatively analyze oil-gas interface stability, and it is found that a stable gas cap with sufficient driving energy can be formed only under a stable oil and gas interface. So, the bidirectional displacement through the gas cap and edge water can be realized during the late development stage in the strong edge-water drive reservoirs. Results show that the recovery of bidirectional displacement can reach 60%, while the recovery of an unstable interface is basically below 50%.