Prediction of three-phase saturation profiles from two-phase capillary pressure curves as a function of wettability

Gravity drainage of oil with gas is an efficient recovery method in strongly water-wet reservoirs and yields very low residual oil saturations. However, many of the oil-producing reservoirs are not strongly water-wet. Thus, predicting the profiles and ultimate recovery for mixed and oil-wet media is essential to design and optimisation of improved recovery methods based on three-phase gravity drainage. In this study, we perform two- and three-phase gravity drainage experiments in sand-packed columns with varying wettability. We propose a simple method for predicting the three-phase equilibrium saturation profiles as a function of wettability. In each case, the three-phase results were compared to the predictions from two-phase results of the same wettability. We find that the gas/oil and oil/water transition levels can be predicted from pressure continuity arguments and the two-phase data. The predictions of three-phase saturations work well for the water-wet media, but become progressively worse with increasing oil-wet fraction.[Received: April 12, 2011; Accepted: September 19, 2011]