Improved saturation-pressure relationship and multiphase pseudo-pressure calculations for retrograde gas reservoir production under boundary-dominated flow

Abstract

For reservoirs containing fluids with complex flow characteristics, the calculation of multiphase pseudo-pressure plays a significant role in production data analysis (PDA) practices. In the case of retrograde gas reservoirs/gas condensate reservoirs under multiphase flow conditions, the lack of a reliable and complete saturation-pressure (So-p) relationship presents a significant challenge in obtaining the appropriate value of multiphase pseudo-pressure. Gas condensate reservoirs are one of the viable and lower-emission hydrocarbon sources for meeting the ever-increasing global energy demand. The economic value of producing gas condensates has inspired numerous research into employing innovative production techniques in developing gas condensate fields. Hence, this study proposes an improved saturation-pressure relationship alongside a Fractional Phase Mobility (FPM) criterion to mitigate potential errors in the multiphase pseudo-pressure calculation for gas condensate reservoirs under boundary-dominated flow. This work introduces an improved So-p relationship derived using a Rescaled Constant Volume Depletion (CVD) method for estimating multiphase pseudo-pressures. To demonstrate the effectiveness of the proposed approach, we provide direct comparisons with the Classical CVD method and numerical simulation results for multiple gas condensate cases subjected to constant and variable bottomhole pressure (BHP) schedules. In contrast to the classical approach, the Rescaled CVD method consistently delivers superior performance for multiphase pseudo-pressure estimations across all cases, thus supporting its potential as a robust and accurate approach for gas condensate reservoir modeling.