An Investigation of Gas Recycling in Fractured Gas-Condensate Reservoirs

Abstract

Condensate banking results from a combination of factors including fluid properties, formation flow characteristics, and pressures in the formation and wellbore. The production performance may suffer provided these factors are not understood at the beginning of field development. Determining the fluid properties can be vital in any reservoir, hence it plays a crucial role in gas-condensate reservoirs where condensate/gas ratio is significant in estimates for the sales potential of gas and liquid. Once reservoir fluids enter a wellbore both temperature and pressure conditions may change, where condensate liquid can be produced into the wellbore but liquid can also drop out within the wellbore. If the liquid falls back down the wellbore, the liquid percentage will increase and may eventually restrict the production. Thus, it is very important for robust reservoir management that each and every control and uncertainty parameter is understood not only in theory but also in practice with solid examples as done in this study. A robust commercial optimization and uncertainty software is coupled with a full-physics commercial simulator that models the phenomenon so as to investigate the significance of major parameters on performance of gas-condensate reservoirs under recycling. Control and uncertainty variables have been investigated via several simulation runs in specified ranges to represent real reservoir and performance conditions rather than theoretical assumptions. This study aims to prepare an insight into the mechanism of gas injection process in reducing gas-well productivity losses due to condensate blockage in the near wellbore region. The main goal of this work is to investigate gas recycling into the reservoir to enhance condensate recovery. The results show the influence of each control or uncertainty variable, leading to a better understanding of management of gas-condensate reservoirs under gas recycling. Impact of fractures is significant and the tornado diagrams illustrate the relative significance of each factor. The results and sensitivities are compared and discussed in light of a comprehensive literature review of recycling gas-condensate reservoirs with different process optimization methods. The significance of all major parameters are outlined using tornado charts to serve as a practical example for optimization of relevant future applications.