Effect of Gas Recycling on the Enhancement of Condensate Recovery in an Iranian Fractured Gas/Condensate Reservoir

Abstract

Abstract Gas condensate reservoirs have complicated fluid flow and thermodynamic processes. The reservoir temperature of these systems lies between the critical point and cricondentherm. As reservoir pressure decreased, the gas condensate system exhibits a dew point. As pressure is reduced, liquid condenses from the gas to form free liquid in the reservoir. The condensate is deposited at such low liquid saturation that is usually trapped by surface tension forces, is therefore immobile, and cannot be produced. Condensate liquid builds up near wellbore causing a reduction in gas permeability and gas productivity. The injection of dry gas into a retrograde gas condensate reservoir helps in vaporizing the condensate and increases its dew point. This study prepared 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 the lean gas recycling into the reservoir to enhance condensate recovery and to prevent permeability reduction. In this work, these subjects were studied: fluid phase diagram changes in gas condensate reservoir, initial gas in place and prediction of the amount of condensate, recovery factor evaluation at different scenarios (Natural depletion and gas injection), implementation of gas recycling to enhance recovery and comparison of this method with CO2, N2 and methane injection. This research was done on a retrograde gas condensate reservoir through compositional simulator. Five possible scenarios: natural depletion, gas recycling, methane, CO2 and N2 injection, were compared. In each scenario, changes in reservoir fluid composition after injection were investigated. Results indicated that CO2 injection yields better recovery that others and methane injection has the least recovery.