Simulation study of enhanced condensate recovery by gas injection in gas condensate reservoirs with natural water influx from lab to field

The depletion of water-driven gas condensate reservoirs is frequently accompanied by active aquifer water intrusion, which contributes to the loss of gas well productivity and the reduction in condensate recovery. Based on laboratory experiments and numerical simulations, this study aims to establish a framework from lab to field for investigating displacement mechanism and the potential to enhance condensate oil recovery in water-driven gas condensate reservoir through the gas injection. First, the phase behavior and fluid properties of condensate oil mixed with various injected gases including carbon dioxide (CO2), nitrogen (N2), and cyclic-injected gas were elucidated by incorporating pressure/volume/temperature (PVT) tube experiment and tuned state of equations (EOS). Then, the mechanisms of gas injection recovery were examined by conducting the long-core flooding experiment and numerical compositional simulation. Finally, a field case involving a waterflooded gas condensate reservoir was presented to demonstrate the feasibility of gas injection on increasing condensate recovery factor. The results show that: 1) the injection of CO2 has the best ability of dissolution enhancement, retrograde evaporation mitigation, interfacial tension reduction, and viscosity reduction of condensate oil; conversely, injecting N2 or cyclic-injection gas yields only minor difference. 2) In comparison with CO2 injection, injection of N2 and cyclic-injected gas exhibits a more pronounced effect in providing pressure support and retarding the influx of the aquifer. 3) The presence of heterogeneity accelerates the breakthrough of injected gas; additionally, the aquifer intrusion renders a volume of trapped gas immobile. Consequently, compared with the primary depletion scenario, gas injection has limited potential for recovering an additional 2%–4% of condensate oil. It is observed that when the condensate oil is dispersed throughout the formation that is highly waterflooded due to natural water influx, enhancing condensate recovery through gas injection becomes challenging.