CO2 Enhanced Gas Recovery and Geologic Sequestration in Condensate Reservoir: A Simulation Study of the Effects of Injection Pressure on Condensate Recovery from Reservoir and CO2 Storage Efficiency
Hydrocarbon recovery efficiency can be increased by injecting miscible CO2 gas in order to displace hydrocarbons towards producing wells. This process of enhanced oil recovery can simultaneously and subsequently be used for CO2 storage after complete hydrocarbon reservoir depletion. Condensate reservoirs provide possible storage sites, with the additional benefit of enhanced gas recovery through re-pressurization of the reservoir and re-vaporization of the condensate. However a lot more research needs to be done. In order to accurately determine the effect of the injected CO2, the compositional simulator CMG- GEM was used. The aim of this paper was to examine the effect of CO2 injection pressures on condensate recovery and CO2 storage. We used a tuned Peng and Robinson equation of state to model the interactions of the CO2 with the hydrocarbons.
It was observed that the injection of CO2 had a positive effect on the re-vaporization of condensate dropout in the reservoir. Increasing the injection pressure yielded higher condensate recoveries up to a certain value (as high as 16%). At this point, the producer experienced liquid loading issues. Additionally, more than 90% of the injected CO2 remained in the reservoir for this specific model. A large percentage of this trapped CO2 remained in the supercritical phase. Increasing the injection pressure increased the percentage of CO2 trapped in the reservoir by hysteresis (as high as 30%). This increased injection pressure had negligible effects on the CO2 dissolved in the formation water.
The results from these simulation studies show that the use of CO2 to increase condensate recovery from the reservoir is feasible with the additional benefit of CO2 sequestration.