Modeling Condensate Banking Mitigation by Enhanced Gas Recovery Methods

Condensate banking in natural gas reservoirs can hinder the productivity of production wells dramatically due to the multiphase flow behaviour around the wellbore. This phenomenon takes place when the reservoir pressure drops below the dew point pressure. In this work, we model this occurrence and investigate how the injection of CO₂ can enhance the well productivity using novel discretization and linearization schemes such as mimetic finite difference and operator-based linearization from an in-house built compositional reservoir simulator. The injection of CO₂ as an enhanced recovery technique is chosen to assess its value as a potential remedy to reduce carbon emissions associated with natural gas production. Two test cases were modeled, a base cylindrical case with one producer and injector (test case #1) and test case #2 a full field model with multiple producers and injectors, with each case having two scenarios. In both cases we first model a base scenario with only producers where we show the deposition of condensate banking around the well and the decline of pressure and production with time. In another scenario we inject CO₂ into the reservoir as an enhanced gas recovery mechanism. In both cases, we use fully tensor permeability and unstructured grids using the multi point flux approximation (MPFA) and the mimetic finite difference (MFD) methods. The results of the simulation show that in the producers only scenarios the gas and condensate production rates drop after a certain production plateau, specifically the drop in the condensate rate by 25 to 46%. The introduction of a CO₂ injectors yield a positive impact on the productivity and pressure decline of the well. It enhances the productivity index by ~ 35 - 60% on all cases and the overall recovery of condensate by 8 – 12%. Further improvements are seen in the pressure profile in terms of reservoir pressure, bottom hole pressure and reservoir drawdown by a maximum of 19.6% in the cylindrical test case #1 and up to 58% in the Full Field Model.