Abstract

The use of enhanced oil recovery methods (EOR) is motivated by the characteristics of the Brazilian pre-salt fields, such as heterogeneous reservoirs under high pressure and low temperature, light fluids with a certain amount of CO2. This produced gas cannot be all released to atmosphere in order to prevent the greenhouse effect. So, this work presents the study of a light oil with 8% of CO2, with an Equation of State (EOS) well-adjusted, applied in three different compositional simulation cases: miscible continuous CO2 injection, WAG – CO2 with or without relative permeability hysteresis. As the hysteresis effect can reduce the gas mobility, causing its displacement through areas that were not initially swept, it was included in the WAG modelling. The results were analysed in terms of average reservoir pressure and production parameters. Both WAG processes (with and without hysteresis) resulted in higher oil production than the continuous CO2 injection, attesting that the water injected in WAG reduced the gas mobility. In the results, it was observed that when the reservoir simulation is a tool applied to predict the oil production, the hysteresis phenomenon should be considered to model a WAG injection, once relative permeability changes with the injection fluids alternation.

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