Análise do processo de injeção contínua de CO2 ou água em reservatórios com características do pré-sal

Abstract

Pre-salt is the world’s greatest oil-related finding of the past 50 years. Pre-salt oil lies in ultra-deeps reservoirs, under an extensive and thick salt layer, along the coast from the states of Espírito Santo to Santa Catarina. These reserves have large volumes of light oil (between 28 to 30 API), large gas volume and high CO2 content (8% - 12%). The exploitation of these reserves also presents great challenges due to the high depths, distance of the coast, the behaviour of salt, among others. In this context, this research aimed to analyse two important methods of oil recovery: water and CO2 injection. From the modelling of a light fluid and a reservoir with characteristics similar to the Brazilian pre-salt, different injection models were simulated through GEM (“Generalized Equation-of-State Model Compositional Reservoir”) from CMG (“Computer Modelling Group”), changing operational parameters such as injection flow, well configuration and injection times. Initially, the isolated injection of water and CO2, and then the injection process of water and CO2, alternatively, were analysed. When the separated injection of these fluids was analysed, the CO2 injection process showed be less efficient than the water injection, but provided an anticipation of the production. The results showed that the use of recovery methods increased the oil recovery factor compared to the primary recovery, around 62% in the best studied case. The continuous injection of water followed by CO2 showed better results when compared to the injection of these fluids separately, increasing the oil recovery factor by approximately 8% compared to only the injection of water.