Previsão de comportamento de reservatórios de petróleo sob injeção de água: estudo comparativo entre os métodos de declínios temporal, volumétrico e de simulação numérica

Abstract

Water injection is one of the most used secondary recovery methods in oil fields. When injected into the rock formation, the water promotes pressurization of the reservoir and this, combined with the displacement of the oil through it, implies a greater final oil recovery. However, for the produced oil flow rates to remain constant, it is necessary to improve the volumetric sweeping efficiency and displacement efficiency within a scenario of increasing the water-oil ratio. Thus, forecasting the production of fluids is necessary for the selection and implementation of production development projects. The purpose of this study is to compare the results obtained with the application of each of the two production decline methods (rate time and volumetric) in the prediction of the behavior of a real oilfield (Marlim) and a synthetic reservoir and to investigate which one presents the best estimate in comparison with the respective base case - real production data for the real oilfield and numerical simulation for the synthetic reservoir. To carry out this study, methods of extrapolating the oil cut and the oil rate were used, which allow the prediction of future productions and foresee problems related to the capacity of the water treatment facilities produced. A black oil model built using commercial CMG® 2019 reservoir simulation and modeling software package was used to study the synthetic reservoir. In this way, the production data (oil and water rates, oil recoveries, and accumulated production) generated by the numerical simulation of the synthetic reservoir were taken as being the “real” production data to be used in the comparison between the methods for the synthetic reservoir. For the Marlim field, production data obtained through the National Agency of Petroleum, Natural Gas, and Biofuels (ANP) were used. That said, the future behavior of production at the Marlim field and the synthetic reservoir was forecast using methods of rate time and volumetric declines. Finally, a comparative study was carried out to evaluate the performance of each method, based on the forecast generated by the Imex-CMG® 2019 software for the synthetic reservoir, and, for the Marlim field, the real data of production. In the end, the strengths and weaknesses of each decline method proposed in the comparative analysis are shown.