Relative permeability curves are crucial parameters for reservoir engineer and reservoir commercial simulator to predict reservoir performance throughout the life of a reservoir, but meet difficulties in laboratory to obtain reliable data under miscible conditions due to the lack of proper testing and formulation methods. Up to now, most relative permeability curves are measured in short core segments by core flooding, which can hardly display miscible flooding features for early gas breakthrough and insufficient contacting time between CO 2 and oil. In addition, the commonly used analytical and semi-analytical data processing methods are not suitable for miscible flooding for ignoring the mechanism of vaporizing and dissolving mechanism. In this study, slim tubes (101 and 1,528 cm in length) and long composite cores (74.46 cm in length) instead of conventional core segments were used to acquire reliable experimental data of CO 2 flooding under miscible or near miscible condition. Then, using improved empirical Corey model which assumes shape defining factor b og is a function of displacement pressure P combined with history-matching method to calculate relative permeability curves under near miscible and miscible conditions. Results indicated core length is another important parameter to simulate miscible flooding other than pressure, temperature and oil composition, and using long composite cores and improved data processing method more reliable data can be obtained compared with conventional measured method. It is found residual oil saturation in short slim tube is 16.25 % higher than that of long slim tube and CO 2 relative permeability is lower in short slim tube/core segment than in long slime tube/long composite cores.
Some of the heavy oil reservoirs show high primary recovery and high flow rate under solution gas drive. The foamy oil theory has been proposed for the anomalous behavior. There have been numerous studies of diffusion-induced growth or collapse of bubbles in a fluid. However, there are some limits about them such as the determination of initial bubbles radius. Pointed to the problem that how to determine the initial bubble radius, this article proposes a new method base on the hydrodynamic equation, and then regards the bubble as a production well with source and sink theory based on the similarity between the bubbles concentration distribution and the pressure distribution of production well. According to the model established, the bubble growth by pressure and time is predicted, that is, how the amount and size of bubbles change during solution-gas drive is presented, which provided the guidance to determine the parameters of foamy oil due to bubbles change, such as foamy oil viscosity, compressibility, permeability, and so on. This model proved to be reasonable and correct by the agreement between the bubble concentration distribution and the pressure distribution during solution-gas drive.
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