An in-situ combustion simulator for enhanced oil recovery
A multi-dimensional three phase flow simulator is written to simulate the process of in-situ combustion. It has six components (oxygen, inert gas, a light oil, a heavy oil, water, and coke). The inert gas consists of all the noncondensible gases other than oxygen. The vaporization and condensation of both water and oil is governed by vapour-liquid equilibria, using temperature and pressure dependent equilibrium coefficients. Splitting of the oil into fractions is done to include the distillation effect. The model includes four chemical reactions. These represent in turn the formation of coke from the heavy oil, the oxidation of the coke, and the oxidation of the light and the heavy oil. Heat transport is assumed to take place by convection and conduction. The effects of gravity, capillary pressure between any two fluid phases, and heat losses to the surrounding rock via conduction are also included. The model is validated using the ISCOM simulator. This has been carried out by comparing the results from the present simulator with these from similar calculations performed using the ISCOM simulator. ISCOM is a fully implicit multi-dimensional finite difference general thermal simulator developed by the computing modelling group (CMG) at Calgary. This comparison is needed in order to establish confidence In the predictive capability of the present model for a particular reservoir. In addition, a comprehensive study of the effect of the main input parameters on the performance characteristics of the in-situ combustion process is carried out. This study is made in order to indicate which data are "important" in the sense of having a significant influence on the performance characteristics of the process and to test the robustness of the program to changes in the input parameters.