Numerical simulation study on gas miscibility of an oil field located in Afghanistan

In this study, a reservoir modeling approach was used to evaluate the miscibility conditions for an Afghan oil reservoir. A model of slim-tube apparatus was built for compositional simulation in CMG-GEM. Minimum miscibility pressure/enrichment (MMP/MME) of crude oil-gas (carbon dioxide, methane and nitrogen) systems were determined by slim-tube simulation. To study the reservoir performance under each injection gas process, we built a quarter of five spot pattern model. The model was assumed to represent a homogeneous section of the reservoir. Simulation results of slim-tube test suggest that, to be miscible with reservoir oil, carbon dioxide requires less addition of enriched gas comparing to nitrogen or methane. But, the reservoir section model showed that a miscible nitrogen injection is better, with higher oil recovery factor than that of miscible carbon dioxide or methane.