Equation of state model development and compositional simulation of enhanced oil recovery using gas injection for the West Sak heavy oil

Abstract

West Sak oil field, with its very huge reserves of heavy oil, has the potential of supplementing the declining light oil production on the Alaska North Slope. Due to the heavy nature of oil, its phase behavior is very complex. A proper understanding of the phase behavioral changes of the West Sak oil is crucial to design any enhanced oil recovery scheme. Such Enhanced Oil Recovery (EOR) techniques are essential in the absence of natural drive mechanisms in these reservoirs. For the proper selection of any EOR technique, reservoir simulation studies should prove its viability. Accordingly, a complete phase behavior analysis of the West Sak crude oil was carried out. All the available experimental data was scrutinized and a model equation of state was developed that should describe the phase behavior of West Sak oil. After having done that, reservoir simulation was carried out to study the implications of employing gas injection as an EOR technique for the West Sak reservoir. It was found that a definite increase in heavy oil production can be obtained with proper selection of injectant gas and optimized reservoir operating parameters. A comparative analysis is provided which should help in making such a decision.