Feasibility study of enhanced foamy oil recovery of the Orinoco Belt using natural gas

Foamy oil behavior contributes significantly to the anomalously high primary recovery of heavy oils observed in the Orinoco Belt, Venezuela. However, once below the pseudo-bubble pressure, disappearance of this phenomenon results in a rapid increase in the produced GOR and a fast decline in oil production. This paper presents the results of a laboratory investigation, including asphaltene precipitation studies, pressure-volume-temperature (PVT) studies of foamy oil-natural gas mixtures and coreflood tests, for evaluating the feasibility of the natural gas injection process for enhanced heavy oil recovery with foamy oil characteristics. Firstly, asphaltene precipitation tests were carried out to investigate the likelihood of asphaltene deposition problems in MPE3 reservoir during the gas injection process. The natural gas dissolution tests characterized the natural gas diffusion process in the foamy oil, and a new method for determining the natural gas diffusion coefficient in foamy oil was developed on the basis of experimental data. Thereafter, foamy oil swelling tests examined the effects on viscosity reduction and foamy oil swelling of the presence of natural gas. Finally, coreflood tests were carried out to investigate the effects on oil recovery of injection mode and their different process parameters. The results indicate that significant amounts of natural gas could dissolve in the oil, which would cause oil swelling, viscosity reduction and artificial foamy oil formation. Core-flooding tests show that the natural gas huff-n-puff process could increase oil recovery 7.8% compared to the primary pressure depletion process, indicating a greater potential for recovering heavy oil. However, the asphaltene instability could potentially nullify any expected benefits of improved oil recovery with natural gas.