Abstract

Eastern Llanos in Colombia is a heavy oil prolific basin. Reservoirs in this area generally exhibit water intrusion and extensive transition zones which its origin is probably explained by a combination of lithology variation and a week density contrast in between the reservoir water and oil. If oil viscosity at reservoir temperature is low enough to allow primary production; it is feasible to develop heavy oil fields using horizontal wells and high volume lift pumps. However, operators have to prepare to treat and dispose large volumes of produced water. Other reservoirs with higher oil viscosity require an enhance oil recovery (EOR) processes to pursuit a commercial development. Among the recovery methods applied to heavy oil reservoirs, the most popular is steam injection in its different schemes. Nevertheless, in high initial water saturation environments the thermal efficiency of the steam is under concern. Other EOR options include but not limited to: polymer injection, Alkaline Surfactant and Polymer “ASP”, “In situ Combustion”, Single Well SAGD, SAGD, VAPEX, Solvent Injections and Steam Solvent Hybrid Processes. In hybrid processes an amount of solvent is added to the steam. It is thought that the efficiency of the thermal recovery can be improved by such solvent fraction. It is expected that the presence of solvent helps reducing the cumulative Steam to Oil Ratio (SOR), therefore the overall economic of the recovery project. The amount and kind of solvent are important factors to investigate for any particular reservoir. The production potential under steam hybrid process has been studied in this work with focus on heavy and extra heavy oil reservoirs exhibiting high initial water saturation in llanos basin.

It has been found that this process looks very promising to overcome the difficult task of producing very viscous oils in presence of mobile water. Numerical evaluations and laboratory displacement test conducted with reservoir fluids and rocks gathered from llanos basin heavy oil reservoirs; have shown a clear improvement on displacement efficiency in hybrid steam-solvent injection with regard to pure steam injection.

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