Simulation studies were performed to evaluate a novel technology, steam-propane injection, for the heavy Hamaca crude oil. The oil has a gravity of 9.3 ϒAPI and a viscosity of 25,000 cp at 50 ϒC. Two types of simulation studies were performed: a simulation study to historymatch laboratory experimental results, and a reservoir simulation study of steam-propane injection in a 5-spot pattern.
A 1D 48 grid-cell model was used to describe the sand mix in the injection cell. A ten pseudo-component oil model for the Hamaca oil was developed based on composition up to C10+. The ten pseudo-component model used gave a satisfactory history match of the experimental results. Components in the C7 – C10 range appear to play a significant role during steam-propane injection and therefore need to be described in greater detail.
The pseudo-component oil model, developed from history-matching the experimental results, was subsequently used in the reservoir model. The reservoir model represented a symmetry volume that is one-eighth of a 10-acre 5-spot pattern. A 9 × 5 × 10 3D Cartesian model was used to describe the symmetry volume, with one axis (x-axis) oriented parallel to the injectorproducer direction. Results of the reservoir simulation study may be summarized as follows. First, oil production acceleration of two months with a propanesteam mass ratio (PSR) of 0.05 was observed compared to pure steam injection. A substantial gain in discounted revenue and savings in steam injection cost would be realized. Second, unlike the experimental results, the oil production rate peak with steam-propane injection (1100 STB/D) is significantly higher than that with pure steam injection (6 9 0 STB/D). Third, oil production acceleration increases with increasing propane content. However, oil recovery at the end of the five-year forecast period increases with PSR up to a PSR of about 0.05 then declines with increasing PSR up to 0.09. More important, oil recovery at the end of the forecast period with PSR of 0.05 is 6.7% OOIP compared to 2.3% OOIP with pure steam injection.
Both experimental and simulation studies indicate that steam-propane injection is a very promising technology. Further research followed by field tests are recommended to better understand and verify the process under actual field conditions
Steam injection is the most widely used thermal EOR method. Steam injection is a very effective method on account of the latent heat of vaporization that can be harnessed from the steam.1,2 When the steam is injected in deep, high permeability, thick formations at a pressure above 1300 psi, and if the production is constrained, large volumes of heavy oil (∼10 ΥAPI) can be upgraded underground up to 25 ΥAPI oil. 3–6
Injection of steam is an efficient method for mobilizing and producing heavy oil or bitumen, due to the large oil viscosity reduction at higher temperatures. However this effectiveness is often lost if steam does not contact large portions of the oil reservoir or if no or limited flow paths exist for the mobilized oil to the producing wells.
