Experimental Investigation of Foamy Oil Flow in Solution Gas-Drive

Foamy oil flow occurs in primary depletion of heavy oil reservoirs as has been demonstrated in many laboratory experiments. It is thought to be an important recovery mechanism in several heavy oil reservoirs in Canada and Venezuela, which have shown higher recovery factors compared to what is expected from the normal solution gas drive (Darcy's Law). This work investigates the effects of several process parameters on oil production rate and recovery factor in foamy solution gas drive.;Primary depletion experiments were carried out in a 2 meters long sand-pack starting from irreducible water saturation and maximum oil saturation. The results showed that the solution gas drive recovery factor, in heavy oil systems, depends strongly on the pressure drawdown (as the driving force for the oil production) that develops in the system as a result of pressure reduction or fluid withdrawal at the production port. It was also found that the foamy solution gas drive performance is negatively affected by increased solution gas-oil-ratio. The methane saturated oil, which had the lowest solution GOR, provided the highest recovery factor, while ethane saturated oil (which had the highest solution GOR) provided the lowest recovery. The results also showed that the oil recovery factor did not decrease significantly when the saturation pressure was decreased from 3,500 kPa to 2,100 kPa.;Only methane was used in runs conducted with the crude oil. It was found that under similar tests conditions the oil and gas production behaviour observed with mineral oil and crude oil was similar. Both oil systems displayed similar decline in the oil recovery performance with decreasing rate of pressure depletion. It was concluded that the oil viscosity is the more important factor in foamy solution gas drive compared to the presence or absence of asphaltenes and other highly polar oil components.;The methane saturated mineral and crude oil depletion tests were numerically simulated with the CMG's advanced Thermal Model (STARS). It was found that it is possible to history match laboratory scale solution gas drive experiments using the foamy-oil model available in CMG-STARS. However, the foamy solution gas drive simulation parameters tuned by history matching a specific experiment do not provide good history matches of other experiments carried out at different rates in the same rock-fluid system. Therefore it was concluded that the predictive capabilities of currently available foamy solution gas drive simulation models are very limited.;The parameters examined included gas-oil-ratio (GOR), saturation pressure, and the type of oil (refined mineral oil versus crude oil). GOR was varied independent of saturation pressure by using different gases, namely, methane, ethane and carbon-dioxide. Each foamy oil system was fully characterized by measuring gas oil ratio, oil compressibility, live oil viscosity, surface tension and foam stability.