| The overall oil recovery of some of the heavy oil reservoirs under solution gas drive is higher than what would be expected from an extrapolation of the behavior of light oil reservoirs to the high oil reservoirs. The objective of this research was to investigate the individual and combined effects of capillary, viscous, and gravity forces on solution gas drive process in heavy oil reservoirs and to relate the observed performance to the well-known capillary number term.;In the first part of the study, depletion tests were carried out in a horizontal sand-pack at different depletion rates. During the depletion, the capillary number varies with the position in the sand-pack and with the extent of pressure depletion. An examination of the changes in capillary number during the test provides insight into the gas-phase build up during solution gas drive and the resulting production behaviour. Furthermore, it was found that relative permeability to gas decreases as the capillary number increases. Foamy oil flow and the resulting low gas mobility are instrumental in providing the improved performance of solution gas drive in heavy oil reservoirs.;In the second part of the project, depletion tests were performed at different rates with the sand-pack held in vertical orientation. One of the findings of this study was that the effect of gravity on oil production from heavy oil reservoirs under solution gas drive has three responses based on the capillary number. First, at high capillary numbers the gravity force does not affect the oil recovery performance. Second, at intermediate capillary numbers, more oil is produced against the gravity force, i.e. with production from the top end of the sand-pack. Third, at very low capillary numbers, more oil is produced when it flows in the same direction as gravity. (Abstract shortened by UMI.)... |
