Solution-Gas Drive in Heavy Oil: Field Prediction and Sensitivity Studies with Low Gas Phase Relative Permeability

Abstract

The favourable behaviour of heavy oil reservoirs under solution-gas drive has intrigued the oil industry for long. Many mechanistic models have been proposed to explain this behaviour. It is believed that the flow in heavy oil reservoir is quite complex and cannot be represented by one theory alone. This paper investigates one of the theories that attribute this behaviour of heavy oil reservoirs to low gas mobility. Simulation is carried out on a commercial black oil simulator to match the production data of heavy oil fields in Lindbergh and Frog Lake. Further, sensitivity studies are carried out to investigate the effect of various parameters in gas relative permeability model, on oil recovery in a radial geometry. The effect of sand production, which is an integral part of heavy oil production in Western Canada, is also investigated. A new parameter is used in the simulator to model the increase in permeability due to sand production. Finally, the results obtained from simulation in radial geometry are compared with that obtained in linear geometry.The results indicate that the field performance can be predicted by assigning low gas phase relative permeability values and incorporating improved permeability due to sand production. Neither of them by itself can model the field performance. It is concluded that the sand production increases the effective permeability of the reservoir in the far away field too. The low gas mobility is successful in explaining high pressure gradients and pressure maintenance mechanism observed in the field, and may be attributed as one of the reasons leading to favourable behaviour of heavy oil reservoirs.

Use of Air with Methane in Cyclic Solvent Injection Applications for Improved Foam Stability and Cost Effective Heavy Oil Recovery

“…Kumar and Pooladi-Darvish pointed out that at early stages the size of the bubbles is too small and can be neglected; nonetheless, it is at this stage that gas supersaturation is starting, and along with oil production, it eventually reaches bubble nucleation. This phenomenon can be observed in the pressure profiles when the recordings in the pressure gauges start deviating from the pressure in the producing end.…”

“…These reservoirs are characterized as having very viscous oils with very low mobility . An anomalous fluid flow behavior has been observed in reservoirs in Venezuela, China, Albania, Oman, and Western Canada, of which have been produced under primary production with a solution gas-driven mechanism. − This atypical behavior involves low producing gas–oil ratios (GOR), good pressure maintenance, and prominent primary production recovery − when compared with conventional solution gas drive performance. On the other hand, gas injection into heavy oil reservoirs is a common practice as the primary depletion results in low recovery factors.…”

Network Modelling of Apparent-Relative Permeability of Gas in Heavy Oils

“…It has been observed that matching of field (6) and laboratory depletion data (5) required assigning extremely low values of gas relative permeability. The relative permeability functions of these studies, however, were obtained through history matching.…”