The main objective of this study was to qualitatively investigate the oil recovery from bottom drive reservoirs with tar barriers. Three experimental models were used, and the tar barrier was simulated using the Athabasca tar sands. Different unconsolidated sand systems were used as porous media for the oil and bottom water zones. The models were initially saturated with 2% (by weight) sodium chloride. Thereafter, the initial oil saturation was established by injecting Bradford crude into the oil zone.

The different recovery techniques tested were: (1) injection of water into the oil zone (internal waterflood) without any bottom drive, (2) internal waterflood with bottom drive, (3) injection of water into the bottom water zone (bottom waterflood) without bottom drive, (4) bottom waterflood with bottom drive, (5) continuous bottom drive without any waterflood, (6) injection of solvent into the tar zone as a secondary process followed by an internal or bottom waterflood, and (7) injection of steam into: (a) the oil zone, (b) the tar zone, and (c) the bottom water zone.

With regard to the waterflood process, the decisive factor in its application was found to be the existence of communication between the aquifer and the reservoir. Complete isolation of the oil zone by the tar mat requires establishing communication between oil and water zones by use of solvent or steam. Internal waterflood proved to be favorable especially if communication existed. Injection of water into the bottom water zone showed low recovery due to water coning and channelling. Results of solvent injection runs indicated that large volumes of solvent will be necessary to establish the communication between the oil and bottom water zones. A very active bottom drive can result in severe water channelling.

In the case of steamflooding, the injection of steam into the oil zone eliminated the benefit of the bottom drive. The favorable factors of this process were low water-oil ratio (WOR), low steam-oil ratio (SOR), and short production period. Injection of steam into the tar zone proved to be effective, and moderate values of WOR and SOR were encountered. The process of steam injection into the bottom water zone required large volumes of steam, and very high WOR and SOR were the highlights of the process. It was observed that injection of steam into the bottom water zone might be considered if recovery of bitumen is an objective.