Steam injection is one of the well-known thermal recovery processes that has been extensively applied to heavy oil reservoirs. Several efforts have been made to understand theoretical and practical aspects of steam injection and alkali flooding. However, the detailed information about the performance of steam-alkali flooding in field applications has not been deeply addressed yet. In this sense, in order to shed light on the background and applications in this area, this study comparatively investigates the efficiency of different strategies of pure steam injection and cyclic steam-alkali flooding in Bati Raman oil field, Turkey.
Three experiments were conducted to evaluate the advantage of steam-alkali injection compared to pure steam injection for an 11.6° API Bati Raman crude oil. The steam injection system consists of two reservoirs for water and the alkali solution, an electrical pump, and an electric steam generator. Those three experiments are as follows; conventional pure steam injection, cyclic injection of steam and alkali solution 4.0 wt%, and cyclic injection of steam and alkali solution 8.0 wt%. Steam was injected with the rate of 10 ml/min at 110°C and the system pressure was set to be the atmospheric pressure. The liquid produced from the separators is sampled periodically to determine the oil recovery.
Observation of sand packs after the experiments indicates the tendency for steam channeling in the vertical direction around the upper thermocouple. Since the upper thermocouple was inserted after the sand packing operation by pressing and rotation, steam could be passed through these channels without entering the all pores in the porous media. The average oil recovery by conventional pure steam injection, steam-alkali solution 4.0 wt% injection, and steam-alkali solution 8.0 wt% are 8%, 3% and 5.5% OOIP (original oil in place), respectively. This indicates that although the oil recovery in conventional pure steam injection was maximum, increasing the alkali concentration in the aqueous solution from 4% to 8% has caused the improvement in the recovery.
The theoretical and practical information is supported by the experimental examples to evaluate the performance of different steam-alkali flooding strategies with Borax in heavy oil reservoirs of Bati Raman. This study also examines the challenges of steam-alkali flooding in extremely heavy oil reservoirs and explains that the pure steam injection is preferred due the insufficient change in interfacial tension during Borax injection process.