Enhanced oil recovery from UAE limestone reservoirs using bacteria flooding, an experimental approach

The use of bacteria to improve oil recovery from the UAE limestone reservoirs was studied. The bacteria were obtained from local water tanks. The system temperature was varied between 30°-100°C and salinity ranged from 0 to 100,000 ppm. Bacteria solution tertiary core flooding experiments were then performed using carbonate rocks at reservoir conditions without injection of nutrient with the bacteria during the core flooding experiments. A good amount of effort was directed to characterize the bacteria used and identify the mechanism by which bacteria work to improve the oil recovery. Results of these laboratory studies showed an abrupt reduction in the interfacial tension between crudes from four different UAE reservoirs at high salinity and high temperature for all studied systems except one, which was sulfur rich. The interfacial tension decreased from 40 to 0.07 dyn/cm for most of the studied systems. Also, tertiary bacteria flooding at reservoir conditions, on average, resulted in an incremental oil recovery of 15-20% of the pore volume.