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

Abstract

This project investigates the use of bacteria, which is a minor cost material, to improve the oil recovery from UAE limestone reservoirs. The work focused initially on the study of the interfacial tension (IFT) between crudes from four different UAE reservoirs (AH, UZ, St, and UAD) and a thermophilic microbial solution. The bacteria were obtained from local water tanks. The system temperature was varied between 30-100℃ and salin-ity 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, throughout the work, 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 IFT at high salinity and high temperature (ie reservoir condition) for all studied systems except for the St crude, which was sulfur rich. The IFT 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 to 20% of the pore volume.