Evaluation of Low Saline “Smart Water” Enhanced Oil Recovery in Light Oil Reservoirs

Abstract

With the depletion of natural driving forces responsible for pushing theoil from reservoirs & declination of oil recovery after secondary stage, the emphasis is now on EOR techniques. The low saline flooding is atype of EOR which gains the attention ofresearchers due to its easiness to use implications, less cost &environment-friendly nature. Though the low salinity effecthas been seen in various labscale core flooding experiments as well as fieldpilot projects, the mechanism which actually leads to thisenhancement in recovery is still the area of research among researchers whichis wide open and needs to gain consensus. Seeingthe wide mechanisms taking place under different scenarios, it is certain that more than one mechanism is actually supplementingeach other in reducing the residual oil saturation while LSW flooding. Thisstudy has been undertaken investigations on the low saline flooding inunconsolidated Ottawa sandpack cores with two different, Weyburn & Pelican crude oil, to find out the optimumsalinity, LSW Slug Size & underlying mechanisms during LSW flooding.Several core flooding experiments were performed under secondary as well astertiary recovery stage by unsteady state method. With the reduction of brinesalinity from 5000 PPM to 1500 PPM, the oil recovery increasedin secondary stage & decreased further upon reduction insalinity to 500 PPM gaining the peak at 1500 PPM. Small enhancement in tertiaryrecovery of 2.24% observed upon switching to 1500 NaCl PPM brine after injectionof formation brine in secondary stage for WeyburnOil, though large tertiary recoveries of the order of 9.95% foreffective oil viscosity of 4 cP and 7.32% for 29.7 cP were observed for n-dodecane diluted Pelican Oil.LSW slug size of 25% pore volume was found to be effective in producing WeyburnOil in secondary stage.