Evaluation of Novel Surfactant for Nitrogen-Foam-Assisted EOR in High Salinity Carbonate Reservoirs

Abstract

Abstract The use of Nitrogen in Foam Assisted Water-Alternating-Gas (FAWAG) can be an alternative to the use of polymer, especially in carbonate reservoirs which generally have low permeability and contain vugs and fractures, for improving the displacement efficiency in chemical-EOR process. In this process foam performs the role of a mobility control agent. By FAWAG process, reducing gas mobility can be achieved by creating more resistance to gas flow since gas bubbles are surrounded in foam by lamella. Oil displacement by foam is strongly dependent on reservoir temperature, pressure and crude oil composition. A number of surfactants have been tested with foam-assisted-N2 flooding. We are presenting a new class of surfactant. Two approaches were applied to determine the favorable concentration of each surfactant studied: solubility test and foam stability. The effect of salinity was investigated to determine the optimum concentration surfactant. Phase behavior was evaluated and it was observed that oil-in-water micro-emulsion is Winsor Type I. It is believe that low IFT can be obtained at high solubility ratio for the optimum salinity concentration. The performance of foam flooding with nitrogen (N2) for oil recovery in limestone carbonate rocks was studied. The success of the FAWAG process was determined by evaluation of oil recovery, pressure response and effluent from coreflooding experiments. The effects of core permeability, alkaline, and type of surfactants on the performance of the FAWAG were evaluated as well. Maximum recovery of 47.7% of residual oil in place in low permeability was observed compared to 43% of residual oil in place on high permeability core. In addition, the more recovery was obtained when using surfactant without alkaline.