Investigation of oil recovery improvement by coupling an interfacial tension agent and a mobility control agent in light oil reservoirs. Technical progress report, January--March 1995

Two series of corefloods were performed to improve alkaline-surfactant-polymer oil recovery economics. In these series of corefloods, the objective was to increase oil recovery by changing the chemical injection sequence. An alkaline gradient was evaluated in the first series of corefloods. Radial corefloods using Berea core were performed in which a pre-flush of alkaline-polymer solution was injected before the alkaline-surfactant-polymer solution. 30% pore volume (PV) of 1.0 wt % Na{sub 2}CO{sub 3} plus 0.2 wt % Petrostep B-100 plus 500 mg/l Flopaam 3330S was injected followed by 30% PV 500 mg/l Flopaam 3330S. A 5% PV 2.0 wt % Na{sub 2}CO{sub 3} plus 500 mg/l Flopaam 3330S followed by 5% PV 1.5 wt % Na{sub 2}CO{sub 3} plus 500 mg/l Flopaam 3330S was injected prior to the alkaline-surfactant-polymer solution in the coreflood with an alkaline-polymer pre-flush. A water flush of 1.5 to 2 PV followed chemical injection. The pre-flush objective was to inject sufficient alkali to satiate consumption and to force the surfactant to go through optimum interfacial tension and phase behavior states. Incremental oil recovery increased 24% from 0.106 PV (30.3% waterflood residual oil) to 0.131 PV (38.6% waterflood residual oil) when an alkaline-gradient pre-flush was injected. The effect on the oil recovery economics of an alkaline-polymer pre-flush is shown in Table 2. Oil recovery as well as the mass of alkali and polymer injected increased making the cost per incremental barrel of oil unchanged