Experimental study on enhanced foamy oil recovery after solution gas drive by waterflooding

Key words:  enhanced oil recovery  foamy oil  waterflooding  pressure at injection timing  pseudo-bubble point  water imbibition

Abstract:

The influences of pressure at injection timing and injection rate on the waterflooding were investigated through physical simulation experiment, and the mechanisms of foamy oil recovery by waterflooding were explored. The results show that the foam oil stream is the main recovery phase during the dissolved gas drive in heavy oil, which dominates 90.91％ of the primary recovery rate. In the waterflooding of the natural depletion, the primary recovery gradually increases and the waterflood recovery decreases in a stepped law with the pressure at injection timing decreasing. The ultimate recovery reaches the maximum of 35.71％ at the pseudo-bubble point of 3.1MPa approximately. The stability of waterflooding is possibly influenced by the varying distribution of oil and gas in porous medium aroused from the difference of core pressure. And the influence is significant only before the water cut is high. Water imbibition is the main mechanism of displacement after water breakthrough in water wet medium. The effect of water imbibition relatively increases with the decrease of injection rate, which leads to a higher recovery. The waterflooding recovery can be improved by 13.11％ when changing the injection rate from 2.5mL/min to 0.01mL/min.