Experimental study on pressure control strategies for improving waterflooding potentials in a heavy oil-methane system

Experimental results show that the optimal pressure control strategy for the heavy oil-methane system is Strategy 2. The ultimate oil recovery and overall average production rate are inversely changed with the depletion rate increasing in Strategy 2. To get a balance between the ultimate oil recovery and overall average production rate, the optimal depletion rate, 2 kPa/min, is obtained. By comparing the performances of Strategy 2 under different depletion rates, the relationship of voidage displacement ratio (VRR) with the depletion rate as well as the optimal VRR for waterflooding are obtained. Moreover, it is found that, with depletion rate increasing, positive effects of depletion rate decrease at foamy oil flow stage and increase at solution gas drive stage.