Effects of microfracture parameters on adaptive pumping in fractured porous media: Pore-scale simulation

Adaptive pumping, exchanging injection and extraction well locations, has achieved good performance in many subsurface operations such as enhanced oil recovery, CO2 sequestration, and aquifer contaminant remediation. However, the pore-scale flow mechanism behind this phenomenon and the effect of fractures on it are poorly understood. In this study, the phase field method is used to trace the interface evolution in the matrix with different fracture parameters, such as width, length, orientation angle, and tortuosity. The results show that the presence of fractures converts the flow regime from continuous pathway flow (CPF) to ganglion dynamics (GD), which improves the transfer kinetics of the displacing fluid. Fracture width and tortuosity significantly affect the ultimate displacement efficiency in positive pumping, while the orientation angle has the most significant effect in adaptive pumping. The disintegration of the residual displaced fluid into smaller ganglia is the displacement mechanism of adaptive pumping, but it is suppressed in fractured porous media. The adaptive pumping reaches the maximum displacement efficiency when the fracture is vertical to the flow direction, which is 15.12% higher than that of the positive pumping in the non-fractured model. These results can bridge the cognitive gap between micro- and macro-phenomena and guide practical engineering.