Oil Production Mechanism of Water Injection Huff-n-Puff for Enhancing Oil Recovery in Tight Sandstone Reservoir

Abstract

It is difficult to establish an effective injection production well pattern in tight reservoirs, and water injection huff-n-puff is an important technology for EOR in late elastic energy development. The water injection huff-n-puff is established with a three-dimensional physical simulation experiment. The boundary conditions are simulated by setting up a pressure buffer device. The injection and production processes of horizontal wells are simulated by prefabricated artificial fractures at the injection port. The variation laws of 29 pressure points and 130 resistivity points can be effectively detected. Two cycles of experiments with different injection volumes are carried out, the change process of pressure and resistivity is analyzed, and the oil production mechanism is described. The fluid transfer velocity along the fracture extension direction is higher than that in the vertical fracture extension direction. The effect of the first cycle of the water injection huff-n-puff is significantly better than that of the second cycle. The change rule of oil recovery and oil change rate with different injection volumes shows that there is an optimal injection volume to maximize the on-site implementation benefits. The experimental results provide a theoretical and experimental basis for EOR by a water injection huff-n-puff in tight reservoirs.