Experimental investigation on enhanced oil recovery by hydraulic pulsating wave driving

An experimental investigation was conducted to study the mechanism of enhancing oil recovery using hydraulic pulsating flooding in high water cut reservoirs. The study involved a series of laboratory experiments using both a visual rectangular glass bead-packed physical model and an invisible rectangular sand-packed physical model. Following a complete stable water flooding, the pulsating pattern is used to continue the formation water injection. The effects of frequency and amplitude of hydraulic pulsation on the enhanced oil recovery efficiency were tested and analyzed. The hydraulic pulsating flooding stimulates pore pressure jumps repetitively. As a result, the residual oil films adhered on the surface of rock pore throats are stripped and swept progressively. This process enhances oil displacement efficiency. Moreover, hydraulic pulsations can induce additional pressure disturbances that break the mechanical equilibrium at the micro interface of the oil-water-solid three-phase system within the pores. This process stimulates the deformation and movement of the oil-water interface, overcoming the Jamin effect and segregating the oil phase into minute droplets persistently. Under a specific amplitude of pulsating pressure, an optimal pulsation frequency of 0.025 Hz is identified to yield the highest water flooding recovery rate. At this optimal frequency, a critical pulsation amplitude of 5 mL/min exists. Beyond this critical amplitude, oil recovery increases with the amplitude of pulsation linearly. Experimental results indicate that employing hydraulic pulsating waves for water flooding can achieve a maximum enhanced oil recovery rate of 14.47%.