Experimental Study on Microscopic Water-Flooding to EOR of Remaining Oil through Changing Flow Direction

To understand the type of remaining oil and the efficiency of enhanced oil recovery (EOR) in super-high water-cut oil reservoirs, experiments were conducted on the characteristic of oil displacement by water in micro-model. Based on analytical methods of geometric characterization of remaining oil and pore throats, remaining oil was classified. Moreover, flow direction effects on microscopic remaining oil were identified by using visible waterflooding test in micro-model, image recognition, statistical calculation technology, and other methods. Results showed that final oil saturation is 20.90% when flow direction remain unchanged. Nevertheless, it drops to 9.69% in continuous waterflooding if flow direction is changed, which could be raised by 11.2 percent of oil recovery. The research indicated that, the saturation of contiguous and branched remaining oil declines in exponential function, while the saturation of droplet, columnar or oil film remaining oil increases then declines in quadratic polynomial function with water injection after flow direction change. The research provides a theoretical basis for improving the recovery of remaining oil through waterflooding.