Heavy oil recovery in blind-ends during chemical flooding: Pore scale study using microfluidic experiments

Abstract

The blind-end is a typical tiny structure widely distributed in reservoir rock. In this work, we used the microfluidics to observe the fluid flow phenomenon in blind-ends at pore scale. A microfluidic chip that contains four blind-ends with different widths was designed. The microfluidic chip is initially saturated with light oil or heavy oil. Then, deionized water, sodium oleate solution, or hydrolytic polyacrylamide solution is selected to inject into the microfluidic chip to displace the oil in blind-ends. We recorded the blind-end snapshots at different experiment conditions and then analyzed the variation of oil saturation quantitatively. Moreover, we explained the oil displacement mechanism in blind-ends with the perspective of micro force. The results demonstrated that the oil in wide blind-end is more easily displaced than the narrow blind-end due to higher shear force and lower capillary force. Heavy oil in blind-end is more difficult to displace from the blind-end due to higher viscous force and elastic force. Polymer flooding is more effective to light oil due to the extrusion swell effect. The reduction of capillary force caused by surfactant is beneficial to recover more oil from the blind-end. This work presents detailed oil displacement mechanism of blind-ends and can be a method to screen more effective chemicals for blind-end oil.