New high-efficiency system for improving oil recovery based on the superwetting phenomenon

Given that a large amount of crude oil remains on the surface of rocks and is difficult to produce after conventional waterflooding, a new superwetting oil displacement system incorporating the synergy between a hydroxyl anion compound (1OH-1C) and an extended surfactant (S-C 13 PO 13 S) was designed. The interfacial tension, contact angle and emulsification performance of the system were measured. The oil displacement effects and improved oil recovery (IOR) mechanisms of 1OH-1C, S-C 13 PO 13 S and their compound system were investigated by microscopic visualization oil displacement experiments and core displacement experiments. The results show that 1OH-1C creates a superwetting interface and electrostatic separation pressure on the solid surface, which destroys the strong interactions between crude oil and quartz to peel off the oil film. S-C 13 PO 13 S has low interfacial tension, which can promote the flow of remaining oil and emulsify it into oil-in-water emulsions. The compound system of 1OH-1C and S-C 13 PO 13 S has both superwettability and low IFT, which can effectively improve oil recovery through a synergistic effect. The oil displacement experiment of low-permeability natural core shows that the compound solution can increase the oil recovery by 16.4 percentage points after waterflooding. This new high-efficiency system is promising for greatly improving oil recovery in low-permeability reservoirs.