Effects and Mechanisms of Acidic Crude Oil-Aqueous Solution Interaction in Low-Salinity Waterflooding

摘要

Crude oil-aqueous solution interactions play an important role in low-salinity waterflooding, but their effects and mechanisms have not been well clarified. Core flooding experiments were first conducted to analyze the effects of crude oil-aqueous solution interactions on enhanced oil recovery (EOR). Then, interfacial tension (IFT) and interfacial dilatational rheology (IDR), total organic carbon (TOC), and zeta-potential measurements were combined to investigate the mechanisms of crude oil-aqueous solution interactions in low-salinity waterflooding. Core flooding results showed that crude oil-aqueous solution interactions are important in low-salinity waterflooding and that adjusting the ionic composition of the aqueous solution could affect EOR. Herein, Mg2+ and Ca2+ both had positive effects on EOR, while SO42- showed no positive effect. The IFT and IDR, TOC, and.-potential results indicated that the ionic composition of aqueous solutions has a great influence on crude oil-aqueous solution interactions. Thereof, Mg2+, Ca2+, and Na+ preferentially interact with acidic polar molecules and enhance crude oil-aqueous solution interactions, and the intensity is Mg2+ Ca2+ Na+. SO42- interacts with cations and acidic polar molecules simultaneously, consequently reducing the effects of cations on crude oil-aqueous solution interactions in varying degrees. Therefore, the positive effects of Ca2+ and Mg2+ exceed the negative influence of SO42- in CaSO4 and MgSO4, while the negative impact of SO42- outweighs the positive effect of Na+ in Na2SO4.