Effectiveness of deep eutectic solvents for light oil recovery through spontaneous imbibition

Abstract

With the rise in demand for energy, comes the need to extract oil from not only primary and secondary stages, but also from tertiary recovery methods to keep up with the current market. Enhanced oil recovery (EOR) has become more prevalent within maturing reservoirs. Ionic liquids (IL) were highly regarded for chemical EOR until researchers raised concerns about their expensive cost, toxicity, and environmental impacts. Recently, deep eutectic solvents (DES) were discovered as a potential replacement for ILs due to their non-toxic nature, being biodegradable, non-flammable, and cheaper. In this study, the effectiveness of DES is investigated by observing its ability to promote oil recovery through wettability alteration. Spontaneous Imbibition tests along with emulsion and thermogravimetric tests (TGA) are used to achieve the objectives. Results indicated that both DESs can recover oil that was not recoverable using brine only. At higher temperatures, the effectiveness of DES was higher, which allowed for more oil to be imbibed out. The effect of concentration suggested that at high concentrations, DESs exhibit self-destructive properties by increasing interfacial tension (IFT), which reduced the imbibition rate and recovery factor. TGA studies indicate that the thermal stability of DESs is highly dependent on the thermal stability of their hydrogen bond donor (HBD).