Ionic Liquid Application To Prevent Asphaltene Precipitation and Deposition during Water-Based EOR Techniques

In this study, systematic experiments were designed toinvestigatethe effect of water/saline water and ionic liquid additives on asphalteneinstability. The results revealed that emulsified water can lead toasphaltene precipitation up to 75.81% of the asphaltene content inthe synthetic oil. The FTIR analysis illustrated that the heteroatomsin the asphaltene structure control the asphaltene precipitation atthe water-oil interface. It was observed that the salinityhas a dual effect on asphaltene instability so that asphaltene precipitationincreases with an increase in salinity up to 20,000 ppm, whereas itdecreases with a further increase in salinity. The "salting-in"and "salting-out" effects were used to describe thisobservation. By comparing the effects of four different salts (NaCl,Na2SO4, MgCl2, and MgSO4), it was found that Mg2+ intensifies the asphaltene instabilityrather than Na+, while the presence of SO4 (2-) hinders asphaltene precipitation in comparison toCl(-). The Hofmeister series was proposed for thefirst time to justify the effect of anions and cations on asphalteneinstability in the presence of water. Moreover, the performance ofthree synthesized ionic liquids (TBAST, TBAOL, and TBACiN) to preventasphaltene instability was investigated. The results revealed thatthe ionic liquids act through two mechanisms: (i) by replacing asphalteneabsorbed on the water-oil interface and (ii) by transferringto the oleic phase and dispersing asphaltene molecules. The betterperformance of TBAST in reducing asphaltene precipitation by up to72.7% demonstrated the key role of alkyl length in the structure ofionic liquids. Finally, the dynamic test results indicated that adding1348 ppm TBAST to the injected saline water reduces asphaltene precipitation/depositionby 83.7% and enhances the ultimate recovery factor from 49.73 to 71.35%.