Chemical agents for enhanced oil recovery: A comparison of a switchable hydrophilic solvent and deep eutectic solvent

Abstract

Switchable hydrophilic solvents (SHS) and deep eutectic solvents (DES) are trending chemical agents used in enhanced oil recovery. In this study, the oil recovery performance of DES, synthesized from tetrabutylammonium bromide (TBAB) and polyethylene glycol 400 (PEG 400) in a 1:2 molar ratio, and the switchable solvent N,N-dimethylcyclohexylamine (DMCHA) was evaluated through a displacement test. Additionally, the interactions between the rock, solvents, and crude oil were investigated through interfacial tension (IFT) measurements using an Altension tensiometer. The trend in the experimental IFT results was compared to the interactions between DMCHA and oil, DMCHA and rock, DES and oil, and DES and rock using quantum mechanics calculations performed with the Spartan v20 molecular modeling tool. The findings revealed that the IFT between the solvents and oil decreased to 5.32 mN/m with DES and 2.64 mN/m with DMCHA. Furthermore, core flooding experiments showed an incremental recovery of 12.0 % of the original oil in place (OOIP) with DES and 10.0 % OOIP with DMCHA for standard Berea sandstone core samples. Similarly, flooding experiments using Niger-Delta sandstone samples achieved an additional 25.8 % OOIP with DES compared to 12.0 % OOIP with DMCHA. In conclusion, both DES and DMCHA demonstrated their potential for crude oil recovery. However, DES proved to be more promising for tertiary enhanced oil recovery applications.