Exploring the efficiency of Prosopis farcta saponin as a biogenic surfactant for enhanced oil recovery from oil reservoirs: An experimental study

Surfactant flooding, as a chemical enhanced oil recovery (cEOR) technique, boosts oil production from oil reservoirs through lowering oil–water interfacial tension (IFT) and altering reservoir rock wettability from oil wet state to water wet. Recently, environmental concerns have encouraged researchers to turn more to use plant-based surfactant as cEOR agent. In the current study, the performance of the purified saponin from Prosopis farcta extract as a natural surfactant was evaluated for EOR applications. Initially, the validity of the purified saponin was analyzed using Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA) and proton nuclear magnetic resonance (¹H NMR) to confirm saponin purification, thermal stability and structure integrity. Prior to EOR experimental tests, the critical micelle concentration (CMC) of the developed saponin was identified from the behavior of the electrical conductivity and surface tension results with increasing saponin’s concentrations. Thus, a surfactant solution prepared with 3000 ppm demonstrated the best performance and thus concentration was identified as saponin’s CMC point. At the same concentration, the IFT was reduced from the initial value of 29 mN/m to 6.56 mN/m and further decrease was obtained as 2.91 mN/m when NaCl was added to the solution. Meanwhile, the developed saponin at CMC range altered sandstone and carbonate rock wettability from strongly oil wet to water wet by reducing contact angles (CAs) of oil droplets to 64.57° and 44.8°, respectively. The findings of foamability and emulsification analyses exhibited that the Prosopis farcta saponin was capable in forming a stable foam and emulsion system. Ultimately, coreflooding test at CMC revealed that the recovery factor was enhanced by 9.65 and 11.48 % original oil in place (OOIP) from sandstone and carbonate core plugs, respectively, compared with waterflooding.