Application of a novel natural surfactant extracted from Avena Sativa for enhanced oil recovery during low salinity water flooding: Synergism of natural surfactant with different salts

Abstract

The use of green, eco-friendly, efficient, and sustainable surfactants for enhanced oil recovery (EOR) is of great importance. In this study, a novel and unique natural surfactant was extracted from Avena Sativa (AS) plant commonly known as oat, to be used for EOR applications. The extracted saponin as a surfactant agent was confirmed using TGA, FESEM, 1H NMR, CHNS, and FT-IR analyses. The physico-chemical characteristics showed that the extracted nonionic surfactant from AS is very efficient and stable to be used for EOR applications. In order to have a better understating of the role of each ion during low salinity (LoSal) water flooding, nine different salts including NaCl, Na2SO4, CaCl2, MgSO4, MgCl2, K2SO2, KCl, NaHCO3, and Na2CO3 with constant ionic strength of 40.517 × 10-3, which is equal to the ionic strength of 2000 ppm diluted seawater (DSW2000) were prepared and tested in this study. The interfacial tension (IFT) measurement results showed that the critical micelle concentration (CMC) value of the natural surfactant is 4000 ppm. The IFT value of the natural surfactant at its CMC point was 6.45 and 3.65 mN/m for deionized water (DIW) and DSW2000, respectively. In addition, the IFT results showed that the CMC value of the natural surfactant was very effective with different salts in the range of LoSal water. Among all the tests performed by various salts, Na2CO3 was the most compatible salt with the natural surfactant in terms of IFT reduction (1.38 mN/m), while MgSO4 salt had the least impact on IFT reduction (6.63 mN/m). Moreover, the contact angle results reduced significantly when the CMC of the natural surfactant was used and reached the point of 38.28°, 55.12°, and 82.60° for Na2CO3, DSW2000, and MgSO4 salts, respectively. Furthermore, the most stable and the least stable emulsion tests were produced when the natural surfactant was mixed with Na2CO3 and MgSO4, respectively. The core flooding results showed that the injection of 5 PVs of the natural surfactant at the CMC point prepared in Na2CO3 as tertiary recovery increased the oil recovery factor (RF) by 28.89%.