Synergy of a deep eutectic solvent and tea saponin on foam flooding EOR in a high salinity clay mineral rich heavy oil reservoir

Abstract

Foam flooding is a common tertiary oil recovery method. When developing heavy oil with high salinity and clay minerals, conventional foaming agents cannot produce stable foams, effectively inhibit hydration and swelling of clay minerals, and do not improve oil recoveries. In this paper, a new system comprising a citric acid-based deep eutectic solvent (DES, molar ratio of choline chloride: citric acid = 1:1) and tea saponin (TS) solved the problem of strong water-sensitivity and high salinity in heavy oil reservoirs. The physical and chemical properties of the new DES/TS system were evaluated in laboratory experiments and the EOR mechanism of the new DES/TS system in highly water-sensitive reservoirs was revealed. Those results showed the interfacial tension (IFT) between the DES/TS system and heavy oil was ∼ 10-3 mN/m. The foam formed by the DES/TS system showed good salt tolerance. Furthermore, the DES/TS system changed rock wettability. The DES/TS system significantly inhibited the hydration and swelling of clay minerals. It greatly reduced the water sensitivity damage of the formation. The recovery ratios of heavy oil reservoirs increased by 12.29%. This study provides a new approach for a natural foam DES/TS that inhibits water sensitivity damage. This may significantly improve the recovery ratio of high salinity clay mineral-rich heavy oil reservoirs.