Effects of Interfacial Tension, Emulsification, and Surfactant Concentration on Oil Recovery in Surfactant Flooding Process for High Temperature and High Salinity Reservoirs

Abstract

Surfactant flooding as a potential enhanced oil recovery technology in depleted reservoirs after water flooding has attracted extensive attention. In this study, 12 surfactants belonging to five different types of surfactants and their compounded formulations were investigated for surfactant flooding under 90−120 °C and 20 × 10 4 mg/L salinity. Two surfactant formulations obtained a stable ultralow interfacial tension (IFT) level (≤10 −3 mN/m) with crude oil after aging for 125 days. The surfactant formulations were used to further investigate the effects of the initial IFT values, the dynamic reduction rate of IFT, and the surfactant concentration and emulsification on oil recovery through core flooding experiments. The results indicated that oil recovery increased with the decrease of the initial IFT values and the increase of the dynamic reduction rate of IFT. The 10 −3 mN/m IFT level yielded an additional oil recovery of approximately 7% compared with the 10 −1 mN/m IFT level. However, under the same IFT level (10 −4 mN/m), it was not the bigger the surfactant concentration that resulted in a higher additional oil recovery. In four surfactant concentrations (0.2%, 0.5%, 1%, and 3%), the 0.5% surfactant formulation obtained the highest oil recovery of 36.65%. Further study manifested that emulsification has important effects on oil recovery. When surfactant concentrations were increased to 1% and 3%, the emulsification was too strong, which makes it more difficult to displace oil. The two selected surfactant formulations could successfully yield additional oil recovery of 20−26%, which indicates these two formulations have great potential for improving oil recovery in high temperature and high salinity oil reservoirs.

A comprehensive review of emulsion and its field application for enhanced oil recovery

“…It was also found in surfactant flooding field tests that, although the oil‐water interfacial tension is low, the oil recovery is not high if little or no emulsion is produced. Therefore, the research emphasis on the surfactant is important to increase the emulsifying performance …”

“…Therefore, the research emphasis on the surfactant is important to increase the emulsifying performance. 106,107 It is important to improve the emulsion performance of surfactant in chemical flooding. The mobility of displacing fluid can be controlled by forming emulsion through interactions between surfactant and crude oil, which can expand the sweep volume.…”

Effects of silica-based nanostructures with raspberry-like morphology and surfactant on the interfacial behavior of light, medium, and heavy crude oils at oil-aqueous interfaces

“…Altering the IFT at the oil-aqueous interface in a reservoir is necessary for generating the mobility and recovery of both the oil that is trapped within the small pores of the geologic formations and the residual oil that remains within the pores after the secondary recovery phase Bagherzadeh 2013, 2015;Joonaki and Ghanaatian 2014;Yuan et al 2015;Hu et al 2016a;Pu et al 2016). The wettability of an oil reservoir is dependent on the conditions that exist at the pore interfaces, conditions which govern the stability and movement of the interfaces and the resulting oil migration.…”

Numerical Approach for Enhanced Oil Recovery with Surfactant Flooding using STARS (CMG)

“…When the surfactant concentration exceeds 0.8 %, the interfacial tension increases instead of decreasing further. This is because, higher concentrations of surfactants will cause a ramification of distribution change of surfactant molecules in the interface of oil and water and this may lead to overly strong emulsification (Yuan et al, 2015).…”

“…Based on this result, the balance between ultralow IFT and emulsification must be balanced to optimise oil recovery using surfactant flooding. However, according to the capillary number theory, in reducing residual oil saturations and improving oil production, reduction of IFT between oil and water is still pivotal and more effective than the factor of emulsification (Yuan et al, 2015).…”