A Comparative Study of Alkaline Flooding and Alkaline/Surfactant Flooding for Zhuangxi Heavy Oil

Abstract

In this study, a comparative study of alkaline flooding and alkaline/surfactant flooding was conducted for Zhuangxi heavy oil with viscosity of 325 mPa·s at 55 °C. The results of core flooding tests show that, the tertiary oil recovery of alkaline-only flooding with the alkaline concentration in the range of 0.4-1.0 wt% can reach 22% -31% OOIP. The coexistence of the surfactant and alkali can reduce the IFT between the heavy oil and aqueous phase to an ultralow level. However, the tertiary oil recovery of alkaline/surfactant flooding are lower than those of alkaline-only flooding. Further flood study via glassetching micromodel tests demonstrates that injected alkaline-only solution can penetrate into the oil phase and creates some discontinuous water droplet inside the oil. The subsequent formation of droplet flow tends to reduce the mobility of the water phase and damp viscous fingering, leading to the improvement of sweep efficiency. While for alkaline/surfactant flooding, because of the addition of the surfactant, these systems exhibit better capacity in emulsification and IFT reduction, the viscous oil can be break up into fine droplets and entrained along with the flowing aqueous phase. Therefore, viscous fingering phenomena are occurred during the displacement, resulting in its relatively lower oil recovery. Comparing the results of alkaline flooding and alkaline/surfactant flooding, improving the sweep efficiency by the droplet flow in alkaline flooding is more effective than lowering IFT by alkaline/surfactant flooding for heavy oil recovery.

Status of Alkaline-surfactant Flooding

“…Emulsions can improve the sweep efficiency, thus oil recovery is improved with an AS system. Recently, one interesting paper was presented by Pei [21]. They compared alkaline performance with AS performance.…”

The effect of alkaline–surfactant on the wettability, relative permeability and oil recovery of carbonate reservoir rock: experimental investigation

“…The results showed that by injecting alkaline-surfactant solution, the surface tension decreases and an emulsion between oil and water is processed and causes oil production without using thermal methods (Hunkey et al 2010). Pei et al (2012) studied injecting alkaline alone and injecting alkaline-surfactant simultaneously for heavy oil field. They found that tertiary oil recovery in injecting alkaline solution 4/0 wt% is equal to 21% of the original oil in place while adding surfactant to alkaline will increase oil recovery to 32%.…”

“…They found that tertiary oil recovery in injecting alkaline solution 4/0 wt% is equal to 21% of the original oil in place while adding surfactant to alkaline will increase oil recovery to 32%. They also found that adding surfactants to alkaline solution reduces surface tension that has an important role in the mechanism of enhanced oil recovery (Pei et al 2012). Experimental investigation of EOR using low salinity water and nanoparticles in one of southern oil fields in Iran was conducted by .…”

A Critical Review of Alkaline Flooding: Mechanism, Hybrid Flooding Methods, Laboratory Work, Pilot Projects, and Field Applications

“…After the end of alkaline flooding, 31.94% of oil recovery was achieved. Although in this field several other modifications were performed, including surfactant-alkaline flooding, the alkaline flooding generated fruitful results compared to other modes of chemically enhanced oil recovery [66]. The Shengli oil field formation and fluid properties are summarized in Table 5 [66][67][68].…”