Surfactant alternating carbonated water injection (SACW) is a new process for enhanced oil recovery

Abstract

Surfactant alternating carbonated water (SACW) injection is a novel mode for Enhanced Oil Recovery (EOR), a method to produce residual oil by injecting surfactant solution slug followed by carbonated water slug. Dissolving carbon dioxide (CO2) in brine water injection may overcome the shortcomings that seriously associate with the tertiary process of CO2 injection such as high CO2 mobility, viscous fingering and gravity override, poor sweep efficiency. The surfactant solution (S) slug alternating carbonated water (CW) slug might reduce the gas mobility at displacement front and retard CO2 breakthrough. In addition, surfactant and CO2 can reduce interfacial tension between oil and water reservoir. The sodium dodecyl sulphate (SDS) surfactant was used in surfactant flooding. In addition, the sand pack flooding experiments has been performed in this work. Glass beads were packed into 34.5 cm length and 3.8 cm diameter of stainless steel tube (sand pack) with small holes in both sides. The synthesized sodium chloride solution (brine water) and crude oil saturated the sand pack to establish Swi and Soi. Thereafter, the sand pack was aged at reservoir temperature of 60 °C and pressure of 2500 psi for 4 days to create actual oil reservoir conditions. Furthermore, different injection strategies were carried out including with different slug sizes in pore volume (pv) of SACW such as 0.25 pv (S) followed by 0.75 pv (CW), 0.5 pv (S) followed by 0.5 pv (CW) and 0.75 pv (S) followed by 0.25 pv (CW) in order to find out the optimum injection strategy to obtain the highest oil recovery factor. The obtained results illustrated that the scenario of 0.75 pv of surfactant slug alternating 0.25 pv of carbonated water showed the highest oil recovery factor of 86.58%. This is may be attributed to the efficiency of surfactant slug is higher than carbonated water slug.