Enhanced oil recovery by surfactant alternate carbonated water injection

Abstract

Surfactant alternate carbonated water (SACW) injection is a novel mode for enhanced oil recovery (EOR), a method to produce residual oil. This process may overcome the shortcomings that seriously associate carbon dioxide (CO2) injection such as high CO2 mobility, viscous fingering and gravity override. Combinations of sodium dodecyl sulfate (SDS) surfactant and carbonated water (CW) system were not used for EOR yet. So, SDS and CW were selected for evaluating wettability, interfacial tension (IFT), and displacement stability. In addition, the oil recovery factor (RF) was evaluated at different reservoir conditions, carbonation levels and SACW injection cycles scenarios. The sessile drop method was used to measure the contact angle in presence of CW, SDS solution and a mixture of CW and SDS at different quartz sandstone reservoir conditions. A sandpack model was utilised for CW, SDS, water flood (WF) and CO2 flood to measure the displacement instability number (Isc). The obtained results revealed that combinations of SDS and CW system reduce the IFT and contact angle. The IFT values for SDS solution with and without carbonation were 0.2 and 2 mN/m, respectively. The respective contact angles for SDS solution with and without carbonation were 32° and 21.7° at 50°C and 1500 psi. The Isc for CW and WF were 11.6 and 10, respectively, which are considered stable at 60°C and 2750 psi. On the other hand, SDS and CO2 flood processes revealed unstable displacement. Moreover, low pH of CW system depicted a significant change in the SDS adsorption on the glass beads as compared to non-CW system. The 100% CO2 content, reservoir temperature of 60°C and pressure of 2750 psi increased RF up to 83.05, 84.42 and 85.22%, respectively. The highest RF was 86.58% which procured from the largest SDS slug scenario. In conclusion, SACW may have a positive impact on the recoverable oil and it can display a technical knowledge to study other techniques for EOR.