Evaluation of waterflooding using carbonated water for oil recovery

Abstract

Malaysian oilfields especially in Malay basin are showing the signs of maturity phase that involves high water-cut and pressure declining, after more than 30 years of extensive exploration and production. In recent development, Malaysia underwent Water Alternating Gas (WAG) process in the Tapis field to improve oil recovery. However, WAG, which utilises carbon dioxide in the Enhanced Oil Recovery (EOR) process has a few flaws that includes poor sweep efficiency due to high mobility ratio of gas and oil, which promotes an early breakthrough. Therefore, a concept of carbonated water injection (CWI) to utilise carbon dioxide was applied. The aim of this study was to measure the suitability of carbonated water to be implemented in oil recovery at high pressure condition, simulating reservoir condition. The simulated reservoir condition was made using a coiled sand pack filled with rounded grain glass beads and pressurised to 2000 psi with 60 °C as a controlled condition. A series of displacement test to investigate the range of recovery improvement at different carbon dioxide concentrations were carried out using different recovery mode stages. Wettability analysis has also been done to analyse the wettability of sandpack treated with carbonated water. The result from this study has shown a positive improvement in oil recovery with 50% concentration of carbon dioxide showed the highest recovery where it recovered additional 28% oil in secondary recovery and 16% recovery in tertiary recovery. Carbonated water also has the ability to alter the wettability of sandpack and sandstone rock to become more water-wet condition. Moreover, carbonated water was more suitable to be in the secondary recovery process, replacing the plain waterflood process, which is a common practice in every field. As a conclusion, carbonated water has a high potential in oil recovery processes, in both secondary and tertiary stages.