Analytical investigation of wet combustion process for heavy oil recovery

Analysis of combustion tube data produced from experiments performed under realistic reservoir conditions is currently the most valid method of investigating in-situ combustion process. In this study, the optimization of water-air ratio for B. Kozluca heavy crude oil, and the comparison of the performance of dry and wet forward combustion processes were studied. An analytical model was used to extend the laboratory results so that the oil production and steam zone volume can be estimated under field conditions. A total of nine combustion tube experiments were carried out under adiabatic conditions in the laboratory using a steel tube that was 10 cm in diameter and 90 cm in length. Temperature distribution, air and water injection pressures and rates, produced gas analysis and rate, and oil and water production rates were recorded to analyze and calculate the combustion parameters. Instead of solving complex multiphase fluid flow and energy equations, an analytical model was developed based on energy balance using measured data from combustion tube experiments and basic reservoir and fluid properties. The analytical model can be used to determine the oil production from burned zone and steam zone. Calculated oil production values were successfully matched with the experimental values. Finally, the field performance was investigated by using a computer program based on the estimation of volume-burned. The program was run by changing areal sweep efficiency, pattern size and air injection rate to achieve the optimum conditions. It has been shown that the oil recovery can be increased from 3.68% to 33.4% of OOIP through this optimization.