Comparative studies of surfactant-enhanced-water, WAG and surfactant-enhanced-WAG injections in concurrent development of thin oil rim reservoir

Abstract

The goal of this paper is the comparative analysis of three injection fluid options: Surfactant-enhanced-Water (SeW), Water Alternating Gas (WAG) and Surfactant-enhanced-WAG (SeWAG). The objectives are to identify the best option with the highest oil and gas displacement efficiency and the best development strategy for optimum recoveries in concurrent development of an oil rim reservoir. The Eclipse simulator was used because of its robust ability in simulating various injection options of an oil rim reservoir in a green field. Four scenarios (base case/no injection, SeW, WAG and SeWAG injections) were simulated under the same conditions to determine injection option with the best displacement efficiency and recoveries of oil and gas. Statistical analysis using Pareto chart was performed for proper identification of the option with the best recoveries. The result showed that SeWAG injection ratio 1:4:2 and injection cycles 56 gave the best recoveries for oil and gas with displacement efficiency of 0.08 and 0.332 respectively, followed by SeW injection with values of 0.073 and 0.331 respectively, while WAG has the least performance. On the Pareto chart, SeWAG simulation result has the highest percentage among the options with the best recoveries of 3.35 MMSTB oil and 16.05 BSCF gas, which is 12.53% and 16.12% of oil and gas in place after 9.6% of oil and 15.1% of gas have been recovered by natural depletion. Hence, this study has shown that two stages of development strategy (combination of natural depletion and SeWAG injection when the reservoir pressure is depleted) give cumulative effect for optimal recoveries in concurrent development of oil rim reservoir.