Laboratory experimental evaluation of enhanced oil recovery by CO2 huff-puff in edge-water heavy oil reservoir
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Graphical Abstract
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Abstract
At present, most of the experimental studies on CO2 huff-puff focus on the evaluation of the conventional huff and puff parameters. There are few experimental studies on CO2 huff and puff in edge-water heavy oil reservoirs, and even fewer on the coordinated recovery mode of displacement and huff-puff. In order to clarify the effect of CO2 injection to enhance oil recovery in edge-water heavy oil reservoirs in the laboratory, by taking ordinary heavy oil samples as an example, CO2 huff-puff experiments were designed and carried out to study the influence of the displacement timing. The development effect of coordinated displacement and huff-puff production mode (pressure-maintaining water injection or gas injection + CO2 huff-puff) is compared, in which the pressure-maintaining water injection simulates the influence of edge water invasion, and the purpose of pressure-maintaining gas injection is to compare the development effects of water flooding with CO2 flooding. The experimental results show that there is an optimal value for both CO2 injection amount and well soaking timing. When the water cut is lower than 50%, the CO2 huff-puff effect is the best. However, if the two oil production stages of water drive + CO2 huff-puff are considered, the total recovery efficiency is the highest when the water drive reaches 98% water cut. For the pressure-maintaining water injection or gas injection + CO2 huff-puff mode, the mechanism of edge-bottom water flooding and CO2 swelling reduction can be exerted, and the oil displacement efficiency of CO2 flooding is higher than that of water flooding. The results obtained in this experiment provide some reference for the implementation of CO2 huff-puff in edge-water heavy oil reservoirs.
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