Micro and macro evaluations were conducted to understand modified enzyme EOR mechanisms using various fluids. Huff n puff tests and flooding tests were carried out with variable modified enzymes concentrations in several reservoirs. Resulted production performances were considerably improved. At reservoir temperature 50–80°C, lab experiment indicated that the modified enzyme solution was adaptable to both light and heavy oil and was not sensitive to minerals water with bivalent cation (1000mg/l) and high salinity (10%). The enzyme working performances were further enhanced with microorganism occurrence in the solution. Micro modeling experiment revealed that spontaneous emulsification and solubilization could take place between the modified enzyme and crude with emulsion particle 2–6μm in diameter, which is produced through striping as a result of solubilization. Core desorption and flooding experiments presented that desorbed crude volume and displacement efficiency were related to modified enzyme concentrations which usually ranged 5 to 10% with the optimum being 8%. In optimal conditions, recovery can be averagely increased by 16.9%. Experiments also proved that the modified enzyme and crude oil could form emulsion but the emulsion was not stable. One specific pilot test with modified enzyme had achieved additional oil production 22,869 bbl.

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