Study on effect of surfactant-assisted CO2 and dominating behavior of surfactant in heavy oil reservoirs

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    In light of the characteristics and development status of heavy oil reservoirs,three surfactants with different properties were compounded based on the evaluation of static foam properties and oil displacement performance. The oil displacement efficiency of CO2 flooding assisted by different surfactants was studied,and the dominating performance of the surfactants was clarified. The experimental results show that the recovery factor of the heterogeneous core with a permeability ratio of 3.0 grows by 19.7%,13.2%,and 15.2%,respectively after CO2 flooding assisted by surfactants S1,S2,and S3,which is superior to the oil displacement by direct CO2 injection. This demonstrates that the surfactants can improve the CO2 flooding of heavy oil reservoirs in the high water-cut stage. The mechanism of enhanced oil recovery(EOR)is mainly manifested as the oil displacement contributed by surfactants and the foam induced by the surfactants with subsequent CO2.When the emulsifying capability of a surfactant is stronger,the emulsification will be more evident,and the increase in oil displacement efficiency will be larger;stronger static foaming ability makes it easier to foam with CO2 in the core;the foam formed by CO2 with the surfactant of strong foaming ability but weak stability is more favorable for deep profile control. As the permeability ratio of the heterogeneous core increases from 3.0 to 9.0,the oil displacement efficiency of CO2 flooding assisted by the three surfactants declines to varying degrees. The increase in the recovery factor of S1-assisted CO2 flooding reduces to 12.6%,and compared with S2 and S3,S1 is more adaptable to the heterogeneous changes in the core. Therefore,for the target reservoir,the compound surfactant S1 with strong emulsification,strong foaming ability,but weak stability performs best in assisting CO2 flooding for EOR.

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  • Online: January 20,2022
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