CO2驱气溶性降混剂提高采收率机理实验

针对CO2驱气溶性降混剂降低混相压力、提高采收率机理认识不清的问题,综合利用室内实验、数值模拟和权重分析法,通过分析原油组分、原油黏度、油气界面张力、原油相态特征的变化,明确了气溶性降混剂的降混机理.实验结果表明:注入体积分数为3％和20％的气溶性降混剂后,原油重质组分含量分别减少25.07％和48.21％,平均原油黏...

Experiment on the Mechanism of Enhancing Oil Recovery by CO2 Flooding with Gas-soluble Demixing Agent

In view of unclear understanding of the mechanism of reducing mixed-phase pressure and enhancing oil recovery by CO₂flooding with soluble demixing agent,the demixing mechanism of gas-soluble demixing agent was clarified by analyzing the changes in crude oil composition,crude oil viscosity,oil-gas interfacial tension and crude oil phase characteristics in combination with laboratory experiment,numerical simulation and weight analysis.The experimental results showed that after injecting the gas-soluble demixing agents of 3%and 20%volume fraction,the content of heavy components in crude oil was reduced by 25.07%and 48.21%,the average crude oil viscosity reduced by 61.51%and 96.88%,the interfacial tension between crude oil and CO₂reduced by 30.36%and 91.16%at the same pressure,and the saturation pressure reduced by 6.22%and 15.90%,respectively.The dominant demixing mechanism of gas-soluble demixing agent was to crack the heavy components of crude oil,reduce the crude oil viscosity and decrease the oil-gas interfacial tension.The study also analyzed the oil displacement mechanism for oil recovery enhancement by mixed injection and plug injection of gas-soluble demixing agent and CO₂,and clarified the seepage characteristics of different affected areas in the formation,namely there was two-phase seepage of CO₂or gas-soluble demixing agent and formation crude oil in the mixed injection area,and three-phase seepage of CO₂,gas-soluble demixing agent and formation crude oil in the mixed-phased area.This study provides a basis for the optimization and field practice of the gas-soluble demixing agent for CO₂flooding.