特低渗储层孔隙结构对CO2驱特征影响

由于强烈的成岩作用，特低渗储层孔隙结构特征复杂，核磁共振实验结果表明，渗透率相近的岩心具有不同的孔隙结构，实验特低渗岩心孔隙结构特征表现为双峰分散型、双峰偏细歪度型及双峰偏粗歪度型；通过核磁共振方法研究了孔隙结构对水驱及后续CO2驱特征的影响，结果表明，不同孔隙结构岩心CO2驱提高采收率机理不同，对于双峰偏细歪度型岩心，CO2驱主要驱替小孔隙中的富集原油，提高了微观波及效率；对于双峰偏粗歪度岩心，CO2驱主要驱替大、中孔隙中的残余油滴和油膜，提高了驱油效率，实验结果为CO2驱提高采收率机理研究及油藏优选提供了参考。

The effect of pore structure on CO2 flooding performance in ultra-low permeability reservoir

The strong diagenesis causes a complicated pore structure characteristic in ultra-low permeability reservoir. The experimental results of nuclear magnetic resonance show that cores with similar permeability have different pore structures, the pore structure characteristic of ultra-low permeability core show double peak dispersion, double peak with smaller slanting degree and double peak with bigger slanting degree. The effects of pore structure on water flooding and CO2 flooding performances were investigated through the method of nuclear magnetic resonance, the results indicate that the enhanced oil recovery mechanisms of CO2 flooding in natural cores with different pore structure are different, for core with type of double peak with smaller slanting degree, the enrichment oil in small pore are mainly displaced, and the microscopic swept efficiency is improved. In contrast, for core with type of double peak with bigger slanting degree, the residual oil and oil film in big and medium pore are displaced, and oil displacement efficiency is increased. The experiments provide references for the study on the recovery mechanism of CO2 flooding and the optimization of reservoir.