裂缝性致密油藏超临界CO2泡沫驱规律实验研究

超临界CO2泡沫可以有效降低CO2流度,提高封堵强度,抑制CO2在裂缝性致密油藏岩心中的窜流。在接近油藏条件下对8种起泡剂进行评价,优选出稳定性最好的起泡剂;研究不同气液比、裂缝开度及注入方式下超临界CO2泡沫的岩心渗流特征,分析水驱和气驱后超临界CO2泡沫驱油规律。结果表明:质量分数为0.5%时,起泡剂HY-2稳定性最好;气液比为1.0时对裂缝性致密岩心封堵效果最好,对裂缝开度在39.80~82.67μm时有较好的适应性,气液同时注入更有利于提高超临界CO2泡沫封堵效果,在水驱或气驱基础上,超临界CO2泡沫驱可使采收率提高20%以上。因此,一定条件下的超临界CO2泡沫驱对裂缝性致密油藏提高采收率有显著效果。

Experimental study on supercritical CO2 foam flooding in fractured tight reservoirs

The supercritical CO2 foam can effectively reduce the mobility of CO2,increase the plugging strength,and inhibit the channeling of CO2 in fractured tight cores. By evaluating eight kinds of foaming agents under conditions close to the reservoir,a foaming agent with the best stability is selected. The core percolation characteristics of the supercritical CO2 foam flooding under the different gas-liquid ratios,fracture openings and injection modes are studied,and the law of the supercritical CO2 foam flooding after water flooding and gas flooding are analyzed. The results show that the foaming agent HY-2 has the best stability when the mass fraction is 0.5%;when the gas-liquid ratio is equal to 1.0,it has the best plugging effect on the fractured tight cores and the good adaptability to the cores with the fracture openings of 39.80-82.67 μm. The simultaneous injection of gas and liquid is more conducive to improving the plugging effect of the supercritical CO2 foam flooding. There is an increase in oil recovery of more than 20% with supercritical CO2 foam flooding compared to water flooding or gas flooding. Therefore,the supercritical CO2 foam flooding under certain conditions has a significant effect on improving oil recovery of the fractured tight reservoirs.