低渗油藏碳化水-CO2交替注入提高采收率及CO2埋存研究

Investigation of Enhanced Oil Recovery and CO2 Sequestration in Low Permeability Reservoirs Through Carbonated Water Alternating CO2 Injection

  • 摘要: 低渗油藏非均质性强,注气开发易发生气窜。尽管水气交替驱可抑制气窜,但其开发效果依然有待提升。文章通过岩心驱替实验,结合核磁共振扫描,通过对比水驱、CO2驱、水气交替驱、碳化水-CO2交替注入的驱油与CO2埋存效果,探究碳化水-CO2交替注入提高采收率、实现CO2埋存的可行性,并利用油藏数值模拟分析注入速度、水气比和段塞体积对其效果的影响。结果表明:(1)碳化水-CO2交替注入的采收率为74.62%,分别比CO2驱、水气交替驱提高了8.40%、3.83%;大孔隙、中孔隙、小孔隙的采收率分别为85.34%、65.54%、44.06%;(2)碳化水-CO2交替注入的CO2埋存率为51.02%,高于CO2驱,略低于水气交替驱;(3)在文章研究参数范围内,随着注入速度增加,累积注入量增大,采收率提升,但CO2埋存率降低;水气比过高或过低均不利于采收率的提高,而高水气比有助于提升CO2埋存率;段塞体积减小能够同时提升采收率和CO2埋存率。由以上结果可知,碳化水-CO2交替注入可提高低渗油藏采收率、实现CO2埋存,是一种极具潜力的开发方法。

     

    Abstract: Low-permeability reservoirs exhibit pronounced heterogeneity, making them susceptible to gas channeling during gas flooding. Although water-alternating-gas (WAG) injection can suppress gas channeling, its overall development performance still requires further improvement. Through core displacement experiments combined with nuclear magnetic resonance scanning, the oil recovery and CO2 storage efficiencies of water flooding, CO2 flooding, WAG, and carbonated water-alternating-CO2 (CWAG) flooding were compared, thereby evaluating the feasibility of CWAG for improving oil recovery and achieving CO2 storage. Furthermore, reservoir numerical simulation was employed to analyze the effects of injection rate, water-gas ratio, and slug size on these outcomes. The results indicate that: (1) The oil recovery of 74.62% was achieved with CWAG, surpassing those of CO2 flooding and WAG by 8.40% and 3.83%, respectively; the recoveries for macropores, mesopores, and micropores were 85.34%, 65.54%, and 44.06%, respectively. (2) The CO2 storage efficiency of 51.02% was attained with CWAG, which is higher than that of CO2 flooding however slightly lower than that of WAG. (3) Within the studied parameter range, an increase in injection rate led to higher cumulative injection volumes and improved oil recovery but reduced CO2 storage efficiency; excessively high or low water-gas ratios were found to be detrimental to oil recovery, whereas a higher water-gas ratio favored CO2 storage; reducing slug size was shown to enhance both oil recovery and CO2 sto-rage efficiency. These findings demonstrate that CWAG can enhance oil recovery in low-permeability reservoirs while achieving CO2 storage, rendering it a promising and viable development method.

     

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