低渗透砂岩储层不同驱替方式开发规律研究

Study on Development Patterns of Different Displacement Methods in Low-Permeability Sandstone Reservoirs

摘要: 本文通过启动压力梯度实验和高温高压在线核磁共振驱替实验，系统研究了低渗透砂岩储层中不同介质(水驱、N₂驱、CO₂驱)的渗流特性及驱油效率。启动压力梯度实验基于压差–流量关系，揭示了驱替介质从液相到气相启动压力梯度逐渐降低的规律，并发现启动压力梯度与岩心孔隙渗透率呈负相关。高温高压在线核磁共振技术在模拟真实储层温压条件下，动态监测不同驱替介质在岩心内部的形态分布及渗流规律，揭示了驱替过程的微观作用机理。实验结果表明，三种驱替介质的驱油效率排序为：CO₂驱 > 水驱 > N₂驱，CO₂驱得益于其溶解性及降黏特性，表现出更优的驱油效果。

Abstract: This study systematically investigates the seepage characteristics and oil displacement efficiency of different displacement media (water, N₂, and CO₂) in low-permeability sandstone reservoirs through threshold pressure gradient experiments and high-temperature high-pressure online nuclear magnetic resonance (NMR) experiments. The threshold pressure gradient test, based on the pressure difference-flow rate relationship, reveals a trend of decreasing start-up pressure from liquid to gas displacement media, and a negative correlation between threshold pressure and reservoir permeability. High-temperature high-pressure NMR under simulated reservoir conditions captures the dynamic morphology and seepage behavior of displacement media in porous cores, elucidating the micro-scale mechanisms of oil recovery. The results indicate that the displacement efficiency follows the order: CO₂ > water > N₂, with CO₂ showing superior efficiency due to its solubility and viscosity reduction characteristics.