致密油储层水驱油核磁共振实验研究

NMR experimental study of water displacing oil of tight oil reservoir

针对鄂尔多斯盆地有代表性致密油储层岩心,将核磁共振技术与水驱油物模实验相结合,对储层初始状态油相赋存特征及水驱油后微观剩余油分布特征进行研究。研究表明：水驱油前,渗透率〉0.3×10^-3μm^2储层粒间孔内（大、中等孔隙）油赋存量多于黏土微孔,渗透率〈0.1×10^-3μm^2储层大孔隙很少,油主要赋存于黏土微孔及中等孔隙内。水驱油后,4个渗透率级别（〉1×10^-3,0.3-1×10^-3,0.1-0.3×10^-3和小于0.1×10^-3μm^2）储层大孔隙采出程度R均很高,分别为77.35%,73.75%,75.70%和60.66%,剩余油饱和度Sorm均很低,分别为3.10%,4.71%,0.81%和0.50%,大孔隙内很少或无剩余油;中等孔隙R较高,分别为64.32%,53.52%,73.34%和82.68%,Sorm较低,分别为10.30%,13.89%,7.95%和5.05%;渗透率越低,该类孔隙R越高,Sorm越低;黏土微孔R均很低,分别为14.32%,17.09%,19.79%和22.61%,Sorm均很高,分别为27.99%,20.94%,29.18%和31.15%,表明剩余油主要分布在黏土微孔内。不同区块层位比较,Ⅰ层好于Ⅱ层,AⅠ储层最好。

Representative tight oil reservoir cores of Erdos basin was studied combined NMR technology and core displacement test, and analysis microscopic oil distribution characteristics both initial state and after water flooding of reservoir. The results show that： Before water flooding, while permeability is greater than 0.3×10^-3 μm^2, oil exist in intergranular pores（large, medium pores） more than clay micropores, and while permeability is less than 0.1×10^-3 μm^2, few macropores exist in reservoir and oil mainly exist in clay micropores and medium pores. After water flooding, four permeability level（greater than 1×10^-3, 0.3-1×10^-3, 0.1-0.3×10^-3 μm^2 and less than 0.1×10^-3 μm^2） reservoir recovery percent of reserves R of large pores are very high（77.35%, 73.75%, 75.70% and 60.66%, respectively）, remaining oil saturation Sorm are very low（3.10%, 4.71%, 0.81% and 0.50%, respectively）,few or no remaining oil in macropores. R of medium pores are high（64.32%, 53.52%, 73.34% and 82.68%, respectively）, Sorm are low（10.30%, 13.89%, 7.95% and 5.05%, respectively）, the lower permeability reservoir have, the higher R and the lower Sorm reservoir get in this pores. R of clay micropore are very low（14.32%, 17.09%, 19.79% and 22.61%, respectively）, Sorm are high（27.99%, 20.94%, 29.18% and 31.15%, respectively）, show that remaining oil mainly distributes in clay micropores. Comparison of different blocks and layers, layer Ⅰ is better than Ⅱ, and AⅠ reservoir is best.