中文摘要：

为分析特低渗透砂岩的水驱油特征，揭示影响水驱油效果的主要因素，利用核磁共振技术对鄂尔多斯盆地延长组样品进行了水驱油前后的T2谱测试。结果表明，实验样品束缚水状态下的油相T2谱呈双峰形态，两峰之间的交点在16．68ms左右，可动油参数对渗透率变化敏感；水驱油后T2谱右峰下降程度不同，左峰的下降与毛细管的自吸作用有关，发挥好毛细管的自吸作用，有助于提高采收率。38块样品的平均可动油百分数达到了57．62％，驱油效率为37．33％，还有约20．29％的可动油没有被驱出，水驱油后的开发潜力仍然较大。物性、孔喉匹配关系、微裂缝发育程度、粘土矿物赋存形态是影响驱油效率的主要因素。驱油效率与可动油百分数之间的对比结果从实验角度印证了核磁共振可动油百分数是驱油效率的上限。

英文摘要：

Samples of Yanchang group in Ordos Basin were tested using the NMR technique before and after the water-looding experiments in order to analyze the characteristics of water displacing oil and to reveal the dominant factors for extra-low permeable sandstones. The results show that oil phase T2 patterns present double peaks in an irreducible water condition with crossing points at about 16.68 ms and movable oil parameters are sensitive to permeability. The right peak decreases to different extents after water-flooding; while the drop of left peak is related to the imbibition of capillary. If the imbibition of capillary can be utilized effectively, recovery can be enhanced. Average value of movable oil percentage is 57.62 and displacement efficiency is 37.33. There is about 20.29% movable oil that has not been flooded out and the development potential is still great after water displacing oil for extra-low permeable sandstones. Physical property, matching relationship of pore throat, degrees of microcrack development, occurrence forms of clay mineral are the main factors affecting displacement efficiency. Correlation between displacement efficiency and movable oil percentage confirms that movable oil percentage of NMR is the upper limit of displacement efficiency.