不同驱替方式下岩石电阻率与饱和度的关系

The Relationship Between Rock Resistivity and Water Saturation in Water-Drive-Oil and Oil-Drive-Water Process

针对高含水期老区调整井饱和度评价过程中存在的问题,通过模拟油田开发过程的岩石物理实验,研究水驱油方式下电阻率与含水饱和度之间的关系。与油驱水不同,水驱油方式下电阻增大率与含水饱和度在双对数坐标系中的关系不再是一条直线,而呈现出明显的与高、低含水饱和度区间相关的两段式;岩石的润湿特征不同,两段式拐点所对应的含水饱和度Swp不同,水驱方式下所能达到的最终采收率也不同。水驱油方式下的I-Sw曲线特征表明,用勘探阶段及开发初期油驱水实验得到的饱和度公式对开发中后期的饱和度进行评价不太合适,尤其是在高含水期,电阻率对高含水饱和度反映能力的局限性严重制约了这一阶段水淹层的评价精度。

Aiming at problems existed in saturation evaluation of regulative wells in high water cut stage, the authors studied the relationship between resistivity （I） and water saturation （Sw） in water- drive-oil process through rock physics experiment for simulation of the oilfield development. It is a contradiction to the oil-drive-water approach, relation between resistivity and water saturation in dual-logarithm coordinates system in water-drive-oil process appears a non-linear pattern, which shows an obvious two sections that corresponds respectively to high and low zones of water saturation. Saturation （Swp） related to the two-section inflexion varies as wetness alters, therefore the final oil recovery also varies in water-drive approach. Characteristics of I-Sw curve under water-drive-oil process show that resistivity curve can not reflect the water saturation exactly in high water cut stage of oilfield development. Thus it is unsuitable to evaluate water saturation in middle and later development stages using model derived from oil-water-drive experiment in exploration stage and early development stage. It is especially inappropriate in the high water-cut stage, in which resistivity represents poorly water saturation so that the evaluation accuracy is severely limited.