采油速度对不同黏度均质油藏水驱特征的影响

Effects of oil recovery rate on water-flooding of homogeneous reservoirs of different oil viscosity

基于均质油藏水驱油物理模拟实验,研究不同黏度均质油藏在不同采油速度下的水驱特征。低黏度油藏（黏度小于5 m Pa·s）水驱波及均匀,流线粗。随采油速度的提高,注水沿油层底部突进减弱,纵向波及更均匀,油层顶、底面波及系数差异减小。低黏度油藏高速开发无水期采出程度明显高于低速开发,含水上升速度低于低速开发,适宜高速开发模式。中高黏度油藏（黏度5~50 m Pa·s）水驱过程中注入水表现出明显的指进现象,水驱流线细,水驱波及不完全,流线间波及程度弱,油层顶、底面波及系数差异大。随采油速度的提高,中高黏度油藏水驱流线更细,波及更不完全,油层顶、底面波及系数明显降低。中高黏度油藏高速开发见水时间短,无水期采出程度明显低于低速开发,含水上升速度高于低速开发,不适合高速开发。

Based on physical simulation of water-flooding homogeneous reservoirs, the water-flooding characteristics of homogeneous reservoirs with different oil viscosity are examined at different oil recovery rate. Reservoirs with low-viscosity （〈5 mPa.s） oil can be evenly swept, with thick streamline. With increasing oil recovery rate, water rush weakens along the reservoir bottom and sweeps the reservoir more evenly in the vertical direction; and the sweep efficiency difference between top and bottom of the reservoir decreases. In high-rate development of the low-viscosity oil reservoir, the water-free recovery percent is significantly higher than that in low-rate development, and the rising velocity of water cut is lower than that under low-rate development, which proved that such reservoirs are suitable for high-recovery-rate development. For reservoirs with medium-high viscosity （5-50 mPa·s） oil, the injected water fingers significantly in the water-flooding process, with thin streamline, the coverage is not swept completely, especially in area between streamlines, the sweep efficiency difference between top and bottom is great. As the oil recovery rate increases, the streamline becomes thinner, the coverage becomes more incomplete, and the sweep efficiency of top and bottom both decreases. Medium to high-viscosity oil reservoirs developed at high rate have a short water breakthrough time, and the recovery percent in the water-free period is much lower than that in low rate development, and the rising velocity of water cut is higher than that under low-rate development, so high-rate development is not adaptable for medium-high viscosity reservoirs.