低渗透油藏聚合物驱启动压力梯度的表征

Characterization of Start-up Pressure Gradient of Polymer Flooding in Low Permeability Reservoir

为研究低渗透油藏聚合物驱启动压力梯度对渗流规律的影响,通过稳态压差-流量法和毛细管平衡法,研究了水驱油至残余油状态时岩心渗透率和聚合物溶液黏度对聚合物驱渗流曲线的影响,建立最小启动压力梯度、拟启动压力梯度与体系黏度、岩心渗透率和流度的量化关系。结果表明,在相同渗流速度下,随着岩心渗透率降低、体系黏度增加,聚合物驱压力梯度增大;随着体系黏度增加、岩心渗透率或流度降低,聚合物驱的最小启动压力梯度和拟启动压力梯度均增大,且都大于相同条件下的水驱启动压力梯度值;拟启动压力梯度与流度关系曲线的拐点为17.89×10^(-3)μm^2/m Pa·s,低渗透油藏进行聚合物驱的渗透率下限为10×10^(-3)μm^2。水驱拟启动压力梯度方法可以用于表征聚合物驱渗流曲线的拟启动压力梯度。

In order to study the influence of start-up pressure gradient on the percolation law of polymer flooding in low permeability reservoir,laboratory experiments were conducted with the combined method of differential pressure-flow and capillary equilibrium. Under the condition of residual oil saturation with water driving,the effects of core permeability and polymer viscosity on polymer flow curves were studied. Quantitative relations between minimum or quasi start-up pressure gradient and viscosity,core permeability or mobility were established. The results showed that displacement pressure gradient increased with increasing polymer viscosity and decreasing core permeability under the same seepage velocity. And with the increase of viscosity or the decrease of permeability and mobility,the minimum or quasi start-up pressure gradients of polymer flooding increased,which were greater than the start-up pressure gradient values of water flooding under same conditions. The inflection point was 17.89×10^（-3）μm2/m Pa·s in the relation curve of quasi start-up pressure gradient and mobility,and the lower limit of permeability was 10×10^（-3）μm2with polymer flooding in low permeable reservoir. The method used for water flooding quasi start-up pressure gradient could be used to characterize the quasi start-up pressure gradient of polymer flooding flow curve.