水驱后聚合物驱全过程的相对渗透率曲线研究

Experiments Research of Full Term Polymer Flooding and Their Relative Permeability Curve

针对油田开发时水驱至一定含水率后聚合物驱的实际情况,选用大庆油田有代表性的葡Ⅰ组与萨Ⅱ组的天然岩心平行样,水测渗透率分别约1.0、0.6、0.2μm2,采用恒速非稳态法分别测定了水驱至含水率90%9、4%、98%时转注聚合物溶液及后续水驱全过程的相对渗透率曲线。实验结果表明:水驱与聚合物驱全过程的相渗曲线形态与单一聚合物驱相比发生了明显变化,注聚合物后的油相相对渗透率先增加后降低,而驱替相渗透率则先降低后增加;同等渗透率级别时,转注聚合物越早,其相渗曲线两相区跨度越大,残余油饱和度越低;转注聚合物时机相同时,岩心渗透率越高,油相相对渗透率下降越缓慢,对应水相相对渗透率上升越缓慢,使两相区增大,残余油饱和度降低。

Considering the actual situation which polymer solution was injected when the water cut of water flooding was up to a certain degree during the development of oilfields,three kinds of representative parallel natural core samples were selected from PⅠand SⅡ reservoirs in Daqing oilfield,which water permeability were about 0.2,0.6,1.0 μm^2 respectively,and the unsteady-state method of constant injection rate was adopted to measure the relative permeability curves of the whole process of water flooding up to water cut 90%,94%,98%,then polymer flooding,sequent water flooding.The results showed that shape of the relative permeability curves of the whole process changed significantly,which compared with the pure polymer flooding＇s.The relative permeability of oil-phase increased after polymer injection and then decreased,meanwhile that of displacing phase decreased first and then went up.With the same permeability level,the earlier transfered to polymer flooding,the larger the span of two-phase region in relative permeability curves was,and the lower the residual oil saturation was.With the same transfer time,the higher the core permeability was,the slower the oil-phase relative permeability decreased,and the slower the corresponding water-phase relative permeability increased,which would lead to the increase of two-phase region and the decline of the residual oil saturation.