低渗透岩心中油水两相渗流启动压力梯度试验

低渗透储层的孔隙变尺度和微尺度效应使得其中流体流动更加复杂化,主要表现为非线性渗流特征和存在启动压力梯度。对胜利油田桩74断块东营组油层26块低渗透岩心进行室内渗流试验,分别测定了岩心油单相和油水两相的启动压力梯度,结果表明,在油单相渗流过程中,随着流度增大,启动压力梯度逐渐减小,当驱替流体流度增大到一定值后变化平稳,油层流度对启动压力梯度的大小影响非常显著;不同初始含水饱和度的两相最小启动压力梯度与流度均呈幂指数关系;随含水饱和度的增加,启动压力梯度逐渐减小。通过对油水混合流体黏度进行饱和度加权,建立了统一的启动压力梯度试验模型,模型适用于单相和油水两相流渗流,具有较好的自适应性。

Experiment on starting pressure gradient of oil and water two phases flow in low permeability core

The variable and micro effect of pore size make fluid flow more complex in low permeability reservoirs,which caused non-linear fluid flow and starting pressure gradient,laboratory experiments of low permeability core have been done on block 26 of Shengli Oilfield 74 block Dongying group,measured its starting pressure gradient of single phase and oil-water two phases flow,the experiment result showed that at single flow of oil,while the displacement fluid mobility reached to a special value,the starting pressure gradient decrease gradually and smoothly with increase of mobility,and the effect of mobility to starting pressure gradient is evident.At different initial water saturation of two phases flow,the starting pressure gradient and mobility increase with exponential function,and the starting pressure gradient decrease with the increase of water saturation.Weighted to saturation based on viscosity of mixed oil and water fluid,established unified experiment model of starting pressure gradient,which is suit for single and two phases flow,and has preferable self isolate.