注水压力对低渗透储层渗流特征的影响

低渗透油藏中流体的渗流规律是当前渗流力学重要的研究领域。低渗透油藏储层的主要特征是渗透率低,油水流动的孔道微细,渗流阻力大,固-液界面及液-液界面之间相互作用显著。这些特点造成了低渗透油藏渗流规律的复杂性。通过室内岩心流动实验,研究了注入压力对岩石渗透率和流体渗流规律的影响。结果表明,低渗透储集层存在非线性渗流特征,当注入压力较低时,流体在岩心中流动速度随压力梯度的变化很小,也就是在低压下,注入水很难进入地层;当压力梯度较大时,渗流速度与压力梯度的关系呈近似的直线关系;在上覆压力和压力梯度不变的条件下,注入压力越高,岩石渗透率就越高。由此可见,在考虑储层保护的前提下,对低渗透储层采用高压注水,有利于提高注水效果。

The influence of water injection pressure on percolation of low permeability reservoirs

The percolation rule of fluids in low-permeability reservoirs is the important research field for seepage mechanics.Low permeability reservoirs are characterized by low permeability,fine pore for the oil and water flowing,high filtrational resistance and significant interactions between the solid-liquid interface and liquid-liquid interface,which results in the complexity of the percolation rule.Based on the core flow test,the effects of injection pressure on rock permeability and percolation rules of liquids are analyzed.The result shows that low permeability reservoirs have the characteristic of non-linear fluid flow through porous medium.The fluid flow speed in the core changes very little with the pressure gradient when the injection pressure is relatively low.It means that the injected water is difficult to enter the formation.When the pressure gradient is larger,there exists an approximate linear relation between flowspeed and pressure gradient.Under the condition ofinvariant overlyingpressure and pressure gradient,the higher the injected pressure gets,the higher the permeability of rocks is.It shows that high pressure water injection will enhance the water injection efficiencyunder the precondition ofthe reservoir formation protection.