摘 要:工程上将多孔介质的渗透率小于50毫达西的油藏,称为低渗透油藏。长期以来,由于存在启动压力,低渗透油藏的渗流特征很难描述,至尽还没有理想的模型。本文考虑液体和固体壁面的相互吸引的性质,从微管的负滑移边界模型出发,定义固壁边界附近不流动流体的流体层为边界黏附层,采用边界黏附层与压力梯度成反比的实验经验公式,推导出了考虑边界负滑移条件下,圆管中的流速分布公式和流量公式。进而得到考虑边界黏附层的低渗透渗流模型。最后以微管和低渗透岩心的流动实验对模型进行了验证,拟合出了相应的启动压力梯度。分析表明:新的模型具有物理含义清晰,易于应用的特点,可广泛用于低渗透油藏的理论分析和开发设计中。Abstract: In the petroleum development engineering, the low permeability reservoir is that the permeability of porous media is lower than 50 micro-Darcy. Because of the existence of the threshold pressure gradient (TPG), the mathemati- cal model of liquid flow in low permeability media is difficult to describe this kind of flow. Until now there is not an ideal model, although there are several models used to fields of well testing analysis and petroleum numerical simula- tions. Based on the force between liquid and surface solid, and the negative slip boundary model of a micro-channel, a new liquid flow model was derived for low permeability reservoirs in this paper. First defined the no movement liquid layer close to the solid surface as the boundary stick layer which regarded as the negative slip length, and used the in- verse proportion of the height of the boundary stick layer to the pressure drop gradient, the formulae of liquid velocity and the flow rate of a round channel were derived; Then the model of liquid flows in low permeability reservoirs was gotten based on the capillaries model; Finally the flow models were tested by examples and shown how to get the TPG of a low permeability reservoir. The results show that the new model has a clear physical definition, and can be easily used to describe liquid flows in low permeability media.
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