油气成藏条件下低渗透砂岩石油运移的渗流特征实验研究

An Experimental Study on Flow Characteristics of Oil Migration in Low-permeability Sandstone under Condition of Oil Accumulation

在室内低速渗流实验的基础上,采用恒压测试法,对成藏条件下石油在低渗透砂岩中的运移渗流规律及影响因素进行了研究。结果表明:(1)石油在低渗透砂岩中低速渗流时存在着启动压力梯度,非达西渗流特征明显。(2)低渗透砂岩中石油非达西渗流曲线主要有两种基本类型,视流度≤1时,非达西渗流曲线表现为上凹型曲线;视流度>1时,表现为变性达西流曲线。(3)低渗透砂岩的物性、石油性质以及它们的相互作用对渗流曲线的位置、非线性段的曲率和变化范围以及直线段在压力梯度轴的截距具有重要影响。(4)随着低渗透砂岩渗透率的降低和石油粘度的增加或视流度的减小,石油在低渗透砂岩储层的非达西渗流特征更加明显。

Based on lab results of low-rate flow,the flow rule of oil migration and its influential factors in low-permeability sandstone under condition of oil accumulation were studied in this paper using constant-pressure test.The results show that： there exists threshold pressure gradient,and the non-Darcy flow is very obvious as oil flows in low-permeability sandstone at a low rate;and there are two basic non-Darcy flow curves according to apparent fluidity,that is,when apparent fluidity is less than or equal to 1,it appears as upward（up-concave） curve and more than 1,appears as metamorphic non-Darcy flow curve.The physical property of low-permeability sandstone,oil property and their combined effect have great influence on the intercept of pressure gradient axis for the location of flow curve,the curvature and range of non-linear segment and line segment.With decrease of permeability in low-permeability sandstone and increase of oil viscosity or decrease of apparent fluidity,non-Darcy flow of oil is more obvious in low-permeability sandstone reservoir.