Abstract:

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.

Key words: low permeability reservoir, forming process, non-Darcy flow, simulated experiment