The Fractal Study Of The Non-Darcy Seepage Properties For Low Permeability Reservoir

With the development of petroleum industry in the world, the development of the low- permeability oil fields has received more and more attention. In order to develop these oil fields reasonably and efficiently, we should fully take into account the special seepage regulation and character parameters of these low permeability reservoirs.Applying the fractal geometry theory about porous media and starting with analyzing the seepage characteristics of low-permeability oil layer, this paper explores the one of physical mechanisms and seepage characters that there is the threshold pressure gradient in such reservoirs. The non-Darcy seepage mechanism at low velocity in porous media is analyzed based on the surface colloid chemistry theory and on the fractal distribution of capillary sizes. A fractal permeability model for non-Newtonian fluid flow in low permeability reservoirs is derived and compared to that for Newtonian fluid through porous media. The threshold pressure gradient for plastic fluid in low permeability porous media is also derived and is expressed as a function of yield stress, pore-area fractal dimension, tortuosity fractal dimension, and micro-structural parameters, and there is no empirical constant in the model and every parameter in the model has clear physical meaning.