IMMISCIBLE DISPLACEMENT OF VISCOSITY-MATCHED FLUIDS IN 2-DIMENSIONAL POROUS-MEDIA

The effect of stabilization has been investigated experimentally when a nonwetting fluid is displacing a wetting fluid with the same viscosi ty in a two-dimensional porous medium. Experiments were done at differ ent injection rates, with capillary numbers ranging from 10(-7) to 10( -4). The features of the front between the liquids were analyzed and f ound similar to those observed from invasion percolation models includ ing a spatial gradient in the average pore threshold value, and gravit ationally stabilized experiments. Front and structure of the trapped c lusters of the invaded fluid at different capillary numbers are self-s imilar with the fractal dimensions D-b = 1.33 and D-b(m)=1.85, respect ively. The dependence of the front width w(s) on the capillary C-a was found to be consistent with a power law w(s) similar to C-a(-alpha), with alpha=0.6. The dynamic exponent beta(d) approximate to 0.8 descri bing front width evolution as a function of time was determined by col lapsing the density-density correlation function data. An analytical a rgument is presented to support the stabilization of the front owing t o the viscous effects.