SIMULATIONS OF MIGRATION, FRAGMENTATION AND COALESCENCE OF NONWETTINGFLUIDS IN POROUS-MEDIA

A model based on invasion percolation was used to simulate the migrati on of a non-wetting fluid through a porous medium filled with an immis cible wetting fluid under the influence of a gradient such as that pro vided by gravity. The migrating fluid clusters undergo both fragmentat ion and coalescence. The fragment size distribution obtained from two- dimensional simulations in which the gradient g is slowly increased fr om 0 can be represented by the scaling form N(s)(g) approximately s-2f (s/\g\-z) where z = 1 + (D - 1)nu/(nu + 1). Here D is the fractal dime nsionality of invasion percolation, with trapping, and nu is the ordin ary percolation correlation length exponent.