BAND FORMATION IN DEPOSITION OF FINES POROUS-MEDIA

We propose that there are two classes of temporal development in the d egradation of permeability of porous media due to deposition of fines: (1) Deposition, and therefore permeability degradation, is localized to bands growing orthogonally to the average local flow direction, and (2) permeability degradation occurs in stripes parallel to the local flow direction. These latter stripes do not influence total permeabili ty much as they develop. When these stripes are allowed to develop, th ey coalesce and worm holes form. We discuss how imposing different flo w conditions such as constant flow and constant pressure influence the deposition process. Our conclusion is that constant pressure conditio ns typically lead to a slower permeability degradation compared to con stant flow conditions as a direct consequence of the formation of low- permeability bands. We test our ideas by numerical simulations on a si mple model for fines migration and deposition in porous media.