COLLOID MIGRATION IN SYMMETRICAL NONUNIFORM FRACTURES - PARTICLE TRACKING IN 3 DIMENSIONS

A three-dimensional model for the migration of colloids in a saturated fracture is presented, which considers the motion of colloids as a re sult of advection and diffusion, as well as colloid-surface interactio ns at the fracture walls. This model is successfully incorporated into a three-dimensional particle tracking algorithm that tracks particles within a continuum and allows consideration of the migration of collo ids in symmetrical, three-dimensional, non-uniform fractures. The fram ework is general enough to incorporate non-local interactions that pro vide colloid motion relative to the fluid. The algorithm is verified a gainst classical Taylor dispersion, and its generalization to a sorbin g phase, in a uniform fracture and shows excellent agreement with theo ry. A simple, non-uniform fracture that has an analytically tractable velocity field is also considered, and both quantitative and qualitati ve comparisons are made with the uniform fracture case. The modelling of more complex fracture geometries is also discussed and a particular case is implemented within the particle tracking framework. (C) 1997 Published by Elsevier Science B.V.