A visual experimental study on proppants transport in rough vertical fractures

The roughness of fractures may play an important role in affecting the migration and placement of proppants during hydraulic fracturing operations. A series of proppant flow experiments were conducted in attempt to compare the proppant transport mechanisms in rough fractures against those in smooth fractures. We examine the migration of proppants in rough and vertical fractures and then quantitatively reveal the effect of roughness on the instantaneous proppants transport and final proppants placement. The proppants-transport behavior in the rough and vertical fractures was observed to be totally different from that in the smooth and vertical fractures. The proppants in a rough vertical fracture do not progress like the regular sand bank that commonly occurs in the smooth fracture, but rather as an irregular-shape sand cluster with fractal characteristics. In the rough and vertical fracture, the phenomenon of proppants bridging is visually observed. The roughness of the fracture model not only affects how much of the fracture area is being occupied by the proppants, but also affects how tightly the proppants fill up the fracture.