A model of non-Newtonian slurry flow in a fracture

An accurate calculation of a non-Newtonian slurry flow in a fracture is an important issue for fracture design (see for example, the book edited by Economides and Nolte [M.J. Economides, K.J. Nolte, Reservoir Stimulation, Third edition, Schlumberger, 2000.]). A model taking into account micro-level particle dynamics is developed here. The model shows that the slurry dynamics is governed to a significant extent by particle fluctuations about mean streamlines in a high-shear-rate flow. Particles migrate from zones of high shear rate at the fracture walls towards the center of the fracture where shear rates are lower. Thus, slurry flow in a fracture is characterized by non-uniform solids concentration across the fracture width. Low solids concentration near the walls leads to a reduction of slurry-wall friction as compared with that predicted by a model that does not take particle migration into account. Reduction in the friction at the wall leads to a reduction in the streamwise pressure gradient and hence in the net pressure.