  In this paper we analyse a problem of a hydraulic fracture driven by a
non-Newtonian shear-thinning fluid. For the PKN fracture geometry we consider
three different rheological models of fluid: i) the Carreau fluid, ii) the
truncated power-law fluid, iii) the power-law fluid. For each of these models a
number of simulations are performed. The results are post-processed and
compared with each other in order to find decisive factors for
similarities/dissimilarities. It is shown that under certain conditions even
the basic power-law rheology can be a good substitute for the Carreau
characteristics. Although for a particular fluid such a conclusion cannot be
made a priori, post-processing based on average values of the fluid shear rates
is a very good tool to verify credibility of the results obtained for
simplified rheological models. The truncated power-law rheology is a good
alternative for the Carreau model. It always produces results that are very
similar to those obtained with the equivalent Carreau fluid and simultaneously
provides a relative ease of numerical implementation.
