Flow of non-Newtonian fluids in single fractures and fracture networks: Current status, challenges, and knowledge gaps

Abstract

Flow of non-Newtonian fluids in rock fractures is ubiquitous in engineering practice and involves e.g. cement flow in tunnel grouting, drilling fluid flow when a fracture is met during drilling, and flow of fracturing fluids in hydraulic fracturing. In this review article, basic information about rheological behavior of non-Newtonian fluids is provided in Section 1. In Section 2, a summary of equations for the flow of non-Newtonian fluids between smooth parallel plates is provided, and knowledge gaps are identified, including those in two-phase flow. In Section 3, non-Newtonian fluid flow in fracture networks is reviewed, and outstanding research tasks are identified. The article concludes with a summary of current challenges in Section 4. Amongst the main knowledge gaps and challenges identified in the review and relevant for engineering geological practice are fracture flow of thixotropic fluids; two-phase flow regimes and instabilities associated with it; flow of non-Newtonian fluids through (and their mixing with Newtonian fluids at) fracture intersections; efficient algorithms for network flow at arbitrary pressure gradients; leak-off of non-Newtonian fluids through fracture walls; modelling of non-Newtonian fluids that include environmental effects and the resulting multiple couplings and multiphysics.