Experimental and theoretical study of the rheological properties of non-newtonian media (solutions of viscoelastic surfactants) under quasi-static and dynamic loading

Abstract

The object of the study are liquids based on a viscoelastic surfactant brand D (type 70-100, produced by JSC «Polyex») and based on guar. These fluids are used for hydraulic fracturing technology as a propant-carrying and propant-retaining fluid for hydraulic fracturing in order to increase oil recovery, including hard-to-recover oil and gas reserves. The work is devoted to the development of a rheological model for the behavior of viscoelastic fluids in a wide range of shear rates typical for hydraulic fracturing. An urgent scientific problem is the substantiation of the choice of concentration of viscoelastic surfactant in the manufacture of fracturing fluid. In domestic practice, it is customary to use a fracturing fluid with an effective viscosity of 0,4 Pa·s (=400 cP) at a strain rate of 100 s-1 and a temperature equal to the arithmetic mean between the formation and wellhead temperatures. In foreign literature, the elastic component of the fracturing fluid is increasingly mentioned as the most adequate characteristic that correlates with the propant-retaining capacity of the fluid (non-viscous component). At present, models of the behavior of propantone-bearing viscoelastic fluids (viscoelastic surfactant solutions) in the processes of hydraulic fracturing are in demand. In this regard, there is a need to develop mathematical models and methods for calculating the propant- retaining capacity of a fracturing fluid depending on its viscoelastic characteristics. The aim of the work was to develop a mathematical model for the behavior of viscoelastic surfactant solutions, to develop approaches and methods for identifying the parameters of the Leonov-Prokunin model, which makes it possible to adequately describe both the process of a stationary fluid flow and dynamic loading in the oscillation mode and shock wave loading. The result of the project is the method for identifying the parameters of the behavior model of viscoelastic surfactant solutions according to static and dynamic tests, which can be used in commercial hydraulic fracturing solvers.