Cross-linked guar gels are the most widely used hydraulic fracturing fluids. The selection of a composition allows to obtain a fluid with desired properties most of them concerns fluid rheological behavior. The hydraulic fracturing fluid must have minimal friction losses during pipe flow, it must ensure the creation of a fracture with the required geometry, ensure the transport and distribution of proppant particles along the fracture, and finally, after completion of the hydraulic fracturing, the viscosity of the fluid must significantly decrease for effective fracture cleaning. At the same time, despite the fact that cross-linked gels are systems with well-developed three-dimensional inner structure, it is standard practice to use the simple power dependence to describe their rheological behavior that relates the shear stress with the shear rate.
The article presents the results of studying the rheology of hydraulic fracturing guar gels using the pipe rheometry method, as well as the results of visualization of flows in a rectangular slot channel. The results clearly show the thixotropic behaviour of cross-linked guar gels during the flow of in the range of shear rates typical for hydraulic fracturing. It has been reveald that the steady flow curves of cross-linked gels are nonmonotonic. Dependences of the rheological characteristics of gels on the shear history are obtained. Flow visualization shows that the flow structure of linear and cross-linked gels is qualitatively different. The results of the study indicate the imperfection of the standard rheological model of gels, which can lead to an incorrect result during hydraulic fracturing simulation.
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DOI: 10.2118/9334-PA
