The Use of Laser Doppler Velocimetry (LDV) for the Measurement of Fracturing Fluid Flow in the FFCF Simulator

Abstract

Abstract Laser Doppler Velocimetry (LDV) is an optical point velocity measuring technique that has revolutionized velocity measurements in hostile flow environments. The high pressures and high temperatures encountered in hydraulic fracturing simulations at the Fracturing Fluid Characterization Facility (FFCF), coupled with the abrasive character of the proppant laden fracturing gels proposed for study, makes LDV the preferred technique for this application. This paper describes a unique nine probe LDV system that is applied to fluid flows in the FFCF simulator. The LDV system consists of nine specially designed laser probes, three power supplies, a unique signal processor/multiplexer, and a personal computer for system control and data display. In addition, three automated precision traversing stages are coupled to three of the laser probes for velocity profile studies. This system has been applied to both Newtonian and non-Newtonian fluids in the simulator at several crack widths and flow rates. Some point velocity data, along with extensive velocity profile data, is presented and discussed for several fluids. The fracturing fluid studies presented are for flows without proppant. The velocity profiles are compared to theoretical models that are applied with volumetric flow rates measured by an independent flowmeter. The results show that LDV is a valuable tool for gathering point velocity information from fracturing fluid flows in the FFCF simulator.