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It is frequently necessary to measure the viscosity of polymer solutions at high shear rates to obtain data under the conditions encountered in industrial processes. Such measurements are most often made on a capillary viscometer. This paper presents a method of determining solution viscosities at shear rates up to 50,000 s-' in a rotational rheometer using a parallel plate geometry. The two keys to performing these measurements are very small gaps between the parallel plates (on the order of 50 microns) to eliminate inertial secondary flows, and the ability to increase and decrease the shear rate quickly to minimize viscous heating. A technique for setting and measuring small gaps is presented. Possible sources of error including inertia, axial compliance, and viscous heating are analyzed. A comparison is made between the viscosity of a 0.7 percent hydroxypropyl guar (HPG) solution measured on the parallel plate rheometer and the viscosity measured in a capillary viscometer. Viscosities of HPG solutions having concentrations of 0.25, 0.50, 1.00, and 1.45 percent are presented over the shear rate range 100 to 50,000 s-'.

Water-soluble polymers crosslinked with metal ions form stable gels that are used in oil and gas production processes. We present an investigation of the chemistry of the binding between guar galactomannans and both borates and titanates using NMR and dynamic light scattering. The two monosaccharides comprising guar -methyl-/?-Dgalactopyranoside and methyl-r -have been studied as model compounds. High resolution 13C NMR detected complexation of the sugars with borate but displayed no sign of complexation with either of the two titanates even at high titanate concentrations. Dynamic light scattering studies demonstrated the existence of colloidal titanium dioxide particles for both titanate crosslinkers. The loss of free titanium to the colloidal particles reduces the concentration of titanium crosslinking sites to below the detectable limits of NMR. The role of colloidal titanium dioxide colloids in these crosslinking reactions has not been reported previously. Data are presented following the growth of these particles with time as a function of pH and salt concentration. The observed particle growth kinetics explains the observed sensitivity of the guar gelafion process to these variables.

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