Suspension characteristics of borate-crosslinked gels: Rheology and atomic force microscopy measurements

Borate-crosslinked guar gels were prepared and characterized to understand their capability to suspend and transport sand particles through a fracture created in a petroleum reservoir. In this study the crosslinked gels were formulated by varying the borate crosslinker concentrations that were selected such that the gels satisfied the minimum viscosity criteria (100 cP at 100/s) used to evaluate crosslinked gels for their suspension capabilities. However, some of these gels did not exhibit satisfactory particles transport through a slot that models a parallel fracture. These gels were then characterized using oscillatory measurements and atomic force microscopy (AFM) to understand the influence of the microscopic behavior of the crosslinked gels on their macroscopic performance in the slot. The results showed that the suspension transport characteristics of these gels could be described through crosslinked networks formed across the guar polymer. The AFM images and rheological measurements of these gels suggest that the elastic modulus provides more useful information than the viscosity about the crosslinked gel structure and their capability to suspend sand particles. (C) 2001 John Wiley & Sons, Inc.