Static Proppant-Settling Characteristics of Non-Newtonian Fracturing Fluids in a Large-Scale Test Model

Large-scale testing of the settling behavior of propants in fracturing fluids was conducted with a slot configuration to model realistically the conditions observed in a hydraulic fracture. The test apparatus consists of a 1/2{times}8-in. (1.3{times}20.3-cm) rectangular slot 141/2 ft (4.4m) high, faced with Plexiglas and equipped with pressure taps at 1-ft (1.3m) intervals. This configuration allows both qualitive visual observations and quantitative density measurements for calculation of proppant concentrations and settling velocities. In this paper, the authors examine uncrosslinked hydroxypropyl guar (HPG) and hydroxyethylcellulose (HEC) fluids, as well as crosslinked guar, HPG, and carboxymethyl HPG (CMHPG) systems. Sand loadings of 2 to 15 lbm/gal (240 to 1797 kg/m{sup 3}) (3 to 40 vol% of solids) were tested. Experimental results were compared with the predictions of existing particle-settling models for a 40-lbm/1,000-gal (4.8-kg/m{sub 3}) HPG fluid system.