Effect of Degradable Fiber Composition and Shape on Proppant Suspension

Abstract

The ability of degradable fibers to reduce the settling rate of ceramic proppant in a guar-based solution was studied as a function of fiber composition and shape. Various cellulose ester fibers were benchmarked against a PLA standard. Aqueous (2 wt% KCl in DI water) mixtures of degradable fiber, ceramic proppant, and guar were consistently mixed then allowed to settle. The position of the interface between the solids-rich bottom layer and solids-poor top layer was measured as a function of time for various fiber compositions, shapes, and loadings. Settling experiments were also repeated to determine measurement error. Viscosity measurements were performed both to determine appropriate guar loading and to investigate the effect of fibers on viscosity. Consistent with recent results published in the patent literature for PLA, fiber shape was found to have a strong effect on proppant suspension. However, these effects went well beyond those found for aspect ratio and degree of crimping reported previously. Indeed, fiber cross-sectional shape was found to have a very strong effect with "X" and trilobal shapes showing better proppant suspension capability than round fibers. Fiber loading with shaped fibers could be reduced up to half of that round fibers with the same proppant suspension performance. The degradable polymer composition may play some role in proppant suspension but it appears to be secondary relative to that of fiber shape. Degradable fibers with improved performance should enable broader consideration of their use for proppant transport, proppant suspension, and heterogeneous proppant placement in fiber-based hydraulic fracturing. Other stimulation applications may also value alternative degradable materials.