Characterization of Breaker Efficiency Based Upon Size Distribution of Polymeric Fragments Resulting from Degradation of Crosslinked Fracturing Fluids

Fluid viscosity reduction is commonly used to gauge polymer degradation. Although viscosity reduction indicates polymer degradation, it is misleading to conclude that this reduced viscosity equates to improved fracture conductivity. Polymer fragments which are desolubilized from the gelled fluid no longer contribute to fluid viscosity but do, unfortunately, contribute significantly to proppant pack damage. A recent study disclosed laboratory procedures to characterize the efficiency of get breakers based upon the Size distribution of the generated polymeric fragments. The study focused on 8-week evaluations of the effects of various breakers on linear, guar-based fracturing fluids from room temperature to 210°F. The studies indicated that enzyme breakers continued to degrade the polymeric molecular weight for at least eight weeks. The molecular weight reduction attributed to the enzyme breakers outperformed oxidative breakers at all conditions evaluated. This study discloses the results of similar efforts conducted to characterize the efficiency of breakers applied in crosslinked fracturing fluids. The data yield a quantitative profile of the polymeric fragments as well as a measure of the relative degrading efficiencies of the various oxidative and enzymatic breakers. The studies were conducted with borate-crosslinked guar, zirconium- crosslinked guar, and zirconate-crosslinked CMHPG. Detailed analyses of the data are provided.