Chemical composition, particle size, and molecular weight distributions of chemically degraded guar gum solutions

Chemical degradation of guar gum solutions via the addition of a strong oxidant is a common process step in hydraulic fracturing. Unfortunately, this degradation step leads to the formation of an insoluble precipitate which clogs the porous rock formation, reducing efficiency, reducing oil recovery potential, and increasing energy costs. The chemical composition, particle size, and molecular weight distributions of the oxidatively degraded guar ("broken guar") are largely unknown, making it difficult to develop mitigation strategies. In this work, broken guar gum solutions are systematically analyzed to understand the origin of the observed residue. Our results indicate that cellulose fibers and proteins, rather than galactomannan oligomers, are the two major components (>50%) of the solid residue (the water-insoluble fraction of broken guar). This finding suggests that removal of the cellulose fiber and proteins from the guar source material may be a potential residue mitigation strategy. Separately, we provide evidence for a potential second mitigation strategy employing chemical additives to reduce aggregation of the insoluble species, effectively reducing their potential to cause formation damage.