Paper: The use Of A Low-Concentration Crosslinked Hydroxyalkyl Polymer System As A Highly Efficient Fracturing Fluid

The necessity of developing cleaner fluids for the purpose of well stimulation has been the topic of current discussion among oil company and service company personnel alike. In fracturing, the incorporation of specific quantities and types of gelling agents and fluid-loss additives has been considered only as means by which to obtain effective viscosities for proppant transport, fracture width development, and efficiency via low leak-off of fluid away from the direction of fracture penetration. Since it has been established by several investigators19 2 that fluid-loss additives and natural agent gelling compounds may contribute significantly to formation damage, a need for a clean fluid encompassing the properties of effective viscosity, low fluid-loss, efficiency and comparable economics is evident. This will be shown in tabular and application history forms. One solution to the problem is to utilize a highly efficient ultra-low residue, chemically substituted, natural polymer at low concentrations, and employ the principle of cross-linking to allow actual link-up of the molecules to provide several folds of viscosity increase over that obtainable by the low concentration base gel; and via the process of interlocking or connecting molecules of guar polymer, create an excellent fluid-loss control mechanism such that little or no additional fluid-loss additive is required?, 4 This system may be batch-mixed into frac tanks unlike the predecessor high concentration cross-linked gels. The guar used is of a relatively new type, being a highly refined (0.5% residue) chemically substituted hydroxyalkyl-type. This product's molecular structure is compared to the conventionally used guar molecule in Fig. 1. When cross-linked at a concentration of 15 lb/1000 gal. aqueous phased fluid, the individual hydroxyalkyl molecule, as shown in Fig. 2, is cross-linked by bonding, as shown in Fig. 33. It may be stated that the use of the abovementioned hydroxyalkyl polymer in the cross-linked state at relatively low concentrations compared to conventional oil or water-based fracturing systems is a comparably efficient or more efficient, more effective fracturing system. The evidence for showing the low-residue hydroxyalkyl cross-linked guar system to be comparable, or better, than conventionally designed gels containing between 20 lb and 60 lb gelling agent in addition to 20-40 lb of fluid-loss control material is borne out by viscosity, fluid loss, friction loss, fluid efficiency, and cost evaluation testing. See Table 1.