Novel associative acrylamide-based polymers for proppant transport in hydraulic fracturing fluids

Abstract

The properties of novel polymers for proppant transport in hydraulic fracturing operations are discussed. Acrylamide based associative polymers have been synthesized using various industrial production processes. Anionic polymers investigated are acrylamide (AMD) based co- and ter-polymers functionalized with monomers such as sodium acrylate (AA), sodium acrylamido-tertiary-butyl sulfonate (ATBS) and a home-made surfactant monomer. The rheological properties of the developed polymers in different brines are evaluated and compared to commercial guar gums usually used for fracturing fluids. The viscoelastic properties as well as settling time of proppant in graduated cylinder have been evaluated. The impact of oxidizing breakers and surfactants added to increase or decrease the viscosity of solutions are reported as well. The new polymers can be used in slickwater, linear gel and cross-linked hydraulic fracturing fluid. They have the ability to carry the proppant down to the target zone. With this technology, proppant can be transported and placed into the fractures with lower concentrations of product and reduce or eliminate the need for using guar gum. Fluid viscosity can be controlled (either increased or decreased) by the addition of surfactants and broken by conventional oxidizers. Laboratory data shows that new associative polymers solutions give very high viscosity at low shear rate and a strong reversible shear thinning effect. Typically, for 3000 ppm of associative polymer, settling time of proppant is 10 times longer than for the same concentration of guar gum. In gel-based fracturing jobs, transport of proppant is generally achieved using guar gum whose viscosity may be improved by adding cross-linkers such as borate or zirconium. The polymer presented in this paper could be a total or partial alternative to guar for proppant transport whose price is subjected to harvest aleas. Results show that lower polymer concentrations are required to obtain the same or even better suspending properties. Besides, traditional oxidizing breakers could be replaced by surfactant to decrease the viscosity of the fluid once the proppant has been placed in the fractures. Copyright 2013, Society of Petroleum Engineers.