Individual Seawater Ions’ Impact on the Rheology of Crosslinked Polymers in the Presence of a Chelating Agent

Seawater (SW) has the potential to replace freshwater in hydraulic fracturing operations, which promotes sustainability. In this study, we investigated the influence of SW ions individually on a crosslinked polymer solution containing a chelating agent. The tested salts include calcium chloride, magnesium chloride, sodium chloride, and sodium sulfate. First, the concentrations of the delayed zirconium crosslinker, which is used to crosslink the carboxymethyl hydroxypropyl (CMHPG) polymer, and high-pH GLDA were optimized. The testing parameters for the crosslinker and chelating agent optimization experiments were a 70 °C temperature, a 500 psi pressure, and a 100 1/s shear rate. However, the temperature was raised to 120 °C representing harsh reservoir conditions. Results showed that sulfate had a significant effect on the rheology of the crosslinked CMHPG polymer. Unlike DI water, the viscosity of SW and individual ions increased when the crosslinker concentration was increased. In addition, the solution stability of magnesium chloride and DI water was improved. Adding a chelating agent at a low concentration improved the solution stability of magnesium chloride and DI water. These findings are critical for comprehending the rheology of produced water and SW-based fracturing fluids.