Development and evaluation of cross-linked fracturing fluid stability and scale inhibition synergy in high-temperature, high-salinity environments

The use of seawater as a base fluid for fracturing applications can significantly reduce freshwater consumption; however, the high salinity and reservoir temperatures degrade polymer networks and destabilize rheological properties. Hence, this study develops and measures a crosslinked fluid for high-temperature wells (i.e., 300 °F) with low polymer loading (40-lb/1000-gal), utilizing Arabian Gulf seawater with a total salinity of 58,850 ppm. The measurements of liquid viscosity were conducted using a high-temperature, high-pressure viscometer at elevated temperatures (212-302 °F). Additionally, Thixotropic analysis was investigated to assess the structural strength of the fluid at 302 °F. Furthermore, the broken gel was studied to measure the residual content. A zirconium-crosslinked carboxymethylhydroxypropyl guar (CMHPG) system at acidic pH (~ 5) displayed rapid viscosity loss at 265 °F. The addition of 1 wt.% viscoelastic surfactant improved the thermal stability by 100%, extending the period with viscosity > 200 cP at 265 °F. The combination of 2,000 ppm zirconium and 2,000 ppm borate crosslinkers significantly enhanced the thermal stability, maintaining the viscosity stable for 69 min at 302 °F, above 200 cp. at 100/s, through the pseudo-cationic bonding of boric acid with CMHPG. Finally, the scale inhibitor has a negative impact on crosslinked solution at 302 °F; nevertheless, 1 wt% of Diethylenetriaminepentaacetic acid (DTPA) decreased the solution viscosity slowly, maintaining high viscosity for 60 min. In addition, the high recovery of fluid's viscosity confirmed the robust structure of the dual crosslinked system at 302 °F. Moreover, the low polymer loading system (40-lb/1000-gal) obtained low residual content as compared with (52-lb/1000-gal) CMHPG. This study provides a comprehensive understanding of the elevated temperatures, water chemistry, scale inhibitors, surfactants, and borate crosslinker on the development of seawater fracturing fluid for high-temperature reservoirs.