A Low-Polymer High-Temperature Water-Based Fracturing Gel Enabled by a Dual-Ligand Organic Zirconium Crosslinker: An Experimental Study.

This experimental study aimed to develop and evaluate a low-polymer, high-temperature water-based fracturing gel using a dual-ligand organic zirconium crosslinker regulated by sodium lactate and ethylene glycol. The crosslinker was selected by ligand screening and single-factor optimization using the apparent viscosity of LX641 gels as the primary response, and was characterized by FTIR and electron microscopy. Gelation, salt response, high-temperature shear rheology, oscillatory and steady-shear behavior, static fluid loss, gel breaking, proppant suspension, and core-permeability damage were then evaluated. The selected zirconium oxychloride octahydrate/sodium lactate/ethylene glycol/water/NaOH mass ratio was 10:6:4:15:1.2, with synthesis at 55 °C, pH 7, for 4 h. A 0.2 wt.% LX641 gel at a base-fluid/crosslinker-solution volume ratio of 100:0.5 retained an apparent viscosity of 246.84 mPa·s at 100 min after heating to 190 °C within 25 min and shearing at 190 °C for the remaining 75 min at 170 s-1. The system also showed no visible settling of 10 wt.% 30-mesh ceramic proppant after 12 h, core-permeability damage of 11.98-13.65%, and visually clear broken fluid within 2 h using 0.01 wt.% ammonium persulfate at 70 °C. The results indicate that sodium-lactate/ethylene-glycol regulation can support substantial high-temperature viscosity retention at only 0.2 wt.% polymer loading, providing a low-polymer alternative for further development of high-temperature zirconium-crosslinked fracturing gels.