Abstract:

To solve the problems of poor temperature resistance, short cross-linking time and high residue content of fracturing fluids commonly used in field, an organic zirconium cross-linking agent YJ-3 was successfully synthesized from zirconium oxychloride, polyols, organic ligands, complex cross-linking agent and high temperature stabilizer. On this basis, a temperature resistant and slowly-cross-linking organic zirconium gelled fracturing fluid was prepared by selecting polyacrylamide thickener RG-1 and additives. Mass fractions of YJ-3 and RG-1 were optimized by single factor method, and the performance indexes of the fracturing fluid system were evaluated. Experimental results showed that the optimal composition of the fracturing fluid was 0.50% RG-1+2.0% YJ-3+0.15% Na₂S₂O₃+0.8% cleanup additive. The cross-linking time was adjustable between 3 and 45 min. The viscosity was still higher than 50 mPa·s at 90 ℃ and 150 ℃ after shear at 170 s^-1 for 2 h. The sand-carrying performance and filtration property were obviously better than that of conventional fracturing fluid system based on guar gum. Fracturing fluid could be completely broken within 1-3 h, without residue and easy to flow back. It is a kind of temperature-resistant, slowly-cross-linking and low-damage fracturing fluid with excellent performance, which has a broad application prospect.

Key words: temperature resistance, organic zirconium gel, fracturing fluid, slowly-cross-linking, performance evaluation