Abstract: Taking advantage of fly ash to prepare poly silicic acid, setting polysilicate and borax as the raw materials,a kind of high temperature retarding crosslinking agent was synthesized.With the single factor method and measuring the performance of boron crosslinking agent,the optimum process parameters was obtained that borax mass fraction was 5wt%, ligand mass fraction was 28.5wt%, the reaction temperature was 80 ℃, catalyst mass fraction was 1.5wt%.The target product was characterized by IR,the rheological property of the cross-linked HPG gel fracturing fluid was evaluated on the condition that the concentration of the HPG was 0.45wt%,cross ratio was 100∶0.8 (volume ratio),110 ℃, 170 s-1,shearing 2 h, which turned out that the viscosity of cross-linked HPG gel fracturing fluid was more 130 MPa·s.It proved that the crosslinking agent had better effect on HPG.The breaking test's results shown that the crosslinked fracturing gel had the characteristics of easily breaking and low residue.

Key words: fly ash;boron crosslinking agent;thickening agent;fracturing fluid;temperature resistance;shear resistance