Abstract:

Two n-butanol zirconium crosslinkers were prepared using n-butanol zirconium as the central ionic reagent and 3-amino-1，2-propanediol （APG） and N-methyldiethanolamine （MDEA） as the organic ligands， respectively. A series of water-based fracturing fluids were prepared with konjac glucomannan （KGM） solution and n-butanol zirconium crosslinker The morphology， structure and properties of fracturing fluid are systematically characterized by Fourier transform infrared spectrometry （FT-IR）， nuclear magnetic resonance spectroscopy （NMR）， high resolution mass spectrometer （HRMS）， rheometer， scanning electron microscopy （SEM）?， and differential scanning calorimeter （DSC）. The reaction pathway of zirconate and KGM crosslinking is discussed. The sol-gel transition point is accurately determined by Winter-Chambon formula. The effects of reactant concentration and ligand species on storage modulus （G'）， loss modulus （G″）， and sol-gel transition time （t_cr） are studied. It is found that compared with APG ligand， the organozirconium/KGM gel system with MDEA as ligand have better delayed cross-linking performance， better temperature and shear resistance. Its t_cr shows a trend of first decreasing and then increasing with the increase of KGM concentration， and a decreasing trend with the increase of ligand concentration and crosslinking agent concentration. When the concentration of KGM solution is controlled at 4.0 g/L， the delay time of gel system can be adjusted within 7~45 min at room temperature， the sol-gel transition temperature （T_sol-gel） is 71.4 ℃， and its temperature resistance can reach 120 ℃. The viscosity of 171 mPa·s is maintained at a shear rate of 170 s^-1. The organic zirconium crosslinked KGM gel system provides a useful reference for the research and application in the field of petroleum exploitation.

Key words: Konjac glucomannan, Zirconium n-butoxide, Coordination, Delayed gelation, Dynamic rheological properties