Ultralow Concentration Guar Gum Fracturing Fluid System with Ultrahigh Proppant Concentration

Summary High polymer loadings, significant residue-induced formation damage, and an inherent compromise between proppant transport and operational control limit the effectiveness of conventional guar gum fracturing fluids. With this study, we present a solution in the form of an ultralow-concentration hydroxypropyl guar (HPG) system enabled by a novel polymeric boron crosslinker. The crosslinker is synthesized from acrylamide, a boron-functional monomer (3-acrylamidophenylboronic acid), and a cationic monomer ([2-(acryloyloxy)ethyl]trimethylammonium chloride). Performance is advanced through three key innovations. First, a strategy of “physical modulation of crosslinking kinetics” is introduced. Gelation time (2–10 minutes) is controlled in real time by adjusting the inversion-agent dosage, effecting a paradigm shift from chemical design to physical process control. Second, the HPG concentration is dramatically reduced to 0.15 wt%, significantly reducing the potential for formation damage. Third, at this ultralow loading, the fluid achieves a high proppant-carrying capacity, sustaining proppant concentrations up to 50%. Laboratory testing at 90°C and 170 s⁻¹ for 90 minutes confirmed a retained viscosity above 85 mPa·s, a broken-gel residue concentration below 200 mg/L, and a core-damage rate under 20%. In field trials at a certain oil field, the proposed system was compared with a conventional organoboron crosslinker system. Throughout the operation, the slurry rate remained stable at 1,000 L/min. During the proppant-transport stage, the average proppant ratio reached 21.7%, with a peak of 45%. The treating pressure was stable and approximately 6.3% lower than that of the control well. The target well achieved an initial daily oil production of 2.66 t/d, representing a 45.4% increase compared with the control well. The gel was completely broken down in the flowback fluid, consistent with the low-damage results observed in laboratory tests. This study provides a fracturing-fluid system that combines excellent proppant transport performance with low-damage characteristics for the efficient development of low-permeability tight oil and gas reservoirs.