超深井非交联复配盐加重压裂液体系构建与性能协同机制OA

Facing the challenges of ultra-deep well fracturing,such as high wellhead pressure,narrow operational safety window,and restricted polymer hydration and thickening under high-temperature and high-salinity conditions,there is an urgent need to develop a fracturing fluid system characterized by high density,high-temperature resistance,low friction,and low reservoir damage.In this study,a ternary non-crosslinked weighted fracturing fluid system was formulated by incorporating the non-crosslinked hydrophobic associative polymer thickener prepared with AM,AA,AMPS and C16AMSE-Na as monomers,the weighting agents such as NaCl,HCOOK and(NH4)2SO4,and the compound salt optimized through orthogonal experiments.The chain conformation and hydrophobically associating behavior of the polymer in different salt environments were investigated by means of dynamic light scattering and pyrene fluorescence probing.In addition,the high-temperature rheology,viscoelasticity,static proppant suspension,friction reduction,gel-breaking performance,fluid-loss control,and core damage characteristics of the system were evaluated.The following results are obtained.First,with the compound-salt density of 1.462 g/cm3 and the thickener dosage of 0.50 wt%,the ternary system encompasses the polymer with the Z-average hydrodynamic diameter increased to approximately 694 nm,the PDI decreased to 0.275,and the I1/I3 ratio lowered to approximately 1.25 compared with the single HCOOK system,indicating that it can alleviate excessive polymer-chain contraction and promote intermolecular hydrophobic association.Second,the ternary system exhibits the apparent viscosity of 63.54 mPa·s after shearing at 180℃and 170 s－1 for 120 min,and remains approximately 55.2 mPa·s after thermal aging at 180℃for 4 hours,demonstrating its capability of static proppant suspension and high-temperature fluid-loss control.Third,compared with high-temperature crosslinked weighted systems,the ternary non-crosslinked system improves the friction reduction efficiency by 12.8%,and reduces the average core damage rate by 38.9%.In conclusion,by coordinating polymer-chain hydration and extension with the formation of hydrophobic association networks,the proposed ternary compound-salt non-crosslinked weighted fracturing fluid system achieves a multi-performance synergy of high density,high-temperature rheological stability,low friction,and low reservoir damage.The research provides a reference for the optimization and field application of fracturing fluids for ultra-deep wells in high-temperature and high-pressure reservoirs.