Organic/Inorganic Hybrid Cross-Linked Weighted Fracturing Fluid for Ultra-Deep Hydrocarbon Reservoirs: Rapid Dissolution, Remarkable Drag Reduction, and Superior Temperature Resistance

Fracturing fluids are indispensable in hydrofracturing technology within the upstream sector of the oil and gas industry. Weighted fracturing fluids have received increasing attention in recent years as they exhibit remarkable capability in mitigating the extreme formation pressures encountered in ultradeep reservoirs. However, current formulations face significant challenges, including inadequate solubility in high-density brine solutions, insufficient drag reduction, and limited temperature resistance. To address these issues, this study proposes an innovative instant polymer thickener comprised of ultrahigh molecular weight linear hydrolyzed polyacrylamide (HPAM), white oil, Span 85, and montmorillonite, augmented with a composite cross-linker composed of a Zr compound and polyethylenimine. The dissolution rate of this instant thickener in weighted salt water was six times faster than that of the corresponding HPAM powder, effectively resolving the issue of poor solubility. Moreover, the viscoelasticity, thermal stability, and drag reduction performance of the instant thickener-based weighted fracturing fluid (I-HPAM) comprehensively surpass those of systems based on a direct HPAM polymer. This enhancement is attributed to the elongation of the polymeric chain conformation facilitated by Span 85. The I-HPAM achieved a maximum drag reduction rate of up to 63.8%. By incorporating robust organic/inorganic hybrid cross-linked network structures, the I-HPAM fracturing fluid demonstrated exceptional viscoelasticity even at 200 °C. Additionally, its gel-breaking ability and core damage characteristics were commendable, with residues below 600 mg/L and a core damage rate of 24.8%. This study provides a superior weighted fracturing fluid for ultradeep reservoirs and introduces a novel strategy for the development of such fluids.