Integrated stimulation technology for ultra deep tight sandstone gas reservoirs with ultra low permeability in Sichuan Xujiahe formation

The development of tight sandstone gas reservoirs in the XUJIAHE Formation of western Sichuan faces critical challenges due to extreme reservoir conditions, including burial depths exceeding 4500 m, abnormal pore pressures (pressure gradient > 1.8 MPa/100 m), high breakdown pressures (> 90 MPa), elevated temperatures (> 120 °C), and ultralow permeability ( 2.5) and conductivity (> 100 Darcy), achieving a fivefold improvement in proppant transport capacity (600 kg/m³). Third, gelled acid pre-treatment (15% HCl system) dissolved calcareous interlayers (CaCO₃ >70%), reducing injection pressure by 14.83 MPa and increasing proppant migration efficiency by 30% in challenging Xu 4 intervals. Field implementation demonstrated breakthrough performance: fracturing success rates improved to 82%, with average post-fracture gas production reaching 2.7 × 10⁴ m³/d—a 210% increase over conventional methods. These innovations tight gas stimulation by synergistically addressing high-stress environments, fracture network complexity, and lithological heterogeneity, providing a replicable framework for deep unconventional reservoirs.