Addressing the challenges in fracturing the WC ultra-low permeability, tight sandstone, high-temperature, and high-pressure gas reservoir (wellhead pressure: 79 MPa; closure pressure: 86 MPa; temperature: 230°C), such as high treating pressure, proppant placement difficulty, fracture extension complexity, inadequate temperature resistance of conventional fluids, and limited freshwater availability, this study developed a seawater-based, nano-enhanced fracturing fluid stable at 230°C. The optimized formulation (0.5% SRP-1 + 0.02% hydrophilic nano-ZrO? + 0.6% YCJ-1+0.2% pH buffer+ 1% KCl + 0.5% ZP-1) maintained a viscosity of 172 mPa.s after shearing at 230°C and 170 s?1 for 2 h, broke completely to 3.23 mPa.s, and caused less than 19% core damage. A composite proppant placement strategy using a blend of small, medium, and large mesh sizes (40/70: 30/50: 20/40 = 1:2:1), which achieved a fracture conductivity of 15 D.cm under 86 MPa closure pressure, ensuring long-term flow capacity while mitigating placement difficulties. Field applications confirmed that this integrated approach successfully addressed the technical challenges, significantly increasing proppant placement efficiency and stimulation performance, providing robust technical support for the efficient development of similar offshore high-temperature gas resources.