Synergistic in situ upgrading and heat storage in intermittent SAGD enabled by a bifunctional nanocatalyst

Abstract The efficient development of heavy oil and oil sands resources faces critical challenges, particularly the high energy consumption and lack of in-situ upgrading capabilities of Steam-Assisted Gravity Drainage (SAGD) technology. This study proposes a bifunctional nanocatalyst-assisted intermittent SAGD (CNF-I-SAGD) technology to achieve in-situ heavy oil upgrading and efficient thermal energy management. The core innovation is a Ni-Mo/Al₂O₃@Al-Sn-Si core-shell nanocatalyst, where the Al-Sn-Si ternary eutectic alloy acts as a phase-change material (PCM) for thermal energy storage, and the Ni-Mo/Al₂O₃ shell catalyzes hydrothermal cracking.Physical simulation experiments demonstrate that CNF-I-SAGD achieves a final recovery factor of 72.5%, 7.9% higher than conventional I-SAGD. Crucially, during intermittent steam shut-in, the PCM core releases latent heat, maintaining a temperature plateau near 225 °C for up to 8 min, extending the catalyst’s effective high-temperature operating time by 18.5%. This reduces the instantaneous steam-oil ratio (SOR) to 3.56 and improves energy efficiency by 18.7%. Oil analysis reveals that the produced oil exhibits an API gravity increased to 15.2°, a viscosity reduction of 71.7%, and a significant 58% decrease in asphaltene content. This research presents an integrated approach coupling PCM-based thermal energy storage with nanocatalytic in-situ upgrading, offering a promising strategy for green and efficient heavy oil resource development.