Experimental study on generation of associated gas from aquathermolysis of Liaohe super-heavy oil

Steam-assisted gravity drainage (SAGD) is widely used to recover super-heavy oil, during which high-temperature steam reduces viscosity and triggers aquathermolysis reactions that generate associated gases. Field data from the Du84 block in the Liaohe Oilfield show significant gas accumulation—mainly CO2 and CH4—at the top of the steam chamber, though the formation mechanisms remain unclear. This study conducted autoclave experiments under SAGD-like conditions to investigate gas generation in Liaohe super-heavy oil. Aquathermolysis occurred primarily between 240–280 °C, with CO2 comprising ∼80% of the gases and a 0.193% conversion rate at 240 °C. Gas yield increased with both temperature and reaction time. The addition of clay minerals boosted gas production by ∼32%, indicating catalytic activity. This study develops a comprehensive five-component (CO2, CH4, H2S, H2 and C2+) parallel reaction kinetic model specifically for super-heavy oil. By integrating mineral catalytic effects and individual gas evolution pathways, the model offers superior predictive accuracy over traditional frameworks. These results enhance understanding of gas formation during SAGD and provide practical guidance for improving gas control and oil recovery in super-heavy oil reservoirs.