Evaluating the impact of reservoir properties on in-situ combustion stability in extra-super heavy oil using temperature peaks and characteristic parameters

In-situ combustion is a promising follow-up technology for shallow, extra-super heavy oil post-steam injection. Evaluating its stability and optimizing parameters through lab tests is crucial. However, existing studies rely on qualitative criteria like "combustion front extinction" rather than quantitative stability indicators. This research proposes a novel method to assess in-situ combustion dynamic stability using temperature peaks and their characteristic parameters. Combustion-tube experiments evaluated permeability and oil saturation effects. Key findings within the studied ranges: (1) The slope ratio (SR) of temperature peaks strongly correlates with stability and serves as a quantitative indicator. Stability occurs when SR standard deviation is <2 and range <4; instability occurs when >5 and >10, respectively. Four peak patterns are defined by slope ratios: plateau peak (SR>10), dragging peak (2<SR<10), sharp peak (1<SR<2), and front-extended peak (SR<1). (2) Stability is controlled by gas flow resistance, oil bank evolution, and overriding effects. Reduced permeability and increased oil saturation (>45%) intensify gas resistance and impair oxygen transfer. This, combined with oil bank suppression and late-stage gas channeling from overriding, causes instability (e.g., instability at 0.2 D permeability, worsened at 45% oil saturation). The temperature peak analysis provides dynamic adjustment benchmarks for physical modeling, enhancing experimental success and mechanistic studies. It also offers new technical support for field stability monitoring and optimization in extra-super heavy oil in-situ combustion.