Effects of the combined use of kaolinite and dolomite as catalysts for the heavy oil oxidation

The oxidation of heavy oil (HOO) during In-situ combustion (ISC) within the porous media of reservoir rock matrix is a critical process. Although previous research has individually investigated the catalytic capabilities of clay minerals (e.g., kaolinite) and carbonate minerals (e.g., dolomite) in HOO, their combined influence remains unexplored. This study aims to investigate the impact of dolomite and kaolinite coexistence on HOO in the Badaowan Formation reservoir located in the Karamay Oilfield. The findings reveal that the Hongqian (HQ) core displays remarkable catalytic ability for HOO, evidenced by the reduction in peak temperatures ( T _peak ) of differential scanning calorimetry (DSC) and infrared absorption of H ₂O and CO ₂ during heavy oil HTO stage. The enhanced catalytic ability is not solely attributed to the presence of single-component minerals like quartz, feldspar, dolomite, or kaolinite within the HQ core. Instead, the kaolinite/dolomite composite showcased a synergistic effect, significantly lowering the T _peak of DSC (HTO) beyond the performance of kaolinite or dolomite acting independently. This synergistic effect is closely associated with the dehydroxylation process of kaolinite. Notably, the catalytic effect of the kaolinite/dolomite composite on HOO was further enhanced at calcination temperatures above 450 °C, primarily due to the increased catalytic ability of dolomite after calcination.