Low-carbon development strategy to achieve heat conversion in heavy oil reservoirs: In-situ combustion

In-situ combustion (ISC) is a low-energy consumption and low-emission technology for developing heavy oil reservoirs, offering significant benefits in enhanced thermal recovery. However, in actual reservoirs, reservoir heterogeneity directly impacts the advancement of the combustion front during the ISC process. Particularly in shielded areas with strong physical properties, the combustion front struggles to penetrate, leading to some heavy oil being unrecoverable from production wells. Using catalysts is considered an effective method to enhance the efficiency of ISC of heavy oil. This paper investigates the catalytic mechanism of catalysts for the three-stage oxidation process of heavy oil through thermogravimetric (TG) analysis experiments. Additionally, it examines the impact of catalysts on the ISC performance of heterogeneous heavy oil reservoirs using threedimensional (3D) physical simulation experiments. The results demonstrate that the oil-soluble catalyst reduces the ignition point of heavy oil from 441 degrees C to 426 degrees C in the TG analysis experiment, intensifying the oxidation reaction at high temperatures and generating more heat. The 3D physical simulation experiment illustrates the ISC process of heterogeneous heavy oil reservoirs. Physical occlusion impedes the progress of the combustion front and generates localized high temperatures, yet no high-temperature zone forms in the oil sand area affected by physical occlusion. After adding the oil soluble catalyst for relay ignition, a new fire line forms. This fire line connects with the original fire line to collectively penetrate the physical barrier, expelling crude oil from the affected area. At this point, approximately 70% of the reservoir experiences high temperatures, resulting in less remaining oil in the model. The remaining oil constitutes 19.28% of the heavy oil initially present in the reservoir, with a recovery rate reaching 76.46%. These results demonstrate that the oil soluble catalyst can enhance the ISC performance of heterogeneous heavy oil reservoirs and offer theoretical guidance for subsequent field development.