Study on the Influence of Composition Differences in Heavy Oil Components on In-Situ Combustion Coking Performance

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Abstract
This study investigates coke formation, structure, and combustion behaviors in paraffin-based Menggulin and naphthenic-based Xinjiang heavy oils under simulated in-situ combustion (ISC) conditions (350 °C, 450 °C), utilizing GC-MS, SEM, 13C ss-NMR, and TG-DSC. The results indicate that the crude oil composition determines the coking mechanisms: Xinjiang oil, rich in cyclic hydrocarbons and O/N/S heteroatoms, forms high-yield, compact, sheet- or block-like coke at 350 °C via π–π stacking. In contrast, Menggulin oil, composed primarily of long-chain alkanes, yields loose coke at 350 °C but produces dense, highly aromatized coke at 450 °C, which corresponds to the critical alkane cracking temperature, through intense cracking–polymerization. Temperature differentially regulates oxidative processes, thereby shaping the divergent functional group distributions. Correlations between coke structure and combustion properties reveal that oxygenated/aliphatic-rich cokes exhibit high reactivity, whereas aromatized cokes release more heat. These findings provide guidance for ISC optimization, suggesting that sufficient high-temperature energy is required for paraffinic oils while medium-temperature oxidation regulation is suitable for naphthenic oils. This work advances the theory of ISC coke formation and supports enhanced recovery of heavy oils.
Funding Information
  • China Petroleum Science and Technology Special Project “Pilot Experiment of Conjugated Development via Fire Flooding-Flue Gas Flooding in Menggulin, Huabei Oilfield” (2023YQX10412ZK)

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