Large amounts of data regarding the influence of temperature and pressure on the thermal stability of crude oil have been pub-lished;however,the role of reservoir mediums has received little attention.Experiments involving oil cracking in the presence of montmorillonite,illite,calcite,quartz and water were conducted in closed gold tubes to investigate the effects of these reservoir mediums on oil destruction.This was done by screening variations in the chemical and stable carbon isotopic components of nC10+ and gasoline-range hydrocarbons(nC8-)present in various systems.Results indicated that reservoir mediums have an active role in oil cracking under experimental conditions.The concentrations of nC10+ in the cracked residues progressively decreased in systems containing oil+water+illite,oil+water+montmorillonite,oil+water,oil+water+quartz and oil+water+calcite.In comparison with the system containing oil+water,our results indicated a retardation effect for oil cracking in systems in the presence of illite and montmorillonite,and an acceleration effect on oil destruction in systems in the presence of calcite and quartz.nC10+ became increasingly depleted in 13C in systems with oil+water+illite,oil+water+calcite,oil+water+montmorillonite,oil+water+ quartz and oil+water.No obvious correlation was observed between concentrations and stable carbon isotopic components of nC6-nC8 and nC10+ in the individual systems.The discrepancies in chemical and stable carbon isotopic components of nC6-nC8 and nC10+ in the pyrolyzed residues highlighted the important role of reservoir mediums to control carbon-carbon cleavage of nC10+ and then the isomerization,cyclolization and aromatization reactions;as well as governing the occurrence and thermal destruction of nC6-nC8 under experimental conditions.This research may have critical implications in reconstructing chemical kinetic models for natural oil cracking.
XIAO QiLin1,2,SUN YongGe1,3 & ZHANG YongDong1,2 1 State Key Laboratory of Organic Geochemistry,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,China
