Insights into oil cracking based on laboratory experiments

The effect of oil expulsion or retention on further thermal degradation of kerogen at the high maturity stage: A pyrolysis study of type II kerogen from Pingliang shale, China

“…3 and 4). The higher stabilities of aromatic hydrocarbons relative to those of saturated hydrocarbons in the simulation experiments have been well documented for the pyrolysis of oils in a closed system (Behar et al, 1999;Hill et al, 2003;Tang et al, 2005), even though the opposite trend has been observed in natural conditions (Horsfield et al, 1992). It is notable that the relative amounts of aromatic hydrocarbons in expelled oils are lower than those generated by KAE in the temperature range from 336-384°C (Fig.…”

“…Relatively lower HI in residual solids of KO compared to that in the residual solids of KAE at the pyrolysis temperature of 384°C could be explained by the reduced formation of pyrobitumen due to the oil expulsion. Pyrobitumen is mainly derived from aromatic condensation of oil or bitumen (Ungerer et al, 1988;Behar et al, 1992;Schenk et al, 1997;Hill et al, 2003).…”

“…The oil generation of type II Toarcian kerogen peaked at the EasyRo value of 1.2% (Dieckmann et al, 1998), and the extracted oil included not only the C 15+ fraction but also the C 6-14 fraction. The secondary cracking of the C 15+ fraction starts at lower pyrolysis temperatures than that of the C 6-14 fraction (Dieckmann et al, 1998;Hill et al, 2003;Walters et al, 2007). For example, in the pyrolysis experiments performed under closed conditions at a heating rate of 5°C/min, secondary cracking of the C 15+ fraction could occur at temperature $40°C lower than cracking of the C 6-14 fraction (Dieckmann et al, 1998).…”

Retardation of oil cracking to gas and pressure induced combination reactions to account for viscous oil in deep petroleum basins: Evidence from oil and n-hexadecane pyrolysis at water pressures up to 900 bar

“…Price et al, 1979;Price et al, 1981;Price, 1982;Mango, 1991;Hayes, 1991), laboratory pyrolysis investigation of oils (e.g. Ungerer and Pelet, 1987;Ungerer et al, 1988;Behar et al, 1992;Behar et al, 1997a;1997b;Schenk et al, 1997;Dieckmann et al, 1998;Lewan and Ruble, 2002;Hill et al, 2003;Lehne and Dieckmann, 2007a;2007b;Behar et al, 2008), or theoretical calculations (e.g. Dominé et al, 1998).…”

“…Undegraded crude oils generally show an increase in both API gravity and gas to oil ratio (GOR) with increasing depth of burial (Tissot and Welte, 1984), which can result from the conversion of oil into lighter hydrogen-rich products (gas and condensate) and heavy carbon rich solid residues (coke or pyrobitumen). Pyrobitumen forms either by aromatic condensation reactions (Ungerer et al, 1988;Behar et al, 1992), or directly from nitrogen sulphur and oxygen (NSO) compounds (Hill et al, 2003). Oil cracking to gas was described as occurring via hydrogen transfer reactions (Bailey et al, 1974;Connan et al, 1975), although it also appears that the mechanism involves free radical reactions (Rice and-Herzfeld 1934), with initiation, hydrogen transfer, decomposition of carbon-carbon bonds by ß-scission, radical isomerization, addition and termination processes in the oil (e.g.…”