Enhanced late gas generation potential of petroleum source rocks via recombination reactions: Evidence from the Norwegian North Sea

Hydrocarbon generation from coal, extracted coal and bitumen rich coal in confined pyrolysis experiments

“…The differences in methane yields among the three experiments at same temperature are relatively minor at EASY%R o < 2.2, but greater with temperature at EASY%R o > 2.2 (Table 2). This result demonstrates that the solid organic residue always retained more hydrogen and higher hydrocarbon generative potential at the postmature stage in the bitumen rich coal than the extracted coal and coal experiments, consistent with previous studies (Dieckmann et al, 2006;Erdmann and Horsfield, 2006). 4.1.5.…”

“…However, activation energies for cracking of these gases decrease with carbon number, reflecting decreased thermal stabilities of these components with carbon number, consistent with the previous study (Pan et al, 2012). It can be deduced that primary cracking gas is generated at lower thermal stress than secondary cracking gas, and therefore, activation energies for the generation of primary cracking gas are lower than those of secondary cracking gas from previous studies on kerogen and oil pyrolysis (e.g., Behar et al, 1992;Horsfield et al, 1992;Hill et al, 2003;Erdmann and Horsfield, 2006). The wet gases have higher ratios of the secondary cracking components from liquid hydrocarbons to the primary cracking components from kerogen in the bitumen rich coal experiment compared to the other two experiments.…”

“…1c). This result suggests that for the bitumen rich coal experiment from the starting temperature to the temperature for EASY%R o 1.0, bitumen generation was suppressed and/or the initial and newly generated bitumen were partially incorporated into the solid organic residue, as suggested by previous studies (Dieckmann et al, 2006;Erdmann and Horsfield, 2006).…”

“…For the present experiments, the generated gases included both primary and secondary components. The primary gases were generated directly from macromolecular precursors (kerogen, resins and asphaltenes) while the secondary gases were generated from oil or liquid hydrocarbons (e.g., Behar et al, 1992;Prinzhofer and Huc, 1995;Erdmann and Horsfield, 2006). As indicated by the yields of Rn-C 8+ , the yields of liquid hydrocarbons are substantially higher in the bitumen rich coal than in the extracted coal and coal experiments.…”

“…However, gas products were not investigated in their study. Erdmann and Horsfield (2006) suggested that the recombination reactions of liquid products released from type III kerogen at low levels of maturation result in the formation of a thermally stable bitumen, which is the major source of methane at very high maturity based on non-isothermal closed (microscale sealed vessel) and open pyrolysis studies. Vu et al (2008) observed that the yields and compositions of gas and liquid hydrocarbons are significantly different between extracted and 0146-6380/$ -see front matter Ó 2013 Elsevier Ltd. All rights reserved.…”