Modelling petroleum formation from heterogeneous source rocks: the influence of frequency factors on activation energy distribution and geological prediction

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

“…For coal samples, simplified kinetic models with a single frequency factor are not sufficient to correctly predict hydrocarbon generation under geological conditions (e.g., Dieckmann, 2005). The main purpose for the kinetic modeling in the present study is to characterize the differences in kinetic properties for the generation of gas hydrocarbons among the three experiments of extracted coal, coal and bitumen rich coal.…”

“…At first, we set a range 1 Â 10 9 /s-1 Â 10 13 /s for the A factor, referenced from the previous studies (e.g., Behar et al, 1997;Dieckmann, 2005). After input of the data from the two heating rates, i.e.…”

“…In order to avoid this compensation effect, we used a fixed frequency factor of 4 Â 10 11 /s for methane generation in all three experiments. This frequency factor is suitable for early methane generation, but lower for late methane generation from coal samples (e.g., Behar et al, 1997;Dieckmann, 2005). The kinetic parameters for the generation of methane are listed in Table 5.…”

Technical note: An inverse method to relate organic carbon reactivity to isotope composition from serial oxidation

“…There exists significant discussion in the literature on the best choice of ω, as multiple values can describe laboratory results equally well but will result in drastically different predictions of OC degradation rates over geologic timescales (Braun and Burnham, 1987;Dieckmann, 2005). Furthermore, it has been argued that ω represents a variable change in entropy associated with the decay of specific organic compounds and should therefore be parameterized as a function of E (the so-called "kinetic compensation effect" or KCE; Dieckmann, 2005;Lakshmanan et al, 1991;Tang et al, 2000). For example, a linear ω increase with E from ≈ 10 8 s −1 (E = 175 kJ mol −1 ) to ≈ 10 26 s −1 (E = 400 kJ mol −1 ) has been utilized to better predict petroleum formation rates (Dieckmann, 2005).…”

“…Furthermore, it has been argued that ω represents a variable change in entropy associated with the decay of specific organic compounds and should therefore be parameterized as a function of E (the so-called "kinetic compensation effect" or KCE; Dieckmann, 2005;Lakshmanan et al, 1991;Tang et al, 2000). For example, a linear ω increase with E from ≈ 10 8 s −1 (E = 175 kJ mol −1 ) to ≈ 10 26 s −1 (E = 400 kJ mol −1 ) has been utilized to better predict petroleum formation rates (Dieckmann, 2005). To circumvent the issue of multiplicity, and to account for the KCE, Miura and Maki (1998) developed a method to estimate the best-fit ω for each E value by comparing the shift in elution temperatures when a sample is analyzed at multiple ramp rates.…”