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APPENDIX II: THE HUNT et al (1991) KINETIC MODEL

 

The Arrhenius equation can be expressed as

k = A exp -E (1)
RT

where k is the reaction rate constant (1/m.y.), A is the pre-exponential or frequency factor (1/m.y.), E is the activation energy (kJ/mol), R is the ideal gas constant, and T is temperature in kelvins (degrees C + 273).

A time-temperature index (TTI) based on the Arrhenius equation is:

TTIARR = A(tn+1 - tn) {[ RT²n+1 exp( -E )]-[ RT²n exp( -E )]} *100 (2)
Tn+1 - Tn E + 2RTn+1 RTn+1 E + 2RTn RTn

where t[n] and t[n+1] are, respectively, the time (m.y.) and T[n] and T [n+1] are, respectively, the absolute temperature (degrees C + 273) at the start and end of a 10 degree C interval. R, E, and A are the same as in the Arrhenius equation (1) previously described.

X% =[1 - exp ( -STTIARR )] * 100 (3)
100

Despite different values for the kinetic parameters, E and A, for different source rock types (Table 1), the (summation) TTI [ARR] values are related to the same percentage of oil generated (X%) by the expression: