RATE CONSTANTS OF N-ALKANES GENERATION FROM TYPE-II KEROGEN IN OPEN AND CLOSED PYROLYSIS SYSTEMS

The purpose of this work is to carry out artificial maturation of a ma rine kerogen under isothermal conditions in open and closed systems an d to derive kinetic parameters for primary C-10+ n-alkanes generation. Reaction mechanisms and accurate kinetic parameters for two individua l n-alkanes C-12 and C-24 generation are derived. Results show that no rmal alkanes generation follows a first-order kinetics in both open an d closed pyrolysis systems. Combining the rate constants derived from open and closed system pyrolysis, one can obtain the Arrhenius plot in a large temperature range (100 degrees C). Based on the linearity of the Arrhenius plot, accurate sets of kinetic parameters for the genera tion of n-C-12 (E = 54.3 kcal/mol, A = 4.32 x 10(14) s(-1)) and n-C-24 (E = 53.0 kcal/mol, A = 1.37 x 10(14) s(-1)) are derived. The extrapo lation of these kinetic parameters to geological conditions shows a qu alitative agreement with what observed on the relative distribution of n-alkanes in source-rock extracts.