Distributed activation energy models of isomerisation reactions from hydrous pyrolysis

Organic Geochemistry(1993)

引用 5|浏览1
暂无评分
摘要
Distributed activation energy models of sterane and hopane isomerisation have been developed using time series of hydrous pyrolysis experiments at 300, 320 and 350°C and a formalised optimisation procedure against field data. Frequency factor (s−1), mean activation energy (Ea, kcal/mol) and distribution factor (% of Ea) of hopane isomerisation are 1.0E8, 37.0 (± 0.5) and 2.9%, hose of sterane isomerisation are 3.5E7, 37.5 (±1.0) and 2.9% respectively. The models are able to predict the reactions at geological as well as experimental heating rates, which constitutes a considerable improvement on most previous models. The mean (50% of the reaction completed) transformation temperature of the sterane isomerisation model at 2.5°C/Ma is 104±9°C; the corresponding temperature for hopane isomerisation is 91±3°C. Verification against an independent set of field data suggests furthermore that temperatures can be determined at an accuracy of ±7.5°C and that the model temperatures tend to be too low by ∼ 5°C at low transformation ratios. The models correlate with apatite fission track (AFTA) temperatures at a coefficient of 0.91 and also tend to be too low at low transformation ratios. In contrast to single-activation-energy models distributed models match the whole reaction interval better and respond in a more differentiated way to complex thermal histories. Further refinement of the models using sequential- or competing mechanisms would lead to improved performance only in case of thermal histories with strong emphasis on back reactions.
更多
查看译文
关键词
sterane isomerisation,hopane isomerisation,hydrous pyrolysis,kinetic models,distributed activation energies,basin modelling
AI 理解论文
溯源树
样例
生成溯源树,研究论文发展脉络