The Evolution of Multicomponent Systems at High Pressures: VI. The Thermodynamic Stability of the Hydrogen-Carbon System: The Genesis of Hydrocarbons and the Origin of Petroleum

摘要

The spontaneous genesis of hydrocarbons which comprise natural petroleum havebeen analyzed by chemical thermodynamic stability theory. The constraintsimposed upon chemical evolution by the second law of thermodynamics are brieflyreviewed; and the effective prohibition of transformation, in the regime oftemperatures and pressures characteristic of the near-surface crust of theEarth, of biological molecules into hydrocarbon molecules heavier than methaneis recognized. A general, first-principles equation of state has been developed by extendingscaled particle theory (SPT) and by using the technique of the factoredpartition function of the Simplified Perturbed Hard Chain Theory (SPHCT). Thechemical potentials, and the respective thermodynamic Affinity, have beencalculated for typical components of the hydrogen-carbon (H-C) system over arange pressures between 1-100 kbar, and at temperatures consistent with thoseof the depths of the Earth at such pressures. The theoretical analysesestablish that the normal alkanes, the homologous hydrocarbon group of lowestchemical potential, evolve only at pressures greater than approximately thirtykbar, excepting only the lightest, methane. The pressure of thirty kbarcorresponds to depths of approximately 100 km. Special high-pressure apparatus has been designed which permitsinvestigations at pressures to 50 kbar and temperatures to 2000 K, and whichalso allows rapid cooling while maintaining high pressures. The high-pressuregenesis of petroleum hydrocarbons has been demonstrated using only the solidreagents iron oxide, FeO, and marble, CaCO3, 99.9% pure and wet withtriple-distilled water.