  The spontaneous genesis of hydrocarbons which comprise natural petroleum have
been analyzed by chemical thermodynamic stability theory. The constraints
imposed upon chemical evolution by the second law of thermodynamics are briefly
reviewed; and the effective prohibition of transformation, in the regime of
temperatures and pressures characteristic of the near-surface crust of the
Earth, of biological molecules into hydrocarbon molecules heavier than methane
is recognized.
  A general, first-principles equation of state has been developed by extending
scaled particle theory (SPT) and by using the technique of the factored
partition function of the Simplified Perturbed Hard Chain Theory (SPHCT). The
chemical potentials, and the respective thermodynamic Affinity, have been
calculated for typical components of the hydrogen-carbon (H-C) system over a
range pressures between 1-100 kbar, and at temperatures consistent with those
of the depths of the Earth at such pressures. The theoretical analyses
establish that the normal alkanes, the homologous hydrocarbon group of lowest
chemical potential, evolve only at pressures greater than approximately thirty
kbar, excepting only the lightest, methane. The pressure of thirty kbar
corresponds to depths of approximately 100 km.
  Special high-pressure apparatus has been designed which permits
investigations at pressures to 50 kbar and temperatures to 2000 K, and which
also allows rapid cooling while maintaining high pressures. The high-pressure
genesis of petroleum hydrocarbons has been demonstrated using only the solid
reagents iron oxide, FeO, and marble, CaCO3, 99.9% pure and wet with
triple-distilled water.
