Using quantitative X-ray diffraction phase analysis and pyrolysis gas chromatography, it was found that, regardless of the genetic type of naturally occurring organic matter (NOM), the principal phase generating C-1-C-7 hydrocarbons upon heating is the polynaphthene component, whose amount significantly decreases during pyrolysis. For NOM of biogenic and abiogenic origin, the ratio Of C-1-C-7 hydrocarbons is close to that found in the majority of crude oils.