• DOI:10.2138/RMG.2013.75.14
• Corpus ID: 27486837

On the Origins of Deep Hydrocarbons

@article{Sephton2013OnTO,
  title={On the Origins of Deep Hydrocarbons},
  author={Mark A. Sephton and Robert M. Hazen},
  journal={Reviews in Mineralogy \& Geochemistry},
  year={2013},
  volume={75},
  pages={449-465}
}

• M. Sephton, R. Hazen
• Published 2013
• Geology
• Reviews in Mineralogy & Geochemistry

Deep deposits of hydrocarbons, including varied reservoirs of petroleum and natural gas, represent the most economically important component of the deep carbon cycle. Yet despite their intensive study and exploitation for more than a century, details of the origins of some deep hydrocarbons remain a matter of vocal debate in some scientific circles. This long and continuing history of controversy may surprise some readers, for the biogenic origins of “fossil fuels”—a principle buttressed by a vast primary scientific literature and established as textbook orthodoxy in North America and many other parts of the world—might appear to be settled fact. Nevertheless, conventional wisdom continues to be challenged by some scientists.

The principal objectives of this chapter are: (1) to review the overwhelming evidence for the biogenic origins of most known deep hydrocarbon reservoirs; (2) to present equally persuasive experimental, theoretical, and field evidence, which indicates that components of some deep hydrocarbon deposits appear to have an abiotic origin; and (3) to suggest future studies that might help to achieve a more nuanced resolution of this sometimes polarized topic.

### Types of hydrocarbons

Deep hydrocarbons include a rich diversity of organic chemical compounds in the form of petroleum deposits, including oil and gas in various reservoirs, bitumen in oil sands, coal and clathrate hydrates. The major gaseous hydrocarbons are the alkanes methane (natural gas, CH4), ethane (C2H6), propane (C3H8), and butane (C4H10). Liquid components of petroleum include a complex mixture primarily of linear and cyclic hydrocarbons from C5 to C17, as well as numerous other molecular species, while solid hydrocarbons include such broad categories as paraffin waxes (typically from C18 to C40). In addition, mature coal deposits sometimes hold a suite of unusual pure crystalline hydrocarbon phases and other organic minerals …