Kerogen maturation and petroleum genesis

Abstract

KEROGEN, the non-extractable organic matter in recent and ancient sediments, has been studied extensively for its importance in petroleum genesis. However, the chemistry of kerogen is not clear because of its highly-polymerised and complicated structure. Elemental analysis, especially of carbon, hydrogen and oxygen, is the most fundamental method of characterising kerogens, and a C–H–O diagram can be effectively used for their classification1–4. The progressive changes of chemical composition of kerogens with depth of sediments which take place release CO2, H2O, and liquid and gaseous hydrocarbons. This process kerogen maturation2, increases the carbon content of kerogen, and eventually forms graphite. Although the carbon content of kerogen increases as CO2 and/or H2O is released, the generation of hydrocarbons will reduce the carbon content. Therefore, it is important to examine the compositional change of kerogens as they release CO2, H2O and hydrocarbons, respectively. This paper discusses kerogen maturation in relation to petroleum genesis on a three component (C, H and O) diagram.