L. Stalker et al., WATER AS AN OXYGEN SOURCE FOR THE PRODUCTION OF OXYGENATED COMPOUNDS (INCLUDING CO2 PRECURSORS) DURING KEROGEN MATURATION, Organic geochemistry, 22(3-5), 1994, pp. 477-486
In order to study the generation of oxygen-rich species which may act
as CO2 precursors, the interaction of sedimentary organic matter and w
ater during hydrous pyrolysis has been investigated using O-18 labelle
d water. Model compound experiments were conducted with a series of co
mpounds (3,4-dimethylphenol, dodecanoic acid and xanthene) in order to
assess their levels of simple homogeneous exchange of oxygen with hot
water. While dodecanoic acid underwent extensive oxygen exchange (98%
), dimethylphenol underwent restricted oxygen exchange (13%) and xanth
ene showed no exchange. A comparison of the dimethylphenol model compo
und experiments in (H2O)-O-18 with dimethylphenols generated by Kimmer
idge Clay kerogen, under identical conditions, showed marked differenc
es in levels of O-18 incorporation (approx. 13% for the model compound
and 40% for the kerogen-derived products) suggesting neogenic phenol
formation during hydrous pyrolysis. The implications of this inferred
water oxygen addition to sedimentary organic matter during kerogen deg
radation will undoubtedly affect mass balance calculations of the gene
ration of oxygen-rich species from sedimentary organic matter and thus
have a potential impact on mass balance assessments of the generation
of CO2 and its precursors in petroleum basins. The results also have
major implications for oxygen mobility between organic matter and wate
r in hydrothermal systems and possibly for lower temperature reactions
in petroleum systems.