LARTER, STEPHEN R., ANDY APLIN, JASON DALE, PAUL TAYLOR, BARRY BENNETT, MARTIN JONES, KIM NOKE and ANDY MORT
Fossil Fuels and Environmental Geochemistry Postgraduate Institutem, NRG, University of Newcastle, Newcastle Upon Tyne, UK

Abstract: Origin, Systematics and Geological Applications of Alkylphenols in Petroleum-Water Systems

The application of dissolved organic solutes to exploration (proximity and nature of undiscovered petroleum, migration range) and perhaps production (compartmentalisation, natural tracers of water floods, unswept oil) rests on an understanding of their origin and geochemical fate. Here, we present alkylphenol data from source rocks, petroleums and waters from North Sea North American and Asian basins. Alkylphenols are generated in source rocks by alkylation/isomerisation of unspecific aromatic precursors. Initial distributions and concentrations of alkylphenols depend on oil maturity but to a much lesser extent ,on source facies. Migration results in a decline in the absolute abundances of individual compounds but little change in the distribution of homologues. These trends are consistent with the three way partition of phenols between petroleum, water and mineral surfaces. The limited extent of phenol loss along migration pathways suggests that petroleum migrates through a small fraction of available porespace. C₀-C₂ alkylphenols occur in ppm concentrations in reservoir waters and appear to be in partition equilibrium with coexisting petroleum. Principal controls of the oil-water partition coefficients are temperature, salinity and the abundance of non-hydrocarbons in petroleum. Biodegradation both destroys and produces alkylphenols. However, aqueous alkylphenols can indicate to what extent the in-reservoir destruction of crude oil was driven by biodegradation or penecontemporaneous water washing.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas