AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
(1) Earth Science and Engineering, Imperial College London, London, United Kingdom.
Aeromagnetic surveys have discovered a link between magnetic anomalies and the presence of hydrocarbons. It was inferred that these anomalies were related to the migration of underlying hydrocarbon accumulations through faults causing the formation of magnetite through the reduction of iron hydroxides and hematite. Recently research has been conducted to characterize the magnetic minerals themselves, revealing an abundance of distinct magnetite framboids in association with large magnetic anomalies. However, we still do not understand how these minerals form in these environments and how they relate to the hydrocarbons.
The objectives of this research are to discover the origin of the magnetic minerals and what the relationship is between the biodegradation state of the oil and its magnetic signature. It also examines whether the magnetic minerals can be used as a proxy to identify migration distance.
Oil sands have been collected from near Wytch Farm oil field, Dorset, UK, as well as heavy oils from Alberta and bitumen from the Tar Tunnel in Shropshire, UK. Samples have also been acquired from drill cores from five oil fields in the North Sea, UK and the onshore oil field, Wytch Farm. Magnetic and electron microscopic characterisation of the samples have been used to determine the morphology, abundance, size and mineralogy of the magnetic minerals as well as controlled laboratory experiments to determine the mineral’s origins and biodegradation state. To analyse the oil sands, the oil was chemically extracted and the samples fractionated using column chromatography followed by gas-chromatography mass spectrometry analysis. Thermophilic iron-reducing bacteria were cultivated within the oil sands to determine the role of bacteria in the production of magnetite under different laboratory controlled conditions.