Formation of magnetic minerals at hydrocarbon-generation conditions

Abubakar, R., Muxworthy, A.R., Sephton, M.A., Southern, P., Watson, J.S., Fraser, A.J. and Almeida, T.P. (2015) Formation of magnetic minerals at hydrocarbon-generation conditions. Marine and Petroleum Geology, 68(A), pp. 509-519. (doi: 10.1016/j.marpetgeo.2015.10.003)

Abstract

In this paper, we report the pyrolysis and formation of magnetic minerals in three source rock samples from the Wessex Basin in Dorset, southern England. The experimental conditions in the laboratory recreated the catagenesis environment of oil source rocks. Magnetic analysis of both the heated and the unheated samples at room temperature and at very low-temperatures (5 K), coupled with transmission electron-microscopy imaging and X-ray analysis, revealed the formation of nanometre-sized (<10 nm), magnetic particles that varied across the rock samples analysed, but more importantly across the pyrolysis temperature range. Magnetic measurements demonstrated the formation of these magnetic minerals peaked at 250 °C for all rock samples and then decreased at 300 °C before rising again at 320 °C. The newly formed magnetic minerals are suggested to be primarily pyrrhotite, though magnetite and greigite are also thought to be present. The sizes of the magnetic minerals formed suggest a propensity to migrate together with oil potentially explaining the magnetic anomalies observed above and within oil fields.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Almeida, Dr Trevor
• Authors: Abubakar, R., Muxworthy, A.R., Sephton, M.A., Southern, P., Watson, J.S., Fraser, A.J., and Almeida, T.P.
• College/School: College of Science and Engineering > School of Physics and Astronomy
• Journal Name: Marine and Petroleum Geology
• Publisher: Elsevier Ltd
• ISSN: 0264-8172
• ISSN (Online): 1873-4073
• Copyright Holders: Copyright © 2015 Elsevier Ltd.
• First Published: First published in Marine and Petroleum Geology 68(A):509-519
• Publisher Policy: Reproduced under a Creative Commons License