Seismicity at Newdigate, Surrey, during 2018-2019: A candidate mechanism indicating causation by nearby oil production

Westaway, R. (2021) Seismicity at Newdigate, Surrey, during 2018-2019: A candidate mechanism indicating causation by nearby oil production. In: Salazar, W. (ed.) Earthquakes - From Tectonics to Buildings. IntechOpen. ISBN 9781839624247 (doi: 10.5772/intechopen.94923)

[img] Text
227098.pdf - Published Version
Available under License Creative Commons Attribution.

9MB
[img] Text
227098Suppl.pdf - Supplemental Material

1MB

Abstract

During 2018–2019, oil was intermittently produced from the Late Jurassic Upper Portland Sandstone in the Weald Basin, southeast England, via the Horse Hill-1 and Brockham-X2Y wells. Concurrently, a sequence of earthquakes of magnitude ≤3.25 occurred near Newdigate, ∼3 km and ∼8 km from these wells. The pattern, with earthquakes concentrated during production from this Portland reservoir, suggests a cause-and-effect connection. It is proposed that this seismicity occurred on a patch of fault transecting permeable Dinantian limestone, beneath the Jurassic succession of the Weald Basin, hydraulically connected to this reservoir via this permeable fault and the permeable calcite ‘beef’ fabric within the Portland sandstone; oil production depressurizes this reservoir and draws groundwater from the limestone, compacting it and ‘unclamping’ the fault, reaching the Mohr-Coulomb failure criterion and causing seismicity. In principle this model is fully testable, but required data, notably the history of pressure variations in the wells, are not currently in the public domain. Quantitative estimates are, nonetheless, made of the magnitudes of the variations, arising from production from each well, in the state of stress on the seismogenic Newdigate fault. The general principles of this model, including the incorporation of poroelastic effects and effects of fault asperities into Mohr-Coulomb failure calculations, may inform understanding of anthropogenic seismicity in other settings.

Item Type:Book Sections
Status:Published
Glasgow Author(s) Enlighten ID:Westaway, Dr Robert
Authors: Westaway, R.
College/School:College of Science and Engineering > School of Engineering > Systems Power and Energy
Publisher:IntechOpen
ISBN:9781839624247
Published Online:19 April 2021
Copyright Holders:Copyright © 2021 The Author
Publisher Policy:Reproduced under a Creative Commons License

University Staff: Request a correction | Enlighten Editors: Update this record