A magnetic solution to the Mupe Bay mystery

Emmerton, Stacey; Muxworthy, Adrian R.; Sephton, Mark A.

doi:10.1016/j.marpetgeo.2013.06.014

Cited by 5 publications

(1 citation statement)

References 25 publications

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“…Hydrocarbons are known to cause reducing conditions at shallow depths that can chemically alter iron-bearing minerals to form authigenic iron oxides and/or sulphides (Reynolds et al 1990;Burton et al 1993). These iron minerals are sometimes ferromagnetic (sensu lato) like magnetite, pyrrhotite and greigite, though they can also be nonferromagnetic such as pyrite and siderite (Costanzo-Alvarez et al 2000;Aldana et al 2011;Emmerton et al 2013a;Badejo et al 2021b). The resulting balance of iron-rich minerals is dependent on the local environment, which can lead to both positive or negative magnetic anomalies or no change in contrast (McCabe et al 1987;Elmore et al 1993).…”

Section: Introductionmentioning

confidence: 99%

Using magnetic techniques to calibrate hydrocarbon migration in petroleum systems modelling: A Case Study from the Lower Tertiary, UK Central North Sea

Badejo

Muxworthy

Fraser

et al. 2021

Geophysical Journal International

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Summary Magnetic minerals form or alter in the presence of hydrocarbons, making them a potential magnetic proxy for identifying hydrocarbon migration pathways. In this paper we test this idea by magnetically measuring core samples from the Tay Fan in the Western Central Graben in the Central North Sea. In a companion paper, 3D petroleum systems modelling has been carried out to forward model migration pathways within the Tay Fan. Rock magnetic experiments identified a range of magnetite, maghemite, iron sulphides, siderite, goethite and titanohematite, some of which are part of the background signal, and some due to the presence of hydrocarbons. Typical concentrations of the magnetic minerals were ∼10–200 ppm. Importantly, we have identified an increasing presence of authigenic iron sulphides (likely pyrite and greigite) along the identified lateral hydrocarbon migration pathway (east to west). This is likely caused by biodegradation resulting in the precipitation of iron sulphides, however, though less likely, it could alternatively be caused by mature oil generation, which subsequently travelled with the migrating oil to the traps in the west. These observations suggest mineral magnetic techniques could be a rapid alternative method for identifying the severity of biodegradation or oil maturity in core sample, which can then be used to calibrate petroleum systems models.

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