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Journal articleMuxworthy A, Lam C, Green D, et al., 2022,
Magnetic characterisation of London’s airborne nanoparticulate matter
, Atmospheric Environment, Vol: 287, Pages: 1-8, ISSN: 1352-2310Iron-bearing particulate matter produced by vehicle emissions is known to be toxic. To better quantify potential health risks, we have conducted the first magnetic study of a time-series of London's inhalable particulate matter (<10 μm, PM10), captured by three monitoring stations in central London (Marylebone Road, Earl's Court Road and Oxford Street) through 2010 and 2012. We conducted room-temperature analysis on all the samples, and a limited number of samples were analysed at both high and low temperatures. The high-temperature measurements identified magnetite as the dominant magnetic phase. The low-temperature measurements revealed high numbers of nanoparticles, which, assuming magnetite, are in the grain-size range 1–4 nm. It is estimated that as much as ∼40% of the total magnetic signal at 10 K is from particles <4 nm, that are magnetically ‘invisible’ at room-temperature and are being routinely under-estimated in room temperature-based magnetic studies. From the low-temperature measurements, the total concentration of magnetite was estimated at ∼7.5%, significantly higher than previously reported. The room-temperature magnetic data were compared with other pollution data, e.g., NOX and PM10, and meteorological data. Mass-dependent terms like the saturation magnetisation were found to display a strong correlation with NOX and PM10, indicating a common source for these pollutants, i.e., vehicle emissions. Magnetic coercivity measurements, which are independent of abundance, and provide information on grain-size, were consistent across all three sampling localities, again suggesting a major dominant source. Relatively small variations in coercivity were correlated with meteorological events, e.g., temperature and precipitation, suggesting preferential removal of larger airborne grains, i.e., >50 nm.
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Journal articleAbdulkarim M, Muxworthy AR, Fraser A, 2022,
High temperature susceptibility measurements: A potential tool for the identification of oil water transition zone (OWTZ) in petroleum reservoirs
, Frontiers in Earth Science, Vol: 10, ISSN: 2296-6463Determining the position and thickness of the oil water transition zone (OWTZ) in hydrocarbon reservoirs is important to reserveestimation and production planning. This paper describes a magnetic method of identifying this zone. High temperaturesusceptibility (HT‐χ) measurements on core samples from Paleogene reservoirs of the UK Central North Sea revealed distinctsignatures around the oil water interface. Rapid increases in susceptibilities at temperatures < 250 °C were observed forsamples around the oil water interface unlike the main oil leg where alteration involving increase in susceptibility occurred atsignificantly slower rates and higher temperatures. The HT‐χ data together with Mössbauer measurements revealed that thevariation in alteration characteristics is due to the increasing concentration of hexagonal pyrrhotite and/or lepidocrocite aroundthe oil water interface. Hexagonal pyrrhotite was identified in reservoirs existing at temperatures of < 80 °C, whilelepidocrocite dominated the signature around the contact of deeper reservoirs. These observations suggest that the precipitationof hexagonal pyrrhotite is related to OWTZ centred biogenic activities i.e., biodegradation. The dominance of lepidocrocite indeeper diagenetic settings has been related to hydrolysis of hydrocarbon at the oil water interface, together with cessation ofbiogenic activities.
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Conference paperNorth TL, Muxworthy AR, Collins GS, et al., 2022,
THERMOREMANENT MAGNETISATION RECORDED DURING IMPACT-INDUCED COMPACTION EXPERIMENTS ON SYNTHETIC CHONDRITIC METEORITES
, LSPC, Publisher: WILEY, ISSN: 1086-9379 -
Journal articleAbdulkarim MA, Muxworthy A, Fraser A, et al., 2022,
Effect of hydrocarbon presence and properties on the magnetic signature of the reservoir sediments of the Catcher Area Development (CAD) region, UK North Sea
, Frontiers in Earth Science, Vol: 10, Pages: 1-20, ISSN: 2296-6463This paper presents a detailed study investigating the effect of hydrocarbon presence on magnetic mineral diagenesis in sediments from the Catcher Area Development (CAD) region, UK North Sea, between 1,000 and 1,500 m (True Vertical Depth Sub-Sea). Magnetic analysis of core samples from hydrocarbon fields of the region and nearby dry-well sandstones (background) was carried out to determine if their signatures can serve as a proxy for understanding petroleum reservoir systems. From the background samples, nanometric and micron-sized magnetite, hematite and titano-iron oxides, were identified. Hydrocarbon presence in the reservoir sediments was found to diminish the iron-oxide signature and favour the precipitation of hexagonal pyrrhotite, siderite and potentially vivianite, lepidocrocite, greigite and paramagnetic iron sulphides. Hexagonal pyrrhotite was found at the oil-water transition zones. This relationship is possibly related to biodegradation at this interface. Siderite was found in increased abundance at shallower depths within the reservoir, which we attribute to hydrocarbon vertical migration and biodegradation. The interbedded shales also experienced significant magnetic mineral diagenesis that depended on its proximity to the hydrocarbon plume. These findings suggest that mineral magnetism can be applied to the identification of oil-water transition zones, reserve estimation, production planning and the determination of hydrocarbon migration pathways. It also suggests that mineral magnetic methods can be used to estimate the timing of hydrocarbon migration.
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Journal articleRoberts AP, Heslop D, Zhao X, et al., 2022,
Unlocking information about fine magnetic particle assemblages from first-order reversal curve diagrams: Recent advances
, EARTH-SCIENCE REVIEWS, Vol: 227, ISSN: 0012-8252 -
Journal articleAbdulkarim M, Muxworthy A, Fraser A, et al., 2022,
Siderite occurrence in petroleum systems and its potential as a hydrocarbon-migration proxy: a case study of the Catcher Area Development and the Bittern area, UK North Sea
, Journal of Petroleum Science and Engineering, ISSN: 0920-4105 -
Journal articleRoberts AP, Zhao X, Hu P, et al., 2021,
Magnetic domain state and anisotropy in hematite (alpha-Fe2O3) from first-order reversal curve diagrams
, Journal of Geophysical Research. Solid Earth, ISSN: 2169-9356 -
Journal articleMuxworthy A, Baker E, 2021,
ThellierCoolPy: A cooling-rate correction tool for paleointensity data
, G3: Geochemistry, Geophysics, Geosystems: an electronic journal of the earth sciences, Vol: 22, Pages: 1-8, ISSN: 1525-2027We report a new approach of implementing cooling-rate corrections in absolute ancient magnetic field intensity (paleointensity) studies. Nearly all methods of determining paleointensity estimates rely on rocks having recorded a thermoremanent magnetization (TRM), on cooling from above the rock’s constituent minerals’ Curie temperature. Typically paleointensity estimates are made by comparing natural TRM, with a TRM induced in the laboratory; however, TRM intensity has long been reported to be dependent on cooling rate. Natural cooling rates are impractical in laboratories. We have developed a new cooling-rate correction method and corresponding software (ThellierCoolPy), that directly corrects the unprocessed paleointensity data, using first-order reversal curve data collected on a sister sample. This site tailored cooling-rate correction has a unique correction for each temperature step within the paleointensity data set. This new method differs from previous approaches which apply a blanket cooling-rate correction independent of the material properties of the sample. Paleointensity data from historical lavas from Parícutin, Mexico, are used to demonstrate the new software. For this data set, it is shown that cooling time of 1 million years yields a reduction of the paleointensity of ∼7%. The software is available for download.
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Journal articleNoble JPP, Bending SJ, Sartbaeva A, et al., 2021,
A Novel In Situ High-Temperature Magnetometry Method for Radiofrequency Heating Applications
, ADVANCED ENERGY MATERIALS, Vol: 12, ISSN: 1614-6832 -
Journal articleBadejo SA, Muxworthy A, Fraser A, et al., 2021,
Identification of magnetic enhancement at hydrocarbon/water contacts
, American Association of Petroleum Geologists (AAPG) Bulletin, Vol: 105, Pages: 1973-1991, ISSN: 0149-1423Identifying the depths of the hydrocarbon-fluid contacts in a reservoir is important for determining hydrocarbon reserves and production planning. Using core samples from the Tay sandstone reservoir in the Central North Sea, we show that thereis a magnetic enhancement at the hydrocarbon-fluid contacts, that is detectable both through magnetic susceptibility measurements and magnetic hysteresis measurements. We observed this magnetic enhancement at both gas-oil and oil-water contacts, that have been independently identified using non-magnetic methods; we did not consider gas-water contacts in this study. We demonstrate that this magnetic enhancement is due to the precipitation of new nanometric iron oxide (magnetite) and iron sulphide (greigite)phases. The magnetic enhancement may be caused by diagenetic changes or preferential biodegradation at the top of the oil column during early filling and at the oil water contact. Our findings have the potential to be used to identify paleo-hydrocarbon-fluid contact in both structurally modified fields and failed wells. The technique can also be used to infer the fill history of a basin and calibrate petroleum systems models. Magnetic susceptibility measurements have the advantage that they can easily and quickly be measured in the field on whole core-material.
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Journal articleBadejo SA, Muxworthy AR, Fraser A, et al., 2021,
Using magnetic techniques to calibrate hydrocarbon migration in petroleum systems modelling: A Case Study from the Lower Tertiary, UK Central North Sea
, Geophysical Journal International, Vol: 227, Pages: 617-631, ISSN: 0956-540XMagnetic 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, 3-D 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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Journal articleBadejo S, Fraser A, Neumaier M, et al., 2021,
3D Petroleum Systems Modelling as an exploration tool in mature basins: A study from the Central North Sea, UK.
, Marine and Petroleum Geology, ISSN: 0264-8172 -
Journal articleHu P, Oda H, Zhao X, et al., 2020,
Assessment of magnetic techniques for understanding complex mixtures of magnetite and hematite: the Inuyama red chert
, Journal of Geophysics Research - Solid Earth -
Conference paperAbdulkarim M, Muxworthy A, Fraser A, et al., 2021,
PRECIPITATION OF SIDERITE IN HYDROCARBON ENVIRONMENT
, Pages: 2417-2421Migration of hydrocarbons in the subsurface has been shown to create an environment that promotes the precipitation and/or alteration of magnetic minerals. For example, iron oxides and iron sulphides have been shown to precipitate due to the reducing conditions created by hydrocarbon migration. Siderite, a paramagnetic mineral with Neel temperature of 37K has been variously identified in hydrocarbon environment and has also been suggested to be an authigenic product of hydrocarbon migration. However, it is commonly found in sedimentary settings. Here we show via experimental studies that siderite is precipitated due to hydrocarbon migrations and suggested the mechanism responsible for this process. Magnetic minerals precipitation along migration pathways suggests the creation of a magnetic fingerprint that if thoroughly understood can be applied to oil and gas exploration.
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Journal articleChang L, Hong H, Bai F, et al., 2020,
Detrital remanent magnetization of single-crystal silicates with magnetic inclusions: constraints from deposition experiments
, Geophysical Journal International, ISSN: 0956-540X
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