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An enhanced understanding of the Basinal Bowland shale in Lancashire (UK), through microtextural and mineralogical observations

Fauchille, AL; Ma, L; Rutter, E; Chandler, M; Lee, PD; Taylor, KG; (2017) An enhanced understanding of the Basinal Bowland shale in Lancashire (UK), through microtextural and mineralogical observations. Marine and Petroleum Geology , 86 pp. 1374-1390. 10.1016/j.marpetgeo.2017.07.030. Green open access

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Abstract

Variability in the Lower Bowland shale microstructure is investigated here, for the first time, from the centimetre to the micrometre scale using optical and scanning electron microscopy (OM, SEM), X-Ray Diffraction (XRD) and Total Organic Carbon content (TOC) measurements. A significant range of microtextures, organic-matter particles and fracture styles was observed in rocks of the Lower Bowland shale, together with the underlying Pendleside Limestone and Worston Shale formations encountered the Preese Hall-1 Borehole, Lancashire, UK. Four micro-texture types were identified: unlaminated quartz-rich mudstone; interlaminated quartz- and pyrite-rich mudstone; laminated quartz and pyrite-rich mudstone; and weakly-interlaminated calcite-rich mudstone. Organic matter particles are classified into four types depending on their size, shape and location: multi-micrometre particles with and without macropores: micrometre-size particles in cement and between clay minerals; multi-micrometre layers; and organic matter in large pores. Fractures are categorized into carbonate-sealed fractures; bitumen-bearing fractures; resin-filled fractures; and empty fractures. We propose that during thermal maturation, horizontal bitumen-fractures were formed by overpressuring, stress relaxation, compaction and erosional offloading, whereas vertical bitumen-bearing, resin-filled and empty fractures may have been influenced by weak vertical joints generated during the previous period of veining. For the majority of samples, the high TOC (>2 wt%), low clay content (<20 wt%), high proportion of quartz (>50 wt%) and the presence of a multi-scale fracture network support the increasing interest in the Bowland Shale as a potentially exploitable oil and gas source. The microtextural observations made in this study highlight preliminary evidence of fluid passage or circulation in the Bowland Shale sequence during burial.

Type: Article
Title: An enhanced understanding of the Basinal Bowland shale in Lancashire (UK), through microtextural and mineralogical observations
Open access status: An open access version is available from UCL Discovery
DOI: 10.1016/j.marpetgeo.2017.07.030
Publisher version: https://doi.org/10.1016/j.marpetgeo.2017.07.030
Language: English
Additional information: This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/
Keywords: Science & Technology, Physical Sciences, Geosciences, Multidisciplinary, Geology, Bowland shale, Variability, Micro-texture, Organic matter, Fractures, Microscopy, Characterization, MISSISSIPPIAN BARNETT SHALE, NORTHEASTERN BRITISH-COLUMBIA, NORTH-CENTRAL TEXAS, FORT-WORTH BASIN, SEDIMENTARY BASINS, NATURAL FRACTURES, PENNINE BASIN, BLACK SHALES, GAS SYSTEMS, FLUID-FLOW
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Mechanical Engineering
URI: https://discovery.ucl.ac.uk/id/eprint/10049095
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