Natural fractures in a United Kingdom shale reservoir analog, Cleveland Basin, northeast England
Trabucho-Alexandre, Joao; Imber, Jonathan; Armstrong, Howard; Clancy, Sarah; Daniels, Susan; Herringshaw, Liam; McCaffrey, Ken; Rodrigues, Joel; Trabucho-Alexandre, João; Warren, Cassandra
Dr Liam Herringshaw L.Herringshaw@hull.ac.uk
Lecturer in Geology / Director of Admissions for Geography, Geology & Environment
Faults and fractures within the well-exposed Lower Jurassic Cleveland Ironstone and Whitby Mudstone Formations may provide insights into the tectonic history of gas-prospective, Mississippian shale in northern England. Subvertical opening mode fractures occur throughout the Cleveland Basin. Bed-parallel fractures, some of which contain blocky calcite fills, occur preferentially within well-bedded, clay-rich mudstones of the Cleveland Ironstone and Whitby Mudstone Formations at Jet Wyke and Port Mulgrave. Subvertical fractures display abutting or curving-parallel relationships with under- and overlying bed-parallel fractures. Together, these observations suggest that bed-parallel fractures, at times, acted as free surfaces. Some bed-parallel fractures curve toward and branch from calcite-filled fault slip surfaces, indicating that bed-parallel fracturing and normal faulting were synchronous, occurring within a regional stress field with vertical maximum principal stress. This apparent paradox can be explained by normal compaction, followed by cementation and coupling between pore pressure and minimum horizontal stress driven by poroelastic deformation or incipient slip along critically stressed normal faults, causing elevation of horizontal stress in excess of the vertical stress within clay-rich units. Propagation of bed-parallel fractures was enhanced by dilatational strains adjacent to normal fault planes. Bed-parallel fractures have not been observed within more SiO₂-rich units at the top of the Whitby Mudstone Formation at Whitby East Cliff, or within well-bedded, clay-rich shale at Saltwick Nab. This observation is consistent with the lack of normal faulting at Saltwick Nab, and the Whitby Mudstone Formation having been drained by structural and/or stratigraphical juxtaposition against permeable Middle Jurassic sandstones at both these localities.
|Publisher||American Association of Petroleum Geologists|
|Peer Reviewed||Peer Reviewed|
|APA6 Citation||Imber, J., Armstrong, H., Clancy, S., Daniels, S., Herringshaw, L., McCaffrey, K., …Warren, C. (2014). Natural fractures in a United Kingdom shale reservoir analog, Cleveland Basin, northeast England. AAPG Bulletin, 98(11), 2411-2437. https://doi.org/10.1306/07141413144|
|Keywords||Fuel Technology; Earth and Planetary Sciences (miscellaneous); Energy Engineering and Power Technology; Geology; Geochemistry and Petrology|
|Copyright Statement||Creative Commons Licence: Attribution 4.0 International License. See: http://creativecommons.org/licenses/by/4.0/|
|Additional Information||Author's accepted manuscript of article published in: AAPG bulletin, 2014, v.98, issue 11|
Creative Commons Licence: Attribution 4.0 International License. See: http://creativecommons.org/licenses/by/4.0/
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