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Analysis of deformation bands associated with the Trachyte Mesa intrusion, Henry Mountains, Utah: Implications for reservoir connectivity and fluid flow around sill intrusions

Analysis of deformation bands associated with the Trachyte Mesa intrusion, Henry Mountains, Utah: Implications for reservoir connectivity and fluid flow around sill intrusions
Analysis of deformation bands associated with the Trachyte Mesa intrusion, Henry Mountains, Utah: Implications for reservoir connectivity and fluid flow around sill intrusions

pShallow-level igneous intrusions are a common feature of many sedimentary basins, and there is increased recognition of the syn-emplacement deformation structures in the host rock that help to accommodate this magma addition. However, the sub-seismic structure and reservoir-scale implications of igneous intrusions remain poorly understood. The Trachyte Mesa intrusion is a small (span classCombining double low lineinline-formulag1/41.5/span kmspan classCombining double low lineinline-formula2/span), NE-SW trending satellite intrusion to the Oligocene-Age Mount Hillers intrusive complex in the Henry Mountains, Utah. It is emplaced within the highly porous, aeolian Entrada Sandstone Formation (Jurassic), producing a network of conjugate sets of NE-SW striking deformation bands trending parallel to the intrusion margins. The network was characterized by defining a series of nodes and branches, from which the topology, frequency, intensity, spacing, characteristic length, and dimensionless intensity of the deformation band traces and branches were determined. These quantitative geometric and topological measures were supplemented by petrological, porosity and microstructural analyses. Results show a marked increase in deformation band intensity and significant porosity reduction with increasing proximity to the intrusion. The deformation bands are likely to impede fluid flow, forming barriers and baffles within the Entrada reservoir unit. A corresponding increase in Y-and X-nodes highlights the significant increase in deformation band connectivity, which in turn will significantly reduce the permeability of the sandstone. This study indicates that fluid flow in deformed host rocks around igneous bodies may vary significantly from that in the undeformed host rock. A better understanding of the variability of deformation structures, and their association with intrusion geometry, will have important implications for industries where fluid flow within naturally fractured reservoirs adds value (e.g. hydrocarbon reservoir deliverability, hydrology, geothermal energy and carbon sequestration)./p.

1869-9510
95-117
Wilson, Penelope I. R.
9c47eb2d-b8b9-46df-9bc5-ea52f6f0b329
Wilson, Robert W.
06b8e0d9-8f5e-451a-81c3-d376a4a99403
Sanderson, David J.
5653bc11-b905-4985-8c16-c655b2170ba9
Jarvis, Ian
ce42268d-7217-42c9-8fdc-e11f74c504f6
Mccaffrey, Kenneth J. W.
6a08843c-2bfd-485c-a2f0-1df2d7275767
Wilson, Penelope I. R.
9c47eb2d-b8b9-46df-9bc5-ea52f6f0b329
Wilson, Robert W.
06b8e0d9-8f5e-451a-81c3-d376a4a99403
Sanderson, David J.
5653bc11-b905-4985-8c16-c655b2170ba9
Jarvis, Ian
ce42268d-7217-42c9-8fdc-e11f74c504f6
Mccaffrey, Kenneth J. W.
6a08843c-2bfd-485c-a2f0-1df2d7275767

Wilson, Penelope I. R., Wilson, Robert W., Sanderson, David J., Jarvis, Ian and Mccaffrey, Kenneth J. W. (2021) Analysis of deformation bands associated with the Trachyte Mesa intrusion, Henry Mountains, Utah: Implications for reservoir connectivity and fluid flow around sill intrusions. Solid Earth, 12 (1), 95-117. (doi:10.5194/se-12-95-2021).

Record type: Article

Abstract

pShallow-level igneous intrusions are a common feature of many sedimentary basins, and there is increased recognition of the syn-emplacement deformation structures in the host rock that help to accommodate this magma addition. However, the sub-seismic structure and reservoir-scale implications of igneous intrusions remain poorly understood. The Trachyte Mesa intrusion is a small (span classCombining double low lineinline-formulag1/41.5/span kmspan classCombining double low lineinline-formula2/span), NE-SW trending satellite intrusion to the Oligocene-Age Mount Hillers intrusive complex in the Henry Mountains, Utah. It is emplaced within the highly porous, aeolian Entrada Sandstone Formation (Jurassic), producing a network of conjugate sets of NE-SW striking deformation bands trending parallel to the intrusion margins. The network was characterized by defining a series of nodes and branches, from which the topology, frequency, intensity, spacing, characteristic length, and dimensionless intensity of the deformation band traces and branches were determined. These quantitative geometric and topological measures were supplemented by petrological, porosity and microstructural analyses. Results show a marked increase in deformation band intensity and significant porosity reduction with increasing proximity to the intrusion. The deformation bands are likely to impede fluid flow, forming barriers and baffles within the Entrada reservoir unit. A corresponding increase in Y-and X-nodes highlights the significant increase in deformation band connectivity, which in turn will significantly reduce the permeability of the sandstone. This study indicates that fluid flow in deformed host rocks around igneous bodies may vary significantly from that in the undeformed host rock. A better understanding of the variability of deformation structures, and their association with intrusion geometry, will have important implications for industries where fluid flow within naturally fractured reservoirs adds value (e.g. hydrocarbon reservoir deliverability, hydrology, geothermal energy and carbon sequestration)./p.

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Accepted/In Press date: 12 November 2020
Published date: 20 January 2021

Identifiers

Local EPrints ID: 447171
URI: http://eprints.soton.ac.uk/id/eprint/447171
ISSN: 1869-9510
PURE UUID: 068b8ba7-b2ab-4c53-90e0-3b59657f33bc
ORCID for David J. Sanderson: ORCID iD orcid.org/0000-0002-2144-3527

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Date deposited: 04 Mar 2021 17:39
Last modified: 26 Nov 2021 02:53

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Author: Penelope I. R. Wilson
Author: Robert W. Wilson
Author: Ian Jarvis
Author: Kenneth J. W. Mccaffrey

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