Predicting the internal structure of fault zones in basalt sequences, and their effect on along- and across-fault fluid flow
Interest in the architecture and fluid flow potential of fault zones in basalt sequences has intensified over recent years, due to their applications in the hydrocarbon industry and CO₂ storage. In this study, field mapping is combined with micro-structural analyses and flow modelling to evaluate fa...
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ftunsthclydestax:oai:strathclyde:cf95jb452 2023-05-15T17:36:48+02:00 Predicting the internal structure of fault zones in basalt sequences, and their effect on along- and across-fault fluid flow Ellen, Rachael. 2012 https://doi.org/10.48730/daf2-ba75 https://stax.strath.ac.uk/concern/theses/cf95jb452 unknown https://stax.strath.ac.uk/downloads/gm80hv700 T13447 https://stax.strath.ac.uk/thesis_copyright_statement http://purl.org/coar/resource_type/c_db06 2012 ftunsthclydestax https://doi.org/10.48730/daf2-ba75 2021-12-20T08:45:56Z Interest in the architecture and fluid flow potential of fault zones in basalt sequences has intensified over recent years, due to their applications in the hydrocarbon industry and CO₂ storage. In this study, field mapping is combined with micro-structural analyses and flow modelling to evaluate fault growth, evolution, fluid-rock interactions, and permeability changes over time in faults in basalt sequences. Twelve brittle fault zones cutting basalt sequences in the North Atlantic Igneous Province were studied. This study finds that fault architecture is ultimately controlled by displacement and juxtaposition. Self-juxtaposed faults (i.e. basalt faulted against itself) are characterised by wide zones of brecciation, cataclasis, fracturing, mineralisation and alteration. Non self-juxtaposed faults (i.e. basalt faulted against an inter-lava unit) are characterised by relatively narrow principal slip zones, filled with clay smears or clay-rich gouge derived from inter-lava beds. This study also finds that brittle deformation of basalts at the grain scale is mineralogy dependent. Fe-Ti oxides and pyroxenes deform by intragranular fracturing and grain size reduction, whereas olivines and feldspars are susceptible to replacement by clay and zeolites. Fault rock bulk chemistries are likely to differ from their host rocks, and this is controlled by secondary mineral formation, with zeolite and clay minerals playing an important role. Flow modelling in this study shows that controls on along- and across-fault fluid flow can significantly change fault zone bulk permeability over time, as a result of mineralisation and alteration of the fault zone as it evolves. The results from this study are used to propose a model for how fault strength, fault-related alteration, and permeability change over time in fault zones in basalt sequences. Results highlight the impact that fault-related alteration could have on CO₂ storage. A predictive model for fault structure at depth, developed from this study's findings, is presented for fault zones in basalt sequences, which has particular relevance to the hydrocarbon and CO₂ industry. Other/Unknown Material North Atlantic University of Strathclyde Glasgow: STAX |
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University of Strathclyde Glasgow: STAX |
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Interest in the architecture and fluid flow potential of fault zones in basalt sequences has intensified over recent years, due to their applications in the hydrocarbon industry and CO₂ storage. In this study, field mapping is combined with micro-structural analyses and flow modelling to evaluate fault growth, evolution, fluid-rock interactions, and permeability changes over time in faults in basalt sequences. Twelve brittle fault zones cutting basalt sequences in the North Atlantic Igneous Province were studied. This study finds that fault architecture is ultimately controlled by displacement and juxtaposition. Self-juxtaposed faults (i.e. basalt faulted against itself) are characterised by wide zones of brecciation, cataclasis, fracturing, mineralisation and alteration. Non self-juxtaposed faults (i.e. basalt faulted against an inter-lava unit) are characterised by relatively narrow principal slip zones, filled with clay smears or clay-rich gouge derived from inter-lava beds. This study also finds that brittle deformation of basalts at the grain scale is mineralogy dependent. Fe-Ti oxides and pyroxenes deform by intragranular fracturing and grain size reduction, whereas olivines and feldspars are susceptible to replacement by clay and zeolites. Fault rock bulk chemistries are likely to differ from their host rocks, and this is controlled by secondary mineral formation, with zeolite and clay minerals playing an important role. Flow modelling in this study shows that controls on along- and across-fault fluid flow can significantly change fault zone bulk permeability over time, as a result of mineralisation and alteration of the fault zone as it evolves. The results from this study are used to propose a model for how fault strength, fault-related alteration, and permeability change over time in fault zones in basalt sequences. Results highlight the impact that fault-related alteration could have on CO₂ storage. A predictive model for fault structure at depth, developed from this study's findings, is presented for fault zones in basalt sequences, which has particular relevance to the hydrocarbon and CO₂ industry. |
format |
Other/Unknown Material |
author |
Ellen, Rachael. |
spellingShingle |
Ellen, Rachael. Predicting the internal structure of fault zones in basalt sequences, and their effect on along- and across-fault fluid flow |
author_facet |
Ellen, Rachael. |
author_sort |
Ellen, Rachael. |
title |
Predicting the internal structure of fault zones in basalt sequences, and their effect on along- and across-fault fluid flow |
title_short |
Predicting the internal structure of fault zones in basalt sequences, and their effect on along- and across-fault fluid flow |
title_full |
Predicting the internal structure of fault zones in basalt sequences, and their effect on along- and across-fault fluid flow |
title_fullStr |
Predicting the internal structure of fault zones in basalt sequences, and their effect on along- and across-fault fluid flow |
title_full_unstemmed |
Predicting the internal structure of fault zones in basalt sequences, and their effect on along- and across-fault fluid flow |
title_sort |
predicting the internal structure of fault zones in basalt sequences, and their effect on along- and across-fault fluid flow |
publishDate |
2012 |
url |
https://doi.org/10.48730/daf2-ba75 https://stax.strath.ac.uk/concern/theses/cf95jb452 |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_relation |
https://stax.strath.ac.uk/downloads/gm80hv700 T13447 |
op_rights |
https://stax.strath.ac.uk/thesis_copyright_statement |
op_doi |
https://doi.org/10.48730/daf2-ba75 |
_version_ |
1766136404258062336 |