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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Main Author: Ellen, Rachael
Published: University of Strathclyde 2012
Subjects:
624
Online Access:http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.665208
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spelling ndltd-bl.uk-oai-ethos.bl.uk-6652082015-12-03T03:51:37ZPredicting the internal structure of fault zones in basalt sequences, and their effect on along- and across-fault fluid flowEllen, Rachael2012Interest 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.624University of Strathclydehttp://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.665208http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=25466Electronic Thesis or Dissertation
collection NDLTD
sources NDLTD
topic 624
spellingShingle 624
Ellen, Rachael
Predicting the internal structure of fault zones in basalt sequences, and their effect on along- and across-fault fluid flow
description 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.
author Ellen, Rachael
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
publisher University of Strathclyde
publishDate 2012
url http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.665208
work_keys_str_mv AT ellenrachael predictingtheinternalstructureoffaultzonesinbasaltsequencesandtheireffectonalongandacrossfaultfluidflow
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