Influence of carbonate facies on fault zone architecture |
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| Institution: | 1. School of Geosciences, King''s College, University of Aberdeen, Aberdeen AB24 3UE, UK;2. Department of Applied Geology, Curtin University, Bentley Campus, Perth, Western Australia 6845, Australia;3. TOTAL, CSTJF, Avenue Larribau, 64108 Pau Cedex, France;1. Dipartimento di Scienze della Terra, Università degli Studi La Sapienza, Piazzale Aldo Moro 5, 00185 Rome, Italy;2. Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata 605, 00143 Rome, Italy;3. Dipartimento di Fisica e Geologia, Università degli Studi di Perugia, Via Alessandro Pascoli, 06123 Perugia, Italy;1. Université Paris Sud Orsay, France;2. TOTAL EP, 64018, Pau, France;3. Scuola di Scienze e Tecnologie, Sezione di Geologia, Università degli Studi di Camerino, via Gentile III da Varano, 62032, Camerino (MC), Italy;1. Dipartimento di Scienze della Terra, Sapienza Università di Roma, Italy;2. Consiglio delle Nazionale Ricerche, IGAG, Roma, Italy;1. School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, United Kingdom;2. Badley Geoscience Ltd, North Beck House, North Beck Lane, Hundleby, Spilsby, Lincolnshire, PE23 5NB, United Kingdom |
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| Abstract: | Normal faults on Malta were studied to analyse fault propagation and evolution in different carbonate facies. Deformation of carbonate facies is controlled by strength, particle size and pore structure. Different deformation styles influence the damage characteristics surrounding faults, and therefore the fault zone architecture. The carbonates were divided into grain- and micrite-dominated carbonate lithofacies. Stronger grain-dominated carbonates show localised deformation, whereas weaker micrite-dominated carbonates show distributed deformation. The weaker micrite-dominated carbonates overlie stronger grain-dominated carbonates, creating a mechanical stratigraphy. A different architecture of damage, the ‘Fracture Splay Zone’ (FSZ), is produced within micrite-dominated carbonates due to this mechanical stratigraphy. Strain accumulates at the point of juxtaposition between the stronger grain-dominated carbonates in the footwall block and the weaker micrite-dominated carbonates in the hanging wall block. New slip surfaces nucleate and grow from these points, developing an asymmetric fault damage zone segment. The development of more slip surfaces within a single fault zone forms a zone of intense deformation, bound between two slip surfaces within the micrite-dominated carbonate lithofacies (i.e., the FSZ). Rather than localisation onto a single slip surface, allowing formation of a continuous fault core, the deformation will be dispersed along several slip surfaces. The dispersed deformation can create a highly permeable zone, rather than a baffle/seal, in the micrite-dominated carbonate lithofacies. The formation of a Fracture Splay Zone will therefore affect the sealing potential of the fault zone. The FSZ, by contrast, is not observed in the majority of the grain-dominated carbonates. |
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| Keywords: | Fault zone architecture Carbonates Fault damage prediction Scaling attributes Normal faults Fluid flow |
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