HR: 1340h
AN: T33C-1502    [Abstracts]
TI: Deformation Bands: Strain Localization Structures in Highly Porous Sandstone
AU: Fossen, H
EM: Haakon.fossen@geo.uib.no
AF: Centre of Integrated Petroleum Research, University of Bergen, Allegaten 41, Bergen, 50007, Norway
AU: Schultz, R A
EM: schultz@mines.unr.edu
AF: University of Nevada, Rock Fracture Group, Department of Geological Sciences and Engineering, Reno, NV 89557, United States
AU: Shipton, Z K
EM: Zoe.Shipton@ges.gla.ac.uk
AF: Department of Geographical and Earth Sciences, University of Glasgow, Glasgow, G12 8QQ, United Kingdom
AU: * Mair, K
EM: karen.mair@fys.uio.no
AF: Physics of Geological Processes, University of Oslo, PO Box 1048, Blindern, Oslo, 0316, Norway
AB: Deformation bands are the most common strain localization feature found in deformed porous sandstones and sediments, including Quaternary deposits, soft gravity slides and tectonically affected sandstones in hydrocarbon reservoirs and aquifers. They occur as various types of tabular deformation zones where grain reorganization occurs by grain sliding, rotation and/or fracture during overall dilation, shearing, and/or compaction. These structures form in rocks and sediments where porosity exceeds approximately 15 percent, where the pore space allows for a more flexible grain reorganization that that seen in non- and low-porosity rocks. Deformation bands with a significant component of shear are most common and typically accommodate shear offsets of millimeters to centimeters. They can occur as single structures or cluster zones, and are the main deformation element of fault damage zones in porous rocks. Factors such as porosity, mineralogy, grain size and shape, lithification, state of stress and burial depth control the type of deformation band formed. The different types are controlled by deformation mechanisms: cataclasis, rigid grain reorganization (granular flow) and cementation and/or dissolution (wet diffusion). Most bands show a reduction in porosity and permeability, usually between 0 and 3 orders of magnitude. Of the different types, phyllosilicate bands and most notably cataclastic deformation bands show the largest reduction in permeability, and thus have the greatest potential to influence fluid flow. This is particularly so where the bands occur in clusters, and if dissolution accompanies the cataclasis. Disaggregation bands, where non-cataclastic, granular flow is the dominant mechanism, show less influence on fluid flow unless assisted by chemical compaction or cementation.
DE: 8010 Fractures and faults
DE: 8118 Dynamics and mechanics of faulting (8004)
DE: 8163 Rheology and friction of fault zones (8034)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting