The mechanics of clay smearing along faults

A clay- or shale-rich fault gouge can significantly reduce fault permeability. Therefore, predictions of the volume of clay or shale that may be smeared along a fault trace are important for estimating the fluid connectivity of groundwater and hydrocarbon reservoir systems. Here, we show how fault smears develop spontaneously in layered soil systems with varying friction coefficients, and we present a quantitative dynamic model for such behavior. The model is based on Mohr-Coulomb failure theory, and using discrete element computations, we demonstrate how the model framework can predict the fault smear potential from soil friction angles and layer thicknesses.

[1]  R. Knipe,et al.  Shear-zone geometries in experimentally deformed clays: the influence of water content, strain rate and primary fabric , 1988 .

[2]  P. Cundall,et al.  A discrete numerical model for granular assemblies , 1979 .

[3]  J. Urai,et al.  Processes of normal fault evolution in a siliciclastic sequence: a case study from Miri, Sarawak, Malaysia , 2005 .

[4]  F. Lehner,et al.  The emplacement of clay smears in synsedimentary normal faults: inferences from field observations near Frechen, Germany , 1997 .

[5]  Andy Chadwick,et al.  Modelling carbon-dioxide accumulation at Sleipner: implications for underground carbon storage , 2007 .

[6]  G. Gudehus,et al.  Hypoplastic simulation of normal faults without and with clay smears , 2007 .

[7]  S. Hotha,et al.  Shear localisation and strain distribution during tectonic faulting — new insights from granular-flow experiments and high-resolution optical image correlation techniques , 2004 .

[8]  V. Bense,et al.  Deformation mechanisms and hydraulic properties of fault zones in unconsolidated sediments; the Roer Valley Rift System, The Netherlands , 2003 .

[9]  B. Freeman,et al.  Quantitative Fault Seal Prediction , 1997 .

[10]  D. Peacock,et al.  Field examples and numerical modelling of oversteps and bends along normal faults in cross-section , 1994 .

[11]  R. Gabrielsen,et al.  Parameters that control the development of clay smear at low stress states: an experimental study using ring-shear apparatus , 2002 .

[12]  J. Urai,et al.  Lateral clay injection into normal faults , 2003, GeoArabia.

[13]  James P. Evans,et al.  Fault zone architecture and permeability structure , 1996 .

[14]  M. Person,et al.  Faults as conduit‐barrier systems to fluid flow in siliciclastic sedimentary aquifers , 2006 .

[15]  R. Gabrielsen,et al.  Experiments on clay smear formation along faults , 2000, Petroleum Geoscience.

[16]  A. Nicol,et al.  Growth of vertically segmented normal faults , 1996 .

[17]  Mike Sandiford,et al.  A new strategy for discrete element numerical models: 2. Sandbox applications , 2007 .

[18]  G. Mandl.  Faulting in Brittle Rocks: An Introduction to the Mechanics of Tectonic Faults , 1999 .

[19]  J. R. Fulljames,et al.  Fault seal processes: systematic analysis of fault seals over geological and production time scales , 1997 .

[20]  J. Walsh,et al.  Outcrop Studies of Shale Smears on Fault Surface , 2009 .