HR: 17:00h
AN: T54A-05 INVITED    [Abstracts]
TI: The Structure and Fluid Flow Properties of Fault Zones: Inferences from Combined Field and Laboratory Studies
AU: * Faulkner, D
EM: faulkner@liverpool.ac.uk
AF: University of Liverpool, Dept of Earth and Ocean Sciences 4 Brownlow Street, Liverpool, L69 3GP, United Kingdom
AU: Mitchell, T
EM: t.mitchell@liverpool.ac.uk
AF: University of Liverpool, Dept of Earth and Ocean Sciences 4 Brownlow Street, Liverpool, L69 3GP, United Kingdom
AB: Quantifying the fluid flow properties of fault zones is important for understanding fault zone mechanics, predicting the distribution of fault-hosted economic deposits, and recovering hydrocarbons from structurally complex reservoirs. The fluid flow properties depend on the distribution of deformation within fault zones and the permeability of the individual fault components. The fault core can be a single, narrow zone of fault gouge, or consist of multiple strands with variably fractured lenses of country rock contained within them. Either structure will inhibit fluid flow across the fault zone, as typical laboratory values for the permeability of fault gouges in this direction is in the range 10^-18 to 10^-22 m². The multiple strand fault core provides the greatest opportunities for fluid entrapment. Although fault gouge exhibits significant permeability anisotropy (up to 3 orders of magnitude), fluid flow rates parallel to the fault within the fault core will still be low. Field, seismological and geophysical observations suggest that faults act as significant fluid conduits, and hence the zone of fractured rock surrounding the fault core (the damage zone) must act as a high permeability pathway. The damage zone consists of microscopic and macroscopic fracturing that decreases in intensity with distance from the fault core. In order to quantify the contribution of microscopic damage to the fluid flow properties, we measured the porosity and permeability evolution of initially low porosity crystalline rocks under simulated crustal conditions during progressive deformation to failure. The data show permeability enhancement from initial values of ~10^{- 21} to ~10^-17 immediately prior to failure. However, these values and the size of damage zones typically seen in the field are not sufficient to explain inferred fluid flow rates and imply that the macroscopic fracture network must play a significant role in fluid transport.
DE: 5104 Fracture and flow
DE: 5114 Permeability and porosity
DE: 5139 Transport properties
DE: 8010 Fractures and faults
DE: 8118 Dynamics and mechanics of faulting (8004)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting