HR: 14:40h
AN: H13I-05    [Abstracts]
TI: Mathematical Modelling of Hydraulic Permeability Evolution in the Damage Zone Surrounding Geological Faults
AU: * Willson, J P
EM: civjpw@hw.ac.uk
AF: Heriot-Watt University, Post Graduate, Arrol Building, School of the Built Environment, Edinburgh, EH14 4AS United Kingdom
AU: Lunn, R J
AF: Heriot-Watt University, Post Graduate, Arrol Building, School of the Built Environment, Edinburgh, EH14 4AS United Kingdom
AU: Cowie, P
AF: University of Edinburgh, Department of Geology & Geophysics, West Mains Road, Edinburgh, EH9 3JW United Kingdom
AB: Geological faults are planar structures, oriented in three-dimensional space, on which shear displacement has occurred. As the rock shears, the material within and around the shear plane is damaged causing a huge variability in fluid flow properties. Faults can be barriers to flow, conduits, or combinations of the two, and their hydraulic properties vary considerably over both space and time. It is critical for the prediction of both future and historical fluid (or gas) migration through fault zones to be able to assess their spatial and temporal hydraulic evolution. This is particularly relevant, due to the large timescales involved, when modelling historic migration in oil fields, or when simulating the transport of radionuclides following the deep burial of radioactive waste. Fluid flow and structural deformation are fully coupled processes within fault zones: Small scale discontinuities, such as fractures and deformation bands of reduced permeability, are formed in the damage zone surrounding faults and have a strong influence on flow properties. Fluid flow in the subsurface is traditionally modelled using Darcy's law, and structural deformation using Navier's law. The main aim of this research is to investigate and validate our understanding of these coupled processes in the damage zone surrounding faults. In the research presented here, fault zone evolution is modelled using a finite element approach. The coupled hydro-mechanical model has been developed and validated using standard benchmark data. The model has been used to simulate deformation and fluid flow in damage zone structures mapped at the Big Hole fault, Utah. Results demonstrate propagation of the existing slip surfaces leading to increased flow. The model is now being applied to explore temporal and spatial fault evolution in the Sierra Nevada based on data sets collected by B\"{u}rgmann and Pollard. Results will validate and enhance scientific understanding of the physical processes inherent in fault development. Ultimately, the model will be extended to include chemical processes such as mineralisation, and will provide an invaluable tool for predicting the heterogeneous hydrogeological properties of faults.
DE: 8010 Fractures and faults
DE: 5104 Fracture and flow
DE: 3200 MATHEMATICAL GEOPHYSICS (New field)
DE: 1744 Tectonophysics
DE: 1800 HYDROLOGY
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting