HR: 08:00h
AN: H51B-01    [PDF]
TI: Experimental Analysis of the Role of Fluid Transport Properties in Fluid-Induced Fracture Initiation and Propagation
AU: * Boutt, D
EM: dboutt@nmt.edu
AF: Geomechanics Department, Sandia National Laboratories, New Mexico, PO Box 5800, Albuquerque, NM 87123-0751 United States
AU: * Boutt, D
EM: dboutt@nmt.edu
AF: Department of Earth and Environmental Sciences, New Mexico Institute of Mining and Technology, 801 Leroy Place, Socorro, NM 87801 United States
AU: McPherson, B J
EM: brian@nmt.edu
AF: Department of Earth and Environmental Sciences, New Mexico Institute of Mining and Technology, 801 Leroy Place, Socorro, NM 87801 United States
AU: Cook, B K
EM: bkcook@sandia.gov
AF: Infrastructure and Information Systems Center, Sandia National Laboratories, New Mexico, PO Box 5800, Albuquerque, NM 87123-0576 United States
AU: Goodwin, L B
EM: lgoodwin@nmt.edu
AF: Department of Earth and Environmental Sciences, New Mexico Institute of Mining and Technology, 801 Leroy Place, Socorro, NM 87801 United States
AU: Williams, J R
EM: jrw@mit.edu
AF: Department of Civil and Environmental Engineering, MIT, 77 Massachusetts Avenue, Cambridge, MA 02139-4307 United States
AU: Lee, M Y
AF: Geomechanics Department, Sandia National Laboratories, New Mexico, PO Box 5800, Albuquerque, NM 87123-0751 United States
AU: Patteson, R
AF: Geomechanics Department, Sandia National Laboratories, New Mexico, PO Box 5800, Albuquerque, NM 87123-0751 United States
AB: It is well known that pore fluid pressure fundamentally influences a rock's mechanical response to stress. However, most measures of the mechanical behavior of rock (e.g. shear strength, Young's modulus) do not incorporate, either explicitly or implicitly, pore fluid pressure or transport properties of rock. Current empirical and theoretical criteria that define the amount of stress a given body of rock can support before fracturing also lack a direct connection between fluid transport and mechanical properties. Our research goal is to use laboratory experimental results to elucidate correlations between rock transport properties and fracture behavior under idealized loading conditions. In strongly coupled fluid-solid systems the evolution of the solid framework is influenced by the fluid and vice versa. These couplings often result in changes of the bulk material properties (i.e. permeability and failure strength) with respect to the fluid's ability to move through the solid and the solids ability to transmit momentum. Feedbacks between fluid and solid framework ultimately play key roles in understanding the spatial and temporal evolution of the coupled fluid-solid system. Discretely coupled models of fluid and solid mechanics were developed a priori to design an experimental approach for testing the role of fluid transport parameters in rock fracture. The experimental approach consists of first loading a fluid saturated cylindrical rock specimen under hydrostatic conditions and then applying a differential stress such that the maximum stress is perpendicular to the cylinder long axis. At the beginning of the test the minimum stress and the fluid pressure are dropped at the same time such that the resulting difference in the initial fluid pressure and the final fluid pressure is greater than the final minimum stress. These loading conditions should produce a fluid driven tensile fracture that is perpendicular to the cylinder long axis. Initial analyses using numerical simulations with similar boundary conditions suggest that resulting fracture propagation rates and fracture spacing are controlled by the rocks hydraulic diffusivity. Modeled rocks with higher permeability had fractures with larger apertures, more localized deformation, and greater fracture spacing. Intuitively, these results are consistent with permeability controlling the time required for pressure to come to equilibrium with the new boundary conditions. Finally, more general goals of this research include using these core-scale experimental data and discrete simulation results to calibrate larger-scale, more traditional continuum models of geologic deformation.
UR: http://www.nmt.edu/~dboutt/AGUFALL03/
DE: 5104 Fracture and flow
DE: 5114 Permeability and porosity
DE: 8010 Fractures and faults
DE: 8045 Role of fluids
SC: Hydrology [H]
MN: 2003 Fall Meeting