HR: 13:55h
AN: H13J-02 INVITED    [Abstracts]
TI: What Have We Learned About Fluid-Fracture Interaction in the Analog Aquifer/Reservoir at the Valley of Fire, Nevada?
AU: * Aydin, A
EM: aydin@stanford.edu
AF: Department od Geological and Environmental Sciences, Stanford University, Stanford, CA 94305, United States
AU: Pollard, D D
EM: dpollard@pangea.stanford.edu
AF: Department od Geological and Environmental Sciences, Stanford University, Stanford, CA 94305, United States
AU: Durlofsky, L
EM: lou@pangea.stanford.edu
AF: Department of Energy Resources Engineering, Stanford University, Stanford, CA 94305, United States
AB: The Jurassic aeolian Aztec Sandstone in the Valley of Fire State Park, Nevada, provides an exceptional natural laboratory to observe fluid-fracture interaction. This presentation is a summary of our investigations over the past decade and addresses: 1) how various fundamental types of fractures interacted with paleo-fluids; and 2) what we have learned about the hydrologic bases for these interactions. The oldest failure structures in the sandstone are a result of deformation localization of both shear band and compaction band types. These structures represent significant porosity and permeability reduction with respect to the undeformed rock as determined from image analyses and lattice-Boltzmann flow simulations, as well as from modeling the paleo-fluid fronts. The simplest failure structures are opening mode fractures or joints which conducted fluids in a fashion close to the idealized parallel plate model with well organized roughness. Sheared-joints which form by slip along pre- existing joints are the simplest shear fracture with slip on the order of millimeters to centimeters. There is abundant evidence that shearing enhanced the conductivity of these fractures. The physical bases of this phenomenon are thought to be dilation associated with slip across rough surfaces and increasing connectivity by linkage through splay fractures. Large-scale shear fractures or faults are always multi-component structures including slip surfaces, fault rocks, and damage zones which are composed of the simpler failure structures referred to above. Due to this complexity, the interaction between fluids and faults shows a wide range of variation. These effects are demonstrated using observation, laboratory measurements as well as upscaled permeability models. We conclude that the Valley of Fire analog aquifer/reservoir displays excellent examples of fluid-fracture interactions with a wide range of diversity, controlled primarily by the failure modes, and that flow modeling at various scales reveal the fundamental physical processes responsible for the nature of the observed interactions.
DE: 1822 Geomechanics
SC: Hydrology [H]
MN: 2007 Fall Meeting