HR: 09:15h
AN: T41G-06 INVITED     [Abstracts]
TI: Predicting Aperture and Length Population Statistics Using a Fracture Mechanics Model
AU: * Olson, J E
EM: jolson@mail.utexas.edu
AF: University of Texas at Austin, Petroleum and Geosystems Eng., 1 University Station C0300, Austin, TX 78712 United States
AB: Diagenesis and fracturing are often linked processes in deformed rock, particularly with regard to veins. The nature of preserved aperture distributions in veins, crack-seal textures, cement bridges across fractures, and fracture porosity preservation under effective compressive stress suggest that mineral precipitation and fracture growth often occur simultaneously. A fracture mechanics model is used to examine the systematics of aperture and length distributions generated by subcritical crack growth under uniform-rate, extensional-strain boundary conditions for stratabound fractures, with and without simulated diagenesis. Numerical results show considerable variability in fracture aperture distributions, but in many cases, aperture populations follow negative exponential curve shapes, consistent with published field observations for stratabound fractures in sedimentary rock. Fracture aperture closure under effective compressive stress is examined with respect to diagenetic stiffening of the rock matrix during the fracturing event. The numerical model also predicts episodic crack propagation that could be analogous to crack-seal vein growth. Crack growth reconstructions through time of numerically-generated orthogonal patterns show that the longest fractures are those that grow first, and these early fractures reach their fullest extent before shorter fractures begin growing. The generated length distributions are predominantly power-law in shape, with the slope established early in the fracture growth history by the longer fractures. Shorter fractures grow to the extent required to extend the power-law shape to smaller sizes. Uniform orientation (single set) patterns of straight fractures show negative exponential to power-law length distributions with different growth histories.
DE: 5104 Fracture and flow
DE: 8010 Fractures and faults
DE: 8020 Mechanics, theory, and modeling
DE: 8199 General or miscellaneous
SC: Tectonophysics [T]
MN: Fall Meeting 2005