A model study of fracture generation in layered brittle rocks with applications to predicting subsurface fracture networks

Single and multiple sets of mode I (opening mode) fractures are simulated using a layered model material, brittle coating, on a PMMA (polymethyl methacrylate) substrate. In most laboratory fracture experiments on small rock specimens the grain-scale heterogeneity can control the fracture process and gross failure of the sample is the normal outcome. This is not a good analogue for fracture in the earth where a stable process is the rule rather than the exception. For the model experiments introduced in this dissertation the specimens do not fail and fracture propagation is stable. Several new fracture experimental techniques are introduced to improve the analogy to fractures in the earth.;The geometry, pattern, and propagation velocity of a fracture set, and the effect of fracture origin, time, material thickness, concretions, and different loading histories on the fracture set are investigated to achieve a better understanding of the behavior of fractures during initiation and propagation.;Potential applications of this research to petroleum geology and reservoir engineering, structural geology, and hydrology are discussed. Attention is paid to the techniques of predicting subsurface fracture networks for the analysis of reservoir characteristics. For example, two methods are introduced: (1) rebuilding subsurface fracture networks, and (2) predicting fracture drainage area in rocks surrounding a borehole.