题目：Characterization of rock fracturing for enhanced geothermal systems
报告人：Dr. Roman Makhnenko, University of Illinois at Urbana-Champaign
Production of renewable and green energy is becoming extremely important because of the projected depletion of fossil fuels and climate change. Enhanced geothermal systems offer new perspective where man-made fractures are created by stimulation methods (primarily hydraulic fracturing) to enhance the permeability of hot rock formations at the depth of at least three kilometers. Proper rock characterization is required, as well as the upscaling that would involve laboratory experiments on size-effect on rock fracturing and numerical modeling of rock mass response. Rock mechanics group at the University of Illinois at Urbana-Champaign performs hydraulic fracturing and three-point bending experiments to study size effect on fracture toughness and process zone. Ultrasonic waves and acoustic emission are used to track propagating fractures and the zone of microcracking in front of them. Based on the test data, we demonstrate the suitability of a theoretical relationship between the size of the process zone and specimen size. The model allows estimation of the limiting specimen size, beyond which no further noticeable increase in the fracture toughness and process zone size is observed, and prediction of in-situ crystalline rock behavior to fluid injection.
Roman Makhnenko is an assistant professor in the Department of Civil and Environmental Engineering at the University of Illinois at Urbana-Champaign. Roman received his PhD (2013) degrees in geological and civil engineering from the University of Minnesota - Twin Cities. Currently, Roman is developing the rock mechanics program at Illinois that involves modern high-pressure high-temperature rock testing facilities and new graduate courses on the topic. His ongoing projects include laboratory investigation of geomaterials and processes associated with CO2 storage and experimental and numerical characterization of enhanced geothermal systems.