| Enhanced Geothermal Systems (EGS) have substantial potential as a domestic energy source and is well suited as an alternative to diversify the national energy portfolio due to its high levels of heat and recoverable energy. Hydraulic fracture stimulation of low permeability EGS reservoir rock is widely employed to develop this resource and is generally required to make unconventional resources an economically viable resource. Significant challenges for EGS technology include poor connectivity between injection and production wells during stimulation and difficulty predicting fracture growth (Tester, et al. 2006). This, coupled with notable advances in oil and gas recovery, has made hydraulic fracture mechanics the subject of considerable study.;Acoustic emissions, or microseisms, contribute greatly to these studies and have been employed on a wide range of topics in rock mechanic studies. At Colorado School of Mines, acoustic emission technology has been employed to monitor stimulation of cubic granite samples under heated and true triaxial stress environments to simulate deep reservoir conditions. Recorded AE activity was used to determine proper location of production well placement while additional analysis on the fracture process using characteristics such as wave amplitude and hit rates were used to identify stages of activity during fracture propagation. Study of the spatial and time dependence of the initiation and growth of rock fractures is critical to understanding the processes that govern fracture behavior and require details that are not accessible to alternative methods of analysis. Acoustic emissions can provide crucial information and represent an important part of rock mechanics studies. |
