2019 Physics/Theoretical Colloquium
 
Thursday, October 17th , 2019
3:45 – 4:45 p.m.
Rosen Auditorium (TA-53, Bldg. 001)
 
 
Refreshments at 3:15pm
 
Speaker:   Prof. William Roggenthen
South Dakota School of Mines
 
 
“Rock Properties and Fracturing Studies at the Sanford Underground Research Facility (SURF)”
 
Abstract: 
 
SURF is an underground particle physics facility located in a former gold mine, but it also provides opportunities for geomechanical studies. The main science level is located 1.5 km below the surface, and a series of geothermal experiments have been conducted including kISMET (permeability [k] and Induced Seismicity Management for Energy Technologies) and the EGS Collab project which is currently underway.  These projects have drilled a total of ten bore holes ranging from 50 to 100 m in length over lateral distances of tens of meters. Taking advantage of the stresses at this depth, fracturing was initiated that successfully determined the direction and magnitude of the minimum horizontal stress.  The EGS Collab test bed includes a 60 meter-long injection borehole and a parallel production hole separated by ~10m.  The injection hole was drilled parallel to the minimum compressive stress and was hydraulically fractured. Given this geometry, induced fractures should be perpendicular to these boreholes, and the subsequent water flow used to evaluate heat extraction from the rock should progress from the injector to the production borehole. Two monitoring bore holes fitted with geophysical instrumentation are parallel to the injection and production boreholes and four are perpendicular to the injection/production holes. The fracturing and water movement is being monitored using continuous active source seismic, electrical resistivity tomography, distributed temperature sensing systems, microearthquake sensing systems, tracers introduced into the flow water, and downhole video cameras.  The flow paths are complicated by the interaction between the induced fracture system and the naturally occurring fractures. A primary objective of the program is the validation of coupled process models using a large-scale test site that extends for tens of meters laterally.  The 4850 Level of SURF is the site for the far detector of the DUNE project, and these rock mechanics experiments provide an extensive rock property database and have advanced the understanding of the geomechanical properties of the same rock type that will host the neutrino project.