Results from the EGS Collab project will support the DOE Geothermal Technology Office FORGE and other EGS development efforts. Results of this testing suggest that the fracture flow pathways can be altered as a result of the pressure perturbations in the injection well on the integrity of adjacent monitoring wells. These changes are believed to be in response to a number of higher-pressure short-term injections at the injection well in early November (2nd to the 6th). A comparison of the tracer breakthrough curves at the production well showed a marked decrease in the initial and peak concentration over time, whereas the OB well exhibited an increase in the initial and peak concentration arrival during this fracture characterization testing period. Analysis of a series of tracers more » during this two-week period suggest a large change in the flow fracture field occurred during this testing period. The injected tracers were detected in three of the five water production locations where the total water recovery ranged from approximately 50 to 80% of the injected water depending on the day the test was being conducted.
From the end of October to the middle of November of 2018, a series of fracture characterization tests were conducted using a series of 10 tracer tests (7 which used C-dot and chloride as conservative solute tracers) to assess the flow pathway in the stimulated fracture. Injected water was recovered from five locations in 4 nearby wells. A flow system was established in one set of fractures by injection water at approximately 400 ml/min between a set of packers 164 feet from the drift wall in the injection well through a hydraulically stimulated fracture. Hydraulic fractures were created at an injection well drilled sub-horizontal from the drift. The first multi-well experimental site was established at the 4850 level of the Stanford Underground Research Facility (SURF) in the Homestake Mine located in South Dakota. The EGS Collab project constructed an approximately ten-meter scale field site where fracture stimulation and flow/transport models can be validated against controlled, in-situ experiments.
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