Preliminary Collab Fracture Characterization Results from Flow and Tracer Testing Efforts

Abstract

The EGS Collab project is developing ~10-20 m-scale field sites where fracture stimulation and flow models can be validated against controlled, small-scale, in-situ experiments. The first multi-well experimental site was established at the 4850 level in the Homestake Mine, where hydraulic fractures were created at an injection well drilled sub-horizontal from the drift. To date, establishing a steady state flow field between the injection and production well has been problematic. This paper will discuss some of these stimulation issues along with results from the flow and tracer testing to characterize the system. Results from early testing have been re-analyzed as to the; amount and location of injected water recovery, changes in the flow system as a function of time, and temperature breakthrough at monitoring wells. Currently, characterization efforts are focusing on injecting distilled water as a chemical solute tracer. Attempts will be made to collect water samples at production zones and construct electrical conductivity breakthrough curves. These results will be compared to electrical resistivity tomography (ERT) time-lapse images in an attempt to correlate the breakthrough information with spatial flow in the system derived from the ERT effort. Finally, DNA is also being investigated as a tracer and is planned to be injected at several locations as an effort to distinguish flow pathways from the injection well to the production well.