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temperature profiles through the fracture. Another <br />16 holes roughly parallel to the fracture contain <br />over a mile of fiber optic cable used in a <br />distributed temperature sensing system. The <br />system provides a temperature measurement every <br />meter along the fiber length. <br />oles N <br />e?t`O6 across and adjacent to fracture <br />ID <br />Roughly parallel holes for <br />Fiber Optic Temperature { <br />Measurement <br />OB9 <br />OB4 <br />ao \\ ." oftt% flit <br />t4 <br />Roughly perpendicular Eight open holes (not shown) <br />admit probes for voltage and <br />holes for thermocouples current measurement. <br />Figure 14. Instrumentation holes for the EF3 low- <br />temperature heating experiment. <br />In addition, eight observation holes at EF3 are <br />used for electrical measurements. These include <br />voltages measured with boiler brush probes and <br />electric current densities measured with a <br />magnetic sensor. These measurements are made <br />periodically by running the probes into the holes. <br />Finally, multi-point extensometers are installed in <br />two observation holes, one running across the <br />fracture, and one running east of the fracture. <br />These measure rock movement caused by <br />Electrofrac heating. <br />The photographs in Figure 15 show the <br />installation of instruments in the mine. <br />Thermocouple bundles 150 feet long were <br />assembled in Houston and shipped to the mine on <br />the large reels shown in the upper right photo. <br />They were run into holes attached to PVC pipes <br />used to cement them in place. The fiber optic <br />cable for temperature measurement was run in and <br />out of each hole in sequence. The fiber was <br />threaded over torpedo-like probes (center photo) <br />which prevented it from turning too tight a radius <br />which would attenuate the signal. These probes <br />were also conveyed into holes on PVC pipes. <br />Finally, the lower right photo shows assembly of <br />an extensometer, which measures rock motion <br />transmitted by graphite rods anchored at several <br />locations along the hole. <br />owl) <br />?Figure 15. Installation of instrumentation for the EF3 Electrofrac low-temperature heating experiment. <br />29th Oil Shale Symposium Page 10 of 13 October 19-23, 2009