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Initial testing consisted of running the heater for <br />several hours at constant rate and analyzing the <br />temperature decline in the heater hole in the same <br />manner one would analyze a pressure build-up test <br />in a well. This allowed interpretation of an <br />average thermal conductivity for this part of the <br />mine. <br />In a second phase of the test the central heater was <br />operated for several weeks under thermostatic <br />control to avoid generating oil and gas. The <br />thermostatic control prevented the heater from <br />exceeding a temperature of 140°F. This phase of <br />the test evaluated the anisotropy of heat <br />conduction in the mine by monitoring temperature <br />in the adjacent holes. <br />7. ELECTROFRAC FRACTURE PUMPING <br />With the benefit of these pretests, two Electrofrac <br />hydraulic fracture treatments were designed and <br />pumped at Colony in mid-2008 in holes EF 1 and <br />EF3. The positions of the two holes along with <br />the resulting fractures are displayed in Figure 7. <br />EF 1 penetrates the south mine pillar from the <br />north drift. EF3 penetrates the north mine pillar <br />from the crosscut. A third hole, EF2, was drilled <br />but not selected for fracturing. <br />EF 1 and EF3 were cased and cemented, except for <br />a short open section at the end of each hole. Both <br />fracturing jobs placed a slurry of calcined coke, <br />Portland cement, and water in the hydraulic <br />fracture. The job at EF3 was larger than the one at <br />EF 1 and was pumped at a higher rate, but they <br />were otherwise quite similar. During the EF3 <br />fracture job, coke-cement slurry was observed to <br />flow from the mine rib in the crosscut. <br />After pumping the two Electrofracs, a program of <br />cored observation holes was completed to map the <br />fractures and investigate their electrical properties. <br />Coring allowed recovery and examination of <br />calcined coke from the fracture. Ultimately, 28 <br />observation holes were used to map the two <br />fractures. The 3D model in Figure 7 shows the <br />interpreted fracture shapes and the observation <br />holes used to map them. The small disks posted <br />along the observation holes indicate the <br />occurrence and orientation of calcined coke <br />encountered in the core. The two larger, outlined <br />disks on each fracture identify observation holes <br />that were later converted to power connections, <br />completing the Electrofrac circuit. The electrode- <br />to-electrode distances at the two fractures, EF 1 <br />and EF3, are 99 and 132 feet respectively. <br />Built and verified <br />two Electrofracs: eC?j <br />EF7 -140 ft @ <br />EF3 -200 ft <br />G??ygGJ` EF3 <br />I entation <br />s on EF7 <br /> <br /> <br /> <br />? <br />GfhO ; Cored 28 observation <br /> <br />n holes: All intersections <br />? ?;_" EF1 probed are electrically <br /> connected <br />Figure 7. Electrofracs EF1 and EF3 along with the <br />observation holes used to map them. <br />Figure 8 shows photographs of the fracture job at <br />EF1. The job was pumped with a Halliburton <br />HT400 pump truck, supplied with coke-cement <br />slurry from a BMR 100-barrel batch mixer. The <br />slurry was mixed on site as shown in the lower <br />right. Thirty-three barrels of slurry were preceded <br />by 77 barrels of green-dyed gelled water. The job <br />29th Oil Shale Symposium Page 5 of 13 October 19-23, 2009 <br />Figure 6. In situ thermal conductivity test physical setup <br />and equipment.