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8. ELECTROFRAC POWER CONNECTIONS <br />Having two electrically continuous fractures, the <br />next phase of field work focused on building <br />power connections to the Electrofracs. To avoid <br />generating most of the heat at the connections, an <br />even more electrically conductive material is <br />needed in this area. This material has been <br />nicknamed "good juice." In our current work it is <br />a graphite-cement slurry, although other <br />electrically conductive materials may be suitable. <br />Good juice is injected directly into the pre-existing <br />coke-filled fracture. Cement is added to the <br />slurries to ensure the conductive material in not <br />displaced away from the connection during <br />repeated injections. Figure 11 describes the <br />function of "good juice" and shows photos of its <br />injection. The modeled fracture temperatures in <br />Figure 11 show that good juice should nearly <br />eliminate heat generation at the connections. In <br />the example, the maximum connection <br />temperature is reduced from 1678 °F to 134 °F. <br />The photos show "good juice" (dyed with a red <br />pigment) being injected with a ChemGrout CG508 <br />grout plant, capable of delivering up to 14 gallons <br />per minute at 2000 psi. The good juice flowing <br />from the mine rib in a pretest (lower right photo) <br />verified that good juice can be injected into a pre- <br />existing coke-filled fracture. This is obviously <br />critical to the approach. <br />Function of Graphite "Good Juice" <br />• Provide higher conductivity at power connections. <br />• Provide an electrical connection between steel casing <br />in the hole and the body of the Electrofrac fracture. <br />4 <br />Figure 11. Graphite "Good Juice" injection prevents hot spots at Electrofrac power connections. <br />The fracture places stress on the injected good <br />juice to make it conductive, but the portion <br />remaining in the hole must be squeezed and <br />dewatered to become conductive, and effectively <br />connect the steel casing to the coke in the fracture. <br />This was accomplished with a large screw drive <br />that forces a flexible porous piston down the pipe <br />to dewater the graphite. This process is illustrated <br />in Figure 12. The flexible porous piston is a <br />balled-up pair of panty hose driven by a metal <br />piston with drainage holes. The figure shows one <br />of these pistons after a laboratory squeezing job. <br />The laboratory-squeezed good juice is shown just <br />below it. It's similar to a thick graphite pencil. <br />With good juice in the hole squeezed into a pencil <br />like this, the result is the Electrofrac heating <br />29th oil Shale Symposium Page 8 of 13 October 19-23, 2009 <br />Modeled Fracture Plane Temperatures (90 days)