Laserfiche WebLink
Figure 3. Colony Mine physical layout. <br />The mine tunnels are 22 ft wide and 12 to 14 ft <br />high. They provide a generous work area allowing <br />roughly horizontal drilling into the Mahogany <br />zone. To facilitate work in the mine, ExxonMobil <br />has installed overhead lighting, ventilation, and <br />permanent compressed-air and water piping in the <br />mine. Field offices and storage buildings have <br />been set up outside the mine. <br />The mine tunnels at Colony provide ready access <br />to a large volume of oil shale under in situ stress <br />created by several hundred feet of overburden. As <br />a result, they provide an ideal laboratory for <br />ExxonMobil's initial Electrofrac field research. <br />3. FIELD RESEARCH PROGRAM <br />ExxonMobil's Electrofrac field research program <br />at Colony has progressed through several phases, <br />including the following: <br />• Geologic mapping of natural fractures. In <br />mid-2007, fractures observed on the mine <br />roof and ribs (walls) and the outside cliff <br />face were mapped and modeled in three <br />dimensions. <br />• In late-2007, hydraulic fracture pretests were <br />conducted to understand hydraulic fracturing <br />in the mine. These pretests included <br />pumping three small fracture jobs with <br />colored grout that could later be found by <br />coring. <br />• In early-2008, a thermal conductivity pretest <br />was conducted to understand the thermal <br />properties of oil shale in the mine. <br />• In mid-2008, two Electrofracs, EF 1 and <br />EF3, were pumped with a calcined coke and <br />cement slurry. <br />• Early in 2009, after several laboratory and <br />field pretests, Electrofrac power connections <br />were pumped and squeezed at EF 1 and EF3. <br />• Most recently, Electrofrac EF3 was <br />instrumented and operated in a low- <br />temperature heating experiment. This low- <br />temperature test was not intended to <br />generate any oil or gas. As a result, the test <br />permitted verification of Electrofrac <br />function, without the need to collect any <br />generated fluids. <br />In the remainder of this paper, highlights from <br />each phase of the field research program will be <br />described in more detail. <br />29th Oil Shale Symposium Page 3 of 13 October 19-23, 2009