Successful Electrofrac Testing Prompting ExxonMobil to Seek Oil Shale R&D Lease from Interior Department in Planned Second Round
GJ Sentinel. Recent successful field tests at its Colony Mine with the Electrofrac process for converting the kerogen in oil shale to producible oil and gas is prompting ExxonMobil to try again for a research and development lease from the Interior Department for a larger trial. ExxonMobil sought, but was denied, one in the first round in 2005.
|ExxonMobil’ Electrofrac Process creates electrically conductive fractures (vertical or horizontal). The planar heat source is more effective than radial conduction from wellbores for the conversion of kerogen. Click to enlarge.|
The Electrofrac process is designed to heat oil shale in situ by first building a hydraulic fracture (a conventional oil field technology) in the oil shale. The fracture is filled with an electrically conductive material—lab experiments have shown that calcined petroleum coke is a suitable Electrofrac conductant.
Electricity is conducted from one end of the fracture to the other, making it a resistive heating element. Heat flows from the fracture into the oil shale formation, gradually converting the oil shale’s solid organic matter (kerogen) into oil and gas. Multiple layers of heating wells may be stacked for increased heating efficiency. The resulting oil and gas hydrocarbons are produced by conventional methods.
Because Electrofrac relies on heat conduction from a large planar heat source, it has the potential to provide cost-effective recovery in deep, thick oil shale with less surface disturbance than other proposed methods, according to ExxonMobil researchers.
Assuming that the process works on a large scale, ExxonMobil sees tantalizing prospects for shale: up to 162,000 barrels of oil per surface acre at a 50 percent recovery rate. The results suggest a 3-to-1 ratio of energy recovered over energy expended to obtain it, McGinn said...It appears ExxonMobil can make its process work using about 1.5 barrels of water for each barrel of oil produced, he said.
Even under the most optimistic of scenarios, ExxonMobil sees no production coming from oil shale for 10 to 24 years, McGinn said. That leaves plenty of time for the company to plan what would be a extensive network needed to generate the electricity necessary to heat the shale, collect the kerogen and begin moving it to refineries and then to markets.
William A. Symington et al. (2008) ExxonMobil’s Electrofrac Process for In Situ Oil Shale Conversion (AAPG Annual Convention & Exhibition)
William A. Symington, James S. Burns, Wadood El-Rabaa, Glenn A. Otten, Norman Pokutylowicz, P. Matthew Spiecker, Richard W. Williamson, Jesse D. Yeakel (2009) Field testing of Electrofrac process elements at ExxonMobil’s Colony Mine