|Radio Frequency / Critical Fluid Oil Extraction Technology. Click to enlarge.|
Schlumberger, a leading oilfield services company, has acquired Raytheon’s technology for the extraction of oil from oil shale and oil sands. Financial details of the transaction were not disclosed.
The technology, developed by Raytheon and partner CF Technologies for oil shale processing, combines radio frequency (RF) technology from Raytheon with critical fluid (CF) technology from CF Technologies. (Earlier post.) Raytheon has projected that the same process could also be used to retrieve oil from Canadian oil sands and to reprocess spent wells.
Field experience indicates that the Raytheon RF heating technique obtains recovery rates of 75% of the oil shale’s Fisher Assay value. (A method used to approximate the energy potential of an oil-shale deposit.) Coupling RF heating with the CF technology has resulted in recovery rates as high as 90 to 95%.
Critical fluids, or supercritical fluids (SCF), are liquids or gases used in a state above their critical temperature and pressure (critical point). In this state, the SCF has unique properties different from those of either gases or liquids, offering a combination of liquid-like density and solvency, with gas-like viscosity, diffusivity, compressibility and lack of surface tension.
As a result, supercritical fluids can rapidly penetrate porous and fibrous solids, offer good catalytic activity and can dissolve and extract a wide range of chemicals. Carbon dioxide is commonly used as a supercritical fluid.
Under the oil shale extraction scenario, oil well holes are drilled into the shale strata using standard oil-industry equipment. RF antennae, or transmitters, are lowered into the shale. The antennae then transmit RF energy to heat uniformly the buried shale rock. This results in the volatilization of water, which, in turn, results in the microfracturing of the formation, enhancing product recovery.
|Samples of kerogen extracted from oil shale with the RF/CF process. Click to enlarge. Credit: Raytheon|
Supercritical carbon-dioxide fluid is then pumped into the shale formations to separate the petroleum from the rock and direct the freed fuel to another well, where it is extracted. Next, the carbon-dioxide fluid is separated from the oil and gas, which is sent to a refinery and further processed into gasoline, heating oil and other products. Ultimately, a self-sequestration approach is expected to yield a neutral carbon foot print for process operations.
The RF/CF combination is more economical and environmentally responsible than older oil shale extraction techniques as it uses less power, does not severely disrupt the landscape or leave behind residue that can enter groundwater supplies.
Raytheon earlier estimated that the technology would retrieve four to five barrels of oil for every one barrel invested. Other in-situ processes retrieve one and a half to three barrels of oil for every barrel consumed estimated.
For tar sands and heavy oil, the Raytheon process could yield 10 to 15 barrels of oil equivalent per barrel consumed, due to the lower heating temperatures required. When applied in tar sands, the combined RF/CF technology performs a mild upgrading in-situ, yielding an attractive light sweet crude oil. The process is “tunable”, facilitating production of various product slates.
The use of RF technology in shale processing would enable the fuel to be extracted from the earth in only one to two months. In-ground heating methods that do not employ radio waves, by contrast, require three to four years to replicate the natural conversion process.
Raytheon’s RF technology was commercially proven for oil shale applications in the 1970s. Since then, the company has continued to perfect the technology, focusing on antenna design and system integration.
Draft OSTS PEIS, Appendix A: Oil Shale Development Background and Technology Overview (December 2007)
Geology and Resources of Some World Oil-Shale Deposits (USGS Scientific Investigations Report 2005–5294)