I suspect the RF energy is used to achieve in-situ hydrocracking of the heavy oil and tar into middle and light distillates which can then be transported to the surface by the supercritical fluid (presumably, mostly water). This will work only if the reservoir is sufficiently well sealed yet shallow enough for the RF radiation to penetrate the rock formation.

Power consumption and water recycling will be key challenges. In Western Colorado, where the US Navy owns huge shale oil deposits, water is scarce (much of it is reserved for Los Angeles by way of the Colorado river).

Mark -

thx for the correction. By using CO2, they would avoid consuming water in a region that has too little and, the associated ground water pollution.

I would expect that the CO2 would be recirculated as much as possible, mostly because producing it requires burning fossil fuel. Failing that, perhaps they intend to build a power station in the vicinity to provide a CO2 source. GHG issues are probably not the #1 priority of the folks that are advocating this, for them it's all about reducing the dependence on oil imports from hostile and/or unstable countries.

Actually you are incorrect in that CO2 could not be used at the shale formations depth. The critical point for CO2 is 31’c and 7.38 mpa or 1070 psi. CO2 was chosen because its critical point is so much less than water’s at 374 ‘C and 22 Mpa (3200 PSI ). That being said the average unconfined compression strength of limestone is between 43.6 MPa (6336 psi), and 73.8 MPa (10718 psi) Unconfined means without overbearing rock strata.
To put this in perspective concrete is usually rated from 4000-10000 psi. Limestone is so strong in compression it’s used, as a structural material for multistory building in Texas the tallest in Austin is 5 stories of unsupported native Texas limestone. O I guess I should clarify I am a Geologist, and currently a grad student at the University of Texas at Austin. I mention limestone, as it is typically the cap rock on the kerogen bearing strata to be targeted with supercritical solvent extraction.
As for the RF having to penetrate the rock strata if you look at the background research in this method the RF energy is conveyed down shaft via wave-guides where it heats the source rocks laterally away from the boreholes. They’re not setting up microwaves on the surface, and beaming it into the ground as was alluded too farther up. Once the strata have been heated the supercritical fluid is used to extract the resulting distillates from downward injection wells to upward producing wells following induced fractures in the formation. Since shale is neither permeable nor porous the fracture system is induced via high pressure hydraulic methods. The CO2 is recycled again, and again in a closed loop system.
Shell is using electric heaters instead of RF to heat the strata to the necessary temperatures, and their energy input/output ratio was 1 to 8 last I checked putting it on par with pumped deepwater oil ,and enhanced oil recovery methods in existing fields. Since sedimentary rocks do not have high specific heat capacities it does not take a lot of energy to heat rock that is already around 50’C to the 250’C necessary to crack kerogen insitu. The historic inability to extract shale oil insitu was the choice to use water as the solvent or to use partial combustion down-bore as the energy source both are very inefficient. Plus there was insufficient political will or funding for the extraction of the resource when oil at the time was 5-10 bucks a barrel. Shells electric heater test plot is yielding light sweet distillates without the use of water as a co solvent or any additional hydrogen source. The Shell method is a reduction coking reaction that leaves the excess carbon from the reaction down bore as coke deposits. Which in the future could be extracted using a endothermic high temperature steam reformation method C+H2O --> 2CO+H this resulting syngas can be liquefied on site via Fischer Tropsch synthesis or methanated via the Sabatier reaction for subsequent pipeline or LNG use.