The concern is that the water, which is pumped out after the process, may either leak these substances plus radioactive radon from the well directly into aquifer layers, or contaminate water supplies after pumping out.
For this reason, some fracking engineers prefer non-hydraulic methods. One of these, used recently in New York State, swaps the water for gelled propane. The idea being that the propane reverts to a gas at the end of the process and can be pumped out, leaving any additives behind in the well, much like boiling seawater and leaving behind the salt.
The Chimera process takes this a step further by eliminating any working liquid. Details of the process have not been made public yet due to patent concerns, but Chimera Energy uses what is called “dry fracturing” or “exothermic extraction.” First developed in China, this involves using hot gases rather than liquid to fracture the shale. This was originally intended for wells in arctic regions where water used in fracking freezes, but Chimera Energy has developed it for general use.
In dry fracturing, metal oxides, ultra-expansive evaporants and pumice are pumped into the well. The metal oxides react with one another to form an exothermic reaction. Extremely hot gases are generated that expand and crack the shale. Meanwhile, the pumice shoots in and reinforces the fractures, keeping them from closing and allowing the gas or oil to flow.
Chimera Energy claims that not only is the technique environmentally safe, but that it is compatible with any existing well in the world.