A Rathole is a temporary storage space that is 30 to 35 feet deep, lined with casing that projects above the floor, and used to store the kelly and swivel. This is either done by the portable rig that drills the conductor hole or can be done by the primary rig after rigging-up.
[pdf] A complete range of accessories for large diameter drill rigs, including kelly bars, CFA augers, drilling equipment and tools, designed to support the full spectrum of large diameter drilling methodologies in all types of soil.
[pdf] This Handbook is a description of the complex process that comprises drilling a geothermal well. The focus of the detailed Chapters covering various aspects of the process (casing design, cementing, logging and instrumentation, etc) is on techniques and. .
The audience for this Handbook is assumed to be familiar with the general nature of drilling, so there is no attempt to give procedures and guidance for every step needed to drill a. .
This Handbook was funded by the US Department of Energy’s Geothermal Technologies Program and has been made possible with support and guidance from Jay Nathwani.. .
The word "geothermal" comes from the combination of the Greek words gê, meaning Earth, and thérm, meaning heat. Quite literally.
[pdf] 
