Potter Drilling, LLC (Potter) is a Redwood City, California-based company that develops drilling technology for various applications, including geothermal energy production.

Potter specializes in novel drilling systems that don’t require contact between the drill assembly and the rock in order to make holes in the geological formation.  Specifically, the company’s key innovations involve a process called spallation, which uses high intensity fluid streams to fracture rock surfaces. 

A common problem that arises during deep drilling is that non-uniform stresses are created around the borehole, which cause the rock around the hole to break out; this can make a circular hole become non-circular.  Pieces of rock can fall into the hole, causing the drill or casing to get stuck.  This phenomenon is aptly named “breakout.”

Potter’s drilling processes take a proactive approach to this problem by intentionally creating non-circular boreholes to avoid inadvertent and uncontrolled breakout.

In addition, Potter developed a technology to produce non-circular boreholes for ground source heat pump (GSHP) applications where it is desirable to separate the tube carrying water down the hole from the tube carrying water back up in order to reduce heat exchange between the different temperature streams. 

Potter owns U.S. Patent Application Pub. No. 2008/0093125 (‘125 application), entitled “Method and system for forming a non-circular borehole”, which describes some of the company’s drilling technologies for creating shaped boreholes.  

One of those is particle drilling for GSHP applications, which uses particles in an air stream to cut the rock.  This technology is being developed by a spinoff company called Ground Source Geothermal.

I talked to Dr. Tom Wideman, Potter’s CTO, who told me (no pun intended I think) that the company’s “most groundbreaking” technology is hydrothermal spallation.

Hydrothermal spallation uses hot water to cut through rock.  According to the company’s web site, hydrothermal spallation was invented and patented by Potter’s co-founder Robert Potter and Jefferson Tester of MIT. 

Potter is the exclusive licensee of U.S. Patent No. 5,771,984 (‘984 patent), which is owned by MIT and directed to apparatus and methods of excavation by hydrothermal drilling. 

The ‘984 patent covers a jet housing (602) rotatably mounted to a flow pipe assembly support (604).  The jet housing (602) contains two or more combustion chambers (610).  

Jet housing (602) contains passageways (614) for cooling water, passageways (616) for the fuel and passageways (618) for the combustion air.  It also has a central conduit (620) for the escaping combustion gases and returning flakes of rock. 

The hot fluid products of thermal combustion are jetted downward onto the rock though nozzles (612) located near the outer circumference of the bottom of the drilling apparatus.

This Clean Technica piece calls Potter’s hydrothermal spallation drill the “Holy Grail” of geothermal because of the promise that it can drill faster, deeper and cheaper than prior drilling systems. 

Potter is continuing its spallation innovation and patenting.  Wideman described Potter as an “IP-rich company” and told me the company has multiple recently-filed patent applications in the pipeline.

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