My first job out of college was as a drilling engineer with Exxon, working on inland and barge rigs in south Louisiana. Our office was in New Orleans. Great job! One of the rigs I worked on was on a three-mile deep well near Jackson, Mississippi called the Mongurere Wildcat. It was so hot at the bottom that we had to drill with oil instead of water as the drilling fluid. Very high tech for that time, in the late ’70s. (I was a member of the “Three Mile Club.”)
I explain all about Ground Source Heat Pumps (GSHP) in 1001 Energy Tips. GSHPs are a well-established technology for heating and cooling a house. The ground is always cooler than the outside air in the summer and warmer in the winter, so GSHPs are always more efficient than the usual air-source heat pumps. Typically, you drill one 100-150 foot well per ton of cooling, connect the wells into a piping loop, and circulate water through the loop going to the air handler.
In other words, the technology exists and is well-established to extract heat from the ground, even if there’s just a small temperature difference. The ground temperature increases roughly 25 C for each kilometer of depth.
A few years ago, when I was living in Vicksburg MS, I scouted some sites around Jackson MS to build a house. I stumbled on the exact spot of our old drilling site, on Moncure Avenue! It was now a grassy field out in the countryside. I could picture the old rig there, the trailers where we lived, all the rig apparatus and mud pits. The first thing I thought of was: wow, I could tap into that old well and get a righteous source of heat for my house. (Too bad the winters in Mississippi aren’t cold at all.)
There are over 3 million abandoned oil and gas wells in the U.S. They call them “orphan wells” these days. Biden’s infrastructure bill, in fact, has funds to seal them off. (The Monguere Prospect was “plugged and abandoned,” like all non-producing wells drilled by Exxon and the other major producers ~ they pump concrete down, filling the well up down to well below the water table, then seal off the pipe.)
Instead of sealing the wells off, why not figure out a way to tap all that geothermal energy?
It’s very common in industrial processes to “accumulate thermal energy,” transforming via special heat exchanges, a low-temperature into a much higher temperature fluid, to then expand through turbines to generate power. The technical term for this is “renewable industrial process heat recovery.” For example, circulate a fluid with a much lower boiling point than water, create steam and use it to rotate a turbine. Steam power is how all fossil fuel and nuclear power plants work.