The big breakthrough seems to be making drill bits out of a composite material formed from diamond and tungsten carbide.[1] One of their bits lasted through 25km of drilling. (Not one hole, re-used for multiple shallow holes.) That's encouraging. The geothermal people only need to go down 10km. Being able to do much of the job without backing out the drill string, one pipe section at a time, to change the bit is what seems to yield the cost estimates in the original article.
The next problem is to get everything at the down-hole end up to that level of reliability. Which is why the author talks about seal problems in mud-powered drilling motors. For the geothermal application, they just want to drill straight down, so they don't need all the fancy stuff used for slant and horizontal drilling.
So there remain some grungy, hard, and important problems to solve, like a seal material that will work better at high temperatures. Such things exist.[2]
This is encouraging.
The article points out that this isn't like hunting for oil and gas pockets; if you have roughly the correct overall geology, there will be hot rock down there anywhere you drill. This upsets some financial models, where drilling the first well in a new area is more like a VC-funded high-risk high return project. You're really drilling for the valuable info that oil or gas is there, not for the oil or gas from the exploration well.
Deep geothermal is going to be dull, boring (literally), usually successful, and profitable over a long period but not in the short term. Great for regulated utilities.
The big breakthrough seems to be making drill bits out of a composite material formed from diamond and tungsten carbide.[1] One of their bits lasted through 25km of drilling. (Not one hole, re-used for multiple shallow holes.) That's encouraging. The geothermal people only need to go down 10km. Being able to do much of the job without backing out the drill string, one pipe section at a time, to change the bit is what seems to yield the cost estimates in the original article.
The next problem is to get everything at the down-hole end up to that level of reliability. Which is why the author talks about seal problems in mud-powered drilling motors. For the geothermal application, they just want to drill straight down, so they don't need all the fancy stuff used for slant and horizontal drilling.
So there remain some grungy, hard, and important problems to solve, like a seal material that will work better at high temperatures. Such things exist.[2]
This is encouraging.
The article points out that this isn't like hunting for oil and gas pockets; if you have roughly the correct overall geology, there will be hot rock down there anywhere you drill. This upsets some financial models, where drilling the first well in a new area is more like a VC-funded high-risk high return project. You're really drilling for the valuable info that oil or gas is there, not for the oil or gas from the exploration well. Deep geothermal is going to be dull, boring (literally), usually successful, and profitable over a long period but not in the short term. Great for regulated utilities.
[1] https://palmerbit.com/
[2] https://allsealsinc.com/HighTemperatureGaskets.html