[doodlebugging]

Geophysicist and former MWD engineer here. I agree. Even if you fuse everything that you penetrate to the annulus of the borehole, the material properties of the fused annular ring will vary as you cross formation boundaries based on the mineral composition of the formations being drilled. You may have some nice silicon glasses through a clean sandstone that transition quickly to inhomogeneous glass from a silicon-poor limestone. That has to create zones of weakness along the annulus and as you drill (zap) deeper it becomes even more critical to stabilize the borehole.

I can see this being a lot like conventional drilling to a point with several bit trips or casing runs necessary until you reach a point where the borehole tends to collapse due to overburden pressure, especially in overpressured environments where well control is critical, and it is no longer possible to trip out and run casing before the borehole collapses in the newly drilled interval.

What happens if your proposed well encounters salt or other evaporites? A lot of questions could use answers and those answers only come from poking holes in the ground so maybe if they throw enough money at it they can determine where this method can be useful. That would be the most valuable result of all this.

This looks useful for near surface stuff but for ultradeep wells looks like it needs some experimentation.

[pavel_lishin]

Are there places on Earth where it's mostly-homogenous "good stuff" all the way down? Could they avoid some of these problems - salt pockets, limestone - by being very picky about where they drill, avoiding (e.g.) places where there used to be ocean?

[jofer]

Even if it's homogenous, you have steadily increasing stresses with depth. This occurs for perfectly uniform materials as well. If you can't offset these to keep the hole open, it collapses.

Rocks are very weak in tension, despite being very strong in contraction. It's the reason you can break rock with a hammer or the reason ancient quarries were able to work by pouring water on wood pegs in rocks. It's also the reason concrete needs rebar to reinforce it (steel is very strong in tension, so the two combined are exceptionally strong). Keeping a hole open requires strength in tension as well as strength in compression.

Drilling mud accomplishes this by being roughly the same density as the rock, so it offsets the stresses that are trying to close the borehole that steadily increase with depth due to the increasing amount of rock above. Drilling mud keeps the borehole open until you can put in casing to support it.

This is exactly the same reason why it's difficult to build a submarine that can go to very large depths in the ocean. To put up steel walls (casing) to keep it open, you have to stop drilling and cement in casing - you can't do that as you drill. So drilling mud is a key part of being able to drill efficiently. Otherwise, you'd need to stop every few tens of meters and spend _days_ setting casing before being able to drill again.

Regardless, there is nowhere on earth where things are homogenous over very long distances. Simply put, even relatively uniform rocks can have very significant variations in physical properties. Many relevant properties (e.g. permeability - how well fluids can move through) vary over _tens of orders of magnitude_ naturally. So "uniform" can still mean "only varies by a few orders of magnitude". There are places where you can reasonably avoid non-silicates, but you're going to hit tons of other issues due to fundamental heterogeneity.

[specialist]

My impression is Quaise's maser (?) drill thingie would be used for granite. Which is increasingly a challenge for geothermal (going deeper, longer).

Can types of drill bits (heads?) be swapped out? So use the super diamond bit to get started, then switch to Quaise's maser once you reach granite.

Just guessing. Am noob. Am just trying to follow along.

eg Most recent Volts podcast episode: An update on advanced geothermal w/ Tim Latimer of Fervo Energy.

[cnote337]

You'd need to trip out of hole for it, but that isn't really a problem. I know the video acts like tripping is the end of the world, but it's a standard day to day practice offshore. Everytime something breaks or dies down hole, or you finish a section of hole you need to case, you have to trip.

So yes, you could swap the two out. But we already have bits that are good at drilling hard rock (granites, etc) they're called tricone bits. They more so crush the rock than cut it. And they look badass.

[gosub100]

Could you avoid the problem by drilling down a fixed length, carving out a room or supply area, drilling laterally, and then drill vertically again?

[BigParm]

You don't have to trip if your cutting tool never wears out. You fix it to the end of a casing string and just keep adding lengths. The hole is cased as soon as it's drilled.

[cnote337]

And so when you go to cement your casing in place, you, what?, cement your brand new indestructible quaise 'drill bit' in the hole?

Sorry, I think not. Neat idea, but there's big holes in that in practice.