• The Heat Beat

Deep Geothermal Drilling: The Search for a Modern Howard Hughes

By Bob Metcalfe

ROP – Rate of Penetration – is a dominant determinant of geothermal economics. And even more so as we drill deeper, say down to 10km into hot dry rock (HDR) to reach 350C. As we aim to harvest Earth’s abundant natural heat for the production of cheap, clean, and safe baseload electricity, to reach global scale we need new drilling technologies to increase ROP in HDR by, say, a factor of 10.

You may have heard of Howard Hughes Jr., who became “the richest man in the world” during the Texas Oil Boom. But you’ve likely not heard of his father, Howard Hughes Sr. The Harvard drop-out (another one of those) founded Hughes Tool Company in (of course) Houston, Texas and invented the tricone rotary rock drill bit.

The Hughes drill bit increased oil well drilling ROP by a factor of 10, and Howard Hughes Jr. was 18 when he took over the Company after his inventor-entrepreneur father died young. These days, the Hughes Tool Company lives on inside of General Electric, and much of the rest of the Hughes fortune, $20B+, endows the immensely important Howard Hughes Medical Institute.

ROP x 10 would be a game-changing proposition in the pursuit of deep geothermal. In the innovation pipeline for ‘break out’ deep drilling technologies flows ideas like mm wave, laser, hypersonic and plasma drilling techniques, to name a few. And behind each concept is an entrepreneur convinced that they hold the key to fast, deep and cheap geothermal drilling.

So will the next Howard Hughes please stand up?

One ascendant candidate hails from another drilling family, this one out of Western Australia. Ben Strange’s family has for four generations been drilling for water, mineral exploration, and more recently geothermal. Ben has plans to cut geothermal drilling costs by 70% as CEO of Strada Global, a drilling startup headquartered in Jersey.

And when I say Jersey, I do not mean New Jersey. Strada is headquartered on the Channel Island of Jersey between England and France. The Bailiwick of Jersey is a British Crown dependency located on an island near Normandy. European startups incorporate in Jersey for the same reasons Silicon Valley startups incorporate in Delaware, so they say. But back to Ben.

Ben’s specialty at Strada is percussion drilling, the kind dominant before Howard Hughes came up with rotary drilling. Ben has worked with mud, water, and air “hammers” that crush rock and brings cuttings up to the surface. Strada’s technology leverages proprietary “dual circulation” water and air drilling hammers.

Let me sketch my layman’s understanding of Strada’s dual circulation percussion drilling: The drilling is accomplished by crushing the rock with a hammer powered by fluid (mud, water, air) through a tube-in-tube drill string. During drilling, the two tubes carry two fluids down to the bottom, one for drilling and the other for clearing the cuttings. The cuttings are returned to the surface in the borehole outside the two tubes. An animation of the dual circulation method for your reference here.

To accomplish geothermal heat production from a well, cold working fluid is sent down the outer tube to be heated and returned to the surface through the insulated inner tube. This is straight-up-and-down closed-loop geothermal heat harvesting. There are other options, but this is Ben’s favorite model right now.

Ben claims that this method of drilling and production will greatly increase ROP. Right now he’s getting between five and ten meters per hour through HDR. And the increase of ROP enables deeper, straight down wells without fracked reservoirs. This reduces the complexity (and cost) of the system.

So, just how far along is Strada in developing its high-ROP, dual circulation percussion drilling and production technologies? Ben reports that Strada has so far raised about $10M and has already drilled two air-hammered 4.5km wells. Here is Strada’s TDC chart contrasting current drilling ROP (orange) versus Strada (yellow and green) in meters drilled.

I told Ben it was our aim at GEO to cost effectively reach 10km and 350C for the prize of enabling globally available baseload electricity production. He answered, “No problem.” And he added there is a lot low-hanging fruit on our way to baseload electricity generation.

Looking at temperature at depth in the US at 5.5km, one has to ponder how much usable and commercially viable geothermal energy is available globally at 4.5km. Ben noted that they stopped drilling at 4.5km due to contractual requirements – not due to technical limitations or difficulties. But it’s clear looking at the US maps that the prize is deeper and hotter. Perhaps Strada can reach 10km and 350C with its dual circulation hammers, no problem. I’m on the cheerleading squad.

Ben has been considering how Strada will do business, and there are several possibilities. Strada might sell drills. Or own wells. Or license patents. Ben likes the service company model where Strada would bring Strada drills and Strada services on site to drill customer wells.

A note on the need for flexible business models as flourishes of advanced geothermal technologies become commercially viable: today in the oil and gas industry, drilling services are billed by the day. But if you are a next generation ultra fast driller, that model makes little commercial sense. Ben would like to charge instead per meter drilled. Right now, that rate would be about $2,340 per meter.

Strada is now seeking to raise something like $50M to drill production wells. One avenue would be to drill a 10km geothermal well for say $20M. Another avenue would be to drill 30 shallower wells. These would become producing geothermal assets.

Good luck to Ben and Strada on becoming The Next Howard Hughes. We can use the ROP on the way to our geothermal future.

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