Enhanced geothermal: deeper, faster, more... sideways? (part 2)

This is part 2 of our series on geothermal energy. If you missed part 1, read it here first.

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Last week, we talked about old-school, traditional geothermal engineering: taking advantage of those rare places in the world where steam naturally rises up from the ground to generate electricity. For trad geothermal, all you gotta do is drill a couple holes to a depth of one to two miles, pump water down there, let it get hot, and use the superheated water that returns to the surface to create steam. Steam can power a generator, thereby making electricity.

One problem: there aren't enough steamy places in the world to go around. I wish there were! America has no spa culture.

So what's a modern-day geothermal engineer to do?

Drill deeeeeper

Remember the 'geothermal gradient'? The deeper underground you go, the hotter it gets. This holds true no matter where you are on the planet.

More heat means more steam means more electricity. In theory, you could drill down to where the rocks are as hot as a volcanic spring and replicate the old-school geothermal system without needing a volcano.

Such a system would last you... pretty much forever! The amount of heat trapped deep underground is, for humanity's purposes, infinite. The sun will burn out long before we run out of heat in the Earth.

The promise of 'geothermal anywhere and forever' is, needless to say, enticing. So for many years now, enterprising geothermal engineers have been trying to solve the complex puzzle of reducing the upfront cost of deep drilling enough to make a tidy profit on boundless electricity generation.

You might think such a project would pay for itself eventually, what with geothermal being an infinite energy resource and all. Maybe it would, eventually.

But drilling is expensive. To drill even a mile underground, you'll need, first of all, a massive freaking drill. A drill that doesn't even look like a drill. A drill that looks like an erector set:

What do you suppose it costs to rent one of these puppies for a day? How about for 75 days straight? While paying an expert crew?

Millions upon millions of dollars, is the answer.

So, yeah, you might recoup your upfront costs after, like, forty years. But the Business Leader of Today doesn't have that kind of time. They want results now, damnit!!

Thankfully—sort of—someone out there's been working very hard to improve drilling technology. Someone with deep pockets and a vested interest in scale, efficacy, and cost reduction. Someone who drills, baby, drills.

That's right: oil and gas companies.

The seven-layer dip

In the late 1800s, some petroleum engineers formed a clever hypothesis: if they drilled down to an oil and gas reservoir, and then turned their drill sideways and drilled some more, they'd be able to reach way more oil and gas than they would by just drilling more vertical wells.

They were onto something.

Imagine, if you will, a seven-layer dip. Let’s say you didn't care about the dip's top layers (you're not a black olive guy): you just want to extract the refried beans at the bottom. You could stick a straw into the dip and suck out a bean or two at a time. You could even do this a bunch of times, with a bunch of straws. But it’d be a lot more effective to use a single bendy straw and extend the bendy section across the dip at bean-depth.

Why, you’d practically be in bean heaven!

The hypothesis was sound. Drilling horizontally, however, proved way harder than drilling vertically. How do you turn a drill sideways when it's hundreds or thousands of feet underground? How do you drill accurately, staying within a shifting reservoir, when you can't see where you're going?

It took many decades and a bevy of technological innovations to make horizontal drilling economically viable. It wasn't until the 1980s, after a succession of improvements to drilling motors and telemetry, i.e. measuring instruments, that horizontal drilling for oil and gas took off.

Then, in the early 1990s, fracking exploded.

What da frack is fracking?

One day, I hope, we’ll look back on this as one of the great ironies of the clean energy transition: without the fracking boom, Enhanced Geothermal Systems (ESG) never would have happened.

But, uh, what is fracking, again, exactly?

Fracking is short for ‘hydraulic fracturing’: using a pressurized fluid to crack open underground rocks—typically shale—so that they release the oil and gas trapped inside of them.

Oil and gas aren't sloshing around in shale as if it were a geode with a big central cavity. Rather, if you put shale under a microscopic, it would look like a sponge. Oil and gas clog up its pores. Ew!

Have you ever used a power washer to clean the side of a house? Fracking is kinda like that… except you do it thousands of feet underground using literally millions of gallons of freshwater, mixed with quartz sand and a harsh chemical fluid, that occasionally contaminates the local water supply.

But to really make fracking effective, you gotta know how to drill sideways. Doing so provides access to way more shale rock—just like in our seven-layer dip.

Once you've cracked open some shale, a portion of the mixed fracking fluid/oil/gas makes its way back to the surface. If you're lucky, you'll recover 50% of the millions of gallons of fracking fluid you just injected into the earth. If you're unlucky, you may only recover 15%. The rest of that fluid? Why, it gets to live in the earth forever.

These days, the natural gas recovered from fracking may get liquified and shipped across the ocean on a big gas-guzzling boat to be burned in Europe or Asia. America is all in on exporting Liquified Natural Gas (LNG) to the world, which means we're gonna keep on frackin' forever—unless someone puts a stop to it.

That's fracking in a nutshell.

(Actually, I skipped over a bunch of stuff. If you want to learn more, including the many ways fracking can be terrible for the environment and why it's massively accelerating climate change, read this NRDC Fracking 101 guide.

The dawn of Enhanced Geothermal Systems

The fracking boom took horizontal drilling to the next level. Billions and billions of dollars have been spent by energy companies to improve their horizontal drilling capabilities, enabling them to drill faster, farther, and more accurately than ever before.

Meanwhile, a modernized approach to geothermal engineering was slowly gaining momentum. It's called Enhanced Geothermal Systems (EGS for short).

EGS is like trad geothermal engineering sans active volcano. It requires drilling way down to where the rocks get real toasty, and then tapping into that heat source.

There are a few ways to tap into hot rocks. One commonly used approach is—wait for it—hydraulic fracturing.

That's right: we're frackin' hot rocks.

Blasting granite with pressurized water can expand existing fissures within the rock, thereby allowing water to circulate through the cracks until it gets nice and superheated and rises up to the surface, at which points it gets plopped into a heat exchanger to convert a second liquid with a lower boiling point into steam.

To be clear: though they share some technology, EGS is far better for our planet than oil and gas drilling and fracking. We'll talk about why that is soon.

But for now, imagine the possibilities of combining hot rock fracking with horizontal drilling. Man! If someone could just figure out how to do it relatively cheaply, why, we'd have access to bountiful, clean, 24/7 energy almost anywhere in the world.

Fervo Energy for the win

In 2017, a former drilling engineer named Tim Latimer founded an Enhanced Geothermal Systems company called Fervo Energy.

Tim wasn't the first person to suspect horizontal drilling could be applied to geothermal engineering. That had already been done to varying degrees for decades.

But Tim and co. may well be the first to attempt EGS on a scale that mirrors—and eventually outpaces—what oil and gas companies have made possible.

Fervo set up shop in the Utah desert, where a few thousand feet underground lies a very thick layer of granite.

Granite is a great choice for EGS: it's abundant, a decent thermal conductor, brittle enough to be 'hydraulically stimulated', and it contains small amounts of the radioactive elements that continuously generate new heat within the Earth.

Fervo's strategy is straightforward: drill vertically, then horizontally, then inject water to expand fissures in the granite; the water circulates through the hot rocks in a classic closed-loop, binary cycle system, complete with heat exchanger and steam-powered turbine.

Easy enough, right?

Not exactly. Granite may be brittle enough to frack, but it's still a hell of a lot harder than shale. This makes deep drilling very, very difficult.

The first time Fervo drilled a well, it took 75 days and cost $13 million. They broke 13 bits drilling 3,000 horizontal feet.

Diamonds on the tips of their drills

But like any decent startup, every time something broke, Fervo tested out a new approach. They made a series of upgrades to their Polycrystalline Diamond Cutter (PDC) drill bits, which use synthetic diamonds—the hardest material on earth—to scrape away rock.

They had another bright idea, too: Fervo lays fiber optic cables along the entire length of their wells to better understand what the terrain looks like deep underground. Here's Tim providing the nitty gritty details (slightly edited by me) on how this neat technology works:

We send laser pulses down the fiber optics. Because there's impurities in all fiber optics, those laser pulses get reflected back to the surface, and we can map out what those reflections look like to get a very clear picture of what's happening in the subsurface.

When stuff gets hot, it expands, right? When stuff gets cool, it contracts. So if we're trying to figure out, for example, how much fluid flow is going down each port we've opened up into the reservoir, we can actually look at the real-time temperature change, because along that fiber optics, if it cools off a little bit, all those impurities get a little bit closer together.

We can measure in real time the temperature along the entire well. And from that, we can figure out how much flow is going where, how much is getting over to the other wells we've drilled. We can map the fluid pathways in between these wells hundreds of feet out into the rock. And this data set allows us to actually understand what's happening in geothermal reservoirs far beyond any data we've ever had access to before.

By their 10th attempt, Fervo managed to drill a lateral section through 5,000 feet of solid granite. Only one drill bit broke, and it took them just 17 days.

As of February, 2025, Fervo is drilling wells for under $4 million a pop.

Key differences between frackers and Fervo

1. Drilling depths

Frackers typically drill 5,000 to 10,000 feet down, and then the same length sideways—though the industry is trending towards longer and longer horizontal wells. 5–10k feet is the depth at which you find the most shale, so there’s not an incentive for them to drill deeper.

Fervo, on the other hand, wants to go deep like Jerry Rice (sports reference) to reach progressively hotter and hotter rocks.

As of February, 2025, Fervo's drilled down to 9,000 feet, a depth where granite reaches temperatures around 400°F. They plan to drill even deeper next year, with wells reaching 11,000 feet and temperatures of 450°F. After that? The sky’s the limit, so to speak. 

As for Fervo's horizontal drilling: they’ve reached lengths of 5,000 feet across, with plans to extend farther as their technology improves.

2. Fluids

Frackers use a mixture of ~90% freshwater, chemicals (which they are sometimes legally allowed not to name), and something called a 'proppant'—typically quartz sand—to keep the cracks they make propped open. This heady brew is called ‘slickwater.’

Fervo uses water.

4. What they do with their used fluids 

Fracking fluid, once it’s been returned to the surface and processed, has no value, so it typically gets injected back into the ground or abandoned in an open-air pit. It's possible to treat fracking fluid, but it's expensive.

Fervo can reuse the same water over and over again in their closed-loop system.

5. Environmental impact

Fervo’s Enhanced Geothermal System is better for the environment than drilling and fracking oil and gas for a variety of reasons:

A. It’s not extractive: Fervo isn’t pulling fossil fuels out of the earth in order to burn them in a power plant somewhere halfway around the world.

B. They don’t leak methane: Because they work in granite and not gassy shale, there's no methane gas being unearthed. Methane, Green Juice readers know, is over 80 times worse for our climate than CO2, and it leaks fucking everywhere, all the time. Over half of methane emissions since 2008 can be attributed to shale gas operations.

C: Fervo’s wells should work for many years: When a fracking well has extracted all the oil and gas in the area, guess what? They let it rot and build a new one. By contrast, Fervo recirculates their water underground over and over again. They expect each well they drill to last upwards of 30 years.

This sure sounds like a lot of work...

A reasonable question: why are we boring holes 10,000 feet underground when solar panels, wind turbines, and batteries are cheap and efficient?

Because there’s enough heat under the Utah desert alone to power all of North America, and we're nowhere close to meeting our need for clean energy.

Fervo’s test pilot was able to produce 3 megawatts.

For their next project, they plan to jump up to 500 megawatts. They say it'll be operational by 2028.

In the next two or three years, they anticipate drilling to depths of 10,000–15,000 feet.

EGS is a worthwhile pursuit. And it’s happening today: Fervo just announced a 31 MW power purchase agreement with Shell. (Why Shell is buying up clean energy is a topic for another post.)

Will Fervo save the world? I'm not sure.

But I know this: Fervo isn't the only newfangled geothermal game in town.

Next week, we’ll showcase a few other companies doing crazy shit deep in the netherworld. Plus, we'll answer all your burning geothermal questions, like, 'Uhhh does this cause earthquakes?'

(Got a question? Hit me up: jon@greenjuice.wtf)

Thanks again to Kim Vinet for keeping me straight.