‘Drill, Baby, Drill’ Is the Future

Dig deep enough and, no surprise, it’s hotter than hell down there. Isotope reactions in the mantle under the Earth’s crust generate 20 terawatts of constant heat flow. Typically, the temperature rises about 25 degrees Celsius for every kilometer, or 75 degrees Fahrenheit for each mile, and more the deeper you go. The steam wafting out of hot springs in Yellowstone National Park or Iceland, places where the Earth’s crust is thin, shows how much heat the mantle gives off.

We already have a good-sized surface geothermal industry in the U.S. For $15,000 to $30,000, you can hire someone to dig a few hundred feet and install a heat pump that circulates heated water to keep your house cozy.

But that’s just scratching the surface. There is huge upside to digging down miles and injecting water into underground reservoirs—think radiators—and then the heated water is pushed back out to generate steam and electricity. It’s carbon-free—clean, green and mostly unseen.

The trick is to get a large enough surface area to do the heat exchange. A typical vertical oil well might have 1,000 to 10,000 square feet of surface area. But it turns out that the same thing that’s been perfected over the past 30 years to make America energy independent can also increase that surface area—horizontal drilling and hydraulic fracturing.

I called one of the industry pioneers, University of Texas engineer Mukul Sharma, who is sometimes called the Frack King (get it?) and has a startup named Geothermix that develops enhanced geothermal systems.

Mr. Sharma walked me through the process. Millions of oil and gas wells have been drilled in the U.S. over the past century. Maps exist that show the thermal conductivity of underlying rock by region—suggesting how deep you’d have to drill to get a temperature hot enough to generate cost-effective electricity, typically 0.5 to 4 miles down. After drilling down you can then drill horizontally and hydraulically fracture the rock to create an underground reservoir. With this technique you could get 10 million to 20 million square feet of surface area for the heat exchanger, thousands of times more than a standard well.

Mr. Sharma thinks we’ll have several commercially viable deep geothermal systems operating in the next five years, maybe costing $10 million to $15 million each, from his company and others like Sage Geosystems and Fervo Energy. He thinks by 2030 we’ll have second- and third-generation systems operating much more efficiently, just as fracking constantly gained in output as technology improved.

The promise of geothermal energy keeps getting better. The deeper you drill, the hotter the rock, and at maybe 10 kilometers, temperatures can reach 373 degrees Celsius or higher. The water that emerges is what physicists call “supercritical,” which means it holds more energy and can be 10 times as efficient doing heat exchange. A lot of invention is still required, especially for high-heat materials and drills that can operate at such high temperatures—not a trivial problem, but not insurmountable. For now, Mr. Sharma says, “the costs go up exponentially as you dig deeper and hotter.” A supercritical-water geothermal system might cost $50 million. But it might be worth it. Some scientists even think drilling into volcanoes might make sense.

Further in the future, we may not even need to fracture the rock, but instead use horizontal drilling and pipes to run fluid through closed-loop systems, with the heat exchange done through the pipes. You could do this anywhere if you drill deep enough, under New York or any other city.

So why are so few talking about deep geothermal? Eco-warriors seem to pine only for solar panels, carbon sinks and bird-slicing wind turbines. Maybe because anything having to do with drilling is considered dirty, even if deep geothermal is carbon-free. The knock on enhanced geothermal systems is the same as for fracking: Critics go on about the risk of seismic activity. But according to Mr. Sharma, that’s a canard. He says seismic activity from fracking wells is “fairly uncommon” and would be even less so with deep geothermal, because the wells are much deeper and you’re merely “circulating fluids” after the initial drilling to create the underground hot reservoir.

It’s early but, like fracking, this technology could change the energy industry over the next 20 to 30 years. Those that can absorb the risk could see huge rewards. Mark Twain once said, “Go to Heaven for the climate, Hell for the company.” Maybe toward hell for both. Drill, baby, drill.

Write to [email protected].