Exploring Geothermal: Hydraulic Fracturing, Enhanced Geothermal, and More

Great podcast on all the cool stuff happening with geothermal! I appreciate the frank conversation about geothermal and hydraulic fracturing (aka fracking), which I find is often misunderstood.

Lets look at the details in a quick thread: https://t.co/aIyU60l8mn

— Zeke Hausfather (@hausfath) April 1, 2023

To start with, its worth pointing that geothermal (and, particularly, newer enhanced geothermal approaches) are benefitting from many of the technologies that enabled the shale gas boom. In many ways, low-cost horizontal drilling is more important than hydraulic fracturing here!

— Zeke Hausfather (@hausfath) April 1, 2023

Not all enhanced geothermal approaches use hydraulic fracturing at all (though, as Jamie Beard notes on the podcast, some who do try and dance a bit around the issue by inventing different terms for it).

— Zeke Hausfather (@hausfath) April 1, 2023

More central, though, is despite the scary sounding term, not all "fracking" is inherently bad. There are three main risks associated with fracking today:
1) climate impacts of cheap gas
2) water contamination
3) induced seismicity (e.g. earthquakes)

— Zeke Hausfather (@hausfath) April 1, 2023

The first concern clearly does not apply to enhanced geothermal, as its not producing any natural gas (as an aside, the issue of fracking and climate is complicated given its role in killing US coal, as discussed in detail in the thread below). https://t.co/bF1LvyoYUW

— Zeke Hausfather (@hausfath) April 1, 2023

The issue of water contamination is complicated, and can involve the chemicals used in the fracking process (though these concerns are often a bit exaggerated), the contamination of recovered fluids by heavy metals underground, and methane seeping into the water table.

— Zeke Hausfather (@hausfath) April 1, 2023

For geothermal, some of these concerns still apply: you can (but don't necessarily need to) use carcinogenic chemicals for fracturing, but you can also use supercritical CO2 or just sand and water. These are only used during initial fracturing, and are less of an issue after.

— Zeke Hausfather (@hausfath) April 1, 2023

Heavy metal contamination of resurfaced fluids is a bigger issue, though this can be addressed in closed systems where fluids are recirculated. And there is generally no risk of methane seepage into groundwater since there is little if any down there.

— Zeke Hausfather (@hausfath) April 1, 2023

There is also the fact that the rocks accessed for enhanced geothermal are less likely to be below groundwater deposits – or proximate to where people live – compared to shales that gas is extracted from.

— Zeke Hausfather (@hausfath) April 1, 2023

On the topic of induced seismicity, while this is a real concern, the largest earthquakes associated with gas production are not due to the fracking process itself, but rather the injection of wastewater from fracking into disposal wells. https://t.co/PQ9Tr5POQ4

— Zeke Hausfather (@hausfath) April 1, 2023

The issue here is that the water used in fracking operations gets contaminated with dangerous levels of heavy metals from the underground rocks, and cannot be disposed of in streams or rivers on the surface. Rather, its disposed of in wastewater injection wells.

— Zeke Hausfather (@hausfath) April 1, 2023

For closed geothermal systems the disposal of wastewater is generally not a concern. And while small earthquakes are possible from geothermal operations, effective modeling can help avoid these.

— Zeke Hausfather (@hausfath) April 1, 2023