Can we predict earthquakes in Texas? SMU researchers study wastewater injection to find out

Researchers at Southern Methodist University are studying how the discharge of wastewater from oil and gas production affects seismic activity in Texas in order to better predict where these earthquakes might occur.

Wastewater is a byproduct of oil and gas production that is then pumped back into wells deep underground.

Seismologists have found a link between wastewater disposal and earthquake activity in Texas. SMU's research is an attempt to better predict where these earthquakes might occur and how strong they might be.

KERA's Bekah Morr spoke with Heather Deshon, a professor of geophysics at SMU who collaborated on the study.

This interview has been edited for length and clarity.

Can you explain what wastewater injection actually is and how this process works?

Yes, there are a number of production processes that are common today that create waste fluid. For example, hydraulic fracturing is where fluid is injected into the ground to break up the rock and extract more oil and gas. And that's pulling out the water that's injected and also the natural water from the rock formations that held the oil and gas. To get rid of that, you can't leave it on the surface. That's an environmental hazard, so you either have to recycle it or dispose of it somehow. And so you look for rock units, generally those made of rock types that can soak up fluid and basically hold it like a sponge.

How does this wastewater discharge contribute to the earthquakes we have experienced in Texas?

I'll go back to the sponge analogy again. When you start filling a sponge, the fluid moves out, into your sponge. What you can't see is that when the sponge is already wet and you put more fluid in, you're actually creating a pressure front. Eventually, that pressure wave can interact with faults that are already there, and you're changing the stresses on those faults, and so those faults slip and release energy in the form of earthquakes.

What's important to understand in this scenario is that the faults were already there. The larger earthquakes in Texas that have been linked to the wastewater discharge are occurring on faults that are hundreds of millions of years old. It's just that those faults seem to have some energy left, and the stress changes from the wastewater discharge triggered some of those faults.

I've spoken to seismologists in the past and it seems that this link between seismic activity in Texas and wastewater discharge is pretty clear, so I'm wondering why you still think this research is relevant and whether people are still not convinced despite the scientific evidence from your research team and others?

Originally, this was controversial. Today, it is much less controversial. Scientists in the oil and gas industry, the oil and gas industry itself, regulators in Texas and Oklahoma and other states with oil and gas activities are quite accepting of the fact that this can happen.

The research we just published is relevant more broadly to really understanding the physics behind how some faults reactivate and others don't. Even if you have an image of the subsurface showing faults, you know where your wastewater disposal is, but you can't tell from that alone which faults will trigger earthquakes and which won't. We're all still working on the physics of fault reactivation because we can't yet just take an image of the subsurface and tell you, “This fault will fail and this fault will not fail, and when this fault fails, the magnitude will be X.” We don't know how to do that yet.