Researchers at Southern Methodist University are studying how wastewater injection from oil and gas extraction impacts seismic activity in Texas in an effort to better predict where these earthquakes may hit.
Wastewater is a byproduct produced in the process of extracting oil and natural gas from the earth, which is then injected back into wells far beneath the ground.
Seismologists have connected wastewater disposal to earthquake activity in Texas, and SMU's research marks an effort to better predict where these earthquakes may hit and how strong they might be.
KERA's Bekah Morr spoke with SMU geophysics professor Heather Deshon, who worked on the study.
This interview has been edited for length and clarity.
Can you explain what wastewater injection actually is and how that process works?
Yeah, so there's a number of production operations that are common now that produce waste fluid. So if you hydrofrack, for example, you put fluid into the ground to help break up the rock in order to produce more oil and gas. And when that happens, you pull back out the water that you put in and also any natural waters in those rock formations where the oil and gas was. To get rid of that, you can't have it sitting on the surface. That's an environmental hazard. So you need to either recycle it or get rid of it somehow. And so what they do is they find rock units, generally those that are of rock types that suck in and can, basically like a sponge, hold fluid.
How does that wastewater injection contribute to the earthquakes that we've seen in Texas?
Again, I'm going to hearken back to this sponge analogy. When you start to fill a sponge, the fluid moves out, into your sponge. What you can't see is, if the sponge is already wet and you're putting more fluid into it, you actually create a pressure front. Eventually that pressure wave can interact with preexisting faults, and you're changing the stresses on those faults, and so those faults slip and release energy in the form of earthquakes.
What is important to understand in that scenario is that the faults were already there. The larger earthquakes in Texas that have been linked to wastewater disposal occur on faults that are hundreds of millions of years old. It's just that those faults appear to have some leftover energy, and the stress changes imparted by wastewater injection triggered some of those faults.
I've spoken to seismologists in the past, and it seems this connection between seismic activity in Texas and wastewater injection is pretty clear. So I'm curious why you think this research is still relevant and are people still unconvinced, despite the scientific evidence from your research team as well as others?
Originally this was controversial. It's much less controversial now. So, scientists in the oil and gas industry, the oil and gas industry itself, the regulatory organizations in Texas and Oklahoma, and other states with oil and gas activity are very much accepting of the fact that this can happen.
The research we just published is relevant in the broader scope of really understanding the physics behind how some faults are reactivated and not others. Even if you have an image of the subsurface that shows you faults, you know where your wastewater disposal is happening, you can't tell just from that which faults are going to generate earthquakes versus which faults won't generate earthquakes. We're all still working on the physics of the fault reactivation, because we still can't just create an image of the subsurface and tell you that, "this fault will fail and this fault won't fail, and when this fault fails, the magnitude is going to be X." We don't know how to do that yet.
