Oklahoma continues to be rocked by earthquakes which begs the question, what is the link between disposal wells and earthquakes? And does fracking cause earthquakes?
Before 2008, Oklahoma experienced around one noticeable earthquake a year. That number would quickly jump to almost one per day in 2014. Other states also started to see a rise in earthquakes.
The Link Between Disposal Wells and Earthquakes
In 2012, USGS geophysicist William L. Ellsworth, published a study linking disposal wells with the sudden increase in earthquakes in Oklahoma.
The abstract from the study states-
Earthquakes in unusual locations have become an important topic of discussion in both North America and Europe, owing to the concern that industrial activity could cause damaging earthquakes. It has long been understood that earthquakes can be induced by impoundment of reservoirs, surface and underground mining, withdrawal of fluids and gas from the subsurface, and injection of fluids into underground formations. Injection-induced earthquakes have, in particular, become a focus of discussion as the application of hydraulic fracturing to tight shale formations is enabling the production of oil and gas from previously unproductive formations. Earthquakes can be induced as part of the process to stimulate the production from tight shale formations, or by disposal of wastewater associated with stimulation and production. Here, I review recent seismic activity that may be associated with industrial activity, with a focus on the disposal of wastewater by injection in deep wells; assess the scientific understanding of induced earthquakes; and discuss the key scientific challenges to be met for assessing this hazard.
You can read the full study for more on what Ellsworth found.
A more recent study done in 2015 compiled data from all injection wells operating in the central and eastern United States. They looked at both wells used for enhanced oil recovery and at dispose wells used to dispose of wastewater from conventional oil and gas extraction or from hydraulic fracturing.
The scientists found that disposal wells were 1.5 times more likely to be associated with earthquakes, although the region contains far more enhanced recovery wells. The link was strongest at higher injection rates, above about 300,000 barrels per month. Other potentially important factors—such as the pressure at the well-head, the total volume of fluid injected, and whether fluid was injected near basement rock—did not appear to make much difference at a regional scale, the researchers say.
Read more about the study at Science Magazine.
In 2016, after the largest earthquake in Oklahoma’s history, disposal wells were ordered to shut down, though not all of them did. And even with the shutdown earthquakes have continued, which is not a surprise to scientists.
Studies have shown that the earthquakes could continue for more than 10 years even if all of the wells are shutdown. “Even after pumps are turned off, the water is still in the ground. It’s still sinking, and it’s still increasing fluid pressure.” – Ryan Pollyea, a hydrogeologist and assistant professor at Virginia Tech
Earthquakes in Oklahoma Continue in 2022
On January 31, 2022 Oklahoma was rocked by a 4.6 magnitude quake near Medford, Oklahoma. And a 2.5 magnitude quake was observed about an hour later in the same area.
In 2021, Oklahoma had 6 earthquakes of magnitude 4.0 or above, 41 between 3.0 and 4.0, and 578 between 2.0 and 3.0. There were also 1486 quakes below 2.0, those quakes are not usually felt by people.
With what we know it’s likely that Oklahoma will feel more earthquakes in 2022 and for years to come. It’s a good time for Oklahomans to become familiar with earthquake safety and be prepared for more.
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