J.C. Moore Online
Current Events from a Science Perspective

Posts Tagged ‘Induced Seismicity’

The Problem with Addressing Induced Earthquakes

Thu ,04/02/2021

Many people believe that man’s activities are so inconsequential that they could not possibly induce earthquakes. However, there have been cases as far back as the 1960s where the only reasonable explanation was that earthquakes were being induced by disposal wells. When the U.S. Army’s Rocky Mountain Arsenal built a disposal well in 1961 to get rid of waste fluids, the seismic activity in the area increased. The well was plugged and the earthquakes stopped. A study by the U.S. Army Corps of Engineers and the U.S. Geological Survey (USGS) determined that a “deep, hazardous waste disposal well at the Rocky Mountain Arsenal was causing significant seismic events in the vicinity of Denver.”  Another case of induced seismicity occurred in Kansas in 1989 near Palco, northwest of Hays. The largest earthquake had a magnitude of 4.0 and caused some minor damage. Several injection wells, used for the disposal of wastewater from conventional vertical oil wells, were located near a deeply buried fault zone. Investigators concluded that the earthquakes were likely induced.

Recent research shows that disposal wells are causing the earthquake swarms in Kansas and Oklahoma. There were only two or three quakes a year in Kansas and Oklahoma before 2009. That was when fracking operations started in the area and each day millions of gallons of wastewater were pumped into disposal wells. By 2015, there were about 4500 Class ll disposal wells in Oklahoma and about 1600 and Kansas. Some Class II disposal wells, which are associated with oil and gas production, were injecting as much as 15,000 barrels of disposal fluids daily.

The graph below shows the number of earthquakes in the central United States from 1973 to 2019. The number of earthquakes, mostly in northern Oklahoma and southern Kansas, increased dramatically as the number of disposal wells increased after 2009.  When, in 2015, the Oklahoma Corporation Commission (OCC) and the KCC started putting limits on the amount of disposal fluid that could be injected into wells near earthquake epicenters, the number of earthquakes fell off appreciably. However, that decrease may not be true for the magnitude (M).

Figure 1.

Earthquake intensity is measured on the Richter scale. The Richter scale is a logarithmic scale, with an M3 .0 quake being 10 times stronger than an M2.0 quake, and it dissipates 32 times more energy. Earthquakes over M2.0 can be felt, those over about M3.5 can cause minor damage, and those over M4.0 are strong enough to do structural damage to buildings and infrastructure. An earthquake in Oklahoma near Pawnee, in 2016, was an M5.8 earthquake. It caused millions of dollars of damage in Oklahoma, an estimated $600,000 in damages 110 miles away in Wichita, and was felt as far away as Illinois.

Most disposal wells are drilled into the Arbuckle zone as it is porous enough to take up the fluid. The Arbuckle zone lies under the region at about 2700 feet.  The pressure of gravity on a column of saltwater that long exerts a pressure of over 1500 psi at the bottom. The drilling fluid, under that much pressure, has to go somewhere so it migrates outward from the injection wells.  As the fluid migrates, it causes an increase in pressure in the zone, labeled dP. When the increase in pressure, dP, reaches about 50 psi, it starts destabilizing ancient faults, causing earthquakes. The graph below shows how the dP has changed in south-central Kansas over the past several years, and its increase can be identified with new clusters of earthquakes.

Figure 2.

The pink area (dP > 50 psi) began increasing near the disposal wells in Harper and Sumner Counties and, by 2014, earthquakes were beginning to start there. The pink area reached Reno County (RN) in 2017. Since then, that area has experienced 126 earthquakes of a magnitude 2.0 or greater – and the magnitude seems to the increasing over time.  Hutchinson experienced an M4.2 quake in 2019  and an M4.6 earthquake on 01/19/2021, which was felt in 20 states. In 2018, Burrton, situated between Hutchinson and Wichita, had an M4.2 earthquake. One of Burrton’s school buildings was damaged and hasn’t been used since then.  The maps only go to 2017, but the disposal fluid has been migrating outward since then, with the pink area, dP > 50, likely reaching Wichita in 2020. That’s when earthquakes began occurring in Wichita.

The Wichita area has had very few earthquakes in the past. In the period1990-2019, there was only one quake near Wichita, about 15 miles east. However, beginning in November 2020, a cluster of earthquakes occurred with the epicenters under Northeast Wichita. There were 21 earthquakes greater than M2.5, with the largest of those an M3.9 on December 30th, which could be felt as far as 30 miles away. Minor damage occurred and Wichita citizens became concerned that there might be more and stronger quakes. Many people thought the earthquakes were caused by disposal wells in the area. The KCC and the Kansas Geological Survey (KGS) investigated and found that there were six disposal wells within a 6 mile radius and together they were only injecting a modest 9000 barrels of wastewater a day. So, the investigators concluded that there was very little link between the earthquakes and the disposal wells near Wichita.

And, the investigators were mostly right. The earthquakes were likely caused by disposal wells much further away. In 2016, the KCC limited the volume of fluid injected into disposal wells within a 6 mile radius of an earthquake’s epicenter. That 6 mile distance, establish for wells south-central Kansas, is apparently not adequate. A 2018 research study by the American Geophysical Union concluded that the earthquakes that occurred in Hutchinson were caused by an increase in fluid pressure from wells that were as much as 55 miles away. The graph of dP versus time from the KGS (Figure 2.) makes it clear that the increased pressure migrating outward from disposal wells correlates with the clusters of earthquakes.

The induced earthquakes have done millions of dollars in damage to homes, public buildings, roads, and bridges. The disposal well companies should be liable for the damages. Lawsuits to recover damages have been unsuccessful as it is not possible to link earthquake damage to any one disposal well. It has been proposed that the disposal companies carry liability insurance or voluntarily set up a fund to pay for damages. Since damages are caused by the total volume of fluid, it would be reasonable to apportion the cost among the disposal companies according to the amount of fluid they inject. Those proposals have not been well received. Many people are now buying earthquake insurance for their homes when it was not needed before. The insurance has been little help. After damages, many customers found their policies have a clause that limits payments to damage only from naturally occurring earthquakes. Even policies covering induced earthquakes have been slow to pay, claiming the damage was caused by settling or poor construction. A professional engineer can determine if the damages are caused by an earthquake, and insurance companies should be required to pay up promptly when the engineer certifies that is the case.

There have been efforts to put regulations in place to limit earthquake damage. Those have met with some success, but are clearly not adequate. Current regulations by the KCC in Kansas impose volume limits on wells within 6 miles of a known earthquake epicenter. That distance is clearly not sufficient. An effort to put limits on the volume of disposal fluid in all wells in Kansas, HB 2641, failed in the legislature after intense lobbying by the oil and gas industry. The KCC and KGS need to re-examine the research and put new guidance in place to protect private property and infrastructure and guide the legislature in protecting the citizens of Kansas.

It is clear that both Kansas and Oklahoma need to put regulations in place to limit induced earthquakes and pay for damages to infrastructure and homes. Either effective agreements, or good legislation is needed to:

1) restrict the location of disposal wells.
2) limit the amount of wastewater that can be disposed of at a site.
3) limit the pressure which can be used to inject the wastewater.
4) require that any disposal well linked to significant seismic activity be further regulated.
5) require that disposal well companies form a fund or carry liability insurance to pay for earthquake damage, and pay claims promptly.

It would be best if the disposal well industry would regulate itself by agreements. They would be happier with the outcome and it would avoid the political pressure put on the state legislatures. So far, it is the Corporation Commissions who have put what regulations there are in place. Our best hope is that they will look at the most recent research and put regulations in place which take it into account.

(C) 2021 J.C. Moore All rights reserved.