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Fracking and Earthquakes, what is our experience?

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There has been a good deal of concern regarding the effects of hydraulic fracturing, “fracking” and oil industry pumping into injection wells to dispose of fluids associated with industry operations. With this in mind we did some research to see what effects are being reported in the Four Corners area of New Mexico and Arizona and more broadly to see what other researchers are reporting.

THE FRACKING PROCESS

Hydraulic fracturing or “fracking” has been used in oil and gas wells for many decades.  It involves injecting chemical laden water at high pressure into geologic formations to extract oil and gas.  The pressure injects water containing chemicals and sand. When the pressure is removed the sand particles remain in the small fractures keeping them open and allowing the flow of oil and/or gas.

What is a recent development in the area of fracking is the technique of horizontal drilling. There are many relatively thin layers of petroleum bearing rock formations that are now economically available for drilling due to the ability to drill the well horizontally along these formations. This true revolution has made it possible for the U. S. to be the only country in the world to reduce carbon dioxide emissions by 7%. It has also made us energy independent and has substantially lowered the cost of gas worldwide.  However the whole process is not without some negative consequences.

The fracking process itself involves high pressure injection of fluids and sand. The process is distributed over a large area and only very seldom causes small earthquakes.  Small is in the sense that we don’t feel them or hardly feel them at the ground surface.  This is because the fracking pressure is distributed over a long distance.

But the process sometimes uses millions of gallons of water which must be disposed of later.  This water and water pumped as part of other oil and gas well operations is usually pumped deep underground into injection wells.

INJECTION WELL OPERATIONS

The source of the water is basically from two sources.  First many existing oil and gas wells produce water in addition to the desired oil and gas.  In the past this water was usually placed in evaporation ponds for disposal.  But much of this oily water is collected and taken to an injection well for disposal.

State agencies when approving these injection wells require that the waste water is pumped in a formation deep underground, way below formations that contain good quality water to prevent contamination and in locations far from population centers. In some areas there are few problems associated with this process as in northwest New Mexico [see below].  In other areas, notably in Oklahoma, geologic activity and conditions are such that the injected fluids cause man-made earthquakes.

MAN-MADE EARTHQUAKES FROM FRACKING, INJECTIONS

Man-made earthquakes of this type are triggered when a large amount of waste water is injected in one place which is exactly what injection wells do.  In Oklahoma’s case, they have an enormous number of wells, some 4,600 injection wells and geologic conditions that can encourage earthquakes.  The largest earthquake ever recorded in Oklahoma had a Magnitude of 5.6 and is believed to have been caused by an injection well. For additional information about man-made earthquake in Oklahoma, Google “Artificial Quakes Shake Oklahoma, Witze”.  The author, Alexandra Witze received the 2016 David Perlman Award for Excellence in Science Journalism from the American Geophysical Union for this well written article.

The State of Oklahoma has now established a 10 kilometer [3 mile] buffer zone around injection wells.  The hydraulic fracturing process, by contrast, is rarely associated with an earthquake and never has been tied to an earthquake greater than Magnitude 4. Magnitude numbers are not linear. In fact a Magnitude 5.6 earthquake which can cause damage to structures is 250 times stronger than a Magnitude 4.0 earthquake, which probably won’t be felt more than a few miles from the epicenter location of the earthquake.

MANMADE EARTHQUAKES IN GENERAL

In a recent study, geologists from Durham University in the United Kingdom compiled what is considered the most complete database to date of man-made earthquakes. The scientists spent a year looking through records stretching back to the 19th century.  Their database lists 715 earthquake sequences, each consisting of as many as several hundred earthquakes. Their conclusion was that man-made earthquakes are grossly under-reported [http://bit.ly/triggered-quakes-abstract].  This report was presented at the American Geophysical Meeting in San Francisco in December 2016 and recently reviewed in the Journal EOS in February 2017.

Their study catalogs man-made earthquakes from four general sources

1.      Surface operations, like quarrying, building structures and dams,

2.      Injecting substances into the earth’s surface, such as wastewater disposal,

3.      Removing material from the subsurface including mining operations and     pumping water for irrigation, and

4.      Explosions from underground nuclear tests.

They found the most common cause of man-made earthquakes accounting for one-third of all man-made earthquakes cataloged were caused by mining processes, mostly small ones.  But occasionally there can be catastrophic consequence.  In 2011 the small town of Lorca in Spain was completely destroyed killing 10 people following a 5.1 magnitude earthquake.  According to the report, this earthquake was caused by decades of ground water being removed for irrigation.

They found that more than 100 mines in China reported seismic events larger than magnitude 4 and in Germany an earthquake of magnitude 5 occurred after a 2 square mile area over a potash mine collapsed killing three people.  They report that most earthquakes triggered by mining processes are very small, ranging in magnitude between 2 and 4.

Another source of earthquakes is groundwater removal. They report that in 2011 a magnitude 5.1 earthquake destroyed a town in Spain killing 10 people.  The event was tied to decades-long removal of water for irrigation.

The next most common cause of man-made earthquakes in their study, about 20%, was caused by dams which can force water into fault zones.  The largest dam-associated earthquake they listed was a magnitude 5.7 event at the Aswan High Dam in Egypt.

Another example they report is the Koyna Dam in India which impounds about 2.4 million acre-feet of water apparently causing a magnitude 5 earthquake every five years.

FOUR CORNERS AREA EARTHQUAKES

But dams certainly don’t necessarily cause earthquakes. Navajo Dam in northwest New Mexico is the third largest earth filled dam in the U.S.  A check with the National Earthquake Information Center’s records [https://earthquake.usgs.gov/earthquakes/search/] indicate that there has never been a measured earthquake near the dam since its construction in 1962.

San Juan County, New Mexico contains one of the largest gas producing areas in the nation with thousands of wells and an area where there has been active hydraulic fracturing of wells for decades. A search of the State’s Oil and Gas website [https://wwwapps.emnrd.state.nm.us/ocd/ocdpermitting//Data/Wells.aspx] shows there are at least 40 active injection wells in San Juan County. A search of the National Earthquake Information Center’s records for San Juan County for earthquakes larger than Magnitude 0.5 for the last ten years shows only one earthquake.  This is identified as a mining explosion and is located near the Burnham Mine south of Fruitland, NM.

Looking at the Navajo Reservation in Arizona, the Earthquake Information Center shows 9 earthquakes in the last ten years. One event, Magnitude 2.8, is identified as a mining explosion and is located at the site of the Black Mesa Coal Mine southwest of Kayenta, AZ. Six other small earthquakes ranging in size from Magnitude 1.6 to 2.8 are located south of Page Arizona ranging in depth from the ground surface to as deep as 24 km were found.  These are likely from natural causes. There was one earthquake located about 10 km south of Tuba City Arizona at a depth of 5 km, and finally one about 6 km northwest of Cameron Arizona also 5 km deep.  So for this portion of the Navajo Indian Reservation we find one small man-made earthquake from mining operations.

What we can see from this is that man has been causing small earthquakes for a long time and these usually cause little or no problem.  On the other hand some caution is advised.  Oklahoma has done this with a 10 kilometer [3 mile] buffer zone.

A check of the data from the Earthquake Information Center in Golden Colorado shows that there have been no earthquakes associated with fracking or injection wells in San Juan County NM or in NE Arizona on the Navajo Indian Reservation for the last 10 years.

By Michael Daly

For the Sun