Nav: Home

Location of wastewater disposal drives induced seismicity at US oil sites

October 31, 2018

The depth of the rock layer that serves as the disposal site for wastewater produced during unconventional oil extraction plays a significant role in whether that disposal triggers earthquakes in the U.S., according to a new study that takes a broad look at the issue.

The research published in Seismological Research Letters reviewed data on wastewater disposal for oil sites in Oklahoma, eastern Montana, western North Dakota, Texas and New Mexico.

Seismicity levels are higher in Oklahoma compared to the other states in part because wastewater is injected deeper into the ground in Oklahoma, nearer to the underlying basement rock, according to study author Bridget Scanlon of the University of Texas at Austin and her colleagues.

The cumulative volume of wastewater injected into the earth in Oklahoma is also higher than in the other oil-producing areas, and can also be linked to increased rates of seismicity in the state, the researchers concluded.

The findings differ from an earlier study based on data in the mid-continent, which did not find a significant correlation between total disposed wastewater volume, or between depth of injection, and increased seismicity. The new study contains an additional 3.5 years' worth of data on injection volume and seismicity in Oklahoma, however, and also uses a new map of basement rock depth, said Scanlon.

Unconventional U.S. oil production, which extracts oil from shales and tight rocks using hydraulic fracturing and horizontal wells, has been linked to an increase in human-induced earthquakes across the mid-continent of the United States for nearly a decade. The main driver of this increase in seismicity is the injection of wastewater produced by extraction, which increases pore pressure within rocks and can affect stress along faults in the rock layers selected for disposal.

The "tightness" of the oil-producing rock layers at these sites means that wastewater can't be injected back into the same layers, so companies have instead found "looser," more permeable rock layers in which to drill disposal wells.

The study by Scanlon and colleagues examined wastewater injection rates, cumulative regional injection volumes and injection proximity to basement rock for tight oil plays in Oklahoma, the Bakken play (Montana and North Dakota), the Eagle Ford play (Texas) and the Permian play (Texas and New Mexico).

Many of the wastewater disposal wells in Oklahoma are drilled into a rock layer called the Arbuckle Formation, which lies adjacent to the basement and is much deeper than the rock layers used for disposal in the Bakken, Eagle Ford and Permian plays.

Wells drilled into the Arbuckle drain water into the formation without the need for pressure at the wellhead, and the rock zone is highly permeable, which makes it an appealing disposal site, said Kyle Murray, a co-author on the study from the Oklahoma Geological Survey. The Arbuckle also has extraction wells only "in a few small areas, so disposal does not diminish producing wells."

The ease of using the Arbuckle as a disposal site might be one reason why oil producers have chosen deeper disposal sites in Oklahoma compared to the other regions, "but drilling shallower wells and disposing in shallower zones in other plays may be related to economics. Deeper wells are much more expensive and not always successful," he added.

Murray said oil field operators in these other regions may also know about the studies linking the increase in seismicity in Oklahoma to injection proximity to basement rock, causing them to avoid deep disposal at their sites.

The researchers noted that their findings are consistent with the reduced seismicity documented in Oklahoma after directives by the Oklahoma Corporation Commission in 2014 and 2016 to reduce injection rates and regional injection volumes, as well as to plug disposal wells drilled into the basement. These directives have led to a 70 percent reduction in the number of magnitude 3.0 or larger earthquakes in the state in 2017, relative to 2015.

There are tradeoffs between injecting wastewater into shallow versus deep rock layers, the researchers note. Shallower wells, which often cost two to three times less than deeper wells and would appear to trigger lower levels of seismicity, could contaminate aquifers with saltwater or interfere with oil production wells.

Scanlon and colleagues say one way to reduce the amount of overall wastewater injection might be to repurpose the wastewater for hydraulic fracturing. "The value of reusing produced water for hydraulic fracturing is similar to re-injecting produced water for water flooding in conventional oil reservoirs, to maintain pressure," Scanlon said. "Reusing produced water for hydraulic fracturing would reduce water sourcing issues and water depletion related to that, and would also reduce wastewater disposal and related potential seismicity."

This strategy might work best in places where the wastewater produced is roughly similar to the amounts needed for hydraulic fracturing, however. In Oklahoma, for instance, hydraulic fracturing operations would use up only 10 percent of the amount of produced wastewater.
-end-


Seismological Society of America

Related Wastewater Articles:

Wastewater test could provide early warning of COVID-19
Researchers at Cranfield University are working on a new test to detect SARS-CoV-2 in the wastewater of communities infected with the virus.
HKU team develops new wastewater treatment process
A University of Hong Kong research team has developed a novel wastewater treatment system that can effectively remove conventional pollutants, and recover valuable resources such as phosphorus and organic materials.
Treating wastewater with ozone could convert pharmaceuticals into toxic compounds
With water scarcity intensifying, wastewater treatment and reuse are gaining popularity.
Polluted wastewater in the forecast? Try a solar umbrella
Evaporation ponds, commonly used in many industries to manage wastewater, can occupy a large footprint and often pose risks to birds and other wildlife, yet they're an economical way to deal with contaminated water.
Wastewater leak in West Texas revealed
Geophysicists at SMU say that evidence of leak occurring in a West Texas wastewater disposal well between 2007 and 2011 should raise concerns about the current potential for contaminated groundwater and damage to surrounding infrastructure.
Mapping international drug use by looking at wastewater
Wastewater-based epidemiology is a rapidly developing scientific discipline with the potential for monitoring close to real-time, population-level trends in illicit drug use.
Mapping international drug use through the world's largest wastewater study
A seven-year project monitoring illicit drug use in 37 countries via wastewater samples shows that cocaine use was skyrocketing in Europe in 2017 and Australia had a serious problem with methamphetamine.
Plant research could benefit wastewater treatment, biofuels and antibiotics
Chinese and Rutgers scientists have discovered how aquatic plants cope with water pollution, a major ecological question that could help boost their use in wastewater treatment, biofuels, antibiotics and other applications.
Predicting earthquake hazards from wastewater injection
ASU-led geoscientists develop a method to forecast seismic hazards caused by the disposal of wastewater after oil and gas production.
Stronger earthquakes can be induced by wastewater injected deep underground
Earthquakes are getting deeper at the same rate as the wastewater sinks.
More Wastewater News and Wastewater Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Teaching For Better Humans 2.0
More than test scores or good grades–what do kids need for the future? This hour, TED speakers explore how to help children grow into better humans, both during and after this time of crisis. Guests include educators Richard Culatta and Liz Kleinrock, psychologist Thomas Curran, and writer Jacqueline Woodson.
Now Playing: Science for the People

#556 The Power of Friendship
It's 2020 and times are tough. Maybe some of us are learning about social distancing the hard way. Maybe we just are all a little anxious. No matter what, we could probably use a friend. But what is a friend, exactly? And why do we need them so much? This week host Bethany Brookshire speaks with Lydia Denworth, author of the new book "Friendship: The Evolution, Biology, and Extraordinary Power of Life's Fundamental Bond". This episode is hosted by Bethany Brookshire, science writer from Science News.
Now Playing: Radiolab

Space
One of the most consistent questions we get at the show is from parents who want to know which episodes are kid-friendly and which aren't. So today, we're releasing a separate feed, Radiolab for Kids. To kick it off, we're rerunning an all-time favorite episode: Space. In the 60's, space exploration was an American obsession. This hour, we chart the path from romance to increasing cynicism. We begin with Ann Druyan, widow of Carl Sagan, with a story about the Voyager expedition, true love, and a golden record that travels through space. And astrophysicist Neil de Grasse Tyson explains the Coepernican Principle, and just how insignificant we are. Support Radiolab today at Radiolab.org/donate.