New Maps Show Seven Million Americans at Risk from Industry-Made QuakesUS science agency highlights 'potential ground-shaking hazards.'
By Andrew Nikiforuk, 1 Apr 2016, TheTyee.ca
For the first time in its history, the United States government's premier science agency has issued maps identifying "potential ground-shaking hazards" from industry-induced earthquakes caused either by high-volume fracking or the injection of wastewater into the ground.
The new United States Geological Survey's risk assessment shows that approximately seven million people now live and work in regions that could be affected by earthquakes triggered by the oil and gas industry in the central U.S.
The USGS had previously published maps showing hazards only from natural earthquake activity.
However, a dramatic increase in earthquake swarms since the advent of high-volume hydraulic fracturing led the science agency to change its earthquake hazard assessments.
Scientists have known for decades that the injection of wastewater or the injection of millions of gallons of fracking fluid (including water, chemicals and sand) to blast apart rock can destabilize underground formations by over-pressurizing natural faults and fractures.
The residents of six states face the most significant potential shaking hazards, including Oklahoma, Kansas, Texas, Colorado, New Mexico and Arkansas, according to the USGS.
"In the past five years, the USGS has documented high shaking and damage in areas of these six states, mostly from induced earthquakes," reported Mark Petersen, a spokesman for the USGS.
"Furthermore, the USGS 'Did You Feel It?' website has archived tens of thousands of reports from the public who experienced shaking in those states, including about 1,500 reports of strong shaking or damage."Once seismically quiet
Before the shale gas revolution, an average of 24 earthquakes of magnitude 3.0 and larger per year shook the U.S. Midwest between 1973 and 2008.
But the shale gas industry and high-volume hydraulic fracturing changed the seismically quiet area into one of the most active regions in the country, as the rate of shaking steadily increased from 2009 to 2015. Tremors of magnitude 3.0 averaged 318 per year and peaked in 2015 with 1,010 earthquakes.
Approximately 226 earthquakes of magnitude 3.0 and larger have shaken the central U.S. region in the last three months. To date, the largest earthquake located near several active injection wells was a magnitude 5.6 in 2011 near Prague, Oklahoma.
To reduce the industry-made earthquakes, Oklahoma state regulators plan to reduce the amount of toxic wastewaters injected miles into the ground by more than half a billion barrels a day over a 5,000-square-mile area.
In an earlier report, the USGS explained that "the most probable risks in areas of increased seismicity include life-threatening injuries caused by falling objects and economic loss from damage to structures with low capacity to absorb moderate earthquake shaking... there is no question that increased hazard accompanies higher levels of earthquake activity."
Seismic activity, whether natural or industry-made, poses two key problems for the oil and gas industry. Gas Migration, a well-known industry textbook, notes that industry-triggered earthquakes can form vertical and subvertical faults and fractures above petroleum reservoirs.
Seismic vibrations can also increase the permeability of the rock and increase upward gas migration into the atmosphere. Gas leakage can pose serious environmental risks.
Current research suggests that induced earthquakes can trigger larger earthquakes on known or unknown faults than natural earthquakes. Throughout oil and gas drilling regions, scientists suspect there may be thousands of faults that could rupture in a large earthquake as a result of fluid injection from industry.
According to the USGS, induced earthquakes also tend to exhibit swarm-like behaviour with more numerous and smaller earthquakes at shallower depths.Canadian induced-quakes mainly caused by fracking
In contrast to U.S. studies, Canadian experts largely attribute dramatic increases and changes in seismic patterns in western Canada to increases in hydraulic fracturing as opposed to wastewater well injection.
To date, the fracking industry has caused more than 1,000 minor and felt earthquakes in southern Alberta and northern British Columbia. Steam injection for bitumen appears to have caused earthquakes near Peace River, too.
A new Canadian study has confirmed that most earthquakes triggered by the oil and gas industry Alberta and B.C. have been caused by the unpredictable technology of hydraulic fracturing.
Some of the world's largest injections of frack fluids to crack open underground rock have taken place in Canada.
In particular, the scientists identified 39 fractured wells that triggered earthquakes greater than magnitude 3.0 with a maximum magnitude to date of 4.6. They also identified 17 disposal wells responsible for earthquakes as great as magnitude 4.5.
"The nature of the hazard from hydraulic fracturing has received less attention than that from wastewater disposal, but it is clearly of both regional and global importance," the Canadian scientists concluded.
The study added that "It is possible that a higher-than-recognized fraction of induced earthquakes in the United States are linked to hydraulic fracturing, but their identification may be masked by more abundant wastewater-induced events."
Although industry and regulators have denied or played down the connection between earthquakes and injecting frack fluids or wastewater into the ground near faults, scientists identified the risk nearly three decades ago.
A 1990 report by the USGS reported that hydraulic fracking in Oklahoma had set off multiple earthquake swarms as early as 1978. "The process once started, may not be controlled completely or readily," concluded the researchers.
Due to limited monitoring, industry and government lack a full understanding of how industry-triggered quakes are changing groundwater flow in the region or altering the migration of gases such as methane, radon and carbon dioxide into the atmosphere throughout northeast B.C and central Alberta.
High rates of methane have now been detected above fracked landscapes in Oklahoma, New Mexico and Australia. Fractures can form in rock as a direct consequence of drilling, acidizing, cementing and fracking activities. These fractures can then serve as potential pathways for methane and other gases.
Earthquakes triggered by the shale gas industry in B.C. have not injured anybody or damaged public property to date. But industry-made tremors in the U.S. Midwest have caused millions of dollars of damage in Oklahoma and created new insurance liabilities.