Man-made earthquakesWhy is oil and gas activity causing earthquakes? And can we reduce the risk?
If you’ve been following the news lately, chances are you’ve heard about — or even felt — earthquakes in the central United States. During the past five years, there has been an unprecedented increase in earthquakes in the North American mid-continent, a region previously considered one of the most stable on Earth. Oklahoma has gone from experiencing fewer than two magnitude-three earthquakes per year to greater than two per day, the report found. Similarly, Texas has experienced a near 10-fold increase in magnitude-three earthquakes or greater in the past five years. Many studies indicate that human activities, including activities related to oil and gas extraction, are beginning to play a significant role in triggering earthquakes in the central United States. History dictates that the advent of new technology often leads to new and unforeseen challenges. The printing press, the automobile, and splitting the atom have provided incalculable benefits to humanity but also incredible responsibility. What is recognized as the Texas-led “Shale Revolution,” arguably one of the most significant innovations of the modern era, is no different.
If you’ve been following the news lately, chances are you’ve heard about — or even felt — earthquakes in the central United States. During the past five years, there has been an unprecedented increase in earthquakes in the North American mid-continent, a region previously considered one of the most stable on Earth.
According to a recent report by the Oklahoma Geological Survey, Oklahoma alone has seen seismicity rates increase 600 times compared to historic levels.
The state has gone from experiencing fewer than two magnitude-three earthquakes per year to greater than two per day, the report found. Similarly, my home state of Texas has experienced a near 10-fold increase in magnitude-three earthquakes or greater in the past five years.
The recent uptick in earthquakes in Texas, Oklahoma and several other central U.S. states raises an obvious question: What is causing all of this seismicity?
Earthquake causes
Several factors can promote the occurrence of earthquakes. There are natural changes caused by the shifting of Earth’s plates, the advance and retreat of glaciers, the addition or removal of surface water or ground water, and the injection or removal of fluids due to industrial activity.
Studies including two reports issued in April, indicate that human activities, including activities related to oil and gas extraction, are beginning to play a significant role in triggering earthquakes in the central United States.
Extracting oil and gas from shale rock involves cracking, or fracturing, a layer of underground rock with a high-pressure mix of water, sand, and chemicals. As the oil and gas are released, those injection fluids and briny water also come up. That wastewater is later disposed of in what are called injection wells, or sometimes disposal wells.
It is important to note that it is not the fracking process itself that usually causes these earthquakes; it is the rapid injection of fluid during wastewater disposal that sometimes pumps hundreds of millions of gallons of brine deep into the earth each year.
Hundreds of studies
So do injection wells cause earthquakes?
A recent peer-reviewed scientific study I co-authored concludes human-activities, specifically water production and wastewater injection, represent the most likely cause of earthquakes in the Azle/Reno, Texas region, where significant gas production and wastewater injection began five years ago.
But this is not a fundamentally new discovery. For nearly a century, industry and academic researchers have recognized that human activities can and do sometimes trigger earthquakes.
