Since 2009, there has been a dramatic increase in earthquakes in the central and eastern United States. In Oklahoma, these earthquakes are prominent in the central and northern parts of the state.
More than 200 magnitude 3.0 or greater earthquakes have shaken Oklahoma since 2009. According to United States Geological Survey, one to three 3.0 magnitude or greater earthquakes occurred yearly from 1975 to 2008. This rose significantly to an average of 40 earthquakes per year from 2009 to mid-2013.
This increase included the largest earthquake recorded in Oklahoma, which was a 5.6 magnitude that occurred near Prague Nov. 5, 2011. It has been interpreted that this activity is related to the process of fracking and wastewater injection.
Fracking is shorthand for hydraulic fracturing, which involves the process of drilling a mile or more into shale formations before gradually turning horizontal and continuing its path. This creates a well that, after it is safely drilled, cased and cemented, has small holes in the horizontal pipe through which a mixture of water and sand is pumped at a high pressure that creates small fractures in the rock that are held open by sand.
Fracking has provided access to an alternate source of fuel. Until renewable energy is better developed and accessible for everyone, this alternate source of fuel will buy some time.
However, fracking also uses larges amount of water. According to Chesapeake Energy, the initial drilling operation could use 6,000 to 60,000 gallons of fracking mixture.
“The oil and gas companies will tell you that there is little to no risk of contamination to drinking water because they securely seal the aquifers. That said, however, there are chances for things to not go as planned and a potential of contamination of drinking water,” said Environmental Science Professor Daniel Ratcliff.
Despite all this, fracking is not considered the cause of this increase in earthquakes.
According to the USGS, fracking is only directly involved in a small percentage of seismic activity.
“It is not each individual frack well per se, because each individual frack well is put under pressure for short durations and not as high of a pressure. It’s the disposal of those millions and billions of gallons of frack fluid and production fluid from all of the wells,” said Ratcliff.
These wells that hold all this fluid are also known as class II underground injection wells. They take any fluid related to oil and gas drilling, including frack wastewater. The oil and gas industry uses injection wells to dispose of the highly salty water from the ancient seas that have preceded in the Oklahoma area, chemicals, heavy metals, and radioactive material.
“Things get pumped down more into those regularly. And so there you have a consistent process going on rather than a very short term,” said Geology Professor Eric Johnson.
Fracking has been a technique to extract resources since the 1940s. However, new techniques such as horizontal drilling, which was developed in the 1990s, has led to more fluid needing to be disposed of. The larger amounts of fluid in recent years are the likely cause of the increase in earthquakes.
“It decreased the amount of fracking fluid they have in their production water, so they have a higher volume of disposal fluid they have to take care,” said Ratcliff.
Johnson also mentioned that it’s possible there are faults deeper below than what was previously recorded. If they exist, it is possible that the wells are interacting with these deep faults.
There’s no definitive answer currently for what is causing the earthquakes. In order to access this source of fuel, it is beneficial for oil and gas companies to continue these fracking procedures.