A new study suggested that the Texas 2012 earthquake was provoked by high volume injections to get oil and gas from deep underground. Geophysicists used a remote sensing technique to analyze the deformations where the quake occurred and found extracting oil and gas was the reason behind the disaster that happened four years ago.
The 2012 earthquake happened in East Texas and affected residents and damaged buildings. The new investigation confirmed what it was suspected: fracking was the cause behind the Earth movement. The earthquake had a magnitude of 4.8 and had strong aftershocks. The study was published in the journal Science and was co-authored by Stanford geophysicist William Ellsworth. The research was based on data collected by a remote sensing technique called Interferometric Synthetic Aperture Radar, or InsSAR.
The sensing technique measured ground deformations surrounding the wells near East Texas. InSAR satellites work using their radar to detect small centimeter-scale changes in the shape of Earth’s surface.
Researchers focused on four high-volume wells that began operating in 2005 and 2007 and used disposing water. The wells peak injected about 200 million gallons of wastewater, which is old water found beneath the Earth’s surface, to get oil and gas.
The four wells are located near the town of Timpson, Texas, where the earthquake occurred. When analyzing the wells, scientists discovered two of them were directly above the point where the 2012 earthquake started.
Those wells were injecting wastewater at a depth of over one mile. The two other wells also injected similar volumes of wastewater but at shallower depths. The deep-well injections sites were the ones that caused the quake.
When injecting the wastewater, the earth beneath the well had stiffer rock and a blocking formation that provoked the increasing pore pressure which later triggered the earthquake. The pressure caused by the fracking also triggered an ancient fault line.
How can fracking provoke an earthquake?
The InSAR technique found that the shallow wells also caused pressure under Earth and lifted the ground up to 5 miles, but they only provoked a modest rise in pressure and did not cause the earth movements that affected East Texas back in 2012.
The quakes caused by the two deepest wells stopped in 2013 after pressure began to decline and after wastewater injections were reduced considerably.
Wastewater is also known as brackish water and naturally coexists with oil and gas under the surface. This water is extracted using hydraulic fracturing or other techniques, Stanford News explain.
Then the water is separated from gas and oil and then reinject to extract more oil and gas. Wastewater is rich in salt and other chemicals that are not economic to treat, which is the reason it is reused to keep obtaining oil and gas.
Approximately 180 thousand similar wells are operating in the United States, primarily in Texas, California, Oklahoma, and Kansas.
Source: Standford News