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Friday, 27 October 2017 01:00

New study links Raton Basin earthquakes to oil and gas wastewater injections

New study links Raton Basin earthquakes to oil and gas wastewater injections Credits: www.pennenergy.com

A series of earthquakes between 2008 and 2010 in the Raton Basin - along the southern Colorado and northern New Mexico border – was likely due to fluids pumped underground during oil and gas wastewater disposal, according to a new study by the University of Colorado Boulder.

The study took place in the 2,200-square-mile Raton Basin and associated more than 1,800 earthquakes up to magnitude 4.3 from 2008 to 2010 to wastewater injection wells, i.e. wells that are used to dispose waste fluids associated with oil and natural gas production. A key element of the new study was the use of hydrogeological modeling of pore pressures in the "basement rock" of Raton Basin, i.e. the several miles deep rock that underlies the oldest stratified layers.

"Basement rock is typically more brittle and fractured than the rock layers above it," said Sheehan, a fellow at University of Colorado Boulder (CU Boulder) Cooperative Institute for Research in Environmental Sciences. "When pore pressure increases in basement rock, it can cause earthquakes."

Although previous studies have linked earthquakes in the Raton Basin to wastewater injection wells, this is the first to show that elevated pore pressures deep underground are well above earthquake-triggering thresholds, according to CU Boulder doctoral student Jenny Nakai, lead author of the study. "We have shown for the first time a plausible causative mechanism for these earthquakes," said Nakai. "The spatial patterns of seismicity we observed are reflected in the distribution of wastewater injection and our modeled pore pressure change."

As part of the research, the team also made a 3D simulation of a 12-mile-long fault, using seismicity data from the Vermejo Park region in the Raton Basin. The seismicity patterns also suggest a second, smaller fault in the Raton Basin that was active from 2008 to 2010.

The study also showed the number of earthquakes in the Raton Basin that correlate with the cumulative volume of wastewater injected in wells up to about 9 miles away from the individual earthquakes.

The earthquake patterns in the Raton Basin are similar to other U.S. regions that have shown "induced seismicity" likely caused by wastewater injection wells, according to Nakai. Previous studies have shown that injection wells likely caused earthquakes near Greeley, Colorado, in Oklahoma and in the mid-continent region of the United States in recent years.

Source: www.colorado.edu

Read 803 times Last modified on Friday, 27 October 2017 14:29

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