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Aug 14, 2009 6:03 pm US/Central
Experts, Residents Talk Salt Water Disposal Wells
DFW AIRPORT (CBS 11 / TXA 21) ―
They rumbled under North Texas and had people asking, what could be causing small earthquakes in this part of the country? Some scientists think it might be because of a byproduct of natural gas drilling.
When the first of the tremors happened, back in the fall, some people began looking toward Dallas Fort Worth International Airport. That's where a lot of natural gas drilling is taking place. There was speculation between the drilling and a fault line that's about 2,400 feet away.
"It felt like somebody ran through my apartment. So I was like 'Oh my God!' I looked outside and I didn't see anything," explained Quintus Williams who lives near DFW Airport. "And I heard later on it was an earthquake. That was my first one here."
Scientists don't think it's the drilling that could be the cause of the quakes, but now believe the cause could be connected to underwater salt water storage.
Gas companies use water to break open the shale to get to the gas. That liquid comes back up as saltwater; liquid that is three times saltier than sea water.
To keep the saltwater away from the water table, a well is dug far below the shale into a porous layer called the Ellenberger formation. That layer already has saltwater in it anyway, and there's a serious reaction if more is introduced right where two plates of earth come together.
"What happens is it tends to float the rocks apart. It lowers the pressure that's pushing the sides of the fault together, just a little bit, and that allows it to move," explained University of Texas at Arlington earth and environmental scientist Larry Standlee. "Not exactly lubricating it but I think for all purposes that's close enough to what's going on."
Chesapeake released a statement that said, in part, "Although the report is not conclusive, Chesapeake has shut in that particular well as a precautionary measure."
Scientists say there's little chance Texas will have any larger earthquakes than what we've already had. "The chances of a big earthquake happening here are very small… very, very small. I wouldn't bet on it," said Standlee.
The chances don't concern John Triplett, who lives near DFW Airport. "I don't think it's a big deal. I think if it was they would have done something about it or not done it at all."
As a precaution, Chesapeake has shutdown the salt water disposal (SWD) well at the southern end of the airport and another salt water disposal well south of Cleburne. Officials with the City of Cleburne didn't wish to discuss the preliminary earthquake findings since the research focused on seismic activity surrounding DFW Airport.
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