sexta-feira, 14 de agosto de 2009

Wastewater Disposal Well May Have Caused Texas Earthquakes

The Wall Street Journal

A series of minor earthquakes in North Texas may have been caused by a wastewater disposal well connected to natural-gas production in the area, Chesapeake Energy Corp. told state regulators Thursday.

Chesapeake said it had shut down two disposal wells "as a precautionary measure."
The Dallas-Fort Worth area has experienced more than a dozen small quakes since last October, though there have been no reports of significant damage or injury. The area lies at the heart of the Barnett Shale, a huge natural-gas field where thousands of wells have been drilled in recent years. Many locals suspect a connection, especially because gas production in the area involves injecting water into the ground at high pressure to crack open the gas-bearing rock, a process known as "hydraulic fracturing."

Researchers from Southern Methodist University in Dallas have deployed seismic sensors in the area to study the phenomenon. On Thursday, the researchers said preliminary results suggest the quakes do not appear to be connected to drilling or fracturing itself.

But they said their research does show a "possible correlation" between the quakes and a salt water disposal well operated by Chesapeake on the southern end of Dallas-Fort Worth International Airport. The airport sits atop a fault line.

Along with hydrocarbons, oil and gas wells almost always produce salt water, which is often disposed of in depleted oil fields or other underground formations. Studies have linked disposal wells to seismic activity in the past.

In an email to the Texas Railroad Commission, which regulates the state oil and gas industry, Chesapeake said it had shut down the airport disposal facility and another well in the town of Cleburne, which has also experienced quakes.

Company spokeswoman Julie Wilson called the move "a precautionary, proactive step."
"The events in that area have been very minor and most have not even been felt or were barely felt," Ms. Wilson said.

Write to Ben Casselman at

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