A study released today by university scientists in Dallas and Austin bolsters suspicions that a saltwater disposal well associated with Barnett Shale natural gas operations was responsible for several small earthquakes in North Texas.

The largest of the quakes measured 3.3 on the Richter scale, and no major injuries or damage were reported.

Geologists from the University of Texas at Austin and Southern Methodist University found no evidence linking earthquakes recorded in 2008 and 2009 to the drilling of more than 13,000 gas production wells in North Texas.

They also found no connection between the quakes and hydrological fracturing, the injection of water underground to force out trapped gas.

They found that a different kind of well used to dispose of saltwater brought to the surface during gas operations might be to blame. They compared the timing, location and depth of earthquakes to the operation of a disposal well at the north end of Dallas/Fort Worth International Airport and discovered an apparent link.

No earthquakes occurred before the D/FW well began operating in September 2008 or after it was closed last year, scientists said. Chesapeake Energy Co. shut down the D/FW well and a similar one near Cleburne in August after researchers told them of the apparent connection.

There was a swarm of minor quakes last year in Cleburne, about 50 miles southwest of Dallas.

Gas companies or disposal firms have drilled about 200 saltwater disposal wells in the Barnett Shale region, but only the D/FW and Cleburne wells had obvious links to earthquakes, the geologists said. They called that puzzling and said more research was needed, noting that they did not have detailed geological information that would let them assess other disposal well locations.