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Texas Injection Well Not Likely Cause of Quaking, Investigation Finds

A proposed order from a Railroad Commission of Texas (RRC) investigation of seismic activity in the Barnett Shale region said a drilling waste injection well operated by XTO Energy Inc. is not likely to have been the cause of earthshaking that has rattled residents in the Azle, TX, area as far back as late 2013.

In June, during a show cause hearing at the RRC, representatives from XTO, a unit of ExxonMobil Corp., testified that the quake activity is naturally occurring (see Shale DailyJune 11). RRC commissioners and the commission's staff seismologist has been inclined to agree with this explanation as residents have complained for months of increased seismic activity in the area of oil/gas drilling operations (see Shale DailyJan. 21, 2014).

In June, XTO attorney Tim George testified that the company's SWD Well No. 1 injection well disposes of drilling fluids in the Ellenburger formation and serves about 230 area producing wells that are producing from the Barnett Shale. The Ellenburger formation is far below the Barnett, George said, adding that the Barnett provides "a natural geological barrier" above the Ellenburger and keeps the disposed fluids from migrating upward.

“The examiners conclude that the preponderance of the evidence supports a finding that the XTO West Lake SWD Well No. 1 was constructed and operated in accordance with its permit,” the proposed order said. “Further...the evidence does not support a finding that fluids injected into the Ellenburger formation through the...[well]...are ‘likely to be or determined to be contributing to seismic activity.’ Therefore, on this basis, the examiners recommend that XTO’s disposal permit...remain active and unchanged.”

The proposed order also said that the evidence does not support a conclusion “...that XTO’s West Lake SWD Well No. 1 is not contributing to seismic activity in the Azle-Reno area, or that the seismic activity is solely the result of natural tectonic processes.”

The RRC also is investigating a well operated by EnerVest Operating LLC and its potential relationship to seismic activity. The findings of that investigation have not yet been released.

The results of the RRC investigation of the XTO well appear to contradict those of researchers at Southern Methodist University (SMU), who said last spring that high volumes of wastewater injection combined with saltwater extraction from natural gas wells is the "most likely cause" of earthquakes occurring near Azle from late 2013 through spring 2014 (see Shale DailyApril 21).

In calling for the show cause hearing on the injection wells, RRC commissioners said they were responding to the SMU study (see Shale DailyApril 24).

The findings of the XTO well report, which were released late Monday, have not been finalized by the RRC. There is a 15-day period within which objections may be filed.

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