Pennsylvania's Department of Environmental Protection (DEP) has told Chesapeake Energy Corp. to take precautions to prevent the migration of gas from its Marcellus Shale wells. DEP is monitoring remediation of a gas migration incident in Wilmot Township in Bradford County.

On Sept. 2 DEP received reports of bubbling water on the Susquehanna River. The agency said it and Chesapeake believe that it is gas migrating from six wells on three well pads on the Welles property, which is two to three miles northwest of the river. One week later DEP issued Chesapeake a notice of violation for failing to prevent gas migration to fresh ground water and for allowing an unpermitted natural gas discharge into state waters.

"Ventilation systems have been installed at six private water wells. Water has been provided to the three affected homes and Chesapeake is evaluating and remediating each of its well bores within a four-and-a-half-mile radius of the gas migration, which is essential," said DEP Secretary John Hanger.

DEP sampled six private water wells affected by the migration for compounds associated with gas drilling. Its analysis found methane levels in the water wells that fluctuated between non detectable and 4.4%, possibly as a result of barometric pressure in the atmosphere. No stray gas has been detected in the homes served by the water wells, According to DEP. The agency also found:

DEP and Chesapeake individually sampled isotopic readings from the gas, which could help pinpoint which well is responsible for the gas migration; DEP said test results are expected soon.

A Chesapeake spokesman was not available to comment Monday morning.

Hanger said DEP told Chesapeake to evaluate each of its 171 wells in Pennsylvania that used the same well casing procedures used in the six Wilmot Township wells -- a procedure that was used exclusively in northeast Pennsylvania. If an anomaly is found, DEP said Chesapeake must "correct it immediately" by sealing the casing with cement.

Once the remediation work is performed, it will take up to two weeks to determine if it was successful, although it may take longer for the stray gas to dissipate.

The Welles property wells were drilled between December 2009 and March 2010 but have not been fractured and are not yet producing. Because of this, DEP said it believes any stray gas migrating from the wells is coming from a formation more shallow than the Marcellus.

"This situation perfectly illustrates the problem DEP is addressing through the improved well construction standards we have finalized," said Hanger. "Chesapeake has assured me that all wells drilled by Chesapeake after July 31 conform to the regulations that the Environmental Quality Board will consider on Oct. 12."

If approved by the EQB, Pennsylvania's Independent Regulatory Review Commission is expected to vote on the regulations in November.

Earlier this year a review of DEP Marcellus Shale records by the Pennsylvania Land Trust Association found Chesapeake to have the lowest number of DEP rule violations per well drilled among companies active in the play (see Daily GPI, Aug. 4).

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