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In early 2019, CNX’s Shaw 1G well suffered a complication that ultimately ended its operation. Last week, the state Department of Environmental Protection and CNX came to an agreement about penalties, and practices moving forward.
The Shaw 1G well is an unconventional natural gas drilling site in Washington Township, Westmoreland County, Pennsylvania. The well pad is home to both conventional (vertical) and unconventional (horizontal) wells, and sits on the bank of the Beaver Run Reservoir.
According to the DEP, operators at the Shaw 1G site observed significant pressure losses in their unconventional well, which then caused gas to migrate uncontrollably from the Shaw 1G site to other formations, causing pressure to rise at other well sites; this is also known as subsurface communication. As a result, CNX flared gas at nine other wells in the immediate area to relieve pressure, as well as ‘killing’ the well by filling the bore with mud, rendering it useless. After investigations by both the DEP and CNX, it was determined that a casing failure in the uncongenial well caused the issue.
In oil and gas extraction, casings are installed in the wellbore to protect subsurface structures and resources from being harmed during the extraction process. Given that oil and gas extraction uses very high pressures to move the resources, well casings must be incredibly strong, but also malleable enough to withstand pressure changes without cracking. A metric used to rate casings is its tensile strength, or its ability to withstand tension without breaking.
According to CNX, the failure was caused by wellbore casing with a high tensile strength that cracked from hydrogen stress. Somewhat counter-intuitively, casings with a lower tensile strength can withstand hydrogen stressors more effectively than its higher tensile-rated counterparts. The failure caused what’s known as a ‘blowout’, which is essentially the uncontrolled release of gas or oil from the well, which can be disastrous.
The DEP’s investigation came to the same conclusion as CNX’s independent investigation, and as a result, found CNX to be responsible for the failure. CNX was fined $175,000 which will go into the state’s Oil and Gas Fund. Additionally, CNX will have to take extra measures to ensure that the integrity of other wells on the Shaw well pad, as well as the Shaw 1G well itself, “report flow increases greater than 5,000 cubic feet per day, and submit a corrective action plan to DEP in the event of flow increases”.