ConocoPhillips Alaska is continuing source remediation activities at the Alpine CD1 pad, following a March 4 natural gas release, the company said in an April 5 update, “including placing kill weight fluid and cement in multiple steps to isolate the natural gas release from the C10 Halo interval.”
In an April 6 situation report the Alaska Oil and Gas Conservation Commission said source remediation operations began March 30 and described the current work as “milling casing to set an open hole cement plug to isolate the C-10 (Halo) formation.”
The work is being done on the WD-03 disposal well, which was being drilled when the release occurred. ConocoPhillips said the C-10 Halo zone of the WD-03 well was not cemented because the interval had not been interpreted “as a significant hydrocarbon zone.”
ConocoPhillips identified the release as predominately methane in a March 24 update, and said it is “believed to be from the C-10 Halo formation, with lesser amounts from the Qannik formation,” and on March 27 the company identified C-10 Halo as the sole source of the gas, citing well logging results.
AOGCC said April 6 that all wells on the CD1 drill site remain shut-in except for waste injection in CD1-01A and produced water injection in CD1-03 and CD1-05 and said ConocoPhillips continues to monitor the CD1 well row for gas releases and well pressures.
ConocoPhillips said no gas has been detected outside of the wellhouses.
“Remediation activities will be ongoing, leading up to the final plug and abandonment of the WD-03 well,” the company said.
March 4 release
The gas release was first observed March 4 from the ground at the wellhouse of well CD1-05, AOGCC said, and natural gas releases occurred at seven wells on the CD1 drill site and through cracks on the pad near Doyon Rig 142.
“The volume of natural gas released into subsurface strata under CD1 that was not captured into CPAI’s Alpine Central Facility … is estimated at 7.2 million standard cubic feet,” ConocoPhillips told the commission in an April 1 letter. The company said most of that volume “is believed to have escaped to the atmosphere between March 4, 2022, when gas was first detected at CD1, and March 8, 2022, when gas flow was routed through the WD-03 outer annulus into the” Alpine Central Facility. “Some small amount of gas that was released to the subsurface strata may continue to escape to the atmosphere over time,” the company said.
March 9-10, the commission said, there was also a release of some 590 gallons of saline water.
Seismic
ConocoPhillips requested a permit for 3D seismic at the Colville River unit March 21, saying the objective “is to acquire high quality 3D seismic data to evaluate the shallow subsurface characteristics in the CD1 pad area.”
The company said that while it wants to acquire the seismic data in the current ice season because of recent events at CD1, the data will not be useful in response to the gas release because of data processing timelines.
SAExploration will be shooting the seismic for ConocoPhillips.
In its April 5 update, the company said: “To understand the geology in the area below the CD1 pad, shallow 3D seismic operations are underway.”
Monitoring continues
AOGCC said ConocoPhillips continues to monitor the CD1 well row for gas releases and well pressures and continues to perform air monitoring.
The company said April 5 that its communications with regulators are ongoing, with the most recent update April 4 and the next meeting planned for April 11.
- KRISTEN NELSON
