North Slope earthquake appears to have had no oil facility impact
A magnitude 6.4 earthquake with an epicenter 52 miles southwest of the village of Kaktovik on the North Slope appears to have left oil industry facilities undamaged, although it did trigger a flurry of facility inspections. According to the University of Alaska Fairbanks Alaska Earthquake Center, the earthquake, which happened at 6:58 a.m. on Aug. 12, was by far the largest ever recorded north of the Brooks Range. A sequence of aftershocks included a magnitude 6.0 earthquake at 1:15 p.m. Even that aftershock was more powerful than any previous earthquake recorded in the region.
The epicenter was located in the Sadlerochit Mountains, about 25 miles south of the Beaufort Sea coast.
Point ThomsonExxonMobil’s Point Thomson gas-condensate field lies on the coast to the northwest of the epicenter - condensate is shipped by pipeline from Point Thomson to the central North Slope.
“We confirm that all Point Thomson staff are safe and site assessments found no damage or impact to facilities,” John Moore, senior advisor for public and government affairs for ExxonMobil Alaska, told Petroleum News in an Aug. 14 email. “Similarly, the Point Thomson Export Pipeline (PTEP) team conducted assessments and surveyed the pipeline and found no damage or impact.”
Moore also commented that ExxonMobil had been in contact with neighboring communities and oil industry sites in Kaktovik, Kavik Camp and Badami to confirm everyone was safe.
“The safety of our personnel, nearby communities and the environment continues to be our top priority,” Moore said.
BP also confirmed that it had not found any damage to the facilities and pipelines in the Prudhoe Bay field in the central North Slope. BP spokeswoman Megan Baldino told Petroleum News that there had been no impacts on BP facilities or operations on the North Slope, but that the company has continued to monitor the situation.
Trans-Alaska pipelineOf particular concern is the trans-Alaska oil pipeline, the artery that delivers North Slope crude oil south to market.
Alyeska Pipeline Service Co. spokeswoman Kate Dugan has told Petroleum News that on Aug. 12 Alyeska, the TAPS operator, completed an aerial survey and a cursory on-the-ground inspection of the pipeline and its related facilities between pump stations 1 and 4. Pump station 1 is at the northern end of the pipeline, while pump station 4 is on the northern side of the Brooks Range.
“Ground crews were out there, just checking things over for movement, settlement … and didn’t see any problems,” Dugan said.
Alyeska was also bringing in a seismic specialist to conduct a second inspection of the same section of the line. There will then be a further round of inspections in a week or two, to determine if any issues have arisen by then, Dugan said.
Dugan emphasized that the pipeline was designed to withstand seismic activity. The vertical support members for the above ground sectors of the pipeline, such as on the North Slope, can accommodate up to two feet of pipeline lateral movement. In areas of particularly severe seismic activity, such as near the Denali fault in the Interior, the supports can accommodate up to 20 feet of lateral movement and up to five feet of vertical movement. And, even where the pipeline is buried, the construction allows some movement of the pipeline relative to the ground, Dugan said.
Fault activityThe Alaska Earthquake Center commented that, although the Aug. 12 earthquake was exceptionally strong, the general features of the quake are consistent with what can be expected from the activity of geologic faults across and to the north of the more easterly part of the Brooks Range. More than 4,400 earthquakes have been recorded in the region since 1970, although none has been as large as this recent one, the Alaska Earthquake Center said.
With an array of seismic recording stations having been installed in Alaska around five years ago, some quite close to the Aug. 12 earthquake, data from these stations should provide insights into how this earthquake happened. Currently the seismicity of the region is poorly understood, and nothing is known about the fault or faults responsible for the recent earthquake, the Alaska Earthquake Center said.
- ALAN BAILEY