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BP halts production from 150 slope wells Wells will be shut down, restarted after testing, in a process expected to take about a week, following Aug. 16 explosion which injured worker Kristen Nelson PNA Editor-in-Chief
BP Exploration (Alaska) Inc. began shutting in production from some 150 oil wells on the North Slope Aug. 23 for diagnosis after an Aug. 16 explosion injured a worker.
BP said Aug. 24 that it is halting production from the wells as a precautionary measure while it confirms the integrity of subsurface well casings in wells with high outer annulus pressure. An annulus is the space between the casings used to construct an oil well.
The company began shutting in wells Aug. 23, BP Exploration (Alaska) spokesman Ronnie Chappell told PNA Aug. 25, and expects the process to take about a week.
A BP employee was seriously injured Aug. 16 when a casing burst on the Prudhoe Bay A-22 well, resulting in an explosion and fire. BP said that prior to the incident, pressures in excess of 2,000 pounds per square inch were recorded in the outer annulus of the A-22.
The halt in production from about 150 wells is expected to result in a production impact of about 60,000 barrels of oil per day, representing about 6 percent of total North Slope production, the company said.
Team recommended shut down A team of BP operators and technical experts assembled to investigate the incident recommended that the company halt production from about 150 wells with outer annulus pressures greater than 1,000 pounds per square inch until casing integrity can be confirmed, the cause of the A-22 casing failure determined, and procedures for operation of these wells are reviewed and revised.
The team was led by Fritz Gunkel, BP’s Northstar delivery manager, not part of the Prudhoe Bay organization, and included representation from Phillips Alaska Inc. Team members included BP technical experts from the Lower 48 and brought both technical expertise and real-world expertise to the investigation, Chappell said.
BP said that casing used in the construction of the well had an original pressure rating in excess of 5,000 pounds per square inch. The investigation team so far has been unable to determine why the outer annulus casing failed at a pressure significantly lower than its original pressure rating.
Some wells killed Chappell said the process involves more than just turning valves.
“In some instances,” he said, BP is “actually pumping water down wells to kill them, so they will not flow to the surface.
Some wells are easier to shut down.
“Many of the wells in question are gas-lift wells,” Chappell said, “and turning off gas-lift gas and depressuring the gas-lift system will also put the wells in a condition where they won’t flow.”
The process of taking the wells off line is expected to take about a week, he said. “Concurrently with that we have a team on the North Slope developing procedures to reconfirm the safety of casings in these wells and reviewing and revising our procedures for the safe operation of these wells.
“We expect to be in a position to begin bringing wells back on line at about the time that the shut-in process is complete,” Chappell said. “We aren’t able to do the two things simultaneously because the people and equipment required to shut in the wells are the people and equipment that would do the testing and re-commissioning of the wells.”
Chappell also said BP has people assessing testing protocols and operating procedures who will be recommending changes so that BP can begin to implement these changes when the shutdown process is completed.
BP is looking at all the areas it operates on the North Slope, he said, but the vast majority of the 150 affected wells are within the greater Prudhoe Bay field where there are some 1,600 to 1,700 wells. The 150 wells have outer annulus pressures in excess of 1,000 psi, Chappell said. The A-22 well, where the explosion occurred, had a relatively new onset of pressure and a diagnostic crew had been sent out to assess the well. He said it was approved for continued operation with an outer annulus pressure not to exceed 2,000 psi, which “tends to be the threshold at which approvals are issued to operate wells of this type.”
“The original pressure rating on the casing used to construct this well is in excess of 5,000 psi,” he said.
Phillips reviewing its procedures Philllips doesn’t plan to shut in any Kuparuk wells but is in close contact with BP, has two members on the task force and is reviewing its own well operating and safety procedures, Phillips Alaska spokeswoman Dawn Patience told PNA Aug. 26.
Phillips is taking the problem very seriously because of concerns about the safety of the company’s employees and contractors, as well as environmental concerns, Patience said.
“We are in close contact with BP to learn all we can about the A-22 well and Phillips has two members on that task force.”
“Phillips doesn’t plan to shut in any Kuparuk wells,” she said. “A review of our current well status and operating procedures — which we just completed — did not reveal any immediate safety concerns that warrant wells be shut it.”
Patience said Phillips initiated the just-completed review as a result of the A-22 explosion.
Phillips is not reviewing its wells at Alpine, she said, because no wells in that field are operated under conditions similar to the Prudhoe Bay well.
“We believe the operations of the Kuparuk wells are safe, however, in light of the BP incident we are reviewing our wells operating and safety procedures,” she said.
Commission investigating A-22 The Alaska Oil and Gas Conservation Commission has initiated an investigation into the A-22 incident, Jim Regg, a commission petroleum engineer who is leading the commission’s investigation, told PNA Aug. 26. The commission is still in the process of gathering information, he said, has “met with BP and talked with them extensively.”
The commission has had a good exchange of information with BP, Regg said. “They’ve been quite open and have cooperated.”
Regg said the commission is “looking at the well, the well design, how the well has operated in the past, BP’s polices and procedures.”
The commission is also gathering information on the shutdown: “One of the things we want to understand is the criteria for shutting in the wells,” he said.
The wells are being shut in “to do some additional diagnosis” of what’s going on with the wells.
The commission will be involved in the decision to bring the wells back on line, Regg said.
“The commission will let wells come back online only if they can be produced safely — not just environmentally, but to the people operating the wells,” he said
Regg said the commission hasn’t yet had discussions with Phillips but will in the future because “we do have analogous situations in other fields.”
Way beyond normal shut in Regg said that as the commission looks at the wells, “it’s likely we’ll find wells that have identical characteristics” and some wells “will probably be signed off on as a group” while other wells will require individual attention. The commission wants to learn as much as possible about the wells, he said, and will look at diagnostics on the wells and issues other than pressure before the wells are brought back on line.
“It’s important to recognize that they’re going way beyond what would be a normal shut in,” Regg said.
“They’re being very cautious in the wells. They don’t want to miss anything. Precaution is warranted but that part of it needs to be recognized: there is a high amount of caution going into the number of wells” that BP has shut down.
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