AOGCC will issue rule on annular pressure management at Prudhoe Bay

BP to submit plan to include notifying commission of wells with pressure communication and obtaining approval to operate such wells

Kristen Nelson

PNA Editor-in-Chief

The Alaska Oil and Gas Conservation Commission said Jan. 16 that it has decided that a rule addressing annular pressure management in Prudhoe Bay field development wells is appropriate to protect worker safety. That rule would require Prudhoe Bay field operator BP Exploration (Alaska) Inc. to keep the commission informed about wells with pressure communication or leaks, and to get permission from the commission for the continued operation of such wells.

The commission said it will issue a proposed rule for public comment after it has received and reviewed information from BP, the Prudhoe Bay field operator, including results of a hazard study of wells at Prudhoe that “exhibit pressure communications or leakage in any tubing or packer or casing” and a proposal for an annular pressure management program for all Prudhoe Bay development wells.

Until the commission issues a rule, it is requiring BP to comply with annulus pressure management programs in the company's well integrity waiver policy; the company's well startup procedures as described to the commission at its Nov. 14 hearing; a commission letter dated Oct. 29 from Cammy Taylor, commission chair; and any modifications or updates of those approved by the commission.

Explosion triggered hearing

The commission received two written public comments for the November hearing, both calling for more oversight by the commission of BP's operations at Prudhoe Bay.

The A-22 well explosion occurred when the well was started up. BP told the commission that since the explosion, it requires continuous monitoring when wells are started up and has provided additional training provided on startup procedures. The rate of startups is limited, BP said, by the availability of staff to monitor wells.

Commission findings

At Prudhoe Bay, some 17 percent of wells “currently have, or are under consideration for, an operator approved 'waiver' that enables operation of a well outside of established parameters.” BP told the commission in November that some 260 wells have waivers or are under evaluation for waivers.

The commission said it has annular pressure management requirements for injection wells, but doesn't have such requirements for producing wells. The Minerals Management Service, American Petroleum Institute and the Gulf of Mexico Offshore Operators Committee are working on recommended practices for Gulf of Mexico wells with sustained casing pressure, the commission said, and expect to complete that work in two to three years.

Rule appropriate

“The objectives of such a rule are to protect worker safety through proper management of well pressures by preventing circumstances that could result in an uncontrolled release of oil and gas, the unintended movement of fluid outside the wellbore and the catastrophic failure of a well.”

There are a variety of well completions and producing well characteristics at Prudhoe, the commission said, and a rule must recognize those. It also noted that existing BP annular pressure management practices may provide the basis for a commission rule. Engineered solutions such as controls or pressure relief systems may satisfy some objectives of such a rule, the commission said.

But, it said, the focus and timing of the offshore Gulf of Mexico work toward an industry recommended practice “does not satisfy the near term need for a rule for the Prudhoe Bay field.”

Information required

The commission said it wants the results by Feb. 14 of a BP hazard study identifying and evaluating potential hazards and addressing mitigation pressures “to prevent a cascading loss of well integrity” at wells with pressure communication or leakage in tubing or packer or casing.

By March 3, BP is to submit a proposal for an annular pressure management program for all Prudhoe Bay development wells, including: routine monitoring of tubing and casing annuli pressures; notification of the commission when there is an indication of pressure communication or leakage in any casing, tubing or packer in a well; timely diagnostic testing to determine well integrity and the potential source of pressure communication or leakage; classification of wells according to risk; commission approval for continued operation of a well with pressure communication or leakage; safe management of annular pressures during well start up and operation; and clear operating limits for wells exhibiting pressure communication or leaks. Those limits, the commission said, would include “when it is no longer safe to continue operating a well.”

The commission has also told BP to provide a work scope and schedule by March 3 for a study of mechanical pressure relief options and to provide a copy of current 'Notice of Waivered Well' forms it has issued on development and service wells to the commission by Feb. 14.

BP cooperating with requests

Beaudo said the commission's order “appears to codify most if not all of the actions we have either already pledged or taken.”

He said that whether or not BP challenges the order, “we believe we have put in place measures that will maintain the safe operation of wells with high annular pressures.”

He also said that annular pressure management is not a condition which occurs only at Prudhoe Bay, and said BP does “not know what other implications or regulatory changes there may be for other producing fields.”

Pressure exceeded design burst rating

Kristen Nelson, PNA editor-in-chief

BP said the immediate cause of the A-22 explosion was “contained thermal induced expansion of fluids trapped in the annulus.”

Among contributing causes BP listed communication between the inner annulus and outer annulus allowing pressures to equalize over time to the inner annulus gas lift pressure of about 2,000 pounds per square inch; and the well house design which “resulted in unsecured materials (e.g., wooden boards, gravel) that were hazardous when propelled during the initial gas/fluid release.”

BP also said the inner annulus continued to provide gas to fuel the fire because of damage to a valve.

The company also listed procedural and implementation issues: “Procedures for bleeding down and monitoring annular pressures did not fully address key issues and were not consistently implemented in the field,” BP said. And the outer annulus pressure was not bled down at start-up or during warm up of well A-22.

BP shut in 137 wells after the explosion for hazard review, reviewed the company's well integrity program and revised testing and operating procedures.

“Operating procedures have been revised to require operators to remain on the pad during startup of wells with outer annulus pressures that exceed 1,000 psi,” the company said. It also said it has created a database with pressure readings that is accessible to all field personnel.

Safety issue in Alaska

In 2002 there was the August A-22 well explosion and the tragic December accident at Gathering Center 2 that killed a welder working for Norcon, he said, a total of more than 11 recordable injuries and one day-away-from-work case per month.

“That's the legacy of BP's safety performance in Alaska in 2002. It is one that we cannot, we must not, and we will not repeat in 2003. Or ever again,” he said.

Worldwide, BP's global performance in 2002 was much better than in Alaska, Marshall said. To meet those standards in Alaska the company must have no more than one day-away-from-work case per quarter; no more than three recordable injuries per month; and no more than one vehicle incident per month.

“And we'll achieve these targets legitimately,” he said, “not by failing to report incidents or hiding them.”

The goal, he said, is to “set a new standard for safety excellence and strive to ensure that no one is every hurt again while working for BP in Alaska.”

What happened at A-22

BP's well integrity group gave approval to initiate production Aug. 15, as long as surface casing annulus pressure did not exceed 2,000 pounds, the company said.

On Aug. 16, some five hours after the well was put on production, the 13-3/8 inch casing failed 17 feet below grade and lift gas and fluid flowed up the 20 inch conductor by surface casing annulus, blowing gravel and boards up into the well house, BP said. The gas was ignited — possibly by a spark from flying debris or electrical equipment damaged by the blast — and the A-pad field operator, who was standing outside the well house prior to bleeding the annulus pressure, was injured by the explosion and fire.

The ruptured casing was recovered and sent to the Edison Welding Institute. BP Exploration (Alaska) spokesman Daren Beaudo told Petroleum News Alaska Jan. 21 that the institute's pressure test showed the casing to be in good shape and “pressure of perhaps as high as 7,700 psi caused the burst.”

The casing, Beaudo said, has a design rating of about 5,300 psi. BP said in its final incident summary that the institute found no evidence of cracking, wear or corrosion affecting casing strength and said the casing fracture was characteristic of over-pressure failure.