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AOGCC calls well integrity ahearing after Prudhoe incident
AOGCC wants to gather evidence following second surface leakage incident involving wellheads in field; orders data for other wells
Alan Bailey Petroleum News
The Alaska Oil and Gas Conservation Commission has scheduled a public hearing on Feb. 7, to assess the mechanical integrity of wells in the Prudhoe Bay field, operated by BP. The hearing announcement follows a second incident involving the leak of fluids from wellheads at Drill Site 2 in the field. The fact that two leaks have now taken place is causing the commission to worry about the mechanical integrity of Prudhoe Bay wells in general and to conduct an inquiry into well integrity in the field. Hence the Feb. 7 hearing.
The first incident occurred in April 2017, when two leaks in the wellhead structure of well 02-03 generated a spray of oil and gas that impacted the well pad. The leaks happened as a result of the wellhead structure rising by 2 to 3 feet and striking parts of the well house. The latest incident happened on Dec. 12, 2018, when gas with an oil mist escaped from the head of well 02-02 on the same drill site. BP is still investigating the cause of that leak, which released about 750,000 cubic feet of gas and two gallons of oil.
In its Feb. 7 hearing AOGCC wants BP to review its findings and actions relating to the two leakage incidents, and the steps that the company is taking to prevent similar incidents in the future. The agency also requires more general information from the company about steps it is taking to monitor and prevent any well integrity problems at Prudhoe Bay.
“We are of course working with the state to address the concerns and doing everything we can to get them the information they’re requesting for the hearing,” BP spokeswoman Megan Baldino told Petroleum News Jan. 15.
Permafrost subsidence BP determined that the leak in 2017 had resulted from subsidence of the permafrost that surrounded the well, in a situation involving an old three-casing well design in which the bottom of the surface casing was located above the base of the permafrost. It appears that hot fluids in the well had melted some of the surrounding permafrost, thus reducing the permafrost load on the surface casing.
Following its investigation in 2017, BP shut in 14 wells that have the same casing design as the well that failed. The company initiated a risk assessment of those wells and of nine other wells that had a three-casing design, but with the bottom of the surface casing below the permafrost. The company also undertook surveying of permafrost subsidence at Drill Site 2. The shut-in wells included the 02-02 well that has now leaked - according to information supplied to AOGCC by BP, the company has been in the process of plugging and abandoning that well.
AOGCC concurred with BP’s assessment of the cause of the 2017 incident and issued an emergency order requiring all North Slope operators to shut in wells of a similar design to the 02-03 well by the end of that year.
BP has now told the commission that it has identified eight additional wells that have surface casings set in the permafrost - one of these wells has been plugged, one is not operable and the remainder have been declared operable following engineering reviews. Two additional wells with surface casing set right at the base of the permafrost were made not operable.
In response to the latest fluid leakage incident, AOGCC has ordered that any further work done on the 14 wells of suspect design will require written approval from the commission, rather than using permitting guidelines for the wells. The commission has also ordered that these wells be plugged immediately, and that they be plugged and abandoned by the end of 2019. Within the first 90 days of 2019 BP must provide evidence that the wells have been securely plugged, that they have passed mechanical integrity tests, and that well tubing and annuli contain fluids “that will overbalance the reservoir.”
Further information required During the Feb. 7 hearing the AOGCC will require a review by BP of the well 02-03 and 02-02 incidents, with BP’s assessment of how to prevent similar incidents in the future. The commission also wants information regarding permafrost subsidence management in the Prudhoe Bay unit, and on work conducted to understand the well leakage incidents and to prevent similar events. And the commission seeks information about any permafrost subsidence issues throughout the unit, about any wells that have failed integrity tests as a result of subsidence, and about BP’s subsidence surveillance program. BP must also provide information about its well long-term shut in program, the commission has said.
- ALAN BAILEY
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