Norway’s Petroleum Safety Authority (PSA) has issued an order after identifying several regulation breaches at Statoil’s Troll field, stemming from an investigation of an “out of control” incident that occurred last year.
The Songa Endurance, from Songa Offshore.
The PSA said in its report that based on the incident’s scope and potential, the agency regards this as one of the most serious well control incidents on the Norwegian continental shelf (NCS) since Statoil’s Snorre A incident in 2004.
The PSA carried out an investigation of the serious well control incident at the G-4 well on the Troll field with Songa Endurance on 15 October 2016. Statoil said in January that the incident could have been fatal.
Several breaches of the regulations have been identified, and the PSA has issued Statoil with an order.
The PSA’s investigation concluded that the direct cause of the incident was that large quantities of gas from the reservoir beneath the tubing hanger were released. Underlying causes are found to be multiple and complex, but can primarily be related to planning, management of change, expertise and understanding of risk, the PSA said.
According to the PSA, the incident on the Songa Endurance drilling unit occurred in connection with work on a production well on the North Sea field, which involved preparations to drill a sidetrack after permanent plugging of existing well paths in well 31/2-G-4 BY1H/BY2H.
The PSA’s investigation, launched on 17 October, revealed that in connection with pulling the tubing hanger, the top drive with the completion string was suddenly raised 6m out of control. At the same time, large quantities of fluid and gas flowed out of control up through the rotary table. This blowout lifted the 2.5-tonne hydraulic slips and threw some 2-tonne of bushings several meters across the drill floor. The liquid column reached the top of the derrick about 50m above the drill floor. Activation of a number of gas detectors led to local equipment shutdowns.
The blowout preventer was activated by drilling personnel immediately after the rising fluid column on the drill floor was observed and after the string shot up, the PSA said.
Stabilization of the well was not achieved until 26 October 2016 after a long and challenging period of normalization work.
The PSA agrees with Statoil in that although there were no physical injuries during the incident, under slightly different circumstances, it could have led to a major accident with the loss of several lives. In addition, the PSA said that substantial material damage and emissions/discharges to the natural environment.
In its report, the PSA identified several serious breaches of regulations, which include: compliance with procedures; design of well barriers; risk assessment as a decision base for improving the efficiency of the operation; expertise; and conduct of flow check.
“The identified nonconformities largely coincide with nonconformities identified after the investigated well control incidents on Snorre A in 2004 and Gullfaks C in 2010. Following these incidents, Statoil has done extensive and long-term work and implemented many measures to comply with the orders. Important improvement measures in Statoil do not appear to have had sufficient effect in parts of the company’s business,” the PSA said.
Statoil has now been ordered to identify why the implemented improvement measures failed, and the Norwegian giant must present its Troll improvement plan by 28 April.