Apr 062011
 
Shell's Draugen platform photo: Shell

Shell's Draugen platform photo: Shell

Norway’s Petroleum Safety Authority Norway (PSA) has given A/S Norske Shell (Shell) a notification of order following completion of the investigation of a well incident on Draugen in December 2010.

The incident on the Draugen facility occurred in connection with a wireline operation in well 6407/9-A-01 on 4 December 2010. Shell was the operator and Seawell AS (Seawell) was the contractor for the wireline operation. The objective of the wireline operation was to replace a gas lift valve.

To replace the gas lift valve, the subsurface safety valve must first be extracted from the well. As the subsurface safety valve was pulled through the Xmas tree, it became stuck. The remaining barrier element in the Xmas tree, the upper master valve, was blocked.

Normalisation of this incident by re-establishing the well barrier situation was completed on 8 December 2010. To limit risk connected with this well, the subsurface safety valve was run back into the well. Subsequently, two mechanical bridge plugs were inserted in the well above the subsurface safety valve. The other valves in the Xmas tree were closed, pressure-tested and accepted.

The incident did not result in any injury to personnel. The scope of material damage in the Xmas tree was not known at the time of the incident, however, the incident involved major accident potential in a situation with only one remaining barrier against hydrocarbon outflow from the well.

Cause of the incident
The direct cause of the incident was the subsurface safety valve becoming stuck in the Xmas tree. When equipment becomes stuck, there can be increased strain on the equipment due to tugging and pulling to free the tool string.

It is not possible to establish fail-safe methods for preventing things from becoming stuck in the Xmas tree during wireline operations, but robust solutions, analyses and a correct understanding of the risk that may be expected, can contribute to prevent the loss of well barriers if something gets stuck.

Identified nonconformities
The PSA’s investigation of the incident has identified several serious breaches of the regulations. The nonconformities are related to:

  • Inadequate management
  • Inadequate risk assessment
  • Inadequate well barriers
  • Inadequate well barrier sketches
  • Inadequate well control
  • Inadequate daily reporting of drilling and well activities

Based on the investigation report, Shell is notified of the following orders:

Pursuant to Section 69 of the Framework Regulations relating to administrative decisions, cf. Section 6 of the Management Regulations relating to management of health, safety and the environment, Section 12 of the Management Regulations relating to planning, cf. Section 29 of the Activities Regulations relating to planning, Section 4 of the Management Regulations relating to risk reduction, Section 5 relating to barriers, Section 16 relating to general requirements for analyses and Section 17 relating to risk analyses and emergency preparedness analyses,

a) AS Norske Shell is ordered to assess, as well as test its own criteria for continuing well intervention in 6407/9-A-01, at the same time as ongoing production from other wells at the facility in an emergency situation when barriers are lost, cf. nonconformities 5.1.1 and 5.1.2 in the report.

Pursuant to Section 69 of the Framework Regulations relating to administrative decisions, cf. Section 6 of the Management Regulations relating to management of health, safety and the environment, Section 20 of the Management Regulations relating to registration, review and investigation of hazard and accident situations, Section 86 of the Activities Regulations relating to well control, Section 16 of the Management Regulations relating to general requirements for analyses and Section 17 relating to risk analyses and emergency preparedness analyses,

b) AS Norske Shell is ordered to assess its own criteria for implementing internal investigations or investigating serious incidents with loss of barriers in the well area on the Draugen facility, cf. nonconformities 5.1.1 and 5.1.3 in the report.

Pursuant to Section 69 of the Framework Regulations relating to administrative decisions, Section 6 of the Management Regulations relating to management of health, safety and the environment, Section 23 of the Management Regulations relating to continuous improvement, Section 86 of the Activities Regulations relating to well control, Section 5 of the Management Regulations relating to barriers and Section 45 of the Activities Regulations relating to maintenance,

c) AS Norske Shell is ordered to assess its own criteria for prudent well control and the need for risk-reducing measures when implementing well intervention in the well area on the Draugen facility, cf. nonconformities 5.1.1 and 5.1.5 of the report.

The deadline for complying with the order is set at 1 June 2011. We must be notified when the order has been complied with.