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Notification of order following investigation of well incident on Ekofisk

In 1994, the Ekofisk 2/4 C-16 well was stimulated by pumping liquid into the reservoir under pressure. In connection with this stimulation, the 9-5/8" casing hanger probably fell into the hole. ConocoPhillips Skandinavia AS (CoPSAS) discovered this well situation in mid-2005, and notified the PSA about the incident in September 2005. Based on our own investigation of this matter, we have issued a notification of order to the company.

Actual consequences of the incident
Ekofisk 2/4 C-16 has produced since 1994, with just one qualified well barrier. As of today, the well does not have a documented secondary well barrier in connection with production where all barrier elements in the envelope are intact. According to CoPSAS, the well will remain shut in for further production until the secondary barrier is restored.

Potential consequences of the incident
The primary barrier, consisting of the production tubing, production packers and downhole safety valves (DHSV) are intact. Failure of one of these barrier elements would have entailed well pressure against an unqualified barrier in annulus B.

Closing the production tree would have prevented flow to the facility, although the well's integrity has not been maintained. The worst possible consequence of such a failure is a subsurface blowout.

The Ekofisk 2/4-C facility does not have a derrick or other heavy equipment on board that can be mobilized at short notice to prevent escalation of a hazardous situation.

Direct causes
The direct cause of the casing hanger falling down during the 1994 stimulation operation was lack of capacity in relation to the actual loads.

The direct cause of why it took 11 years to ascertain that the casing hanger had fallen down was that the failure was not identified. Therefore, necessary measures were not implemented in spite of the fact that full annular communication was noted in the well in connection with well activities in the period 1994-2005.

Several similar incidents on Ekofisk
The investigation report notes that the Ekofisk 2/4 A-20 and 2/4 W-05 wells have experienced similar incidents with casing hangers.

Serious circumstances
The PSA takes a serious view of the fact that it took 11 years to identify that the casing hanger with the primary packer had fallen through the wellhead. It is also worrisome that the company chose to use a new type of wellhead for its facilities without adequate quality assurance of its design and fabrication.

Notification of order
To ensure that CoPSAS prudently operates its wells with similar wellhead arrangements in the future, we have given notice of the following order:

Pursuant to Section 58 of the Framework Regulations relating to individual decisions, cf. Section 2 of the Management Regulations relating to barriers, Section 23 of the Activities Regulations relating to use of facilities and Section 44 of the Activities Regulations relating to maintenance programs, CoPSAS is ordered to:

  1. Document sufficient strength of the elements in the well barriers in relation to the loads they may be subjected to, cf. Section 8.1.1 of the report.

  2. Determine restrictions for further use of wells with similar wellhead arrangements, as a consequence of insufficient strength of casing hanger and possible lack of well integrity, and follow up to ensure compliance with these restrictions, cf. Section 8.1.10 of the report.

  3. Develop a plan with specific and binding measures, both short-term and long-term, to ensure that the wells comply with regulatory requirements, including preparation of procedures to monitor the condition of well barriers, cf. Section 8.1 of the report.

  1. ~LT~/LI>

Pursuant to Section 58 of the Framework Regulations relating to individual decisions, cf. Section 3 of the Management Regulations relating to management of health, environment and safety and Section 11 of the Management Regulations relating to manning and competence, CoPSAS is ordered to ensure that:

Personnel responsible for the technical condition of critical safety equipment have sufficient competence, time to evaluate the condition of the equipment, and the necessary authority to carry out these responsibilities, cf. Section 8.1.7 of the report.

The deadline for complying with the order is set at 1 December 2006. The PSA must be informed when the order has been carried out.

We have informed CoPSAS that any comments concerning the notification must reach the PSA within three weeks after receipt of this letter.

Link: Explanation of the terms "order" and "notification of order"

Contact in the PSA:
Inger Anda, press spokeswoman
E-mail: inger.anda@ptil.no
Tel.: +47 970 54 064