Technology and methods for permanent plugging on the NCS

Specific attention has been devoted to the process used to document the qualification and use of the perforate, wash and cement (PWC) method. This is utilised to establish permanent well barriers, and the PSA has concentrated on experience transfer and learning related to how barriers are verified when using this method or new technology.

Qualify

The PSA has an overall responsibility to follow up that operator companies on the NCS qualify new technology and methods related to permanent plugging and abandonment (P&A) of wells, and that these new solutions meet applicable regulatory requirements.

Such qualification processes must be documented and verifiable, and thereby ensure both robust and cost-effective solutions in a long-term perspective.

In this knowledge-gathering, the PSA has secured information and documentation from ConocoPhillips, Equinor and Aker BP. It has given emphasis to the need for testing new technology, documentation of the qualification process, and differences and similarities in operator assessments related to the suitability and limitations of the method with associated results for establishing permanent well barriers.

Experience transfer

Experience transfer and lessons applied when qualifying PWC and further development of the method have been shared between the operators and will benefit other operator companies in the future.

The PSA believes that transferring experience and associated learning across operators will also be beneficial in similar projects where new technology and methods are qualified.

Through information sharing and experience transfer, the industry has jointly developed new guidelines in Norsok D-010 (revision 5/2021). These emphasise the opportunities and limitations of using PWC, and the need to establish a track record before the integrity of the cement plugs can be verified without associated drilling-out and logging.

Both section 9 of the facilities regulations, on the qualification and use of new technology and methods, and Norsok D-010 refer to the use of DNV-GL-RP-A203.

Best practice

Norsok D-010 emphasises the importance of establishing a best practice and a qualification matrix for using the PWC method. In cases where a PWC operation is not conducted in accordance with best practice, the plug must be drilled out and logged to verify the cement bond.

A relevant challenge is interpreting the cement bond logging when using jet-type PWC, since the large perforated holes make it more difficult to interpret the raw data.

Each well or application outside the limits set in a company’s internal best practice requires a new qualification process to verify the well barrier with the associated development of a qualification matrix. PWC must also be qualified when the method is used by other operators on different fields.

The report has been prepared for the PSA by the Reflekt consultancy.