New requirements were introduced in section 88 of the activities regulations in 2014 to regulate how long new exploration and production wells can remain plugged and abandoned on a temporary basis without continuous monitoring.

The main reason for the regulatory change was that the PSA had noted an increase both in the temporary plugging and abandonment of wells and in the number of years these remained in that condition.

Underlying this temporary status is the possibility that the same well path could be reused at a later stage. Re-entering a temporarily plugged and abandoned well for that purpose poses a risk if any of its barriers have failed in the interim.

The companies are responsible for following up the integrity of their wells, and categorise this on the basis of guidelines developed by the Offshore Norge industry association.

According to the regulations, a well must have at least two independent barriers. Wells are colour-coded to show the status of these protections – those rated green or yellow meet the regulatory requirements, while those in the orange or red categories do not because one of their barriers has failed.

Temporary and permanent plugging

A temporarily plugged well is intended to be re-entered and probably plugged permanently at a later date. Both the positioning (depth) and material of the barriers differ between the two types of plugging.


Barriers qualified from the perspective of eternity are required for permanently plugged wells, while the temporary type only needs ones which last for a specified period.


The wells are categorised in two ways – either monitored or unmonitored. Where a temporarily plugged and abandoned well without monitoring is concerned, the primary and secondary barriers are not continuously monitored and routinely tested as specified in a maintenance programme.

Measures taken

On the basis of knowledge acquired in earlier years and the regulatory changes in 2014, the PSA opted to send identical letters to the operator companies to secure an update to the number and integrity status of temporarily plugged and abandoned wells on the NCS.

Overall findings from this survey were acquired, collated and presented on the psa.no website in 2022 in order to underline the importance of paying constant attention to temporarily plugged and abandoned wells within a defined time frame.

Results

The survey showed that the number of these wells on the NCS declined from 269 in 2020 to 227 by 2022. Of the latter figure, 117 are planned to be permanently plugged and abandoned by 2030. Wells rated orange or red were reduced from 24 in 2020 to 17 in 2022.

Results from the 2022 survey also show that 63 of the 227 wells had been temporarily plugged and abandoned without continuous monitoring. Of these, 32 are now permanently plugged or returned to production. A further 32 exceed the time limit set in the regulations, which is two years for exploration wells and three for producers.

Figure: Historical trends for the integrity status of temporarily plugged and abandoned wells on the NCS (2011-22).

Effects

Following the persistent highlighting of temporarily plugged and abandoned wells, a number of the oldest exploration wells have been permanently plugged. In addition, wells with reduced integrity have received greater attention from NCS operators.

By acquiring information, collating data and actively exercising the see-to-it role, the PSA helps to minimise the risk of discharges from temporarily abandoned wells. The work also has an effect by increasing awareness of and knowledge about this type of issue.

Since section 88 of the activity regulations was amended, the attention paid to temporarily plugged and abandoned wells has prompted the companies to work more systematically on identifying the status of such wells and implementing measures.

The work has yielded a positive trend, where the operators comply to a great extent with such regulatory requirements as:

  • reducing the total number of temporarily plugged and abandoned wells
  • reducing the red and orange categories for well integrity status
  • evaluating a growing number of temporarily plugged and abandoned wells for conversion to permanent plugging
  • paying attention to qualifying new technology and solutions.

Purposeful efforts to develop and qualify new technology and materials could yield safer and more cost-effective solutions. Publishing data about temporarily plugged and abandoned wells keeps the industry informed about the volume of work involved and future technology needs.

Case: Follow-up of red wells

After mapping the extent of temporarily plugged and abandoned wells in 2020, the PSA followed up those with weakened integrity (rated red and orange). All were monitored and subject to a risk assessment, and the survey was updated in 2022.

In the spring of 2022, the PSA received a consent application for an intervention in one of the red-category wells. A close dialogue was pursued with the operator to follow up the risk assessments for this activity. The well was temporarily plugged and abandoned without continuous monitoring at the time.

When the operator began the work, challenges arose with a leaking valve. The PSA followed the operation closely from the sidelines, with daily updates provided by the operator. After three weeks, the barriers had been re-established and the well secured.

The PSA and the operator then met to sum up lessons learnt from the incident and how these could be utilised to reduce risk in further work with permanent plugging of the well in question.

This article is taken from PSA's annual report for 2022. The full report (in Norwegian only) can be read here.