The Petroleum Safety Authority Norway (PSA) has decided to investigate a well incident on the Gjoa on 20 September 2020, when the drill string became stuck fast and blocked the blowout preventer (BOP).
This incident occurred during drilling of production well 35/9-G-4 H on the North Sea field by the Deepsea Yantai mobile unit.
Gjoa is operated by Neptune Energy. Deepsea Yantai is operated by Odfjell.
The well had already entered the reservoir section when the string became stuck in the formation while it was being pulled out. During efforts to free it, the string separated into two sections.
These parts of the string blocked the BOP so that the latter was unable to close and prevent a potential wellstream leak.
No discharges resulting from the incident have been reported.
Neptune Energy reports that a cement plug has been inserted against the reservoir so that barriers have been restored. Work is still under way to remove the two drill string sections from the BOP.
The PSA regards the incident on Gjoa as serious, and an investigation team drawn from its specialist staff is starting work immediately.
It will concentrate on the planning of the well and implementation of the drilling operation up to the point when the incident occurred.
The main objective of the investigation is to identify the causes of the incident and possible lessons to be learnt, and to share this information with the industry.
In conducting its investigation, the PSA will
- review the course of events
- assess the actual and potential consequences of the incident
- identify direct and underlying causes
- identify nonconformities and improvement points related to the regulations
- apply necessary enforcement powers to correct possible regulatory breaches
make public its findings
- contribute to experience transfer to and learning by other players in the petroleum sector.
- The investigation will be summed up in a report published at psa.no.