Ekofisk 2/4, the first fixed oil production platform on the field, was shut down in September 2013 after 40 years of service. Permanent P&A of the wells started in August 2014.
During the two-day audit this June, the PSA examined how the operator had planned and executed the permanent plugging.
It emerged that 18 of the 23 permanently plugged wells at Ekofisk 2/4 A lacked documentation demonstrating compliance with regulatory requirements in Norway for permanent well barriers.
PSA also found no evidence of an adequate risk assessment of wells with deficient or defective permanent well barriers, with regards to potential leaks over time.
Following the audit, PSA has asked ConocoPhillips to demonstrate by Dec. 1 that it is acting to meet the regulatory requirements, from a long-term perspective.