Negative Other LL with DNO

Oselvar (A-1 H, A-2 H, A-3 HT2) – P&A

PSA Finding

• Use of 1 long cement barrier for 2 potential flow zones (res + Forties fm).
• According to internal requirements Repsol only qualified the top barrier element of the long cement plug (should be tested separately).
• Repsol deemed it necessary to only verify barriers for the first 3 wells and the barrier verification for the remaining 28 was planned to be excluded if they followed an internal job matrix.
• Unqualified personnel interpreting CBL logs to verify cement.
• Interviewed personnel lacked knowledge of own internal P&A requirements (e.g. 30m min. length cmt barrier).
• Insufficient barrier verification of surface plug inside casing and annulus (tagging and P/T).
• Lacked internal deviation registration for the above points.

PSA Comments

Risk/opportunity:
• Isolate 2 zones (res + Forties fm.) in one continuous cement plug and only verify the top of the second plug, to save time.
• Log, verify and qualify barriers for the first 3 Gyda wells and skip that step for the remainder if the cement operation was a success, to save time.

Comments: • NORSOK D-010 Rev. 4 15.22 D2a) states that qualified personnel must interpret logs, but what defines “qualified”?
• NORSOK D-010 Rev. 4 15.24G states that when using common well barriers, the cement must be dressed off, but does not state if a separate verification of the lowest plug is needed when 2 plugs are set on top of each other, as one. If the reservoir and the flow potential zone can be considered as one reservoir, then NORSOK D-010 Rev. 4 allows for 1 long continuous barrier.
• NORSOK D-010 Rev. 4 15.22D2b) states that it is acceptable to forego the barrier verification (csg. cmt) given successful log in similar cement jobs.