Report Investigation of gas blowout on Snorre A - Well Integrity ...

In a preparatory meeting for RTD on 27 October 2004, the drilling and well engineering
group acceded to the wishes <strong>of</strong> the reservoir engineering group. In the third detailed planning
meeting on 2 November 2004, the original operations program was changed and adapted to
this decision.
Various methods were considered. Two <strong>of</strong> the alternatives were to pull the plug in the 2 7/8”
tail pipe or to perforate the tail pipe above this plug. The assessment <strong>of</strong> technical experts
from the supplier and the “slot recovery” project team in SNA RESU was that the method
with the greatest chance <strong>of</strong> success was perforation. Therefore, they decided to perforate the
tail pipe in order to pump cement past the HE3 plug and into the reservoir section.
The original plan was to pull the 5 ½” tubing before perforating the tail pipe. After cutting
and pulling the tubing, there would be a crossover from 9 ” to 5 ½”, which would lead to
problems in connection with subsequent entry with perforation tools. Therefore, a decision
was made to carry out perforation before the production tubing was cut and pulled.
The wireline company wanted the tail pipe to be perforated in brine (a heavy salt water
solution) before replacing this completion fluid with drilling mud. A better result was
expected if the perforation was done in brine, and this wish was also accommodated.
In the third planning meeting, the SNA RESU project team laid plans for:
• Perforation <strong>of</strong> the tail pipe,
• Pulling the scab-liner in a single piece, and pulling this through the BOP.
In addition, potential problems with the perforations in the 9 5/8” casing, in relation to
perforation <strong>of</strong> the tail pipe, were discussed, although none <strong>of</strong> these issues were identified as a
risk or a breach <strong>of</strong> barriers.
In addition to these planning meetings, several meetings were held with the suppliers <strong>of</strong> the
equipment regarding the details <strong>of</strong> the plan. For example, meetings were held with
Weatherford and Red Baron regarding cutting and pulling the 7 ” scab-liner, and with Baker
regarding perforation <strong>of</strong> the 2 7/8” tail pipe.
The fourth and final formal planning meeting was held on 11 November 2004. Both supplier
personnel and personnel from SNA RESU participated in this meeting, which started with a
review <strong>of</strong> the well's history before each individual sub-operation in the program was reviewed
and discussed.
A risk review (peer assist) for the entire program was planned for 12 November 2004. The
risk review was postponed because <strong>of</strong> a collision <strong>of</strong> meeting times, with subsequent
downgrading <strong>of</strong> priority on the part <strong>of</strong> the participants.
The program was submitted to SNA RESU management for verification, recommendation
and approval:
• Verified by the lead drilling engineer, 15 November 2004.
• Verified by the lead well engineer, 16 November 2004.
• Recommended by the drilling operations supervisor, 15 November 2004.
• Approved by SNA RESU manager, 16 November 2004.
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