North Sea
Norway 1989

Problem: During the drilling of a potential production zone with a near balanced condition, a simultaneous lost circulation and influx scenario occurred. After several days of attempting to kill the well, a backoff/sidetrack was planned. Wireline tools became stuck inside the drillpipe during the backoff operation. Well control was lost during a subsequent coiled tubing clean out operation on this North Sea HPHT well. Ultimately, the drillpipe had to be sheared leaving 4500 m of coil tubing inside the drillpipe. The wellhead pressure increased to over 10,000 psi, resulting in an underground blowout.
Remedial Strategy: A surface re-entry project utilizing a high pressure riser and snubbing unit (contracted and supervised by Boots & Coots) would be used in combination with a simultaneous relief well to regain control of the blowout. The relief well surface location was positioned 1100 m away and would intersect the open blowout wellbore below the bit, at a depth of 4705 m tvd. Heavy mud would ultimately be circulated by the relief well and monitored by the surface re-entry operation. A direct hit of the wellbore was necessary due to low fracture strength.
Special Services: John Wright Company (JWCO) was contracted near the end of the project through Boots & Coots to supervise the special services required for this project. Services provided included pre-planning and on-site supervision of directional drilling, surveying, and casing detection. Vector Magnetics, responsible for electromagnetic ranging, was coordinated through JWCO and worked together as one team.
Challenges: The project was complicated by the following:
  • Shallow gas charging required an 1100 m surface separation for the relief well.
  • A new relief well design was necessary to intersect the required kill target.
  • Kill liner was designed to be set at least 20 ft from the blowout open hole.
  • Directional control and surveying would be pushed to their practical limits.
  • Electromagnetic ranging would be critical to achieve well placement accuracy.
  • Kill equipment and connection to wellhead would be from a semi-submersible.
  • Team concept for special services was successfully and efficiently utilized.
  • A semi-submersible was successfully used for the relief well kill platform.
  • New relief well design (crossing without plugback) was successfully used.
  • Directional drilling and surveying techniques were successful with proper QC.
  • Electromagnetic ranging techniques were successful with new well design.
  • The 8-1/2" open hole was intersected with a direct hit at 4962m MD.
  • Th surface operation was integral for the evaluation of the kill hydraulics.
  • See SPE paper # 20420 for additional details.