Wyoming 1998

Problem: While drilling into the top of the main reservoir, a loss circulation condition occurred which ultimately resulted in the inability to progress further. The drillstring became plugged and up to ~11800psi was present on the annulus of the 9-7/8” casing. It was decided to put the well, which was producing ~40-45 MMcfpd at ~11000psi, on production and assess intervention options. A relief well contingency plan was in place shortly after the initial incident and identified critical issues, equipment and services. After approximately six months of continuous production, the surface casing ruptured, lifting the BOP stack, breaking several surface lines and resulted in a surface flow/crater situation. Due to the close proximity of a nearby railway track, the dispersed gas flow was ignited for safety reasons. The derrick and BOP stack were engulfed in flames, preventing any further surface operations. Estimated surface flow was in excess of 70 MMcfpd. See Figure 1.
Remedial Strategy: The relief well option was implemented without delay from a nearby well drilling operation having a 3879’ surface displacement. Estimated intervention time was approximately 4 months to build, hold and drop profile well. The relief well would be planned with a cross-by followed by a close proximity interval to accurately locate the blowout wellpath. After setting the 9-7/8” casing string at ~200’ TVD above the target well 9-7/8” shoe, a short interval would be drilled to intersect the blowout. A substantial kill pumping plant would be necessary to successfully kill the uncontrolled well. A plugging operation would commence immediately after killing to permanently plug the well.
Special Services: John Wright Company (JWCO) was contracted to supervise the special services required for the relief well intervention project. This would include pre-planning and on-site supervision of directional drilling, surveying, kill operations and casing detection. Specialists for directional drilling, borehole uncertainty and hydraulic simulations remained on site full time during the project. Vector Magnetics, responsible for electromagnetic ranging, was coordinated through JWCO on this project and worked together as one team. Well Flow Dynamics simulated various kill scenarios for the kill operations, both surface and relief well kills.
Challenges: The project was complicated by the following:
  • The surface displacement was high, caused by the decision to redirect a vertical well currently being drilling adjacent to the blowout.
  • MWD surveys existed, but no onsite QA/QC controls were instituted.
  • The kill/intersection point must be above the loss zones due to casing string constraints/availability.
  • Kill operation was influenced by the prolific blowout rate, several loss/producing zones and the requirement to intersect at the 9-7/8” shoe openhole interval
  • The 'team concept' for special services was successfully and efficiently utilized.
  • The blowout well MWD surveys were found to be fairly accurate and the well was found to be within 25’ of the calculated position.
  • The relief well crossed the blowout well at ~12’ and then dropped to vertical.
  • During the cross-by losses caused the blowout well to bridge and surface flow dropped dramatically.
  • The surface operation required locating the wellhead and cutting of the casing strings prior to setting up the snubbing unit and plugging the well.
  • A milling and hydro-jetting operation severed the blowout well drillpipe and no fluids were lost or gained, i.e. drillpipe was plugged.
  • After extensive repairs to the platform structure, field development was continued.