Southeast Asia 2006

Problem: While drilling the 12-1/4” hole section on a production well a platform conductor slumped shearing the 13-3/8” casing and drillstring at 185m MD, leaving a fish in the openhole with the bit at ~2 m off the hole depth of 2029 m MD.  No hydrocarbon zones had been penetrated, but the open casing left a conduit below the platform which would constitute a stability hazard in the event of an underground crossflow from an adjacent well.  The risk was assessed and deemed unacceptable over the life of the platform and a remedial plug and abandonment relief well was planned.  The planning was started in earnest in the fall of 2005 and continued until the spud of the well in August 2006.
Remedial Strategy: The proposed plan was for a relief well to intersect the target well below the 13-3/8” casing shoe, followed by a cement plugging operation of the casing/dp annulus. A dual intersection above the 13-3/8” shoe depth by perforating the casing was planned in the event of poor hydraulic communication with the target well. As a float was installed in the lost BHA, combined with the barite sagged mud—which was confirmed during intersection—the drillstring was not considered as a potential flow conduit and attempting to place cement inside it was considered risky and unnecessary. Once all the potential flowpaths was confirmed as properly plugged, the relief well would be abandoned.
Special Services: John Wright Company was contracted to perform the investigation of utilizing a relief well to plug and abandon the well and budget the well, write the drilling program, and manage the ranging/intersection team offshore. In addition a John Wright engineer acted as the operations engineer based in the contractors office, coordinating all third party services, as well as the offshore team on the rig. Vector Magnetics was contracted through JWCO and responsible for electromagnetic ranging.

Challenges Met:  The project was complicated by the following:

  • The unconsolidated formations required careful planning of circulation rates, pipe rotation and reciprocation after drilling a section.
  • Circulation above TD resulted in an unplanned cement plug and high doglegs required to reach target. The high doglegs made the wire line conveyed ranging tool unable to pass to TD. This was successfully remedied by running open ended drillpipe past the high doglegs and washouts.
  • Achieving the parallel intersections and maintaining proximity within less than a few inches edge to edge, is possible only with specialist ranging support, close supervision of directional drilling, and focused management of the offshore specialist team.
  • The abandonment was achieved by drilling a stand alone relief well from a brand new Jackup drilling unit, with only one well drilled, operated by a new drilling contractor, with no injuries or accidents.
  • Hydraulic communication with target well confirmed it as a potential conduit for fluid flow to surface. This, not only made the proposed perforation program unnecessary, but more importantly justified the project.
  • Cement successfully placed in target well from the intersection point back to the break point.
  • Cement plug tested and confirmed to be of good quality.
  • Relief well plugged and abandoned.
  • Project was completed according to planned schedule and under budget.