Bangladesh
1997-98

 Problem: After drilling to the kick-off point in 17-1/2” hole a swab kick was encountered which resulted in the well unloading and put on diversion at a tremendous rate. Almost immediately the well cratered around the 20” casing and wellhead, soon thereafter the gas ignited. The rig and nearly the entire location sank into a large water filled crater. After burning for several weeks the well bridged high and resulted in gas charging the surface sands for hundreds of meters around the wellhead resulting in numerous gas boils erupting to the surface.
Remedial Strategy: With a cratered wellhead the only intervention options were to drill a relief well. Immediately a suitable rig was located in the region that could be mobilized to the remote location by road. Kill pumping equipment including mud and cement plants where also mobilized. Two intersection points were planned (one primary and 1 secondary) as two permeable gas sands had been opened by the 17-1/2” hole. Due to the surface gas evolution the relief well surface location had to be placed 620m from the crater. The shallow targets (800m) required high inclinations in the relief well which included a bypass and plugback to reach the targets.
Special Services: John Wright Company (JWCO) was contracted to supervise the special services required for this project. Special services included pre-planning engineering and on-site supervision of directional drilling, surveying, casing detection, intersections and kill hydraulics. The field operator and drilling contractor supervised the normal drilling activities. Vector Magnetics was contracted and was responsible for electromagnetic ranging services. Well Flow Dynamics performed the hydraulic simulations. Alert Disaster Control (Singapore) supplied fire pumps, safety and medical support and all worked together with JWCO on this project as one team.
Challenges: The project was complicated by the following:
  • Logistics in the region where very complicated requiring long range planning.
  • Continual political problems had to be addressed on top of technical difficulties.
  • Shallow gas charging complicated the entire project requiring high inclination and dog-leg well trajectories, possibility of relief well blowout in surface hole, safety issues as the surface gas escape continually spread outward toward the RW Rig.
  • Shallow soft sands created very large washouts in the blowout well making kill hydraulics and plugging extremely difficult.
Results:
  • Surface and 13-3/8” casing was set through the shallow sands without incident.
  • Communication was achieved during the bypass and confirmed at the crater
  • Large volumes of cement and DOBC gunk were placed at this depth.
  • Deeper intersection made in shale above the upper gas sand, cement plug here.
  • Intersection made above lower gas sand, losses stopped with sand then cement.