||Problem: During a trip
out of the hole for a logging run, the well began flowing when the HWDP were reached. The
well was shut-in with the pressure reaching 1200psi before stabilizing at 900psi. After
circulating kill mud for two days, the pressure reduced to zero and a slick BHA was RIH
for a cleanout trip. A bridge was found at the shoe and after drilling 1-1/2 singles, the
kelly and 4 joints of DP were ejected prior to the shutting in of the BOPs. The well was
blowing out underground through a highly permeable shallow sand. Plumes and craters had
formed at the outcrop of the 20° dipping formation two days after the initial kick.
Blowout rates were estimated to be greater than 150 million cfpd.
After a new BOP stack and diverter system was installed, a snubbing unit ran a string of
4-1/2" DP to 1086m TVD. Two unsuccessful dynamic kill attempts were made prior to the
drilling of the relief well. The relief well was planned to intersect the drillpipe in
openhole followed by a dynamic kill. Once the static kill was achieved, the pumping of
reactive plugging materials from the two wellbores would be performed. The blowout well
drillpipe allowed for pressure monitoring during the kill and provided an additional kill
string for the pumping of the highly reactive kill/plugging materials.
|Special Services: John
Wright Company (JWCO) was contracted through Boots & Coots L.P. to provide blowout
control engineering and to supervise special services for the project. Services included
the engineering planning and supervision of relief well and surface kill operations.
Vector Magnetics, providing casing detection services, and Well Flow Dynamics, responsible
for kill simulations, worked together with the JWCO to create a single team.
|Challenges: The project
was complicated by the following:
- The integrity of the wellhead vicinity was suspect and
cratering could occur.
- A relatively thick salt formation was washing out and
increased kill rates.
- A shallow supercharged zone complicated kill dynamics for
this high rate well.
- Low formation strength and fluid loss problems required
- Only magnetic singleshot borehole surveys were available.
- Topographic restrictions, diverter layout and plume exit
area severely limited suitable relief well locations.
- Remote location increased logistical problems, including
availability of kill fluids materials, high pressure pumping equipment, mud plant, and
- Intersection of a welbore in a salt formation had never been
- The producing formation fracture/kill pressure envelope was
- Team concept for special services was successfully and
- A direct openhole intersection was performed in the salt
formation with special electromagnetic ranging techniques.
- The blowout bottomhole location was within 2m of the
- The pumping of reactive fluids/materials to form a plug
during a relief well intervention project was an industry first.
- A dynamic kill program of mud in RW annulus, cement down RW
drillpipe and sodium silicate down blowout drillpipe ultimately killed and plugged the
- Kill volumes were in excess of 6000bbls, requiring the
building of a kill mud plant between the relief well and blowout wellhead sites.
- For the final relief well kill operation a sodium silicate
plant was installed on the blowout wellhead site and a cement plant was set up on the