Argentina 1994

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.
Remedial Strategy: 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 special techniques.
  • 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 casing.
  • Intersection of a welbore in a salt formation had never been performed.
  • The producing formation fracture/kill pressure envelope was very small
Results:
  • Team concept for special services was successfully and efficiently utilized.
  • A direct openhole intersection was performed in the salt formation with special electromagnetic ranging techniques.
  • The blowout bottomhole location was within 2m of the predicted location.
  • 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 blowout.
  • 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 relief well.