California 1999

Problem:  After setting a 7" liner string and drilling into the top of the reservoir, a gain occurred which ultimately resulted in a surface blowout. The estimated formation pressure was in excess of 15000psi with a BHT of ~350 F with production rates estimated to be very high. A successful surface capping operation by Boots and Coots IWC was achieved, followed by a snubbing operation to fish onto the drillstring. After several unsuccessful surface kill attempts through the drillstring, it was decided to put the well on production and further assess intervention options. An underground blowout at ~2000-3000’ was identified after further assessment with hydraulic simulations and the presence of formation solids at surface. See Figure 1.
Remedial Strategy: The relief well option commenced at a 1500’ surface displacement location. Estimated intervention time was ~ 4-6 months to drill the build, drop build and hold profile well. The relief well was planned to intersect the blowout well on the highside. After setting a 7" casing string at ~120’ TVD above the intersection point, a short interval would be drilled to parallel the blowout for ~50-90’ After running a 5" scab liner to protect the wellbore and perforating between the two wells, a kill operation followed by a plugging operation would plug the well.  Backup intersection methods included milling and hydra-jet.
Special Services: John Wright Company (JWCO) was contracted to supervise the intersection and assist in the overall design for the relief well project. Halliburton Drilling Systems provided directional drilling supervision, MWD services and onsite coordination. B&C and HOWCO Supervised the Kill Operation. Vector Magnetics provided electromagnetic ranging services. Well Flow Dynamics provided simulation services for various kill scenarios including surface kill options.
Challenges:   The project was complicated by the following criteria:
  • The relief well was to intersect the blowout and remain parallel with ~28 Inc.
  • The relief well must achieve and maintain a close proximity of <0.5’ for 50-90’ on the high side of the blowout 7" liner string.
  • A perforating operation must penetrate the 5" scab liner and the heavy walled 7" Q-125, 41ppf blowout casing string and provide a very low pressure drop for the kill operation.
  • Formation dips and strikes ranged from near vertical to horizontal.
  • Bottomhole conditions were near directional equipment design limits at ~320 F.
  • High bottom hole pressure, inflow performance and possible underground cross flow complicated kill operation planning.
  • The Team Concept for special services was successfully and efficiently utilized.
  • The blowout well MWD surveys were found to be within specifications and the well was found to be within ~65’ of the calculated position.
  • A mud cooler/chiller was very successful in lowering the circulating temperature.
  • A highside intersection with ~50’ of <0.5’ proximity was achieved. See Figure 2.
  • After perforating, losses occurred and a cement plug was pumped to a height of ~6000’ TVD in the blowout well.
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