Syria 1995

Problem: During the final angle building phase of this horizontal well, drilling fluids returns were lost. After several unsuccessful attempts of pumping and spotting diesel and LCM pills to halt the fluid losses, well control was lost. The well pressure exceeded the rupture limits of the last casing string and a broach to surface occurred from the shoe of the surface string. The BOP stack remained intact with the drillstring suspended 276m off bottom of a 1563m openhole section. The well was flowing oil and gas at extremely high rates.
Remedial Strategy: After two unsuccessful attempts to kill the well from surface through the drillpipe, a relief well intervention project was planned. The well was flowing up the annulus at a very high rate and hydraulic simulations showed that kill rates in excess of 75bpm with 15ppg kill fluids were required. Further investigation concluded that two relief wells, intersecting the blowout well above the bit, would allow the necessary high kill rates and an effective use of reactive plugging agents/mixtures. Although two direct intersecting relief wells were required from the hydraulic calculations, the blowout severity, the kill program complexity and the intervention time mandated that a third relief well could provide reservoir flooding capabilities and backup options.
Special Services: Wright Boots & Coots was contracted to supervise the special services for this very large blowout intervention project. This included technical planning services and on-site supervision of well blowout control and engineering, hydraulic kill simulations, directional drilling, well surveying, casing detection, kill fluids plant design and operation, pumping plant design and operation, cementing, kill program design and engineering and reactive fluids design and implementation. Vector Magnetics provided electromagnetic ranging services and Ely & Associates provided pumping and reactive plugging material expertise. Boots & Coots provided well blowout control services for surface operations and kill fluid engineering was supplied by OGS. Well kill simulations and engineering services were provided by Well Flow Dynamics. All special services groups worked together with Wright Boots & Coots to create a single team.
Challenges: The project was complicated by the following:
  • A multiple relief well intersection into a blowing wellbore had never been performed in the industry.
  • Intersection must be prior to the build up section having an 8 to 12/30m BUR. The presence of oil in the target annulus and three converging wells required special planning and electromagnetic ranging detection techniques.
  • High flow rates required a kill program having two intersections, spaced at 40m TVD apart, for efficient reactive plug pumping and ranging.
  • Local supply yards and services were very limited and could not provide the required quantities and types of kill fluid materials and kill plant equipment.
  • All operations were integral to the ability to place the two relief wells within the specified TVD interval and at the same approximate time.
Results:
  • Team concept for special services was successfully and efficiently utilized.
  • Electromagnetic ranging was effective in locating the blowout wellbore.
  • Two wellbores intersected the blowout at the specified TVD interval and within three days of each other.
  • A rate gyro was instrumental in minimizing borehole position uncertainties.
  • A 120 bpm total kill rate for 12 minutes dynamically killed the blowout.
  • Cement plugging with 2440bbls commenced after achieving a static kill.