||Problem: Well control
was lost during a trip out of the hole to run casing on a geothermal development well. The
reservoir was entered prematurely and the typical string of 9-5/8 casing had not
been set just above the reservoir. In 1-1/2 hours a 100 diameter crater swallowed
the rig substructure, leaving the derrick exposed above the monkey board. The well was
flowing 5000gpm of 350º water, which became steam and water upon exiting. The surface
location of the blowout had not been properly referenced, there were no surveys and no
drillstring was present in the hole, increasing the complexity of a successful
|Remedial Strategy: A relief well would be drilled and the blowout wellbore intersected within
10 TVD of the top of the reservoir. The relief well surface location must be fairly
close due to the geometry and no definitive target. The rig was positioned at 246
from the approximate location of the blowout wellhead. A 30 diameter uncertainty cone atop a 10 TVD target was specified. It was believed
that cold water injected near the top of the reservoir would stop the flow. High buildup
rates would be required to achieve the displacement to the blowout well and to provide for
an adequate proximity interval in the event that subsequent sidetrack(s) were necessary.
|Special Services: John
Wright Company (JWCO) was contracted to supervise the special services.
|Challenges: The project
was complicated by the following:
- A suitable surface location was severely limited by access,
blowout effluent runoff and geometric constraints.
- No suitable electromagnetic ranging target was present after
the drillstring was pulled from the hole and the exact location of the openhole target was
- A build and hole well design, with higher than normal build
up rate was required. Minimizing the probability of a direct intersection and also
reducing the TVD interval in which close proximity to the blowout would be maintained.
- No surveys existed for the target well.
- A 9-5/8" kill casing string must be set prior to
entering the specified 30' diameter uncertainty target.
- An accurate relief well trajectory must be present at the
casing point and an imminent intersection provided during the subsequent rotary drilling
- A 6-7º/100 BUR with a bent sub/motor configuration
and oriented with a steering tool were used to control the trajectory to the 9-5/8
- Intersection of the blowout wellbore was made with a rotary
BHA and loss of drilling fluids occurred at the predicted measured depth.
- An additional planned casing string was set to minimize the
potential well control problems resulting from supercharging and/or unstable water
- A 100bpm kill rate was expected, but a very low, 3-10bpm,
rate was required.
- John Wright and Jim Woodruff supervised as Eastman
Christensens RW Team.