Safe Drilling in the Arctic:
Geosteering by Seismic While
Drilling (SSWD)
A new well positioning method evaluated for use in relief well
drilling
Presenter: Egil Tjåland, Norwegian University of Science and Technology (NTNU)
Authors: Kristoffer Evensen, Sigbjørn Sangesland, Ståle Emil Johansen, Børge Arntsen, Espen Birger
Raknes, Egil Tjåland
(NTNU)
Contents of presentation
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Description of method
Conventional relief well drilling
Benefits of SSWD in relief well drilling
Simulation results
Conclusion
Description of method
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Simulations performed with an elastic wave modeller showed that a thin object could be
identified on surface seismic data.
•
The upper parts of a relief well from 1989 was identified on real seismic data
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The well represents a reflective object for seismic waves creating prismatic, diffraction and
normal reflections.
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A well could be visualized during drilling by taking several seismic surveys and evaluate the
results compared to a reference seismic data set taken before drilling was initiated.
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Input data in the seismic model could be updated continuously with data from MWD/LWD and
ROP to increase the accuracy of the method.
•
SSWD use conventional equipment with a seismic survey vessel and/or ocean bottom seismic
receivers together with specialized processing software.
SSWD basic concept
4
SSWD concept
• Simulated 2D response from two wells
• Forward seismic modelling is used
• Repeated response from bottom of borehole
5
Conventional relief well drilling
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The blowing wellbore is intersected by utilizing
passive or active magnetic measurements
downhole in the relief well to home-in on the
target
•
All methods are dependent on steel in the target
wellbore to be able to intersect, hence the
intersection point might not be in the bottom of
the blowing well
•
Ranging can be performed with MWD tools or
wireline tools
•
Ranging methods have certain requirements on
the relief well trajectory and the execution of the
operation
•
Because of the ranging operation the relief well
will take longer time to drill than the blowing well
SSWD in relief well drilling
•
SSWD can potentially facilitate
intersection of a blowing wellbore
regardless of the presence of steel.
•
This enables intersection at the bottom of
the openhole section.
•
The added depth and wellbore length
increase the hydrostatic and frictional
pressure for a given relief well injection
rate.
•
This can reduce the required static kill
mud density and kill rig pump pressure,
increase pressure buildup and minimize
time used to displace rathole
Results of simulation
Parameter
Casing shoe
intersection
Bottom hole
intersection
Reduction
Static kill
mud
1728 kg/m3
(14.4 ppg)
1308 kg/m3
(10.9 ppg)
24%
Dynamic
kill rate
290 l/s
(110 bpm)
151 l/s
(57 bpm)
48%
Pump
pressure
508 – 1494 bar
(7370 – 21700
psi)
244 – 617 bar
(3540 – 8950
psi)
52-59%
Minimum
pump
power
19759 hhp
4942 hhp
75%
Maximum
Casing shoe
pressure
354 bar
(6200 psi)
278 bar
(4900 psi)
21.5%
Rat hole
Up to 76 m3
(480 bbl)
Down to 0 m3
100%
Conclusion
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The SSWD method will allow for direct and continuous positioning of the well path on the seismic
section or in the seismic cube.
•
A field test is needed to verify the concept and the accuracy.
•
SSWD may be used in combination with conventional ranging tools or as a standalone method to hit
a blowing well.
•
SSWD can potentially facilitate a direct intersection of a blowing well without the presence of steel.
•
A deeper intersection point is favorable during a killing operation.
Presentation based on SPE 167994-MS, 2014