Summary
Drillpipe buckling affects the industry in many operational aspects, like
motor sliding problems, liner running, or weight transfer for downhole
equipment activation.
The authors believed the existing nonrotating buckling theories applied in
drilling software needed challenging by physically measuring buckling in a
realistic setup of well geometry and drillstring sizes and comparing the
results with the buckling theories.
The tests were performed in a 2020 m measured depth (MD) research well, with
a buildup and 60° tangent geometry (Aas 2008). Various configurations of a
tapered string with 5- and 3½-in. drillpipe as well as drill collars were used.
The tests were performed without torque or rotation being applied to the
drillstring.
A novel approach was using a high accuracy continuous gyro to measure the
string geometry changes (i.e., buckling) as function of axial load. Both
downhole and topside tension devices were applied to measure weight
transfer.
Several data sets recording buckling and weight transfer were obtained. The
gyro measurements of drillstring geometry changes clearly demonstrated the
onset and type of drillstring buckling. Weight transfer was measured under the
different buckling states and demonstrated that lockup occurs before reaching a
helically buckled state. This might alter operational practice regarding the
design of running strings.
The results have been compared with predictions from standard buckling
models. Necessary model enhancements are suggested.
The work has potential to improve buckling and weight-transfer models. The
potential outcome will be more accurate predictions for sinusoidal and helical
buckling and their effects on weight transfer. Ultimately, this will lead to
better decision making and understanding in drilling and completion
operations.
© 2009. Society of Petroleum Engineers
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History
- Original manuscript received:
30 May 2008
- Meeting paper published:
25 August 2008
- Revised manuscript received:
18 December 2008
- Manuscript approved:
30 December 2008
- Published online:
20 August 2009
- Version of record:
23 December 2009
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