Helical Buckling Limit

Dear community,

We would value your opinions, thoughts and comments with regards to defining buckling limits for drill string design.

In the process of modelling T&D for our ERD wells, we have found that different software's are calculating helical buckling limits in different ways giving different results.

Whilst the equation for the critical sinusoidal buckling load appears to be the same (difference in consideration of inclination change only or both inclination and azimuth change), the calculated critical helical buckling loads differ due to a constant which varies depending on the software and integral algorithms used.

For example, our T&D modelling software provides two helical buckling limits, rotating and non-rotating. Whereas another software states that rotation has no effect on helical buckling and therefore shows a single helical buckling limit. A literature study did not provide any conclusive information to evaluate the different software.

The outcome from a third party simulation shows that helical buckling is considered critical whilst running the production liner in an ERD well, whilst our in-house modelling shows some safety margin left before reaching non-rotating helical buckling.

As we endeavour to have a consistent approach during planning and operations, as well as to increase our in-house knowledge for the increasingly challenging wells we plan in the future, I’m interested to learn how other operators and service providers are dealing with this challenge.

Using the sinusoidal buckling limit as a limit does not work for us, so my questions is, “how does your organization define the limit for helical buckling?”

Thanks

Uwe

10 Answer(s)

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