Drill Pipe Fatigue

Posted on 15 October 2012 by DouglasMiller

Drill pipe rotating in curved segments of the well-bore are exposed to extreme alternating stresses, axial loads, compression,   and bending.   The root cause of most drill pipe failure is fatigue cracks in the thread regions of the pipe caused by reverse bending, an effect by which drill pipe experiences alternating directional loads from their mean straight position, as seen in the diagram below.

The above picture is a diagram of a cantilever , a long projected beam fixed at one end, experiencing reverse bending forces.  In our case, the cantilever is supposed to be the drill pipe and the pin ends of the pipe  both the fixed and free ends of the cantilever. The fixed end serving simply as a reference point for a particular pipe and the underlying external forces.

Actively measuring shock, vibration, and weight on the drill bit,  and more broadly collecting LWD and MWD data provides comprehensive insight about well conditions throughout the drilling process. When coupled with preliminary string design and stress simulations, a very detailed view of the incurred stresses of the drill string can be inferred.

Now most of this data is used to plan for drill operations and actively adjust for well conditions during drilling. It can also however be used to provide an understanding of an individual pipes true fatigue throughout the drilling process. The data is already there and it is simply a matter of effectively bridging the relationship between pipe and well.

Enter ‘RFID’. This technology enables the ability to automatically identify drill pipe as it enters and leaves the wellbore. When overlaying this information with well LWD, MWD, and simulation data, the resulting fusion provides invaluable level of insight into each and every drill pipe used.  When relating these well conditions to pipe fatigue and subsequently associating it to each pipe, users are able to collect a historical track record about the stresses that each pipe has gone through at each well location. When analyzing this information and correlating trends in the data to actual inspection results, valuable fatigue indicators can be extrapolated.

These extrapolations  can be used to determine an individual pipes fatigue over time and accurately predict risks of reusing pipe at each subsequent well.  This information can also be used to refine inspection and maintenance procedures of drill pipe based on predictive maintenance techniques that far outweigh the industry status quo.

The maturity of RFID technology for drilling and pipe applications is phenomenal. As an early adopter of the older technology offerings and a re-adopter of the next-generation technologies, I am amazed how far the technology has come.

- Jointly Published in Collaboration with Oil & Gas RFID Solution Group



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