TY - THES

T1 - Drillpipe Failure and its Prediction

AU - Stelzer, Claudia

N1 - embargoed until null

PY - 2007

Y1 - 2007

N2 - Drillpipes need to resist ever higher stresses as the drilling environments are getting more and more challenging, leading to possible failures that in the worst case of a pipe twist off can result in tremendous costs. These expenses can on the one hand be attributed to costly fishing jobs and on the other hand to potential side tracks including the costs of additional drilling time and the lost of equipment in hole. Although many investigations have been done previously on this topic and lots of prediction models to avoid failure can be found, the frequency of drillpipe failure still remains high. This is partly due to the insufficiency of these models as they do not take all failure influencing factors into account. Most of these models consider bending stress as the main source of fatigue and do not include other stresses or stress raisers leading to a shorter life of the components than predicted. Therefore the following work provides a discussion of the different types of failure, their prediction, the effect of drillpipe inspection and potential alternatives to steel. Furthermore, and most important, it explains the parameters that influence drillpipe failure and shows by means of flowcharts which of these factors are already able to be included into a prediction model and which need further investigations. Besides that, a workflow was developed how a prediction model could be build if all necessary information was available. Nevertheless, a lot of the unknown parameters cannot be measured with nowadays technology as they need to be known for each length increment of the drillstring. For developing such measuring devices, though, a positive cost-benefit ratio is necessary as well as the limited space found downhole needs to be considered when costructing the device.

AB - Drillpipes need to resist ever higher stresses as the drilling environments are getting more and more challenging, leading to possible failures that in the worst case of a pipe twist off can result in tremendous costs. These expenses can on the one hand be attributed to costly fishing jobs and on the other hand to potential side tracks including the costs of additional drilling time and the lost of equipment in hole. Although many investigations have been done previously on this topic and lots of prediction models to avoid failure can be found, the frequency of drillpipe failure still remains high. This is partly due to the insufficiency of these models as they do not take all failure influencing factors into account. Most of these models consider bending stress as the main source of fatigue and do not include other stresses or stress raisers leading to a shorter life of the components than predicted. Therefore the following work provides a discussion of the different types of failure, their prediction, the effect of drillpipe inspection and potential alternatives to steel. Furthermore, and most important, it explains the parameters that influence drillpipe failure and shows by means of flowcharts which of these factors are already able to be included into a prediction model and which need further investigations. Besides that, a workflow was developed how a prediction model could be build if all necessary information was available. Nevertheless, a lot of the unknown parameters cannot be measured with nowadays technology as they need to be known for each length increment of the drillstring. For developing such measuring devices, though, a positive cost-benefit ratio is necessary as well as the limited space found downhole needs to be considered when costructing the device.

KW - drillpipe failure prediction of drillpipe failure fatigue testing manufacturing process of drillpipe metallurgy of drillpipe drillpipe inspection alternative materials for drillpipe

KW - Defekt des Bohrgestänges

KW - Inspektion von Bohrgestänge

KW - Prognose eines Bohrstranggebrechens

KW - Herstellung von Bohrgestänge

KW - Metallurgie des Bohrgestänges

KW - Biegespannung

M3 - Master's Thesis

ER -