The failure of oil well drillstrings due to torsional and longitudinal stresses
caused by stick-slip phenomena during the drilling operation causes great
expense to industry. Due to the complicated and harsh drilling environment,
modelling of the drillstring becomes an essential requirement in studies.
Currently, this is achieved by modelling the drillstring as a torsional lumped
model (which ignores the length of the drillstring) for real-time measurement
and control. In this thesis, a distributed-lumped model including the effects of
drillstring length was developed to represent the drillstring, and was used to
simulate stick-slip vibration. The model was developed with increasing levels of
detail and the resultant models were validated against typical measured signals
from the published literature.
The stick-slip model describes the friction model that exists between the cutting
tool and the rock. Based on theoretical analysis and mathematical formulation
an efficient and adaptable model was created which was then used in the
application of a method of species conserving genetic algorithm (SCGA) to
optimise the drilling parameters.
In conclusion, it was shown that the distributed-lumped model showed improved
detail in predicting the transient response and demonstrated the importance of
including the drillstring length. Predicting the response of different parameters
along the drillstring is now possible and this showed the significant effect of
modelling the drillcollar. The model was shown to better represent real system
and was therefore far more suited to use with real time measurements. / Iraqi Government, Ministry of Higher Education and Scientific Research.
| Identifer | oai:union.ndltd.org:BRADFORD/oai:bradscholars.brad.ac.uk:10454/16859 |
| Date | January 2018 |
| Creators | Alkaragoolee, Mohammed Y.A. |
| Contributors | Bryant, David, Li, Jian-Ping, Rahmanian, Nejat |
| Publisher | University of Bradford, Faculty of Engineering and Informatics |
| Source Sets | Bradford Scholars |
| Language | English |
| Detected Language | English |
| Type | Thesis, doctoral, PhD |
| Rights | <a rel="license" href="http://creativecommons.org/licenses/by-nc-nd/3.0/"><img alt="Creative Commons License" style="border-width:0" src="http://i.creativecommons.org/l/by-nc-nd/3.0/88x31.png" /></a><br />The University of Bradford theses are licenced under a <a rel="license" href="http://creativecommons.org/licenses/by-nc-nd/3.0/">Creative Commons Licence</a>. |
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