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Stability of confined slender structures – reducing freedom to increase strength

PhD defence, Wednesday, 1 December 2021. Johannes Liljenhjerte.

2021.12.01 | Mette Nielsen

Johannes Liljenhjerte

Unstabilized CT in cylindrical confinement along with an example of using periodic support as a stabilizing initiative.

During his PhD studies, Johannes Liljenhjerte researched the stability of axially compressed tubings in cylindrical confinement. Coiled tubings (CT) are utilized in well service operations for transporting various tools and fluids into the wellbore. Some wellbores have a long horizontal section, in which friction build up, causing the CT to buckle and locking up, making it impossible to reach any further. Johannes Liljenhjerte investigated where instabilities occur during CT operations, how a stabilizing initiative can extend reach, and potential stabilizing initiatives.

Research findings contribute to the understanding of the buckling phenomena for confined slender structures, and covers the structural aspects in the development of a whole new type of extended reach technologies.

The PhD study was completed at the Department of Biological and Chemical Engineering, Faculty of Technical Sciences, Aarhus University.

This summary was prepared by the PhD student.

Time: Wednesday, 1 December 2021 at 13:00
Place: Building 3210, room 04.121, Navitas, Inge Lehmanns Gade 10, 8000 Aarhus C

Title of PhD thesis: Extending Coiled Tubing Reach using Stabilizing Initiatives
Contact information: Johannes Liljenhjerte, e-mail: jl@bce.au.dk, tel.: +45 61 78 22 42.

Members of the assessment committee:
Professor Erik Lund, Department of Materials and Production, Aalborg University, Denmark
Professor Sebastian Thöns, Division of Structural Engineering, Lund University, Sweden
Associate Professor Menglin Chen (chairman), Department of Biological and Chemical Engineering, Aarhus University

Main supervisor:
Associate Professor Jens Vinge Nygaard, Department of Biological and Chemical Engineering, Aarhus University, Denmark

Language: The PhD dissertation will be defended in English

The defence is public.
The PhD thesis is available for reading at the Graduate School of Technical Sciences/GSTS, Katrinebjergvej 89F, building 5132, 8200 Aarhus N.

PhD defence
17427 / i43