PhD thesis on life extension of offshore structures

Ashish Aeran has defended his PhD in offshore technology at the University of Stavanger, with a thesis on life extension of ageing offshore structures.

More than 50 per cent of offshore installations on the Norwegian Continental Shelf, the United Kingdom Continental Shelf and the Gulf of Mexico Shelf are currently operating beyond their original life. The replacement of all these structures at once presents operational and technical challenges.

The use of infrastructure from an existing field is also sometimes a precondition for the development of a newer oil/gas field. Falling profit margins due to low oil prices, uneconomical small field discoveries and plenty of remaining oil reserves in existing fields are also encouraging operators to undertake more life extension studies.

It is important to use the existing infrastructure efficiently and to estimate its structural integrity and remaining service life.

Unreliable predictions

Material degradation caused by fatigue and corrosion is a major issue in assessment of existing ageing structures for life extension. Currently available assessment standards are good but can be further improved by adding more advanced theories/models.

Moreover, commonly used theories for fatigue life estimation have shortcomings and can lead to unreliable life predictions.

New framework

Aeran’s thesis proposes a conceptual framework for structural integrity assessment of ageing offshore structures, in order to estimate their remaining life more accurately.

The proposed framework not only overcomes the deficiencies in the currently available guidelines, but also includes recent research proposals available in the literature. Application of proposed framework is also shown to a jacket type oil platform.

The PhD thesis also proposes a new and accurate fatigue damage theory for more accurate estimation of remaining life than the commonly used theory. The proposed model can be easily applied by practising engineers using the available design standards. This is the main feature of this proposal unlike other such theories proposed in the past.

Model verification

The model has been verified with many experiments done on several materials. Also, the application of this model is shown to welded joints and jacket type oil platforms. Aeran has also improved multiaxial critical plane based fatigue theory by proposing new formulation of off-angle.

Aeran published his results in level two journals like International Journal of Fatigue and Marine Structures. He also presented and gave talks in several recognized international conferences like ISOPE, OMAE, COtech.

Publishing and teaching

During his PhD, Aeran also performed several department duties and was actively engaged with bachelor and master students. He was the main lecturer in Structural Mechanics II and Building Materials courses during the last 2 years.

Also, several Bachelor/Master theses were supervised as both main supervisor and co-supervisor during the last 3 years.

Aeran’s research project was supported by the Norwegian Ministry of Education and Research.

About the candidate

Ashish Aeran is 30 and from India. He has a Master's Degree in Structural Engineering from IIT Bombay and worked as Structural Engineer in Allseas Netherlands for four years. He defended his thesis called  Life Extension of Offshore Structures: A Conceptual Framework and Fatigue Damage Models at UiS on 1 October 2019.

Aeran is currently working as Integrity Management Senior Engineer in Wood Group Kenny Norge AS, Stavanger, Norway.

Photo of Ashish Aeran holding his thesis

Ashish Aeran