About the Project
Polymeric liners are under investigation for their reliable use as permeation barriers to protect steel pipes used in the transport of fluids containing carbon dioxide and in some cases hydrocarbons. Swaged or rolled-in liners have been successfully used in non gaseous-produced water conveyancing applications for many years. The permeation of gases through the liner to the steel surface and the alteration of the mechanical properties of the polymeric liner as a result of fluid saturation can, in some circumstances, lead to liner collapse.
There is an increased demand to adopt liners in the transportation of carbon dioxide containing hydrocarbon mixtures at high temperature (~80°C) and high pressure (1,500 psi). This research aims to propose novel material combinations that could contribute to improving the collapse resistance of polymeric liners for such demanding environments.
Project Outline
The collapse of polymeric liners is generally caused by gases or vapours that permeate through the liner and expand when there is a pressure drop in the bore. In some cases, the critical collapse pressure will have been reduced by ageing or de-bonding of layers in the liner. The collapse of liners during rapid gas decompression events leads to concerns for their long-term deployment.
The research will investigate novel ideas for a non-metallic liner that will resist collapse. It is expected that the PhD will include novel approaches to research in the following aspects;
1. Development of finite element (FE) models that simulate the pressure differential at which the unaged and reinforced liners would collapse. Information obtained on the mechanical and physical properties of the liner material will be used, with allowances for the presence of thermal gradients where the bore temperature is ~80ºC. Novel materials, which may include polymeric layering or fibre or particulate reinforcement, will be considered, and the influence of fibre layup wind angle or weave on the resistance to collapse will be explored.
2. Mechanical property data for materials aged in hydrocarbon fluids will be used as inputs to predict the conditions for liner collapse. The material combinations will be evaluated before and after exposure to combinations of carbon dioxide and hydrocarbon high-pressure permeation facility.
3. New materials property data will be obtained using novel strain measurement methods with mechanical tests, including digital image correlation, computed X-ray tomography and digital volume correlation.
The student will be working between the Materials Department at the University of Oxford, where they will be registered for DPhil, and the NSIRC (National Structural Integrity Research Centre), and will be expected to spend ~50% of their time at each site over the 3.5 year duration of the project.
About Non-metallic Innovation centre
Aramco Technologies partnered with TWI Ltd and NSIRC to establish the multi-stakeholder Non-Metallic Innovation Centre (NIC). NIC will conduct a research programme that covers Technology Readiness Levels (TRL) 1-9 to develop ready to deploy non-metallic technologies for field applications.
About NSIRC
NSIRC is a state-of-the-art postgraduate engineering facility established and managed by structural integrity specialist TWI, working closely with, top UK and International Universities and a number of leading industrial partners. TWI has recently developed an advanced permeation and materials ageing facility that can be used to expose polymeric liner materials to complex mixtures containing carbon dioxide, hydrocarbons and hydrogen sulfide where appropriate.
About the University of Oxford, Department of Materials
The Department of Materials at Oxford offers an exciting environment in which to work for a DPhil degree. With, at the time of writing, 30 academic staff, 14 Senior Research Fellows, and around 200 research students and 82 postdoctoral research fellows, leading-edge research is carried out across a wide range of materials science, from atomic-scale characterization, through state-of-the-art materials modelling, to industrial-scale processing. The Department’s high rating for research is evidence of its international excellence in a wide range of materials research. In the UK Government’s most recent assessment of research excellence in UK universities, the 2014 REF, Oxford Materials was one of the top-rated materials departments in the country. 34.1 (FTE) academic staff, including several early career researchers (Royal Society URFs, RAEng Fellows and similar post-doctoral fellows), were submitted for assessment and 98% of our activity was judged to be in the highest categories of excellence [Grades 4* & 3*; respectively ‘world-leading’ (60%) and ‘internationally excellent’ (38%)]. 90% of our ’impact’ was judged to be ’world-leading’.
The academic supervisors at Oxford will be Prof. Hazel Assender and Prof. James Marrow.
Candidate Requirements
Candidates should have a relevant degree at 2.1 minimum, or an equivalent overseas degree in Mathematics, Material Science or Mechanical/Chemical Engineering.
Funding Notes
This 3.5 year project is funded by TWI and the academic partners and will provide full fees and maintenance for a student who has home fee status (this includes an EU student who has spent the previous three years (or more) in the UK undertaking undergraduate study). Candidates with EU fee status are eligible for a fees-only award, but would have to provide funding for their living costs from another source such as personal funds or a scholarship. The stipend will be at the EPSRC level (~£16k per year). Information on fee status can be found at http://www.ox.ac.uk/admissions/graduate/fees-and-funding/fees-and-other-charges.
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