Lifetime prediction of polymer-, elastomer and composite materials for sub sea application in arctic and deep water regions

The PolyLife project has explored the aging of polymeric materials in aggressive environments, similar to the environments they experience in the oil and gas exploration. During the project a range of equipment has been built in order to perform harsh environment exposure and perform measurement of diffusivity and solubility. Procedures to operate this equipment in a reliable and repeatable manner with complex thermodynamic test environment have been established. In addition methods and procedures to characterize various material properties in a reliable manner have been established. Also software modulus to efficiently analyse experimental data and use them in simulations have been developed, in particular with regards to permeation. PolyLife includes studies of the material types HNBR, PUR and PA11. For HNBR and PUR extensive studies has been conducted of how these materials age at high pressure and temperature in contact with water, organic fluids and gases similar to what is encountered in oil and gas installations at large depths. This includes identification of aging mechanisms, and methods for determination of lifetime in such environments. The knowledge generated by the PolyLife projects enables better interpretation of test results from accelerated life time tests and to design better test procedures. PA11 is used as a barrier in flexible risers (pipes). Water, especially at high temperature and low pH degrades PA by hydrolysis. PolyLife have demonstrated that methanol which is used for cleaning of risers accelerates hydrolysis. The PhD student in the project has developed a multi scale modelling approach that links models for molecular degradation to changes morphology and further on to bulk properties.

The production of oil and gas is happening under ever tougher conditions. The combination of high loads, high temperatures and corrosive environment (oil, chemicals) with the extreme requirements on reliability for offshore oil production in arctic and de ep water regions requires a proper choice of materials that can withstand the conditions. The main idea is to combine detailed experimental and theoretical analysis of material specific ageing processes on molecular and microstructural level into global models for life time prediction. The lifetime prediction will be based on advanced models for the sorption of the surrounding species into the material combined with kinetic models for degradation (e.g. chain scissoring, cross-linking etc.) and relations between the local molecular and morphological structure and mechanical properties. The experimental methods and models shall be used to qualify materials and components for given lifetimes under combined mechanical and environmental load conditions with a reduced requirement on testing time. The reliability of the final global models will be verified on selected polymer-, elastomer- and composite materials relevant for sub-sea installations. Solutions for sub sea processing and oil production in arctic a nd deep water regions must satisfy severe requirements on reliability, zero emissions, reduced need for maintenance and low weight. Use of polymers, elastomers and composite materials represent a technology gap for development of cost-efficient solutions that meet these requirements An important achievement of the project will be development of a national competence center in this area which will be attractive to the industry for efficient development and qualification of new commercial solutions. Also o f great importance for the industry is the development of a project guideline giving lifetime qualification methods that are simpler, less time consuming and more reliable than the methods used today.