By Dr Morris Roseman, Senior Scientist at Element Materials Technology
The economic gain from using materials that are lighter, stiffer, stronger and more corrosion resistant than carbon steel in the oil and gas industry is substantial, but the willingness of the industry to accept components fabricated from composites is directly related to the operational risks for that component. As a result, they have currently only made progress in lower risk components, such as gratings and hand-rails. However, with higher pressures and temperatures (HPHT), deeper water and deeper wells and more corrosive environments, composites are starting to be considered for application in more aggressive service.
A report issued by MERL in 2007 discussed some of the barriers facing the uptake of composites in the industry, and one barrier identified was a need for new standards for composites in these challenging applications.
For low risk applications it is easier to address regulatory concerns and to overcome the technical challenges. For higher risk applications, (such as HPHT composite flowlines, risers and liners, flexible pipe reinforcement and wirelines), the regulatory requirements are more stringent and the technical challenges are more difficult.
There is a significant lack of relevant performance information, especially in hostile offshore environments (including erosion, fatigue, wear and impact abuse, as well as fluid environments), which hinders the specification of composite materials.
There is a significant lack of relevant performance information, especially in hostile offshore environments, which hinders the specification of composite materials.
There are several standards and guidelines available for composites in different industries that are directly relevant.
ASTM is perhaps the most common source for test methods relating to the evaluation of material properties. Other standards, such as ISO 14692, ISO 24817 and API Specification 15HR, were written for oil and gas industry pipe work and offer a very thorough description of testing and evaluation of glass reinforced plastic (GRP) materials for pipe applications.
Others such as the ABS Guide for Certification of FRP Hydrocarbon Production Piping Systems, the DNV Offshore Standard DNV-OS-C501 Composite Components and the DNV Recommended Practice DNV-RP-F202 give very comprehensive descriptions on what testing can be done.
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However, the methods quoted are not necessarily relevant to the actual material geometry or do not describe the step-by-step procedures on how the appropriate tests should be carried out for qualification purposes.
Whilst basic material properties may be evaluated on the material itself using existing standards, the procedures were often not written for oil field composite materials and hence the standard will be used outside of its scope, bringing inconsistency in approaches. For example, ASTM D790M is a flexure test method developed for flat sheet, not for specimens cut from a liner or pipe sections that have a radius to them. NORSOK M-710 includes a rapid gas decompression (RGD) test method for elastomers. The conditions such as dwell times of the high pressure gas would not be suitable for composites which take much longer to saturate with the gas then do elastomers.
Element Hitchin (previously MERL) is currently leading a Joint Industry Project (JIP) to write a new international standard to enable qualification of composite components to be used in aggressive oil and gas operations. ♦
Dr Morris Roseman is a Senior Scientist at Element Materials Technology, Hitchin,UK (formally Materials Engineering Research Laboratory (MERL)). He has more than 15 years experience of working with composites, six of which being in the oil and gas sector.