Several parameters can influence materials selection such as tax regime cost of maintenance experience and traditions. The main differences in materials selection between the North Sea and other regions will be presented. Materials selection is addressed differently and the degree of involvement from the operator varies. Other operators leave all materials selection activities totally up to the engineering contractors and fabricators. ISO is the only ISO standard addressing materials selection in the upstream oil and gas industry. The expert group that developed the standard consisted of representatives from most of the major operators.
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This would create a more predictable situation for suppliers, manufacturers and contractors. Deadline to provide comments to the national standardisation bodies may typically be some weeks prior to the ISO deadline. This includes all equipment from and including the well head, to and including pipeline for stabilized products.
Downhole components are excluded. CO 2 corrosion can lead to both localised and general corrosion. The most important parameters for CO 2 corrosion are temperature, partial pressure of CO 2 , pH, content of organic acids and flow conditions. Several models for prediction of CO 2 corrosion on carbon steel are available, and the model to be used should be agreed with the end user. The lower temperature limits are mostly based on laboratory experiments, but there are very few field cases that show cracking at these conditions.
Many operators have used higher critical temperature limits that are represented by the higher temperature value in table 1. Extensive field experience over many years has shown that very few SCC failures have occurred on uncoated pipes when these higher temperature limits have been used. The produced water systems can be complex, and oxygen contamination may occur in some circumstances as described in 4. Seawater ingress from drain systems has also been experienced. Some produced water systems can support bacterial activity, especially if the sulphate concentration is high due to break though of seawater from previous seawater injection.
In such circumstances, microbial corrosion is the main integrity threat for carbon steel. Oxygen ingress and MIC will strongly influence the effectiveness of the chemical inhibition.
The typical materials for produced water systems are given in Table 4.
51313-02268-Materials Selection for Oil and Gas Production Systems—Use of ISO 21457