Pipeline corrosion: The Shell viewpoint

The March/April edition of Process Engineering magazine includes a feature on pipeline corrosion, which covers the impact of this problem on the process industry and how operators are dealing with this issue. In this related Q&A article, Sergio Kapusta, chief scientist regional manager, Upstream Materials and Integrity, Shell Global Solutions US Inc. offers an insight into Shell’s viewpoint on the subject:

Q: Corrosion costs have been described as a major untapped area for economic gains. How significant is this as an issue at Shell and what is the potential for further improvement?

A: Corrosion costs US industry more than $150 billion per year, according to a survey carried out by NACE (The Corrosion Society). The oil industry’s annual corrosion costs are estimated in the same survey at about $15 billion. Naturally, there is a large economic incentive to mitigate the impact of corrosion on our business. Our experience is that expenditures in corrosion control have a large multiplier in saving the costs associated with corrosion damage. In corrosion, as in other areas, an ounce of prevention is worth more than a pound in potential losses. Shell is a leader in applying advanced management and technical solutions to reduce the risks associated with corrosion.

Q: How does Shell measure its performance in terms of corrosion prevention?

A: There are several ways in which we measure our performance. We comply with all local and national regulations related to corrosion control. For instance, we monitor the cathodic protection of our pipelines, we comply with construction and maintenance codes, we keep a record of leaks, etc.

This is a minimum level of performance. But we have also implemented additional forward looking performance indicators that give advance warning of potential problems. Some examples of these performance indicators are:

(1) Training and skills of the people involved in corrosion control and maintenance activities; (2) Quality control of all corrosion control chemicals; (3) Corrosion monitoring coupons and probes to determine actual corrosion rates; (4) Periodic assessment of corrosion risks using established methodologies, such as risk based inspection; (5) internal inspection of pipelines using instrumented tools (intelligent pigs).

This is a simply indicative review of our performance measurements, rather that an exhaustive list.

Q: What proactive steps/procedures is Shell implementing to minimise pipeline corrosion and have there been any recent initiative at the company in this area?

A: We have undertaken an intensive and thorough programme to assess the corrosion risk of our pipeline systems. This assessment is based on US Federal Guidelines and is complemented with our own experience as an operator of a very large pipeline system.

The programme includes both a review of the pipeline corrosive conditions, the consequence of leaks, and the condition of the lines from direct measurements such as coupons or intelligent pig inspection.

For pipelines that operate with fluids that are considered corrosive, such as those transporting crude oil that contains water, we use a combination of techniques to mitigate this corrosion, such as injection of corrosion inhibitors, biocides, routine pigging to clean deposits, monitoring of corrosion rates, etc.

Q: Which emerging technologies does Shell see as significant in this area in terms of: pipe construction, materials and coatings; corrosion inhibitors and corrosion monitoring?

A: I will start with corrosion inhibitors. More than 30 years ago Shell, working with chemical suppliers and partners, championed the development and application of highly effective corrosion inhibitors for very corrosive conditions.

The technology that we developed for the super sour (high H2S content) fields in Mississippi and Canada is still in use today, and has proven very successful in preventing corrosion related failures in these operations.

From this experience we learned that we could probably find inhibitors to prevent corrosion under most conditions. The challenge is to find chemicals which are more environmentally friendly to meet the ever more stringent offshore regulations. The process of developing these enviromentally friendlier inhibitors requires close cooperation between users, suppliers, and regulators.

We have achieved some successes particularly in the US, Europe, and the Middle East, but more still needs to be done, particularly in areas of the world where environmental regulations affecting corrosion control chemicals are unclear or non-existent.

We are continuously striving to develop, together with our partners in other industries, new materials that offer corrosion resistance, better mechanical properties, or lower costs. In these areas Shell has also been a pioneer, for instance in the development of high strength H2S resistant tubulars, and of corrosion resistant alloys.

Some of the challenges now are related to new materials and design practices for constructing large diameter (greater than 30-inches), long (up to 200 km), subsea pipelines. Pipeline materials, installation and corrosion protection costs can become a significant factor in determining the viability and sustainability of some of these new projects.

We look at bimetallic pipe (a carbon steel pipeline with an inner liner of a corrosion resistant material) as one solution to this problem; finding innovative corrosion control methods, such as stabilizing the formation of natural protective scales, is another potential solution.

We typically look at several options for reducing corrosion risks to manageable levels, since the best solution is often a combination of materials selection, application of corrosion control methods, monitoring, inspection, and risk assessment. Of course, lowering costs is a factor.

But at Shell we take a “safety first” approach, which gives us a clear guidance for prioritization of our selection.

For many years we have had an intensive program to evaluate the performance of protective coatings. In fact, many of the testing protocols that are used by NACE (The Corrosion Society) were originally developed in the Shell Laboratory. We don’t develop coatings, but we encourage the suppliers to come up with new technology to improve the performance of existing products. We also continue our program to qualify coatings for Shell applications.

Q Control & automation suppliers are now pushing technologies for increasing the monitoring of corrosion and linking this with process variables to help maximise productivity and minimise corrosion damage. How interesting are these technologies and are there any current applications/projects at Shell?

A: We have been working on similar technologies to monitor process variables and establish correlations with corrosion rates for the past 5 years. We have initiated pilot programs to implement these technologies at some of our refinery units. This same technology is also being tested for use in our oil and gas production operations as part of a more generic “smart fields” approach. We are very interested in what other companies are doing in this area, and we have in fact established contacts with several of them to test their products.

Q: Are there any other technical developments in the area of corrosion prevention that our readers should be aware of?

The two most important aspects of corrosion prevention are planning and execution. We think that planning involves a good assessment of the potential corrosion problems and of the available solutions. This step requires qualified staff, who are very skillful and understand the intricacies and nuances of corrosion.