Getting a handle on corrosion

Intertek

Intertek’s Dr Kirsten Oliver asks whether it is possible to have a truly integrated approach to managing integrity of upstream oil and gas facilities?

Within the upstream and downstream oil and gas sectors, integrity management of the assets is concerned with getting fluid from the reservoir through the pipelines to process facilities and onward to refineries and into the distribution system. A break or failure in integrity in any of these stages interrupts production and supply in addition to causing the release of hydrocarbons and therefore the potential for significant health and safety and environmental implications. A vast number of factors influence the ‘integrity’ of an upstream oil and gas facility including materials of construction, internal and external environment, operations and process conditions, management issues, regulatory issues and cultural issues.

Corrosion

In the upstream oil and gas sector, the predominant degradation mechanism affecting metallic materials is corrosion, either external or internal. External corrosion is influenced by the surrounding area and this environment is typically consistent throughout the life of the facility. Items such as pipelines, process equipment and structures are typically protected from external corrosion by the application of coatings and/or cathodic protection systems.  Regular maintenance of these systems is required over the life of the asset.

Internal corrosion is influenced by the properties of the fluids contained within the pipeline or process facility, typically hydrocarbon, and is mitigated by the selection of materials, removal of corrosive species in the fluid (e.g. water, CO₂ and H₂S) and the injection of chemicals into the fluid streams (e.g. corrosion inhibitors and biocides). Unlike the external environment, the  property of the fluids and the operating conditions that directly effect the internal environment are unlikely to be constant throughout the asset life and therefore an ongoing programme of monitoring/inspection and assessing the probability of degradation and the consequence of a failure (from internal or external degradation) is key to understanding the condition of an asset.

All too often the potential for changing conditions is overlooked.  A facility will be designed at the project stage based on predicted field conditions and often optimised for peak production, and each part of the operations of the facility will collect data and go about their daily operations to enable fluid to be transferred thought-out their part of the process, but without appreciating how changes in production and conditions can affect long term integrity.

In the upstream environment, process and operational changes (e.g. reservoir acid stimulation, introduction of fluids from another reservoir, change in chemical provider, etc.) are often carried out but not effectively communicated throughout the organisation and result in integrity issues in pipelines and process facilities. To fully manage the integrity of an asset, data from a number of sources is required and this data must be transferred into information that can be interpreted to make knowledgeable decisions regarding future degradation of the pipelines, process equipment, piping and structures and therefore maintaining asset integrity.

The set up and implementation of an effective integrity management system is key to effective management of the facility. A large number of companies will offer ‘integrity management’ services, which are in fact a small piece of the overall jigsaw. Co-ordination of these integrity activities and interpretation of the vast amount of data that is generated is required to obtain a picture of ‘how is degradation occurring across my facility’? or ‘when am I going to get a failure’?

Review

Regular review of operational changes allows corrosion risk assessments to be updated, as well as allowing the implementation and future refinement of successful risk-based inspection programmes (potentially offering cost savings) and a thorough understanding of the condition of the asset to be demonstrated though a combination of inspection, monitoring, fluids sampling and data analysis. The data gathered can be housed in one central system or a number of integrated data management systems. 

‘One size does not fit all’, and the requirements for setting up and implementing an integrity management system will vary for different operators and asset types. Any system has to be based on an understanding of the asset itself as well as ensure that the overall goal is clearly understood.

Dr Kirsten Oliver is Upstream Production and Integrity Manager for Intertek based in the UAE. She has a bachelor’s degree and PhD in Materials Science and has worked as an operational corrosion engineer and has eight years experience of setting up and implementing integrity management systems for clients around the world. For more information go to www.intertek.com. Alternatively, telephone +971 6 538 7036 or email: kirsten.oliver@intertek.com.