“Historically, pipelines were designed for 20 to 25 years, following which time they underwent a ‘life extension’,” he said. “These days the design life is set at 50 years for some projects.”
DWA has pioneered many new methods for offshore cathodic protection life extension over the years and has learned many lessons. The ACA works with companies such as DWA and CCE, along with academia, to research all aspects of corrosion in order to provide an extensive knowledge base that supports best practice in corrosion management, thus ensuring all impacts of corrosion are responsibly managed, the environment is protected, public safety enhanced and economies improved.
Around the world, there are thousands of kilometres of pipelines—on and offshore—connecting drilling rigs and production platforms to wellheads and other facilities. This infrastructure represents billions of dollars of investment by companies over many years. Corrosive fluids flow inside the pipelines and on the outside they are exposed to a range of harsh physical, climatic and chemical effects that can cause corrosion and degradation.
Deep ocean, coastal and onshore environments present very different operating conditions for infrastructure. In tropical regions, surface water might be as warm as 20°C and at one atmosphere of pressure, compared to the deep ocean where the temperature at depths of thousands of metres drops to around 2°C and the pressure increases to more than 1700 psi. (At sea level, the atmospheric pressure is approximately 14 psi.)
Oil from deep wells can be as hot as 176°C. As the hot oil comes up from the well it travels through the much colder pipeline and the fluid in the pipe can quickly cool down. At approximately 21°C, the water and gas mixtures in the pipe can form gas hydrates or paraffins. If the build-up of paraffins is too great, it can ultimately block the pipeline. Such blockages can be extremely costly to clear and, if a pipeline ruptures, can cause catastrophic damage to equipment and the environment. In order to prevent catastrophic failures, there is ongoing research in to new insulation materials and their application procedures. “Unfortunately, some of these new materials have not been in use for very long and thus their long term performance is unpredictable,” Grapiglia stated.
Maintenance and corrosion prevention come together to ensure Subsea Flow Assurance. These are the processes that ensure subsea pipelines and equipment maintain oil flow. “Appropriate insulating materials must be applied to infrastructure in order to maintain or at least slow down the heat loss from the fluids being transported,” Flanery said. Manufacturers of surface coatings have worked to develop suitable materials to handle the extreme conditions of deep water activities.