illustration: shutterstock / Vismar UK
durable, next-generation coatings prolong subsea production capabilities
Hundreds and even thousands of feet beneath the ocean’s surface, subsea oil and gas production equipment clanks and whirs on the sea floor and below. There, it extracts raw crude oil and natural gas from wellheads, pumping these valuable resources to processing and storage operations on the surface — but not necessarily directly above via a riser. The supporting infrastructure may instead be 30 miles away, connected by an undersea pipeline. In either case, producers often use subsea tiebacks to connect the equipment on the ocean floor to fixed platforms and floating production storage and offloading (FPSO) vessels above.
Such tiebacks enable oil and gas producers to drill multiple wells in a single area and connect them to a central processing operation instead of enduring the much higher costs of deploying a platform for every drilled well. This efficiency saves producers a lot of money — but only when equipment lasts for the duration of the tapped reservoir, which may be 25 years or longer. Any equipment that needs to be pulled to the surface precipitately or replaced before the well is sealed cuts into the well’s return on investment. That includes equipment that needs to be pulled because the coatings applied to protect it from the highly corrosive undersea environment have deteriorated prematurely.
To help subsea tieback equipment maintain continuous operation throughout a well’s service life, producers need to specify the use of robust protective coating technologies that mitigate damage and corrosion. Doing so will help subsea tiebacks deliver the reliable performance required without needing premature maintenance, saving the bottom line.
Robust Coatings for Delicate Equipment
Oil and gas producers are now setting 30-plus years of service as a longevity target for their tapped fields, forcing equipment producers and coatings manufacturers to meet these extended targets with uninterrupted performance. That can be a tall order, as subsea equipment is often pressurized, faces high operating temperatures and endures transport and submersion in corrosive marine environments. In these operating conditions, coating systems must defend against all these corrosive threats whether or not cathodic protection is used. The stakes are the highest on pressurized equipment, where a coating failure could have catastrophic consequences.
Coatings specified to protect assets in the unforgiving offshore and subsea environments must meet established industry standards and requirements for safe and reliable performance of reservoirs and associated equipment. That includes guidelines governed by the International Organization for Standardization (ISO), the CSA Group, NORSOK and NACE International. Operators like Saudi Aramco, Shell and Chevron issue their own supplemental requirements, which coatings must also abide by.
Mitigating Operational and Transportation Stresses
Subsea equipment is tested over decades by a range of challenges and stresses — both below and above the surface. In addition to corrosion resistance, all coated equipment must also withstand impacts, abrasion and water permeation. Coatings also need to be resistant to the extreme high temperatures of extracted oil, as well as compatible with the various insulation systems installed over top of pipes and equipment.
To accommodate these needs for subsea oil and gas equipment, Sherwin-Williams Protective & Marine recommends a range of liquid coatings that meet various NORSOK guidelines. That includes meeting NORSOK M-501, Rev. 6, Category 7B standards for use on fully-immersed structural components that do not operate at high temperatures, using coatings such as Macropoxy® 646 fast cure epoxy and Macropoxy M922 epoxy glass flake. It also includes meeting NORSOK M-501, Rev. 6, Category 7C requirements for components that are fully immersed and operating at high temperatures. Sherwin-Williams coatings meeting that standard include Macropoxy M922 (accommodating temperatures up to 80°C/176°F), Dura-Sub™ C1330 epoxy (up to 180°C/356°F) and Dura-Sub C1230 epoxy (up to 200°C/392°F).
Producers must also remember the stresses that coatings may encounter before they’re placed into service. In the event of project delays, some equipment may be stored by the fabricator or remain dockside for weeks or months. Prolonged ultraviolet (UV) and atmospheric marine environment exposures can reduce the durability of the applied coatings, potentially taking valuable years off of their protective capabilities.
With this challenge in mind, producers may want to consider solutions that can effectively mitigate deterioration from UV exposure, including those tested to the NORSOK M-501, Rev. 6, Category 7A standard for splash zones on offshore installations and associated facilities. This specification measures the coating’s overall performance to ensure it offers optimal protection with minimal maintenance needs. Sherwin-Williams has tested Dura-Sub C1230 in accordance with this standard with exceptional results.
Compatibility Across Complicated Systems
Subsea production systems involve a web of various pipes, parts and components that control and channel the flow of oil or gas from a reservoir to a production facility. These installations often use components fabricated and assembled by different original equipment manufacturers (OEMs). Because each OEM may maintain different specifications for its components, the coatings used must be compatible across different standards and specs.
Equipment fabricators and assemblers must work efficiently to avoid delays and keep equipment moving from the shop to the production site to meet critical delivery schedules. They can help accelerate that timeline by using ultra-high-solids (UHS) liquid epoxies. Such epoxies allow fabricators to realize faster recoat windows and quicker curing times, so they can apply a second coat on a much faster timeline and move coated equipment sooner.
Additionally, UHS technology reduces the amount of solvent used and the amount of volatile organic compounds (VOCs) released during coating applications for a more environmentally friendly workspace.
In addition to the anti-corrosion coating system, insulation plays a big factor in the long-term production and life cycle of subsea equipment. Compatibility of the anti-corrosion coating system and the insulation that is applied on top is essential to long-term subsea production system performance. As a result, Sherwin-Williams is evaluating and testing new technologies to enhance the bond between the two materials.
Increased Durability for Ambitious Subsea Projects
As oil and gas producers look to new opportunities for growth and development, they must identify new areas for exploration while also making their existing operations more efficient. High-performance coatings support both of these goals by extending the service life of subsea tiebacks and other equipment, as well as providing the necessary performance enhancements to withstand increasing temperatures and external stresses.
The flexibility of HOT FBE-coated pipes enables reel-lay applications for efficient offshore field joint operations. photo: courtesy of the sherwin-williams company
HOT Pipeline Coatings Support Deeper Drilling
As oil and gas wells are drilled increasingly deeper, coatings technology must advance to handle the increased temperatures and pressures so the industry can avoid premature failures and threats to pipeline safety. Thankfully, newer coating solutions are enabling exploration activities to reach new depths. For example, high operating temperature (HOT) fusion-bonded epoxy (FBE) coatings from the Sherwin-Williams Protective & Marine Dura-Sub C family of coatings can now accommodate operating temperatures up to 180°C (356°F), with room to handle even more extreme temperatures in the future.
Today’s HOT FBE coatings feature higher glass transition temperature (Tg) values, allowing pipeline operators to specify coatings with Tg values that are at least 5°C (9°F) greater than the highest operational temperature of the pipe. New HOT FBE coatings also maintain a high degree of flexibility, ensuring pipes can be joined onshore and reel-laid, saving time and money when compared with welding and coating every 12 meters on a lay barge. High Tg values also provide better damage resistance and a stronger barrier against water and corrosion-causing particles.
— Dr. Jeffrey David Rogozinski, Global Product Director – Fusion-Bonded Epoxy/Pipe, Sherwin-Williams Protective & Marine
Claims or positions expressed by sponsoring authors do not necessarily reflect the views of TPC, PaintSquare or its editors.