Oil & Gas

Offshore oil and gas seal standards

Offshore oil and gas facilities are well known for their extremely harsh environments. Choosing the correct seal can reduce both planned and unplanned maintenance, extend seal life and as a result, optimise long term production costs.

In the Oil and Gas industry it is extremely important to ensure compliance with industry standards and new sealing materials as they are introduced into the market. By working with a supplier who can offer compliant materials, oil and gas organisations can receive greater processing performance while reducing the number of suppliers needed to maintain fresh supplies.

Oilfield environments and applications require a wide sealing range

There are many factors which lead to the requirement for an increasing number of sealing materials in offshore oil and gas applications. Standard formulations often cannot cope with the demanding sealing environments and applications of the industry. Pressures can be very high, temperatures extreme, and the mix of contact and system media can be particularly destructive.

Some of the extreme media that must be handled includes:

• Hydrochloric, acetic and formic acids, which are used during acidizing and hydraulic fracturing operations.
• Aromatic hydrocarbons such as benzene, toluene and xylene.
• Aliphatic hydrocarbons and carbon dioxide.
• Other chemicals to prevent corrosion of the piping, casing and associated equipment.

In addition to handling severe chemicals, seal development must also consider the effect of drilling mud, which is very abrasive.  Many types of material exist which are based on diesel oils, mineral oils, esters or silicates. Experience has highlighted that one seal material will not be suitable for all applications. As a result of this, a broad range of compounds is essential to ensure that different operating conditions can be met in terms of media resistance, life expectation, and friction / wear requirements.

The main factor to reducing downtime is understanding how seals react over time when exposed to severe working conditions.  Extending long term seal life is one main priority, but the most important factor is safety.

STANDARDS BOOST CONFIDENCE IN SEAL SAFETY AND PERFORMANCE

As sealing requirements constantly change and become more challenging, new sealing compounds and technologies are being developed to meet these increasingly demanding conditions. To ensure safety controls must be in place for these new formulations, and this has led governing bodies to introduce standards which offer the Oil and Gas industry unbiased, accurate ways to assess performance. Certification to these standards gives an additional level of confidence that specially engineered seals will meet the toughest requirements.

NORSOK

The overview of many oilfield service companies’ regarding the various governing bodies serving the oil and gas industry suggest that NORSOK is the most popular and widely recognised. NORSOK has been used since 2001 and their M-710 specification underlines the need for oilfield equipment manufacturers to ensure higher levels of quality and compatibility of non-metallic seals used in oilfield equipment operating anywhere in the world.

The certifications for NORSOK M-710 have three components to them:

• Annex A specifies procedures for conducting accelerated ageing tests in an autoclave on constrained O-ring samples.
• Annex B comprises the fluid compatibility recommendations for the seals.
• Annex C concentrates on the ageing of thermoplastics and addresses explosive decompression resistance. Even though the rapid gas decompression (RGD) resistance testing generated by reputable oil companies is highly regarded, the independent qualification generally chosen for equipment suppliers and fluid sealing specialists is NORSOK M-710 Annex B.

NORSOK M-710 qualification of non-metallic sealing materials and manufacturers (Rev. 2, Oct. 2001) requires individual seal materials to be rigorously tested based on Explosive Decompression Resistance (ED).  This can occur when gas or gas mixtures which come into contact with elastomer surfaces can be absorbed into the elastomer under pressure. At high pressures, absorbed gas is in a compressed state and when the systems external pressure is reduced, or falls quickly, the compressed gas rapidly expands within the elastomer. This can lead to cracking within the body of the elastomer which multiplies internally causing voids, cracks and blisters to appear on the elastomer surface. This effectively reduces seal function.

Other tests conducted relate to sour and sweet gas ageing, compression set tests, and material property tests. There are defined requirements for critical non-metallic (polymer) sealing, seat and backup materials for permanent use in subsea applications. These include well completion, trees, control systems, wellheads, valves and also topside valves in critical gas systems.   There are constant new revisions evolving in accreditation requirements today that have updated previous specifications, for example the updates NORSOK standard certification to encompass all individual components within an assembly rather than just the complete assembly.

In addition to NORSOK, standards from NACE (National Association Corrosion Engineers) and the American Petroleum Institute (API) are also significant.

NACE

NACE is the standards-writing organisation accredited by the American National Standards Institute (ANSI) that recommends three categories of NACE standards: Standard Practices, Material Requirements and Test Methods.

NACE discovered that there have been many failures caused by permanent compression set of O-rings and cracked energizing springs and therefore felt it necessary for specific certification for seal suppliers.  The standards organisation has recently developed test parameters aimed at defining materials for elastomeric seals that can avoid damage during decompression in high-pressure gas duty. There are four such protocols set for practical seal selection in this type of aggressive oilfield service.

AMERICAN PETROLEUM INSTITUTE (API)

API’s mission is to promote safety across the industry globally and to influence public policy in support of a strong oil and natural gas industry

API maintains nearly 700 standards and recommended practices covering all segments of the oil and gas industry which promote the use of safe, interchangeable equipment and proven and sound engineering practices. These cover such diverse categories such as Sub-surface safety equipment to environmental protection.

API standards support proven sound engineering and operating practices and safe, interchangeable equipment and materials.

In addition to NORSOK, NACE and API standards, there are also those of major Oil companies. The governing bodies have worked closely with seal suppliers and played an important role in releasing new and revised standards on how sealing materials should act and work in actual applications.

MEETING STANDARDS IS FUNDAMENTAL TO IMPROVEMENT OF OFFSHORE OPERATIONS

Achieving compliance to all relevant standards is time consuming and expensive and not all suppliers have the resources to obtain the required certification. It is important that suppliers have the appropriate certification and the wider the range of certified sealing materials and solutions offered. This reduces the number of suppliers an operator needs to fulfil specifications for varying oilfield sealing requirements. Choosing the correct seal supplier can be critical in ensuring safety, minimising down time and lowering overall cost of offshore oil and gas operations.

This is supported by reports from Industry analysts who state that it is important to partner with a supplier who has been committed to providing solutions for the upstream and downstream oil and gas industries. They also state that it is important that suppliers invest in research and development, having facilities and analytical laboratories equipped with up to date equipment and technology.

It is important to choose a supplier who can provide a wide range of certified sealing materials and solutions which are compliant to the most important sealing standards. A reputable supplier should have a selection of fully approved NORSOK M-710 materials in a range of types. This is an important consideration for the customer as these materials will have been pre-tested for temperatures and fluids by an independent third party.

Eastern Seals offer a broad range of sealing materials to meet the varying industry standards. We supply a large selection of fully approved NORSOK M-710 materials in a variety of types.

Our high performance seals for Oil and Gas applications offer market leading chemical resistance to sour gas and other fluids, in combination with rapid gas decompression (RGD) resistance.

Recommended materials include Perfluoroelastomers (FFKM), Fluoroelastomers (FKM / Viton^®), HNBR seals and Aflas^®, with materials independently tested and certified to the Norsok M-710 specification.

We can help customers optimise their production by helping select the correct seal material to be specified for specific oilfield conditions. Our expert advice can help extend seal life, reduce planned and unplanned maintenance, and ultimately reduce the total cost of processing for the customer.

Contact Eastern Seals’ Technical team to discuss the best sealing solution for your process. Call us on +44 (0) 1670 840529 or send us an email to sales@easternseals.co.uk.