High Performance Seals Handle Rapid Gas Decompression In Extreme Environments

10th February 2015
Posted By : Jacqueline Regnier
High Performance Seals Handle Rapid Gas Decompression In Extreme Environments

Increasing oil extraction pressures and temperatures, aggressive chemicals and rapid gas decompression (RGD) in new, more difficult drilling sites are creating operating environments beyond the capabilities of most elastomers. DuPont Kalrez 0090 (K-312 “A” O-rings) perfluoroelastomer sealing parts, however, were developed to provide enhanced rapid gas decompression resistance in aggressive environments and have received the industry best “0000” rating in accordance with the NORSOK M-710 Rev. 2 standard and TOTAL GS EP PVV 142 specification.

These products, which are available from UK authorised distributor Dichtomatik Ltd, provide the optimum balance of chemical, heat and mechanical properties for different chemical and oil and gas sealing applications.

Their superior performance has also been substantiated by further tests conducted at the Centre Technique des Industries Mécaniques (CETIM) of France, in accordance with the TOTAL GS EP PVV 142, Rev. 5 procedure. CETIM found DuPont™ Kalrez® 0090 O-rings 113,67 x 5.33 mm also fulfil the acceptance criterion of the TOTAL General Specification GS EP EVV 142 Rev. 5. concerning O-rings used in the industrial valve industry. Kalrez® 0090 is the latest in a family of DuPont perfluoroelastomer parts for the oil and gas industry that includes Kalrez® Spectrum™ 6375 and Kalrez® Spectrum™ 7090.

DuPont is the only fully integrated perfluoroelastomer seal manufacturer, having total upstream and downstream expertise of monomer, polymer, compounding and finished product. Their Kalrez® 0090 products with enhanced RGD-resistant properties have established proven provenance in commercial service, and are currently in use at several major oil and gas companies. Many leading oil OEMs have also qualified Kalrez® 0090 seals for use in surface and downhole valves, data logging drilling tools, packers, completion tools and mechanical seals.

The key performance characteristics of Kalrez® 0090 seals include:

  • Exceptional resistance to rapid gas decompression, certified to highest 0000 rating in NORSOK M-710, Rev. 2 laboratory tests made with Kalrez® 0090 K-312_ “A_ O-rings
  • Withstands attack by over 1800 chemicals, and resists ageing in sour fluid, including multi-phase fluids containing high concentrations of hydrogen sulphide
  • Retains high levels of elasticity, recovery and extrusion resistance even after long-term exposure to temperatures as high as 250°C and as low as -40°C in high pressure environments.
  • Although Kalrez® 0090 parts are a high hardness perfluoroelastomer, it remains elastomeric with low compression set under most aggressive HPHT environments.

The spectre of shrinking global oil reserves and the search for new, more difficult sources such as deep water and shale is well documented. Many new exploration sites challenge the oil and gas industry with increasing extraction pressures and temperatures, and by the presence of aggressive chemicals such as ammonia, carbon dioxide, hydrogen sulphide (sour gas), methane, and steam — exacerbated by the phenomenon of rapid gas decompression (RGD).

Often referred to as HPHT (high pressure/high temperature) environments, these more aggressive drilling conditions pose a new set of problems for suppliers and equipment operators within the industry because they create operating environments beyond the capabilities of many commonly used equipment-sealing elastomers like hydrogenated nitrile rubber (HNBR) and fluoroelastomers (FKM).

Combinations of RGD, HPHT, and harsher chemicals can lead to premature seal failure, with the associated risks of costly financial, safety and environmental issues, and possibly resulting in plant premature shut downs. Because of this scenario the industry pressed for the establishment of a test standard to qualify non-metallic sealing materials. NORSOK standard M-710, Rev. 2, October 2001, developed by the Norwegian petroleum industry, has been widely adopted internationally as the benchmark of performance for any elastomer seal in critical oil and gas service. NORSOK certification for RGD is essential to qualifying performance of elastomer seals in HPHT and aggressive chemical environments, with the objective of reducing the risk of seal failure. TOTAL general specification GS EP PVV 142, Rev. 5, developed by TOTAL, is also widely accepted as an independent test of elastomer seal resistance to RGD in valve applications.

Perfluoroelastomer (FFKM) parts offer the highest temperature and chemical resistance of all elastomers, and are at the very top end of seal performance in the most aggressive chemical processing and oil and gas applications. “0000” is the highest rating in a NORSOK certification, and Kalrez® 0090 achieves and maintains this highest rating.

DuPont has more than 30 years experience serving the oil and gas industry with Kalrez® perfluoroelastomer parts. With oil extraction environments becoming more and more challenging for elastomer seals, DuPont embarked on a new formulation program in 2008 with the primary objective of developing a new compound with enhanced RGD resistance. Due to its fully integrated supply chain, DuPont was able to test hundreds of different formulations — not only using various curing chemistries and fillers but also alternative polymers — leading to the development of DuPont™ Kalrez® 0090 perfluoroelastomer parts. Before launch in 2010, Kalrez® 0090 parts were submitted for rigorous RGD resistance testing in October 2009 by the Materials Engineering Research Laboratory (MERL) in the UK, according to the NORSOK M-710 Rev. 2 standard.

The samples were exposed to a test gas of 90% methane and 10% carbon dioxide at 150 bar and 100°C, and a decompression rate of 20 bar/minute (see Table 1).

Table 1: Highest NORSOK and TOTAL ratings for DuPont™ Kalrez® 0090 seals tested.

 

NORSOK M-710 (Rev. 2) Certified

TOTAL GS EP PVV 142 (Rev. 5) Qualified

Rating

No internal cracks, holes, or blisters

No internal cracks, holes, or blisters

Test conditions

Gas

90/10 mol% CH4/CO2

80/20 mol% CH4/CO2

Temperature

100 °C (212 °F)

75 °C ±2 °C (167 °F± 3.6 °F)

Pressure gradient

15 MPa (~2200 psi)* to ambient

19 MPa (~2756 psi)* to ambient

Decompression rate

2 MPa/min

 

Cycling

10 cycles, one every 24 h

5 cycles

Sample details

Size

BS 1806 size 312

BS 1806 size 349

Section diameter

   

Groove fill

67%, nominal

73%, nominal

*Initial pressure maintained for at least 72 h prior to testing

 

 

 

 

 

 

 


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