Metal-metal, elastomer and composite sealing

Understanding the strengths and limitations of various sealing systems enables Severn Subsea Technologies to offer a customized approach to tool development and performance.

In many cases the pressure and temperature requirements of today’s downhole tools are beyond the limitations of traditional elastomeric seals. This has led to the development of enhanced polymers such as perfluoroelastomers, and rapid gas decompression (RGD) resistant grades with enhanced resistance to H2S (hydrogen sulphide) combined with low compression set performance.

Understanding the chemical, temperature and RGD resistant properties of sealing materials and the ways in which changes to seal geometry can eliminate areas of weakness through the addition of back-up rings, and energized composite seals, to prevent extrusion in high pressure applications.

Hydraulic Intensifier

In some cases the seals need to be designed out altogether. One such example is the development of a hydraulic intensifier by Severn Subsea Technologies.

The hydraulic stainless steel pressure intensifier needed to supply 25,000psi for a high temperature, downhole application.  Hydraulic spool valves are commonly used to provide local pressure intensification downhole. These rely on either elastomer seals or tight tolerance, metal-to-metal seals to prevent leaks, and subsequent loss of pressure. Both sealing methods rely on the fluid having a minimum dynamic viscosity, however. Water is preferred downhole – it is plentiful and more environmentally friendly than hydraulic oil – but has a much lower viscosity. High downhole temperatures can further significantly reduce water viscosity greatly increasing the risk of leaks.

Severn Subsea Technologies developed an innovative sealing technique based on metal seated valves to provide leak-free, hydraulic spool valve intensification for water/glycol from 2,500psi to 25,000psi. The intensifier can also be used with mineral / synthetic based oils for a scale of intensifications from 2:1 to 10:1.

Designed for low / zero maintenance, the intensifier’s hydraulic switching and metal seated control valve avoids the use of heat sensitive elastomers, to provide leak-free performance for water and glycol mixtures up to 150°C.

 

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