Crossing the high pressure, high temperature ‘chasm’

Paul Boughton
Richard Dodd outlines the challenges of developing subsea solutions for the oil and gas thresholds of deep water, high pressure and high temperature.
The oil and gas industry is often criticised for not being at the cutting edge of technological advancement. But with the demise of ‘easy oil’ Operators and vendors are now leading the way in developing technologies to shape the world’s energy future.
The joint challenge faced by the industry is one of developing safe, environmentally and economically viable subsea solutions for the oil and gas thresholds of deep water, high pressure and high temperature (HPHT).
Easier said than done. The developments represent a step change in technology with a significant ‘chasm’ to cross. HPHT innovation isn’t just a linear extrapolation of the current technology. Sadly, up-sizing of the current technology just won’t work on its own.
The rewards for crossing the ‘chasm’ and successfully bringing such technologies on stream, however will have a revolutionary impact by enabling access, reducing risk and reducing costs, transforming the uneconomic to the economic. [Page Break]
What are the thresholds?
They have been termed as Extreme, defined as having pressures of up to 20,000 psi and/or temperatures of 350°F (176°C). Extreme HPHT wells are currently being drilled in the Gulf of Mexico region, on the shelf and in deep water, many of them exhibiting reservoir pressures and temperatures that approach 20,000 psi and 350°F. Some deep gas reservoirs, also on the Gulf of Mexico shelf have pressures and/or temperatures upwards of 30,000 psi and 450°F, propelling them into the Ultra HPHT designation.
And then you introduce the need to develop at Extreme depths – Gulf of Mexico’s Abyssal Plain and the Atlantic margin sea floor reaching in excess of 3000m for example. This ‘complication’ extends the challenge and the design rules of the past need to be rewritten in order to optimise new designs.
So what does the technology step change look like for valve design?
Material selection is crucial. The choice and availability of materials very much depends upon nominal bore size, the minimum and maximum temperatures and a third variable not yet introduced, the process conditions. On the metallurgical front, the design needs to recognise that, when high temperature liquid flows through a pipe or valve in cold water, the yield strength of the pipe is reduced — and along with it the pipe’s ability to withstand high pressures, both internal and external. And so new designs take into account: Higher strength steels, composite materials for lightness, strength and corrosion resistance, cost effective base material cladding, material stability, prediction of deflection and permanent set.
Sealing technology presents its own challenges. One of the most obvious is the current widespread use of elastomers and thermoplastics, which are, of course sensitive to high temperatures. These materials may be used separately or together for sealing systems or sealing elements and for other components within the system.
No fully qualified technology exists in the market today and so closing these HPHT technology gaps poses great challenges to the industry in the design, manufacture and testing/qualification of a whole new generation of subsea equipment, including critical valves.
Development of these technologies requires commitment to R&D investment regardless of the changes to energy prices and earnings. Experience from a vendor perspective indicates that it takes years, not months to carry out the development of new HPHT technologies. Therefore good relations and close collaboration between vendors and operators is needed now, to ensure that the potential benefits of HPHT, deep water systems for both the industry and global energy supply security are realised.

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Richard Dodd is Group Product and Engineering Director, BEL Valves Ltd, Newcastle upon Tyne, UK.

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