The first flexible pipes were used in the offshore oil and gas industry in 1972. These early models were built and applied as a ‘kill and choke’ line and formed with a bonded type of material, usually vulcanised rubber and armouring.
Since then, the demands for this technology have steadily grown and diversified. Today, they are found in every major production basin worldwide and are used for everything from risers, flowlines, fluid transfer lines and jumpers, all designed to keep production flowing efficiently.
The development of flexible pipe technology has accelerated in recent years. Of course, the clear trend across the oil and gas industry has been operators looking for operational efficiencies wherever possible. Marginal gains in operational efficiency have become the order of the day.
However, implementing this is trickier than it may sound given that many new fields are located in some of the most challenging environments the industry has ever had to contend with. Deeper water, higher temperatures, higher pressure, ageing infrastructure and complex chemistry, all stack up to create ever more intense conditions for flexible pipe to withstand. In short, more and more fields are pushing the boundaries of existing technology. So, is it feasible to expect even more from flexible pipe technology?
Why go flexible?
Every project, at some point, has to make a choice between rigid or flexible pipeline. The simplicity of the rigid carbon steel, welded together on a barge or at a spoolbase and then laid on the seabed, has been overshadowed in some cases by the more sophisticated mechanism of a flexible pipe – where installation and operation are simplified by design, before the pipes are constructed and shipped.
The choice of subsea pipeline technology is often based on local conditions, technical requirements, installation vessel availability, operator preferences and cost efficiency.
The ability to apply flexible pipe in the most challenging environments is a significant part of its appeal. High performance in water depths beyond 2500 m, high pressure reaching beyond 10 000 psi, and high temperatures above 130°C, as well as the ability to withstand large vessel motions in adverse weather conditions, point towards why flexible pipelines have increased in popularity in recent times.
For floating production, flexible risers are often the only option that solves the geometric constraints of water depth, fluid pressure, vessel motions due to environmental loading and the consequent fatigue degradation of steel.
Of course, these operating conditions are set against their own challenging backdrop. Even five years after the downturn hit, almost every operator continues to encourage supplier-led solutions to reduce cost and standardise and simplify subsea system installation and operation.
Deeper, higher, hotter
Today, frontier markets such as Latin America, Brazil in particular, and West Africa, epitomise the need for enhanced flexible pipe technology. Operations here typically involve negotiating extremely deep waters, high pressures and very high temperatures, with production to a FPSO. It is because of this that Brazilian projects have often been at the cutting edge of technology developments.
Increased project activity in such complex environments has led to incremental improvement in product capabilities. To date, flexible pipeline has been manufactured from a combination of materials, including steel pressure armour. This gives the designers high stiffness to provide strength, geometric compliance to provide flexibility and incorporates polymer sealing layers with low stiffness for increased fluid integrity. With the addition of further strength bearing armour layers, this traditional structure is what gives the product its intrinsic properties, however new operating and economic environments have called for more – deeper, hotter, faster, larger, cheaper….
Therefore Baker Hughes have developed new designs for flexible pipe, moving from purely metallic strength to a carbon fibre composite pressure armour layer, marking a major step-change in the industry.
By developing a composite pressure armour layer, the weight of the riser is reduced by up to 30%, making it easier and less expensive, to transport and install - using smaller vessels or reduced vessel time, less ancillaries and giving the operator a simpler riser configuration to manage. This hybrid composite flexible pipe allows a significant reduction in overall system complexity, allowing operators to move into deeper waters while lowering OPEX and operational risk.
Furthermore, the composite replaces metallic layers which are susceptible to carbon dioxide corrosion, something increasingly encountered in deep water basins, which may cause stress corrosion cracking unless properly managed. This hybrid riser design, proven with full life-cycle testing, adopts aerospace type materials to significantly reduce permeated gas flow rate through the pipe, reducing operational risk and adding cost benefits over the field lifecycle.
This is part one of a two-part article. Part two can be read here: https://www.oilfieldtechnology.com/special-reports/26022020/why-the-oil-and-gas-industry-needs-flexible-pipe-dreams-part-two/.
Read the article online at: https://www.oilfieldtechnology.com/special-reports/25022020/why-the-oil-and-gas-industry-needs-flexible-pipe-dreams--part-one/