VESTAMID® PA 12 for liners in oil & gas exploration and production

VESTAMID^® grades specially tailored to the requirements of liners expand the application spectrum to subsea multiphase product pipelines. VESTAMID^® PA12 offers the combination of a close-fit liner technology and a liner material having an extensive subsea track history. On the one hand the integrated liner system of Swagelining Ltd. using PE liner looks back to a long track history in subsea water injection applications; on the other hand VESTAMID^® PA12 has gaint a successful track history as barrier and jacket material in unbonded flexible pipes used for offshore multiphase flowlines and risers. This unique combination offers the operator a reliable, available and economic liner solution for subsea production flowlines and risers. It overcomes the long lead times for corrosion resistant alloys (CRA) and offers total project cost savings of up to 50% over CRA solutions. In contrast to pipeline designs considering corrosion allowance the VESTAMID^® PA12 integrated liner solution eliminates the need of corrosion inhibitors resulting in opex savings and minimizes the required equipment for corrosion inhibition resulting also in capex, space, and weight savings for platforms.

Liners protect steel piping even at temperatures exceeding 60°C

Considering rehabilitation of corroded onshore crude flowlines the liner material used is generally polyethylene; in direct contact with oil, however, its use is restricted to temperatures below about 60°C. VESTAMID^® PA12 offers, for the first time, a liner material combining the advantages of a close-fit design with application temperatures above 60°C.

Liners for pipelines conveying high abrasive media

In addition to its resistance to corrosive media, VESTAMID^® also has extraordinarily high erosion resistance, thereby extending significantly the service lives of piping systems subjected to high abrasive wear. This is advantageous for production pipes in the Canadian oil sands, for example, where conveyor lines have extremely short useful lives and the necessary maintenance and replacement work accounts for as much as 20 percent of downtime in production.

Liner Technology in oil & gas applications

Plastic liners have been used for decades in many areas of steel pipe construction. In most cases they are used for relining corroded steel pipes, but new pipes, such as subsea pipes for water injection lines used in oil production, are also provided with liners to prevent corrosion. A number of different installation techniques are available, including the Swagelining^TM, Rolldown^TM, and Slipliner^TM techniques. The liner material used here is generally polyethylene. Whereas in subsea application PE liner are only accepted for water injection lines PE liners are used in direct contact with oil offshore, however, its use is restricted to temperatures below about 60°C.

Conditions in oil fields are often highly corrosive, and steel piping must be particularly heavily protected against corrosion. This is achieved by designing a corrosion allowance by simply increase the wall thickness of the pipe in addition with injection of corrosion inhibitors to the conveyed fluid or by using corrosion resistant alloys (CRA) as the piping material. The first alternative involves additional operating costs and investments in the required equipment, and the second high capital costs. Moreover, significant bottlenecks occur in CRA supply, particularly in boom periods, leading to extended delivery periods and delays in the exploitation of new oilfields. VESTAMID^® PA12 liners eliminate the need for either corrosion allowance and corrosion inhibitors or CRA. This leads to considerable cost savings and improved time management.

At elevated temperatures the close-fit systems of Swagelining^TM and Rolldown^TM offer advantages over Slipliner^TM, in which an annular space remains between the liner and the steel pipe. In close-fit systems, on the other hand, an overlarge liner is inserted whose outer diameter is generally designed to be 2 to 5 percent larger than the internal diameter of the steel pipe so that the annular space exists between pipe and liner is minimized. A common feature of the above close-fit systems is that the external diameter of the liner is reduced by compression in the elastic region to the extent that the liner can be drawn into the steel pipe by a winch. Within the pipe, the liner tends to revert to its original external diameter until it is flush with the inner wall of the pipe. Thanks to this close fit, any temperature- or swelling-induced linear expansion of the liner is prevented by the high friction against the wall of the steel pipe. This rules out the risk of inversion, also known as axial buckling, arising as a result of changes in length, as could occur with a movable liner. The close fit also increases the collapse strength of the liner: The surrounding piping statically reinforces the close-fitting liner to such an extent that radial buckling resistance is significantly increased.