K 2010 Trade press conference
June 22 and 23, 2010 in Frankenthal, Germany
Hardness test under water
Polyurethanes in the offshore oil and gas industry
Presentation by Dr. Marcus Leberfinger
Head of Segment Elastomers
BASF Polyurethanes GmbH, Lemförde, Germany
In spite of all the efforts made searching for renewable sources of energy, fossil fuels such as oil and gas will continue to be indispensable in the coming decades. Tapping into offshore sources will play an increasingly significant role, one example are the huge deposits off the Brazilian coast. Experts anticipate that the offshore share in the total oil and gas production will triple over the next ten years. The recent explosion of the Deepwater Horizon oil rig and its consequences in the Gulf of Mexico are evidence of the hazards involved in offshore operations. Thus, making activities of the offshore industry as safe as possible and being able to utilize such resources in the first place call for the use of reliable high-performance plastics.
Over the past years, BASF Polyurethanes has been consistently expanding its expertise by developing customized polyurethane systems for offshore applications. These polyurethane casting systems that are employed here consist of two liquid components. Special metering machines normally use catalysts to bring about the reaction of the components that later will make up the finished high-performance plastic. The development of these offshore polyurethane systems has been focused not only on resistance to high temperatures and seawater but also on the use of environmentally friendly catalysts that are free of heavy metals. Moreover, the products are extremely tough. After all, they have to be able to withstand high forces while, at the same time, being sufficiently elastic to absorb dynamic loads and impacts.
Protection against currents
One application example are vortex-induced vibration (VIV) strakes, spiral sheaths made of polyurethane that are affixed to the pipeline rising from the seabed, called riser. The special feature of the strakes is their helical shape, which vertically dissipates the horizontal current forces. These strakes are polyurethane cast parts, designed and produced by Trelleborg Offshore. Immediately before the pipeline is laid, the strakes are mounted on the riser aboard the pipe-laying vessel, after which the riser is lowered into the sea. While the pipeline is being installed from the ship over the so-called stinger, the enormous weight of the pipeline exposes the strakes to such colossal loads that they are severely deformed. This is why the chemical structure of the polyurethane material has to be formulated in such a way that it cannot break. Furthermore, the cast part has to return to its original shape after being stressed. For this reason, Trelleborg performed a 70 tons installation load test to qualify the material’s suitability for this challenging task. During this stinger test, the sheathed pipes run over a device that simulates a stinger. The test has demonstrated that the plastic is robust and its recovery behavior is very good. Under water, the specific shape of the strakes ensures that the pipeline is positioned securely in the water and does not start to vibrate since this could lead to breakage of the pipes.
Pressure resistance and thermal isolation
Under certain circumstances, there is a need to manually inspect and maintain the pipeline underwater. Mostly, however, the pipelines are at depths that cannot be reached by the deep-sea divers on their own. Therefore a diving bell has been developed to transport experts to depths of 300 meters. Thus the bell was designed as a submersible decompression chamber. The thermal isolation was performed by Trelleborg Offshore using a so called glass-syntactic polyurethane system from BASF Polyurethanes: The polyurethane is foamed apparently, however a true foam would not be able to withstand the hydrostatic pressure underwater and would collapse. This is why the polyurethane matrix is mixed with hollow glass microbeads that are under vacuum, but ensuring that the material can resist the pressure at the same time. These hollow glass microbeads function like miniscule thermos bottles. The special feature of this polyurethane system is the realization of long flow paths achieved through its viscosity and through its reaction profile when the mold is filled with the two components.
The principle of glass-syntactic polyurethane is also employed in offshore pipelines. Crude oil is pumped at temperatures of 120 to 140 degrees Celsius [248 to 284 degrees Fahrenheit]. In order to be able to transport the black gold over long distances, it is imperative to keep it from cooling down, especially during a possible shutdown, so as to prevent the pipeline from clogging. This task, too, is achieved through the use of glass-syntactic polyurethane, which also offers resistance against the hydrostatic pressure of up to 300 bar at a depth of 3,000 meters.
A general trend in the offshore industry is the exploitation of ever-deeper oil deposits. This means that the crude oil being pumped and transported is even hotter, which will pose a new challenge for such materials.
Buoyancy thanks to Polyurethane
If innovative systems have to be developed under extreme conditions you have to rethink existing solutions to make the difference. This is also true for offshore pipelines which are laid over many kilometers and at a depth of over 500 meters.
Together with the British firm Manuplas BASF Polyurethanes UK has now developed a PU system for subsea buoys and floats. The mouldings are primarily employed as buoyancy and mooring aids for risers in the oil and gas industry. Risers coming from extreme depths are lying on the buoys compensating the weight of the risers and preventing them from the influence of extreme drag forces. The buoys also come into service, in case the pipeline needs to be bridged over rocks at the bottom of the sea. With the help of these barrel-like buoyancy aids, the pipeline is guided safely across obstacles and prevented from damage caused by abrasion by rocks.
Underwater buoys used to be cut out of glass microsphere filled epoxy resin blocks which were then treated with a special coating. Their production took three days. The polyurethane solution, developed by Manuplas within only two years, reduces production time by up to 48 hours. Again, the core of this buoy consists of a one-shot glass-syntactic polyurethane system, which was transformed into the finished part in one shot. An additional polyurethane coating seals the surface and protects the buoy from mechanical damages. For this application tailor-made Elastocoat® polyurethane systems were developed. They can withstand the enormous pressure of the water in addition to being produced very quickly for an industry which often operates on a 'just in time' basis.
Worldwide Service
The offshore industry is a conservative and global industry, but it relies on innovative high-performance products. Thanks to its 38 polyurethane system houses around the world, BASF can provide polyurethane products and technical service with a constant level of quality to the offshore industry in every region of the world, be it Brazil or the Baltic Sea.