Fibre-reinforced polymer composites have found extensive applications in the oil and gas industry for the last three decades in areas such as modules, protection, equipment, spoolable pipes and pressure vessels.
Significant advances have been made in the areas of composite pipe work and fluid handling. The high cost to replace steel piping in retrofit applications and increased longevity in new construction are driving the use of composites, which withstand the severe conditions experienced in offshore environment. In the offshore oil and gas industry, composites offer several potential advantages with the cost of manufacturing and erecting oil rigs could being significantly reduced if heavy metal pipelines could be replaced with lighter ones made of composites. Composite pipes could be used for fire-water piping, sea water cooling, draining systems and sewerage. The cost advantages of composite products are much greater when they replace expensive corrosion-resistant metals such as copper-nickel alloys, duplex / super duplex stainless steel, titanium etc. used in offshore platforms for various applications. Their resistance to corrosion helps in improving reliability and safety & also leads to lower life cycle costs.
Piping systems using glass-fibre reinforced polymer composites (GFRP) offer complete solutions for the offshore environment against highly corrosive fluids at various pressures, temperatures, adverse soil and weather conditions (especially in oil exploration, desalination, chemical plants, fire mains, dredging, portable water etc.) Composite pipes are commonly used in oil transportation where resistance to crude oil, paraffin build-up as well as ability to withstand relatively high pressures is required. The system is also being used on offshore rigs for sea water cooling lines, air vent systems, drilling fluids, fire-fighting, ballasts and drinking water lines in offshore application. The lightweight properties of GFRP helps reduce heavy and expensive construction costs. Established oil fields use composite pipes for high pressure and steam-injection lines for the recovery of oil preserves. Composites can withstand the detrimental effect of brackish water when expelled under pressure from fire mains, making rupture less likely and the system more reliable. The chemical resistance and service temperature of such composites in a particular fluid depends on resin formulations, additives used etc.
Composite grids/gratings, hand rails, cable trays, ladders, decking, flooring have been used on fixed and floating off-shore platforms world over for more than 30 years. In topside applications, the inherent corrosion resistance of composite materials reduces life cycle costs by minimising its maintenance.
Conventionally, grids/gratings are made of mild steel/cast iron. Due to the limitations on corrosion resistance, weight, durability, lifecycle costs etc. for the metallic gratings, composite grids/gratings perform much better due to their superior properties under aggressive environments as in chemical process industry.
Composite ladders are stronger than wood or aluminium and do not absorb water, rot or corrode. The products can be pigmented with a suitable colour along with the resin during the pultrusion process. With the colour throughout the part, there is no chipping or peeling. Unlike aluminium, composites have excellent insulation properties which substantially reduce the hazard of electrocution by contacting high voltage power lines. For rough jobs where a ladder takes a beating, composite provides the ultimate ruggedness and long-term durability.
Composite coil tube replaces the existing steel coil tubing for high pressure down-hole applications in offshore platforms. The tube can be coiled or uncoiled on a drum and can easily be transported to the desired location of the wells.
Composite riser is the pipeline that connects the rig of the water surface to the well bore at the seabed. They must separate the oil, gas and drilling fluids from seawater. The weight of riser can drastically come down with the use of composite material as alternative to heavy metallic risers. Composite risers can be designed to withstand highly corrosive chemicals, salts and fluids under different environmental conditions. The durability and life cycle costs in offshore platforms can be improved.
High Pressure Accumulator Bottles
To accommodate the relative motions between the platform and the riser, in case of tension leg platforms, a telescopic joint is used at the upper extremity of each riser. These joints require a tensioning system capable of storing and releasing large amounts of energy as movement takes place. Tension is applied through gas-pressurised tensioners with accumulator bottles. In older designs steel accumulator bottles were used but recently considerable success has been achieved with composite bottles. The composite bottles offer significant weight and cost saving being less than a third of the weight of equivalent steel bottles. These bottles can withstand very high internal pressures.
Caissons and Pull Tubes
Caissons are attractive applications for composites as an offshoot of composite piping technology. In general, caissons are used to provide the service fluids to enter or leave the sea. These are located at splash zones in the sea water. Caissons are designed to withstand flexural fatigue loads created by waving loads and corrosion to aqueous fluids in the sea.
Case Studies in Oil and Gas