Subsea Drilling Riser

Subsea flowlines are the subsea pipelines used to connect a subsea wellhead with a manifold or the surface facility. The flowlines may be made of flexible pipe or rigid pipe and they may transport petrochemicals, lift gas, injection water, and chemicals. For situations where pigging is required, flowlines are connected by crossover spools and valves configured to allow pigs to be circulated. Flowlines may be single pipe, or multiple lines bundled inside a carrier pipe. Both single and bundled lines may need to be insulated to avoid problems associated with the cooling of the produced fluid as it travels along the seabed. Subsea flowlines are increasingly being required to operate at high pressures and temperatures. The higher pressure condition results in the technical challenge of providing a higher material grade of pipe for highpressure, high-temperature (HP/HT) flowline projects, which will cause sour service if the product includes H2S and saltwater. In addition, the higher temperature operating condition will cause the challenges of corrosion, down-rated yield strength, and insulation coating. Flowlines subjected to HP/HTwill create a high effective axial compressive force due to the high fluid temperature and internal pressure that rises when the flowline is restrained.


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