Optimisation of Thermal Insulation of Subsea Flowlines for Hydrates Prevention

Abstract

Abstract In the development of an oil field, the assurance that produced hydrocarbon will flow is a critical determinant for the development of an oil and gas field even when other disciplines such as subsea design, reservoir engineering, artificial lift equipment, pipeline engineering have done a thorough analysis. Hydrate formation is one of the challenges of flow assurance in an oil and gas pipeline especially those installed in deepwater oil fields. Insulation of subsea pipelines is paramount to the prevention of hydrate formation. This work investigates the best material that is suitable for the thermal insulation of subsea flowlines using the ANSYS software package, and then provide the best composite arrangement of insulation materials for better heat optimisation. Four insulation materials were considered; Aerogel, Mineral Wool, Paraffin Wax and Grooved Mineral. A pipe-in-pipe (PiP) flowline model filled with fuel oil, at an inlet temperature of 60°C, was simulated on ANSYS by varying the configuration of the respective insulation material sheath; the heat transfer method in the PiP is by convection from the outer pipe to the ocean ambience at a temperature of 4°C. Results obtained from the simulation established that Aerogel is best for insulation among those considered, this is because of its low thermal conductivity and high specific heat capacity; in contrast, Grooved Mineral simulation result presented a poor performance. To ensure maximum heat conservation through optimum insulation, a composite configuration of insulation materials was proposed.