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Direct Electrical Heating of Flowlines (DEH)

Hydrate and wax formation in subsea transport flowlines will cause undesired fluid properties and even blocking of the wellstream, following shutdown and comprehensive repairs. Direct electrical heating (DEH) is developed as a method for avoiding hydrates and wax, and is also applicable for removal of plugs.

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The development work at SINTEF Energy Research has included comprehensive qualification of the heating method. Feasibility of the system is proven through large test programs. A designated simulation tool for the electromagnetic and thermal rating of the system is developed and verified by tests. The DEH Method is now applied on several flowlines, and installation solutions will be developed and modified according to the technology development for subsea installations and equipment. Field developments at deeper waters and long step-outs will make this flow assurance method even more attractive.

Publications from the project:

During the qualification of the DEH Method; SINTEF Energy Research developed test methods and equipment to characterize relevant steel grade with regards electrical and magnetic properties. This makes possible verification of material data used in the calculations of electrical data for the heating system. Also equipment and methods for the performance of hydrostatic tests at high pressures (500 bar) were developed. Test methods and calculation tools for the water exposure of the DEH cable (outer sheath and high voltage insulation) was established, giving decision basis in order to evaluate whether the estimated service time of the heating system is acceptable.

Key Factors

Project start