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, which implies shutdown and comprehensive reparations.
Direct electrical heating (DEH) is developed as a method for removing hydrates and wax, and is also applicable for solving plug situations.
DEH was qualified in 1996/97 as a method to ensure that the temperature in subsea flowlines is above critical limits concerning formation of hydrates or wax.
The development studies have comprised material studies as well as a specific qualification of the heating method.
Feasibility of the system is proven both by scaled tests and on full-scale test installations. These tests are made to develop a proper design of termination of cables to pipe, to study the current transfer zones with a modified anode system and to verify the designated simulation software applied for the electromagnetic and thermal rating of the system. The different material data and design parameters in the heating system are verified in the laboratory tests.
The DEH method is now applied on several flowlines, and installation solutions are being modified according to the technology development for subsea installations and equipment.