Electrical Heating of Subsea Flowlines
Direct electrical heating system (DEHS) offers an attractive method for flow assurance with the potential of reducing OPEX. The system allows for active hydrate and wax control by controlling thermal conditions inside the flowline.

The principle behind DEHS is to pass an electrical current through the pipe wall. By controlling the current, the pipeline inner wall will at all times be kept above the wax and hydrate formation temperature. As a result, problem free and reliable transportation will be achieved. Traditional methods for flow assurance, by use of chemical treatments and pressure evacuations, have considerable operations costs with long down time and may present a risk to the environment. Since 1987 Norwegian oil companies have been investigating different electrical heating methods for flow assurance. Nexans has been involved in development of the alternative methods. As a result of this work, direct electrical heating has at the time of writing been installed at four different fields. Nexans supplied the cable and subsea systems for all four projects.