High efficiency heating method for subsea pipelines heating

Due to the harsh conditions sub-sea flow lines are exposed, they are subject to clogging by hydrates. Up to now, sub-sea pipeline heating was mainly used for purpose of preservation in case of production shutdown to prevent this pipe clogging. Access to more complex fields with lower quality of oil or longer distances of transfer to process plant requires to permanently heat the oil to maintain good viscosity and high flow rate. With a requirement of 20 to 50 kW/km and length in excess of 50km, this heating process represents a significant amount of energy per year. A new design of heating system and insulation structure of the pipes increase the efficiency of the heating process from 50% up to more than 90%. This design also allows use of standard method for electrical protection of the heating elements compared to the existing ones. This article will present a brief comparison of the different systems used today and the main difference with the new design of the electrically heated pipe in pipe. Development of a site is ongoing at the moment and a summary of experience will be presented.