The Asgard field is located 150 km outside the Norwegian coast north of Trondheim and include oil production from a FPSO (Asgard A) and gas production from a SEMI (Asgard B). The oil production started early in 1999 and the gas production started in November 2000. The field include 300 km of flowlines and 17 production and gas injection templates (4 wells each) Oil is produced mainly from the Smorbukk South and Southern part of the Smorbukk reservoir while gas will be produced from Midgard and the northern part of the Smorbukk reservoir. Different methods for hydrate control have been implemented for the flowlines from the various reservoirs such as:
Depressurisation and inhibition
Continuos use of glycol
Bundles
Direct electric heating
The background for selecting the various concepts and the work performed for qualification and implementation of the Direct heating concept will be presented in this paper.
The Direct heating concept for hydrate control of subsea pipelines is a new developed concept which have been qualified and used for the first time on the Asgard phase 2 production flowlines. Direct heating have been implemented for 6 flowlines producing from subsea templates at the Northern parts of Smorbukk to Asgard B with flowline length from 6 to 9 km (total length of 45 km of 10" production lines) For the Smorbukk production hydrates start to form when the temperature in the flow falls below 25°C which is relevant for longer shut down situations. Direct heating include keeping the temperature above the hydrate formation temperature by use of spare electrical power which normally is used for processing the production. Direct heating does not create any pollution to the environment or the production (power generation) as the alternatives and it is a user friendly concept.
