Providing Skin Effect Heating Systems for the Kharyaga Oil–Field in Siberia
A Sensitive Environment
Kharyaga is located within the permafrost zone in a sensitive environment comprising tundra, swamps, shallow lakes and rivers, with numerous species of flora and fauna. Especially the tundra is an extremely sensitive environment where regeneration takes time.
These conditions explain why the field’s development must comply with environmental principles such as the optimization of water management; limitation of greenhouse gas emissions; prevention of soil contamination and a selective waste collection and disposal. All Kharyaga contractors are required to respect these rules; drilling activities are carefully monitored and a “No Spill” policy is applied on the rigs of new pads.
Warmth to the Permafrost
Bartec delivered its complete skin effect heating systems to Kharyaga, providing engineering, calculation, design, components, installation, commission and supervision. The target was to assure frost protection and temperature maintaining at the long transfer pipe lines, an application where the system could show its advantages: It is cost effective at long distance lengths with the least number of feeding points available, Bartec states.
The heating circuit is encapsulated in a tube element under the insulation and cladding. A constant power output ensures safe temperatures for the medium and installation, certified for use in explosive atmospheres.
The skin effect heating system is an electrical heating circuit using the alternating current phenomenon on the inner surface of a ferromagnetic tube.
The heating element is a plastic insulated cable inside a steel tube, that produces the majority of heat output. At the end, the heating cable is connected to the tube end to return the current and close the heating circuit (serial circuit). The current density and flow back is limited to the inner surface of the tube, with a thickness of about 3 millimeter.
To ensure electrical safety, the heat tube (or envelope) is grounded every 600 meters. All parts of the envelope are protected against direct contact. Even at the maximum rated voltage of up to 5,000 Volts, the current flow is always and only at the inner side of the carbon steel heat tubes.
The electrical heating circuit is tailored to any needs by variation of the heat tube size, electrical heating cable size, supplied voltage and insulation material. The high voltage transformer and the distribution panel are customized to the individual project requirements.
The maximum length of the heating cable is 600 meters. Therefore, there are auxiliary devices along the carrier pipeline. These pull & splice boxes are only used during construction and to splice the cable ends, allowing a maximum circuit length of ten kilometers with only one feeding point.