Heating System Providing Skin Effect Heating Systems for the Kharyaga Oil–Field in Siberia
Bartec delivered skin effect heating systems into the Kharyaga field, providing engineering, calculation, design, supply, installation, commission, and supervision in frozen Siberian. The target was to assure frost protection and temperature maintaining at the long transfer pipe lines of the oil field in the oil-rich Nenets tundra.
The Kharyaga oil field in Western Siberia, with overall oil reserves estimated to 160 million tons, epitomizes the difficulties of Arctic and extreme-cold regions: isolation, extreme weather conditions, and a fragile ecosystem.
Yet some years of uninterrupted production have demonstrated the validity of the solutions conceived by Total who, together with StatOil and the Nenets Oil Company, operate the Kharyaga oil field near the Barents Sea. The Russian government approved this joint venture in 1999. In 2009, Bartec started to work on the Kharyaga phase III development project.
Despite the harsh conditions some 60 kilometers north of the Arctic Circle — remote location, winter temperatures down to -46 °C and very strong winds — production at Kharyaga has continued uninterrupted for years, thanks to a number of specific measures: By drilling with deviated wells from a limited number of pads away from a central processing station the impact of surface installations is minimized.
To prevent plugging the waxy oil is maintained at +40 °C. All facilities use high-performance insulation and Bartec’s skin effect heating systems. A first oil line between the North Pad and the central facility had 10,4 kilometers length. Another line for a second pad in the East followed fastly. Empty caves in the earth are filled with +60 °C warm water. Workspaces are enclosed and heated to protect workers and equipment with ventilation for confined areas due to explosion risks. During phase III development, heat recovery units will be installed on the new gas turbines as an energy efficiency measure.
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.