Pipeline Heating Systems
Pipeline Heating SystemsThe formation of hydrates is a well-known problem in subsea production systems for oil and gas. When the pipeline content (mix of oil and water) cools down, the temperature is approaching the ambient seawater temperature.
This can cause flow assurance challenges such as flow line blockage or reduced capacity. The pipeline content should therefore be kept above the critical temperature - depending on water cut, salt content and pressure, the hydrates will form typically at temperatures below 25 degrees Celsius.
Traditionally, chemicals (methanol) have been used to remedy this problem. Alternatively, hydrates can be prevented using thermal insulation in combination with additional electric heating. In this approach, a single-phase electrical current is supplied to heat the pipe content above the hydrate formation temperature. The heating method is known as Direct Electric Heating (DEH) as the steel-built pipeline is heated by forcing single-phase current directly through the pipe steel. Qualified by Statoil in the mid-90s, there have been number of projects in the North Sea with more than 100 kilometres of pipelines heated by DEH. Another pipeline heating technology which has been adopted recently is electrical heat tracing / electrical trace heating (EHT / ETH), which uses three-phase cable circuits.
Direct Electrical Heating Systems (DEH)Siemens Energy offers DEH power supply systems to prevent hydrate formation during planned and unplanned process shutdown.
Our systems will contribute to a consistent flow of hydrocarbons despite challenging fluid characteristics and temperature conditions at the seabed. The respective modules of the systems may contain power electronic components as well as control and protection units for the topside equipment and subsea pipeline to be installed on the platform deck.
The systems are designed to control, compensate and balance the single-phase electrical load that the pipeline and the piggyback cable constitute. Each of the systems is customized to the power requirements and electrical properties of the specified subsea load, in both “heat-up” and “maintain heat” mode. The systems are designed to be optimally tuned at any load condition to ensure an excellent power factor, low harmonic feedback, and to have low negative sequence current - important for minimal impact to the platform power grid.
Auxiliary systems for fiber-optic temperature monitoring of the piggyback cables are offered optionally, as well as solutions for remote connection to the modules’ control and protection system via a secure internet connection.
Electrical Trace Heating (ETH)Siemens Energy has a conceptual design for a Subsea Medium Voltage ETH Power Unit.
Our conceptual design for a Subsea Medium Voltage ETH Power Unit, allows subsea power distribution to multiple ETH loads, and uses components already qualified in the Subsea Power Grid program, together with field-proven topside components, in order to achieve a reliable design. In combination with other subsea power grid units, like the subsea transformer, even higher degrees of flexibility and customization for specific project requirements can be achieved.
Siemens Energy also offers connectivity solutions for ETH applications using the SpecTRON 8 family.