Siemens Energy has received an order to deliver customized direct electrical heating (DEH) power supply systems for ten subsea flow lines, with an option for two additional systems. Customer is BP Exploration Limited and all the systems are to be deployed on BP-operated Shah Deniz gas field in the Azerbaijan sector of the Caspian Sea. Delivery of the equipment is scheduled for end of 2015. When completed, this is expected to be the world’s largest subsea pipeline heating power system.
Siemens scope of supply for the Shah Deniz Stage 2 development project includes the delivery of customized topside DEH power supply systems to be used on ten subsea flow lines to prevent hydrate formation during planned and unplanned process shutdown. Deepwater natural gas reservoirs and low temperatures induce hydrate formation, which can cause flow assurance challenges such as flow line blockage or reduced capacity. The DEH power systems from Siemens will contribute to a consistent flow of hydrocarbons despite challenging fluid characteristics and temperature conditions at the seabed. The respective modules of the systems contain power components as well as a unique control and protection system for the topside equipment and subsea DEH cables. They will provide power for the heating of pipelines when required by the operations and will be installed on the platform deck.
The order includes full-load testing of the containerized systems that simulates real-life conditions to verify the integrity and full functionality of the system before shipment to Azerbaijan. This is key in order to ensure the reliability and availability required for this type of critical equipment.
“Siemens is an established supplier of DEH systems and Subsea Solutions. With this contract award in the prolific Shah Deniz field, we will strengthen our position in the growing market for direct electrical heating,” said Mario Azar, CEO of the Siemens Energy Sector’s Oil and Gas Solutions Business Unit.
The 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, the single phase electrical current is supplied to heat the pipe content above the hydrate formation temperature. The heating method is known as 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 kilometers of pipelines heated by DEH.