Heidrun is a field on Haltenbanken in the Norwegian Sea, 30 kilometres northeast of the Åsgard field. The water depth is 350 metres. Heidrun was discovered in 1985, and the plan for development and operation (PDO) was approved in 1991. The field has been developed with the world’s first ever floating concrete tension-leg platform (TLP), installed over a large subsea template with 56 well slots. Six subsea templates in the southern and northern areas are additionally tied-back to the TLP. Production started in 1995. The PDO for the Heidrun northern flank was approved in 2000. The Maria field receives water for injection from Heidrun. The Dvalin field is being developed as a tie-in to Heidrun, and a dedicated processing plant for Dvalin was installed on Heidrun in 2019.