Hejre Field, Denmark

The Hejre oil and gas field is located in central part of the North Sea. It lies 300km away from the Danish coast in License 5/98 at a water depth of 70m.

DONG Energy is the operator of the field and holds a 60% interest in the field. Bayerngas Norge holds the remaining 40% interest. The partners are investing $1.6bn in the development of Hejre. The field is expected to come online in 2015.

Development of the field will increase reliability of oil and gas supply to Denmark.

Discovery of the Danish oil and gas field

The Hejre field was discovered by the Hejre-1 well in 2001. The well was drilled by the Ensco 101 jack-up rig to a depth of 5,265m.

The Hejre-2 well was drilled in 2005 by the Ensco 101 jack-up rig to a depth of 5,399m. The drilling activities confirmed the presence of oil.

Oil was produced at favourable production rates along with associated gas.

Geology and reserves at the Herje reservoir

The Hejre reservoir is made of the upper Jurassic reservoir sandstones. The sandstones are similar to the UK Fulmar and Norwegian Ula formations.

The reservoir lies at a depth of 5,100m with oil and gas found in the subsoil in a geological layer consisting of sandstone. It is a high-temperature and high-pressure (HTHP) reservoir with a pressure of 1,000 bar and a high temperature of 1700C.

The field is expected to produce 16 million m3 of oil and ten billion m3 of gas during its operational lifetime.

Field development

DONG Energy submitted a plan for approval to the Danish Energy Agency in November 2010. The plan was approved in October 2011. The HTHP nature of the field reservoir required a technically complex production system.

The development concept includes a manned wellhead and processing platform. Five HTHP production wells will be drilled to a depth of 67m and tied back to the platform. Seven more production wells are planned to be drilled in the future.

The field will be decommissioned at the end of its operating life.

Hejre processing platform

The hydrocarbons recovered at the field will include a large concentration of natural gas liquids (NGLs), which necessitate the construction of a dedicated onshore facility. The Hejre processing platform will feature a wellhead, processing facilities and other equipment. It will include a living quarters to accommodate 70 people.

The design of the platform includes a load bearing structure and topsides which will be constructed onshore, towed to the field and installed using barge cranes. Piles will be driven into the seabed for the load bearing structure.

The processing capacity of the platform will be 6,000m3 a day. The processing area will be split into two streams - live oil containing NGLs and sales gas. It will include coolers, separators and gas treatment system.

Exporting oil and gas produced

The hydrocarbons produced at the field will be exported onshore through two new pipelines.

A 90km pipeline will be laid to carry live oil to the Gorm E platform. After going through initial processing, the oil will be transported through existing pipelines to the Fredericia terminal onshore to process the NGLs. A new LPG gas plant and storage facility will be built at the terminal to process the NGLs.

Sales gas will be carried through a new 24km pipeline to the South Arne field. From there it will go through the South Arne-Nybro pipeline to the onshore Nybro Gas Treatment Plant.

Contracts awarded

COWI was contracted to prepare the environmental impact assessment study for the field. It was also involved in assessing the development concepts for the field.

Ramboll was responsible for carrying out the feasibility studies for selecting the development concept for the field. It carried out process simulations, material selection, risk evaluation and life cycle cost estimation.

It was also involved in the FEED tender preparation in 2010.