Development

Gullfaks is a field in the Tampen area in the northern part of the North Sea. The water depth is 130-220 metres. Gullfaks was discovered in 1978, and the plan for development and operation (PDO) for Gullfaks Phase I was approved in 1981. A PDO for Gullfaks Phase II was approved in 1985. The production started in 1986. The field has been developed with three integrated processing, drilling and accommodation facilities with concrete bases (Gullfaks A, B and C). Gullfaks B has a simplified processing plant with first stage separation. The Gullfaks facilities are involved in production and transport from Tordis, Vigdis, Snorre, Visund, Visund Sør and Brime. A PDO for Gullfaks Vest was approved in 1993, and for recovery from the Lunde Formation in 1995. An amended PDO for the Gullfaks field, covering prospects and small discoveries, which could be drilled and produced from existing facilities, was approved in 2005. Amendments to the Gullfaks PDO, covering Phase I and Phase II production from the Shetland/Lista deposit, were approved in 2015 and 2019, respectively. In 2020, an amended PDO for the development of the Hywind Tampen wind farm was approved. The wind farm consists of 11 floating turbines that started supplying electricity to the Gullfaks and Snorre platforms in 2022/2023. These fields are the first in the world receiving power from a floating wind farm.

Reservoir

Gullfaks produces oil from Middle Jurassic sandstone in the Brent Group, and from Lower Jurassic and Upper Triassic sandstone in the Statfjord Group and Cook and Lunde Formations. Recoverable oil is also present in fractured carbonate and shale in the overlying Shetland Group and Lista Formation. The reservoirs are at depths of 1700-2000 metres in rotated fault blocks in the west and a structural horst (raised fault block) in the east, with a highly faulted area in between. Reservoir quality is generally good to very good in the Jurassic reservoirs within each fault compartment, but poor reservoir communication is a challenge for pressure maintenance.

Recovery strategy

The drive mechanism for the main reservoirs is primarily water injection, with gas injection and water alternating gas injection (WAG) in some areas. Initially, the drainage strategy for the Shetland/Lista reservoir was depletion, but pressure support by water injection has now been implemented.

Transport

Oil is exported from Gullfaks A and Gullfaks C via loading buoys onto tankers. Rich gas is transported by Statpipe for further processing at the Kårstø terminal.

Status

Drilling of new wells on Gullfaks has been challenging for many years due to overpressured areas in the Shetland/Lista interval. Production from the Shetland/Lista reservoirs has gradually contributed to reduced overpressures and improved drillability. Additional wells are being drilled continuously from all platforms. Hywind Tampen started power production 2022/2023.