Gullfaks

Discovery and Licensing

The Gullfaks field was discovered in 1978 in block 34/10 of the northern part of the North Sea. The field was awarded to a purely Norwegian group of licensees, including Statoil (now Equinor), Norsk Hydro, and Saga Petroleum, with Statoil appointed as the operator.

Location and Geology

The Gullfaks field is situated in the Tampen area of the North Sea, at water depths ranging from 130 to 220 meters. The reservoirs consist of delta sandstones from the Middle Jurassic Brent Group, shallow-marine Lower Jurassic Cook Formation sandstones, and the fluvial-channel and delta-plain Lower Jurassic Statfjord Formation.

Platforms and Infrastructure

The development of the Gullfaks field involves three substantial production platforms:

• Gullfaks A: This is an integrated drilling, processing, storage, and accommodation platform. It was installed in 1986 and is located at a sea depth of 135 meters. The platform has an initial production capacity of 245,000 barrels of oil per day and accommodates 330 crew members.

• Gullfaks B: This platform is a simpler drilling and wellhead platform, installed in 1988. It is located at a sea depth of 142 meters and has a production capacity of 150,000 barrels of oil per day. It accommodates 160 crew members. Oil and gas from Gullfaks B are transferred to Gullfaks A and C for processing, storage, and export.

• Gullfaks C: Installed in May 1989, this platform is also a concrete gravity platform, similar to Gullfaks A but positioned at a deeper water depth of 216 meters. It has a production capacity of 250,000 barrels of oil per day and accommodates 300 crew members. Gullfaks C holds the record for the heaviest object ever moved relative to the Earth's surface, with a total displacement between 1.4 and 1.5 million tons.

Production and Processing

• The combined production capacity of the three platforms is approximately 630,000 barrels of oil per day.
• Oil from the platforms is stored in the gravity bases and loaded onto tankers via loading buoys.
• Gas is transported via the Statpipe system to the gas facility at Kårstø for further processing and then exported from there to Ekofisk and eventually to Emden in the Netherlands.

Satellite Fields

The Gullfaks field includes several satellite fields developed using state-of-the-art subsea technology:

• Gullfaks South: Located in blocks 34/10 and 33/12, production started in October 1998. It produces oil, gas, and condensate, with associated gas reinjected into the reservoirs.
• Rimfaks: Proven in 1983, it has oil, gas, and a high-condensate content. Production is tied back to the Gullfaks A platform.
• Gullveig: Discovered in 1995, it contains oil with small quantities of associated gas. Production started in 2001 and is tied back to the Gullfaks A and C platforms.
• Skinfaks: Another satellite field, though less detailed information is available compared to the others.
• Tordis Field: Located 11 kilometers southeast of Gullfaks C, it is tied back to the Gullfaks C platform. A subsea separation manifold was installed in 2007.

Production History and Peak

• Production from Gullfaks A began on December 22, 1986, followed by Gullfaks B on February 29, 1988, and Gullfaks C on November 4, 1989.
• The field reached its peak production in 2001 at 180,000 barrels of oil per day.

Reservoir Management and Recovery

• The field has undergone various improvements in recovery techniques, including horizontal and extended reach wells, new completion and sand control technologies, and water alternating gas (WAG) injection.
• The use of subsea installations and gas reinjection has been crucial in maintaining reservoir pressure and enhancing recovery rates.

Incidents and Safety

• Between November 2009 and May 2010, there were multiple well control incidents at Gullfaks C, which were investigated by the Petroleum Safety Authority Norway. The report highlighted the potential for a full-scale disaster and questioned the effectiveness of Statoil’s safety measures.
• On April 29, 2016, a helicopter carrying oil workers crashed while flying from the Gullfaks field to Bergen, resulting in the deaths of all 13 people on board.

Modifications and Upgrades

• The platforms have undergone several modifications to increase capacity and improve efficiency. For example, Gullfaks A is being modified to enhance its gas treatment and reinjection capabilities, with new modules being installed.

The Gullfaks oil field is a significant example of advanced offshore oil and gas production, showcasing the use of concrete gravity platforms, subsea technology, and sophisticated reservoir management techniques.