Statoil’s Gullfaks field: 30 years down, over 20 to go
Statoil’s Gullfaks field, the first ever to be both developed and operated by the company, has celebrated its 30-year anniversary. Most impressively, it is only middle aged and is expected to continue on into the mid-2030s – nearly 30 years beyond the original development plan. Heidi Vella reports on what Gullfaks has meant for Statoil.
The name Gullfaks comes from the word "Gullblokken" (the Golden Block), the original name given to block 34/10, where the main Gullfaks field lies in the Norwegian North Sea, prior to its allocation in 1978.
And the block has certainly proved golden for Norway’s Statoil. It was the first field the oil and gas multinational would both develop and operate, and provided a platform for the company to effectively find its feet on the Norwegian continental shelf (NCS).
Despite foreign interest in the block being very high – hence its nickname – its licence was originally awarded to a wholly Norwegian group, consisting of Statoil (85%),Hydro (9%), a now defunct division of Norsk Hydro, and the now closed Saga (6%). This was the first time a purely domestic consortium had been awarded an offshore licence.
Through Gullfaks, Statoil has developed and tested several key technological capabilities and significantly expanded its subsea installations. Without the technology first used at Gullfaks, it could not have developed fields such as Åsgard, which ranks among the largest developments on the NCS, and Troll, which represents around 40 % of total NCS gas reserves.
This experience ultimately led to Statoil bringing onstream the world’s first subsea wet gas compression system on the seafloor of Gullfaks field in 2015.
First explorations of Gullfaks in the 1970s indicated that it was a significant oil and gas reservoir, yet the field was not expected to operate long into the new millennium.
Since production started at Gullfaks on 22 December 1986, 2.6 billion barrels of oil (bbo) have passed the loading buoys, according to the company. And last year, The Norwegian Petroleum Directorate (NPD) gave the green light for the company to use the oil and gas platform on the Gullfaks field in the North Sea until 1 January 2036, which corresponds to the length of the production license.
"Wise decisions, outstanding subsurface work, the use of new technology and good teamwork in the Norwegian petroleum cluster have more than tripled the expected field life and ensured enormous value creation from Gullfaks,” says Gunnar Nakken, senior vice president for the operation’s west cluster.
“After 30 years, we still believe in Gullfaks, which has seen major investments and undergone extensive upgrades in recent years," adds Nakken, who is also Statoil's site manager in Bergen.
In total, the project consists of three production platforms: Gullfaks A (1986), Gullfaks B (1988), and Gullfaks C (1989).
Over the years, the project has continued to grow. Statoil opened the valves of its very first subsea well in Gullfaks and the technology has since been used on many other fields, with many satellites linking back to the field. These include Rimfaks, Skinfaks and Gullveig – which have all been developed with subsea wells remotely controlled from the Gullfaks A and C platforms.
The Rimfaks satellite began production in 1999, Skinfaks in 2007, Gimle in 2006 and Gullveig in 1998.
In late 2010, production at the original Gullfaks installation began to decline. Over the next two years wells with compromised integrity were repaired by Statoil with the injection of water being stabilised.
Expanding improved oil recovery
A few key factors and technologies have been instrumental in prolonging the life of Gullfaks. Statoil says that the field is an outstanding example of innovation in improved oil recovery (IOR). The company has won the Norwegian Petroleum Directorate's IOR prize, among other awards, for its proficiency in this area.
According to the company, water injection has been the main reason for the high recovery factor at Gullfaks, as well as installation of new loading buoys in 2014 and a subsea gas compression technoloty developed by the company, in collaboration with others.
In December 2015, Statoil and partners Petoro and OMV brought on-stream the world’s first subsea wet gas compression on the seafloor of the Gullfaks field. The $525m project at the Åsgard section of the field involved the first use anywhere of a subsea wet gas compression system. Since then production at the field has been increased by more than 16 MMboe.
The technology was first tested at the company’s K-lab laboratory at Kårstø near Stavanger in 2008 and represented a ‘quantum leap’ in technology, significantly improving recovery rates and extending the lifetimes of a number of gas fields, including Statoil's Tordis field, located between the Tordis Subsea Field and the Gullfaks C platform, which has also been part of the company’s IOR project.
“Subsea gas compression represents an important leap forward in the efforts to improve recovery and extend the producing life of several gas fields," Siri Espedal Kindem, senior vice president for technology, said at the time. "Having implemented this technology, we are also one step closer to our ambition of moving processing facilities down on the seabed – in other words, a subsea factory."
Subsea compression has a more robust impact than conventional platform-based compression. It also avoids the extra weight and space usually taken up from fitting a compression module to a platform. Furthermore, a wet gas compressor doesn’t need gas and liquid separation before compression, and smaller modules can be used for a simpler structure on the seabed.
Gullfaks is a Statoil success story, but the field has suffered some tragic incidents during its lifetime. In 2016, 13 people departing the Gullfaks-B platform died after their transport. At the time, Nakken said that although Gullfaks had faced many challenges in its history, none had been as “difficult as this tragic accident”.
That same year, the field was taken offline for a period following a chemical leak on an umbilical line and just recently, in March 2017, a crane reportedly toppled over onto the deck of its Gullfaks B platform during a drilling operation.
Despite these incidents, the Gullfaks team say they are very proud of what they have achieved at the field. “Gullfaks is a prime example of the best that this industry has achieved in Norway," says Nakken.
The goal is to keep achieving, starting with raising the recovery factor on Gullfaks from 59%, to 62% and ensuring that the production horizon for the Golden Block continues to stretch towards 2040.