Commitment and courage on Statfjord

Chapter 4: Recovery

Discovered in 1974, Statfjord was one of the pioneer fields on the Norwegian continental shelf (NCS). Today, the commitment made and courage shown in testing and adopting new methods can be seen to have created substantial value. This field has accounted for about 12 per cent of Norway’s total oil and gas production. It was the biggest oil producer on the NCS from 1981 to 1994.

This field was originally expected to remain on stream until the mid-1990s. The Statfjord late life project, approved in 2005, aimed to maintain production to 2012. Current plans call for it to continue until 2022.

A precondition for success is that both expertise and capacity are present on both sides – along with the ability and willingness to pursue a dialogue in order to find solutions which benefit both licensees and society.

One of the NPD’s most important duties is to see to it that possible measures for improved recovery are taken into account as early as the planning phase of a project. This principle applied when development began on the NCS, and is still in force today.

Choosing the right drainage strategy at an early stage was important on Statfjord. After a series of discussions between the companies and the NPD, an approach was selected which also ensured good production in the field’s late life.

Water was injected in the Brent formation – the good upper reservoir – and gas in the lower Statfjord formation to exploit the fact that this was the most effective use of gas. It also permitted control over the whole production period. That decision proved successful and remains so today.

In addition came work on Statpipe, another important milestone for reducing the risk of losing gas resources. Gas was carried in this pipeline from Statfjord to Kårstø north of Stavanger before continuing to continental Europe.

Fully documented technology was not available at that time for laying pipelines across the deepwater Norwegian Trench close to Norway’s coast. Many people doubted whether it was possible.

Norwegian engineering expertise was equal to the task, just as it was to other challenges on the NCS. Statpipe was and is important for Norway’s extensive gas export infrastructure.

Since no arrangements were initially in place for transport and sale of the gas, it was injected to help maintain pressure in the Statfjord reservoir and increase oil production. Statfjord is one of the three Norwegian fields where the largest volume of gas has been injected. Calculations indicate that this has yielded five to 10 per cent of additional oil. Most of the injected gas is currently being produced now and until the field goes off stream.

Statfjord is an example of a very successful use of gas and water alternating gas (WAG) injection. This experience has been useful for other fields.

Continuous maintenance and upgrading of drilling equipment for efficient drilling of production wells has also been part of the recipe.

Production is currently well above the level estimated when the plan for development and operation (PDO) of Statfjord late life was approved.

Although its output is now an eighth of what it was when daily production peaked in 1987, the field continues to yield revenues both to its licensees and to the Norwegian Treasury.