The Norwegian Petroleum Directorate has recognized Statoil ASA for improving oil recovery via gas injection at Oseberg field in the North Sea off Norway.
Statoil calculates the recovery factor at Oseberg’s main reservoir at as much as 69%, compared with a Statoil average of 50% for the entire Norwegian Continental Shelf and 35% for the rest of the world. This translates into improved oil recovery by gas injection of 400-500 million bbl of oil at Oseberg.
In fact, without giving a figure, Statoil said it has doubled Oseberg’s reserves since submitting the field development plan in the 1980s.
Carl Frederik Eek-Jensen, head of petroleum technology in the Oseberg organization, said, “Last year we managed to replace our production volume by new reserves in the Oseberg area. That is proof of perseverance in an area where we have producing for more than 20 years.”
The initial plan was to develop Oseberg using injected water for pressure maintenance, but the NPD convinced then-operator Hydro to examine the technological requirements of injecting gas from Troll field and urged the Oseberg partners to agree on a final development decision.
The Troll Oseberg gas injection project, or TOGI, was revolutionary and controversial and came on stream in 1991. The goal was to inject gas from Troll into Oseberg to ensure optimal recovery. The project involved a remotely controlled subsea installation, the first of its kind in the world. Some 21.7 bscm of gas were injected in 1991-2002.
Since 2002 Oseberg’s produced gas has been recycled, and at present 2 bscm/year of Oseberg gas is produced and sold. Most Oseberg gas is not to be produced and sold until after 2020. Until last year this was to have begun in 2017.
Statoil and the Oseberg license partners are still investing heavily in the field. Eek-Jensen said 4D seismic is now available to map the remaining resource and design and position new wells. Considerable sums have been invested in drill upgrades on the platforms.
Statoil is still drilling on all four of the field’s permanent platforms and tieing new discoveries back to existing installations. The Stjerne development will come on stream in 2013, and the company has plans for more seabed templates and a fast-track development project.