Fact box 4.4 Exploring near infrastructure and extended production – the Norne area
The NCS north of the 62nd parallel was opened for petroleum operations in 1980.
Until 1990, exploration was extremely disappointing outside Nordland county but very successful off the Trøndelag region.
In the winter of 1989, PL 159 in the Nordland II area was awarded in licensing round 12-B with Statoil as operator. Drilling the Alpha prospect with well 6507/3-1 in the summer of 1990 yielded a discovery later named Alve, which was brought on stream as a satellite tied back to Norne.
Although Alve was relatively small and consisted moreover largely of gas, indications existed that the reservoir might have contained oil. This led Statoil to believe that oil could be present in block 6608/10, covered by PL 128, just to the north of 6507/3-1.
Drilling commitments in the licence had already been met and, to retain the acreage after the initial period expired on 28 February 1992, the licensees had to promise another wildcat. Spudded on 28 October 1991, 6608/10-2 was completed on 29 January the following year and Statoil could announce an oil discovery which was later named Norne.
This discovery was substantially larger than the pre-drilling estimate. An appraisal well was drilled in 1993, and a new exploration well in 1994 proved 6608/10-4 (Nordøstsegmentet). A plan for development and operation (PDO) was submitted in June 1994 and approved the following March.
Estimated resources were then about 72 million scm of oil and roughly 15 billion scm of gas. The field was developed with a floating production, storage and offloading (FPSO) unit, and came on stream in 1997 – five years and nine months after completing the first discovery well. A plan for installation and operation (PIO) of a gas pipeline tied into Åsgard Transport was submitted in 1997, and the field began producing gas in 2001. The estimated producing life was up to 2012.
Since Norne came on stream in 1997, both exploration and improved recovery have been purposefully pursued in the area. These efforts have resulted in several new discoveries, and reserves have risen substantially. Sixteen wildcats drilled in PL 128 alone have yielded 12 discoveries. Across the Nordland I-V areas, 60 wildcats have produced 28 discoveries since Norne. The two largest are 6507/5-1 Skarv (1998) and 6507/5-3 Ærfugl (2000). A total of more than 310 million scm oe has been found in the area, including roughly 195 million scm oe in the wake of the Norne discovery.
Tie-backs to Norne
The Alve, Marulk, Skuld and Urd fields have been tied back to Norne, and new tie-ins are continuously being evaluated. Collectively, this means that the Norne FPSO will continue producing beyond 2025 – twice as long as originally planned. More than 130 million scm oe will be produced through this facility in 2020 (figure 4.15).
Over the past five years, almost 80 per cent of production has come from the tied-back fields. Without these, operating the FPSO would not have been commercial. Socioeconomically profitable resources might have been lost if production had ceased too early. Resources from the new fields tied back to Norne can be produced commercially for many years. That has helped to extend tail production on Norne, yielding a far higher return from the field than originally expected.
Spare capacity on and continued profitable operation of the Norne FPSO creates a good basis for more exploration in the area. With fully depreciated infrastructure and cost-effective operation, very small discoveries can also become commercial.
That revitalises older discoveries in the area which have not been relevant for tie-back earlier. Such discoveries due to be tied back in coming years include 6507/3-8 (Gjøk) from 2009 and 6608/10-17S (Cape Vulture) from 2017. Other discoveries in the area could also be relevant here, providing a basis for extending profitable production from the Norne FPSO even further.
Figure 4.15 Historical and future production for Norne