Ressursregnskapet per 31.12.1997 (kun engelsk)


The Norwegian Petroleum Directorate's (NPD) resource account gives an overview of the recoverable petroleum resources. Recoverable petroleum resources comprise both the original marketable and the remaining petroleum resources on the Norwegian shelf. The resource estimates are based on reports submitted annually by the operating companies, NPD evaluations for fields and discoveries and NPD estimates of undiscovered resources. Resources on the Norwegian continental shelf are classified in a system according to profitability and maturity, see the resource classification table.

Resources in Fields
As of 31 December 1997, 42 fields were in production on the Norwegian continental shelf, and development plans have been approved for eleven fields. In addition, three fields have ceased production. The original recoverable reserves (classes 0-2) comprise 3 600 million Sm3 of oil and NGL and 1 700 billion Sm3 of gas. Of this, about half of the oil and one third of the gas and NGL have been produced for sale. Oil resources from future projects (classes 3-6) are expected to correspond to two years oil production.

The main changes in oil reserves (classes 0-2) last year can be ascribed to the two new fields approved for development, Jotun and Oseberg Sør. Most of the other changes in these classes are ascribed to Troll II (Troll Oil), Eldfisk, Statfjord and Draugen. Oil resources in planning phases (classes 3 and 4) thus have been added to the reserves (classes 0-2). A similar increase has taken place in resource classes 3 and 4. Most of this increase in resources comes as a result of realising a part of the possible future measures to increase the recovery factor (class 8). A smaller part of the new oil resources came from re-evaluation of existing fields and discoveries which now are reported under fields.
For gas, the changes in reserves and in resources in planning phases are similar to those for oil.

50 per cent for oil and 75 per cent for gas
Based on the rate of present-day technological development and promising results from some recovery projects, the NPD believes there is reason to expect a further increase in the recovery from fields on the Norwegian continental shelf. A future average recovery factor of 50 per cent for oil fields and 75 per cent for gas fields is expected and set as today's goal. Resource class 8 comprises the difference between this possible future recovery and resources reported in classes 0 to 7.
Possible measures for increased oil recovery 1
Based on the reserves per 31.12.1997, the average recovery factor for oil is estimated at 43 per cent. Of the total oil resources in classes 3 - 8, the total potential for increased oil recovery (IOR) is 840 million Sm3, 210 million Sm3 of which stem from activities in planning phases. The other 630 million Sm3 is expected to come from possible future measures for increased oil recovery (class 8).
The IOR potential is dynamic. It changes as the resources changes their degree of maturity. Most of the increase in oil resources since last year comes as a result of realising part of the IOR potential.

The graph shows the increase in reserves and the corresponding in place oil from which the reserves are drained. The potential for IOR is based on a 50 per cent recovery factor for oil. This can be realised through improved technology. Improved techniques for exploitation, however, also increase the resources in place because of detailed mapping and addition of new drainable areas
1 Please refer to the report "Improved Oil Recovery (IOR)", order No. YA-793, for further details and explanation of terms.

Resources in Dicoveries
There are a total of 129 discoveries which have not yet been approved for development (see the tables on the last two pages), 17 of which were made in 1997. In addition, there are 21 discoveries for which resources are reported under other fields or discoveries.
The new discoveries in 1997 added 50 million Sm3 of oil, 50 million tonnes of NGL, and 200 billion Sm3 of gas to the resources. The new resources balance about one third of the oil produced and add considerably to the gas resources. The total recoverable resources in discoveries amount to 573 million Sm3 of oil and NGL and 931 billion Sm3 of gas. The discoveries may constitute as much as 30 per cent of the produced oil. Gas from discoveries may add another 60 per cent to the current gas reserves, making up more than 10 years of gas sales at 80 billion Sm3 of gas per year.


Undiscovered Resources
The undiscovered resources have an expected value of 1400 million Sm3 of oil and 2070 billion Sm3 of gas with an uncertainty range of as much as two to six billion Sm3 o.e. The new discoveries in 1997 open for a modest increase in the undiscovered resources, particularly for gas resources in the Norwegian Sea. For this reason the estimates for undiscovered resources have been kept on the same level as last year. The results from a new assessment of the undiscovered resources will be published in 1999. The discovery history indicates that the undiscovered resources will be found in many, generally small, discoveries. Using 1997, which was a very successful exploration year, as a reference, it may take as much as 30 years to realise most of the undiscovered oil potential.
It is important to bear in mind the large uncertainty of the resource estimates. The resource accounts presented here, give the expected values while the predicted uncertainty is shown in the graph.

The petroleum resource data that forms the basis of this article and the graphs within, are available for downloading. If utilized, please refer to the Norwegian Petroleum Directorate as the source.