On Troll, oil reserves are now four times greater than had been assumed when the decision to develop was taken. The main reason is continuous development of the field, with a number of new installations and a commitment to drilling and completion technology. At the same time, gas recovery has increased through measures to reduce reservoir pressure.

Johan Sverdrup was estimated to be a medium-sized oil field in 2010, with opportunities for further growth through continued drilling activity. It is now more than 20 times larger than that initial estimate

Reasons for reductions in estimate resources

Expected recoverable resources can also be reduced. This could occur if resources in place prove to be smaller than first thought, or because producing the field is more complicated than predicted.

Resources can also decline if projects are not regarded as sufficiently profitable. In most cases, the resource base for projects which are not implemented remains in place. New technology, other concepts or changes in profitability calculations may allow such resources to be developed later.

Biggest increase for oil

Growth in the resource estimate has primarily been driven by an increase in the estimated quantity of oil. The latter accounts for more than 85 per cent of remaining proven fluids. Natural gas liquids (NGL) and condensate are the other fluid products.

Proven fluid resources in 2016 were almost the same as the estimated figure in 2003, and much more is expected to be found. Proven resources increased by 20 per cent or 1.9 billion scm oe over the same period.

Resource accounts for 2003 and 2016 for liquids and gas respectively.

The estimate for total gas resources has risen marginally since 2003. Sold gas and gas reserves add up to about the same figure as proven gas reserves in 2003. Undiscovered and contingent  gas resources are slightly higher than the estimated undiscovered quantity in 2003.

New fields contribute most

About 70 per cent of the growth since 2003 has come from discoveries made during the period. The remainder derives primarily from measures implemented or planned to improve recovery from the fields.

The figure below shows the status for and volume of discoveries since 2003. Fluids account for 75 per cent of proven petroleum resources. More than half the fluids and a third of the gas discovered since 2003 have been sanctioned for Development..

Status and volume of resources discovered since 2003.

Big oil discoveries

Johan Sverdrup, the biggest oil discovery after 2003, has reserves of 298 million scm oe in its first development stage. In addition, plans call for substantial resources to be developed in subsequent phases on the field.

A number of other large oil discoveries have also been made,  including 7220/8-1 Johan Castberg and 7324/8-1 Wisting in the Barents Sea. Both are expected to yield more than 50 million scm of oil.

Gas discoveries

The biggest gas discovery since 2003 is 6406/9-1 Linnorm, with 24.9 million scm oe of recoverable resources. Dvalin is the largest sanctioned for development, with recoverables of 18.8 million scm oe. A plan for development and operation (PDO) was submitted in 2016..

Projects on fields contribute to reserve growth

Measures and new projects on the fields added more than 500 million scm oe to recoverable resources in 2003-16.

 Substantial efforts are devoted to continued development of fields. That helps to extend their producing life and improve recovery

Contributors to this growth include:

• optimising recovery
• constructing new production facilities
• extending the producing life of Fields
• identifying new opportunities
• drilling many new wells.

READ MORE: Projects on fields yield substantial reserve growth

Production forecast

All the resources in the accounts are expected to be produced, but the future level of production will depend on such factors as:

• which measures have been implemented on the Fields
• which discoveries are sanctioned for development, and when they are due to come on stream
• which new discoveries have been made, how large they are, and how and when they are developed.

 Production history and forecasts broken down by maturity of resources, 2010-30. As the figure shows, the level of production is expected to be relatively stable in coming years.

According to the production forecast, output is expected to remain at the level maintained so far in this decade. The contribution from petroleum sanctioned for development will stay at a high and stable level over the next five years. While the level of production will be maintained in the subsequent five years, the contribution from resources in fields and discoveries yet to be sanctioned for development will increase. Undiscovered resources are expected to acquire greater significance for production towards 2030.

IOR prize for 2016

The increase in the volume of gas resources derives primarily from action to reduce reservoir pressure. Such measures – like subsea compression on Åsgard, for example – are normally implemented when most of the gas which can be recovered without additional support has been produced. Work by the Åsgard licensees on subsea compression won them the NPD’s prize for improved oil recovery (IOR) in 2016.

When presenting the IOR prize for 2016, NPD director general Bente Nyland (third from right) praised the winners for their willingness to accept risk and the ability to think innovatively at all levels.