Development of the NPD’s resource estimate
The NPD’s overall resource estimate has risen by 40 per cent since 1990. Total proven resources alter as a result of new discoveries and changes to estimates for individual fields. The latter can rise as a result of drilling appraisal wells, mapping, and conducting detailed studies which improve knowledge of reservoir size and recovery mechanisms.
Oil and gas resources
Many examples of a substantial increase in resources can be found on the Norwegian continental shelf (NCS). The estimated amount of oil and gas in many fields has more than doubled since the first recovery estimates were produced. Ekofisk and Troll made the biggest contributions to boosting resources in the 1990s.
The growth in 1990-96 derived both from a detailed review of project opportunities in fields and from the discovery of large fields such as Grane and Norne during this period. This was followed by a number of years with a steady rise in resources until the Johan Sverdrup discovery provided a sharp upturn.
A change made by the NPD in 2003 in the method used to calculate recovery from fields led to a reduction in recoverable gas resources. Subsequently unchanged, this approach now forms the basis for the NPD’s estimates and analyses..
Improved recovery from fields
Water injection, several new installations and an increased number of wells on Ekofisk mean that expected recovery is now more than three times above the estimate in the first development plan.
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.
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..
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.
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.
Contributors to this growth include:
- optimising recovery
- constructing new production facilities
- extending the producing life of Fields
- identifying new opportunities
- drilling many new wells.
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.
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.
IOR prize 2016: Groundbreaking technology on Åsgard