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Growth in resources
The growth of oil and gas resources in the form of new discoveries was very
good on the Norwegian continental shelf until the mid-1980s. Figure 3.6 shows
how the total recoverable resources have increased from 1967 until today.
Initially, oil resources grew faster than gas resources, but after Troll Øst
was discovered in 1983, the quantities of oil and gas (in oil equivalents, see
Chapter 1) have been about equal. The figure illustrates how the growth in new
resources has been more modest since 1986. The Directorate's estimates of the
volume of undiscovered resources suggests that the growth in resources
experienced over the past few years is likely to continue. However, there is
considerable uncertainty as to what the investigation of the new exploration
areas in the Norwegian Sea will bring. If these areas contain large oil and gas
resources, we may see a new increase in the growth of resources. Figure 3.9
shows the growth in resources for the various exploration provinces on the
Norwegian continental shelf, which are divided into areas according to their
maturity, this being defined on the basis of well density and seismic
coverage.
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Fig. 3.6
Growth in resources for the whole continental
shelf. |
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Fig. 3.7
Number of discoveries per year. |
Discovery statistics
As of 31.12.96, 196 discoveries have been made on the Norwegian continental
shelf. Of these, 32 are so small that they cannot be expected to be developed
(resource class 6). This means that 164 profitable or possibly profitable
discoveries have been made. The number of new discoveries per year has shown a
general increase since Balder field was found in 1967 (Fig. 3.7).
This is naturally connected with the increase in drilling activity, but there
is no direct correlation between the number of discoveries and the quantities
of oil and gas that has been found. The largest discoveries are generally made
first. During the last 10 years, 85 discoveries have been made, the largest of
which are the 6406/2-1 discovery and the Norne field (Fig. 3.8). A number of
smaller discoveries have been made in the same period, resulting in an average
discovery size of around 13 million Sm3 o.e., 40% of which is gas.
The number of discoveries per licensing round show a clear decline from the
first round to today (Fig. 3.10). This is not related to the size of the area
allocated, but to the most prospective exploration areas being allocated early.
That the number of discoveries increases per year, but decreases per round,
also illustrates that extensive exploration is taking place in older production
licences.
Success rate
Of the 520 wildcat wells that have been drilled on the Norwegian continental
shelf, discoveries (profitable or possibly profitable) have been made in 164.
This gives a success rate of 32%. This is somewhat higher than, for example,
the UK shelf and the Gulf of Mexico (USA), but on a par with other important
offshore exploration areas, such as West Africa. The success rate has, however,
varied over a period of time, as shown in Figure 3.11. This figure illustrates
how the success was initially poor, but following the discovery of the Ekofisk
field it improved significantly. At the same time, exploration in the Frigg and
Sleipner areas gave results. Afterwards, the success rate fell off before again
receiving a boost when the exploration of the northern North Sea began and the
opportunity was opened up to explore north of 62° N. Subsequently, the
success rate, as measured on the basis of the, at any one time, last 50 wells,
has varied between 25% and 40%. In the last couple of years, it has again
increased and is now close to 50%. Of the 21 wildcat wells that were drilled in
1996, discoveries were made in 10, thus making the success rate for 1996 as
high as 48%. Figure 3.12 shows the trend in the success rate for the various
areas on the continental shelf. It is increasing in the southern part of the
Viking Graben, stable on the Halten and Dønna Terrace, and in the northern part
of the North Sea, and decreasing in the Central Trough.
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Success rate can be defined in many ways. Here, we have included all
discoveries in resource classes 0-5, i.e. those which are profitable or may be
profitable in the long run. If we include the discoveries in class 6, which are
not expected to be profitably developed, the success rate will be somewhat
higher. This may be called the "technical success rate". It is also
common to only consider those discoveries which are developed or are clearly
profitable today, i.e. classes 0-3. The success rate will then be lower.
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