ANNUAL REPORT 2003
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Energy resources
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Procuring knowledge for continued exploration and exploitation of the energy resources of Denmark and Greenland
Jurassic heavy-weighter
A comprehensive book with 948 pages was published in 2003: "The Jurassic of
Denmark and Greenland". The book describes the geological development in a
period of the Earth's history that is of great significance to society today. The
Jurassic strata are thus important source rocks and reservoir rocks for oil and gas
and also constitute an important resource for storage of CO2 and gas and for
exploitation of geothermal energy. Through 28 articles, the reader is presented to
the results of intensive Jurassic research in the late 1980s and the 1990s. This includes
a detailed chronostratigraphic and biostratigraphic overview of the Jurassic in
north-western Europe as well as a number of stratigraphic, sedimentological, structural
and geochemical studies of the Jurassic strata in Denmark and East Greenland.
The Jurassic strata in Danish territory are primarily found in the subsurface
and research here is based on innumerable wells and seismic data collected over
more than 30 years of oil explorations. In contrast to this, the Jurassic strata in
East Greenland can be studied in impressive exposures along fjords or mountain
sides, and East Greenland is regarded as a unique field laboratory, particularly
among geologists working with exploration of the Norwegian shelf.
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Article 76
- short text with far-reaching consequences
During the course of 2004, Denmark is expected to ratify the United Nations
Convention on the Law of the Sea which makes it possible for coastal states to
claim rights to the resources of the subsurface and seabed beyond the 200 nautical
mile limit. Off the coasts of Greenland and the Faeroe Islands there are five areas
where it may be possible to make such claims. The coastal state has 10 years from
the time of ratification to document any claims by means of geodetic, bathymetric,
geophysical and geological data. The Danish Finance Act has now appropriated
funds to carry out these surveys, and in 2003, seismic data were collected at sea
north of the Faeroe Islands and south of Greenland in order to explore the thickness
of sedimentary rocks. Article 76 of the Convention on the Law of the Sea
defines the conditions required for making claims beyond 200 nautical miles, and
the occurrence of thick sedimentary rocks is one of them. A requirement for any
claim is that there is a natural prolongation of the land territory beyond 200 nautical
miles - a factor that can give rise to diverse geological considerations. Although
article 76 is only one page of text, it will form the basis of one of the main initiatives
for GEUS in the next decade.
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New calculations of oil migration in the North Sea limestone
GEUS completed a project which, by means of model calculations, describes the processes when limestone reservoirs in
the North Sea are charged with oil. It can take millions of
years to fill the microscopic pores in the limestone, so the
model is not only intended to calculate the migration of oil
and water in the pores but also to take into account that,
over many years, the reservoir will slowly sink further down
into the subsurface under a continued compression. The project showed that, by means of simple and geological assumptions, it is possible to calculate the filling history for limestone
reservoirs. Thus, it has been possible to calculate a hydrocarbon distribution in the Kraka Field and in the Dan-Halfdan
Field system which has great similarity to the current hydrocarbon distribution data from oil wells. As a consequence of
the constant subsidence of the area, water is being pressed
through the limestone very slowly. This migration may move
the oil towards the flanks of up-faulted limestone structures;
places where oil is not normally expected to be found.
Further model calculations may help identify new areas in the
North Sea that have not previously been relevant in connection with oil. The project is funded by the Danish Energy
Authority's Energy Research Programme.
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Possible geological storage of CO2
Storage of CO2 in the subsurface is one method of
reducing greenhouse gas emissions into the atmosphere. In 2003, GEUS completed the EU project GESTCO which looked into the possibilities of subsurface
storage of CO2 in eight EU Member States. The studies show that in Denmark it is possible to store 16
billion tonnes of CO2. The calculation only includes
the most obvious geological possibilities, but the storage capacity nevertheless corresponds to more than
400 years of CO2 emissions at the current level of
coal and natural gas consumption. In addition, GEUS
is participating in projects about storage of CO2 in
the United Kingdom and in the Canadian Weyburn oil
field where it is not only environmental benefits that
come from the CO2 injection but also in terms of
increased oil extraction from the field because of the
thinning effect of the gas on the oil. Finally, GEUS is
participating in the international research project
SACS which monitors and models storage of one million tonnes CO2 per year under the Norwegian
Sleipner gas field in the North Sea. This corresponds
to 3 per cent of total Norwegian CO2 emissions. This
project is currently the only one of its kind where
CO2 is stored in the subsurface merely out of environmental concerns.
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New map of the limestone in Denmark
The limestone in the Danish subsurface is a very
important reservoir rock for oil and gas, but in
several places in Denmark, we also get drinking
water from the limestone strata. In the North
Sea, we find the limestone several kilometres
down in the subsurface, and in eastern Denmark, the rocks are exposed, for example in the
cliffs at Stevns and on Møn. In 2003, GEUS prepared a new detailed map of the top and depth
of the carbonate rocks under the entire Danish
territory from the central part of the North Sea
to the easternmost part of Denmark. The map,
which is prepared on a scale of 1:750 000, is the
first collated record of rock types important to
society, and it builds on a collection of comprehensive seismic data, previously published maps
and information from oil and gas and water
wells. The map covers the carbonate rocks and
similar geological formations deposited in the
period from the Cenomanian to the Danian.
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