Geological Survey of Denmark and Greenland Bulletin
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Nr. 4, Review of Survey activities 2003, pp. 13-16 |
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13
GESTCO is an acronym for European potential for the
Geological Storage of CO2 from fossil fuel combustion. The
project formed part of the ENERGIE Programme of the
European Union 5th Framework and was concluded in
2003. The Geological Survey of Denmark and Greenland
(GEUS) led the project, with the national geological surveys
of Belgium, France, Germany, Greece, the Netherlands,
Norway and UK as research partners (Fig. 1).
Geological Storage of CO2 from fossil fuel combustion. The
project formed part of the ENERGIE Programme of the
European Union 5th Framework and was concluded in
2003. The Geological Survey of Denmark and Greenland
(GEUS) led the project, with the national geological surveys
of Belgium, France, Germany, Greece, the Netherlands,
Norway and UK as research partners (Fig. 1).
The primary goal of the GESTCO project was to deter-
mine whether the geological storage of carbon dioxide cap-
tured at large industrial plants is a viable method of reducing
greenhouse gas emissions in Europe (Christensen 2000; Gale
et al. 2001; Christensen & Holloway 2003). This was evalua-
ted by a series of case studies that assessed the CO2 storage
potential of saline aquifers, geothermal reservoirs, coal seams
tured at large industrial plants is a viable method of reducing
greenhouse gas emissions in Europe (Christensen 2000; Gale
et al. 2001; Christensen & Holloway 2003). This was evalua-
ted by a series of case studies that assessed the CO2 storage
potential of saline aquifers, geothermal reservoirs, coal seams
and oil and gas reservoirs. The case study approach was used
so that currently available, largely theoretical, generic infor-
mation could be applied to real geological situations. In addi-
tion aspects of safety and environment, conflicts of using
underground space and public and stakeholder perception
were evaluated. Secondary goals of the GESTCO project were
to establish an inventory of major CO2 point sources in
Europe and a Decision Support System (DSS) to serve as an
economic analysis tool for CO2 storage in Europe.
so that currently available, largely theoretical, generic infor-
mation could be applied to real geological situations. In addi-
tion aspects of safety and environment, conflicts of using
underground space and public and stakeholder perception
were evaluated. Secondary goals of the GESTCO project were
to establish an inventory of major CO2 point sources in
Europe and a Decision Support System (DSS) to serve as an
economic analysis tool for CO2 storage in Europe.
Inventory of large CO2 point sources
Major industrial sources of CO2 in the participating coun-
tries were identified and compiled into a database. In almost
all countries, the major sources of CO2 are power plants,
tries were identified and compiled into a database. In almost
all countries, the major sources of CO2 are power plants,
Fig. 1. Map of Europe showing the participating
countries and offshore study areas included in
the GESTCO project.
Geological Survey of Denmark and Greenland Bulletin 4, 1316 (2004) © GEUS, 2004
Assessing the European potential for geological storage
of CO 2 : the GESTCO project
of CO 2 : the GESTCO project
Niels Peter Christensen and Michael Larsen
14
integrated steel plants, refineries/petrochemical complexes
and cement works. The exception is Norway, where many of
the major sources of CO2 are generators at offshore oil and
gas fields. The location and details of the sources of CO2 are
compiled into a Geographic Information system (GIS) ena-
bling qualified search routines.
and cement works. The exception is Norway, where many of
the major sources of CO2 are generators at offshore oil and
gas fields. The location and details of the sources of CO2 are
compiled into a Geographic Information system (GIS) ena-
bling qualified search routines.
In Denmark, the annual emission of greenhouse gases is
close to 60 Mt of which approximately half originates from
fossil fuel combustion related to power and heat generation.
Major CO2 point sources were identified based on yearly
reports to the Danish Energy Authority. These point sources
alone contribute 29 Mt CO2 of the total CO2 emission in
Denmark. The largest single source is the coal-fired power
plant Asnæsværket in Kalundborg, with an average yearly
emission of 5.8 Mt CO2 in the period 19941999. Conside-
ring CO2 sequestration from Asnæsværket could thus ac-
count for approximately half of the greenhouse gas reductions
required for Denmark in the Kyoto agreement (Larsen et al.
2003a).
fossil fuel combustion related to power and heat generation.
Major CO2 point sources were identified based on yearly
reports to the Danish Energy Authority. These point sources
alone contribute 29 Mt CO2 of the total CO2 emission in
Denmark. The largest single source is the coal-fired power
plant Asnæsværket in Kalundborg, with an average yearly
emission of 5.8 Mt CO2 in the period 19941999. Conside-
ring CO2 sequestration from Asnæsværket could thus ac-
count for approximately half of the greenhouse gas reductions
required for Denmark in the Kyoto agreement (Larsen et al.
2003a).
European storage capacities
Underground storage capacities in the case study areas were
evaluated by seismic mapping, analysis of well logs and reser-
voir simulation. The results are summarised in Christensen
& Holloway (2003). The major part of the mapped storage
capacity was related to deep saline aquifers in onshore and
nearshore sedimentary basins in Denmark, Germany, south-
ern UK and northern France. In the Netherlands and Bel-
gium the storage potential is primarily related to exhausted
gas fields and coalmines. A huge potential exists in aquifers
offshore Norway, and it is likely that very large additional off-
shore aquifer potential exists in British and Danish sectors of
the North Sea. The Greek storage potential is composed of
evaluated by seismic mapping, analysis of well logs and reser-
voir simulation. The results are summarised in Christensen
& Holloway (2003). The major part of the mapped storage
capacity was related to deep saline aquifers in onshore and
nearshore sedimentary basins in Denmark, Germany, south-
ern UK and northern France. In the Netherlands and Bel-
gium the storage potential is primarily related to exhausted
gas fields and coalmines. A huge potential exists in aquifers
offshore Norway, and it is likely that very large additional off-
shore aquifer potential exists in British and Danish sectors of
the North Sea. The Greek storage potential is composed of
aquifers as well as a few hydrocarbon fields. Significant stor-
age capacity is related to the gas and oil fields of northern
Europe, particularly in the North Sea and onshore in the
Netherlands and Germany.
age capacity is related to the gas and oil fields of northern
Europe, particularly in the North Sea and onshore in the
Netherlands and Germany.
Geological storage capacities in Denmark
The potential storage capacity in Denmark was evaluated
through case studies of onshore and nearshore saline aquifers,
and hydrocarbon fields of the Danish North Sea sector.
through case studies of onshore and nearshore saline aquifers,
and hydrocarbon fields of the Danish North Sea sector.
Deep saline aquifers
Large sedimentary basins of Late Palaeozoic Cenozoic age
are present in Denmark and provide a potential for CO2
storage. In the onshore or nearshore Danish area the reservoir
units comprise porous sandstone layers of the Lower Triassic
Bunter Sandstone Formation / Skagerrak Formation, the
Upper Triassic Lower Jurassic Gassum Formation, the
Middle Jurassic Haldager Sand Formation, and the Upper
Jurassic Lower Cretaceous Frederikshavn Formation. Map-
ping and initial description of these units has been under-
taken in the search for hydrocarbons and geothermal reservoirs
(cf. Nielsen et al. 2004, this volume).
are present in Denmark and provide a potential for CO2
storage. In the onshore or nearshore Danish area the reservoir
units comprise porous sandstone layers of the Lower Triassic
Bunter Sandstone Formation / Skagerrak Formation, the
Upper Triassic Lower Jurassic Gassum Formation, the
Middle Jurassic Haldager Sand Formation, and the Upper
Jurassic Lower Cretaceous Frederikshavn Formation. Map-
ping and initial description of these units has been under-
taken in the search for hydrocarbons and geothermal reservoirs
(cf. Nielsen et al. 2004, this volume).
The GESTCO aquifer study was focused on sandstone for-
mations within a depth range of 9002500 m, i.e. between
the depth required for CO2 to become a dense fluid and the
depth below which reservoir quality typically deteriorates due
to diagenetically induced reduction of porosity and permea-
bility.
the depth required for CO2 to become a dense fluid and the
depth below which reservoir quality typically deteriorates due
to diagenetically induced reduction of porosity and permea-
bility.
The total storage capacity of unconfined aquifers in
Denmark has been estimated to be 47 Gt of CO2, although
only a small part of the volume was related to structural clo-
sures (Holloway et al. 1996). In order to gain public and
only a small part of the volume was related to structural clo-
sures (Holloway et al. 1996). In order to gain public and
15
political acceptance, structural traps are considered essential,
at least initially, when considering storage onshore Denmark,
and consequently the GESTCO study was focused on eleven
large structures (Fig. 2; Table 1). These structures were mapped
from seismic surveys and evaluated using data from existing
deep wells to assess the storage potential (Larsen et al. 2003b).
at least initially, when considering storage onshore Denmark,
and consequently the GESTCO study was focused on eleven
large structures (Fig. 2; Table 1). These structures were mapped
from seismic surveys and evaluated using data from existing
deep wells to assess the storage potential (Larsen et al. 2003b).
Based on many years of experience from aquifer storage of
natural gas in Denmark, Germany and France, it is assumed
that 40% of the total pore volume within a trap could be
filled with CO2. This effective storage capacity will depend
on a number of parameters including the geometry of the
trap (e.g. difference in height between top point and spill
point), the number of injection wells, injection rates and
reservoir characteristics. The initial calculations carried out in
the present study suggest that the eleven structures alone may
provide storage for at least 16 Gt of CO2 (Table 1; Larsen et
al. 2003b). Note that almost two thirds of the calculated
aquifer storage capacity is present in the Thisted/Legind
structure.
that 40% of the total pore volume within a trap could be
filled with CO2. This effective storage capacity will depend
on a number of parameters including the geometry of the
trap (e.g. difference in height between top point and spill
point), the number of injection wells, injection rates and
reservoir characteristics. The initial calculations carried out in
the present study suggest that the eleven structures alone may
provide storage for at least 16 Gt of CO2 (Table 1; Larsen et
al. 2003b). Note that almost two thirds of the calculated
aquifer storage capacity is present in the Thisted/Legind
structure.
As well as a proper reservoir, a tight cap rock is needed
when considering underground storage of CO2. Geological
formations with good sealing properties are lacustrine and
marine mudrocks, evaporites and carbonates. In Denmark
the most important sealing rock type is marine mudstone,
which often forms units several hundred metres thick and is
present at several stratigraphic levels. In addition to the pri-
mary cap rock, chalk of Late Cretaceous Danian age forms
a possible secondary seal in most of the Danish area. The sea-
ling effect of the chalk is dependent on chemical reactions
between dissolved CO2 and the carbonate rock.
formations with good sealing properties are lacustrine and
marine mudrocks, evaporites and carbonates. In Denmark
the most important sealing rock type is marine mudstone,
which often forms units several hundred metres thick and is
present at several stratigraphic levels. In addition to the pri-
mary cap rock, chalk of Late Cretaceous Danian age forms
a possible secondary seal in most of the Danish area. The sea-
ling effect of the chalk is dependent on chemical reactions
between dissolved CO2 and the carbonate rock.
Detailed site surveys will be needed in order to test the
integrity of the seal at any future storage site.
Storage in oil and gas fields
Although the potential storage capacity of deep saline
aquifers is many times greater than that of hydrocarbon
structures, there are some distinct advantages of using deple-
ted hydrocarbon fields as storage sites. First, the hydrocarbon
fields have proved their capability to retain fluids and gases,
in many cases for millions of years. Secondly, the reservoir is
well understood due to intensive data gathering before and
during the productive life of the field, and finally infrastruc-
ture for the production and transport of fluids and gases is
already in place. With some modifications, this infrastructure
may often be re-usable for delivery and injection of CO2 for
storage.
aquifers is many times greater than that of hydrocarbon
structures, there are some distinct advantages of using deple-
ted hydrocarbon fields as storage sites. First, the hydrocarbon
fields have proved their capability to retain fluids and gases,
in many cases for millions of years. Secondly, the reservoir is
well understood due to intensive data gathering before and
during the productive life of the field, and finally infrastruc-
ture for the production and transport of fluids and gases is
already in place. With some modifications, this infrastructure
may often be re-usable for delivery and injection of CO2 for
storage.
The reserve figures for 14 chalk fields and three sandstone
fields of the Danish sector were included in the GESTCO
project (Christensen & Holloway 2003). These comprise
detailed estimates of the expected ultimate (initial) reserves,
and rounded figures for low and high case reserves as given by
the Danish Energy Authority (DEA 2002). The storage
capacity of hydrocarbon reservoirs is calculated from the
underground volume of ultimately recoverable oil or gas. The
calculation assumes that the entire underground volume of
recoverable hydrocarbons can be replaced by CO2. For gas
reservoirs, this is a straightforward assumption, since most
gas reservoirs are of a closed nature. Formation water (the
aquifer) does not significantly replace the drained gas during
project (Christensen & Holloway 2003). These comprise
detailed estimates of the expected ultimate (initial) reserves,
and rounded figures for low and high case reserves as given by
the Danish Energy Authority (DEA 2002). The storage
capacity of hydrocarbon reservoirs is calculated from the
underground volume of ultimately recoverable oil or gas. The
calculation assumes that the entire underground volume of
recoverable hydrocarbons can be replaced by CO2. For gas
reservoirs, this is a straightforward assumption, since most
gas reservoirs are of a closed nature. Formation water (the
aquifer) does not significantly replace the drained gas during
Fig. 2. Map showing the position
and outline of the eleven structural
closures mapped in the Danish
aquifer case study of the GESTCO
project. Black dots indicate the
position of deep exploration wells
used in the evaluation of the
reservoirs. Modified from Larsen
et al. (2003a).
16
the producing field life. For oil reservoirs, it is assumed that
the amount of CO2 that can be stored in the reservoir is
approximately 30% of the oil initially in place. Since the
Ultimate Recovery (UR) of most oil fields (as initially re-
ported) also approximates 3035%, the storage capacity can
be approximated by the initial proven reserves (or UR). In
addition to the volumetric estimates special concern is
needed when considering storage of CO2 in chalk, as chem-
ical and physical reactions are likely to occur between CO2
in solution and carbonate rocks.
the amount of CO2 that can be stored in the reservoir is
approximately 30% of the oil initially in place. Since the
Ultimate Recovery (UR) of most oil fields (as initially re-
ported) also approximates 3035%, the storage capacity can
be approximated by the initial proven reserves (or UR). In
addition to the volumetric estimates special concern is
needed when considering storage of CO2 in chalk, as chem-
ical and physical reactions are likely to occur between CO2
in solution and carbonate rocks.
Based on the above assumptions, the Danish storage
capacity for existing oil and gas fields is estimated to be 629
Mt CO2. Of this, 452 Mt can replace natural gas, while 176
Mt can replace oil (Christensen & Holloway 2003). How-
ever, all of the investigated fields of the Danish North Sea are
in the production phase, and CO2 injection will probably
not be possible in the near future unless applied through En-
hanced Oil Recovery (EOR) operations. The EOR option of
the North Sea is currently under investigation and prelimi-
nary results have been presented by Markussen et al. (2003).
The vision of the project is to capture CO2 from the Danish
power plants and export it through an extensive pipeline sy-
stem to the offshore industry. Implementation of the EOR
technology would have great impact on the lifecycle of
Danish oil and gas production.
Mt CO2. Of this, 452 Mt can replace natural gas, while 176
Mt can replace oil (Christensen & Holloway 2003). How-
ever, all of the investigated fields of the Danish North Sea are
in the production phase, and CO2 injection will probably
not be possible in the near future unless applied through En-
hanced Oil Recovery (EOR) operations. The EOR option of
the North Sea is currently under investigation and prelimi-
nary results have been presented by Markussen et al. (2003).
The vision of the project is to capture CO2 from the Danish
power plants and export it through an extensive pipeline sy-
stem to the offshore industry. Implementation of the EOR
technology would have great impact on the lifecycle of
Danish oil and gas production.
Conclusions
The inventory of major point sources of CO2 and the geo-
logical storage potential mapped in the GESTCO project
indicate that the eight European countries could make a sig-
nificant impact on their national CO2 emissions by captu-
ring the emissions from a relatively small number of the
largest point sources and storing them underground.
logical storage potential mapped in the GESTCO project
indicate that the eight European countries could make a sig-
nificant impact on their national CO2 emissions by captu-
ring the emissions from a relatively small number of the
largest point sources and storing them underground.
In Denmark, mapping of geological structures suitable for
underground storage of CO2 suggests that enough storage
volume is present within the subsurface to store several hun-
dred years of total CO2 emissions from Danish industry and
power production. Detailed site surveys and risk analysis,
including long term monitoring, are needed to validate these
storage capacities and should be the focus of future studies.
volume is present within the subsurface to store several hun-
dred years of total CO2 emissions from Danish industry and
power production. Detailed site surveys and risk analysis,
including long term monitoring, are needed to validate these
storage capacities and should be the focus of future studies.
Acknowledgements
The project formed part of the ENERGIE Programme of the European
Union 5th Framework Programme for Research & Development, Project
No. ENK6-CT-1999-00010, and was 50% funded by the Programme.
Union 5th Framework Programme for Research & Development, Project
No. ENK6-CT-1999-00010, and was 50% funded by the Programme.
In addition to the principal research partners, valuable contributions
to the project were made by the Flemish Institute for Technological
Research (Vito, Belgium), Public Power Corporation of Greece, Com-
pagnie Française de Geothermie (CFG), Danish Oil and Natural Gas
Company (DONG), CE-Transform (the Netherlands) and the Tyndall
Centre (UK).
Research (Vito, Belgium), Public Power Corporation of Greece, Com-
pagnie Française de Geothermie (CFG), Danish Oil and Natural Gas
Company (DONG), CE-Transform (the Netherlands) and the Tyndall
Centre (UK).
Further contributions to the project were given by BEB (now EMPG),
BP, Danish Energy Authority, Gaz de France, IEA Greenhouse Gas R & D
Programme, Norsk Hydro, Norwegian Petroleum Directorate, Shell,
Statoil, Total-FinaElf, the UK Department of Trade and Industry, and
Vattenfall.
Programme, Norsk Hydro, Norwegian Petroleum Directorate, Shell,
Statoil, Total-FinaElf, the UK Department of Trade and Industry, and
Vattenfall.
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Authors' address
Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark. E-mail: npc@geus.dk
Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark. E-mail: npc@geus.dk
