a further increase in production from thereon is not possible. Optimistic scenarios suggest that additional reserves
can be obtained by a more effective oil recovery from producing fields, the usage of unconventional resources, and
that significant additional oil – and also natural gas – is
found in the frontier areas of the Arctic and the deepwater
areas of the continental margins. It is not only the geology
and reservoir performance that defines if the targeted
resources are exploited, it also depends on future demand
and prices, the availability of new technologies, the infrastructure, environmental issues, and political and regulatory considerations. The impact of carbon dioxide on the
climate may result in efforts to limit the extensive use of
coal, oil, and natural gas.
At present, renewable energy represents only a minor
percentage of global primary energy consumption, but it
is growing very rapidly. Renewable energy costs continue
to drop as a result of technological innovation and mass
production. A main driving force to expand the use of
renewable energy is its relatively low impact on climate
and on the environment.
Offshore renewable energy
In order to decrease emissions of carbon dioxide into the
atmosphere, serious efforts are undertaken to develop
renewable energy sources.
Offshore wind farms boast some advantages in comparison to onshore installations: the wind blows more constantly most of the time, and the demands on “land” use
are less competitive offshore. Technical challenges
include the foundations of the wind turbines installed in
shallow water. This requires detailed information of the
sediment distribution not only on the surface but also
some tens of meters below the seafloor, where peat horizons or shallow gas may occur. Sediment movement
may restrict the foundations of wind turbines. Many shallow areas of the sea are important habitats for the reproduction of marine mammals, fishes, and benthic
invertebrates. These biological communities are not only
disturbed during the construction but also may be
perturbed during operation.
As the number of offshore wind turbines installed in the
marine realm increases, integrating them into the existing
power supply structures will become increasingly important. While the present total capacity of offshore wind
farms is in the megawatt range, plans call for much larger
offshore units. A substantial increase in the amount of
wind power will have to be integrated into national and
international electricity grids. The next step in offshore
wind farming will lead to installation in deeper and more
remote areas far away from the coast. Since the wind
blows more strongly and comparatively smaller areas are
needed, electricity generation with wind turbines out at
sea is particularly attractive. The organizational and technological requirements are however significantly higher
than on land, i.e., great distances to the coast, ocean depths
of up to 40 m, and the harsh sea climate with humid, salty
air, strong temperature fluctuations, severe storms,
squalls, and high wave loads (see Ocean Margin Systems).
The development of wave power devices is still in progress and so far only prototypes are being tested at sea.
With the recent worldwide growth in interest in renewables, wave energy may also become more important.
Wave power devices harness the continuous energy of
waves to generate electricity. These may be installed at
the shoreline, nearshore, or offshore. Tidal power plants
convert the potential energy or the power of currents
between low and high tide into electricity. The major
advantage of this renewable energy is that tides are more
predictable than other renewable energy sources. However, regions with sufficiently high tidal ranges or flow
velocities are limited. Further technological improvements are necessary to bring production costs of tidal
energy down to competitive levels.
Other ocean energy sources that are at present not
widely used include ocean thermal energy, making use
of the small temperature difference between deep and
shallow water, salinity gradient energy which becomes
available from the difference in the salt concentration
between seawater and river water, and the energy of
marine currents.
Fossil energy resources
The most important offshore energy resources are oil and
gas. Given the huge onshore resources, coal and uranium
are not expected to be produced in the coming decades
from offshore areas.
Petroleum classifications, reserves, and resources
Oil and gas are trapped in subsurface geological structures
and the volumes cannot be physically examined or
inspected. Regional estimates are based on data that provide indirect evidence of the scale of the resource base.
Classification usually starts with a petroleum play, which
is a concept to recognize patterns in petroleum occurrence
that can help to predict the results of future exploration.
Plays are characterized by the presence or prediction of
source rocks, reservoirs, and seals. Hydrocarbon generation in sedimentary basins (see Marine Sedimentary
Basins) is controlled by the source rock, its lithology,
facies, distribution, and organic content and by the tectonic evolution of the basin. The amount of organic matter
in the source rock depends on the production and input of
organic matter during sedimentation (see Paleoceanography) but also on preservation or degradation during
diagenesis. The increasing heat and pressure during subsidence and continuing sedimentation control the generation of hydrocarbons in the source rock, while porosity
and permeability control the migration of hydrocarbons
from the source rock into a reservoir. The potentiality of
sedimentary basins thus depends also on subsidence,
burial, and physical conditions such as pressure and heat
flow. Porous structures for accumulations and seals
218
ENERGY RESOURCES
can be obtained by a more effective oil recovery from producing fields, the usage of unconventional resources, and
that significant additional oil – and also natural gas – is
found in the frontier areas of the Arctic and the deepwater
areas of the continental margins. It is not only the geology
and reservoir performance that defines if the targeted
resources are exploited, it also depends on future demand
and prices, the availability of new technologies, the infrastructure, environmental issues, and political and regulatory considerations. The impact of carbon dioxide on the
climate may result in efforts to limit the extensive use of
coal, oil, and natural gas.
At present, renewable energy represents only a minor
percentage of global primary energy consumption, but it
is growing very rapidly. Renewable energy costs continue
to drop as a result of technological innovation and mass
production. A main driving force to expand the use of
renewable energy is its relatively low impact on climate
and on the environment.
Offshore renewable energy
In order to decrease emissions of carbon dioxide into the
atmosphere, serious efforts are undertaken to develop
renewable energy sources.
Offshore wind farms boast some advantages in comparison to onshore installations: the wind blows more constantly most of the time, and the demands on “land” use
are less competitive offshore. Technical challenges
include the foundations of the wind turbines installed in
shallow water. This requires detailed information of the
sediment distribution not only on the surface but also
some tens of meters below the seafloor, where peat horizons or shallow gas may occur. Sediment movement
may restrict the foundations of wind turbines. Many shallow areas of the sea are important habitats for the reproduction of marine mammals, fishes, and benthic
invertebrates. These biological communities are not only
disturbed during the construction but also may be
perturbed during operation.
As the number of offshore wind turbines installed in the
marine realm increases, integrating them into the existing
power supply structures will become increasingly important. While the present total capacity of offshore wind
farms is in the megawatt range, plans call for much larger
offshore units. A substantial increase in the amount of
wind power will have to be integrated into national and
international electricity grids. The next step in offshore
wind farming will lead to installation in deeper and more
remote areas far away from the coast. Since the wind
blows more strongly and comparatively smaller areas are
needed, electricity generation with wind turbines out at
sea is particularly attractive. The organizational and technological requirements are however significantly higher
than on land, i.e., great distances to the coast, ocean depths
of up to 40 m, and the harsh sea climate with humid, salty
air, strong temperature fluctuations, severe storms,
squalls, and high wave loads (see Ocean Margin Systems).
The development of wave power devices is still in progress and so far only prototypes are being tested at sea.
With the recent worldwide growth in interest in renewables, wave energy may also become more important.
Wave power devices harness the continuous energy of
waves to generate electricity. These may be installed at
the shoreline, nearshore, or offshore. Tidal power plants
convert the potential energy or the power of currents
between low and high tide into electricity. The major
advantage of this renewable energy is that tides are more
predictable than other renewable energy sources. However, regions with sufficiently high tidal ranges or flow
velocities are limited. Further technological improvements are necessary to bring production costs of tidal
energy down to competitive levels.
Other ocean energy sources that are at present not
widely used include ocean thermal energy, making use
of the small temperature difference between deep and
shallow water, salinity gradient energy which becomes
available from the difference in the salt concentration
between seawater and river water, and the energy of
marine currents.
Fossil energy resources
The most important offshore energy resources are oil and
gas. Given the huge onshore resources, coal and uranium
are not expected to be produced in the coming decades
from offshore areas.
Petroleum classifications, reserves, and resources
Oil and gas are trapped in subsurface geological structures
and the volumes cannot be physically examined or
inspected. Regional estimates are based on data that provide indirect evidence of the scale of the resource base.
Classification usually starts with a petroleum play, which
is a concept to recognize patterns in petroleum occurrence
that can help to predict the results of future exploration.
Plays are characterized by the presence or prediction of
source rocks, reservoirs, and seals. Hydrocarbon generation in sedimentary basins (see Marine Sedimentary
Basins) is controlled by the source rock, its lithology,
facies, distribution, and organic content and by the tectonic evolution of the basin. The amount of organic matter
in the source rock depends on the production and input of
organic matter during sedimentation (see Paleoceanography) but also on preservation or degradation during
diagenesis. The increasing heat and pressure during subsidence and continuing sedimentation control the generation of hydrocarbons in the source rock, while porosity
and permeability control the migration of hydrocarbons
from the source rock into a reservoir. The potentiality of
sedimentary basins thus depends also on subsidence,
burial, and physical conditions such as pressure and heat
flow. Porous structures for accumulations and seals
218
ENERGY RESOURCES