trapping the generated hydrocarbons are prerequisites for
petroleum reservoirs.
The amount of the producible and usable energy
resources in a specific setting depends on the geological
conditions of the deposits, the state of the scientific and
technical knowledge, the technological potential of development and production, as well as the economic and political requirements. Correspondingly, the intentions and
methods used to assess the amounts of energy resources
considerably vary. There is one general distinction that
applies to all energy resource statistics: the distinction
between those energy resources whose exploitation is
regarded as proven (reserves) and those energy resources
whose existence is only assumed or whose production is
currently not considered economically feasible
(resources) (Andruleit et al., 2013). Oil and gas reserves
are defined as the volumes that have been accurately
recorded and can be commercially recovered in the future
using the current technical possibilities. Resources are
those amounts of oil and gas which have been geologically
proven, but which at the present time cannot be economically recovered, and the amounts which have not been
proven, but which can be expected for geological reasons
in the concerned area. There is a dynamic boundary
between resources and reserves and, e.g., variations in
the price or technical advances will convert resources to
reserves and vice versa.
There is no common definition to subdivide oil and gas
into conventional and unconventional occurrences. Probably most commonly classified are conventional occurrences as the ones which can be exploited by standard
exploration and production methods. According to this
definition, the development and use of unconventional
occurrences requires alternative technologies. Aspects of
economic efficiency, or whether the individual deposit is
already used for production, are not considered in this definition. However, once an alternative technology becomes
established, earlier unconventional resources may be classified as conventional.
Giant oil and gas fields (those with 79,000,000 m
3
(500 million barrels) of ultimately recoverable oil or gas
equivalent) account for about 40 % of the world’s petroleum reserves (Halbouty, 2001). The majority of the
world’s giant oil and gas fields exist in two characteristic
tectonic settings – passive continental margin and rift
structures – highlighting the potential impact of future offshore resources. Passive continental margins are the outcome of a “successful rift” which resulted in continental
separation and the formation of new oceanic crust, while
in failed rifts, extension terminated at some stage during
the evolution to leave an aborted rift (see “Plate
Tectonics”).
Offshore petroleum exploration and production
Evolution of offshore petroleum exploration
Offshore drilling for oil in seawater began off the US West
Coast, just south of Santa Barbara, California, as early as
1896. Significant offshore exploration, however, only
started in the middle of the twentieth century. In the Gulf
of Mexico, off the Louisiana coast, the first productive
wells were installed in the 1940s. However, water depth
was still far less than 100 m. 1947 is commonly used as
the year defining the initiation of offshore drilling beyond
the sight of land. From then on, exploration also began in
the Caspian Sea, the Persian Gulf, the Arabian Sea off
India, and the North Sea. Some discoveries were made
in China and Australia. Exploration peaked in 1982 when
nearly 200 new fields were discovered. In 1986, the first
deepwater field (>1,500 m) was discovered in the Gulf
of Mexico (Mensa gas field). Based on the dominant discovery pattern of the 1990s, the deep water became the
primary new exploration target for petroleum companies
(Esser, 2001). Several new discoveries were made up until
the twenty-first century, but the number of new discoveries never again reached the high numbers of 1982. In
2000, when the oil price dropped to about 12$/barrel,
almost all coastal countries bordering passive continental
margins were involved in deepwater exploration. Until
this time, offshore exploration had been concentrated in
shallow waters. Only about 40 production rigs were
installed in waters exceeding 500 m depth, accounting
for about 3 % of global oil production. More than 2000
new discoveries were made since that time, the most
important being in the Gulf of Mexico, offshore Brazil,
Iraq, and Australia. Global deepwater production has
more than tripled since 2000, and in 2010, about 10 % of
the global oil production came from deepwater wells.
The fact that more than 50 % of newly discovered reserves
are found in deep waters over the last few years indicates
that the proportion of deepwater oil and gas production
will grow further in the near future.
Deepwater petroleum
There is a wide range of definitions for deep water. The
most widespread definition refers to water depths greater
than 500 m. That is about the depth at which traditional
development platforms cannot be implemented. Deepwater exploration came along with major improvements of
exploration and production methods. Major challenges
include 3-D seismic data acquisition (see Technology in
Marine Geosciences) and advanced seismic processing
integrated with interpretation workstations capable of handling and visualizing large 3-D volumes, the use of seismic amplitudes for hydrocarbon and reservoir prediction,
methodologies for basin analysis and predictive stratigraphy (see Deep-sea Sediments), and drilling and logging
tools (dynamically positioned drill ships, automated pipe
handling systems, horizontal drilling and well completions, and subsea systems).
Offshore oil production represents about one-third of
present world oil output. Globally, there are more than
150 major deepwater fields that have the potential to come
on-stream over the next few years. Drilling activity has
particularly increased in the “golden triangle” of Brazil,
ENERGY RESOURCES
219
petroleum reservoirs.
The amount of the producible and usable energy
resources in a specific setting depends on the geological
conditions of the deposits, the state of the scientific and
technical knowledge, the technological potential of development and production, as well as the economic and political requirements. Correspondingly, the intentions and
methods used to assess the amounts of energy resources
considerably vary. There is one general distinction that
applies to all energy resource statistics: the distinction
between those energy resources whose exploitation is
regarded as proven (reserves) and those energy resources
whose existence is only assumed or whose production is
currently not considered economically feasible
(resources) (Andruleit et al., 2013). Oil and gas reserves
are defined as the volumes that have been accurately
recorded and can be commercially recovered in the future
using the current technical possibilities. Resources are
those amounts of oil and gas which have been geologically
proven, but which at the present time cannot be economically recovered, and the amounts which have not been
proven, but which can be expected for geological reasons
in the concerned area. There is a dynamic boundary
between resources and reserves and, e.g., variations in
the price or technical advances will convert resources to
reserves and vice versa.
There is no common definition to subdivide oil and gas
into conventional and unconventional occurrences. Probably most commonly classified are conventional occurrences as the ones which can be exploited by standard
exploration and production methods. According to this
definition, the development and use of unconventional
occurrences requires alternative technologies. Aspects of
economic efficiency, or whether the individual deposit is
already used for production, are not considered in this definition. However, once an alternative technology becomes
established, earlier unconventional resources may be classified as conventional.
Giant oil and gas fields (those with 79,000,000 m
3
(500 million barrels) of ultimately recoverable oil or gas
equivalent) account for about 40 % of the world’s petroleum reserves (Halbouty, 2001). The majority of the
world’s giant oil and gas fields exist in two characteristic
tectonic settings – passive continental margin and rift
structures – highlighting the potential impact of future offshore resources. Passive continental margins are the outcome of a “successful rift” which resulted in continental
separation and the formation of new oceanic crust, while
in failed rifts, extension terminated at some stage during
the evolution to leave an aborted rift (see “Plate
Tectonics”).
Offshore petroleum exploration and production
Evolution of offshore petroleum exploration
Offshore drilling for oil in seawater began off the US West
Coast, just south of Santa Barbara, California, as early as
1896. Significant offshore exploration, however, only
started in the middle of the twentieth century. In the Gulf
of Mexico, off the Louisiana coast, the first productive
wells were installed in the 1940s. However, water depth
was still far less than 100 m. 1947 is commonly used as
the year defining the initiation of offshore drilling beyond
the sight of land. From then on, exploration also began in
the Caspian Sea, the Persian Gulf, the Arabian Sea off
India, and the North Sea. Some discoveries were made
in China and Australia. Exploration peaked in 1982 when
nearly 200 new fields were discovered. In 1986, the first
deepwater field (>1,500 m) was discovered in the Gulf
of Mexico (Mensa gas field). Based on the dominant discovery pattern of the 1990s, the deep water became the
primary new exploration target for petroleum companies
(Esser, 2001). Several new discoveries were made up until
the twenty-first century, but the number of new discoveries never again reached the high numbers of 1982. In
2000, when the oil price dropped to about 12$/barrel,
almost all coastal countries bordering passive continental
margins were involved in deepwater exploration. Until
this time, offshore exploration had been concentrated in
shallow waters. Only about 40 production rigs were
installed in waters exceeding 500 m depth, accounting
for about 3 % of global oil production. More than 2000
new discoveries were made since that time, the most
important being in the Gulf of Mexico, offshore Brazil,
Iraq, and Australia. Global deepwater production has
more than tripled since 2000, and in 2010, about 10 % of
the global oil production came from deepwater wells.
The fact that more than 50 % of newly discovered reserves
are found in deep waters over the last few years indicates
that the proportion of deepwater oil and gas production
will grow further in the near future.
Deepwater petroleum
There is a wide range of definitions for deep water. The
most widespread definition refers to water depths greater
than 500 m. That is about the depth at which traditional
development platforms cannot be implemented. Deepwater exploration came along with major improvements of
exploration and production methods. Major challenges
include 3-D seismic data acquisition (see Technology in
Marine Geosciences) and advanced seismic processing
integrated with interpretation workstations capable of handling and visualizing large 3-D volumes, the use of seismic amplitudes for hydrocarbon and reservoir prediction,
methodologies for basin analysis and predictive stratigraphy (see Deep-sea Sediments), and drilling and logging
tools (dynamically positioned drill ships, automated pipe
handling systems, horizontal drilling and well completions, and subsea systems).
Offshore oil production represents about one-third of
present world oil output. Globally, there are more than
150 major deepwater fields that have the potential to come
on-stream over the next few years. Drilling activity has
particularly increased in the “golden triangle” of Brazil,
ENERGY RESOURCES
219