Chapter 19
4D Seismic
Martin Landrø
19.1 Introduction
The term 4D seismic reflects that calendar time
represents the fourth dimension. A more precise term is
repeated seismic, because that is actually what is done: a
seismic survey over a given area (oil/gas field) is repeated
in order to monitor production changes. Time-lapse seismic is another term used for this. For some reason, the
term 4D seismic is most common, and we will therefore
use it here. It is important to note that if we repeat 2D
surveys, it is still denoted 4D seismic according to this
definition. Recent examples of such surveys are repeated
2D lines acquired over the Troll gas province.
Currently there are three major areas where 4D
seismic is applied. Firstly, to monitor changes in a
producing hydrocarbon reservoir. This is now an
established procedure being used worldwide. So far,
4D seismic has almost exclusively been used for clastic
reservoirs and only rarely for carbonate reservoirs. This
is because carbonate reservoirs (apart from those in
porous chalk) are stiffer, and the effect on the seismic
parameters of substituting oil with water is far less
pronounced. Secondly, 4D seismic is being used to
monitor underground storage of CO 2 . Presently, there
is a global initiative to decrease the atmospheric CO 2
content, and one way to achieve this goal is to pump
huge amounts of CO 2 into saline aquifers. A third
application of 4D seismic (with other geophysical
methods) is the monitoring of geohazards (landslides,
volcanoes etc.), however this will not be covered here.
The business advantage of using 4D seismic on a
given field is closely correlated with the complexity of
the field. Figure 19.1 shows a 3D perspective view of
the top reservoir (top Brent) interface for the Gullfaks
Field. Since the oil is trapped below such a complex 3D
surface, it is not surprising that oil pockets can remain
untouched even after 10–15 years of production. Since
4D seismic can be used to identify such pockets, it is
easy to understand the commercial value of such a tool.
However, if the reservoir geometry is simpler, the number of untapped hydrocarbon pockets will be less and
the business benefit correspondingly lower.
The first 4D seismic surveys were probably acquired
in America in the early 1980s. It was soon realised that
heavy oil fields were excellent candidates for 4D seismic. Heavy oil is highly viscous, so thermal methods
such as combustion or steam injection were used to
increase its mobility. Combustion describes a burning
process, which normally is maintained by injection of
oxygen or air. As the reservoir is heated, the seismic Pwave velocity decreases, and this results in amplitude
changes between baseline and monitor seismic surveys.
The best known example is maybe the one
published by Greaves and Fulp in 1987, for which
they received the award for the best paper in Geophysics. They showed that such thermal recovery methods
could be monitored by repeating conventional 3D land
seismic surveys (Fig. 19.2). These early examples of
seismic monitoring of thermal recovery methods did
not immediately lead to a boom in the 4D industry,
mainly because they were performed on small and
very shallow onshore fields. The major breakthrough
for commercial 4D seismic surveys in the North Sea
was the Gullfaks 4D study launched by Statoil in 1995.
Together with WesternGeco a pilot study was done
M. Landrø (*)
NTNU Trondheim, Trondheim, Norway
e-mail: martin.landro@ntnu.no
K. Bjørlykke (ed.), Petroleum Geoscience: From Sedimentary Environments to Rock Physics,
DOI 10.1007/978-3-642-34132-8_19, # Springer-Verlag Berlin Heidelberg 2015
489
4D Seismic
Martin Landrø
19.1 Introduction
The term 4D seismic reflects that calendar time
represents the fourth dimension. A more precise term is
repeated seismic, because that is actually what is done: a
seismic survey over a given area (oil/gas field) is repeated
in order to monitor production changes. Time-lapse seismic is another term used for this. For some reason, the
term 4D seismic is most common, and we will therefore
use it here. It is important to note that if we repeat 2D
surveys, it is still denoted 4D seismic according to this
definition. Recent examples of such surveys are repeated
2D lines acquired over the Troll gas province.
Currently there are three major areas where 4D
seismic is applied. Firstly, to monitor changes in a
producing hydrocarbon reservoir. This is now an
established procedure being used worldwide. So far,
4D seismic has almost exclusively been used for clastic
reservoirs and only rarely for carbonate reservoirs. This
is because carbonate reservoirs (apart from those in
porous chalk) are stiffer, and the effect on the seismic
parameters of substituting oil with water is far less
pronounced. Secondly, 4D seismic is being used to
monitor underground storage of CO 2 . Presently, there
is a global initiative to decrease the atmospheric CO 2
content, and one way to achieve this goal is to pump
huge amounts of CO 2 into saline aquifers. A third
application of 4D seismic (with other geophysical
methods) is the monitoring of geohazards (landslides,
volcanoes etc.), however this will not be covered here.
The business advantage of using 4D seismic on a
given field is closely correlated with the complexity of
the field. Figure 19.1 shows a 3D perspective view of
the top reservoir (top Brent) interface for the Gullfaks
Field. Since the oil is trapped below such a complex 3D
surface, it is not surprising that oil pockets can remain
untouched even after 10–15 years of production. Since
4D seismic can be used to identify such pockets, it is
easy to understand the commercial value of such a tool.
However, if the reservoir geometry is simpler, the number of untapped hydrocarbon pockets will be less and
the business benefit correspondingly lower.
The first 4D seismic surveys were probably acquired
in America in the early 1980s. It was soon realised that
heavy oil fields were excellent candidates for 4D seismic. Heavy oil is highly viscous, so thermal methods
such as combustion or steam injection were used to
increase its mobility. Combustion describes a burning
process, which normally is maintained by injection of
oxygen or air. As the reservoir is heated, the seismic Pwave velocity decreases, and this results in amplitude
changes between baseline and monitor seismic surveys.
The best known example is maybe the one
published by Greaves and Fulp in 1987, for which
they received the award for the best paper in Geophysics. They showed that such thermal recovery methods
could be monitored by repeating conventional 3D land
seismic surveys (Fig. 19.2). These early examples of
seismic monitoring of thermal recovery methods did
not immediately lead to a boom in the 4D industry,
mainly because they were performed on small and
very shallow onshore fields. The major breakthrough
for commercial 4D seismic surveys in the North Sea
was the Gullfaks 4D study launched by Statoil in 1995.
Together with WesternGeco a pilot study was done
M. Landrø (*)
NTNU Trondheim, Trondheim, Norway
e-mail: martin.landro@ntnu.no
K. Bjørlykke (ed.), Petroleum Geoscience: From Sedimentary Environments to Rock Physics,
DOI 10.1007/978-3-642-34132-8_19, # Springer-Verlag Berlin Heidelberg 2015
489