Organic geochemistry, which includes the study of
organic matter in sediments and its transformation into
hydrocarbons, has become another vital part of petroleum geology.
Tectonics and structural geology provide an understanding of the subsidence, folding and uplift responsible for the creation and dynamic history of a basin.
The timing of the folding and faulting that forms
structural traps is very important in relation to the
migration of hydrocarbons.
Seismic methods have become the main tool for
mapping sedimentary facies, stratigraphy, sequence
stratigraphy and tectonic development. Marine
seismics recorded from ships have become very efficient and seismic lines are shot at only a few 100 m
spacing or less. Because of the rapid improvement in
the quality of seismic data processing techniques, geological interpretation of seismic data has become an
important and expanding field. Seismic and other geophysical data are often the only information we have,
particularly for offshore exploration where drilling is
very costly. Shooting seismic lines with a close
spacing allows high resolution 3D seismic imagery
to be produced for critical parts of sedimentary basins.
By repeating a 3D reservoir seismic survey during
production, one can observe how the gas/oil and oil/
water contacts move as the reservoir is depleted. This
is called 4D seismic because time provides the fourth
dimension.
Geophysical measurements may include gravimetry and magnetometry; electromagnetic methods that
were used mostly in ore exploration have also in the
last 10–20 years been applied to oil exploration. Electromagnetic methods have been used to detect
sediments with low resistivity due to the presence of
oil instead of saline water. This method requires a few
100 m of water depth and relatively shallow accumulation (<2–3 km).
Seismic surveys are more expensive on land than by
ship at sea because geophones have to be placed in a
grid, often on uneven and difficult land surfaces. Drilling on land, however, costs much less than from
offshore rigs and a much denser well spacing can be
used during both exploration and production.
Indirect methods of mapping rock types employing
geophysical aids are becoming increasingly important
in petroleum geology, but it is still necessary to take
samples and examine the rocks themselves. A
petroleum geologist should have a broad geological
training, preferably also from field work.
Geophysical well-logging methods have developed
equally rapidly, from simple electric and radioactive
logs to highly advanced logging tools which provide
detailed information about the sequence penetrated by
the well. Logs provide a continuity of information
about the rock properties which one can seldom obtain
from exposures or core samples. This information
makes it possible to interpret not only the lithological
composition of the rocks and the variation of porosity
and permeability, but also the depositional environment. Image logs make it possible also to detect bedding and fractures inside the wells.
Practical petroleum geology is not only based on
many different geological and geophysical disciplines.
A good background in basic chemistry, physics, mathematics and computing is also required, particularly
for different types of basin modelling.
A very large percentage of the geologists and
geophysicists in the world are directly or indirectly
involved with the petroleum industry which recruits a
large percentage of the university students in relevant
fields.
The petroleum industry also funds much research
which is not narrow applied research, but more general
contributions to the understanding of the Earth’s crust
and particularly sedimentary basins. Applied research
directed towards exploration and production of oil and
gas has often resulted in insight into more fundamental
geological processes.
Environmental geology has become a very important field to deal with problems not only related to the
petroleum industry but generally about the distribution
of pollutants in rocks and sediments.
A good background in chemistry is then required.
1.1
A Brief Petroleum History
There are many places where oil seeps out of the
ground. Bitumen produced from such naturally occurring crude oil has been collected and used since
ancient times, both for lighting and medicine, and by
the Greeks even for warfare. In some places, for
example Germany in the 1800s, small mines were
dug to get at the oil. Before 1859 oil was also recovered from coal for use in kerosene lamps. It was not
until Edwin Drake’s exploits in 1859 at Oil Creek near
2
K. Bjørlykke
organic matter in sediments and its transformation into
hydrocarbons, has become another vital part of petroleum geology.
Tectonics and structural geology provide an understanding of the subsidence, folding and uplift responsible for the creation and dynamic history of a basin.
The timing of the folding and faulting that forms
structural traps is very important in relation to the
migration of hydrocarbons.
Seismic methods have become the main tool for
mapping sedimentary facies, stratigraphy, sequence
stratigraphy and tectonic development. Marine
seismics recorded from ships have become very efficient and seismic lines are shot at only a few 100 m
spacing or less. Because of the rapid improvement in
the quality of seismic data processing techniques, geological interpretation of seismic data has become an
important and expanding field. Seismic and other geophysical data are often the only information we have,
particularly for offshore exploration where drilling is
very costly. Shooting seismic lines with a close
spacing allows high resolution 3D seismic imagery
to be produced for critical parts of sedimentary basins.
By repeating a 3D reservoir seismic survey during
production, one can observe how the gas/oil and oil/
water contacts move as the reservoir is depleted. This
is called 4D seismic because time provides the fourth
dimension.
Geophysical measurements may include gravimetry and magnetometry; electromagnetic methods that
were used mostly in ore exploration have also in the
last 10–20 years been applied to oil exploration. Electromagnetic methods have been used to detect
sediments with low resistivity due to the presence of
oil instead of saline water. This method requires a few
100 m of water depth and relatively shallow accumulation (<2–3 km).
Seismic surveys are more expensive on land than by
ship at sea because geophones have to be placed in a
grid, often on uneven and difficult land surfaces. Drilling on land, however, costs much less than from
offshore rigs and a much denser well spacing can be
used during both exploration and production.
Indirect methods of mapping rock types employing
geophysical aids are becoming increasingly important
in petroleum geology, but it is still necessary to take
samples and examine the rocks themselves. A
petroleum geologist should have a broad geological
training, preferably also from field work.
Geophysical well-logging methods have developed
equally rapidly, from simple electric and radioactive
logs to highly advanced logging tools which provide
detailed information about the sequence penetrated by
the well. Logs provide a continuity of information
about the rock properties which one can seldom obtain
from exposures or core samples. This information
makes it possible to interpret not only the lithological
composition of the rocks and the variation of porosity
and permeability, but also the depositional environment. Image logs make it possible also to detect bedding and fractures inside the wells.
Practical petroleum geology is not only based on
many different geological and geophysical disciplines.
A good background in basic chemistry, physics, mathematics and computing is also required, particularly
for different types of basin modelling.
A very large percentage of the geologists and
geophysicists in the world are directly or indirectly
involved with the petroleum industry which recruits a
large percentage of the university students in relevant
fields.
The petroleum industry also funds much research
which is not narrow applied research, but more general
contributions to the understanding of the Earth’s crust
and particularly sedimentary basins. Applied research
directed towards exploration and production of oil and
gas has often resulted in insight into more fundamental
geological processes.
Environmental geology has become a very important field to deal with problems not only related to the
petroleum industry but generally about the distribution
of pollutants in rocks and sediments.
A good background in chemistry is then required.
1.1
A Brief Petroleum History
There are many places where oil seeps out of the
ground. Bitumen produced from such naturally occurring crude oil has been collected and used since
ancient times, both for lighting and medicine, and by
the Greeks even for warfare. In some places, for
example Germany in the 1800s, small mines were
dug to get at the oil. Before 1859 oil was also recovered from coal for use in kerosene lamps. It was not
until Edwin Drake’s exploits in 1859 at Oil Creek near
2
K. Bjørlykke