Titusville in West Pennsylvania that oil was recovered
in any quantity from boreholes. He drilled a well about
25 m (70 ft) deep which produced 8–10 bbl/day, a
huge production rate compared with anything earlier.
A few years later there were 74 wells round Oil Creek,
and the USA’s annual production had risen to half a
million barrels. Outside the USA the calculated total
production at that time was maximum 5,000 bbl. In
1870 production had increased tenfold, with 5 million
bbl from the USA, and 538,000 bbl from other
countries. In southern California oil production started
early in 1864 (in Santa Paula), but for many years oil
was mined by driving shafts into the oil-bearing strata
because it was so heavy and biodegraded that it would
not flow in a well.
In its infancy, oil exploration consisted largely of
looking for oil seepage at the surface and drilling in
the vicinity, which did not require much geological
knowledge. It was then realised that oil and gas occur
where layers of sedimentary rocks form domes or
anticlinal structures since petroleum is less dense
than water and a low permeability (seal) layer is
needed to prevent the oil and gas from rising and
escaping. This led to extensive geological mapping
of anticlines and domes visible at the surface, particularly in the USA. It was also found that oil fields had a
tendency to lie along structural trends defined by
anticlines or faults and this “rule” was used in
prospecting. This is also often the case with salt
domes, which became important prospecting targets.
Oil production developed rapidly up to the end of
the nineteenth century, and more systematic geological principles for prospecting were gradually developed. The geological information which one obtains at
the surface is often not representative of the structures
deeper down. Structures which are not visible at the
surface could be mapped by correlation between wells
using logs and cuttings from the drilling. One method
was to measure the depth of particularly characteristic
strata through analysis of cuttings in different wells.
Improved electrical measurements (logs) from wells,
developed during the 1920s and 1930s, made the
whole effort much simpler because they provided
continuous vertical sections through the rocks. The
first logs were simple recordings of how well rocks
conduct electrical currents (resistivity), and later also
gamma logs recorded the gamma-radiation emitted by
the different sedimentary rocks.
The USA maintained its position as the major
world producer of oil and gas well into the twentieth
century. Americans thus became leaders in the development of oil technology, which today is strongly
reflected in the industry’s terminology. The US used
to be a major importer of oil despite domestic production, though this has recently increased due to shale oil
and gas. The need for import has therefore been
reduced. For energy statistics: www.eia.gov.
The US consumption (18-20 million barrels/day) is
a very large fraction of the total world consumption
(94 million bbl/day).
It was first in the 1930–1940 period that the industry became aware of the vast oil resources of the
Middle East, which now account for about 60% of
world reserves. Since then this region has dominated
oil production.
In the 1950s and 1960s prospecting for oil and gas
was extended onto the continental shelves, opening up
new reserves. Until the development of modern seismic it was not possible to effectively explore deep
below the seafloor in sedimentary basins offshore. As
long as there was an abundance of oil to be found in
onshore basins there was little incentive to develop
costly drilling rigs for offshore exploration and
platforms for production.
Since the 1970s an increasingly large share of
international prospecting has taken place offshore,
helped by improved seismic methods. Advanced well
log technology in particular made it possible to gain
optimal information from each well. Before the development of powerful computers, seismic recordings
were based on analogue methods which produced
results very far removed from the standard of modern
seismic data. Recording of seismic data from ships is
much less expensive than onshore where geophones
have to be laid out manually. Onshore, extensive drilling may be cheaper than expensive seismic mapping.
Rising oil prices and new technology have made
exploration financially attractive in areas which previously were of little interest, including in very deep
waters. High oil prices can also pay for more enhanced
hydrocarbon recovery from reservoirs. There are now
relatively few sedimentary basins in the world that
have not been explored and it is getting increasingly
difficult to find new giant fields (>500 million bbl).
There is now increasing interest in heavy oil, tar
sand and oil shale.
1 Introduction to Petroleum Geology
3
in any quantity from boreholes. He drilled a well about
25 m (70 ft) deep which produced 8–10 bbl/day, a
huge production rate compared with anything earlier.
A few years later there were 74 wells round Oil Creek,
and the USA’s annual production had risen to half a
million barrels. Outside the USA the calculated total
production at that time was maximum 5,000 bbl. In
1870 production had increased tenfold, with 5 million
bbl from the USA, and 538,000 bbl from other
countries. In southern California oil production started
early in 1864 (in Santa Paula), but for many years oil
was mined by driving shafts into the oil-bearing strata
because it was so heavy and biodegraded that it would
not flow in a well.
In its infancy, oil exploration consisted largely of
looking for oil seepage at the surface and drilling in
the vicinity, which did not require much geological
knowledge. It was then realised that oil and gas occur
where layers of sedimentary rocks form domes or
anticlinal structures since petroleum is less dense
than water and a low permeability (seal) layer is
needed to prevent the oil and gas from rising and
escaping. This led to extensive geological mapping
of anticlines and domes visible at the surface, particularly in the USA. It was also found that oil fields had a
tendency to lie along structural trends defined by
anticlines or faults and this “rule” was used in
prospecting. This is also often the case with salt
domes, which became important prospecting targets.
Oil production developed rapidly up to the end of
the nineteenth century, and more systematic geological principles for prospecting were gradually developed. The geological information which one obtains at
the surface is often not representative of the structures
deeper down. Structures which are not visible at the
surface could be mapped by correlation between wells
using logs and cuttings from the drilling. One method
was to measure the depth of particularly characteristic
strata through analysis of cuttings in different wells.
Improved electrical measurements (logs) from wells,
developed during the 1920s and 1930s, made the
whole effort much simpler because they provided
continuous vertical sections through the rocks. The
first logs were simple recordings of how well rocks
conduct electrical currents (resistivity), and later also
gamma logs recorded the gamma-radiation emitted by
the different sedimentary rocks.
The USA maintained its position as the major
world producer of oil and gas well into the twentieth
century. Americans thus became leaders in the development of oil technology, which today is strongly
reflected in the industry’s terminology. The US used
to be a major importer of oil despite domestic production, though this has recently increased due to shale oil
and gas. The need for import has therefore been
reduced. For energy statistics: www.eia.gov.
The US consumption (18-20 million barrels/day) is
a very large fraction of the total world consumption
(94 million bbl/day).
It was first in the 1930–1940 period that the industry became aware of the vast oil resources of the
Middle East, which now account for about 60% of
world reserves. Since then this region has dominated
oil production.
In the 1950s and 1960s prospecting for oil and gas
was extended onto the continental shelves, opening up
new reserves. Until the development of modern seismic it was not possible to effectively explore deep
below the seafloor in sedimentary basins offshore. As
long as there was an abundance of oil to be found in
onshore basins there was little incentive to develop
costly drilling rigs for offshore exploration and
platforms for production.
Since the 1970s an increasingly large share of
international prospecting has taken place offshore,
helped by improved seismic methods. Advanced well
log technology in particular made it possible to gain
optimal information from each well. Before the development of powerful computers, seismic recordings
were based on analogue methods which produced
results very far removed from the standard of modern
seismic data. Recording of seismic data from ships is
much less expensive than onshore where geophones
have to be laid out manually. Onshore, extensive drilling may be cheaper than expensive seismic mapping.
Rising oil prices and new technology have made
exploration financially attractive in areas which previously were of little interest, including in very deep
waters. High oil prices can also pay for more enhanced
hydrocarbon recovery from reservoirs. There are now
relatively few sedimentary basins in the world that
have not been explored and it is getting increasingly
difficult to find new giant fields (>500 million bbl).
There is now increasing interest in heavy oil, tar
sand and oil shale.
1 Introduction to Petroleum Geology
3