(hi)(hi)(hi)(hi)
:gift::gift:
Petroleum Geology
(Developments in Petroleum Science)
By
R. E. Chapman
Publisher
Elsevier Science Ltd
Number Of Pages: 434
Publication Date: 1983-12
ISBN-10 / ASIN: 0444421653
ISBN-13 / EAN: 9780444421654
PREFACE
The fascination of petroleum geology lies both in its complexity and in its
importance to society. There is still much that we do not understand; and
there is much to learn if remaining undiscovered reserves of oil and gas are to
be found economically. It is also good geology with a healthy practical component.
The great advances in geological thought and understanding in the 19th
Century were based largely on the construction of coal mines, railways and
canals. But this was almost two-dimensional geology of the land, bounded by
the low-tide line. In the last 30 years or so, geology has moved offshore onto
the continental shelves and ocean floors, largely under the stimulus of petroleum
exploration, and with it has grown a great wealth of geological information.
In “Petroleum Geology: a Concise Study” (published by Elsevier in 1973,
with the paperback edition in 1976) I attempted to focus on those elements
of petroleum geology that seemed to be amenable to synthesis and to
provide a broader understanding of some significant processes in petroleum
geology. Since then, there has been an even more spectacular growth in the
quality and quantity of geological information. We are still being buried
under a mountain of empirical data.
I remarked then, as many others had before me, that petroleum geology
embraces more disciplines of science than one mortal can master. The same
is true today, of course, and it is also true that in many of our fundamental
topics, no true consensus has emerged. This is not through lack of information
(although this is certainly retarding our progress in the microbiological
aspects of petroleum geology). The notable exception is the consensus
reached on the geochemical aspects of the origin and generation of petroleum.
Since writing my first book, books have been written on petroleum geochemistry,
abnormal pore-fluid pressures, and empirical approaches to petroleum
migration (among others), whereas only papers in journals or chapters
of books had appeared before. These were all valuable contributions to
petroleum geology; but there has grown from these and other works a need
for another treatment of petroleum geology that will help the individual to
get a grasp of the whole subject and the interactions between the specialist
topics. This is particularly important for the student because, once an active
career in industry begins, little time will be found to keep up with the literature.
This book is the child of the first. It was no longer possible, or even desirable,
to follow the format of the first book, although I have no reason to wish
to change the main conclusions in it. Once again, I have tried to present the
subject in a way that will also interest the student who does not intend to
follow a career in the petroleum industry. I hope also that, like its predecessor,
this book will also interest those with some experience in the industry.
My purpose here is to present a view of petroleum geology that may also
contribute something to our understanding of wider aspects of geology. I
have only paraphrased the works of others in essential outline. References to
topics not considered here in detail are given at the end of each chapter, as
are references to works that present a different view or interpretation. The
reader is encouraged to delve into the literature because it is exciting.
The most worrying aspect of the developments of the last two or three
decades concerns the eternal problem of scientific rigour in what is essentially
an applied science. It is quite certain that many of us are in error in
our ideas and assertions: what is not certain is who they are, and which
ideas and assertions are in error. It is not the purpose of science to avoid
error, but to avoid its propagation. In our branch of science, which depends
almost exclusively on industrial operations for data, much of which is confidential
to the company acquiring the data, there is little control in the scientific
sense. This is not to impute dishonesty to anyone. The pressures within
the petroleum industry simply do not allow much time for thought, and it is
not necessary to prove a theory or hypothesis before it is put to practical
use. But this can lead us into errors that may have important practical consequences.
For example, vitrinite reflectance was found some years ago to have
real practical value in assessing the prospects of exploratory wells in some
areas (not all). There was danger of forgetting the logic of the association,
and some came to believe that there was a causal association. There are many
areas of the world where, if such a dogmatic approach had been taken, important
reserves would not have been discovered. The danger here is that
that information can be obtained from a single well. Fortunately, other techniques
for assessing maturity of sedimentary rocks were developed, and
vitrinite reflectance is but one of the methods used. If scientific proof had
been required before its use, this technique would never have developed to
usefulness. But there is still a danger that we have misunderstood the nature
of maturity.
This raises the question of parochialism. Some years ago I suggested to the
author of a paper on abnormally high pore pressures in mudstones that his
reliance on clay-mineral diagenesis could lead him into difficulties if confronted
with abnormal pressures at depths known to be shallower than the
depths of this diagenesis. His reply was that his company had “proof” that
the cause of abnormal pressures is clay-mineral diagenesis. A few months
later, in the research laboratory of another company, I was shown “proof”
that clay -mineral diagenesis is not the cause of abnormal pressures.
The point is this: if your perspective is limited to one part of the world,
you are more likely to be led into erroneous ideas because the evidence that
would distinguish cause and coincidence might be lacking. A geologist who
has spent his career in the Western Canada basin would probably have totally
different ideas about the generation, migration and entrapment of petroleum
from one whose career had been spent in the U S . Gulf Coast. Indeed, they
would probably have different ideas about the nature of geology in general.
Not the least of these contrasts would be the lack of deformation in the Western
Canada basin where, from the well-head, the Rocky Mountains can be seen;
while the Gulf Coast is deformed under the continental shelf with no land
in sight, let alone mountains. But our Canadian geologist would feel quite at
home in Mexico and Libya, while our Gulf Coast geologist would feel quite
at home in Nigeria and South-East Asia.
Geology, I believe, still suffers from one important, but unavoidable, fact:
it grew from studies of outcrop, which are necessarily confined to the land
areas, with the third dimension limited to the depths of mines and
the heights of mountains, and it is still practised by a majority of geologists
within these dimensions. The geology of what we can see and touch is the
geology of sedimentary basins that are no longer accumulating sediment, and
the geology of orogeny. Petroleum geology gives us a glimpse of sedimentary
basins that are still actively accumulating sediment, and are still being deformed
in spite of the fact that they have not yet suffered orogeny. Petroleum
geology, although not giving us a complete three-dimensional picture,
has given us a three-dimensional picture of some areas in great detail to
depths of two, three, and four kilometres. Who would have imagined that
there could be Mesozoic thrust faults beneath the horizontal Tertiary of the
north German plains? . . . or folds and faults in young Tertiary sediments in
many continental shelves? Our conception of an unconformity seems to
have been dominated by Hutton’s unconformity on the east coast of Scotland,
and an assumption of subaerial erosion; yet there are extensive and important
unconformities in the continental shelves that were never subaerially
formed, so far as we can determine, and the deformation, erosion and subsequent
sediment accumulation were entirely submarine.
These matters affect our understanding of geology. There are others that
affect our understanding of petroleum geology. When people peer into our
science from another discipline, and speak with confidence, we tend to accept
what they say. Lord Kelvin poured scorn on geologists of the last century,
and few rose to defend geology against him. A century later, we can
say with confidence that most of what he said about geology and geologists
was wrong. During the last 20 years or so, chemists have spoken with increasing
confidence about the generation of oil, and geologists have tended to
mould their concepts to fit the hypotheses of chemists. Some seem to have
forgotten that geology is also a science - even if an imprecise one compared
to chemistry, physics and mathematics, but nevertheless a science with its
own logic. No geochemical hypothesis can be satisfactory unless it is also
satisfactory from a geological point of view. This is not to assert that the
geochemists are wrong, but rather to assert that the search for the truth
about oil generation and migration must be a search for hypotheses that are
geologically as well as chemically satisfying. It is not at all clear that this
happy state has been reached in any major petroleum province.
Finally, it must be remembered that whether an hypothesis is correct or
erroneous cannot be determined by voting. The majority is not always right.
A vote taken in 1950 on the validity of continental drift would have had a
very different result from one taken in 1980. My friend S.W. Carey, who
would probably have been in the minority on both votes, may yet turn out
to be more correct than the rest of us!
It is therefore my earnest hope that readers will read this book not with
their eyes but with their minds, to try and get at the fundamentals of the
various problems and, above all, to develop an independent assessment of
the nature of petroleum geology. The answers to our problems lie in the
geology of our petroleum provinces and the geology of provinces without
petroleum, not in books.
Brisbane, 3 October 1982 RICHARD E. CHAPMAN
LinK
http://rapidshare.com/files/210128294/0444421653_Petroleum_Geology.rar
:gift::gift:
Petroleum Geology
(Developments in Petroleum Science)
By
R. E. Chapman
Publisher
Elsevier Science Ltd
Number Of Pages: 434
Publication Date: 1983-12
ISBN-10 / ASIN: 0444421653
ISBN-13 / EAN: 9780444421654
PREFACE
The fascination of petroleum geology lies both in its complexity and in its
importance to society. There is still much that we do not understand; and
there is much to learn if remaining undiscovered reserves of oil and gas are to
be found economically. It is also good geology with a healthy practical component.
The great advances in geological thought and understanding in the 19th
Century were based largely on the construction of coal mines, railways and
canals. But this was almost two-dimensional geology of the land, bounded by
the low-tide line. In the last 30 years or so, geology has moved offshore onto
the continental shelves and ocean floors, largely under the stimulus of petroleum
exploration, and with it has grown a great wealth of geological information.
In “Petroleum Geology: a Concise Study” (published by Elsevier in 1973,
with the paperback edition in 1976) I attempted to focus on those elements
of petroleum geology that seemed to be amenable to synthesis and to
provide a broader understanding of some significant processes in petroleum
geology. Since then, there has been an even more spectacular growth in the
quality and quantity of geological information. We are still being buried
under a mountain of empirical data.
I remarked then, as many others had before me, that petroleum geology
embraces more disciplines of science than one mortal can master. The same
is true today, of course, and it is also true that in many of our fundamental
topics, no true consensus has emerged. This is not through lack of information
(although this is certainly retarding our progress in the microbiological
aspects of petroleum geology). The notable exception is the consensus
reached on the geochemical aspects of the origin and generation of petroleum.
Since writing my first book, books have been written on petroleum geochemistry,
abnormal pore-fluid pressures, and empirical approaches to petroleum
migration (among others), whereas only papers in journals or chapters
of books had appeared before. These were all valuable contributions to
petroleum geology; but there has grown from these and other works a need
for another treatment of petroleum geology that will help the individual to
get a grasp of the whole subject and the interactions between the specialist
topics. This is particularly important for the student because, once an active
career in industry begins, little time will be found to keep up with the literature.
This book is the child of the first. It was no longer possible, or even desirable,
to follow the format of the first book, although I have no reason to wish
to change the main conclusions in it. Once again, I have tried to present the
subject in a way that will also interest the student who does not intend to
follow a career in the petroleum industry. I hope also that, like its predecessor,
this book will also interest those with some experience in the industry.
My purpose here is to present a view of petroleum geology that may also
contribute something to our understanding of wider aspects of geology. I
have only paraphrased the works of others in essential outline. References to
topics not considered here in detail are given at the end of each chapter, as
are references to works that present a different view or interpretation. The
reader is encouraged to delve into the literature because it is exciting.
The most worrying aspect of the developments of the last two or three
decades concerns the eternal problem of scientific rigour in what is essentially
an applied science. It is quite certain that many of us are in error in
our ideas and assertions: what is not certain is who they are, and which
ideas and assertions are in error. It is not the purpose of science to avoid
error, but to avoid its propagation. In our branch of science, which depends
almost exclusively on industrial operations for data, much of which is confidential
to the company acquiring the data, there is little control in the scientific
sense. This is not to impute dishonesty to anyone. The pressures within
the petroleum industry simply do not allow much time for thought, and it is
not necessary to prove a theory or hypothesis before it is put to practical
use. But this can lead us into errors that may have important practical consequences.
For example, vitrinite reflectance was found some years ago to have
real practical value in assessing the prospects of exploratory wells in some
areas (not all). There was danger of forgetting the logic of the association,
and some came to believe that there was a causal association. There are many
areas of the world where, if such a dogmatic approach had been taken, important
reserves would not have been discovered. The danger here is that
that information can be obtained from a single well. Fortunately, other techniques
for assessing maturity of sedimentary rocks were developed, and
vitrinite reflectance is but one of the methods used. If scientific proof had
been required before its use, this technique would never have developed to
usefulness. But there is still a danger that we have misunderstood the nature
of maturity.
This raises the question of parochialism. Some years ago I suggested to the
author of a paper on abnormally high pore pressures in mudstones that his
reliance on clay-mineral diagenesis could lead him into difficulties if confronted
with abnormal pressures at depths known to be shallower than the
depths of this diagenesis. His reply was that his company had “proof” that
the cause of abnormal pressures is clay-mineral diagenesis. A few months
later, in the research laboratory of another company, I was shown “proof”
that clay -mineral diagenesis is not the cause of abnormal pressures.
The point is this: if your perspective is limited to one part of the world,
you are more likely to be led into erroneous ideas because the evidence that
would distinguish cause and coincidence might be lacking. A geologist who
has spent his career in the Western Canada basin would probably have totally
different ideas about the generation, migration and entrapment of petroleum
from one whose career had been spent in the U S . Gulf Coast. Indeed, they
would probably have different ideas about the nature of geology in general.
Not the least of these contrasts would be the lack of deformation in the Western
Canada basin where, from the well-head, the Rocky Mountains can be seen;
while the Gulf Coast is deformed under the continental shelf with no land
in sight, let alone mountains. But our Canadian geologist would feel quite at
home in Mexico and Libya, while our Gulf Coast geologist would feel quite
at home in Nigeria and South-East Asia.
Geology, I believe, still suffers from one important, but unavoidable, fact:
it grew from studies of outcrop, which are necessarily confined to the land
areas, with the third dimension limited to the depths of mines and
the heights of mountains, and it is still practised by a majority of geologists
within these dimensions. The geology of what we can see and touch is the
geology of sedimentary basins that are no longer accumulating sediment, and
the geology of orogeny. Petroleum geology gives us a glimpse of sedimentary
basins that are still actively accumulating sediment, and are still being deformed
in spite of the fact that they have not yet suffered orogeny. Petroleum
geology, although not giving us a complete three-dimensional picture,
has given us a three-dimensional picture of some areas in great detail to
depths of two, three, and four kilometres. Who would have imagined that
there could be Mesozoic thrust faults beneath the horizontal Tertiary of the
north German plains? . . . or folds and faults in young Tertiary sediments in
many continental shelves? Our conception of an unconformity seems to
have been dominated by Hutton’s unconformity on the east coast of Scotland,
and an assumption of subaerial erosion; yet there are extensive and important
unconformities in the continental shelves that were never subaerially
formed, so far as we can determine, and the deformation, erosion and subsequent
sediment accumulation were entirely submarine.
These matters affect our understanding of geology. There are others that
affect our understanding of petroleum geology. When people peer into our
science from another discipline, and speak with confidence, we tend to accept
what they say. Lord Kelvin poured scorn on geologists of the last century,
and few rose to defend geology against him. A century later, we can
say with confidence that most of what he said about geology and geologists
was wrong. During the last 20 years or so, chemists have spoken with increasing
confidence about the generation of oil, and geologists have tended to
mould their concepts to fit the hypotheses of chemists. Some seem to have
forgotten that geology is also a science - even if an imprecise one compared
to chemistry, physics and mathematics, but nevertheless a science with its
own logic. No geochemical hypothesis can be satisfactory unless it is also
satisfactory from a geological point of view. This is not to assert that the
geochemists are wrong, but rather to assert that the search for the truth
about oil generation and migration must be a search for hypotheses that are
geologically as well as chemically satisfying. It is not at all clear that this
happy state has been reached in any major petroleum province.
Finally, it must be remembered that whether an hypothesis is correct or
erroneous cannot be determined by voting. The majority is not always right.
A vote taken in 1950 on the validity of continental drift would have had a
very different result from one taken in 1980. My friend S.W. Carey, who
would probably have been in the minority on both votes, may yet turn out
to be more correct than the rest of us!
It is therefore my earnest hope that readers will read this book not with
their eyes but with their minds, to try and get at the fundamentals of the
various problems and, above all, to develop an independent assessment of
the nature of petroleum geology. The answers to our problems lie in the
geology of our petroleum provinces and the geology of provinces without
petroleum, not in books.
Brisbane, 3 October 1982 RICHARD E. CHAPMAN
LinK
http://rapidshare.com/files/210128294/0444421653_Petroleum_Geology.rar
