Page 9 - Petroleum Geology

VIII

This book is the child of the first. It was no longer possible, or even desir-
able, 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 predeces-
sor, 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 essen-
tially 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 confi-
dential to the company acquiring the data, there is little control in the scien-
tific 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 conse-
quences. 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, im-
portant reserves would not have been discovered. The danger here is that
that information can be obtained from a single well. Fortunately, other tech-
niques 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 con-
fronted 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.