An Introduction to Petroleum Geoscience

319 Pages·2017·40.53 MB·English

by  Michael Ala

The Imperial College Lectures in
PETROLEUM ENGINEERING
An Introduction to
Petroleum Geoscience
Volume
1
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The Imperial College Lectures in
PETROLEUM ENGINEERING
An Introduction to
Petroleum Geoscience
Volume
1
Michael Ala
Imperial College London, UK
World Scientific
NEW JERSEY • LONDON • SINGAPORE • BEIJING • SHANGHAI • HONG KONG • TAIPEI • CHENNAI • TOKYO
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Published by
World Scientific Publishing Europe Ltd.
57 Shelton Street, Covent Garden, London WC2H 9HE
Head office: 5 Toh Tuck Link, Singapore 596224
USA office: 27 Warren Street, Suite 401-402, Hackensack, NJ 07601
Library of Congress Cataloging-in-Publication Data
Names: Ala, Michael, author.
Title: An introduction to petroleum geoscience / by Michael Ala, (Imperial College London, UK).
Description: [Hackensack] New Jersey : World Scientific, [2017] |
Series: The Imperial College lectures in petroleum engineering ; volume 1 | Includes index.
Identifiers: LCCN 2016049017 | ISBN 9781786342065 (hc : alk. paper)
Subjects: LCSH: Petroleum--Geology. | Petroleum reserves.
Classification: LCC TN870.5 . A528 2017 | DDC 553.2/8--dc23
LC record available at https://lccn.loc.gov/2016049017
British Library Cataloguing-in-Publication Data
A catalogue record for this book is available from the British Library.
Copyright © 2017 by World Scientific Publishing Europe Ltd.
All rights reserved. This book, or parts thereof, may not be reproduced in any form or by any means,
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Preface
Petroleum geoscience is a multidisciplinary subject, underpinned by
the broad spectrum of the Earth sciences. The aim of this book
is to cover the fundamentals of the Earth sciences and examine
their role in controlling the global occurrence and distribution of oil
and gas resources. It also explains the principles, practices and the
terminology associated with the upstream sector (exploration and
production activities) of the oil industry. The book is intended also
for non-geoscientists — petroleum engineers, drilling engineers and
petrophysicists — who, due to their interaction with geologists
and geophysicists, benefit from some knowledge of the latters’ role
and work practices in exploration ventures.
With the non-geoscientists in mind, the book opens with a
chapter introducing the principles of geology, defined as the study of
rocks and Earth history. The shape, structure, age and composition
of the Earth are reviewed, followed by a brief discussion of the origin
and description of the rocks comprising the crust, which contains
the world’s commercially accessible mineral and fossil fuel resources.
Since hydrocarbons are hosted primarily in sedimentary rocks,
emphasis is placed on their formation, evolution and descriptions
of the most common types. Movements within the crust cause the
rocks to deform. Thesedeformational features are reviewed briefly in
the closing sections of Chapter 1.
Worldwide, petroleum accumulations are found in sedimentary
basins — depressions in the Earth’s crust containing a large
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vi An Introduction to Petroleum Geoscience
thickness ofsedimentary rocks—andtheparametersthatdetermine
hydrocarbon occurrence are geologically controlled. Plate tecton-
ics plays a paramount role in explaining a wide variety of the
Earth’s geological and geophysical features, including the origin and
subsequent evolution of sedimentary basins. An overview of the
conceptanditsinfluenceonbasinformation,depositionalhistoryand
characteristics is presented in Chapter 2. Petroleum is a chemically
complex substance and encompasses both crude oil and gas. The
chemical composition of petroleum and the impact on its physical
properties of the relative proportions of its constituent components
are discussed in Chapter 3.
Oil and gas fields are economically viable concentrations of
hydrocarbons, the formation of which depends on a number of
factors referred to as elements and processes. The study of how
these elements and processes interact to create hydrocarbon-bearing
provinces is known as Petroleum system analysis. Such analysis
underpins the assessment of the hydrocarbon potential of the area
under exploration and a major part of this book, Chapter 4, is
devoted to the discussion of the generation, migration and accumu-
lation of petroleum.
Exploring for oil and gas requires a systematic approach. Explo-
ration techniques are described in Chapter 5. The first step in the
assessment of the hydrocarbon potential of an area is the collection
of data. Broadly, the information required falls into three categories:
geological, remote sensing (obtained from aerial photography and
satellite imagery) and geophysical (acquired by conducting gravity,
magnetic and seismic surveys). Methods employed in the interpre-
tation of these data are presented and discussed. Preparation of
subsurface maps is an integral part of data interpretation. A large
variety of such maps are in use and serve as indispensable aids in
hydrocarbon reserves estimation. Exploration is inherently risky and
the level of risk associated with drilling objectives identified during
theexplorationphaseneedstobeassessedandquantified.Evaluation
of hydrocarbon potential and assessment of risk at basin or regional
level is referred to as play fairway analysis.
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Preface vii
Chapter 6 addresses the question of resources and reserves.
The former is a broad term, encompassing all industrially useful
materials, which includemineral deposits as well as petroleum,while
the latter refers to the portion of an identified resource that can
be produced economically through existing technology. Following a
classification ofthetermreserves,methodsofestimatingthevolumes
ofhydrocarbonsinitially inplaceinareservoir aredemonstratedand
statistics are provided on the distribution of oil and gas reserves,
production and consumption in global terms. Biofuels are also
discussed.
It has been known for nearly two centuries that vast amounts of
oil and gas are locked up in dark-coloured, organic-rich shale rocks.
These are referred to as unconventional hydrocarbons, defined as oil
and gas deposits that are not stored in pore spaces in permeable
rocks (the reservoir) and are not commercially recoverable by
“conventional” drillingandproductionmethods.Advancesindrilling
andextractiontechnologysincethemid-1990s,however,havemadeit
possibleforsomeofthesehydrocarbonstobeproducedeconomically,
resulting in their status being changed from unconventional to
conventional. Prominent among these are shale oil, shale gas and
oil or tar sands. In particular, oil and gas supplies from shale have
risen rapidly in the US since the turn of the present century and
have transformed the American energy landscape; the US is now
self-sufficient in gas and its imports of crude oil have diminished
significantly. The various types of unconventional hydrocarbons,
their globaldistribution,estimates of thereserves attributedtothem
and production of oil and gas from these sources are reviewed in
Chapter 7.
Oil and gas wells are usually cased. Casing generally protects the
boreholewall,preventsitfromcollapseinunconsolidatedformations,
andshutsofftheflowofunwantedfluidsintotheborehole.Hydrocar-
bons are produced through perforations in the production section of
the casing. Before a well is cased, however, measurements are made
of the electric, acoustic, radioactive, dielectric and nuclear magnetic
properties of the rocks penetrated in the well. This is referred to
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viii An Introduction to Petroleum Geoscience
as well logging and the interpretation of the measurements provides
valuable information on the physical properties of sub-surface rock
layers and their interstitial fluids as well allowing the calculation
of fluid saturations. Knowledge of hydrocarbon saturation is indis-
pensable in the computation of reserves. There are also logging tools
that record the angle of inclination and dip direction of the layers
traversed by the well and devices that provide computer-generated
images of the borehole wall based on the electrical properties or
the acoustic reflectivity of the formations. The acquisition and basic
interpretation of wireline log data are dealt with in Chapter 8.
Finally, there is a glossary that defines the technical terms
and explains the abbreviations used in the Earth and petroleum
geosciences and charts the history and functions of some of the
scientific and data gathering organisations that are associated with
the international oil industry.
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About the Author
Dr. Michael Ala has been closely associated with the oil industry for
more than 35 years as an exploration geologist with an independent
oil company, as a consultant as well as in the field of education and
training. He has a BSc in Oil Technology and an MSc, PhD and DIC
in Petroleum Geology from Imperial College.
In 1973, he joined Seagull Exploration International and was
involved in exploration studies and prospect evaluation in many
parts of the world including Africa, northwest Europe, eastern
Mediterranean, the Caribbean, South America and the Middle East.
In 1976, he became the company’s General Manager in London,
responsible for its north European and Middle Eastern operations.
He joined the academic staff of the Earth Science Department
of Imperial College in 1981, rising to the post of Director of the
internationally recognised MSc Petroleum Geoscience Course in
ix