ARCTIC OFFSHORE ENGINEERING
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ARCTIC OFFSHORE ENGINEERING Andrew Palmer National University of Singapore, Singapore Ken Croasdale K R Croasdale & Associates Ltd, Canada World Scientific NEW JERSEY LONDON SINGAPORE BEIJING SHANGHAI HONG KONG TAIPEI CHENNAI
Published by World Scientific Publishing Co. Pte. Ltd. 5 Toh Tuck Link, Singapore 596224 USA office: 27 Warren Street, Suite 401-402, Hackensack, NJ 07601 UK office: 57 Shelton Street, Covent Garden, London WC2H 9HE British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library. ARTIC OFFSHORE ENGINEERING Copyright 2013 by World Scientific Publishing Co. Pte. Ltd. All rights reserved. This book, or parts thereof, may not be reproduced in any form or by any means, electronic or mechanical, including photocopying, recording or any information storage and retrieval system now known or to be invented, without written permission from the Publisher. For photocopying of material in this volume, please pay a copying fee through the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, USA. In this case permission to photocopy is not required from the publisher. ISBN 978-981-4368-77-3 Printed in Singapore.
Foreword The Arctic is important to all of us. It offers to humanity enormous resources of oil, gas, gas hydrates, gold, iron ore, diamonds, timber, fish and hydroelectric power. At the same time, it is a fragile human and biological environment. It has indigenous peoples with their own cultures and history, all too easily disrupted by outsiders. It has a wealth of animals and plants, each special in its own way but liable to damage. Andrew Palmer and Ken Croasdale have written this book about Arctic Offshore Engineering, and examine how we can exploit the resources in and under the sea for human purposes, and can do so safely, economically and with minimal risk to the environment. Singapore may at first seem a surprising place to be writing such a book, but in fact we have a significant and growing interest in the Arctic, from several directions, among them shipping and petroleum production. At Keppel we are already active in more than one of those fields, and have a long term commitment to the area. I welcome the book enthusiastically. Choo Chiau Beng CEO, Keppel Corporation Singapore June 2012 v
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Preface AA Milne wrote in the preface to a detective story that the only good reason for writing anything was that you wanted to, and that he would be prouder of a telephone directory written with love than of a tragedy in blank verse, written as a chore. We agree completely. The Arctic is a region of endless fascination, beauty and excitement. Many writers more eloquent than we are have explored its biology, geography, history and environment. At the same time, it is the home of many people who want to pursue civilised and comfortable lives with the amenities of the 21 st century. The Arctic seas and the lands bordering them are important to the wider human community as a source of raw materials, above all petroleum, but as well as for fish, timber and mineral ores, and important too for tourism and exploration. Many important reserves of petroleum have been found already, some of those reserves are in production, and the unexplored geology of this vast region has many promising structures: some estimates have it that as much as a third of the petroleum still to be discovered will be found in the Arctic. With that as one priority, we must not forget that the Arctic is uniquely vulnerable to damage: if we make a mess, the consequences will be with us for decades. Oil and gas reserves close to shore can be produced by horizontal drilling, but beyond a few kilometres the petroleum industry will need platforms to drill from and produce to, and pipelines and other systems to bring the petroleum ashore and transport it to markets. Those structures have to operate safely in an extremely demanding environment. The ocean is cold and rough, and for much of the year it will be covered with ice, often in very large pieces. Ice pushes against structures with great force, and drags along the seabed, strongly enough to cut huge gouges. Sometimes the seabed will be partly frozen, and anything we do may alter the thermal regime and thaw or freeze the seabed soil, greatly modifying its physical properties. Almost all the problems of offshore construction in lower latitudes are still present, and there are storm waves and high winds, tidal currents, shifting seabeds and the added challenge of long periods of winter darkness. Most importantly, anything we are going to build has vii
viii Arctic Offshore Engineering to be constructible, at an acceptable cost, within a reasonable timeframe, safely and without environmental damage. Serious thinking about offshore structures in the Arctic seas began more than forty years ago, initially in Cook Inlet in southern Alaska, then in the Beaufort Sea and the Canadian Arctic Islands, and later in many other areas. One of the critical subjects was the level of ice forces on fixed structures, as opposed to ships, which are rather different and can move to avoid the worst ice features. That raised questions unfamiliar to civil engineers accustomed to steel, concrete, rock and soil, because ice is a totally different material of a remarkably unusual kind. In this book we explore the many issues that an engineer designing for the Arctic offshore will encounter and will have to respond to. Without apology, and because engineering is about human needs and desires, we begin with the human context, and consider the people who will be affected by offshore construction, and their diverse priorities. Next we examine the physical and biological environment. We then move on to ice as a material and how it responds to stress, a deeply controversial and difficult subject where the development of knowledge is still at an early stage. That leads us to the many different kinds of offshore structures, and to the factors that influence a choice between them. From there we move on to pipelines and transportation by tanker, and then to safety, environmental factors and the ultimate decommissioning and removal of structures we no longer need. Finally, we consider the implications of human factors and the people who will build and operate systems in the Arctic offshore. We are not the first to have written about these subjects. Four books have been a particular inspiration. Professor Bernard Michel of Université Laval, Quebec, devoted his career to ice research and was in the forefront of developing university courses in ice mechanics, and postgraduate research. His book Ice mechanics published in 1978 was a very valuable and comprehensive early contribution. Tim Sanderson s Ice mechanics: risks to offshore structures came out in 1988. Elegantly written, full of insight, not afraid to question the received opinion of the time, it remains a powerful source that repays rereading, even though the subject has moved on. Sadly, and to all our loss, Tim s health made it impossible for him to continue at the leading edge of ice mechanics. Peter Wadhams Ice in the ocean carries with it his unrivalled knowledge of the Arctic oceans and his delight in their beauty and strangeness. More recently, Willy Weeks magisterial On Sea Ice was published in 2010, and reflects the deep and broadly-based experience of a lifetime.
Preface ix We are grateful to many people we have worked with over the years, in many different places and on many different projects. In addition to the colleagues mentioned above, we would particularly like to thank Ainur Abuova, Razek Abdelnour, Gray Alexander, Norm Allyn, Ricardo Argiolas, Mike Ashby, Ravi Aurora, Eleanor Bailey, Anne Barker, Ken Been, Frank Bercha, Morten Bjerkås, Denis Blanchet, Steve Blasco, Bob Brown, Tom Brown, Jim Bruce, Steve Bruneau, Gus Cammaert, George Comfort, Max Coon, Greg Crocker, John Dempsey, Dave Dickins, Ken Downie, Rod Edwards, Tony Evans, Simon Falser, John Fitzpatrick, Ginny Frankenstein, Lindsey Franklin, Bob Frederking, Mark Fuglem, Lorne Gold, Dougal Goodman, Jed Hamilton, Willott Heerde, Kevin Hewitt, Chris Hill, John Hutchinson, Knut Høyland, Chris Heuer, Hans Jahns, Catherine Jahre-Nilsen, Waleed Jazrawi, Bengt Johansson, Michelle Johnston, Ian Jordaan, Ollie Kaustinen, Tuomo Kärnä, Arno Keinonen, John Kenny, Hans Kivisild, Ibrahim Konuk, Austin Kovacs, Rick Kry, Ivana Kubat, Glenn Lanan, Arny Lengkeek, George Li, Pavel Liferov, Sveinung Løset, Mauri Määttänen, Glenn Mainland, Bob Marcellus, Dan Masterson, Dmitri Matskevitch, Derek Mayne, Dave McGonigal, Richard McKenna, Michel Metge, Per-Olav Moslet, Derek Muggeridge, Karen Muggeridge, Charlie Neill, Don Nevel, Rune Nilsen, Peter Noble, Ravi Perera, Roger Pilkington, Anatoly Polomoshnov, Alan Ponter, Bob Pritchard, Matthew Quah, Terry Ralston, Jim Rice, Ron Ritch, Mohamed Sayed, Joachim Schwarz, Karl Shkhinek, Victor Smirnov, Dev Sodhi, Walt Spring, Alan Strandberg, Paul Stuckey, Gennady Surkov, Rocky Taylor, Graham Thomas, Garry Timco, Hendrik Tjiawi, Pavel Truskov, Paul Verlaan, Sergey Vernyayev, Stanislav Vershinin, David Walker, Cynthia Wang, Jeff Weaver, Alexandra Weihrauch, Mitch Winkler, Brian Wright, Pete Wiebe, Yap Kim Thow, Abzal Yergaliyev and Zheng Jiexin. We thank the many companies we have worked with, and particularly RJ Brown and Associates, Keppel Offshore, Panarctic Oils, Polar Gas, BP, ExxonMobil, Dome Petroleum, Imperial Oil, Elvary Neftegaz, AgipKCO, Total, Statoil and Shell. It should not be thought that those companies or the individuals listed would agree with all our conclusions. Some of this material was first put forward in the Arctic Engineering course OT5207 at the National University of Singapore, and we are grateful to the students on that course for their comments. Our determination is to make this book stimulating and enjoyable, on principle and not merely for the utilitarian reason that people engage more with subjects they find enjoyable. The mistakes and misunderstandings are our own,
x Arctic Offshore Engineering and we shall be grateful to anyone who points them out, or better still! argues with us. Most of all, we thank our wives Jane Palmer and Anne Murphy Croasdale for their infinite patience. Andrew Palmer Ken Croasdale Singapore, 16 March 2012 Calgary, 16 March 2012
Contents Foreword Preface 1. The Human Context 1 1.1 Introduction 1 1.2 The Peoples Native to the Arctic 2 1.3 Explorers 7 1.4 Developers 11 1.5 Outsiders 13 2. The Physical and Biological Environment 17 2.1 Climate 17 2.2 Permafrost and Land Ice 20 2.3 Sea Ice 26 2.3.1 Introduction 26 2.3.2 Oceanographic Context 28 2.3.3 The Structure of Ice 30 2.3.4 Ice Formation 32 2.4 Gathering Data about Sea Ice 37 2.4.1 Identifying Needs 37 2.4.2 Planning 38 2.4.3 Methods for Ice Thickness 39 2.4.4 Ice Movement 42 2.4.5 Ice Strength and Related Parameters 42 2.5 Biology 48 3. Ice Mechanics 55 3.1 Introduction 55 3.2 Creep 58 3.3 Fracture 61 3.3.1 Introduction 61 v vii xi
xii Arctic Offshore Engineering 3.3.2 Linear Elastic Fracture Mechanics 61 3.3.3 Nonlinear Fracture Mechanics 67 3.4 Elasticity 70 3.5 Plasticity 72 3.6 Broken Ice 75 3.7 In-situ Rubble Tests 79 3.7.1 Overview 79 3.7.2 The Direct Shear Test 80 3.7.3 The Punch Shear Test 83 3.7.4 The Pull Up Test 85 3.7.5 Summary of Results of in-situ Tests 88 3.7.6 Translation of Rubble Shear Strength into a Bearing Pressure (or pseudo crushing strength) 91 3.7.7 Confined Compression Test (indentation test) on Ice Rubble 92 3.8 Model Ice 94 4. Ice Forces on Structures in the Sea 101 4.1 Introduction 101 4.2 Alternative Design Concepts 104 4.3 Ice Forces 108 4.4 Ice Forces on Vertical-sided Structures 112 4.4.1 Alternative Modes 112 4.4.2 Creep 113 4.4.3 Buckling 113 4.4.4 Crushing: A Simple but Incorrect Approach 114 4.4.5 Crushing: Evidence from Measurements 115 4.4.6 Crushing: Empirical Representations of the Data 119 4.4.7 Crushing: Theory 121 4.5 Sloping-sided Structures 126 4.5.1 Introduction 126 4.5.2 Mechanics of Ice Interaction with Sloping-sided Structures 129 4.5.3 Adfreeze Effects 136 4.5.4 Experimental and Full Scale Data 138 4.5.5 Modifications for very Thick Ice 140 4.5.6 Velocity Effects 144 4.6 Local Ice Pressures 146 4.7 Ice Encroachment 151
Contents xiii 4.8 Model Tests 154 4.9 Ice-induced Vibrations 158 4.10 Ice Load Measurements on Platforms 162 5. Broken Ice, Pressure Ridges and Ice Rubble 181 5.1 Introduction 181 5.2 Formation of Ridges 181 5.3 Limit- Force Calculations 194 5.4 Multi-Year Ridges 199 5.4.1 Introduction 199 5.4.2 Ridge Breaking Analysis 199 5.5 Loads due to First-year Ridges 207 5.5.1 Introduction 207 5.5.2 Ridge Interaction with Vertical Structures 209 5.5.3 First-year Ridge Interaction on Upward Sloping Structures 214 5.5.4 First Year Ridge Interaction on Downward Sloping Structures 218 5.6 Structures in Shallow Water 225 5.6.1 Effects of Ice Rubble on Ice Loads 225 5.6.2 First-year Ridge Loads in Shallow Water 229 5.7 Multi-leg and Multi-hulled Platforms 232 5.7.1 Multi-leg (with Vertical Legs) 232 5.7.2 Multi-leg Structure with Conical Collars on the Legs 235 5.7.3 Multi-caisson Systems and Ice Barriers 235 5.8 Limit momentum (limit energy) Ice Loads 239 5.8.1 Principles and Application to a Vertical Structure 239 5.8.2 Sloping Structures 245 5.8.3 Iceberg Impact Loads 247 6. Ice Forces on Floating Platforms 251 6.1 Introduction 251 6.2 Background to Use of Floaters in Sea Ice 252 6.3 Loads on Floaters in Unmanaged Ice 254 6.4 Loads on Floaters in Managed Ice 259 6.5 Calibration against the Kulluk Data 262 6.6 Influencing Parameters 264 6.7 Typical Managed Ice Loads 268 7. Arctic Marine Pipelines and Export Systems 275 7.1 Introduction 275
xiv Arctic Offshore Engineering 7.2 Seabed Ice Gouging 276 7.2.1 Introduction 276 7.2.2 Ice Gouging: The First Model 279 7.2.3 Ice Gouging: Gouge Infill by Seabed Sediment Transport 282 7.2.4 Ice Gouging: Subgouge Deformation 285 7.2.5 Ice Gouging: Alternative Routes to a Choice of Safe Gouge Depth 289 7.2.6 Methods for Minimising Required Trench Depth 290 7.3 Strudel Scour 290 7.4 Construction 293 7.4.1 Introduction 293 7.4.2 Panarctic Drake F-76 Pipeline 298 7.4.3 Northstar Pipeline 303 7.4.4 Oooguruk Pipeline 305 7.4.5 Nikaitchuq Pipeline 306 7.5 Transportation by Tanker 306 8. Environmental Impact 315 8.1 Introduction 315 8.2 Oil in the Sea 317 8.2.1 Outside the Arctic 317 8.2.2 In the Arctic 320 8.3 Gas in the sea 322 8.4 Response and Oil cleanup 322 8.5 Effects of Structures on the Ice 327 8.6 Decommissioning 330 9. Human Factors and Safety 333 9.1 Context 333 9.2 Psychological Factors 334 9.3 Physical Factors 335 9.4 Platform Safety and Evacuation 335 9.5 Safety during On-Ice Activities 337 9.5.1 Introduction 337 9.5.2 Safe Loads on an Ice Sheet 340 9.6 Platform Reliability and Safety Factors 345 Index of Geographical locations 351 Index 355