handbook of offshore engineering, vol2

HANDBOOK OF OFFSHORE ENGINEERING SUBRATA K. CHAKRABARTI Offshore Structure Analysis, Inc. Plainfield, Illinois, USA Volume I1 2005 Amsterdam - Boston - Heidelberg - London - New York - Oxford Paris - San Diego - San Francisco - Singapore - Sydney - Tokyo Elsevier The Boulevard Langford Lane, Kidlington, Oxford OX5 lGB, UK Radarweg 29, PO Box 2 1 1, 1000 AE Amsterdam, The Netherlands First edition 2005 Reprinted 2005, 2006 Copyright Q 2005 Elsevier Ltd. All rights reserved No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means electronic, mechanical, photocopying, recording or otherwise without the prior written permission of the publisher Permissions may be sought directly from Elsevier’s Science & Technology Rights Department in Oxford UK: phone (+44) (0) 1865 843830; fax (+44) (0) 1865 853333; email: permissions@elsevier.com. 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Because of rapid advances in the medical sciences, in particular, independent verification of diagnoses and drug dosages should be made British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library Library of Congress Cataloging-in-Publication Data A catalog record for this book is available from the Library of Congress ISBN-13: 978-0-08-044568-7 (v01 1) ISBN-10: 0-08-044568-3 (VO~ 1) ISBN-13: 978-0-08-044569-4 (v01 2) ISBN-10: 0-08-044569-1 (VO~ 2) ISBN-1 3: 978-0-08-04438 1-2 (set) ISBN-10: 0-08-04438 1-8 (set) For information on all Elsevier publications i visit our website at books.elsevier.com Printed and bound in Great Britain 06 07 08 09 10 10 9 8 7 6 5 4 3 V PREFACE Due to the rapid growth of the offshore field, particularly in the exploration and develop- ment of offshore oil and gas fields in deep waters of the oceans, the science and engineering in this area is seeing a phenomenal advancement. This advanced knowledge is not readily available for use by the practitioners in the field in a single reference. Tremendous strides have been made in the last decades in the advancement of offshore exploration and production of minerals. This has given rise to developments of new concepts and structures and material for application in the deep oceans. This has generated an obvious need of a reference book providing the state-of-the art in offshore engineering. This handbook is an attempt to fill this gap. It covers the important aspects of offshore structure design, installation and operation. The book covers the basic background material and its application in offshore engineering. Particular emphasis is placed in the application of the theory to practical problems. It includes the practical aspects of the offshore structures with handy design guides, simple description of the various components of the offshore engineering and their functions. One of the unique strengths of the book is the impressive and encompassing presen- tation of current functional and operational offshore development for all those involved with offshore structures. It is tailored as a reference book for the practicing engineers, and should serve as a handy reference book for the design engineers and consultant involved with offshore engineering and the design of offshore structures. This book emphasizes the practical aspects rather than the theoretical treatments needed in the research in the field of offshore engineering. In particular, it describes the dos and don’ts of all aspects of offshore structures. Much hands-on experience has been incorporated in the write up and contents of the book. Simple formulas and guidelines are provided throughout the book. Detailed design calculations, discussion of software development, and the background mathematics has been purposely left out. The book is not intended to provide detailed design methods, which should be used in conjunction with the knowledge and guidelines included in the book. This does not mean that they are not necessary for the design of offshore structures. Typically, the advanced formulations are handled by specialized software. The primary purpose of the book is to provide the important practical aspects of offshore engineering without going into the nitty gritty of the actual detailed design. Long derivations or mathematical treatments are avoided. Where necessary, formulas are stated in simple terms for easy calculations. Illustrations are provided in these cases. Information is provided in handy reference tables and design charts. Examples are provided to show how the theory outlined in the book is applied in the design of structures. Many examples are borrowed from the deep-water offshore structures of interest today including their components, and material that completes the system. vi Contents of the handbook include the following chapters: Historical Development of Offshore Structures Novel and Marginal Field Offshore Structures Ocean Environment Loads and Responses Probabilistic Design of Offshore Structure Fixed Offshore Platform Design Floating Offshore Platform Design Mooring Systems Drilling and Production Risers Topside Facilities Layout Development Design and Construction of Offshore Pipelines Design for Reliability: Human and Organisational Factors Physical Modelling of Offshore Structures Offshore Installation Materials for Offshore Applications Geophysical and Geotechnical Design The book is a collective effort of many technical specialists. Each chapter is written by one or more invited world-renowned experts on the basis of their long-time practical experience in the offshore field. The sixteen chapters, contributed by internationally recognized offshore experts provide invaluable insights on the recent advances and present state-of-knowledge on offshore developments. Attempts were made to choose the people, who have been in the trenches, to write these chapters. They know what it takes to get a structure from the drawing board to the site doing its job for which it is designed. They work everyday on these structures with the design engineers, operations engineers and construction people and make sure that the job is done right. Chapter 1 introduces the historical development of offshore structures in the exploration and production of petroleum reservoirs below the seafloor. It covers both the earlier offshore structures that have been installed in shallow and intermediate water depths as well as those for deep-water development and proposed as ultra-deep water structures. A short description of these structures and their applications are discussed. Chapter 2 describes novel structures and their process of development to meet certain requirements of an offshore field. Several examples given for these structures are operating in offshore fields today. A few others are concepts in various stages of their developments. The main purpose of this chapter is to lay down a logical step that one should follow in developing a structural concept for a particular need and a set of prescribed requirements. The ocean environment is the subject of chapter 3. It describes the environment that may be expected in various parts of the world and their properties. Formulas in describing their magnitudes are provided where appropriate so that the effect of these environments on the structure may be evaluated. The magnitudes of environment in various parts of the world are discussed. They should help the designer in choosing the appropriate metocean conditions that should be used for the structure development. vii Chapter 4 provides a generic description of how to compute loads on an offshore struc- ture and how the structure responds to these loads. Basic formulas have been stated for easy references whenever specific needs arise throughout this handbook. Therefore, this chapter may be consulted during the review of specific structures covered in the handbook. References are made regarding the design guidelines of various certifying agencies. Chapter 5 deals with a statistical design approach incorporating the random nature of environment. Three design approaches are described that include the design wave, design storm and long-term design. Several examples have been given to explain these approaches. The design of fixed offshore structures is described in Chapter 6. The procedure follows a design cycle for the fixed structure and include different types of structure design including tubular joints and fatigue design. Chapter 7 discusses the design of floating structures, in particular those used in offshore oil drilling and production. Both permanent and mobile platforms have been discussed. The design areas of floaters include weight control and stability and dynamic loads on as well as fatigue for equipment, risers, mooring and the hull itself. The effect of large currents in the deepwater Gulf of Mexico, high seas and strong currents in the North Atlantic, and long period swells in West Africa are considered in the design development. Installation of the platforms, mooring and decks in deep water present new challenges. Floating offshore vessels have fit-for-purpose mooring systems. The mooring system selection, and design are the subject of Chapter 8. The mooring system consists of freely hanging lines connecting the surface platform to anchors, or piles, on the seabed, positioned some distance from the platform. Chapter 9 provides a description of the analysis procedures used to support the operation of drilling and production risers in floating vessels. The offshore industry depends on these procedures to assure the integrity of drilling and production risers. The description, selection and design of these risers are described in the chapter. The specific considerations that should be given in the design of a deck structure is described in Chapter 10. The areas and equipment required for deck and the spacing are discussed. The effect of the environment on the deck design is addressed. The control and safety requirements, including fuel and ignition sources, firewall and fire equipment are given. The objective of chapter 11 is to guide the offshore pipeline engineer during the design process. The aspects of offshore pipeline design that are discussed include a design basis, route selection, sizing the pipe diameter, and wall thickness, on-bottom pipeline stability, bottom roughness analysis, external corrosion protection, crossing design and construction feasibility. Chapter 12 is focused on people and their organizations and how to design offshore structures to achieve desirable reliability in these aspects. The objective of this chapter is to provide engineers design-oriented guidelines to help develop success in design of offshore structures. Application of these guidelines are illustrated with a couple of practical examples. The scale model testing is the subject of Chapter 13. This chapter describes the need, the modeling background and the method of physical testing of offshore structures in a Vlll small-scale model. The physical modeling involves design and construction of scale model, generation of environment in an appropriate facility, measuring responses of the model subjected to the scaled environment and scaling up of the measured responses to the design values. These aspects are discussed here. Installation, foundation, load-out and transportation are covered in Chapter 14. Installa- tion methods of the following sub-structures are covered: Jackets; Jack-ups; Compliant towers and Gravity base structures. Different types of foundations and their unique methods of installation are discussed. The phase of transferring the completed structure onto the deck of a cargo vessel and its journey to the site, referred to as the load-out and transportation operation, and their types are described. Chapter 15 reviews the important materials for offshore application and their corrosion issues. It discusses the key factors that affect materials selection and design. The chapter includes performance data and specifications for materials commonly used for offshore developments. These materials include carbon steel, corrosion resistant alloys, elastomers and composites. In addition the chapter discusses key design issues such as fracture, fatigue, corrosion control and welding. Chapter 16 provides an overview of the geophysical and geotechnical techniques and solutions available for investigating the soils and rocks that lay beneath the seabed. A project’s successful outcome depends on securing the services of highly competent contractors and technical advisors. What is achievable is governed by a combination of factors, such as geology, water depth, environment and vessel capabilities. The discussions are transcribed without recourse to complex science, mathematics or lengthy descriptions of complicated procedures. Because of the practical nature of the examples used in the handbook, many of which came from past experiences in different offshore locations of the world, it was not possible to use a consistent set of engineering units. Therefore, the English and metric units are interchangeably used throughout the book. Dual units are included as far as practical, especially in the beginning chapters. A conversion table is included in the handbook for those who are more familiar with and prefer to use one or the other unit system. This handbook should have wide applications in offshore engineering. People in the follow- ing disciplines will be benefited from this book: Offshore Structure designers and fabricators; Offshore Field Engineers; Operators of rigs and offshore structures; Consulting Engineers; Undergraduate & Graduate Students; Faculty Members in Ocean/Offshore Eng. & Naval Architectural Depts.; University libraries; Offshore industry personnel; Design firm personnel. Subrata Chakrabarti Technical Editor TABLE OF CONTENTS Preface v Abbreviations ix Conversion Factors List of Contributors Chapter 8 . lMooring Systems 663 8.1 Introduction 8.2 Requirements 8.3 Fundamentals 8.3.1 Catenary Lines 8.3.2 Synthetic Lines 8.3.3 Single Catenary Line Performance Characteristics 8.4 Loading Mechanisms 8.5 Mooring System Design 8.5.1 Static Design 8.5.3 Dynamic Design 8.5.5 Effective Water Depth 8.5.7 Uncertainty in Line Hydrodynamic Coefficients 8.5.8 Uncertainty in Line Damping and Tension Prediction 8.6 Mooring Hardware Components 8.6.1 Chain 8.6.2 Wire Rope 8.6.3 Properties of Chain and Wire Rope 8.6.4 Moorings 8.6.5 Connectors 8.6.6 Shipboard Equipment 8.6.7 Anchors 8.6.8 Turrets Industry Standards and Classification Rules 8.7.1 Certification 8.7.2 Environmental Conditions and Loads 8.7.4 Thruster-Assisted Mooring 8.7.5 Mooring Equipment 8.7.6 Tests 8.5.2 Quasi-Static Design 8.5.4 Synthetic Lines 8.5.6 Mooring Spreads 8.7 8.7.3 Mooring System Analysis 663 665 665 665 669 670 671 675 675 676 677 680 680 680 681 684 687 687 688 689 689 689 693 693 694 696 697 697 699 704 705 706 XVI Chapter 9 . Drilling and Production Risers 9.1 9.2 9.3 9.4 9.5 9.6 9.7 9.8 9.9 9.10 9.11 Introduction 9.2.1 Design Background 9.2.2 Influence of Metocean Conditions 9.2.3 Pipe Cross-Sect 9.2.4 Configuration ( 9.2.5 Vortex-Induced 9.2.6 Disconnected Riser 9.2.7 Connected Riser 9.2.8 Emergency Disconnect Sequence (EDS)!Drift-Off An 9.2.9 Riser Recoil after EDS Production Risers 9.3.1 Design Philosophy and Background 9.3.2 Top Tension Risers 9.3.3 Steel Catenary Risers (Portions contributed by Thanos Moros & Howard Cook, BP America, Houston, TX) 9.3.4 Diameter and Wall Thickness 9.3.5 9.3.6 In-Service Load Combinations 9.3.7 Accidental and Temporary Design Cases Vortex Induced Vibration of Risers 9.4.1 VIV Parameters 9.4.2 Simplified VIV Analysis 9.4.3 Examples of VIV Analysis 9.4.4 Available Codes VIV Suppression Devices Riser Clashing 9.6.1 Fatigue Analysis 9.7.1 9.7.2 Fatigue Due to Riser VIV 9.7.3 Fatigue Acceptance Criteria Fracture Mechanics Assessment 9.8.1 Engineering Critical Assessment 9.8.2 Paris Law Fatigue Analysis 9.8.3 Acceptance Criteria Reliability-Based Design Design Verification Design Codes Drilling Risers SCR Maturity and Feasibility Clearance, Interference and Layout Considerations First and Second Order Fatigue 9.8.4 Other Factors to Consi Chapter 10 . Topside Facilities Layout Development 709 709 714 715 715 715 718 726 730 744 757 166 768 769 779 802 817 824 826 828 828 828 829 832 832 832 836 836 838 842 845 848 849 850 851 851 851 851 853 854 861 10.1 Introduction 861 10.2 General Layout Considerations 862 10.2.1 General Requirements 10.2.2 Deepwater Facility Considerations 10.2.3 Prevailing Wind Direction 10.2.4 Fuel and Ignition Sources 10.2.5 Control and Safety Systems 10.2.6 Firewalls, Barrier Walls and Blast Walls 10.2.7 Fire Fighting Equipment 10.2.8 Process Flow 10.2.9 Maintenance of Equipment 10.2.10 Safe Work Areas and Operations 10.2.1 1 Storage 10.2.12 Ventilation 10.2.13 Escape Routes 10.3 Areas and Equipment 10.3.1 Wellhead Areas 10.3.2 Unfired Process Areas 10.3.3 Hydrocarbon Storage Tanks 10.3.4 Fired Process Equipment 10.3.5 Machinery Areas 10.3.6 Quarters and Utility Buildings 10.3.7 Pipelines 10.3.8 Flares and Vents Deck Placement and Configuration Horizontal Placement of Equipment on Deck Vertical Placement of Equipment 10.4 Deck Impact Loads 10.5 10.5.1 10.5.2 10.5.3 Installation Considerations 10.5.4 Deck Installation Schemes 10.6 Floatover Deck Installation 10.7 Helideck 10.8 Platform Crane 10.9 Practical Limit Analysis of Two Example Layouts 10.10 10.1 1 Example North Sea Britannia Topside Facility Chapter 11 . Design and Construction of Offshore Pipelines 11.1 Introduction 11.2 Design Basis 1 1.3 Route Selection and Marine Survey 11.4 Diameter Selection 11.4.1 Sizing Gas Lines 11.4.2 Sizing Oil Lines 11.5 Wall Thickness and Grade 11.5.1 Internal Pressure Containment (Burst ) xvii 864 865 866 867 869 869 869 869 870 870 870 871 872 872 872 872 873 873 873 874 874 874 875 876 876 876 877 877 879 881 883 883 883 887 891 89 1 892 893 893 893 895 895 896 11.5.2 Collapse Due to External Pressure 897 xviii 11.5.3 Local Buckling Due to Bending and External Pressure 11.5.4 Rational Model for Collapse of Deepwater Pipelines 11.6 Buckle Propagation 11.7 Design Example 11.7.1 Preliminary Wall Thickness for Internal Pressure Containment (Burst) 11.7.2 Collapse Due to External Pressure 1 1.7.3 Local Buckling Due to Bending and External Pressure 11.7.4 Buckle Propagation 11.8.1 Soil Friction Factor 11.8.2 Hydrodynamic Coefficient Selection 1 1.8.3 Hydrodynamic Force Calculation 11.8.4 Stability Criteria 11.9.1 11.9.2 Design Example 11 .IO External Corrosion Protection 11.10.1 Current Demand Calculations 11.10.2 Selection of Anode Type and Dimensions 11.10.3 Anode Mass Calculations 11.10.4 Calculation of Number of Anodes 1 1.10.5 Design Example 11.11 Pipeline Crossing Design 11.8 On-Bottom Stability 11.9 Bottom Roughness Analysis Allowable Span Length on Current-Dominated Oscillations 11.12 Construction Feasibility 11.12.1 J -lay Installatio 11.12.3 Reel-lay 11.12.4 Towed Pipelines 11.12.2 S-lay Chapter 12 . Design for Reliability: Human and Organisational Factors 12.1 Introduction 12.2.1 Operator Malfunctions 12.2.2 Organisational Malfunctions 12.2.3 Structure, Hardware, Equipment Malfunctions 12.2.4 Procedure and Software Malfunctions 12.2.5 Environmental Influences 12.3.1 Quality 12.3.2 Reliability 12.3.3 Minimum Costs Approaches to Achieve Successful Designs 12.4.1 Proactive Approaches 12.2 Recent Experiences of Designs Gone Bad 12.3 Design Objectives: Life Cycle Quality, Reliability a 12.4 899 900 905 907 908 910 911 911 912 913 913 914 914 914 916 917 917 918 919 919 920 920 921 927 929 932 933 933 939 939 939 942 944 946 947 948 948 948 949 952 957 958 [...]... initial position The results of a typical analysis are presented in fig 8.10 The steady component of environmental force from wind, current and wave drift effects is applied to the vertical axis of this diagram to obtain the resultant static component of vessel offset from the horizontal axis The slope of the force curve at this offset gives an equivalent linear stiffness C, of the mooring system in the... 16.11 16.12 16.13 16.14 Index 1264 Handbook of Offshore Engineering S Chakrabarti (Ed.) C 2005 Elsevier Ltd All rights reserved 663 Chapter 8 Mooring Systems David T Brown BPP Technical Services Ltd., Loizdon, UK 8.1 Introduction It is essential that floating offshore vessels have fit-for-purpose mooring systems The mooring system consists of freely hanging lines connecting the surface... a significant length at A l , to none at A4 From a static point of view, the cable tension in the vicinity of points A is due to the total weight in sea water of the suspended line length The progressive effect of line lift-off from the seabed due to the horizontal vessel movement from A l to A4 increases line tension in the vicinity of points A This feature, coupled with the simultaneous decrease... 14.10.2 14.10.3 14.10.4 14.10.5 14.10.6 Methods of Pipeline Installation Types of Risers Methods of Ris Vessel and Equ Analyses Required Chapter 15 Materials for Offshore Applications 15.1 Introduction 15.1.1 Factors Affecting Mat 15.1.2 Classification of Materials 15.2 Structural Steel 15.3 Topside Materials... value of installation stiffness should be used to calculate offsets in the period after installation Drift stiffness - Cyclic loading under moderate weather conditions, applicable to the mooring during a high proportion of the time, shows a mean variation of tension and elongation which is represented by the drift stiffness A minimum estimated value of drift stiffness should be used to calculate offsets... Water Depth Combinations of tide change plus storm surge, for example, together with alterations in vessel draught, because of ballasting, storage and offloading etc result in changes in the elevation of the vessel fairleads above the seabed The example given in fig 8.14 presents the range of elevation levels for a 120,000 ton dwt floating production unit in a nominal water depth of 136 m This elevation... fibre ropes are sensitive to cutting by sharp objects and there have been reports of damage by fish bite A number of rope types such as high modulus polyethylene (HMPE) are buoyant in sea water; other types weigh up to 10% of a steel wire rope of equal strength Synthetic fibre lines used within taut moorings require the use of anchors that are designed to allow uplift at the seabed These include suction... restoring force characteristics of a single catenary line plotted against offset (non-dimensionalised by water depth) for variations respectively in line weight and initial tension Both figures emphasise the hardening spring characteristics of the mooring with increasing offset as discussed above While this is a specific example, several observations may be made regarding design of a catenary system from... results Mooring Systems 671 3io HlTUL TLNEIOH 0 2 b OFFSET (a) Effect of changing line weight -initial tension = 135 kN / LN b ~ 1 1 1 0 X WATER PEPTH (b) Effect of changing initial tension -weight = 450 kg/m Figure 8.6 Restoring force for a single catenary line (depth = 150 m) Figure 8.6a shows the effect of line weight for a single line in 150 m of water with 135 kN initial tension Under these conditions,... Dimensions 1016 1019 13.3.2 Generation of Waves, Wind and Current 1019 13.4 Modelling of Environment 13.4.1 Modelling of Waves 13.4.2 Unidirectional Random Waves 13.4.3 Multi-directional Random Waves 1020 1021 13.4.4 White Noise Seas 13.4.5 Wave Grouping 1022 13.4.6 Modelling of Wind 13.4.7 Modelling of Current 1023 1026 13.5 Model . and Construction of Offshore Pipelines Design for Reliability: Human and Organisational Factors Physical Modelling of Offshore Structures Offshore Installation Materials for Offshore Applications. with offshore engineering and the design of offshore structures. This book emphasizes the practical aspects rather than the theoretical treatments needed in the research in the field of offshore. design of offshore structures. Typically, the advanced formulations are handled by specialized software. The primary purpose of the book is to provide the important practical aspects of offshore