(Surface Production Operations) DISCLAIMER This text contains descriptions, statements, equations, procedures, methodology, interpretations, and other written matter and information, hereinafter collectively called "contents," that have been carefully consid- ered and prepared as a matter of general information. The contents are believed to reliably represent situations and conditions that have occurred or could occur, but are not represented or guaranteed as to the accuracy or application to other conditions or situations. There are many variable condi- tions in production facility design and related situations, and the authors have no knowledge or control of their interpretation. Therefore, the contents and all interpretations and recommendations made in connection herewith are presented solely as a guide for the user's consideration, investigation, and verification. No warranties of any kind, whether expressed or implied, are made in connection therewith. The user is specifically cautioned, reminded, and advTised that any use or interpretation of the contents and resulting use or application thereof are made at the sole risk of the user. In production facility design there are many proprietary designs and tech- niques. We have tried to show designs and techniques in a generic nature where possible. The user must assure himself that in actual situations it is appropriate to use this generic approach. If the actual situation differs from the generic situation in design or lies outside the bounds of assumptions used in the various equations, the user must modify the information con- tained herein accordingly. In consideration of these premises, any user of the contents agrees to indemnify and hold harmless the authors and publisher from all claims and actions for loss, damages, death, or injury to persons or property. I Surface Production Operations Design of Oil-Handling Systems and Facilities Ken Arnold Maurice Stewart SECOND EDITION Surface Production Operations VOLUME 1 Design of Oil-Handling Systems and Facilities Copyright © 1989, 1999 by Butterworth-Heinemann. All rights reserved. Printed in the United States of America. This book, or parts thereof, may not be reproduced in any form without permission of the publisher. Originally published by Gulf Publishing Company, Houston, TX. For information, please contact: Manager of Special Sales Butterworth-Heinemann 225 Wildwood Avenue Woburn, MA 01801-2041 Tel: 781-904-2500 Fax: 781-904-2620 For information on all Butterworth-Heinemann publications available, contact our World Wide Web home page at: http://www.bh.com 10 9 8 7 6 5 4 Library of Congress Cataloging-in-Publication Data Arnold, Ken, 1942- Design of oil-handling systems and facilities / Ken Arnold, Maurice Stewart. — 2nd ed. p. cm. — (Surface production operations; v. 1) Includes index. ISBN 0-88415-821-7 (alk. paper) 1. Petroleum engineering—Equipment and supplies. 2. Oil fields—Equipment and supplies. 3. Oil fields—Production methods. I. Stewart, Maurice. II. Title. III. Series. TN871.5.A74 1998 665.5—dc21 97-38110 CIP Printed in the United States of America. Printed on acid-free paper (°o). iv Contents Acknowledgments xi Preface xiii CHAPTER 1 The Production Facility 1 • Introduction, 1 Making the Equipment Work, 16 Facility Types, 18 CHAPTER 2 Choosing a Process 26 Introduction, 26 Controlling the Process, 26 Operation of a Control Valve 26, Pressure Control 29, Level Control 30, Temperature Control 30, Flow Control 31 Basic System Configuration, 31 Wellhead and Manifold 31, Separation 31, Oil Treating 38, Lease Automatic Custody Transfer (LACT) 40, Pumps 42, Water Treating 43, Compressors 43, Gas Dehydrators 46 Well Testing, 48 Gas Lift, 51 Offshore Platform Considerations, 54 Overview 54, Modular Construction 55, Equipment Arrangement 55 CHAPTER 3 Fluid Properties 58 Introduction, 58 Basic Principles, 58 Specific Gravity and Density 58, Viscosity 64 v Flash Calculations, 69 Characterizing the Flow Stream, 87 Molecular Weight of Gas 87, Gas Flow Rate 88, Liquid Molecular Weight 89, Specific Gravity of Liquid 90, Liquid Flow Rate 92, The Flow Stream 92 Approximate Flash Calculations, 93 Other Properties, 95 CHAPTER 4 Two-Phase Oil and Gas Separation 101 Introduction, 101 Factors Affecting Separation, 102 Equipment Description, 102 Horizontal Separators 102, Vertical Separators 104, Spherical Separators 104, Other Configurations 105, Scrubbers 107 Horizontal vs. Vertical Vessel Selection, 108 Vessel Internals, 109 Inlet Diverters 109, Wave Breakers 111, Defoaming Plates 111, Vortex Breaker 112, Mist Extractor 112 Potential Operating Problems, 115 Foamy Crudes 115, Paraffin 116, Sand 117, Liquid Carryover and Gas Blowby 117 Theory, 117 Settling 117, Drop Size 121, Retention Time 122, Re-entrainment 122 Separator Sizing, 122 Horizontal Separators 122, Procedure for Sizing Horizontal Separators 126, Vertical Separators 126 Examples, 129 Sizing a Vertical Separator 129, Sizing a Horizontal Separator 133 References, 134 CHAPTER 5 Oil and Water Separation 135 Introduction, 135 Equipment Description, 136 Horizontal Separators 136, Vertical Separators 140, Horizontal vs. Vertical Selection 142 vi Vessel Internals, 143 Coalescing Plates 143, Sand Jets and Drains 143 Emulsions, 144 Theory, 144 Gas Separation 144, Oil/Water Settling 144, Water Droplet Size in Oil 144, Oil Droplet Size in Water 145, Retention Time 145 Separator Sizing, 145 Horizontal Separators 146, Settling Equation 148, Vertical Separators 151 Examples, 154 Sizing a Vertical Three-Phase Separator 154, Sizing a Horizontal Three-Phase Separator 156 CHAPTER 6 Crude Oil Treating Systems 160 Introduction, 160 Emulsion Treating Theory, 161 Forming Emulsions 161, Emulsifying Agent 164, Demulsifiers 165 Gravity Separation, 167 Coalescence 168, Viscosity 169, Temperature Effects 170, Heat Input Equations 174, Water Droplet Size and Retention Time 175, Coalescing Media 175, Electrostatic Coalescers 176 Treating Equipment, 177 Vertical Treaters 177, Horizontal Treaters 180, Electrostatic Treaters 181 Equipment Sizing and Theory, 182 Settling Equations 182, Retention Time Equations 184, Water Droplet Size 185 Design Procedure, 188 Examples, 189 Sizing a Horizontal Treater 189, Sizing a Vertical Treater 191 References, 192 CHAPTER 7 Produced-Water Treating Systems 194 Introduction, 194 System Description, 195 vii Theory, 197 Gravity Separation 197, Dispersion 198, Coalescence 198, Flotation 199 Treating Equipment, 199 Settling Tanks and Skimmer Vessels 199, Skimmer Sizing Equations 202, Plate Coalescers 207, Skimmer/Coalescers 214, Precipitators/Coalescing Filters 215, Free-Flow Turbulent Coalescers (SP Packs) 215, Flotation Units 218, Hydrocyclones 223, Disposal Piles 225, Skim Pile 228 Drain Systems, 230 Information Required for Design, 230 Influent Water Quality, 231 Produced Water 231, Soluble Oil 232, Deck Drainage 233 Equipment Selection Procedure, 233 Equipment Specification, 236 Example: Design the Produced-Water Treating System for the Data Given, 237 CHAPTER 8 Pressure Drop in Piping 244 Introduction, 244 Basic Principles, 245 Reynolds Number 245, Flow Regimes 247, Bernoulli's Theorem 247, Darcy's Equation 248, Moody Friction Factor 249 Fluid Flow Equations, 251 Liquid Flow 251, Gas Flow 254, Two-Phase Flow 263 Head Loss in Valves and Pipe Fittings, 273 Resistance Coefficients 274, Flow Coefficient 274, Equivalent Length 277, Laminar Flow Coefficient 278 Example Pressure Drop Calculations, 278 Pressure Drop in Liquid Line 278, Pressure Drop in Gas Line 281, Pressure Drop in Two-Phase Line 284 CHAPTER 9 Choosing a Line Size and Wall Thickness 285 Introduction, 285 viii Line Size Criteria, 286 Erosional Flow 286, Liquid Lines 289, Gas Lines 291, Two-Phase Flow 295 Wall Thickness Criteria, 299 Standards and Requirements 299, General Hoop Stress Formula for Thin Wall Cylinders 300 Pressure Rating Classes, 313 Industry Standards 313, API 6A 314, Pipe, Valve, and Fitting Specifications 314 Examples, 324 Liquid Line 324, Gas Line 329, Two-Phase Line 330 References, 332 CHAPTER 1O Pumps 333 Introduction, 333 Pump Classification, 333 Centrifugal Pumps, 334 Reciprocating Pumps, 339 Diaphragm Pumps, 344 Rotary Pumps, 345 Multiphase Pumps, 347 Basic Principles, 347 Head 347, Horsepower 349, Net Positive Suction Head (NPSH) 350 Basic Selection Criteria, 352 CHAPTER 11 Centrifugal Pumps 355 Introduction, 355 Multiple Pump Installations, 356 Pump Specific Speed, 358 Codes and Standards, 358 Generic Types of Centrifugal Pumps, 359 ANSI Pump 359, Single-Stage API Pump 361, Vertical In-Line Pump 362, API Multistage Split Case Pump 364, API Barrel Pumps 364, Sump Pump 365, ix