Advanced Natural Gas Engineering Xiuli Wang XGAS Michael Economides University of Houston Gulf Publishing Company Houston, Texas Advanced Natural Gas Engineering Copyright © 2009 by Gulf Publishing Company, Houston, Texas. All rights reserved. No part of this publication may be reproduced or transmitted in any form without the prior written permission of the publisher. Gulf Publishing Company 2 Greenway Plaza, Suite 1020 Houston, TX 77046 10 9 8 7 6 5 4 3 2 1 Library of Congress Cataloging-in-Publication Data forthcoming Printed in the United States of America ∞ Printed on acid-free paper. Editing, design and composition by TIPS Technical Publishing, Inc List of Figures Figure 1–1 Artist’s rendition of onshore petroleum reservoir...2 Figure 1–2 Artist’s rendition of offshore petroleum reservoir...3 Figure 1–3 Sedimentary environment.......................................4 Figure 1–4 Grain sizes of sediments..........................................5 Figure 1–5 Natural gas reservoirs and trapping mechanisms ...7 Figure 1–6 Gas cap.....................................................................7 Figure 1–7 Phase diagram........................................................10 Figure 1–8 The gas deviation factor for natural gases.............15 Figure 1–9 Pseudocritical properties of natural gases..............17 Figure 1–10 Pseudocritical temperature adjustment factor, e ..21 3 Figure 1–11 Viscosity of natural gases at 1 atm.........................26 Figure 1–12 Viscosity ratio at elevated pressures and temperatures..........................................................26 Figure 1–13 Viscosity of gases at 1 atm.....................................27 Figure 2–1 Offshore seismic data acquisition..........................37 Figure 2–2 S-wave impedance from AVO inversion for an offshore natural gas bearing structure...................39 Figure 2–3 Calculated Poisson ratios for the zone of interest in Figure2–2...........................................................39 Figure 2–4 Seismic attribute of a structure: Ratios of compressional-reflection to shear-reflection amplitudes..............................................................40 Figure 2–5 Drilling rig components........................................42 xix xx List of Figures Figure 2–6 Measured versus extrapolated from correlations drilling fluid densities at high pressures................46 Figure 2–7 Measured drilling fluid densities of four fluids at depth and at predicted temperatures and pressures.................................................................46 Figure 2–8a Onshore wellbore example....................................50 Figure 2–8b Offshore wellbore example....................................51 Figure 2–9 Selected completion types.....................................51 Figure 2–10 Gas critical flow rate versus flowing tubing pressure for Example2–5.......................................55 Figure 3–1 Steady-state flow....................................................63 Figure 3–2 Production versus flowing bottomhole pressure for Example3–1........................................................67 Figure 3–3 A sketch of an openhole vertical well and its cross section...........................................................75 Figure 3–4 Turbulence effects in both horizontal and vertical wells...........................................................81 Figure 3–5 Effects of index of permeability anisotropy..........82 Figure 3–6 Pushing the limits: maximum J with constraints...88 D Figure 3–7 Folds of increase between fractured and unfractured wells...................................................94 Figure 3–8 Fluid flow from reservoir to a transverse fracture....95 Figure 3–9 Chart of iterative calculation procedure................97 Figure 3–10 Productivity comparison among vertical and horizontal wells with and without fracture...........98 Figure 3–11 Skin versus permeability in the single transversely fractured horizontal well.......................................99 Figure 3–12 Flow geometry in pipe.........................................100 Figure 3–13 Well deliverability for Example3–9, k =1 md, D = 3 in..............................................................105 tbg Figure 3–14 Well deliverability for Example3–9, k =10 md, D = 3 in..............................................................105 tbg Figure 3–15 Well deliverability for Example3–9, k =10 md, D =6.3in..............................................................106 tbg Figure 3–16 Material balance for Example3–10.....................108 Figure 3–17 Production rate, reservoir pressure, and cumulative recovery for Example3–10...............109 List of Figures xxi Figure 4–1 Generalized gas processing schematic.................117 Figure 4–2 Forces on liquid droplet.......................................119 Figure 4–3 Vertical three-phase separator.............................124 Figure 4–4 Obtain G from the downcomer allowable flow...128 Figure 4–5 Two-phase vertical separator...............................135 Figure 4–6 Three-phase horizontal separator..............................140 Figure 4–7 Three-phase horizontal separator with a weir.....146 Figure 4–8 Water content of sweet natural gas.....................153 Figure 4–9 Water content correction for sour natural gas....155 Figure 4–10 Hydrate formation prediction.............................158 Figure 4–11 A sketch of a typical glycol dehydration process 161 Figure 4–12 Gas capacity for packed glycol gas absorbers forg = 0.7 at 100°F..............................................161 g Figure 4–13 Trays or packing required for glycol dehydrators...163 Figure 5–1 Economically preferred options for monetizing stranded natural gas.............................................173 Figure 5–2 Basic pipeline capacity design concept................173 Figure 5–3 Diagram for Example5–1....................................176 Figure 5–4 Moody diagram....................................................178 Figure 5–5 Pipeline and compressor station for Example5–2...179 Figure 5–6 Work needed to compress gas from p to p ........181 1 2 Figure 5–7 Loading and offloading terminal for LNG and CNG..............................................................186 Figure 5–8 Regions actively investigating CNG projects.......187 Figure 5–9 Schematic of a CNG vessel...................................189 Figure 5–10 Schematic of a CNG vessel...................................190 Figure 5–11 Gas deviation factor Z as function of pressure and temperature for natural gas..........................190 Figure 5–12 Value of ZT/p as function of pressure and temperature for natural gas.................................191 Figure 5–13 “Hub-and-Spoke” (left) and “Milk-Run” (right) paths for CNG distribution to N receiving sites (terminals T ,…,T ).............................................193 1 N Figure 5–14 Potential “Hub-and-Spoke” scheme for CNG distribution to island countries in the Caribbean Sea with large consumption of electricity...........194 xxii List of Figures Figure 5–15 Potential “Milk-Run” scheme for CNG distribution to island countries in the Caribbean Sea with small consumption of electricity..........195 Figure 5–16 Scheduling of gas delivery from a single source to a single delivery site using two CNG vessels...195 Figure 5–17 Scheduling of gas delivery from a single source to a single delivery point using three CNG vessels..195 Figure 5–18 Scheduling of gas delivery from a single source to a single delivery site using n CNG vessels.......196 Figure 5–19 Minimum number of vessels, n , required min to implement a CNG delivery schedule corresponding to various ratios of consumptions rates over loading rates................197 Figure 5–20 Dependence of vessel capacity and total fleet capacity on the number of vessels, n, for Example5–4.........................................................200 Figure 5–21 Dependence of vessel capacity and total fleet capacity on the number of vessels, n, for Example5–5.........................................................203 Figure 5–22 Schedule development for CNG distribution by n similar vessels to N receiving sites serviced successively on a cyclical path as shown in Figure5–13...........................................................204 Figure 5–23 Destinations for CNG delivery using Milk-Run scheme.................................................................207 Figure 6–1 Typical LNG plant block flow diagram................211 Figure 6–2 Typical natural gas/refrigerant cooling curves....213 Figure 6–3 Simple cooler/condenser......................................216 Figure 6–4 Three-stage process for liquefaction....................218 Figure 6–5 Simple flash condensation process......................220 Figure 6–6 Simplified schematic of Linde process.................221 Figure 6–7 APCI process.........................................................223 Figure 6–8 p-H diagram for methane....................................224 Figure 6–9 Simplified APCI process schematic......................225 Figure 6–10 Typical propane precooled mixed refrigerant process..................................................................228 Figure 6–11 Optimized cascade process..................................229 Figure 6–12 Single mixed refrigerant loop..............................230 List of Figures xxiii Figure 6–13 Mixed fluid cascade process (MFCP)......................232 Figure 6–14 IFP/Axens Liquefin™ process.................................233 Figure 6–15 Schematic overview of the DMR refrigeration cycles....................................................................235 Figure 6–16 LNG carrier size progression................................236 Figure 6–17 Moss type LNG tanker.........................................237 Figure 6–18 Membrane type LNG tanker................................237 Figure 7–1 Basic flowchart of indirect conversion of natural gas to liquids through syngas and Fischer-Tropsch synthesis....................................246 Figure 7–2 Relative values of equilibrium constants for steam reforming and water gas shift Reactions (7.14) and (7.15), respectively.............253 Figure 7–3 Equilibrium compositions for steam reforming at 20atm and stoichiometry H O/CH = 3. 2 4 Methane converson is complete at about 1,000°C. The production of CO from the water 2 gas shift reaction is maximum around 700°C....253 Figure 7–4 The ratio of H /CO as a function of the ratio of 2 steam/methane for Example7–3.........................257 Figure 7–5 Relative activity of transition metal catalysts for steam reforming..........................................................257 Figure 7–6 Configuration of a steam reforming reactor at multiple levels of detail: (a) tube bundle in furnace, (b) reactor tube, and (c) catalyst pellet. Heat can be provided to the long tubes in a number of ways, not shown................................259 Figure 7–7 Autothermal reforming reactor...........................261 Figure 7–8 Configuration of ceramic membrane partial oxidation reactor (not drawn to scale)................263 Figure 7–9 Timeline of Fischer-Tropsch synthesis................264 Figure 7–10 Thermodynamics of the Fischer-Tropsch synthesis of decane (n = 10) via the reaction 10CO + 20H → C H + 10H O..........................267 2 10 20 2 Figure 7–11 Initiation step of Fischer-Tropsch reactions........269 Figure 7–12 Chain growth step of Fischer-Tropsch reactions...269 Figure 7–13 Chain termination step of Fischer-Tropsch reactions resulting in alkanes (first two) or alkenes (third)......................................................269 xxiv List of Figures Figure 7–14 Theoretical dependence of mass fraction W of n Fischer-Tropsch products C –C on the chain 1 20 growth probability, a, according to the AFS Eq.(7.44)..............................................................270 Figure 7–15 Theoretical cumulative distribution of Fischer- Tropsch products according to the AFS Eq.(7.44), for different values of growth probability, a.......271 Figure 7–16 Theoretical cumulative distribution of Fischer- Tropsch products according to the AFS Eq.(7.44), for different values of the growth probability, a...272 Figure 7–17 Theoretical composition of fuel product from Fischer-Tropsch synthesis according to the AFS Eq.(7.44), for different values of the growth probability, a........................................................272 Figure 7–18 Theoretical composition of fuel products from Fischer-Tropsch synthesis according to the AFS Eq.(7.44), for different values of the growth probability, a........................................................275 Figure 7–19 Types of Fischer-Tropsch reactors.............................279 Figure 7–20 Typical compositions of Fischer-Tropsch products before and after hydrocracking............283 Figure 8–1 U.S. Underground natural gas storage facilities in the lower 48 states...........................................291 Figure 8–2 Storage measures..................................................293 Figure 8–3 p/Z curve vs cumulative gas storage....................296 Figure 8–4 p/Z vs gas storage for Example8–2......................297 Figure 8–5 p/Z versus G plot for Example8–3......................299 s Figure 9–1 The world energy mix, past, present, and future...305 Figure 9–2 World’s main natural gas proven reserves holders compared to oil and coal........................309 Figure 9–3 The Wind potential of the United States at 50 land and offshore............................................311 Figure 9–4 Net electricity generation by energy source...........326 Figure 9–5 Wind electricity generation cost for three US cities at discount rates (6%, 8%, and 10%)....326 Figure 9–6 Solar electricity generation cost for three US cities at discount rates (6%, 8%, and 10%)....327 Figure 9–7 Historical CO emissions from electric power 2 sector....................................................................329 List of Tables Table 1–1 Molecular Weights and Critical Properties of Pure Components of Natural Gases........................................13 Table 1–2 Results for Example1–1..................................................13 Table 1–3 Calculated Results for Example1–3................................18 Table 1–4 PseudoCritical Properties for Example1–4.....................22 Table 1–5 Correlations to Calculate Pseudocritical Properties fromg..............................................................................29 g Table 1–6 Typical Units for Reservoir and Production Engineering Calculations................................................33 Table 2–1 Results from Example2–5...............................................54 Table 2–2 API Recommended Performance Casing.........................56 Table 3–1 Correlations for non-Darcy Coefficient..........................61 Table 3–2 Results for Example3–1..................................................67 Table 3–3 PVT Table for Example3–3.............................................74 Table 3–4 Well and Reservoir Characteristics for Example3–4......79 Table 3–5 Results for Example3–4..................................................81 Table 3–6 Effects of Index of Permeability Anisotropy...................82 Table 3–7 Constants a and b............................................................91 Table 3–8 Material Balance Calculations for Example3–10.........110 Table 4–1 Types of Liquid/Gas Separators.....................................118 Table 4–2 Separator K Factors........................................................121 Table 4–3 k Values for Some Systems...........................................123 s Table 4–4 Symbols used in Figure4–3...........................................125 xxv