Natural Gas Hydrates (eBook)

Front cover 1
Natural gas hydrates: A guide for engineers 4
Copyright page 5
Contents 8
Preface to second edition 14
Preface to first edition 16
Acknowledgements 18
Chapter one: Introduction 20
1.1 Natural gas 21
1.1.1 Sales gas 21
1.1.2 Hydrates 22
1.2 The water molecule 22
1.2.1 The normal boiling point of water 22
1.2.2 Enthalpy of vaporization 24
1.2.3 Expansion upon freezing 25
1.3 Hydrates 28
1.4 Water and natural gas 30
1.4.1 Free-water 30
1.5 Heavy water 31
1.6 Additional reading 32
1.7 Units 32
Bibliography 33
References 33
Appendix 1A. A Periodic Table of the Elements 34
Chapter two: Hydrate types and formers 36
2.1. Type I hydrates 36
2.1.1 Type I formers 37
2.2. Type II hydrates 38
2.2.1 Type II formers 39
2.3. Type H hydrates 39
2.3.1 Type H formers 39
2.4. The size of the guest molecule 39
2.5. n-Butane 41
2.6. Other hydrocarbons 41
2.7. Cyclopropane 41
2.8. 2-Butene 42
2.9. Hydrogen and helium 42
2.9.1 Update 42
2.10. Chemical properties of potential guests 43
2.11. Liquid hydrate formers 43
2.12. Hydrate forming conditions 43
2.12.1 Pressure-Temperature 43
2.12.2 Composition 44
2.12.3 Caution 46
2.12.4 Nitrogen 47
2.12.5 Ethylene 47
2.12.6 Propylene 48
2.13. V+L[sub(A)]+H Correlations 49
2.13.1 Ethylene 50
2.14. L[sub(A)]+L[sub(H)]+H Correlations 54
2.15. Quadruple points 55
2.15.1 Cyclopropane 56
2.16. Other hydrate formers 56
2.16.1 Freons® 57
2.16.2 Halogens 57
2.16.3 Noble gases 57
2.16.4 Air 57
2.16.5 Others 57
2.17. Hydrate formation at 0°C 58
2.18. Mixtures 58
2.18.1 Mixtures of the same type 58
2.18.2 Type I plus Type II 59
2.18.3 Azeotropy 60
2.18.4 Mixtures with non-formers 61
Appendix 2A. Water content of the fluid in equilibrium with hydrate for pure components 63
References 68
Chapter three: Hand calculation methods 70
3.1 The gas gravity method 70
3.1.1 Verifying the approach 73
3.2 The K-Factor method 76
3.2.1 Calculation algorithms 77
3.2.2 Liquid hydrocarbons 79
3.2.3 Computerization 80
3.2.4 Comments on the accuracy of the K-factor method 81
3.2.5 Mann et al. 83
3.3 Baillie-Wichert method 83
3.4 Other correlations 86
3.4.1 Makogon 90
3.4.2 Kobayashi et al. 90
3.4.3 Motiee 91
3.4.4 Østergaard et al 91
3.4.5 Towler and Mokhatab 91
3.5 Comments on all the methods 92
3.5.1 Water 92
3.5.2 Non-formers 93
3.5.3 Isobutane vs. n-butane 93
3.5.4 Quick comparison 94
3.5.5 Sour natural gas 96
Appendix 3A. Katz K-Factor charts 102
References 112
Chapter four: Computer methods 114
4.1 Phase equilibrium 114
4.2 van der Waals and Platteeuw 115
4.3 Parrish and Prausnitz 116
4.4 Ng and Robinson 117
4.5 Calculations 117
4.5.1 Compositions 118
4.6 Commercial software packages 119
4.7 The accuracy of these programs 119
4.7.1 Pure components 120
4.7.2 Mixtures 123
4.7.3 Sour gas 127
4.8 Dehydration 128
4.9 Margin of error 129
References 131
Chapter five: Inhibiting hydrate formation with chemicals 132
5.1 Freezing point depression 133
5.2 The Hammerschmidt equation 136
5.3 The Nielsen-Bucklin equation 138
5.4 A new method 138
5.4.1 A chart 139
5.4.2 Accuracy of the new method 141
5.5 Brine solutions 143
5.5.1 McCain method 145
5.6 Østergaard et al. 145
5.7 Comment on the simple methods 149
5.8 Advanced calculation methods 149
5.9 A word of caution 150
5.10 Ammonia 151
5.11 Acetone 151
5.12 Inhibitor vaporization 152
5.12.1 A more theoretical approach 154
5.12.2 Inhibitor losses to the hydrocarbon liquid 156
5.13 A comment on injection rates 158
5.14 Safety considerations 158
5.15 Price for inhibitor chemicals 158
5.16 Low dosage hydrate inhibitors 159
5.16.1 Kinetic inhibitors 160
5.16.2 Anticoagulants 161
Bibliography 167
References 167
Chapter six: Dehydration of natural gas 170
6.1 Water content specification 170
6.2 Glycol dehydration 171
6.2.1 Liquid desiccants 171
6.2.2 Process description 172
6.2.3 Short Cut Design Method 175
6.2.4 Approximate capital cost 178
6.3 Mole sieves 179
6.3.1 Process description 179
6.3.2 Simplified modeling 179
6.4 Refrigeration 183
6.4.1 Process description 184
6.4.2 Glycol injection 185
References 188
Chapter seven: Combating hydrates using heat and pressure 190
7.1 Plugs 190
7.2 The use of heat 191
7.2.1 Heat loss from a buried pipeline 191
7.2.2 Line heater design 195
7.2.3 Two-phase heater transfer 198
7.3 De-pressurization 198
7.4 Melting a plug with heat 200
7.5 Buildings 202
7.6 Capital costs 202
Appendix 7A. Output from pipe heat loss program for the examples in the text 206
References 219
Chapter eight: Physical properties of hydrates 220
8.1 Molar mass 220
8.2 Density 221
8.3 Enthalpy of fusion 222
8.4 Heat capacity 224
8.5 Thermal conductivity 224
8.6 Mechanical properties 224
8.7 Volume of gas in hydrate 224
8.8 Ice versus hydrate 225
References 229
Chapter nine: Phase diagrams 230
9.1 Phase rule 230
9.2 Comments about phases 230
9.3 Single component systems 231
9.3.1 Water 233
9.4 Binary systems 233
9.4.1 Constructing T-x and P-x diagrams 236
9.4.2 Methane+water 236
9.4.3 Free-water 239
9.4.4 Carbon dioxide+water 239
9.4.5 Hydrogen sulfide+water 241
9.4.6 Propane+water 241
9.5 Phase behavior below 0°C 241
9.5.1 Methane+Water 241
9.6 Multicomponent systems 242
9.6.1 An acid gas mixture 243
9.6.2 A typical natural gas 244
References 247
Chapter ten: Water content of natural gas 248
10.1 Equilibrium with liquid water 248
10.1.1 Ideal model 249
10.1.2 McKetta-Wehe chart 250
10.1.3 Sharma-Campbell method 250
10.1.4 Bukacek 253
10.1.5 Ning et al. 254
10.1.6 Maddox correction 256
10.1.7 Robinson et al. charts 259
10.1.8 Wichert correction 260
10.1.9 AQUAlibrium 261
10.2 Equilibrium with solids 261
10.2.1 Ice 261
10.2.2 Hydrate 263
10.2.3 Methane 263
10.2.4 Gas gravity 264
10.2.5 Ethane 267
10.2.6 Propane 268
References 273
Chapter eleven: Additional topics 274
11.1 Joule-Thomson expansion 274
11.1.1 Theoretical treatment 275
11.1.2 Ideal gas 275
11.1.3 Real fluids 276
11.2 Hydrate formation in the reservoir during production 278
11.3 Flow in the well 278
11.4 Transportation 280
11.5 Natural occurrence of hydrates 281
11.5.1 Seabed 281
11.5.2 Natural gas formations 282
11.5.3 Outer space 283
References 285
Appendix: Programs on the Accompanying Web Site 288
Index 292
A 292
B 292
C 292
D 292
E 292
F 293
G 293
H 293
I 293
J 293
K 293
L 293
M 294
N 294
O 294
P 294
Q 295
R 295
S 295
T 295
U 295
V 295
W 295
X 295