Chapoy, Antonin (2004) Phase behaviour in water/hydrocarbon mixtures involved in gas production systems. PhD thesis Génie des procédés, ENSMP.

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Abstract

Inside wells, natural gases frequently coexist with water. The gases are in equilibrium with the sub-adjacent aquifer. Many problems are associated with the presence of water during the production, transport and processing of natural gases. Accurate knowledge of the thermodynamic properties of the water/hydrocarbon and water-inhibitor/hydrocarbon equilibria near the hydrate forming conditions, at sub-sea pipeline conditions and during the transport is crucial for the petroleum industry.
An apparatus based on a static-analytic method combined with a dilutor apparatus to calibrate the gas chromatograph (GC) detectors with water was used to measure the water content of binary systems (i.e.: water -methane, ethane- water, nitrogen -water...) as well of a synthetic hydrocarbon gas mixture (i.e.: 94% methane, 4% ethane and 2% n-butane) with and without inhibitor. This same apparatus was also used generate data of methane, ethane, propane, n-butane and nitrogen solubility in water and also the solubilities of a synthetic mixture in water.
In-house software has been developed in order to fit and model the experimental data

Table of content

1.: INTRODUCTION AND INDUSTRIAL CONTEXT - 17
2 : STATE OF THE ART, BIBLIOGRAPHY REVIEW - 25
2.1. Properties and Characteristics of Water - 25
2.2. Gas Hydrates - 31
2.3. Experimental Data - 33
2.3.1. Water Content in the Gas Phase - 34
2.3.1.1. Water Content in the Gas Phase of Binary Systems - 34
2.3.1.2. Water Content in Natural Gas Systems - 37
2.3.2. Hydrocarbon Solubility in Water - 38
2.3.3. Hydrate Forming Conditions - 45
3 : THERMODYNAMIC MODELS FOR FLUID PHASE
EQUILIBRIUM CALCULATION - 53
3.1. Approaches for VLE Modelling - 53
3.1.1. Virial Equations - 54
3.1.2. Cubic Equations of State - 55
3.1.2.1. van der Waals Equation of State - 56
3.1.2.2. RK and RKS Equation of State - 57
3.1.2.3. Peng-Robinson Equation of State - 58
3.1.2.4. Three-Parameter Equation of State - 59
3.1.2.5. Temperature Dependence of Parameters - 63
3.1.2.6. EoS Extension for Mixture Application - 66
3.1.3. The g - F approach - 67
3.1.4. Activity Coefficient - 70
3.1.4.1. NRTL Model - 71
3.1.4.2. UNIQUAC Model - 72
3.1.4.3. UNIFAC and Modified UNIFAC - 73
3.2. Hydrate Phase Equilibria - 75
3.2.1. Empirical Determination - 75
3.2.2. van der Waals-Platteeuw Model (Parrish and Prausnitz Development) - 77
3.2.3. Modifications of the vdW-P Model - 80
3.2.3.1. Classical Modifications - 80
3.2.3.2. Chen and Guo Approach - 81
4 : EXPERIMENTAL STUDY - 87
4.1 Literature Survey of Experimental Techniques and Apparatus - 87
4.1.1 Synthetic Methods - 88
4.1.2 Analytical Methods - 90
4.1.3 Stripping Methods, Measurement of Activity Coefficient and Henry's Constant at Infinite Dilution - 91
4.1.4 Review of the Experimental Set-Ups for Determination of the Water Contents - 93
4.1.4.1 Direct Methods - 93
4.1.4.2 Indirect Methods - 95
4.1.5 Review of the Experimental Set-ups for Determination of Gas Solubilities - 100
4.2 Description of the Apparati for Measurement of the Water Content and Gas Solubilities - 100
4.2.1 The Experimental Set-ups for Determination of the Water Content and Gas
Solubilities - 101
4.2.1.1 Chromatograph - 104
4.2.1.2 Calibration of Measurement Devices and GC Detectors - 105
4.2.1.2.1 Calibration of Pressure Measurement Sensors - 105
4.2.1.2.2 Calibration of Temperature Measurement Devices - 107
4.2.1.3 Determination of the Composition in the Vapour Phase - 109
4.2.1.3.1 Calibration of the FID with Hydrocarbons (Vapour Phase) - 109
4.2.1.3.2 Calibration of the TCD with Water (Vapour Phase) - 111
4.2.1.3.2.1 Estimation of the Water Content - 111
4.2.1.3.2.2 Calibration Method -112
4.2.1.3.3 Optimization of the Calibration Conditions - 115
4.2.1.3.3.1 Optimization of the Chromatographic Conditions - 115
4.2.1.3.3.2 Calibration Results - 118
4.2.1.3.4 Experimental Procedure for determination of the vapour phase composition - 119
4.2.1.4 Determination of the Composition in the Aqueous Phase - 119
4.2.1.4.1 Calibration of the TCD with Water - 119
4.2.1.4.2 Calibration of the TCD and FID with the gases - 121
4.2.1.4.3 Experimental procedure for determination of the aqueous phase composition - 122
4.2.2 The Experimental Set-ups for Determination of Gas Solubilities -123
4.2.2.1 Apparatus based on the PVT techniques - 123
4.2.2.1.1 Principle - 123
4.1.2.2.2 Experimental Procedures - 124
4.2.2.2 Apparatus based on the static method (HW University) - 125
4.2.2.2.1 Principle - 125
4.2.2.2.2 Experimental Procedures - 126
5 : MODELLING AND RESULTS - 131
5.1 Pure Compound Vapour Pressure - 131
5.1.2 Temperature Dependence of the Attractive Parameter - 132
5.1.3 Comparison of the a-function abilities -133
5.2 Modelling by the F -F Approach - 139
5.3 Modelling by the g-F Approach- 141
6 : EXPERIMENTAL AND MODELLING RESULTS - 147
6.1 Water Content in Vapour Phase - 147
6.1.1 Methane-Water System - 147
6.1.2 Ethane-Water System - 56
6.1.3 Water Content in the Water with -Propane, -n-Butane, -Nitrogen, -CO2, -H2S Systems - 158
6.1.5 Mix1- Water-Methanol System - 167
6.1.6 Mix1- Water-Ethylene Glycol System - 170
6.1.7 Comments and Conclusions on Water Content Measurements - 171
6.2 Gas Solubilities in Water and Water-Inhibitor Solutions - 172
6.2.1 Gas Solubilities in Water - 172
6.2.1.2 Ethane - Water System - 175
6.2.1.3 Propane - Water System - 177
6.2.1.4 Mix1 - Water System - 179
6.2.1.5 Carbon Dioxide -Water System - 180
6.2.1.5.1 Data generated with the PVT apparatus - 180
6.2.1.5.1 Data generated with the Static analytic apparatus - 182
6.2.1.6 Hydrogen Sulphide-Water System - 185
6.2.1.7 Nitrogen -Water System - 188
6.2.2 Gas Solubilities in Water and Ethylene Glycol Solution - 190
7 : CORRELATIONS - 197
7.1 Water Content Models and Correlations - 198
7.1.1 Correlation and Charts - 198
7.1.1.1 Sweet and Dry Gas in Equilibrium with Liquid Water - 198
7.1.1.2 Acid Gas in Equilibrium with Liquid Water - 203
7.1.1.3 Gas in Equilibrium with Ice or Hydrate - 204
7.1.1.4 Comments - 205
7.1.2 Semi - Empirical Correlation - 206
7.1.2.1 Approach for Sweet and Dry Gas - 206
7.1.2.2 Gravity Correction Factor - 209
7.1.2.3 Acid and Sour Gas Correction Factor - 209
7.1.2.4 Salt Correction Factor - 210
7.1.3 Comments and discussions - 210
7.2 Gas Solubilities and Henry's Law Correlations - 212
8 : CONCLUSION AND PERSPECTIVES - 215
8.1 En français - 215
8.2 In English - 216
9 : REFERENCES - 219
APPENDIX A: PROPERTIES OF SELECTED PURE COMPOUNDS - 241
APPENDIX B: PUBLISHED PAPERS AND PROJECTS DONE DURING THE PHD - 242
APPENDIX C: THERMODYNAMIC RELATIONS FOR FUGACITY COEFFICIENT CALCULATIONS USING RK, RKS OR PR-EOS - 244
APPENDIX D: CALCULATION OF FUGACITY COEFFICIENT USING AN EOS AND THE NDD MIXING RULES - 247
APPENDIX E: BIPS FOR THE VPT EOS - 248
APPENDIX F: DATA USED FOR THE WATER CONTENT CORRELATION - 249
APPENDIX G: ARTIFICIAL NEURAL NETWORK FOR GAS HYDRATE PREDICTIONS - 253

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