UNIVERSITY OF CALGARY Use of CO in Vapex, Experimental and Modeling Study 2 by Amin Badamchi Zadeh A THESIS SUBMITTED TO THE FACULTY OF GRADUATE STUDIES IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF CHEMICAL AND PETROLEUM ENGINEERING CALGARY, ALBERTA FEBRUARY, 2013 © AMIN BADAMCHI ZADEH 2013 Abstract Employing CO as the non-condensable gas in the Vapex process is an attractive option. 2 The high solubility and viscosity reduction potential of CO could provide improvement 2 to Vapex performance. Mixtures of CO and a hydrocarbon such as propane allow the 2 solvent to be tailored to different reservoir conditions. To select the optimum solvent mixtures, data on the phase behavior and physical properties of the oil-solvent system are required. The saturation pressure and solubility of propane in Athabasca bitumen as well as the liquid phase densities and viscosities, were measured at temperatures from 10 to 50°C. The solubility of pure carbon dioxide in Athabasca bitumen was measured and compared with the literature data. Two liquid phases were observed at carbon dioxide contents above approximately 12 wt%. A correlation based on Henry’s law was found to fit the saturation pressures at carbon dioxide contents below 12 wt%. The saturation pressure and solubility of carbon dioxide and propane in Athabasca bitumen, as well as the liquid phase densities and viscosities, were measured for three ternary mixtures at temperatures from 10 to 25°C. Two liquid phases (carbon dioxide rich and bitumen rich) were observed at 13 wt% carbon dioxide and 19 wt% propane. Only liquid and vapour-liquid regions were observed for the other two mixtures:13.5 wt% propane and 11.0 wt% carbon dioxide; 24.0 wt% propane and 6.2 wt% carbon dioxide. iii Vapex physical model experiments were conducted using a fixed composition of the CO 2 and propane binary mixture as the solvent. The objective of this work was to evaluate the performance of this solvent in recovering Athabasca bitumen. In-line measurements of the density and viscosity of the produced oil were used to gain further insight into the mechanisms involved in the process. An improved mathematical model was developed to predict the oil recovery performance of Vapex process. The compositional dependence of diffusion coefficient causes a strong non-linearity in the moving boundary diffusion equation of the Vapex mathematical model. Pseudo-concentration and pseudo-time terms were defined to resolve this non- linearity. The concentration profile ahead of solvent-bitumen interface was obtained analytically using the HIM “Heat Integral Method”. This results in a new correlation for the “average flow fraction of the heavy oil” in the flowing mixture, and drainage rate of heavy oil. The new correlation for drainage rate of heavy oil has the same square-root relationship to most of the key reservoir parameters as the previous theories except that its relationship to kinematic viscosity is altered by the concentration dependence of the diffusion coefficient. The new mathematical model was tested against our Vapex experimental results at a pseudo steady state condition to back calculate the solvent apparent mass diffusion coefficient at the vapor chamber interface and its power law functionality to solvent concentration. iv Acknowledgements I would like to take this opportunity to express my gratitude, regards and sincere thanks to my supervisors, Dr. Brij Maini and Dr. Harvey Yarranton for their continuous guidance and support throughout my study at the University of Calgary. It has been a great pleasure and privilege to work under their supervision toward completion of this research. I am very appreciative to Dr. Mehrotra and Dr. Svrcek for sharing their experience and expertise regarding to the solubility and property measurement of the solvent-bitumen system. Also I am very thankful to Dr. Marco Satyro for his technical inputs, helpful discussions, and great suggestions regarding the phase behaviour modeling. I also wish to thank my colleagues in the Improved Heavy Oil Science and Technology (IHOST) and Asphaltene & Emulsion Research (AER). The technical support from Paul Stanislav during Vapex experiments and from Elaine Baydak, Florian Schoeggl and Dr. Kamran Akbarzadeh during PVT experiments and property measurements is highly acknowledged. The phase behaviour software license from Computer Modeling Group (CMG) and Virtual Material Group (VMG) is highly appreciated. Financial support provided by AERI, Department of Chemical & Petroleum Engineering, and National Iranian Oil Company (NIOC) is greatly acknowledged. v Finally, I would like to appreciate my wonderful family for their understanding and patient and great emotional support throughout of this long study. vi Dedication To My family, My Mother, And memory of my late Father. vii Table of Contents Approval Page ..................................................................................................................... ii Abstract .............................................................................................................................. iii Acknowledgements ..............................................................................................................v Dedication ......................................................................................................................... vii Table of Contents ............................................................................................................. viii List of Tables ..................................................................................................................... xi List of Figures and Illustrations ....................................................................................... xiii List of Symbols, Abbreviations and Nomenclature ....................................................... xviii CHAPTER 1 : INTRODUCTION .......................................................................................1 1.1 Heavy Oil Resources .................................................................................................1 1.2 Vapex Process ............................................................................................................2 1.3 Research Objectives ...................................................................................................4 1.4. Thesis Outline ...........................................................................................................6 CHAPTER 2 : LITERATURE REVIEW ............................................................................8 2.1 Phase Behaviour of Bitumen and Solvent ...............................................................12 2.2 Vapor Solvent for Bitumen Extraction ....................................................................21 2.3 Viscosity of Heavy Oil and Solvent ........................................................................22 2.4 Solvent Mass Diffusion Coefficient in Heavy oil ....................................................29 2.5 Gravity and Capillary Forces Interplay in Vapex ....................................................30 2.6 Vapex Process Mathematical Model .......................................................................35 CHAPTER 3 : EXPERIMENTAL METHODS FOR PHASE BEHAVIOR AND PHYSICAL PROPERTIES ......................................................................................42 3.1 Materials ..................................................................................................................42 3.2 SARA Analysis ........................................................................................................43 3.2.1. Extraction and Purification of Asphaltenes ....................................................44 3.2.2. Fractionation of Maltenes ...............................................................................45 Clay and Gel Activation ....................................................................................45 Chromatographic Procedure ..............................................................................46 Solvent Removal ................................................................................................48 3.3 High Temperature Gas Chromatography (HTSD) - Simulated Distillation (SimDist). ...............................................................................................................51 3.4. Molecular Weight Measurements ..........................................................................53 3.4.1. Description and Operation of the Vapor Pressure Osmometer (VPO) ...........54 3.5. Density Measurement .............................................................................................60 3.5.1. SARA Fraction Densities ...............................................................................60 3.5.2. Athabasca Bitumen Density Measurement at Elevated Pressure and Temperature .....................................................................................................61 3.6. Athabasca Bitumen Viscosity Measurement ..........................................................63 3.7. Phase Behavior Measurements ...............................................................................65 viii The phase behaviour measurements are described for mixtures of bitumen and propane. Variations in the procedure for bitumen/carbon dioxide and bitumen/propane/carbon dioxide mixtures are described afterwards. .............65 3.7.1 Apparatus .........................................................................................................65 3.7.2 Methodology for Mixtures of Propane and Bitumen ......................................67 3.7.3 Methodology for Mixtures of Bitumen, Carbon Dioxide, and Propane ..........73 3.7.3.1. Solubility in Vapor-Liquid Region: ......................................................73 3.7.3.2. Phase Boundaries: .................................................................................75 3.7.4. Carbon dioxide, Propane, and Bitumen ..........................................................80 Cases 1 and 2 .....................................................................................................80 Case 3 82 CHAPTER 4 : PROPERTIES AND PHASE BEHAVIOR OF MIXTURES OF BITUMEN, PROPANE, AND CARBON DIOXIDE ..............................................84 4.1. Bitumen Properties .................................................................................................84 4.1.1 Characterization ...............................................................................................84 4.1.2 Density Data and Fitting ..................................................................................86 4.1.3 Viscosity Data and Fitting ...............................................................................89 4.2 Mixtures of Athabasca Bitumen and Propane ........................................................91 4.2.1. Saturation Pressure Correlation ......................................................................94 4.2.2. Density and Viscosity Modeling ....................................................................97 4.3 Mixtures of Athabasca Bitumen and Carbon Dioxide .........................................102 4.3.1. Saturation Pressure Correlation ....................................................................103 4.4. Mixtures of Bitumen, Propane, and Carbon Dioxide ...........................................108 4.4.1 Cases 1 and 2 .................................................................................................109 4.4.2 Case 3 ............................................................................................................114 4.5 SUMMARY ..........................................................................................................116 CHAPTER 5 : EQUATION OF STATE MODELING ...................................................119 5.1. Peng - Robinson Equation of State .......................................................................119 5.2. Athabasca Bitumen Characterization ....................................................................122 5.3. Model Tuning for Mixtures of Athabasca Bitumen and Propane .........................126 5.3.1 Saturation Pressure ........................................................................................126 5.3.2 Density ...........................................................................................................128 5.3.3Viscosity .........................................................................................................129 5.4. Model Tuning for Mixtures of Athabasca Bitumen and Carbon Dioxide ............133 5.6. Model Predictions for Athabasca bitumen/Carbon Dioxide/Propane Pseudo- Ternary Mixtures .................................................................................................135 5.6.1 Saturation Pressure ........................................................................................135 5.6.1.1 Propane and Carbon Dioxide Binary System .............................................135 5.6.1.2 Bitumen, Propane, and Carbon Dioxide Pseudo-Ternary ..........................136 5.6.2 Density ...........................................................................................................138 5.6.3 Viscosity ........................................................................................................140 7. Summary ..................................................................................................................141 CHAPTER 6 : VAPEX PHYSICAL MODEL AND EXPERIMENTAL METHODS ..142 6.1 Apparatus ...............................................................................................................142 ix 6.2. Experimental Procedure ........................................................................................146 6.2.1. Solvent Preparation ......................................................................................146 6.2.2. Physical Model Preparation ..........................................................................147 6.2.3. Vapex Test ....................................................................................................150 CHAPTER 7 : MATHEMATICAL MODEL OF THE VAPEX PROCESS ..................156 7.1 Introduction ...........................................................................................................156 7.2 Model Assumptions ...............................................................................................157 7.3 Diffusion Model .....................................................................................................159 7.3.1 Application of Fick’s Law .............................................................................159 7.3.2 Linearization of Equation 7-6. .......................................................................164 7.3.3 Heat-Integral-Method (HIM) Solution of Convective-Diffusive P.D.E. ......168 7.4. Fluid Flow and Movement of Interface ................................................................172 7.4.1 Fluid Flow Equation ......................................................................................172 7.4.2 Movement of the Interface ............................................................................174 7.4.3 Dimensionless Flow and Interface Movement ..............................................177 7.4.4. Bitumen Flow Rate Equation .......................................................................180 7.5. Model Solutions ....................................................................................................183 7.5.1. Pseudo Steady State Condition .....................................................................183 7.5.2. Transient Solution Procedure .......................................................................186 CHAPTER 8 : RESULTS OF VAPEX EXPERIMENTS ...............................................189 8.1 Experimental Results ............................................................................................190 8.4 Phase Behaviour and Compositional Path .............................................................204 8.5 Solvent Mass Diffusion Coefficient ......................................................................207 CHAPTER 9 : CONCLUSION AND RECOMMENDATION ......................................214 9.1 Summary and Conclusions ....................................................................................214 9.2 Observation ............................................................................................................217 9.3 Recommendations ..................................................................................................218 REFERENCES ................................................................................................................219 x