Analytical Characterization Methods for Crude Oil and Related Products

Ashutosh K. Shukla, PhD, is Associate Professor of Physics at Ewing Christian College, Allahabad, India. He is a Member of the International EPR Society (IES), Web member of the International Society of Magnetic Resonance (ISMAR), and matching member of the American Physical Society (APS).

List of Contributors xiii

Preface xvii

1 Rheological Characterization of Crude Oil and Related Products 1
Flávio H. Marchesini

1.1 Introduction 1

1.2 Sample Preparation for Rheological Characterization 2

1.2.1 Ensuring the Chemical Stability 2

1.2.2 Choosing the Rheometer Geometry 3

1.2.3 Erasing theThermal Memory 4

1.2.4 Performing the Cooling Process 4

1.3 Rheological Tests 5

1.4 Potential Sources of Errors 9

References 10

2 Optical Interrogation of Petroleum Asphaltenes: Myths and Reality 13
Igor N. Evdokimov

2.1 Introduction 13

2.1.1 What are Asphaltenes? 13

2.1.2 The Reasons for Intensive Asphaltene Research 14

2.1.3 No Controversy about the Elemental Composition of Asphaltenes 15

2.1.4 Continuing Debates on the Size and the Structure of Asphaltene Molecules and Aggregates 15

2.1.5 Conflicting Paradigms based on Similar Analytical Techniques: Apparent Significance of “Human Factors” 18

2.2 Mythical “Characteristic Signatures” of Asphaltenes in Optical AnalyticalMethods 19

2.2.1 Nonexistent “Resonance UV Absorption” of Asphaltenes 19

2.2.2 Mythical “CharacteristicMonomer Peaks” in Fluorescence Emission Studies 23

2.3 Misconceptions about the Properties of UV/Vis Absorption Spectra of Asphaltenes 29

2.3.1 The Myth about the Absence of Asphaltene Aggregation Effects in Optical Absorption Studies 30

2.3.2 The Myth about the “Urbach Tail” in Optical Absorption Spectra of Asphaltenes and Crude Oils 34

2.3.2.1 Tauc Range 35

2.3.2.2 Urbach Range 35

2.3.2.3 Low Absorption (Defects) Range 35

2.3.3 In the UV/Vis Spectral Range Asphaltenes Apparently Act not as Absorbers, but as Scatterers 38

2.4 Current State of Knowledge about Asphaltene Monomers and Primary Asphaltene Aggregates 42

2.4.1 Some Requirements for Preparation of Dilute Asphaltene Solutions 44

2.4.2 Multiple States/Phases of Primary Asphaltene Aggregates Revealed by Optical Absorption Measurements 46

2.4.3 Multiple States/Phases of Primary Asphaltene Aggregates Revealed by Refractive Index Measurements 47

2.4.3.1 Mean Refractive Index at Concentrations below CNAC 50

2.4.3.2 Standard Deviation of Refractive Index at Concentrations below CNAC 50

2.4.4 Conditions for Observation of Asphaltene Monomers and Evolution of Primary Asphaltene Aggregates Revealed by Fluorescence Measurements 53

2.4.4.1 Studies of Steady-State Fluorescence Emission 53

2.4.4.2 Studies of Time-Resolved Fluorescence Emission 55

2.4.5 Evolution of Primary Asphaltene Aggregates Revealed by Mass Spectrometry 56

2.4.6 “Optical Interrogation” Reveals that Primary Asphaltene Aggregates are Porous and Entrap/Occlude Molecules of Metalloporphyrins and other Compounds 58

2.4.7 Apparent Absence of “Consecutive Aggregation” in Asphaltene Experiments: Revised Description of the Observed Non-monotonic Concentration Effects in Dilute Asphaltene Solutions 62

References 65

3 ESR Characterization of Organic Free Radicals in Crude Oil and By-Products 77
Marilene Turini Piccinato, Carmen Luisa Barbosa Guedes and Eduardo Di Mauro

3.1 Introduction 77

3.2 Organic-Free Radicals in Crude Oil 77

3.3 ESR of Crude Oil 78

3.4 By-Product Oil by ESR 85

3.5 ESR and Calculations on the Electronic Structure of Free Radicals in Oil By-Products 93

References 96

4 High-Field, Pulsed, and Double Resonance Studies of Crude Oils and their Derivatives 101
Marat Gafurov,M. Volodin, T. Biktagirov, G. Mamin and S. B. Orlinskii

4.1 Introduction 101

4.2 EPR: Basic Principles and Magnetic Interactions 103

4.3 EPR Pulse Sequences 109

4.4 Application Examples 112

4.4.1 W-Band, Relaxation Studies of VO2+ and FR in Asphaltenes Fractions 112

4.4.2 ENDOR of VO2+ in Crude Oil Samples 116

4.5 Conclusion 121

Acknowledgments 121

References 121

5 NMR Spectroscopic Analysis in Characterization of Crude Oil and Related Products 125
Siavash Iravani

5.1 Introduction 125

5.2 1HNMR and 13C NMR Spectroscopy Analysis Methods 126

5.3 NMR Techniques 127

5.4 Application of NMR Analysis in Characterization of Crude Oil and Related Products 129

5.5 Asphaltene Characterization using NMR Techniques 134

5.6 Conclusions 137

References 137

6 NMR Spectroscopy in Bitumen Characterization 141
Catarina Varanda, Inês Portugal, Jorge Ribeiro, Carlos M. Silva and Artur M. S. Silva

6.1 Introduction 141

6.2 1H and 13C NMR Spectroscopy 143

6.3 Phosphorus-31 NMR Spectroscopy 152

6.4 NMR Imaging and Solid-State NMR 154

6.4.1 Solid-State NMR 154

6.4.2 NMR Imaging 155

6.5 Conclusion 156

References 157

7 Applications of Low Field Magnetic Resonance in Viscous Crude Oil/Water Property Determination 163
Jonathan L. Bryan and Apostolos Kantzas

7.1 Introduction 163

7.2 Background for NMR Measurements 165

7.2.1 Interpretation of NMR Relaxation Rates 167

7.2.2 Interpretation of NMR Amplitudes 171

7.3 Fluid Content in Oil/Water Systems 175

7.4 Oil Viscosity from NMR 181

7.4.1 Viscosity Predictions in High Viscosity Bitumen 187

7.4.2 Viscosity Predictions in Oilfield Emulsions 189

7.5 Fluid Saturations and Viscosity in Porous Media 192

7.5.1 Prediction of Saturations and Viscosity from T2 relaxation distributions 193

7.5.2 Prediction of Saturations from T1–T2 Relaxation Distributions 200

7.6 NMR in Oil-Solvent Systems 206

7.6.1 Predictions of Solvent Content in Oil–Liquid Solvent Systems 207

7.6.2 Predictions of Non-Equilibrium Viscosity in Oil–Vapor Solvent Systems 213

7.7 Summary of NMR and Fluid Property Measurements 215

Acknowledgments 216

References 217

8 Application of Near-Infrared Spectroscopy to the Characterization of Petroleum 221
Patricia Araujo Pantoja, Juan López-Gejo, Claudio Augusto Oller do Nascimento and Galo Antonio Carrillo Le Roux

8.1 Introduction 221

8.2 Sample Handling and Preparation 222

8.3 Near-Infrared Spectroscopy 223

8.3.1 Near-Infrared in Refineries 227

8.4 Chemometrics 228

8.4.1 Pretreatment 228

8.4.1.1 Smoothing 228

8.4.1.2 Multiplicative Scatter Correction 228

8.4.1.3 Mean Centering 229

8.4.1.4 Derivation 230

8.4.2 Calibration Model 230

8.4.2.1 Principal Component Analysis (PCA) 231

8.4.2.2 Partial Least Squares Regression 232

8.4.2.3 Artificial Neural Networks 234

8.4.3 Validation 234

8.4.4 Other Methods 235

8.5 Commercial NIR Equipment and Industrial Applications 236

8.5.1 Industrial Applications 236

8.5.1.1 Pipeline Product Analysis and Identification 238

8.5.1.2 Crude Distillation Optimization 238

8.5.1.3 Product Blending 238

8.5.1.4 Ethanol Fermentation 238

8.5.1.5 Conjugated Diolefins in Pygas 238

8.5.1.6 Regulatory Fuel Screening 238

8.6 Conclusions 239

References 239

9 Raman and Infrared Spectroscopy of Crude Oil and its Constituents 245
Johannes Kiefer and Stella Corsetti

9.1 Introduction 245

9.2 Fundamentals of Raman and Infrared Spectroscopy 246

9.3 Infrared Spectroscopy 249

9.4 Raman Spectroscopy 251

9.5 Evaluation of Vibrational Spectra 257

9.6 Applications 261

9.7 Conclusion 266

References 267

Index 271