PHYSICOCHEMICAL CHARACTERIZATION OF ASPHALTENES A Thesis by ANDREAS ADI PRAKOSO Submitted to the Office of Graduate and Professional Studies of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Chair of Committee, Berna Hascakir Committee Members, Hadi Nasrabadi Yuefeng Sun Head of Department, A. Daniel Hill May 2016 Major Subject: Petroleum Engineering Copyright 2016 Andreas Adi Prakoso ABSTRACT This work proposes the study on physicochemical characterization of crude oils and their asphaltenes to understand the destabilization mechanism of asphaltenes. Knowledge on the molecular-scale interactions between components of crude oil is vital for the assessment of potential reserves and mitigation efforts of asphaltene-related problems. 11 heavy oil and bitumen samples from various regions of the world were subjected to characterization to attain universal yet simple correlations that are applicable under operating conditions. Comprehensive physicochemical analysis of the samples were performed through density and viscosity measurements of the crude oil, Saturates, Aromatics, Resins, and Asphaltenes (SARA) fractionation, Fourier Transform InfraRed (FTIR) spectroscopy analysis, elemental analysis, solubility profile assessment, and onset asphaltene precipitation (OAP) tests on the crude oil samples. Furthermore, two different types of asphaltenes were examined; n-pentane and n-heptane insolubles. Accordingly, density, zeta potential, and cluster size measurements, as well as high resolution microscopy imaging techniques, were conducted on these asphaltene samples to support the asphaltene stability and onset precipitation test results. The results have revealed that heteroatoms contained within the crude oils and asphaltenes play an important role in defining the physicochemical characteristics of crude oil. In particular, oxygen and metal (mostly V and Ni) functional groups were found to contribute significantly towards asphaltene stability and polarity. Additionally, this study has established that the presence of impurities in the saturates fraction causes it to have a destabilizing power towards ii asphaltenes. Thus, higher concentration of saturate fraction in the crude oil may pose higher risks of asphaltene-related issues. Moreover, it is highly recommendable that OAP experiments are conducted by using the crude oil’s own saturate fraction to achieve better accuracy and provide representative results of actual reservoir conditions. iii DEDICATION I dedicate this thesis to my parents, brothers, and friends who have given me their full support throughout my life. iv ACKNOWLEDGEMENTS I would like to thank Dr. Berna Hascakir for her continuous guidance and support throughout my research. Without her encouragements, I would not have been able to realize my full potential and reach such great heights with this study. I am also grateful to Dr. Hadi Nasrabadi and Dr. Yuefeng Sun for their willingness to serve as my committee members. A special thanks to Abhishek Punase who have helped me in countless occasions during my research. I would also like to specifically thank Kristina Klock for assisting me with some of the laboratory measurements. Moreover, I would like to express my deepest gratitude to all the members of the Heavy Oil, Oil shales, Oil sands, and Carbonate Analysis and Recovery Methods (HOCAM) research group for their help and support. I would like to extend my gratitude to Chevron, especially to Dr. Cesar Ovalles and Estrella Rogel, for their assistance in conducting the elemental analysis and solubility profile experiments. Furthermore, I am grateful to all the staff and faculty members of Texas A&M University who have shared their insights and also aided me in conducting lab measurements. Financial support from the Society of Petroleum Engineers (SPE) is also greatly appreciated. Lastly, I am thankful to all the support and motivation that my family and friends have given me throughout my life. v NOMENCLATURE AFM Atomic Force Microscopy ASTM American Society for Testing and Materials ATR Attenuated Total Reflectance DSC Differential Scanning Calorimetry EDS Energy Dispersive X-ray Spectroscopy ELSD Evaporative Light Scattering Detector ESI-MS ElectroSpray Ionization – Mass Spectrometry FTIR Fourier Transform InfraRed HPLC High Performance Liquid Chromatography nC5 n-pentane nC7 n-heptane NMR Nuclear Magnetic Resonance SARA Saturates, Aromatics, Resins, Asphaltenes SEM Scanning Electron Microscopy TDS Total Dissolved Solids TGA ThermoGravimetric Analysis wt% weight percent vi TABLE OF CONTENTS Page ABSTRACT .......................................................................................................................ii DEDICATION .................................................................................................................. iv ACKNOWLEDGEMENTS ............................................................................................... v NOMENCLATURE .......................................................................................................... vi TABLE OF CONTENTS .................................................................................................vii LIST OF FIGURES ........................................................................................................ viii LIST OF TABLES ............................................................................................................ xi CHAPTER I INTRODUCTION ........................................................................................ 1 CHAPTER II RESEARCH STATEMENT ....................................................................... 7 CHAPTER III EXPERIMENTAL PROCEDURES .......................................................... 8 3.1 Characterization of Crude Oils .......................................................................... 8 3.2 Characterization of Asphaltenes ...................................................................... 11 3.3 Onset Asphaltene Precipitation (OAP) Test .................................................... 14 CHAPTER IV EXPERIMENTAL RESULTS ................................................................ 15 4.1 Characterization of Crude Oil and Bitumen Samples ...................................... 15 4.2 Characterization of Asphaltenes ...................................................................... 31 4.3 Onset Asphaltene Precipitation Results ........................................................... 50 CHAPTER V CONCLUSIONS ....................................................................................... 61 REFERENCES ................................................................................................................. 63 APPENDIX ...................................................................................................................... 77 vii LIST OF FIGURES Page Figure 1: Correlation of heavy-to-light fractions of crude oil to API gravity and viscosity (Heavy: Asphaltenes and Resins; Light: Aromatics and Saturates) .. 17 Figure 2: FTIR spectra of 4 different types of crude oil. Other FTIR spectra can be found in the appendix section (Figure A-1). ..................................................... 20 Figure 3: Correlations of heteroatom content (Table 2) with physical properties of crude oil (Table 1). Blank circles represent outliers in the dataset. ............................ 24 Figure 4: Correlations of sulfur content (Table 2) with physical properties of crude oil (Table 1). Blank circles represent outliers in the dataset. ................................. 26 Figure 5: Correlations of metals content (Table 2) with physical properties of crude oil (Table 1). Blank circles represent outliers in the dataset. (Metals detected: Al, Ca, Cr, Cu, Fe, K, Mg, Mo, Na, Ni, Pb, Sn, Ti, V, and Zn) ............................. 27 Figure 6: Solubility profile of 4 different types of crude oil. The solubility profiles for other crude oil samples are listed in Figure A-3. .............................................. 28 Figure 7: Correlations of ∆PS parameter (Table 3) with SARA (Table 1) and elemental compositions (Table 2) of crude oil. Blank circles represent outliers in the dataset. .............................................................................................................. 30 Figure 8: Correlations of asphaltene density (Table 4) with physical properties of crude oil (Table 1). Blank circles represent outliers in the dataset. ............................ 33 Figure 9: FTIR spectra of original crude oil, n-pentane and n-heptane asphaltenes of sample EH2 ....................................................................................................... 34 Figure 10: Correlations of elemental composition with density of n-pentane asphaltenes. Blank circles represent outliers in the dataset. Asphaltene densities are reported in Table 4 and elemental analysis data are obtained from Table 5. In Figure 8D, metals include: Al, Ca, Cr, Cu, Fe, K, Mg, Mo, Na, Ni, Pb, Sn, Ti, V, and Zn elements. ........................................................... 38 viii Figure 11: Correlations of SARA fractions (Table 1) with zeta potential and cluster size of n-pentane asphaltenes (Table 6). Blank circles represent outliers in the dataset. .............................................................................................................. 41 Figure 12: Correlations of elemental composition of nC5 asphaltenes (Table 5) with zeta potential of