ttGOAosMSM Inge Harald Auflem Influence of Asphaltene Aggregation and Pressure on Crude Oil Emulsion Stability Influence of Asphaltene Aggregation and Pressure on Crude Oil Emulsion Stability by Inge Harald Auflem Thesis Submitted in Partial Fulfilment of the Requirements for the Degree of DOKTOR INGENI0R Department of Chemical Engineering Norwegian University of Science and Technology Trondheim, June 2002 Preface Preface This thesis, submitted in partial fulfilment of the requirements for the degree of dr.ing. at the Norwegian University of Science and Technology, consists of five articles, one patent and one book chapter. The thesis is based on work performed at Statoil Research Centre, the Institute for Surface Chemistry in Stockholm, and Chalmers University of Technology in Gothenburg in the period from August 1999 to June 2002. My supervisor introduced me to the field of surface and colloid chemistry in 1997, while studying physical chemistry as an undergraduate student at the University of Bergen. Little did I then know that the work would lead me into the petroleum industry, and a struggle with "the good and the bad asphaltenes". As an experimentalist, the work in the laboratory has, more often than not, provided results difficult to interpret. Nevertheless, the work has continued, and in-between the total failures, there has been some near successes, which have resulted in the thesis you are now paging through. During my time as a dr.ing. student I have had the fortune to participate in a project with the acronym FLUCHA II, which stands for Fluid Characterisation at elevated pressures and temperatures. The group has consisted of 3 dr.ing. students and 1 post doc, under the guidance of the enthusiastic and demanding Prof. Sjdblom. The work tasks of the group have covered a number of flow assurance related problems, i.e. asphaltene precipitation, emulsion formation and stabilisation, naphthenate formation, crude oil characterisation, etc. i Acknowledgements Acknowledgements First of all, I would like to express my sincere gratitude to my academic advisor Prof. Johan Sjoblom, for his years of guidance and invaluable encouragement, along with generous hosting when teambuilding throughout this research work. During my three years of work, I have enjoyed the opportunity of working with several fellow graduate students and postdoctoral associates, which have provided intellectual assistance and an enjoyable working environment. I am also grateful to all my co ­ authors, whom I have had the fruitful pleasure of collaborating with. I would also like to acknowledge the FLUCHA II program financed by the Research Council of Norway and the oil industry. Statoil ASA is especially thanked for providing office space and access to laboratory equipment. Finally, I wholeheartedly thank Helene and my parents for their love and support, without which this work would never have been completed. n Abstract Abstract Water-in-crude oil emulsions stabilised by various surface-active components are one of the major problems in relation to petroleum production. This thesis presents results from high-pressure separation experiments on "live" crude oil and model oil emulsions, as well as studies of interactions between various indigenous stabilising materials in crude oil. A high-pressure separation rig was used to study the influence of gas and gas bubbles on the separation of water-in-crude oil emulsions. The results were interpreted as a flotation effect from rising gas bubbles, which led to increased separation efficiency. The separation properties of a "live" crude oil were compared to crude oil samples recombined with various gases. The results showed that water-in-oil emulsions produced from the "live" crude oil samples, generally separated faster and more complete, than emulsions based on recombined samples of the same crude oil. Adsorption of asphaltenes and resins onto a hydrophilic surface from solutions with varying aromatic/aliphatic character was investigated by a quarts crystal microbalance. The results showed that asphaltenes adsorbed to a larger degree than the resins. The resins were unable to desorb pre-adsorbed asphaltenes from the surface, and neither did they adsorb onto the asphaltene-coated surface. In solutions of both of resins and asphaltenes the two constituents associated in bulk liquid and adsorbed to the surface in the form of mixed aggregates. Near infrared spectroscopy and pulsed field gradient spin echo nuclear magnetic resonance were used to study asphaltene aggregation and the influence of various amphiphiles on the asphaltene aggregate size. The results showed interactions between the asphaltenes and various chemicals, which were proposed to be due to acid-base interactions. Among the chemicals used were various naphthenic acids. Synthesised monodisperse acids gave a reduction of size of the asphaltene aggregates, whereas polydisperse naphthenic acids seemed to affect the state of the asphaltenes only to a minor extent. The effect of the naphthenic acids on the asphaltenes appeared however, to depend on the asphaltene type. Other amphiphiles such as amines and alcohols, showed a varying effect on the dispersion of the asphaltenes into smaller aggregates. Furthermore, measurements of diffusion coefficients upon increased concentration of asphaltenes, implied that the asphaltenes began to self-associate at concentrations above 0.1 wt-% in toluene-dg. Table of Content Table of Content Preface ..................................................................................................................................... i Acknowledgements ................................................................................................................... II Abstract ................................................................................................................................... ill Table of Content ..................................................................................................................... iv List of Publications.................................................................................................................... v Complimentary work.................................................................................................vi 1 Introduction .............................................................................................................. 1 2 Theory ........................................................................................................................ 3 2.1 Crude Oil Composition.................................................................................3 2.2 Asphaltene Chemistry.................................................................................. 4 2.3 Emulsions and Emulsion Stability............................................................... 9 2.4 Stabilisation of Water-in-Crude Oil Emulsions......................................... 10 2.5 Destabilisation of Crude Oil Emulsions..................................................... 12 3 Methodology and Theory ....................................... 16 3.1 High-pressure High Temperature Separation Rig (HPHT-rig).............. 16 3.2 Quartz Crystal Microbalance (QCM)...........................................................18 3.3 Near Infrared Spectroscopy (NIR)............................................................20 3.4 Nuclear Magnetic Resonance (NMR)......................................................... 22 4 Main Results .............................................................................................................26 4.1 Paper 1........................................................................................................ 26 4.2 Paper II.......................................................................................................28 4.3 Paper III......................................................................................................33 4.4 Paper IV......................................................................................................36 4.5 Paper V.......................................................................................................37 4.6 Paper VI......................................................................................................40 5 Summary and Conclusions ......................................................................................44 References ............................................................................................................................. 46 Papers I-VII IV List of Publications List of Publications 1. Auflem, I.H., Kallevik, H., Westvik, A. and Sjoblom, J., Influence of Pressure and Solvency on the Separation of Water-in-Oil Emulsions from the North Sea. Journal of Petroleum Science and Engineering, 2001. 31(1): p. 1-12. 2. Kallevik, H., Sjoblom, J., Westvik, A., Auflem, I.H., Process for separation of water and oil in a separator by breaking water-in-oil emulsions, P 4202-1, PCT- application, 23. February 2002 3. Auflem, I.H., Westvik, A. and Sjoblom, J., Destabilisation of water-in-oil emulsions based on recombined oil samples at various pressures. Journal of Dispersion Science and Technology, Submitted 4. Ekholm, P., Blomberg, E., Claesson, P., Auflem, I.H., Sjoblom, J. and Kornfeldt, A., A Quartz Crystal Microbalance Study of the Adsorption of Asphaltenes and Resins onto a Hydrophilic Surface. Journal of Colloid and Interface Science, 2002. 247(2): p. 342-350 5. Auflem, I.H., Havre, T.E. and Sjoblom,