New Strategy for Separation of Complex Water-in-Crude Oil Emulsions: From Bench to Large Scale Separation

During petroleum crude oil production there is incorporation of water in oil under the form of emulsions i.e. droplets of water in the oil phase. For economic and environmental purposes, these emulsions need to be "broken" to obtain anhydrous oil and pure water. As environmental regulations become more rigorous, it is of the outmost importance to improve oil-water separation technology in order to successfully process increasingly complex production fluids. That is why the project aims to improve the knowledge of water-oil separation processes and to develop new separation strategies by focusing on: 1. Improving the knowledge of the properties and composition of asphaltene (crude oil components) layers formed between oil and water. This layer is responsible for the separation problems. 2. Improving the oil-water separation by combining two different ways to break emulsions, namely the application of electrical fields (called electrocoalescence) and the injection of chemicals named demulsifiers. The project has Ugelstad Laboratory (NTNU) as host institution and is conducted in collaboration with University of Alberta, Canada, Swiss Federal Institute of Technology (ETH), Switzerland, and IFE in Kjeller,with a strong implication from industrial sponsors Anvendt Teknologi, Equinor, Nalco Champion, Nouryon, and Sulzer. The project has consisted in 5 different research activities. -The interactions between asphaltenes and model demulsifiers in bulk have been studied by a technique named Small-Angle Neutron Scattering. It was shown that model demulsifiers adsorb and then disrupt aggregates formed by asphaltenes in solution. -Second, Structure and properties of asphaltenes layers present on solid surface or between oil and water have been studied. The internal structure of asphaltene layers has been determined by neutron reflectometry. Then, the mechanical properties of asphaltene layers in presence of chemical demulsifiers have been determined by new techniques developed at ETH. Asphaltenes layers have a predominantly elastic character, responsible for the stability of oil emulsions, that is lost in presence of demulsifiers. -Thirdly, in order to gain knowledge about the effect of electrical fields on the interface, a new setup, and mathematical treatment to analyze data, was developed which allows the determination of the properties of the interface (interfacial tension) between a water droplet and oil in presence of an electric field. It was found that the transfer of crude oil components to the interface was improved in presence of electric field, compared with in absence and this was attributed to movements around the droplet in presence of electric field. Another set-up has also been developed to study the attraction between two droplets and their stability in presence of an electric field. The influence of chemical composition on attraction and stability was determined. -Fourthly, the electrocoalescence phenomenon was studied by a modelling method named Dissipative Particle Dynamics. This modelling technique allows to determine the effect of demulsifier on the films stabilizing water droplets. It was found that pores are formed in these films in presence of electric field. -Finally, the synergy between chemical demulsification and electrocoalescence to separate oil and water has been investigated at small scale (2 milliliters) and at high temperature at Ugelstad Laboratory. This study was made possible by developing a new set-up to recreate the electrical field applied in an industrial separator and new Nuclear Magnetic Resonance procedures which allow to follow-up oil-water separation. It was shown that, in absence of chemical demulsifiers, there is a critical electric field strength from which the separation is not improved even if the field strength is increased. When electrocoalescence is applied in combination with chemical demulsification, the separation is synergistically improved only at low electric field strength. Above a given field, the electric field dominates the separation efficiency. The data obtained from this technique have been compared with results obtained using other techniques designed to assess oil-water separation. It appears that, even if the different techniques provide similar trends, differences exist that seems to be related to the sample preparation methods (emulsification conditions). Since its start-up, research partners have reported the results and conclusions obtained in the project to the sponsors bi-annually. 9 scientific articles were published, and 2 are in the process to be submitted 1 Post-doctor and 2 master students have been educated in the program, as well as 2 PhD students. The results will allow a better description and simulation of oil-water separation process.

The results have allowed to develop new techniques and obtaining new knowledge on oil-water systems. We anticipate they will allow to improve separation strategies. Techniques: A new algorithm to measure the interfacial tension in presence of electric field. Improvement of a modeling technique, Dissipative Particle Dynamics, considering of electric field on the interface. The two improvements will allow new scientific investigations. New NMR techniques to follow up oil-water separation. They can be implemented by the Norwegian-company Anvendt Teknologi. Knowledges: Structure of the asphaltene layer at the interface, its rheological properties, and the influence of demulsifiers. Improved adsorption of asphaltenes onto droplets in presence of electric field. Determination of the attraction and the merger between two droplets when an electric field is applied. The range of improvement of separation by combining chemical demulsification and electrocoalescence is determined.

Water-in-oil emulsions (w/o) are formed during production, transport, and processing of petroleum crude oils and will impose a separation problem. The need to improve separation efficiency is accelerated by large water volumes, environmental constraints, subsea concept Development and low oil prices. The current project combines modelling and experimental activities in Norway and internationally. It aims at a better understanding of complex petroleum systems and to develop new separation strategy combining chemicals and electrocoalescers. The results will be integrated in separation modelling, instrument development and for new environmental-friendly chemicals. The project will have Ugelstad Laboratory as host institution but will be conducted in collaboration with several experts in separation and colloid chemisty: -Dr. Morad Amarzguioui and Erik Bjorklund, specialists in the field of electrostatic separation instumentation and large scale experiments, Wärtsilä Oil and Gas, Oslo. -Prof. Kenneth Knudsen, neutron techniques, IFE, Kjeller. -Dr. Geir Sørland, NMR method development, Anvendt Teknologi A/S, Trondheim. -Prof. Jan Vermant, interfacial phenomena, ETH Zurich, Switzerland. -Prof. Zhenghe Xu, colloid chemistry and emulsion technology, University of Alberta, Canada. -Prof. Roar Skartlien, Modelling, IFE/UL. This project is based on competence from two former programs: -Increased Energy Savings in Water/Oil Separation Through Advanced Fundamental Emulsion Paradigms, KPN Petromaks number 207538. -The Multiphase Flow Assurance Centre, SFI number 174974/I30 The activities of the proposal will be complimentary to and support for the research impact in the centre for research-based innovation (SFI) "Subsea Processing and Production (SUBPRO)" number 237893 in which Ugelstad Laboratory is one of the key partners.T