The main objective of this study is to use microwaves to develop an energy efficient and economical separation method to demulsify stable crude oil and water emulsions. This separation method will be further enhanced by using reusable,
in situ materials to further destabilize the oil-water interface in the emulsions. The crude oil emulsions are formed by high shear mixing of process water and crude oil during pumping, desalting and transportation through wellbores and pipelines and are stabilized by emulsifying agents that form interfacial films at the oil-water interface. These surface-active species, such as asphaltenes, resins, solids, waxes, or commercially available chemical emulsifiers present in the crude, are responsible for the formation of stable emulsions. Tight crude oil emulsions, characterized by suspended droplets on the order of submicron to tens of microns, often cause serious problems to the wellbores and pipelines such as clogging, corrosion, and pump failures. The most common method widely used is the chemical demulsification method by addition of chemicals called demulsifiers. These chemicals neutralize the stabilizing effects of the emulsifiers that stabilize the emulsions. The surface active demulsifiers move to the oil/water interface and weaken or break the rigid films formed by the asphaltenes, resins, and waxes present in the emulsion. This enhances the coalescence of the dispersed water droplets. With increasing demand for nanomaterials in various fields, they have also gained interest in the petroleum industry. Graphene oxide (GO) has oxygen containing functional groups like epoxide, hydroxyl, carbonyl, and carboxyl groups. The presence of these oxygen-containing functional groups provides potential advantages for using GO in numerous applications. The polar oxygen functional groups in GO sheet make it strongly hydrophilic, which give GO good dispersibility in many solvents, particularly in water. It is hydrophilic and forms stable suspension in water and other solvents. Polyethylene glycol is a hydrophilic chemical demulsifier used for crude oil water separation.
Here we have prepared a hydrophilic nanohybrid structure (GO-PEG) using graphene oxide and polyethylene glycol (PEG). Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction were used to characterize the prepared GO-PEG structure. To simulate field conditions, we mixed two crude oils to prepare samples with American Petroleum Institute (API) gravities between 28.9° and 46.0°. These crudes were mixed with water to create emulsions containing between 20% and 80% water. This array of Water-in-Oil (W/O) and Oil-in-Water (O/W) emulsions with different densities and viscosities were mixed at varying shear rates. To study their individual effects on demulsification, GO, PEG, and GO-PEG were added to these emulsions at different concentrations of 0, 200, 500, and 1000 mg/L. A series of batch demulsification runs of these crude oil emulsions with GO, PEG, GO-PEG additives were done by exposure to microwaves under a well-defined set of parameters such as temperature, power, time, and salinity. To determine the efficiency of phase separation after treatment, final oil-phase water content was measured using Karl Fischer Titration. Change in droplet size of dispersed phase was analyzed using the optical microscopy images of the emulsions before and after treatment. Energy input analysis was performed from the Power-Time data obtained from each demulsification run. A separation efficiency model was developed based on the energy and mass balance study for the microwave demulsification method.
