ABSTRACT
Asphaltenes precipitate and form deposits in reservoirs, wellbores, flowlines, separators and other equipment. The implementation of enhanced oil recovery operations, based on miscible injection of gases, may lead to asphaltene precipitation and deposition due to lower solubility in lower density crude oils. The asphaltenes content of reservoir fluids varies greatly. Precipitation and deposition of asphaltenes is most prevalent from light crude oils and least prevalent from heavy crude oils. Asphaltenes are a poorly defined group of high molecular weight, highly aromatic, polar compounds found in crude oils. The presence of asphaltenes stabilizes oil-water emulsions and oil-gas foams, making the separation of oil, gas and water difficult, affecting important sales and environmental specifications. Several fields of study are required to make progress in understanding asphaltenes: organic chemistry, colloidal/emulsion sciences, thermodynamics and phase behaviour. Asphaltenes are insoluble in paraffinic hydrocarbons, but soluble in aromatic hydrocarbons.
