Asphaltenes are typically defined by solubility as benzene soluble and pentane or heptane insoluble.The asphaltenes are believed to exist in the oil as a colloidal suspension,and are stabilized by resins adsorbed on their surface.The asphaltenes are normally in equilibrium at reservoir condition.As crude oil is produced this equilibrium may be disrupted by a number of factors.These includes pressure reductions,crude oil chemical composition changes,introduction of miscible gases and liquids,mixing with diluents and other oils,and during acid stimulation,hot oiling and other oilfield operations.The upset of the colloidal system may result in flocculation of asphaltenes.The deposition and precipitation of flocculated asphaltenes can severely reduce the permeability of the reservoir,cause formation damage and can also plug-up the wellbore and tubing.
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