Accurate modeling of the asphaltenes precipitation from asphaltenic crude oil is essential in order to possible preventive and curative measures for the potential problem of asphaltene deposition occurring during oil production, transport and refining operations.
Available thermodynamics model are very complicated and requires several different adjustable parameters for modeling asphaltene precipitation that may not be accurate in prediction of some operational range.
In this paper the simple method base on scale equation has been developed for prediction of asphaltene precipitation modeling from live oil. Extensive experimental results were applied over a wide range of temperature and pressure on the different Iranian oil fields.
The original scale equation has been presented for modeling of asphaltene precipitation due to increasing the normal alkane concentration to the dead oil. In the live oil the same analogy has been applied with this difference that for the live oil in the isothermal condition, change in the pressure is the major factor that causes the asphaltene precipitation. Therefore, two different models have been presented for upper and lower bubble point to cover all range of operational condition.
The models are adequate to represent a wide range of the experimental results. The predictions of the suggested modified scaling equations for asphaltene deposition from live oil are compared with present results and the data which are reported by other investigators for live oil from other reservoirs. Good agreements are observed which confirm the suitability of the models.
Crude oil is considered as a colloidal mixture consisting fractions of saturated hydrocarbons, aromatics, resins and asphaltenes components 1. Asphaltene is viewed as the most polar and highest molecular weight fraction of the crude oil. The chemical structure of asphaltene has been the subject of many studies.2,3 These investigations reveal that asphaltenes are stabilized in oil by the resin molecules which act as peptizing agent for emulsifying asphaltene particles. Colloidal asphaltenes may be naturally or artificially precipitated from oil if the resin molecules are removed from the surface of asphaltene panicles. Resins are normally classified as the fraction of crude oil which is soluble in normal alkane solvents such as normal heptane and normal hexane while asphaltenes are soluble in aromatic solvents such as benzene, toluene and xylene.4 Asphaltenes appearance are brown and chemically consisting a mixture of polar ring aromatic and naphthenic molecules which contain heteroatoms of nitrogen, sulfur and oxygen, flocculated by normal alkanes including those with small carbon number such as propane 5,6. The degree of resins removal from the surface of asphaltene particles depends strongly on the carbon number of the normal alkane solvents and increases with increasing carbon number 7,8. Asphaltenes deposition can also be enhanced by any chemical, mechanical or electrical processes which are able to depeptize colloidal asphaltene particles and thus lead to flocculation and precipitation of deposit 9.
Asphaltene deposition is considered as a major unresolved problem in oil industry which may occur during primary oil production and subsequent enhanced oil recovery methods.
