Abstract
Asphaltenes are complex molecular entities, which together with resins, aromatic hydrocarbons and saturates forms the crude oil. Asphaltenes and resins are in the thermodynamic equilibrium at static reservoir condition. However, asphaltene can precipitate due to changes in thermodynamic condition. Asphaltene deposition in production tubings has been an outstanding problem with wide economic impact on the oil industry. Meanwhile, the use of real-time tools to monitor depositions along the well is of great difficulty. In this work, the asphaltene precipitation region in a single phase flow wellbore is predicted for an oil well of the Iranian oil field. Then, asphaltene deposition thickness along the well is predicted for three time intervals. The simulation results indicated that asphaltene thickness exceeded more than 50% of tubing radius; therefore, a reduction in flow rate, an increase in pressure drop and tubing blockage are expected. Moreover, it is shown the deposits thickness along the wellbore has approximately a skew normal distribution shape, which could be the result of increases in velocity and excess pressure drop.
Highlights
Hydrocarbon crude oil is a complex mixture of hydrocarbon, hetero-atoms such as sulphur, oxygen and nitrogen as well as compounds containing metallic constituents vanadium, nickel, iron and copper
The asphaltene precipitation region in a single phase flow wellbore is predicted for an oil well of the Iranian oil field
It is shown the deposits thickness along the wellbore has approximately a skew normal distribution shape, which could be the result of increases in velocity and excess pressure drop
Summary
Hydrocarbon crude oil is a complex mixture of hydrocarbon, hetero-atoms such as sulphur, oxygen and nitrogen as well as compounds containing metallic constituents vanadium, nickel, iron and copper. Kharrat their solubility and polarity): 1) saturates, 2) aromatics, 3) resins and 4) asphaltenes; known as SARA fractions. The asphaltenes and resins have similar molecular structure but as a result of solubility based fractionation scheme employed, resins are less polar, less aromatic and have lower molar mass than asphaltenes [1]. Asphaltene, can form aggregates with molecular-weight distribution of 103 to 105 These aggregates are stabilized in solution by the resins and aromatics which act as peptizing agents. When this protective shield is removed by preferential dissolution of the resin into the fluid phase, asphaltene molecules start to flocculate and aggregate into large enough particles resulting in deposition [2]. Changes in temperature, pressure and chemical composition of crudes, combined with streaming-potential effects in well tubing, affect asphaltene stability [2]
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