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Modeling of Asphaltene Deposition in Flow Lines Considering Pressure and Temperature Drop

Eyni, Leila | 2016

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 48800 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Ayatollahi, Shahabeddin; Assareh, Mehdi
  7. Abstract:
  8. Crude oil is made up of dozens of chemicals which based on their structural similarity, SARA test separate it into four categories: saturates, aromatics, resins and asphaltene. Asphaltenes are recognized as the largest, heaviest and the most polarizable fraction of the crude oil which are in thermodynamic equilibrium with oil at reservoir conditions. Each of the physical, chemical, electrical or mechanical disruption of this balance during production can result in instability and asphaltene precipitation may occur and eventually led to deposition in the reservoir, wells, pipelines, etc. Due to the fact that most changes in temperature and pressure will generated in the wells, thus observation of asphaltene deposition is more necessary in this part. Asphaltene deposition cause different problems such as the decrease of efficiency in EOR processes, blockage of the flow lines, production loss and so on; that’s why Asphaltene is known as an important factor affecting the oil industry, especially in the Iranian fields identified.Many studies have been done on the asphaltene deposition in porous media, but despite the universality of the asphaltene deposition in wells and flow lines, investigations in this case were not sufficient and due to the lack of adequate access to the sedimentation area in the well, they cannot answer all the complexities which are reported. Since diagnosis and determination of the possibility, time and amount of asphaltenes precipitation and deposition is the most important aspect of prevention and controlling the asphaltene problems at the start of the production of any oil reservoir containing asphaltenes, and according the importance of asphaltene deposition in well column with considering the temperature, pressure drop and hydrodynamic of wells, this issue has been studied comprehensively in this thesis, and precise simulator is developed for this purpose. The results in the form of a computer program that is capable of such calculations is presented. Despite uncertainties and even lack of data in some cases, the results of these studies can be obtained both qualitative and quantitative profile of asphaltene deposition in the flow lines inside the well.This study was performed in several stages, in the first step, the phase change from liquid to solid (i.e., asphaltene precipitation) reviewed which was entirely studied in thermodynamic modeling. There are several models in thermodynamic modeling, which in this thesis PC SAFT equation of state is used. Also it is extremely important to determine the pressure drop along the vertical well, because this pressure drop account for the energy of the well, so for this purpose and considering hydrodynamic flow Olga software is used. Finally in different pressure and temperature of each section of the well, stability of the asphaltene was defined and the solubility of asphaltene as a function of pressure and temperature as one of the inputs needed to get asphaltene deposition rate is calculated. With the passage of time and the effect of grain contacting and growth, asphaltene particle sizes will getting large which is studied in the second stage of kinetic modeling. In this section to obtain the rate of aggregation, the population balance module is used and the effect of size distribution is calculated. Finally to obtain the amount of asphaltene deposition with respect to required inputs calculated in the previous section, the equations of mass transfer between the fluid and the walls have been solved.The results of this thesis are: profile of solubility of asphaltene in the well column, profile of asphaltene solution in equilibrium conditions in the well column, asphaltene particle size distribution function, profile of asphaltene deposition in the well column with respect to the passing of time, the effect of distribution of different sizes on the asphaltene deposition
  9. Keywords:
  10. Deposition ; Aggregation Treatment ; Asphaltene Precipitation ; Population Balance ; Asphaltene ; Perturbed Chain From of the Statistical Associating Fluid Theory (PC-SAFT)State Equation

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