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Experimental and Simulation Study of Asphaltene Deposition in Porous Media

Khalili, Mohammad | 2009

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 39544 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Ghotbi, sirous; Kharrat, Reyaz
  7. Abstract:
  8. Asphaltene deposition on reservoir rocks occurs during natural depletion as well as miscible injection processes. It causes reduction of effective pore space and consequent impairment of the ability of oil to flow through reservoir. Therefore, deposition of asphaltene causes significant formation damage and wellbore plugging, requiring expensive and difficult cleanup procedures. Thus it is necessary to be able to consider the onset, amount of deposition and also consequent damage of permeability and porosity reduction due to various factors. The objective of current work is to conduct experimental and simulation study of asphaltene deposition dynamics in one of the Iranian reservoirs. In experimental tests, effect of pressure depletion, and also injection of CO2, Recycled gas and n-heptane on asphaltene deposition and permeability and effective porosity reduction, has been considered. Tests were performed using actual reservoir rock and fluid samples and under actual reservoir conditions of temperature and pressure. In simulation part, asphaltene deposition has been considered at the field scale and under natural depletion condition, and permeability and porosity reduction and their consequent effects on oil production have been investigated. Also sensitivity analysis of parameters affecting asphaltene deposition in reservoir has been done. The results showed during injection and especially at the beginning, pore throat plugging and to some extent surface deposition are the dominant mechanisms in permeability reduction. By continuing the injection and consequently increase of asphaltene deposition, re-entertainment of asphaltene particles can affect and cause to increase permeability. At first, permeability reduction at the beginning part of the core is greater than the rest, but in consequence, end core permeability decreases too. During co-injection of oil and normal heptane, the more increase in volume fraction of normal heptane, the more decrease in permeability. In addition, tests at reservoir condition of temperature and pressure showed that asphaltene deposition problem increases in natural depletion, co2 injection and recycled gas injection condition, respectively. Correlation between permeability reduction ratio and porosity reduction ratio showed that there is an exponential relationship between them, in which its exponent increases with the amount of asphaltene deposition. Simulation results showed that in reservoirs with natural depletion mechanism, the maximum amount of asphaltene deposition occurs near saturation pressure and also near production wells. The results of sensitivity analysis on asphaltene parameters showed that the role of asphaltene dynamic parameters on field performance forecast is important and crucial.
  9. Keywords:
  10. Permeability Reduction ; Natural Depletion ; Gas Injection ; Simulation ; Sensitivity Analysis ; Asphaltene Precipitation ; Solvent Injection

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