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Mechanistic Studies of Improved Oil Recovery under Forced Gravity Drainage GAGD Process

Rostami, Behzad | 2009

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 39352 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Kharrat, Riyaz; Ghotbi, Cyrus; Pooladi Darvish, Mehran
  7. Abstract:
  8. Gas-oil displacement, when stabilized by gravity forces leads to high displacement efficiency, as manifested in high recovery factor associated with gas-cap drive and gravity drainage. The main objective of this research is improved understanding of drainage behavior and changes in flow properties when the importance of viscous, gravity and capillary forces varies. The influence of interplaying between controlling forces on relative permeabilities is also studied. Another objective of this work is to study effect of wettability on recovery under forced gravity drainage. To study drainage behavior under various dominant driving/resistive forces, a number of forced gravity drainage experiments have been conducted in low pressure visual and physical models and high pressure core holder using a wide range of the physical and operational parameters, where the type, length, permeability, and wettability of the porous media as well as oil viscosity and injection rate were varied. The experimental results indicated that oil recovery (at a constant pore-volume of gas injected) is adversely affected by (i) increasing rate (ii) increasing viscosity and (iii) decreasing permeability. Analytical and numerical analysis of the results of this study showed that the negative effect of displacement rate on oil recovery can be related to oil relative permeability. For experiments conducted in unconsolidated media, the influence of increasing rate on oil relative permeability is found to be more when the capillary force is significant. The experiments with oil-wet and water-wet porous media showed that the negative effect of increasing rate could be consistently observed in both systems. In oil-wet systems, the degree of worsening of oil recovery with increasing rate was found to be more than that in water-wet systems. To better understand the fluid dynamics in the GAGD process, the dimensional analysis was employed. Analyses of the experimental results using dimensionless numbers indicate that each number alone is insufficient to obtain a satisfactory correlation with recovery, therefore a combined dimensionless group is proposed. Recoveries from of all experiments conducted in this study show a very good correlation with the proposed group
  9. Keywords:
  10. Gas-Oil Gravity Drainage ; Wetting ; Relative Permeability ; Enhanced Oil Recovery ; Gas Injection ; Dimensionless Numbers

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