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Pore-scale Simulation of Trapping Phenomena and Hysteresis Effect in Porous Media

Tabibnejad Azizi, Mehdi | 2023

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 55884 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Fatemi, Mobeen
  7. Abstract:
  8. So far, many studies have been carried out on the core-scale regarding the effects of hysteresis on the macro-scale properties of systems including fluids and porous rock, however, many issues related to the physics of the problem (especially regarding the way fluids are distributed and the trapping of the non-wetting phase) at the pore-scale need further investigation. In the process of multiphase fluid flow in porous media, hysteresis refers to the dependence of the results of the fluids’ displacements on the history of fluid saturation and the direction of saturation changes (increasing or decreasing). The first step to investigate the hysteresis effect is to determine the amount of fluid trapped in the previous displacement process. In this project, at the first part, the effect of hysteresis on the capillary pressure and relative permeability curves of the porous medium has been investigated through pore-scale simulations. For this purpose, cyclic injections of water and oil (imbibition-drainage cycles) have been simulated and the results have been analyzed to obtain the changes in the relative permeability and capillary pressure curves. Based on the results of the simulations, the amount of oil and water trapped in each injection was obtained, which was equal to 15 percent in the primary imbibition and 11percent in the secondary imbibition, which shows the irreversibility and hysteresis effect in the cyclic injections. In the second part of this research, in order to investigate the trapping phenomenon and the hysteresis effect more closely, the effect of low-salinity and high-salinity water injection in the porous medium with and without fractures has been discussed, and simulations have been carried out in co-current and counter-current displacement modes. Based on the obtained results, in all wettability alteration scenarios, co-current displacement has a higher recovery factor than counter-current displacement if all the conditions are equal. The counter-current displacement of oil by high-salinity water in a very water-wet system had a recovery factor equal to 30 percent, which was lower than the counter-current displacement by low-salinity water with contact angle changes of 130°-35° with a recovery factor of 44 percent. Also, among of counter-current displacements by low-salinity water (different degress of wettability alteration) , the case with contact angle changes of 130°-80° (where the minimum contact angle reached 80°), had the lowest efficiency (just 6% recovery factor). This result is expected since as the wettability of the matrix increases, the tendency of water to enter the matrix will increase. Among different investigated co-current displacements, the case with the contact angle changes of 130°-20°, had the highest efficiency with 56 percent recovery factor, and the lowest efficiency was related to the case with contact angle changes of 130°-80° with a recovery factor (15 %). Finally, in this research, the effects of secondary and tertiary injection of low-salinity water have been investigated. According to the results, tertiary injection of low-salinity water injection (after secondary injection of high-salinity water injection) does not have a great effect on oil production from fractured porous media. In these systems, injection of low-salinity water should be performed from the beginning. By injecting water in the oil-wet porous media, water tends to enter through larger pores, and when low-salinity water is injected, due to the wettability change towards water-wet, water will enter through smaller pores and displace the oil
  9. Keywords:
  10. Capillary Pressure ; Relative Permeability ; Wettability Alteration ; Hysteresis ; Trapping ; Low Salinity Water Flooding

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