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Pore Scale Modeling of Fluid-Fluid Intercations During Low Salinity Waterflooding

Kamani, Ahmadreza | 2023

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 55961 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Ayatollahi, Shahab; Mahani, Hassan
  7. Abstract:

  8. Recent studies have shown that the injection of low-salinity water would enhance the oil recovery factor for both the core scale and the field test. The evidence obtained from laboratory studies showed that the control of salinity and the composition of injected water has successfully affected the oil release, hence enhancing the oil recovery efficiency. In this method, by changing the type and amount of dissolved ions in the injected water, the water/oil/rock interactions are altered. Based on this, extensive studies have been focused on the mechanisms for the trapped oil release at the pore scale. Several mechanisms have been proposed to explain this phenomenon, which can be divided into two categories. The first category is related to liquid/liquid interactions and the second one deals with solid/liquid interactions. One of the most recent proposed mechanisms related to liquid/liquid interactions is the change of surface viscoelasticity of water and oil because of low-saline water injection. Previous studies pointed to the fact that the oil and water interface is composed of high concentrations of natural surface active particles such as asphaltene. The accumulation of these polar molecules causes a special rheological response due to the fluid movement. In this case, the behavior of the oil-water interface cannot be described solely by isotropic surface tension. Therefore, it is necessary to change the boundary conditions of the stress on the contact surface and use specific structural models to describe the additional stresses on the interface. In this study for the first time, the effect of surface viscoelasticity on water/oil movement was modeled at the pore scale using computational fluid dynamics (CFD) simulation. The advantage of this method compared to laboratory tests is more flexibility to model different cases of fluid-fluid interactions at the pore scale that are difficult or impossible to be conducted in the lab. Besides, by utilizing this technique it is possible to conduct advanced sensitivity analysis to study the effects of different parameters in a wide range of changes. In this study, OpenFoam software as a computational fluid dynamics simulation was used to fulfill the goals of this research work. The results showed that the shear effects of surface viscoelasticity would reduce the mobility of the wetting phase (water) while increasing the mobility of the non-wetting phase (oil). This would hinder the movement of water on the rock surface in water-wet cases hence increasing the mobility of the oil phase. Considering the pressure, the surface viscoelasticity reduces the pressure of the mobile phase and increases the pressure of the immobile phase. These effects are opposed to the effects of interfacial tension in the throats, which results in the length of the non-wetting phase to be increased. Therefore, the continuity of the oil phase is maintained for a longer period of time, which leads to the release of more trapped oil from the porous rock. The preliminary results showed that by injecting low-salinity water; the shear elasticity of the oil-water interface increases. Therefore, in the next stage, the outcomes of this study were validated using the available laboratory results. After successful validation, it was shown that the amount of oil released out of the throat increased by 2.7%, and by modeling the single-pore system, the amount of trapped oil decreases by 5.9%. The shape of interfaces was closely monitored in this modeling study which showed that by considering the Dilatational elasticity, the curvature of the oil/water interface increases that prevents the trapping of the oil phase. Introducing the normal forces on the oil-water interface result in the continuity of the oil phase for a longer period of time. Quantitative results showed that the time required for water to neck the oil phase (oil trapping criterion) was increased by 1.31 in the modeling of the single pore system, by increasing the Dilatational elasticity. This phenomenon causes the oil to have more time to leave the pore, hence lower oil trapping results. Besides, in the validation stage using the results obtained from laboratory tests, the amount of output from the throat was increased by 3.5%, and in the modeling of the single-pore system, the oil volume trapped was decreased by 6.4 percent.
  9. Keywords:
  10. Computational Fluid Dynamics (CFD) ; Viscoelastic Surfactant (VES) ; Engineered/Low Salinity Water ; Modeling ; Pore-Scale Model ; Interfacial Rheology ; Fluid-Fluid Interaction

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