Pore-Scale Investigation of Polymer Enhanced Low Salinity Water flooding EOR

Posht Panah, Mohammad Reza | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 53911 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Mahani, Hassan; Rostami, Behzad
  7. Abstract:
  8. Low salinity water flooding (LSWF) is a relatively new EOR method in which low salinity or modified ionic composition water is injected into the reservoir to alter its wettability toward a more water-wettable state to accelerate oil recovery. Ease of field deployment and relatively low cost, as well as laboratory results confirming the positive effect of this method in improving the oil recovery factor, have made this technique attractive in the oil industry.Despite the many advantages of this method, overcoming the mixing between low and high salinity water which occurs due to a high mobility ratio between these two fluids is essential because it negatively affects the efficiency of LSWF. This study addresses the problem by using polymer augmented low-salinity brine to suppress mixing. For this purpose, a systematic series of visual, micromodel experiments were carried out. The micromodels were first saturated with high salinity brine, and then low salinity water was injected into the micromodels. Partially hydrolyzed polymer (HPAM) was used in the experiments. To investigate the impact of polymer concentration on pore-scale mixing, the polymer concentration varied between 0 to 750 ppm. The breakthrough curve for each experiment was obtained using a high-resolution digital camera mounted at a point near the outlet of the model to monitor the displacement of high salinity water by injected low salinity brine. The breakthrough curves were interpreted using advection-dispersion analytical model to infer the dispersion coefficient. In addition to the experimental work, conceptual computational fluid dynamics (CFD) simulations were performed to provide further insight into the experimental observations and also to verify these results. The pore-scale results show that using different concentrations of polymer reduces the mixing between high and low salinity brines by 2 to even more than 3 times, and sharpens the breakthrough curve. Another important point of using polymer is to control the phenomenon of viscous fingering. The addition of polymer, increased the viscosity of the injected brine, reduced the mobility ratio and delayed the breakthrough of the low salinity fluid between 0.08 to 0.2 pore volume injected (PVI) in homogeneous micromodels, and between 0.03 to 0.9 in the heterogeneous model depending on the polymer concentration. This helps improve the performance of low salinity water by increasing the microscopic displacement of high salinity water. The results of this study show that the concentration of 250 ppm polymer has a smaller effect in reducing the mixing zone length than the concentration of 500 ppm. On the other hand, in most of the experiments, it was observed that increasing the polymer concentration to 750 ppm had little effect on the results compared to the concentration of 500 ppm. Therefore, an optimal concentration can be determined. Another important aspect addressed in this study was the effect of injection rate on the variations of mixing zone length. The results show that increasing the injection rate would aggravate the mixing between LS and HS brines as a result of an increase in fluid velocity. However, adding polymer at higher rates also reduced mixing and improved the performance of low salinity water
  9. Keywords:
  10. Low Salinity Water Flooding ; Micromodel ; Polymers ; Molecular Dynamic Simulation ; Enhanced Oil Recovery ; Computational Fluid Dynamics (CFD) ; Mixing between Low Salinity and High Salinity ; Viscous Fingering Phenomenon

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