# A Computational Study of Polymer Solutions Flow Regimes during Oil Recovery from a Fractured Model
## 4 Conclusions  
Polymer flooding with aqueous solutions of polyacrylamide is today one of the most effective and cheapest polymers used for reservoir flooding. In addition to its availability, other important advantages of polyacrylamide are their good solubility in water, due to which the viscosity of solutions quickly changes, the ability to easily filter in rock, and, also, environmental safety. Despite the fact that polymer flooding has been successfully used in field development for quite a long time, tasks related to optimizing the composition, increasing stability, reducing costs, and reducing the risks of the field-development process are still relevant. 1. A computational study of oil displacement from a fractured medium model obtained by digitizing the image of a fractured surface was carried out. To prepare a naturally cracked structure, an original approach was used, based on the evaporation of a suspension of nanodiamonds on a glass substrate. This made it possible to obtain a topology of the pore space close to the topology of real fractured cavern rocks. Calculations were performed for solutions of polyacrylamide polymer with different molecular weights. Experimentally determined properties of polymer solutions (viscosity, contact angle at the polymer-oil-rock, and interfacial tension) were used in the model. The computational study was employed to refine the technology for developing fractured structure models. The developed mathematical model was used to obtain new information about the flow of polymer solutions in a fractured medium;
2. The effect of polyacrylamide with a molecular weight of 20 million c.u. at 0.05 and 0.1% for oil displacement during polymer flooding of a fractured medium model. It is shown that using polymer solutions enhances the oil-recovery factor from the fractured medium from 0.45 (when displaced by water) to 0.74 when displaced by a polymer solution with a weight concentration of 0.05%. A further increase in the concentration to 0.1% leads to an enhancement of the oil-recovery factor to 0.85. Such a significant enhancement of the oil-recovery factor is due to the fact that the viscosity of polymer solutions increases significantly compared to that of water, as well as the fact that these solutions are non-Newtonian fluids (whose viscosity coefficient depends on the shear rate);
3. Investigation of the oil displacement from a fractured medium has been conducted for polymers with different molecular weights. Three polyacrylamide polymer solutions with a weight concentration of 0.1% were considered. Grades 2515, 2540, and 2020 polymer solutions with relative molecular weights of 10, 14, and 20 mln c.u. were  
Figure 16: The oil recovery (**a**) and the pressure drop (**b**) vs. weight concentration of polyacrylamide for different oil viscosities. considered in the computational study. For the considered 2515, 2020, and 2540 polymer solutions, the oil-recovery factors obtained during calculations were quite similar. The maximum magnitude of the oil-recovery factor for grade 2540 polymer was 0.88, which corresponded to the maximum values of the effective viscosity among the polymer solutions considered. The dependences of the pressure drop for polymers of different molecular weights were obtained. It was revealed that using polymer solutions leads to an increase in the pressure drop by 10 or more times. Thus, the greatest increase in the pressure drop was noted for the grade 2540 polymer solution, which exceeded that for water by 14 times. For grades 2515 and 2020 polymer solutions, the pressure drop was, respectively, 11.4 and 10.8 times greater than that for water;
4. The influence of oil viscosity on the oil-recovery factor and pressure drop during oil displacement using a polymer solution has been studied. Calculations were conducted for a polyacrylamide polymer solution with a molecular weight of 10 mln c.u. at a weight concentration of 0.1%. The largest increment of the oil-recovery factor, when using a polymer solution was observed for high-viscosity oil.