| As the end of polymer flooding in the Daqing Oilfield major reservoirs, the displacement object gradually turned to oil reservoir with low permeability, large difference between layers, the injection pressure of the reservoir is generally high combined with the actual production condition. It mainly due to the polymer system or ASP system with certain reservoir fit is poorer, the injected solution mainly flow to the high permeability and good connectivity reservoir. Rely on the original layering injection process could not solve the above contradictions, so in order to improve the effect of the overall displacement of ASP flooding and lower the interlayer contradiction, we put forward the single pipe layering injection technology of ASP system about molecular weight and pressure adjusting. Based on the property contrast before and after through the nozzle of different types of ASP solution, combined with theoretical knowledge of these changes have made the corresponding explanation and analyzed the nozzle’s influence on ASP solution. We also optimized the structural parameters of the nozzle.First, this paper studied the influence of the nozzle on the microstructure of ASP solution. We observed the morphology of different ASP solution made by different molecular weight and concentration of polymer through scanning electron microscopy. Sample preparation freezing method is adopted to ensure the form of polymer molecules in the sample the same as the original state of hydration. The experimental results show that different types of the microstructure of ASP system were presented for uniform size, multilayer three-dimensional space network structure. The high concentration of ASP solution’s space network is more closely than the low concentration. A high molecular weight of ASP solution has a more thick network and strong rigidity. After through the nozzle all the solution’s space network appeared different degree of molecular chain fracture phenomenon, this suggests that part of the three-dimensional network structure after through the nozzle was cut off because of the shear and tensile action.Then in order to study whether the nozzle is influential in the polymer molecular weight or not, we used intrinsic viscosity method and the viscosity calculation method to measure the polymer molecular weight of the solution after through the nozzle. The results show that after through the nozzle, polymer molecular weight of the different types ASP solution has showed a trend of lower. A high molecular weight and concentration of ASP solution beard more intense shear than the low molecular weight and concentration ASP solution, so the viscosity loss is relatively larger than the low molecular weight and concentration ASP system, the error measured by viscosity calculation method of the molecular weight is bigger.Finally, we did fluid-solid coupling finite element analysis to the injector nozzle structure tools and parameters optimization on the tool’s structure. The results show that, the optimal structure parameters of nozzle is A4B3C2D2E3, the diffusion angle of L1=1mm, the diffusion angle of alpha=45°, the cylindrical section d=3mm diameter, the length of cylindrical section L2=2mm, the contraction section radius R=10 mm. Multistage series of nozzle can increase the viscosity loss without a significant increase in pressure loss and make the differential pressure greatly reduced at the same degree of shear.To sum up, due to the influence of shear and tensile of the nozzle, the original continuous space network structure of the ASP solution was destroyed and the polymer molecular weight of solution is reduced after through the nozzle, so the viscidity of the ASP solution degraded. This can further account for the working principle of the nozzle, and it has a practical guiding significance for the selection of the nozzle parameters in the field application. |
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