Study on Aggregation Morphology and Resistance Reducing Properties of Drag Reducing Agents

In order to clarify the micro control mechanism of the macro drag reduction performance of drag reducing agents, a large number of micro characterization of the aggregate structure formed by different types of polymer drag reducing agents were carried out by environmental scanning electron microscope. Combined with the test of the drag reduction performance of the system, the micro mechanism of the effect of concentration on the drag reduction performance of different drag reducing agents systems was revealed from the level of polymer molecular aggregation structure. It is found that most of the aggregation forms of slick water fracturing fluid drag reducing agents are net like network structures surrounded by polymer skeleton structures, but the network structures formed by different types of drag reducing agents are different. Among them, emulsion and suspension type drag reducing agents have the most complete network structures, while powder type drag reducing agents have uneven distribution of aggregated network structures and low network strength due to slow dissolution speed. At low concentration, the average mesh wall thickness of the network structure formed by the three drag reducing agents is about 0.1 ~ 0.3 μm. With the increase of the concentration of drag reducing agents, the mesh shape of the system gradually changes from irregular to polygonal. Some drag reducing agents can form a circular network support structure with high strength and good stability. The mesh size decreases and the mesh wall thickness increases. When the concentration of drag reducing agents increases to 0.05%, the mesh wall thickness can reach 0.3 ~ 0.9 μm. The strength of network structure has been significantly improved. The aggregation structure characteristics of drag reducing agents will have an important impact on the drag reduction performance of the system. The over dense or sparse mesh of polymer network is not conducive to the exertion of the drag reduction performance of the system. Only the network structure with appropriate size will deform properly under the action of shear, effectively store the energy of solution turbulence, significantly reduce the energy dissipation in the flow process, and finally achieve a good drag reduction effect.