The micro encapsulated drag reducing agent, also known as MDRA, is made by encapsulating high concentration drag reducing polymer particles in a shell composed of some inert substances. The development of microcapsule drag reducer is a new trend of drag reducer. There are many methods to produce drag reducer, including static extrusion, centrifugal extrusion, vibrating nozzle, rotating disk, interface polymerization, multi-component agglomeration, suspension polymerization, etc. The formation process of static extrusion nozzle and microcapsule for producing microcapsule drag reducer is shown in Figure 1.

Using this device to produce microcapsule drag reducer is to add polymerization monomer, catalyst and shell materials from the central hole and outer ring sleeve respectively, and extrude from the lower end of the device at a certain speed to form microcapsule drag reducer particles. The extrusion speed is very important. When the extrusion speed is slow, the micro encapsulated particles will be regular in appearance and uniform in size. On the contrary, if the extrusion speed is fast, the micro encapsulated particles will adhere, resulting in the shape of the micro encapsulated particles is abnormal and the size is different. Keeping a certain frequency of vibration in the production process will help to control the particle size of microcapsules.

Because the monomer is polymerized in a small closed microcapsule, the reaction scale is very small for a single microcapsule, so the reaction conditions can be well controlled, especially the reaction heat can be emitted in time. If the monomer is σ - olefin, Ziegler Natta catalyst is usually used and added before the formation of microcapsules. Because the catalyst in Ziegler Natta system will fail rapidly when encountering oxygen, there is no oxygen in the reaction system. Some monomers can be polymerized by UV, but UV must be able to penetrate the microcapsule shell.

The outer shell of microcapsule is an important part of microcapsule drag reducer, and the reactants of outer shell material and inner core of microcapsule can not react with each other or be miscible. If the inner core of the microcapsule is a σ - olefin polymerization system, in order to avoid catalyst failure, there is no oxygen in the microcapsule shell, but a small amount of hydroxyl and carboxyl groups have little effect on the polymerization. The suitable shell materials are polybutene, polymethacrylate, polyethylene glycol, wax, stearic acid, etc. If the microcapsule shell itself is a polymer, its polymerization can be carried out in the process of producing microcapsule drag reducer, but it can not restrict other technical requirements of forming microcapsule system. In addition, the performance of the microcapsule shell is required to be stable in the process of transportation and storage, and its broken or dissolved residue has no effect on the physical and chemical properties of crude oil or petroleum products and the oil processing process. The microcapsule shell can be removed by dissolving in the injection medium or pipeline fluid, mechanical breaking, melting, photochemical breaking, biodegradation, combination and other methods.

Because the microcapsule drag reducer is stored and transported in the form of solid particles, the cost of transporting solvent, slurry or other carriers is saved. If solvent or other carriers (i.e. injection medium) are needed for injection into the oil pipeline, they can be purchased locally at a low price and prepared on site, instead of requiring complex post-processing procedures.