| The natural gas was growing in demand because of the needing on the economic sustainable development and the calling on the clean energy. As the green high efficiency energy, natural gas had become the optimum selection to improve environment and promote economic sustainable development for all over the world. It was also a main way to improve the energy structure and seek the coal replacement energy of China. At present, the popularization rate and the consumption of natural gas had became the mark of the economic and social development level to evaluate one country, one zone, or one city.Pipeline was one of five major forms of transportation in the world. At present, almost all of natural gas produced in the world were transported by pipeline. The long-distance, big-diameter and high-pressure pipeline was the main developing flow of gas pipeline in the world in order to increase the pipeline throughput. But there were several problems for the natural gas pipeline transportation. Firstly, high energy consumption was the outstanding problem for long-distance, big-diameter pipeline. Secondly, it took the hidden trouble of vital safety accident when using the design pressure or pressurization to maintenance the throughput for aging pipeline. Thirdly, it was required that the same diameter pipeline conveyer should have the economic and reasonable elastic adjusting ability because of the law of gas field exploitation and the various demand at different period. Fourthly, one of the key problems for the economic and rational exploitation was the transportation dynamics and energy consumption with high proportion to the total cost when exploitation the gas filed was in the hash natural conditions region, including offshore, desert, swamp, and alpine region.The best way to solve these problems was using drag reducing agents(DRAs). Using DRAs could improve the throughput, decrease the pipeline pressure, save energy, and improve the safety, etc. It had two main functions:On the one hand, the friction was decreased keeping the throughput invariant and the throughput was improved keeping the pressure drop invariant. Thus, the labor and material were saved. On the other hand, the elastic throughput was improved in order to meet the different gas fields and area. The elastic throughput was improved and the rigid pipeline changed into elastic when DRAs were used in the practical pipeline transportation. It also solved the outstanding problem of high energy consumption for long-distance, big-diameter pipeline. At the same time, the operating pressure of pipeline was reduced and the running safety coefficient was improved when using DRAs to maintain the throughput for the aging pipeline.At present, the inner-coated drag reduction technology was adopted to reduce the pipe wall roughness, which obtained excellent results and better economical benefits. But, for the inner-coated drag reduction technology, the construction equipments were complex and the cost was high. Especially, the drag reduction efficiency reduced and the inverse effect happened because of the runaway coating after long-time transportation and irregular pigging. It must stop production, dismount, and clean in order to repair. It was very difficult in the engineering technology. More important, the inner-coated drag reduction technology had fatal weakness that the exfoliated inner-coatings directly affected the high speed operation blade of compressor, on the severe case, blade was damaged causing the compressor outage.In 1990s, the concept of gas DRAs technology was firstly introduced according to the fatal weakness of inner-coated technology. The content of this concept was that the chemicals with surface activity said as gas DRAs were periodically injected into gas pipeline, the polar terminal was adsorbed onto the pipe iron wall surface to form the elastic film, so the pipe wall roughness was accordingly reduced and the drag reduction was obtained. The general idea of research and development according to the concept was that synthesis of compounds having high adsorption properties with iron and resistant to draw-off of high speed gas. At present, this technology was in developing phase abroad, but it was blank home.This paper overviewed the technology state and trend of gas pipeline development. According to the state that the natural gas DRAs was blank, and it was showed the industrial germination. Based on our experience and equipments on the studying process of "development and preparation technology of oil pipeline a-olefin", the natural gas DRAs drag reduction theory and the research and application of DRAs production were studied in this paper. The scientific and technical significance of synthesis of natural gas DRAs and its drag reduction performance studying was:Oil & gas storage and transportation was the grade-2 subject. Its transportation equipment can be solved by introducing, digesting, and adsorbing for all over the world. So, it was ranged in the same level. But the technology of drag reduction and throughput increasing possess a strategic significance, so only the products was for sale and the technique was keeping secret. The technology of drag reduction and throughput increasing was considered as the commanding point in this subject. It was representative for academic theory and engineering technology status of a county in the word. The "development and preparation technology of oil pipeline a-olefin" has won the second state technological innovation prize which mark a international leading level of China in the oil DRAs. Because the development of natural gas DRAs was drop behind in China compared to abroad, it was necessary to study energetically in order to catch up with and exceed the advanced level to take a place in the technology of drag reduction and throughput increasing field.For the above reasons, the author was engaged in development of natural gas DRAs and its drag reduction performance studying on the basis of taking part in "development and preparation technology of oil pipeline a-olefin". The following creative achievements were obtained after five years efforts.1. The drag reduction mechanism was studied using the methods of fluid mechanics, quantum mechanics, and molecular dynamics simulation on the basis of the experience of oil DRAs. The results showed that the compounds or polymers including amino, amide, and imidazole with high bond energy with iron had the preconditions to become natural DRAs. It was laying a solid foundation for the molecular design of natural gas DRAs.2. The natural gas drag reduction evaluation system was designed simulating the actual natural gas pipeline under the conditions of analyzing the energy loss in the transportation and the experience of the oil DRAs drag reduction evaluation system. The system was stable, reliable, maneuverability, and repeatable. The system was laying a solid foundation for the screening and development of natural gas DRAs.3. Three natural gas DRAs including stearic imidazole, AAMT, and VI-VTMS copolymers were designed and synthesized according to the drag reduction mechanism. The SEM and electrochemical methods were employed to study the property of film-forming. The results showed that three materials had better film-forming properties on the iron surface and the industrial application background.4. The drag reduction efficiency of three synthetic materials were studied using the natural gas drag reduction evaluation system. The technological conditions effect on the drag reduction efficiency were discussed and the optimum technological conditions were determined. The results showed that the drag reduction efficiency of stearic imidazole was 8.4%, AAMT was 10.03%, VI-VTMS was 22.72%. The drag reduction efficiency of VI-VTMS was international leading level and the polymerization process was simple. It was laying a solid foundation for the industrial development.
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