Journal of Oil and Gas Technology 石油天然气学报, 2016, 38(3), 67-78 Published Online September 2016 in Hans. http://www.hanspub.org/journal/jogt http://dx.doi.org/10.12677/jogt.2016.383027 文章引用: 冯定, 王杰, 钱利勤, 孙巧雷, 张红, 涂亿柳. 井下管柱的真实轴向力计算与应用[J]. 石油天然气学报, 2016, 38(3): 67-78. http://dx.doi.org/10.12677/jogt.2016.383027 Calculation and Application of Real Axial Force of Downhole Pipe String Ding Feng 1,2,3 , Jie Wang 1,2,3 , Liqin Qian 1,2,3 , Qiaolei Sun 1,2,3 , Hong Zhang 1,2,3 , Yiliu Tu 1,2,3 1 School of Mechanical Engineering, Yangtze University, Jingzhou Hubei 2 Oil and Gas Drilling and Well Completion Tools Research Center, Jingzhou Hubei 3 Hubei Collaborative Innovation Center of Unconventional Oil and Gas (Yangtze University), Wuhan Hubei Received: Mar. 10 th , 2016; accepted: Apr. 15 th , 2016; published: Sep. 15 th , 2016 Copyright © 2016 by authors, Yangtze University and Hans Publishers Inc. This work is licensed under the Creative Commons Attribution International License (CC BY). http://creativecommons.org/licenses/by/4.0/ Abstract The calculation precision of pipe string’s fraction was directly related to the quality of well com- pletion. Domestic and foreign scholars have established a lot of models to calculate the friction of pipe string, of which the “rigid rod model” was more frequently used, but the static pressure without liquid at ends of micro-unit was not taken into account when the buoyancy of pipe string on the unit is calculated, thus the calculation of axial force was the effective axial force. For the pipe string unit that only side is contacted with liquid, if the displaced fluid gravity is used as its buoyancy, additional axial force would be generated at the ends of the unit, the real axial force of pipe string is calculated based on the study above, a new calculation formula is established for improving the accuracy of calculation of pipe string friction. To verify the accuracy of the model, the existing rigid rod model and the model established in this paper are used to solve the stress of water injection string when it is lifted in a actual well, and Matlab program is used to solve it. By comparing the results of the two models, the results of the model of this paper show that the pipe string exists neutral point, the pipe string above the neutral point is subjected to tension and the pipe string below the neutral point is subjected to pressure, this result is closer to the actual stress state of pipe string. Keywords Rigid Model, Effective Axial Force, Real Axial Force, Additional Axial Force, Neutral Point Open Access