﻿ 井下管柱的真实轴向力计算与应用

# 井下管柱的真实轴向力计算与应用Calculation and Application of Real Axial Force of Downhole Pipe String

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.

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