A study on mechanical properties of equal wall thickness rubber bushing of positive displacement motor based on hydrogenated nitrile butadiene rubber aging test

Abstract

Shale gas production has become the main driver of global gas production growth. Deep shale gas is difficult to extract, which puts forward higher requirements for drilling speed increase. The downhole power drilling tools are mainly screw drilling tools. Conventional screw drill tool stator bushing has poor heat dissipation, which is prone to thermal hysteresis failure, shortening drilling tool life, and is not suitable for high temperature and high pressure environment of deep shale gas wells. Equal wall thickness screw drilling tools and hydrogenated nitrile rubber have better high temperature resistance. Therefore, based on the thermal aging experiment and constitutive model of the rubber changes the displacement of the inner cavity of the stator bushing and the difference between the front and the back is up to 21.6%. The increase of the interference and eccentricity between rotor and motor leads to the increase of the maximum von Mises stress of the stator bushing and the thermal hysteresis temperature. The influence of the interference is greater than the influence of the eccentricity so that the interference should be given priority in the design. This paper provides a theoretical reference for the design and optimization of equal wall thickness bushing of positive displacement motor.

Keywords

PDM / HNBR / Constitutive model / Thermal hysteresis / Numerical simulation

Declaration of competing interests

The authors declare that they have no competing interests.

Acknowledgements

This work was supported jointly by the Southwest Petroleum University Drilling Tools Youth Technology Innovation Team(2018CXTD03), Sichuan Science and Technology Plan Applied Basic Research Project(19YYJC1058), the National Natural Science Foundation of China (Grant No. 51604234), and Youth Scientific Research Innovation Team Project of Sichuan Province (Grant No. 2017TD0014).

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