The influence of the longitudinal oscillation damper location on the rod string fatigue resistance
The article presents calculations of the rod strings for fatigue strength under the pulsating loading cycles corresponding to the main and the most affected part of the string when installing the longitudinal oscillations vibration damper of rods under the polished rod and above the pump plunger, i. e. with a minimum and maximum effect on the increase in the intensity of the rods fatigue failure in an arbitrary cross-section along the length of the string. Kinematic schemes of some constructions of longitudinal oscillations vibration dampers are given. Based on axial loads dynamograms, under different values of the fluid dynamic level between the tubing and casing columns, an example of calculation for the upper part of the rod string is considered for the inclined well of the Western Siberia (the Jurassic deposits). The solution given in the example confirms the rationality of the installation place of the damper in the area where the waves of the rod string longitudinal oscillations are formed, i. e. above the pump plunger or, better, the junction point of the vibration damper with the pump itself. In the latter case, it becomes possible to further reduce the hydraulic resistance of the near-well zone of the productive reservoir, i. e. increase of a well production. Also, to a certain extent, the neutralization of the difference in the changes values of the relative elastic elongations (according to Hooke) of the tubing and rod strings is provided.