Analysis and improvement of the design of uninterrupted connection of pump rods

Abstract

Based on the field data, numerous failures of the downhole equipment of sucker rod pumping units occur, especially of the sucker rod strings. They are subject to corrosion, wear and alternating loads. The stress-strain state of the threaded connection elements is determined by the nature of the distribution of loads along the threads, which is uneven and depends on many factors. Despite this, the development of new designs of sucker rod connections and measures to improve the efficiency of operation and their research is an urgent task. In addition to the threaded connections of the sucker rods, there were a number of threadless designs that were not used in the fields, but they passed certain tests. The article presents these connection designs and discusses their advantages and disadvantages in comparison with standard threaded connections. Simulation modeling of a standard connection of sucker rods made it possible to investigate its stress-strain state and identify hazardous areas (stress concentrators). The stress-strain state of the threaded connection of the sucker rods has been investigated, the design of this connection has been improved and it has been established that, in comparison with the standard threaded connection of the sucker rods, the investigated has certain advantages. It was found that with an increase in the number of protrusions and depressions in a threaded joint, stresses decrease, which are concentrated in dangerous sections and along the contact planes. Convex contact planes also reduce stress, especially at the joint surface. Research has shown that the stresses generated in a threadless sucker rod joint are less than the stresses generated in a standard sucker rod and sleeve joint. Although the difference between these stresses is insignificant, attention should be paid to changing the geometric parameters of the threadless connection of the sucker rods, thereby reducing the maximum stresses.