Comparative evaluation of the executive mechanism of the balancing drive of the rocking machine equipped with a long-running stand

The article studies long-running drive of a downhole rod pumping unit, the design of which combines a traditional two-arm balancing drive (rocking machine) and a long-running stand. Modern downhole rod pumping units can extract oil, usually from one or two layers of wells up to 3500 m deep with a liquid flow rate from a cubic meter to several hundred cubic meters per day. It is investigated that the characteristics of balancing drives, performed by a number of world manufacturers allow the usage of pumping equipment in the range of fluid flow rate from the well from 1 to 40 m3 day. There is a general global trend of reducing the oil wells’ flow, as most oil fields are in the late stage of development, and therefore most traditional rocking machines are operated with low efficiency. Because the vast majority of of Ukrainian oil-production enterprises’ wells are equipped with beam pumping units their replacement by other types of the downhole rod pumps' drives requires significant investments. Equipping of a traditional balancing drive with a long-travel stand can improve drive’s technical characteristics. Determination of the design changes’ influence on kinematic and dynamic characteristics has been performed for two balancing options: 1 – traditional balancing of the drive with crank counterweights, placed on the cranks of the rocking machine in combination with a long-running stand and 2 – when the balance drive is used only to convert movement of a rope suspension bracket, and counterweights are placed on a long-running stand. It has been calculated that the first balancing variant allows to reduce the maximum torque up to 27.7 %, and by the counterweights placing on a long-running stand, the reduction of the maximum torque can be up to 62 %. It is proposed to use the standard deviation of the torque as a criterion for assessing the quality of balance.