| 摘要 |
<p>A counterweighted well pumping unit comprises two or more reversible motors, each of which is directly and operatively connected to a rotatable drive component mounted on a support structure positioned over a wellhead. For each motor, an elongate, flexible drive element is trained over the associated rotatable drive component, with one end of the flexible drive element connected to a counterweight assembly and the other end connected to a pump rod string associated with the wellhead. Actuation of the motors rotates the rotatable drive components, thus causing the drive elements to move the pump rod string and the counterweight assembly in opposite vertical directions. The rotational direction of the drive motors is alternated so as to alternate the directions of vertical movement of the pump rod string and the counterweight. The counterweight assembly may be concentric with or offset from the wellhead.</p> |
