Calculation methodology of wellhead counterbalance weight of pumping units' combined rotary-wellhead counterbalancing
A significant part of the producing wells, operated by the sucker-rod pumping installations, is equipped with balancing beam-pumping units (BPU). The counterbalancing of balancing BPU is mainly realized by a mechanical method, i.e. by special counterweights (counterbalances). The existing technologies of pumping units counterbalancing cause considerable fatigue wear of above-ground equipment components due to high loads on BPU actuator (drive). This leads to premature equipment failure and increased power consumption. The listed facts make it necessary to look for innovative methods of pumping units counterbalancing, including systems with a combined rotor-wellhead counterbalancing. Additional BPU counterbalancing in such systems is achieved using a wellhead counterweight, that provides a directed vertically-upward force, caused by its weight and applied through a flexible rod directly to the wellhead rod. The wellhead counterweight installation makes it possible to partially compensate the constant load on the balancer head, caused by the weight of the rod string in the liquid, thus reducing the load on the balancer head, its support, and thereby to prevent wear of BPU components. The article presents the results of research of dynamic processes occurring during operation of a sucker-rod pumping unit with a wellhead counterbalancing system. The influence downhole equipment operating conditions on the estimated weight of a wellhead counterbalance meeting the criteria for minimizing the loads on the beam-pumping unit assemblies and ensuring the stable operation of the balance beam is considered. It is shown that equipping the well with an additional wellhead counterbalancing system significantly reduces the load on the balancer head, thus contributing to an increase of the uniform load of BPU assemblies and the pumping power and to a reduction of the electricity consumption.