INVESTIGATION OF THE LOADS ON THE ROD PUMPING UNIT WHEN THE FLUID LEVEL IN THE WELL CHANGES

The balance of the pumpjack, which is the most common type of drive for downhole rod pumps, has a significant impact on the efficiency of pumping operation of the well. It determines the degree of loading of the pumpjack, the amount of electricity consumed. However, during the operation of the well, the balance of the drive may be disrupted due to a change in the load on the balancer head due to the weight of the liquid column in the annulus and acting on the pump plunger. This situation is noted for wells operating in the periodic pumping mode, as well as when the inflow of reservoir fluid changes for various reasons (unstable inflow, deterioration of permeability of the downhole zone of the formation, changes in reservoir pressure during development and other reasons). The paper considers the issues of forming loads on the drive of rod installations at a variable dynamic fluid level in the well. A mathematical model is presented describing the formation of loads on the head of the pumpjack balancer, taking into account possible fluctuations in the dynamic level. Verification of the proposed model was performed and a good agreement was obtained between the model and field dynamometer cards. A field example shows that a decrease in the dynamic liquid level causes an increase in maximum loads on the balancer head by more than 10 %. It was found that due to a change in the balance of loads on the drive, the torque on the crank shaft increases when the rods move upwards, which leads to an increase in the asymmetry of loads on the drive and a violation of the balance of the rocking machine. The relevance of the use of dynamic balancing systems is substantiated, which allow maintaining the balance of loads acting on the drive in changing external conditions.