Accumulation of associated petroleum gas in the annulus is one of the negative factors that impede the intensification of mechanized oil production. An increase in annular gas pressure causes growth of bottomhole pressure, a decrease in back pressure to the formation and the inflow of formation fluid. In addition, accumulation of gas in the annulus leads to displacement and a decrease in the liquid level above the submersible pump. Insufficient level of the pump submersion (rod or electric submersible) causes a number of complications in the operation of mechanized production units associated with overheating of the elements in pumping units. Therefore, the development of technologies for optimizing the gas pressure in the annulus is relevant. Method for calculating the intensity of gas pressure increase in the annulus of production wells operated by submersible pumps has been developed. Analytical dependence for calculating the time interval of gas accumulation in the annulus, during which the dynamic level decreases to the pump intake, is obtained. This value can be used to estimate the frequency of gas withdrawal from the annulus using compressors. It has been found that the rate of increase in annular gas pressure in time increases non-linearly with a rise in the gas-oil ratio and a decrease in water cut, and also linearly increases with a rise in liquid flow rate. Influence of the operating (gas-oil ratio) and technological (value of the gas pressure maintained in the annulus) factors on the flow rate of the suspended reciprocating compressor driven by the beam engine, designed for forced withdrawal and redirection of the annular gas into the flow line of the well is analyzed.
The efficiency of sucker rod pump installations, which have become widespread in mechanized lift practice, is largely determined by the balance of the drive. During the operation of sucker rod installations, the balance of loads acting on the rod string and the drive can change significantly due to changes in the dynamic fluid level, which leads to a decrease in balance and an increase in loads on the pumping equipment units. The increase and decrease in the dynamic level in accordance with the pumping and accumulation cycle occurs in wells operating in the periodic pumping mode. It is shown that during the operation of equipment in a periodic mode, fluctuations in the dynamic level and, accordingly, in the loads acting on the nodes occur. This leads to the need for dynamic adjustment of the balancing weights to ensure the balance of the pumping unit. A system for automatic balancing of the rod drive has been developed, including a balancing counterweight, an electric motor that moves the load along the balance beam, a propeller and a computing unit. To study the effectiveness of the proposed device, a complex mathematical model of the joint operation of the reservoir - well - sucker rod pump - rod string – pumping unit has been developed. It is shown that due to the dynamic adjustment of the balance counterweight position, the automatic balancing system makes it possible to significantly reduce the amplitude value of the torque on the crank shaft (in comparison with the traditional rod installation) and provide a more uniform load of the electric motor. Equalization of torque and motor load reduces the power consumption of the unit.
The ECSPU pneumatic compensators with quasi-zero stiffness are proposed. The pneumatic compensator with quasi-zero stiffness is suggested to be made in the form of pneumatic spring assemblies having a power characteristic with a positive stiffness working area and a set of successively connected Belleville springs and a power characteristic with a working area of negative stiffness. Structurally, a set of Belleville springs is located inside the air spring and supports pneumatic compensator piston. As a result of adding the negative stiffness of the disc spring washers set and the positive stiffness of the pneumatic spring, the resulting system (the proposed pneumatic compensator) acquires a quasi-zero or specified low stiffness. The efficiency of the suggested pneumatic compensator was determined by the possibility of moving its piston from the effects of various pressure drops. It was assumed that the greater the distance the piston can move under a given action, the more effective the pneumatic compensator is. The effect of various forces acting on the piston in the case of pressure drops on the discharge line of the electric centrifugal submersible pump units (ECSPU) is simulated: a rapidly decreasing load; a sudden increase in the force acting on the piston and vibration impact. In all the considered examples, the displacement of the piston was several meters, which corresponds to the length of the working area of the power characteristic of the considered pneumatic compensator with quasi-zero stiffness. It is shown that existing pneumatic compensators, which are like gas caps, are in principle unable to provide the same displacement of the piston under the same effects on it. For their effective operation, the size of the gas cap should be several tens of meters, which is impossible in the conditions of the well. In the calculations, it is shown that it is possible to manufacture the necessary disk spring washers from various materials: steel; fiberglass FGM; beryllium bronze. Of particular interest are disk spring washers made of beryllium bronze, which are capable of withstanding up to 20 billion load cycles.
