CN100390372C - An underground reciprocating pumping unit driven by a rotating motor - Google Patents

Abstract

The utility model relates to an underground reciprocating oil pumping unit driven by a rotary motor, relating to an oil pumping unit. Existing pumping units have problems such as high energy consumption, large horse-drawn carts, large size, and large inertial loads. The buffer oil pipe (13) of the present invention is provided with a motor (12), the output shaft of the motor (12) is connected with the lead screw (15), and the motor drives the lead screw to rotate and will drive the plunger (18) matched with the lead screw to make Linear movement, thus transporting the crude oil underground to the surface. The invention is based on the principle of converting the rotary motion of the motor into the linear motion of the plunger pump based on the transmission form of the rotary motor + ball screw, and has the advantages of simple structure, stable operation, high system efficiency, good energy-saving effect, and can meet the oil production process The requirement of automatic control and the characteristics of adapting to harsh working environment, etc. At the same time, the pumping unit also has the advantages of low cost, high reliability, strong overload capacity, long stroke, high efficiency, good flexibility and simple structure, which is conducive to popularization and application.

Description

An underground reciprocating pumping unit driven by a rotating motor

technical field

The invention relates to an oil pumping unit.

Background technique

The most widely used conventional beam pumping unit oil recovery system is mainly composed of three parts: ground part: it consists of motor 1, reduction box 2 and four-bar linkage mechanism 3 (including crank, connecting rod, beam, beam), Composed of donkey head and rope hanger; underground part: oil pump 7, which is suspended at the lower end of oil pipe 5 in casing 6; the middle part connecting the ground and underground part: sucker rod column 4, which is composed of one or more Diameter sucker rod and couplings. The composition of the conventional beam pumping unit oil recovery system is shown in Figure 1.

The pumping unit oil recovery system transfers electrical energy from the surface to the downhole fluid, thereby lifting the downhole fluid to the surface. The working process of the whole system is a process of continuous energy transfer and conversion, and every transfer and conversion of energy will have a certain loss.

Among the three components of the pumping unit oil production system, the structure and working principle of the underground part and the middle part of different systems are basically the same, and the main difference of the system lies in the difference of the pumping unit. Therefore, the difference of the pumping unit determines the energy consumption of the oil production system of the pumping unit.

The basic working principle of the beam pumping unit is to use electric energy to convert the rotary motion of the motor, and then use the four-bar linkage mechanism to convert the linear reciprocating motion of the suspension point after being decelerated by the reducer. It has simple structure, high reliability, and is easy to damage. It has the advantages of less parts, simple operation, convenient maintenance and low maintenance cost. However, due to the structural characteristics of the conventional beam pumping unit itself, it is determined that it has poor balance effect, large net torque pulsation of the crankshaft, negative torque, low load rate, low work efficiency, "big horse and small cart" and energy consumption Higher shortcomings, mainly manifested in the following four aspects:

1. The problem of high energy consumption: The energy loss of the beam pumping unit mainly comes from the following two aspects:

①. Motor loss: In general, when the rotating motor works under the condition of output power (60%-100%) rated power, its efficiency is close to the rated efficiency, about 90%, that is, the motor loss is about 10%. However, because the load of the motor of the pumping unit changes very violently and frequently, in each stroke of the pumping unit, the output power of the motor will appear two instantaneous power maximums and two instantaneous power minimums (generally this The values of the two maximum and minimum values are not equal), the maximum instantaneous power may exceed the rated power, and the minimum value is generally negative power, that is, the motor not only does not output power, but is driven by the pumping unit And power generation, so the change of the output power of the motor is far beyond the range of (60%-100%) rated power, especially when the pumping unit is not well balanced, its motor may even be in the range of (20%-120%) rated power At this time, the efficiency of the motor decreases, and the loss will inevitably increase. From the field measured data, the loss of the motor is as high as 30%-40%.

②. Transmission loss: Transmission loss mainly includes belt transmission loss, reduction box loss and commutation loss.

Belt transmission loss can be divided into two categories, one is load-independent loss, including bending loss around the pulley, friction loss entering and exiting the wheel groove, and wind resistance loss. When multiple belts are driven, due to belt length error and wheel groove Power loss due to error. The other type is load-related losses, including elastic sliding losses, slipping losses, radial sliding friction losses between the belt and the wheel groove, etc. Generally, the losses of belt transmission are mainly bending loss and elastic sliding loss. Field measurement data shows that the belt transmission efficiency of a large number of pumping units is about 85%, so the belt transmission loss is about 15%.

The loss of the gearbox includes bearing loss and gear loss. There are three pairs of bearings in the gearbox, which are generally rolling bearings. As the speed and shaft diameter increase, the bearing loss also increases, and the amount of grease added to the rolling bearing will also affect the loss. Generally, under the condition of good lubrication, the loss of one pair of bearings is about 1%, so the loss of three pairs of bearings of the gearbox is about 3%. There are generally three pairs of herringbone gears in the reduction box. When the gears are in transmission, there is relative sliding between the meshing tooth surfaces, so friction and power loss will occur. Adding lubricant between the gear meshing surfaces can avoid direct metal contact and reduce friction loss. The transmission power loss of a pair of gears is about 2%, and the transmission loss of the three pairs of gears in the pumping unit reduction box is 6%. Therefore, the total power loss of the gearbox is about 9%-10%, which is the data under the condition of good lubrication. If the gearbox is poorly lubricated, the power loss will increase and the efficiency will also decrease.

The reversing part of a conventional beam pumping unit is mainly a four-bar linkage mechanism, generally with three pairs of bearings and a wire rope, and its losses mainly include deformation loss of donkey head wire rope and friction loss of bearings. The steel wire rope that hangs the sucker rod column on the donkey head of the pumping unit repeatedly contacts with the donkey head to be squeezed and deformed, and is stretched repeatedly at the same time, so deformation loss occurs, and the deformation loss of the steel wire rope is about 2%. The power loss of the three pairs of bearings is about 3%. Therefore, considering the wire rope and the bearings comprehensively, the energy loss of the four-bar linkage mechanism of the beam pumping unit is about 5%.

Considering the above three aspects, the mechanical transmission energy loss of the conventional beam pumping unit itself is about 30%.

2. The problem of large horse-drawn carts: the beam pumping units in actual production work in the state of "big horse-drawn carts" with low power factor, low efficiency and high energy consumption all the year round, which is caused by the following factors:

①. When selecting the motor capacity of beam pumping units, it is often in pursuit of a large safety factor or a large change in system load. As a result, the motor capacity is too large, resulting in the phenomenon of "big horses and small carts", causing the motor to deviate from the optimal work point, operating efficiency and power factor decrease. Generally speaking, the selection of motor power is always greater than the actual load requirements, so the motor seldom operates within its rated power range, and even at the maximum load, it cannot reach the rated power. If the load is in a changing state for a long time, the waste of energy is more serious.

②. The beam pumping unit is a mechanical device with a large moment of inertia. When working, especially the heavy oil and high pouring oil structure wells are started with load, which requires high power to start, and the overload capacity of the Y series motor is general (generally is twice the rated load), therefore, in order to meet the needs of starting, it has to be equipped with a motor with a larger rated power to drive. In addition, the motor load of the pumping unit is a variable load with impact. In order to make the drive The pumping motor runs stably and has a certain overload capacity, and the motor should be equipped according to the maximum power of the pumping unit. For a long time, most of the pumping unit motors used in oilfields are in light-load operation in actual operation, and even individual operation sections are no-load operation. The load rate of most motors is lower than 45%, and the power factor is lower than 0.6. The electromechanical motor has been running under the condition of low load and low power factor for a long time, which has caused a large rate loss of lines, transformers and motors. In addition, most of the motors of the beam pumping units adopt the direct start method, which not only causes impacts and accidents on the power grid and the drag system, but also causes huge energy loss due to the 8-10 times the starting current.

③ When the pump device is adapted according to a certain stroke length, piston diameter, etc., and when the stroke frequency is completely determined, the working capacity of the pumping unit becomes a constant quantity. With respect to the change of well load, the fixed capacity of the pumping unit cannot respond to the changing load during the pumping process. Therefore, it often occurs that the working capacity of the pumping unit is excessive, which is what we often call the problem of a large horse-drawn cart. Excessive reactive power extraction or low-efficiency extraction leads to dissatisfaction with the extraction level, and the pumping unit is often at half load or light load. working status. Nearly 80% of the oil wells in our country are light-load oil wells. After the peak period of oil field development, the amount of underground oil reserves is small and the oil pumping capacity decreases. In this case, the pumping unit needs to run continuously, and sometimes it is "half-pumped" or "empty-pumped", and the phenomenon of "big horse-drawn cart" appears.

④. The characteristics of pumping unit operation are that the operating load changes periodically and the difference is large. Therefore, the motor is in a large horse-drawn trolley during operation, and the average power factor is very low. In addition, the actual load of most pumping units is much smaller than the rated load. The oil pump itself is a large horse-drawn cart, so the problem of a large horse-drawn cart is more serious. Generally, the average load rate of the ten-type pumping unit is lower than 30%, or even below 15%, and the average power factor is 0.1-0.4. The average load rate of the pumping unit is below 20%, the power factor is about 0.2, the reactive current is large, and the line loss is a prominent problem in the power consumption of the pumping unit.

⑤ For any induction motor directly connected to the power grid, no matter how big the load is, its excitation current is fixed, and the current used to generate torque decreases with the decrease of the load, while the excitation current remains unchanged. Therefore, when the motor is running below the rated load, the power factor is less than the rated power factor. The lighter the load, the lower the power factor.

3. The size problem after the stroke is increased:

When the conventional beam pumping unit increases the stroke, the torque of the reduction box will increase proportionally, and the corresponding weight and size will be heavier and larger. Take the 12-type beam pumping unit as an example, the maximum load is 120kN, the minimum load is 60kN, the stroke is 3M, the torque of the gearbox is 53kN.m, if the stroke is increased to 4.2m, the torque of the gearbox will increase to 75kN .m, it can be seen that the stroke is increased from 3m to 4.2m, and the reduction box is increased from 53kN.m to 105kN.m, which is an increase of 2 grades. In addition, after the stroke is increased, the size of the four-link must be increased due to the limitation of the swing angle of the beam.

Therefore, after the stroke of the conventional beam pumping unit is increased, its overall size and total weight will be greatly increased. m, the total weight of the pumping unit increased from 15t to 25t, a net increase of 66.6%. This is due to the structural characteristics of the beam pumping unit itself, which cannot be developed for long-stroke, heavy-duty heavy-duty pumping units.

4. The problem of excessive inertial load: the four-bar linkage mechanism of the conventional beam pumping unit makes the motion of the donkey head similar to simple harmonic motion, and its maximum speed and minimum speed are much higher than the speed of uniform motion, so the acceleration is relatively The uniform motion is also much larger, resulting in a large inertial load, which makes the pumping unit bear too much load and shortens the service life of the pumping unit.

Therefore, although people have done a lot of research on pumping unit energy saving for many years, manufacturers at home and abroad have successively developed front-mounted pumping units, out-of-phase crank pumping units, air-balanced pumping units, and special-shaped pumping units (double donkeys). head), curved beam pumping unit, diameter-adjusting variable torque pumping unit (two-stage balance), barbell beam pumping unit, etc. However, these pumping units have not been converted from electric energy into rotary motion, and then four Linkages convert rotary motion into linear reciprocating motion and thus do not solve the fundamental problem.

Contents of the invention

Aiming at the problems of high energy consumption, large horse-drawn carts, increased size after stroke increase and excessive inertial load in the existing pumping units, the present invention provides a low-cost, high-reliability, strong overload capacity, long-term pumping unit. The pumping unit has high stroke, high efficiency, good flexibility and simple structure.

An underground reciprocating pumping unit driven by a rotary motor, which includes a motor controller 8, a cable 9, an oil outlet pipe 10, a plunger barrel 11, a motor 12, and a buffer oil pipe 13. The lower end of the oil outlet pipe 10 is connected to the plunger barrel 11 is sealed and connected, the lower end of the plunger barrel 11 is provided with a motor 12, and a buffer oil pipe 13 is sleeved outside the motor 12, and the upper end of the buffer oil pipe 13 is sealed and connected with the outer wall of the plunger barrel 11, and the column inside the buffer oil pipe 13 There is an oil suction hole 14 on the side wall of the plug barrel 11; the two ends of the cable 9 are respectively connected with the motor controller 8 and the motor 12;

A lead screw 15 is arranged inside the plunger barrel 11, and the lower end of the lead screw 15 is connected with the output shaft of the motor 12; Fixedly connected end fixture 16, the upper end of the screw 15 is connected with the end fixture 16 through a bearing, the end fixture 16 is provided with an axial through hole 16-1; A screw nut 17 is provided on the screw nut 17, and a plunger 18 is fixed on the screw nut 17; a one-way oil outlet valve 19 is arranged above the end fixing part 16 in the plunger barrel 11, and a one-way oil outlet valve 19 is arranged in the buffer oil pipe 13. A one-way oil inlet valve 20 is provided below the motor 12 . The underground reciprocating pumping unit driven by the rotary motor described in the present invention is based on the principle of converting the rotary motion of the motor into the linear motion of the plunger pump based on the transmission form of the rotary motor + ball screw. It is compatible with the linear motor pumping unit and Compared with the beam pumping unit, it has the characteristics of simple structure, stable operation, high system efficiency, good energy saving effect, can meet the requirements of automatic control of oil production process and adapt to harsh working environment, etc., especially suitable for deep wells, heavy oil, pumping control The use of oil wells has opened up a new way for the manufacture of heavy-duty pumping units. The pumping unit described in this invention has the following effects simultaneously:

1. Simple structure, low cost and high reliability: the plunger pump is driven by a rotating motor, without the need for a sucker rod column and a beam pumping unit reducer and four-bar linkage, and without a ground derrick, realizing rodless Therefore, the cost of the pumping unit can be greatly reduced and the reliability of the system can be improved.

2. High efficiency: The loss of the rotating motor is small, the power factor is high, the transmission efficiency of the ball screw is also high, and there is no need for the reducer and the four-bar linkage of the sucker rod column and the beam pumping unit, realizing the rodless pump oil. At the same time, the transmission efficiency of the rotary motor + ball screw is also much higher than that of the linear motor. Therefore, the present invention not only has high efficiency of the driving element itself, but also has a short transmission chain of the whole system, which greatly improves the oil production efficiency.

3. Long stroke: the underground reciprocating pumping unit driven by a rotating motor does not use a four-bar linkage, which overcomes the disadvantage of increasing the torque of the gearbox when the stroke of the beam pumping unit increases, and only needs to increase the length of the screw. , The overall size and total weight of the pumping unit are small, so it is suitable for long strokes.

4. Small inertia: The movement law of the underground reciprocating pumping unit driven by the rotating motor is a uniform motion for most of the time, except for the short-term acceleration and deceleration movement of the upper and lower dead points, which greatly reduces the inertial load and improves the performance of the pumping unit. Big improvement.

5. Strong overload capacity: Since the variable frequency drive motor has a high overload capacity, it can solve the requirement for high thrust when starting, so there is no need for "big horse-drawn carts".

6. Good flexibility: Due to the transmission form of rotating motor + ball screw, there are few transmission links and the system is easy to control. The stroke (within the length of the screw) and stroke times of the pumping unit can be changed in real time and arbitrarily.

Description of drawings

Fig. 1 is a schematic structural view of an existing conventional beam pumping unit, and Fig. 2 is a schematic structural view of the present invention.

Detailed ways

Embodiment 1: This embodiment is an underground reciprocating pumping unit driven by a rotating motor, which includes a motor controller 8, a cable 9, an oil outlet pipe 10, a plunger barrel 11, a motor 12, and a buffer oil pipe 13. The lower end of the oil outlet pipe 10 is sealingly connected with the plunger barrel 11, and the lower end of the plunger barrel 11 is provided with a motor 12, and a buffer oil pipe 13 is set outside the motor 12, and the upper end of the buffer oil pipe 13 is sealed with the outer wall of the plunger barrel 11 Connected, on the side wall of the plunger cylinder 11 inside the buffer oil pipe 13, an oil suction hole 14 is opened, and a one-way oil inlet valve 20 is arranged in the buffer oil pipe 13 below the motor 12. Both ends of the cable 9 are respectively connected with the motor controller 8 and the motor 12;

A lead screw 15 is arranged inside the plunger barrel 11, and the lower end of the lead screw 15 is connected with the output shaft of the motor 12; The end fixing part 16 is fixedly connected, and a one-way oil outlet valve 19 is arranged in the plunger barrel 11 above the end fixing part 16. The upper end of the screw 15 is connected to the end fixing part 16 through a bearing, and the end The effect of external fixing member 16 is to fix the end of leading screw 15, prevents it from shaking and eccentricity. The end fixing part 16 is provided with an axial through hole 16 - 1 , and the axial through hole is a hole along the length direction of the screw, so that crude oil can enter the oil outlet pipe 10 from the plunger barrel 11 upward. A lead screw nut 17 is fitted on the lead screw 15, and a plunger 18 is fixed on the lead screw nut 17. When the motor controller 8 controls the motor 12 to rotate forward and reverse, the ball screw 15 will The rotary motion of the motor 12 is converted into the up and down linear reciprocating motion of the plunger 18, so the plunger 18 can continuously lift the crude oil from the underground oil well to the surface.

Motor controller 8 takes DSP or microprocessor as the core, it can receive signals from various sensors, and according to specific data processing methods and control rules, determine the rotational speed of the motor 12 rotor and the stroke of the lead screw nut 17, and then control the column Pump strokes and strokes. The motor 12 can be a multi-phase permanent magnet synchronous motor (brushless DC motor), or a multi-phase induction motor or a multi-phase reluctance motor, both of which can achieve the purpose of the present invention. Its specific working process is as follows: the motor controller 8 rectifies, filters, and inverts the AC power of the ground power distribution system, and then inputs it to the downhole motor 12 through the cable 9 to provide energy for the rotation of the output shaft of the motor 12. The lower end of the rod 15 is connected with the output shaft of the motor 12, so the rotation of the output shaft of the motor 12 will drag the screw 15 to rotate, and the rotation of the screw 15 will drive the screw nut 17 and the plunger 18 that cooperate with it to move upward in a straight line At this time, the buffer oil pipe 13 has been filled with oil. During the upward movement of the plunger 18, on the one hand, the pressure will be transmitted downward through the oil suction hole 14 to close the one-way oil inlet valve 20. On the other hand, the pressure will be transmitted through the end fixing piece The axial through hole 16-1 on 16 uploads the pressure to open the one-way oil outlet valve 19, thereby pushing the crude oil in the plunger barrel 11 into the oil pipe 10 and lifting it from the oil pipe 10 to the ground; when the plunger 18 moves When the upper end of the plunger barrel 11 is reached, the motor controller 8 controls the motor 12 to reverse, and then the screw nut 17 and the plunger 18 move downward in a straight line. At this time, the pressure in the plunger barrel 11 and the buffer oil pipe 13 decreases. The oil outlet valve 19 is closed, and the oil inlet valve 20 is opened. Under the action of pressure, the crude oil is sucked into the buffer oil pipe 13 from the outside of the buffer oil pipe 13 through the one-way oil inlet valve 20, and then enters the plunger from the buffer oil pipe 13 through the suction port 14. Inside the cylinder 11. Make motor 12 forward rotation, reverse rotation, forward rotation... repeatedly in this way, just can continuously lift crude oil to ground from underground.

Claims (2)

1. an underground reciprocating pumping unit driven by a rotary motor is characterized in that it comprises a motor controller (8), a cable (9), an oil outlet pipe (10), a plunger barrel (11), a motor (12), Buffer oil pipe (13), the lower end of the oil outlet pipe (10) is in sealing connection with the plunger barrel (11), the lower end of the plunger barrel (11) is provided with a motor (12), and the outer cover of the motor (12) There is a buffer oil pipe (13), the upper end of the buffer oil pipe (13) is sealed and connected with the outer wall of the plunger barrel (11), and an oil suction hole ( 14); the two ends of the cable (9) are respectively connected to the motor controller (8) and the motor (12); A lead screw (15) is arranged in the plunger barrel (11), and the lower end of the lead screw (15) is connected with the output shaft of the motor (12); the oil suction hole (14) is in the plunger barrel (11). ) is provided with an end fixture (16) fixedly connected to the inner wall of the plunger barrel (11), the upper end of the screw (15) is connected to the end fixture (16) through a bearing, and the end Axial through hole (16-1) is provided on the fixed piece (16); Lead screw nut (17) is provided on described leading screw (15), and plunger (17) is fixed on described leading screw nut (17) 18); A one-way oil outlet valve (19) is arranged above the end fixing piece (16) in the plunger barrel (11), and a one-way oil inlet valve is arranged below the motor (12) in the buffer oil pipe (13) (20). 2. The underground reciprocating pumping unit driven by a rotating electric machine according to claim 1, characterized in that the motor (12) is a multi-phase permanent magnet synchronous motor or a multi-phase induction motor or a multi-phase reluctance motor.

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