DRIVE OF A DOWNHOLE PUMP

Abstract

The invention relates to oil production equipment and can be used for actuating submersible downhole plunger pumps in the operation of marginal wells. A drive of a downhole pump comprises a housing, a submersible electric motor with a protector, the drive shaft of which is coupled to the screw of a ball screw actuator that is movably coupled to the housing and is coupled to a rod which is sealed inside the housing. The interior cavities of the housing are filled with oil and are in communication with an annular space of the borehole through an elastic shell. The drive shaft of the electric motor is connected to the ball screw actuator via a reverse reduction gear having a switching mechanism. The reverse reduction gear is switched only when the nut of the ball screw actuator (or of an additional ball screw actuator) arrives at its terminal positions, thus improving the operational reliability of the drive. The electric motor operates in a continuous mode, which increases the reliability and energy efficiency of the drive owing to the absence of repeated starting and stopping of the electric motor; consequently, a spike in current intensity upon start-up is avoided. Therefore, the solutions used in the invention make it possible to improve the reliability and energy efficiency of the drive of a downhole pump.

Claims

1. A borehole pump drive, comprising a housing, a submersible motor with a hydraulic protector having a drive shaft connected to a screw of a rolling screw-nut transmission, said transmission is in a movable connection with the housing and is connected to a rod sealed in the housing, internal cavities of the housing are filled with oil and are communicated with an annular space of the borehole through an elastic shell, wherein the drive shaft of the motor is connected with the rolling screw-nut transmission through a reverse reduction gear with a switching mechanism.

2. The borehole pump drive according to claim 1, wherein the switching mechanism consists of a tie-rod coupled with a nut of the rolling screw-nut transmission and the reverse reduction gear, wherein the tie-rod has an end position lock.

3. The borehole pump drive according to claim 1, wherein the switching mechanism consists of an additional screw-nut transmission installed between the rolling screw-nut transmission and the reverse reduction gear, a nut of the additional screw-nut transmission is connected through a pusher with the reversible reduction gear, and the pusher has an end position lock.

4. The borehole pump drive according to claim 1, wherein the reverse reduction gear is connected with the rolling screw-nut transmission through an elastic coupling.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The invention is explained by the figures, in which:

[0013] FIG. 1—a downhole pump drive with a switching mechanism in the form of tie-rod.

[0014] FIG. 2—a downhole pump drive with a switching mechanism in the form of additional screw-nut transmission.

DETAILED DESCRIPTION OF THE INVENTION

[0015] Downhole pump drive (see FIG. 1) contains housing 1, submersible motor 2 with protector 3. The shaft of the electric motor (not shown in FIG. 1) through shaft 4 of protector 3 is connected with intermediate shaft 5 by clutch 6. Intermediate shaft 5 is connected through reverse reduction gear 7 and clutch 8 with screw 9 of rolling screw-nut transmission. Nut 10 of rolling screw-nut transmission is rigidly connected through hollow rod 11 and centralizer 12 with stem 13 sealed in housing 1 by seals 14.

[0016] Tie-rod 15 with retainer of extreme positions 16 passing through hole in nut 10 is arranged along housing. Stops 17 and 18 are made on tie-rod 15.

[0017] An elastic shell 19 is installed in the lower part of the housing, the inner cavity of the elastic shell 19 is communicated with the internal cavities of the housing, and the outer cavity is connected with the annular space (annulus) through openings 20.

[0018] A cable 21 is used for powering the submersible motor.

[0019] In the downhole pump drive with the switching mechanism in the form of additional screw-nut transmission (see FIG. 2), this additional screw-nut transmission is installed between reverse reduction gear 7 and screw-nut screw 9, the transmission consists of screw 22 and nut 23. Nut 23 is connected by pusher 24 with reverse reduction gear 7. Pusher has end position lock 25.

[0020] The downhole pump drive operates as follows.

[0021] Downhole pump drive is filled with oil, connected to pump of plunger type, and on tubing string is lowered into borehole. Cable 21 (see FIG. 1) current is supplied to the electric motor 2. The torque from the shaft of the electric motor 2 through the shaft 4 of the protector 3 and the reverse reduction gear 7 is transmitted to the rolling screw-nut transmission screw 9, with the rotation of which, the nut 10 reciprocates. Thereby, the nut 10 transfers the movement through the hollow rod 11, the centralizer 12 and the stem 13 to the plunger-type pump.

[0022] When the extreme position is reached, the nut moves due to the stop 17 (for the lowermost position) or the stop 18 (for the extreme upper position)) a tie-rod 15 which switches the direction of rotation of the reverse reduction gear 7. In order to prevent sticking of the switching mechanism in the middle position, when the torque from the electric motor 2 will not be transmitted to the screw 9, the lock of the extreme positions 16 is used, which ensures finishing and fixing of the tie-rod 15 to the extreme position.

[0023] In order to maintain constant internal volume of housing 1 at the outlet-closing of rod 13, flexible shell 19 is used, which is compressed at the outlet of rod 13, and during the stroke-unclamping.

[0024] The cycle is repeated multiple times over the entire operating time of the actuator.

[0025] To exclude large-length rod between reversible reducer 7 and rolling screw-nut transmission, additional screw-nut transmission may be installed, the pitch of the screw 22 is smaller than the pitch of the screw 9, so that the tappet 24 has considerably smaller axial dimensions than the tie-rod 15. The operation of the tappet 24 is similar to that of the tie-rod 15.

[0026] The clutch 8 may be resilient (elastic) to avoid shock loads when switching the direction of rotation of the screw 9 of the screw-nut transmission.

[0027] A ball-screw or a roller-screw transmission may be used as the rolling screw-nut transmission, which leads to enhanced efficiency.

[0028] The submersible motor 2 may be asynchronous, asynchronous with an increased voltage or a permanent magnet motor.

[0029] Reverse reduction gear is switched only when rolling screw-nut transmission nut (or nut of additional screw-nut transmission) reaches its extreme positions, which increases the reliability of the drive operation.

[0030] The electric motor operates in a constant mode, which improves the reliability and the power efficiency of the drive because there is no repeated start-stop of the electric motor, and hence the abrupt increase of the current intensity at the start of the start is eliminated.

[0031] Thus, the solutions used in the invention make it possible to increase the reliability and the energy efficiency of the downhole pump drive.