RU2737750C2 - Check valve of electric centrifugal pump for cleaning of submersible equipment from precipitation and method of its implementation - Google Patents

Abstract

FIELD: oil industry.

SUBSTANCE: invention can be used to remove various types of precipitation from the cavity of electric centrifugal pumps, for example, inorganic salts, solid suspended sand particles, asphalt-resinous and other substances. Check valve of electric centrifugal pump for cleaning of submersible equipment from sediments includes housing with upper and lower connecting threads, spherical valve covering seating seat, splined shaft of submersible electric pump of pump, which extends into cavity of pump head. Between the splitting shaft of the electric-centrifugal pump and the check valve there is an impeller containing a body with a stepped inner cavity and blades inclined to the vertical. Upper end face of the housing is connected to the rod entering the through hole of the pump check valve seat. Inside housing by means of threaded connection stepped drive rod enters. Lower part of the stock under the lower edge of the impeller is connected to the splined bushing, which is fixed on the splined shaft of the pump. In order to implement method of submersible equipment cleaning from sediments pump is stopped for repair. Chemical reagent is pumped from the wellhead to the tubing string in the designed volume. Electric centrifugal pump is turned in the reverse direction for the valve ball seating into the seat and the time for the sediment dissolution in the equipment is maintained. Pump is started in constant mode with normal direction of its shaft rotation.

EFFECT: technical result is improved reliability of opening of check valve and removal of deposits from cavity of downhole equipment using chemical reagents.

2 cl, 2 dwg

Description

The proposed invention relates to the oil industry and can be used to remove various types of sediments from the cavity of electric centrifugal pumps and tubing strings, for example, inorganic salts, solid suspended particles of sand, asphalt-resinous and other substances.

With the formation of sediments in the tubing and the cavity of the electric centrifugal pump, a decrease in pump flow occurs due to a significant increase in resistance in the submersible equipment and an emergency occurs. Control over the process of sedimentation in the submersible equipment is carried out by measuring the flow rate of the well on the surface.

At the outlet of the electric centrifugal pump (ESP), check and whipping valves are installed in the tubing. When the pump is stopped, the check valve prevents the outflow of liquid from the tubing string into the well and the pump shaft unwinding in the opposite direction. The churning valve allows, on the contrary, to release the tubing from fluid for lifting equipment during repair (Bogdanov A.A. Submersible centrifugal electric pumps for oil production. M .: Nedra. 1968. P.52-54). Pouring fluid from the tubing into the well is carried out by dumping a load into the tubing, which, having reached the whipping valve, breaks it and forms an opening connecting the tubing cavity with the annulus.

Known check valve (patent RU No. 56940 U1, declared. 07.04.2006, publ. 27.09.2006), consisting of a body, a saddle fixed in the body, a shut-off element in the form of a ball. A cylindrical channel and a stop for the axial movement of the shut-off element in the channel with openings for the fluid flow are formed in the body, and the stop is made in one piece with the body. The axes of the holes for the fluid flow are located on the generatrices of the cylindrical channel. The saddle is secured at the inlet with a nut and / or a threaded bushing with keyways.

Known valve of a borehole centrifugal pump (patent RU 72268 U1, declared. 12/26/2007, publ. 04/10/2008), containing a housing with internal and external connecting threads and a saddle fixed in it and placed in the channel of the limiter of axial movement of a ball locking element. The valve seat is equipped with a bore for the sealing ring and is fixed with respect to the body by a cylindrical bushing and a washer with holes for the passage of formation fluid. In the upper part of the valve body there is a branch pipe with a sludge trap pipe screwed into it, equipped with radial holes for the formation fluid passage. A washer with holes for the passage of formation fluid is fixed against axial movement relative to the valve body by means of a spring ring, and the branch pipe is mounted in the body by means of a key with a spring ring.

A common disadvantage of the above analogs is the impossibility of removing various sediments from the tubing cavity and the electric centrifugal pump by pumping various chemicals or coolant into the well through the tubing string and then a submersible pump.

Known cleanable downhole filter (patent RU 2441139 C1. Appl. 12.07.2010. Publ. 27.01.2012), including outer and inner pipes with holes, a filter element fixed between the pipes, a wave converter. The filter element is made in the form of a wire twisted along the height. The wave converter is made in the form of a compression spring.

To clean the filter after clogging, the centrifugal pump is stopped and then started in the opposite direction of the rotor rotation. The backflow of the liquid washes away the adhered sand particles from the filter element.

This device has the disadvantage that it is impossible to create a reverse flow of fluid from the tubing through the pump into the well in the case of a check valve at the outlet of the centrifugal pump.

Known check valve - automatic, consisting of a body with a seat, which is seated with a poppet valve with a stem (Patent RU 2038463 C1. Check valve - automatic. Appl. 17.03.1992. Publ. 27.06.1995). The stem is passed through a hole in the cross-piece installed in the body. A spring is installed between the washer and the crosspiece. On the side of the washer, a bushing is mounted on the stem. At certain stop pressures, the stem wedges, allowing the turbo drill to be cleaned. The disadvantage of such a valve is the dependence of the opening or closing of the shut-off element on the pressure and flow rate of the liquid, which is unacceptable for the operation of a submersible pump.

The closest to the proposed invention in terms of the technical essence and the achieved result is a check valve for an electric centrifugal plant and a method for cleaning the filter at the pump intake (patent RU No. 2544930 C1. Check valve for an electric centrifugal plant and a method for cleaning the filter at the pump intake. Appl. 17.09.2013. Publ. 02.16.2015). The design of the valve includes a poppet valve stem made of a hollow, a movable sleeve made of stepped, the lower part of which with a smaller diameter forms a sliding friction pair with the outer surface of the hollow valve stem, and in the upper part of the sleeve there are horizontal holes with larger diameters in comparison with the valve stem holes.

Flushing is performed by lowering the load into the pipe string on a scraper wire through a lubricator at the wellhead, which by its own weight compresses the spring and moves the movable step-shaped sleeve downward, aligning the horizontal holes in the movable sleeve and the hollow poppet valve stem and creating a fluid overflow under hydrostatic pressure from the string pumping - compressor pipes into the well through the pump cavity and filter, and after washing the filter, the load is removed from the well and the pump is started up.

The disadvantage of this method is the need to lower the load on a scraper wire to the valve through the tubing string. A well with bent holes or its inclination does not allow lowering the load through the tubing under its own weight. On the other hand, the presence of any deposits (salts, paraffin) on the tubing wall also impedes the descent of the load.

The technical problem of the proposed invention is to improve the reliability of opening the check valve and removing sediments from the cavity of the downhole equipment using chemical reagents.

The problem is solved by the fact that in the known check valve of an electric centrifugal pump, which includes a housing with upper and lower connecting threads, a spherical valve that overlaps the landing seat, a splined shaft of a submersible electric pump of the pump that goes into the cavity of the pump head, according to the invention, between the splined shaft of an electric centrifugal pump and an impeller is placed with a check valve, containing a housing with a stepped internal cavity and blades inclined towards the vertical, the upper end of the housing of which is connected to a rod entering the through hole of the pump check valve seat, and a stepped drive rod enters the housing by means of a threaded connection, the lower part of which under the lower end of the impeller, it is connected to a spline sleeve fixedly mounted on the spline shaft of the pump.

The solution to this problem is achieved in a method for cleaning submersible equipment from sediments, including stopping the pump for repair, flushing the cavity of the submersible pump, receiving filter and tubing string from sediments and then starting the electric centrifugal pump into operation, according to the invention, immediately after shutdown, injection is performed from the wellhead into the tubing string of the chemical reagent in the calculated volume, then turn on the electric centrifugal pump in the opposite direction to seat the valve ball into the seat and hold the time for the sediment to dissolve in the equipment and then start the pump in a constant mode of operation with the usual direction of rotation of its shaft.

FIG. 1 and 2 show the diagrams of the check valve. It consists of a housing 1 screwed with a fishing head 2 of a submersible electric centrifugal pump (not shown in the figure). A tubing (not shown in the figure) is screwed into the upper part of the housing 1.

The housing 1 contains a spherical valve 3, a landing seat 4 with a cylindrical stop 5 and an O-ring 6. Between the splined shaft 7 of the electric centrifugal pump and the valve seat 4 is an impeller consisting of a hollow cylindrical housing 8 and blades 9. A rod is screwed into the upper part of the housing 8 10 entering the seat bore 4. The inner cavity of the body 8 is made stepped. A stepped drive rod 11 is placed on the thread inside the body. Part of the drive rod 11 of a larger diameter is threaded, and the lower part of a smaller diameter is without a thread. The lower part of the drive rod 11 through the O-rings 12 comes out of the housing 8 and is screwed into the spline sleeve 13, which is fixedly fixed to the spline shaft 7 of the pump by means of a bolt 14. The impeller blades 9 are inclined relative to the housing.

The work of the check valve of the electric centrifugal pump is as follows.

During normal operation of a submersible electric submersible pump, the rotation of the shaft through the splined sleeve 13 is transmitted to the drive rod 11. In the absence of liquid between the splined shaft 7 and the valve seat 4, rotation of the pump shaft will cause the impeller to rotate at the same angular velocity. But the presence of liquid and blades 9 will lead to some deceleration of the impeller rotation. The appearance of a difference in the speeds of their rotation will lead to the rotation of the impeller housing relative to the splined shaft 7, and, consequently, relative to the drive rod 11. Rotation of the impeller relative to the drive rod 11 will lead to the movement of the impeller housing up or down due to their threaded connection, depending on the direction of the thread in the housing 8 impellers. Threading for starting the pump and its subsequent operation is performed based on the movement of the impeller upward. This movement occurs until the upper end of the drive rod stops at the lower end of the rod 10. After that, the upward movement of the impeller will stop and the impeller housing 8 will begin to rotate at the rotational speed of the spline shaft 7 of the pump. At this point, the rod 10, having moved completely upward, will take a position at which the ball 3, when the pump stops, will no longer be able to sit tightly and close the seat 4, i.e. the check valve will remain open and only the weight of the ball 3 will act on the stem 10.

During the operation of the pump, various sediments can form in the pump or tubing string, reducing the pump flow and often leading to an emergency. To remove sediment, the electric centrifugal pump is stopped. Since the ball 3 can no longer close the seat 4 into the tubing string and a fluid overflow from the tubing string into the well through the pump is formed, a reagent solution is immediately injected to remove sediment. After pumping the calculated portion of the solution, the pump is started for a short time in the opposite direction of rotation. Due to the deceleration of the impeller in a liquid medium (oil or water-oil mixture), the casing 8 will begin to move downward until the upper part of the drive rod 11 rests against the protrusion inside the casing 8. After that, the casing 8 and the splined shaft 7 of the pump will begin to rotate at the same angular velocity. When the impeller housing 8 and the rod 10 reach the extreme lower position, the ball 3 will completely block the seat 4, and the hydrostatic pressure of the entire liquid column in the tubing will act on the check valve.

Next, a certain calculated time delay is performed to dissolve the precipitate. After complete dissolution of the sediment in the tubing, the unit is put into operation. In this case, the well fluid under the pressure of the pump will raise the ball 3 above the seat 4 and the pumping of the reaction products from the tubing and then the formation production from the well will begin. At the same time, the resistance of the blades 9 will contribute to the rise of the impeller and the extension of the rod 10 into the hole in the seat 4 to a position that prevents the ball from seating in the seat afterwards after stopping the pump.

To remove salt deposits from the cavity of the electric centrifugal pump, the check valve is closed by starting the pump in the opposite direction after the solvent of the salt precipitate completely fills the pump cavity.

The injection of solvents directly into the tubing string significantly reduces the consumption of reagents in comparison with the injection of reagents through the annulus of the well.

When sediments of mechanical impurities accumulate on the filter and in the receiving part of the pump, the pump is simply flushed with the pumped liquid without the use of chemical reagents.

The inclination of the blades 9 (Fig. 2) to the vertical allows you to create an additional head for pumping liquid and to increase the efficiency of the pump. The inclination of the blades allows you to create an additional head for pumping fluid from the well, as well as a head for pumping fluid down from the tubing string to the pump with a short change in the direction of rotation.

O-rings 12 prevent mechanical impurities from entering the inside of the impeller housing 8 in order to avoid jamming of the threaded pair of the drive rod 11 and its wear.

The technical and economic advantages of the proposed invention are the simplicity and reliability of preliminary opening of the valve and its subsequent closure due to a short-term start of the pump in the opposite direction, as well as the possibility of removing sediments from submersible equipment using small volumes of chemical reagents. In addition, the extension of the stem into the bore of the seat to open the valve is performed without any effort immediately after starting the pump, since the ball is stripped off by the pressure of the liquid generated by the pump.

Claims (2)

1. Check valve of an electric submersible pump for cleaning submersible equipment from sediments, including a housing with upper and lower connecting threads, a spherical valve that overlaps the landing seat, a splined shaft of a submersible electric pump of the pump that goes into the cavity of the fishing head of the pump, characterized in that between the splined shaft of the electric submersible the pump and the check valve there is an impeller containing a body with a stepped internal cavity and blades inclined to the vertical, the upper end of the body of which is connected to the rod entering the through hole of the pump check valve seat, and a stepped drive rod enters the body by means of a threaded connection, the lower part which, under the lower end of the impeller, is connected to a spline sleeve fixed motionlessly on the spline shaft of the pump. 2. A method of cleaning submersible equipment from sediments, including stopping the pump for repair, flushing the cavity of the submersible pump, the intake filter and the tubing string from sediments and then starting the electric centrifugal pump into operation, characterized in that immediately after the shutdown, the pump is pumped from the wellhead into the string the pumping-compressor pipes of the chemical reagent in the calculated volume, then turn on the electric centrifugal pump in the opposite direction to plant the valve ball according to claim 1 into the seat and hold the time for dissolving the sediment in the equipment, after which the pump is started in a constant mode of operation with its usual direction of rotation shaft.

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