Method for cleaning centrifugal pump of oil well from precipitation

The alleged invention relates to the oil industry and can be used to remove various types of sediments from the cavity of electric centrifugal pumps, for example, inorganic salts, solid suspended particles of sand, asphalt-resinous substances, etc., as well as paraffin deposits from the walls of the upper part of the tubing string ( Tubing). With the formation of sediments in the cavity of an electric centrifugal pump or on the walls of the tubing, a decrease in pump flow occurs due to a significant increase in hydraulic resistance in the submersible equipment. Wax deposition occurs at the top of the tubing string due to oil cooling as it rises and the paraffinic hydrocarbon crystallization temperature is reached. 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. The check valve, when the pump is stopped, prevents the flow of fluid from the tubing into the well and the unwinding of the pump shaft 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. S. 52-54). Pouring fluid from the tubing into the well is carried out by dumping a load into the tubing, which, having reached the whipped valve, breaks it and forms a hole 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, filed. 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 axial movement limiter 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 the submersible pump.

A well-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 that the opening or closing of the shut-off element depends on the pressure and flow rate of the liquid, which is unacceptable for the operation of a submersible pump.

A known 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. 16.02.2015). 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 the check valve design is the need for a significant linear movement of the movable sleeve along the hollow rod due to the weight of the load for full alignment of the holes in this sleeve and the hollow rod and to ensure sufficient fluid flow from the tubing string into the pump cavity. With a large movement of the movable sleeve, the likelihood of scuffing the rubbing pair increases due to the ingress of solid particles, corrosion of metals or other reasons.

In addition, lowering the load into the tubing string through a scraper wire lubricator significantly complicates the pump cleaning technology, increases the costs and time of the operation. The ingress of mechanical impurities into the valve when lowering the load into the tubing does not allow the movable sleeve to move along the hollow rod and open the channel for fluid flow from the tubing into the well through the pump.

The closest to the proposed method is a method for studying productive formations at the same time - separate operation of a multilayer well and installation for its implementation (patent RU 2546218 C1. Appl. 29.01.2014. Publ. 10.04.2015. BI No. 10), selected as a prototype.

The installation contains an electrically actuated valve connected for power supply to the submersible telemetry unit, which makes it possible to close the flow area of ​​the valve seat with a retractable valve stem. If research is needed, turning on the electric motor leads to an axial movement of the valve stem and shutdown of the liquid through the valve seat.

However, to open the pump check valve, it is required to overcome a large force from the hydrostatic pressure on the valve stem from the top from the side of the liquid in the tubing. The force of opening the pump check valve after stopping, which must be overcome by the retractable rod of the shut-off element of the electric motor, is hundreds of kilograms, which makes it impossible to flush the pump with liquid from the tubing.

The technical problem of the proposed invention is to simplify the method for cleaning the pump from sediments and to improve the reliability and efficiency of its implementation by reducing the axial load on the motorized valve.

The problem is solved by the fact that in the known method, including stopping the well, supplying current to the electric motor of the valve with a retractable valve stem, flushing the cavity of the electric submersible pump with liquid from the tubing string under pressure, supplying the electric valve with reverse polarity current and closing the valve with subsequent start-up of the pump in accordance with the invention, the current is supplied to the electric motor of the valve to extend the stem of the shut-off body, while the pump is running, before stopping it for cleaning, then the pump is stopped and the calculated volumes of the chemical solvent of sediment and displacement fluid are pumped into the tubing string from the wellhead, and then the valve motor is supplied reverse polarity current to return the rising stem to its lowest position and seat the valve in the seat, after which the calculated time is maintained for the dissolution of the sediment by the chemical substance and after its expiration the pump is started up.

In fig. 1, 2 and 3 show schemes of the method implementation.

An electric centrifugal pump 3 was run into well 1 on the tubing string 2 (Fig. 1). Above the pump 3 in the tubing string 2, a check valve is installed, consisting of a body 4 with a seat 5 and a spherical valve 6 located inside. Below the seat 2, an electric motor 7 is located in the body, to which a cable 9 is connected through a sealed current lead 8, which supplies the electric motor 7 from the surface or from the telemetry system of the submersible electric motor of pump 3 (not shown in the figures).

The electric motor 7 of the valve has a retractable stem 10 passing through the seat 5. The stem 10 can be moved along the axis of the electric motor 7 using the electric motor reducer and the worm gear (not shown in the figures). The valve body 4 is connected to the pipes of the tubing string 2 with couplings 11. The submersible motor of the pump 3 is powered by cable 12.

The valve works as follows

After running the electric centrifugal pump 3 into well 1, the spherical valve 6 under its own weight sits in the seat 5 (Fig. 2). In this case, the stem 10 is in the lowest position, allowing valve 6 to completely close the seat 5. After starting the pump, the flow of fluid under the pressure generated by pump 3 will raise the valve 6 above the seat 5 and enter the tubing string 2.

During the operation of a complicated well, various sediments are formed in the pump, for example, inorganic salts, which block the flow path of the pump and reduce its flow. To dissolve the formed precipitation with chemical reagents and remove reaction products, a technological operation is performed, including the following operations. First, the electric motor 7 is turned on and the rod 10 is pushed to the extreme upper position, in which it will be above the seat 5 (Fig. 3). Then the electric centrifugal pump 3 is stopped. In this case, the valve 6, due to the presence of the stem 10, will not be able to sit down and close the seat 5 and will be held by the stem in a suspended position. Thus, after stopping the electric centrifugal pump 3, only a small load from the weight of the valve 6 will act on the rod 10. The advance extension of the stem 10 allows without any effort to ensure the opening of the valve 6 and create the possibility of a high pressure fluid flow from the tubing string 2 into the well through the pump cavity 3. Immediately after stopping the pump 3, the calculated volumes of the chemical reagent solution are pumped into the tubing string 2 from the wellhead , dissolving the sediment in the pump 3 and the displacement fluid, such as oil, for the purpose of non-productive consumption of the chemical reagent. After the solvent at the estimated time fills the cavity of the pump 3, a current is supplied to the electric motor 7 of the current valve of reverse polarity to return the stem 10 to the lowest position. In this case, the valve 6 will lower and close the landing seat 5 under high hydrostatic pressure in the tubing string 2. Then, the estimated time required for the reaction and dissolution of sediments in the working elements of the pump 3 is maintained. After that, pump 3 is put into operation, which pumps out the reaction products and restores the supply of formation fluid (Fig. 1 and 2).

In case of clogging of the inlet filter of the electric centrifugal pump with mechanical impurities, it is flushed with a liquid flow from the tubing string 2 without the use of chemicals.

The technical and economic advantages of the method are its simplicity and high reliability of implementation, as well as significant savings in the chemical reagent.