Sludge trap for submersible electric centrifugal pump

Abstract

FIELD: oil producing industry.SUBSTANCE: invention is intended to facilitate the start-up of a submersible electric centrifugal pump (ECP). The device comprises a housing with a coupling connection at the top and a nipple connection at the bottom, a discharge grate with central and circumferential passage openings, above which a filter element made of wire mesh is installed, configured to move along the axis of the housing. The filter element is made in the form of a cup with an open base facing upwards towards the mouth, fixed on a movable rod at the top with a nut and washer, and at the bottom with a metal disk. The base of the filter element is fixed with two metal rings with protrusions having holes for screw connections; the metal disk is designed with the ability to hermetically close the passage holes of the discharge grate when the ECP is stopped. A limiting nut is installed on the lower part of the rod, designed to rest against the discharge grate when starting the ECP. The discharge grate is made in a glass, equipped with a thread at the bottom for connection through a coupling with an internal pipe of at least two meters in length, installed in a housing having an additional internal thread on top. The diameter of the base of the filter element made of wire mesh is 4-6 mm smaller than the internal diameter of the pump and compressor pipes.EFFECT: reliability of the ECP is increased and the start-up is facilitated by increasing the service life and reliability of the sludge trap.1 cl, 2 dwg

Description

[0001] The invention relates to the oil production industry and is intended to facilitate the start-up of a submersible centrifugal pump and prevent clogging of the upper stages of the pump with mechanical impurities settling from the tubing string when the pump is stopped.

[0002] During the operation of an electric centrifugal pump (ESP) installation, sludge settling from the tubing (sand, scale, oxides, etc.) when the submersible electric centrifugal pump (ESP) stops gets into its upper stages, which leads to complications during startup, increased wear of the working parts, and in some cases, jamming of the installation or overheating of the extension cable.

[0003] Using standard check valves above ESPs in complex wells proves insufficient. The valves become clogged, leading to leaks and subsequent mechanical impurities entering the ESP. The use of various protective filters and separators at the ESP intake cannot ensure complete purification of the produced product, especially with small particle sizes or with the sudden removal of large quantities of proppant after hydraulic fracturing. The situation is exacerbated by low-flow ESPs operating intermittently with frequent shutdowns and restarts.

[0004] A sludge trap is known (RU patent No. 134254, IPC F04D 13 / 10, published 11 / 10 / 2013), consisting of a branch pipe, to the lower end of which a washer is welded, which is clamped in the coupling connection of the pump-compressor pipes through one pump-compressor pipe above the check valve of the submersible centrifugal pump installation, and the upper part of the branch pipe has slotted holes for the passage of the extracted liquid and is sealed with a cone, the base diameter of which is larger than the outer diameter of the branch pipe.

[0005] The disadvantages of this sludge trap are:

[0006] - low efficiency due to small volume for collecting mechanical impurities in the annular space between the sludge trap pipe and the tubing pipe;

[0007] - low reliability due to the risk of breakage of the welded joint of the washer.

[0008] A sludge trap for a submersible centrifugal electric pump is known (RU patent No. 209131, IPC F04D 13 / 00, published 02.02.2022), comprising a cylindrical body with internal and external connecting threads, in the stepped opening of which a pipe is installed, at the second end of the pipe a tip with radial holes for the passage of liquid and a centralizer are installed using a threaded connection, the pipe is made consisting of one pipe section, the pipe is screwed into the stepped opening of the body, and the tip with the centralizer are made in the form of a single part.

[0009] The disadvantage of this sludge trap is its low efficiency due to the small volume for collecting mechanical impurities in the annular space between the sludge trap pipe and the tubing pipe.

[0010] The closest in design is a regenerable sludge trap for protecting submersible pumping equipment from the deposition of polluting particles (RU patent No. 2781103, IPC E21B 43 / 08, published on October 5, 2022), installed in a tubing string (TUB), comprising a housing, inside which a discharge grate is installed, above which a filter element is installed, configured to move along the axis of the housing and pressed against the grate by a spring mechanism, while the filter element is made of an elastic wire permeable material, or perforated fluoroplastic, or perforated disc-shaped polymer plates, or filter wire meshes.

[0011] The disadvantages of this trap include its limited scope of application in wells with low solids content, low efficiency, and low reliability in wells with high solids content. The main problem lies in its operation at high solids concentrations, especially after hydraulic fracturing. During prolonged pumping shutdowns, solids tend to accumulate above the filter element. This can lead to the formation of a dense plug, causing the filter element to jam. The consequences of such jamming are extremely negative: disruption of the ESP feed, subsequent equipment failure, and, as a consequence, the need for costly underground repairs. Therefore, the trap has a limited scope of application—wells with low solids content—and low reliability in more challenging operating conditions.

[0012] The technical result of the invention is to increase the reliability of operation and facilitate the start-up of the ESP by increasing the service life and reliability of the sludge trap.

[0013] The technical result is achieved by a sludge trap for a submersible centrifugal electric pump (ECP), comprising a housing with a coupling connection at the top and a nipple connection at the bottom, a discharge grate with central and circumferential passage openings, above which a filter element made of wire mesh is installed, configured to move along the axis of the housing.

[0014] What is new is that the filter element made of wire mesh is made in the form of a cup with an open base facing upwards towards the mouth, fixed on the movable rod at the top with a nut and washer, and at the bottom with a metal disk, which is a single product with the movable rod, and the base of the filter element is fixed with two metal rings with protrusions having holes for screw connections, and the metal disk is designed with the possibility of hermetically closing the passage holes of the discharge grate when the ESP is stopped, a limiting nut is installed on the lower part of the movable rod, designed to rest against the discharge grate when the ESP is started, the discharge grate is made in a glass equipped with a thread at the bottom for connection through a coupling with an internal pipe of at least two meters in length, installed in a housing having an additional internal thread on top,the diameter of the base of the filter element made of wire mesh is 4-6 mm smaller than the internal diameter of the pump and compressor pipes,

[0015] Fig. 1 shows a diagram of the proposed sludge trap during operation of the ESP, in Fig. 2 shows a diagram of the proposed sludge trap during the shutdown of the ESP, where the housing is 1, the coupling connection of the housing is 2, the nipple connection of the housing is 3, the discharge grate is 4, the central hole is 5, the circumferential passage holes are 6, the filter element made of wire mesh is 7, the movable rod is 8, the nut is 9, the washer is 10, the disk (plate valve) is 11, the limiter nut is 12, the metal rings are 13, 14, the projections with holes are 15, 16, the screw connections are 17, the cup is 18, the lower thread of the cup is 19, the coupling is 20, the internal pipe is 21, the additional internal thread in the housing is 22, the tubing pipe is 23.

[0016] Essence of the invention

[0017] A sludge trap for a submersible centrifugal electric pump comprises a housing 1 with a coupling connection 2 at the top and a nipple connection 3 at the bottom, a discharge grate 4 with a central 5 and circumferential passage 6 openings, above which a filter element 7 made of wire meshes is installed, configured to move along the axis of the housing 1.

[0018] The filter element 7 made of wire mesh is made in the form of a cup with an open base facing upwards towards the mouth, fixed on the movable rod 8 at the top by a nut 9 with a washer 10, and at the bottom by a metal disk 11 (plate valve), which is a single product with the movable rod 8.

[0019] Furthermore, the base of filter element 7 is secured by two metal rings 14 with projections 15 having holes for screw connections, and metal disk 11 is designed to hermetically seal the passage openings 6 of discharge grate 4 when the ESP is stopped. This prevents mechanical impurities from passing through discharge grate 4 and accumulating above filter element 7. Thus, the risk of filter plugging and jamming is eliminated, directly leading to increased reliability of the unit.

[0020] A stop nut 12 is installed on the lower part of the movable rod 8. It is designed to rest against the discharge grate 4 when the ESP is started. This ensures controlled movement of the rod.

[0021] The discharge grate 4 is made in a cup 18, equipped at the bottom with a thread 19 for connection through a coupling 20 with an internal pipe 21 of at least two meters in length, installed in a housing 1, which has an additional internal thread 22 at the top.

[0022] The diameter of the base of the filter element 7 made of wire mesh is 4-6 mm smaller than the internal diameter of the pump and compressor pipes 23.

[0023] Increased Service Life: The design of the filter element 7, a cup-shaped element with an open base facing upward (toward the wellhead), and the reduced base diameter of the filter element 7 compared to the inner diameter of the tubing 23, contribute to more efficient sedimentation of mechanical impurities in the annular space between the inner pipe and the tubing, eliminating catastrophic clogging of the filter element, including jamming, during long shutdowns, unlike its closest analogue. At the same time, during short shutdowns of less than 1 hour, typical for intermittent operation, the majority of mechanical impurities settle within the cup-shaped filter element, which is regenerated when the ESP is started. This reduces the load on the filter element 7 itself, increasing its service life and, consequently, the service life of the sludge trap as a whole. Furthermore, the ability to regenerate the filter element during ESP operation, unlike the prototype, also contributes to an increased service life.

[0024] The sludge trap for submersible centrifugal electric pump works as follows.

[0025] The sludge trap is lowered into the well together with the ESP on the tubing string and is installed through one tubing pipe above the check valve. A drain valve is also installed through one tubing pipe above the sludge trap (not shown in the diagrams).

[0026] When the ESP is operating, the liquid enters the inner pipe 21, and due to the pressure difference, the rod 8 with the disk 11 rises until the stop nut 12 stops against the discharge grate 4. Then the liquid enters the inner space of the tubing string 23 through the circumferential passage holes 6, through which it rises to the surface.

[0027] When the ESP is stopped, mechanical impurities contained in the liquid inside the tubing string 23 are deposited and accumulated inside the filter element 7. Some of the mechanical impurities are deposited in the annular space between the inner pipe 21 and the tubing string 23.

[0028] When the ESP is restarted, the rod 8 moves upward again, and the liquid flows through the circumferential passage holes 6 into the internal space of the tubing string 23, washing the filter element 7 from accumulated mechanical impurities, lifting them upward.

[0029] Thus, the proposed sludge trap for a submersible centrifugal electric pump improves the operational reliability and eases startup of the ESP by extending the service life and reliability of the sludge trap. This installation will be most effective in low-flow wells equipped with ESPs operating intermittently after hydraulic fracturing.

Claims

A sludge trap for a submersible centrifugal electric pump (ECP) comprising a housing with a coupling connection at the top and a nipple connection at the bottom, a discharge grate with central and circumferential through holes, above which a filter element made of wire mesh is installed, configured to move along the axis of the housing, characterized in that the filter element made of wire mesh is made in the form of a cup with an open base facing upwards towards the mouth, fixed on a movable rod at the top - with a nut and a washer, and at the bottom - with a metal disk, which is a single product with the movable rod, wherein the base of the filter element is fixed by two metal rings with protrusions having holes for screw connections, and the metal disk is configured to hermetically close the through holes of the discharge grate when the ESP is stopped, a limiting nut is installed on the lower part of the movable rod,designed to rest against the discharge grid when starting the ESP, the discharge grid is made in a cup equipped with a thread at the bottom for connection through a coupling with an internal pipe of at least two meters in length, installed in a housing having an additional internal thread on top, the diameter of the base of the filter element made of wire mesh is less than the internal diameter of the pump and compressor pipes by 4-6 mm.

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