RU2792501C1 - Wellhead stuffing box - Google Patents

Abstract

FIELD: seals.

SUBSTANCE: wellhead stuffing box is declared. The wellhead stuffing box comprises a body, an upper fixed main sealing unit and a lower backup sealing unit. The assemblies include sealing elements placed in cups with a central axial hole and pressure rings with a stop. The lower sealing assembly is configured for limited axial movement between the body stop and the upper sealing assembly to form a variable volume chamber. The chamber is equipped in its upper part with a check valve and a plug placed in the radial openings of the housing. The housing is provided with a cover configured for interaction with the pressure ring of the upper sealing unit. The body below the radial holes is provided with an upper stop. The upper and lower sealing units are equipped with spacer bushings spring-loaded relative to the cups, interacting with the pressure disks and configured for interacting with the cover and the upper stop of the body, respectively, at the upper position of the lower sealing unit.

EFFECT: increased life of the sealing units of the wellhead stuffing box.

2 cl, 3 dwg

Description

The invention relates to oil-producing equipment, in particular to a wellhead stuffing box, and can be used to seal the rod of a sucker-rod pump.

Known wellhead seal, which consists of a body, a fixed sealing unit with a pressure ring, a cover with a stop interacting with the pressure ring (see book: Molchanov A.G. Machines and equipment for oil and gas production, Moscow, Alliance Publishing House , 2010, p. 147, Fig. 5.16).

The disadvantages of this design are the lack of durability of the sealing unit and the possibility of oil leakage in case of leakage of the sealing unit.

Also known is a wellhead stuffing box containing a housing, an upper working and lower emergency sealing units with pressure rings installed with the possibility of forming an oil cavity between them, a cover with a guide sleeve and a stop interacting with the pressure ring of the working sealing unit (see Pat. RF No. 2205307 , MCP F16J 15/18, 2003).

The disadvantages of this design are the possibility of oil leakage in case of violation of the tightness of the working or backup sealing unit, the need for manual switching to the backup or emergency sealing units in case of violation of the tightness of the working sealing unit. In addition, the installation and dismantling of the sealing unit are characterized by significant labor intensity due to the collapsible design of the unit.

Well-known wellhead stuffing box containing a housing, the upper fixed working and lower reserve sealing units, including placed in the cups with a Central axial hole sealing elements, pressure rings with a stop, the lower sealing unit is installed with the possibility of limited axial movement between the housing stop and the upper sealing unit with the formation chamber of variable volume, equipped in its upper part with a check valve and a plug installed in the radial openings of the housing, the housing is equipped with a cover installed with the possibility of interacting with the pressure ring of the upper sealing assembly (see RF patent No. 2669313, IPC E21V 33/02, pub. 10/10/2018, bulletin No. 28), which is taken as a prototype.

The disadvantages of this design are the intense wear of the sealing elements and the possibility of oil leaks due to their constant axial preload, regardless of wear and pressure of the medium to be closed. In addition, the preload of the sealing elements of the upper sealing unit is controlled from the condition of ensuring tightness without controlling the contact pressure in the sealed pair.

The purpose of the proposed technical solution is to increase the resource of sealing units of the wellhead stuffing box.

This task is achieved by the fact that in the wellhead stuffing box containing the body, the upper fixed working and lower reserve sealing units, including sealing elements placed in the cups with a central axial hole, pressure rings with a stop, the lower sealing unit is installed with the possibility of limited axial movement between the body stop and an upper sealing assembly to form a chamber of variable volume, provided in its upper part with a check valve and a plug, placed in the radial openings of the housing, the housing is provided with a cover installed with the possibility of interacting with the pressure ring of the upper sealing assembly, according to the technical solution, the housing below the radial openings is equipped with upper stop, and the upper and lower sealing units - spring-loaded relative to the cups with spacer bushings that interact with the pressure disks and are installed with the possibility of interacting, respectively, with the cover and the upper stop of the housing when check the position of the lower seal assembly.

The distance sleeve of the upper sealing unit is spring-loaded relative to the pressure ring.

The proposed technical solution is illustrated by the drawing.

In FIG. 1 shows a diagram of the proposed wellhead gland (longitudinal section);

in fig. 2 - version of the wellhead seal;

in fig. 3 - version of the wellhead stuffing box with a controlled pressing force of the sealing elements.

The wellhead stuffing box contains a housing 1 (Fig. 1), in which the upper (working) 2 and lower (reserve or emergency) 3 sealing units are installed coaxially. The lower sealing unit 3 is installed with the possibility of limited axial movement between the stops 4 and 5 of the body with the formation of a chamber 6 of variable volume between the sealing units 2 and 3. The stops 4 and 5 are made, for example, in the form of a cylindrical protrusion and a split spring ring installed in the annular groove (not shown in Fig.).

The upper sealing assembly 2 is fixedly installed in the housing 1 and interacts with the stop 7.

Sealing units 2 and 3 contain sealing elements 11 and 12 installed in housings 8 and 9, made in the form of a glass with a central through hole (not shown in Fig.) in response to the polished rod 10. Units 2 and 3 are equipped with upper pressure rings 13 and 14 and stops 15 and 16 installed with the possibility of preloading the sealing elements 11 and 12. The sealing elements 11 of the upper sealing unit 2 are made, for example, in the form of gland packing, and the sealing elements 12 of the lower unit 3 are in the form of cuffs. Stops 15 and 16 are made, for example, in the form of split spring rings installed in the annular grooves (not shown in Fig.).

The upper sealing unit is fixedly fixed by the cover 17 by means of a distance sleeve 18 with the possibility of its interaction with the pressure ring 13 and with the formation of a guaranteed axial clearance (not shown in Fig.) between the end face of the cover 17 and the body 1, and is connected to the body 1 by a threaded connection. The cover 17 can be provided with a boot (not shown in the figure) for stripping the polished shock 10 as it moves down.

The lower sealing unit 3 is equipped with a distance sleeve 19, which interacts with the pressure ring 14 and is able to interact with the stop 5 of the housing 1.

Sealing units 2 and 3 are provided, for example, with sealing rings 20 and 21 to seal the gap between them and housing 1.

In the housing 1 between the stops 5 and 7, at least two through radial holes (not shown in Fig.) are provided, equipped with a check valve 22 and a plug 23. The chamber 6 can also be equipped, for example, with a pressure gauge 24 or a pressure sensor (Fig. . not shown).

The housing 1 is connected from the bottom to the tubing string (not shown in the figure) to form a cavity 25, and the rod 10 is connected to the drive (not shown in the figure).

Chamber 6 of variable volume is filled with lubricant.

The sealing units 2 and 3 (Fig. 2) can be equipped with springs 26 and 27 installed between the spacer bushings 18, 19 and the housings 8, 9 of the sealing units 2 and 3. The force of the springs 26 and 27 is less than the force from the pressure of the lifted oil acting from below on sealing units 2 and 3. The force from the pressure of the medium acting on the sealing units is determined by the following formula

where D, d - the outer diameter of the body of the sealing unit and the diameter of the polished rod;

p is the pressure of the formation medium.

When units 2 and 3 are equipped with springs 26 and 27, part of the force from the pressure of the medium is compensated by springs 26 and 27, preventing intense wear of the sealing elements 11 and 12.

The upper seal assembly 2 (Fig. 3) can be provided with a spring 28 placed between the spacer sleeve 18 and the pressure ring 13.

Installation and operation of the wellhead stuffing box is carried out as follows.

When assembling the sealing assembly 2, the pressing force of the sealing elements 11 is set to a minimum level. The pressing force of the sealing elements 12 of the assembly 3 is selected from the condition of ensuring tightness in the absence of a pressure drop under and above the sealing assembly 3.

When mounting the stuffing box, the lower sealing unit 3 with the spacer sleeve 19 is first installed until it interacts with the stop 4. The chamber 6 is filled with grease to the level of the plug 23. Next, the stop 5 is installed, the upper sealing unit 2. The cover 17 with the spacer sleeve 18 is installed to ensure the required preload of the sealing elements 11. Further, through the check valve 22, the chamber 6 can be supplemented with lubricant. Plug 23 is screwed into body 1.

With the reciprocating movement of the polished rod 10 in the cavity 25, the pressure of the produced medium, for example, oil, rises. Under the action of the pressure drop, the lower (emergency or backup) sealing unit 3 rises slightly, equalizing the pressure in the chamber 6 and the cavity 25. Under the action of the pressure drop, the upper working sealing unit 2 is put into working condition. The lower sealing unit 3, which is subjected to the same pressure from below and from above, remains in the non-working position. The sealing elements 12 of the node 3 interact with the rod 10 with a small preliminary contact pressure, set in order to ensure their tightness. Since the chamber 6 of variable volume is filled with lubricant, the wear of the sealing elements 11 of the sealing assembly 2 occurs with little intensity. When moving the rod 10 upwards, part of the lubricant from the chamber 6 can flow out.

With a decrease in the volume of lubricant in chamber 6, the pressure in it decreases. Under the action of a pressure drop, the sealing unit 3 moves upward, equalizing the pressure in chamber 5 and cavity 25. node 2.

With further movement of the node 3, when the remote sleeve 19 interacts with the stop 5, the pressure in the chamber 6 is reduced. Under the action of the created pressure drop, the sealing elements 12 of the assembly 3 are additionally pressed by the distance sleeve 19, increasing the contact pressure in the friction pairs. Further, the sealing of the rod 10 is carried out by the lower reserve sealing unit 3. In this case, the reading of the pressure gauge 24 shows zero pressure.

The operation of the wellhead stuffing box in FIG. 2 happens in a similar way. At the same time, units 2 and 3 are equipped with springs 26 and 27 provided that the pressure force of the working medium, determined by relation (1), is exceeded, the required force of pressing the sealing elements 11 and 12. Part of the force from the pressure of the medium is compensated by springs 26 and 27.

The operation of the upper sealing unit 2 of the wellhead stuffing box in FIG. 3 is carried out with an almost constant pressing force of the sealing elements 11. In addition, when assembling the stuffing box, it is possible to set the required pressing force of the sealing elements 11, for example, by the magnitude of the axial displacement of the cover 17 relative to the housing 1.

When the contact pressure in the friction pairs decreases, for example, when the sealing elements 11 and the rod 10 are worn, the pressure ring 13 under the action of the spring 28 restores the initial contact pressure.

Thus, the proposed device makes it possible to prevent oil leakage through the wellhead stuffing box in case of leakage of the working sealing unit 2. If the tightness of the working sealing unit 2 is lost, the backup sealing unit 3 automatically switches to operation.

It is possible to control the pressure in the chamber 6 of variable volume and the serviceability of the working sealing unit 2. Operation in a pure lubricant environment significantly increases the durability of the upper sealing unit 2.

When equipped between the cover 17 and the pressure ring 13 of the sealing unit 2 with a spring 28, it is possible to control the pressing force of the sealing elements 11 and maintain it during the operation of the sealing unit 2.

Claims (2)

1. A wellhead stuffing box containing a body, an upper stationary working and a lower reserve sealing assembly, including sealing elements placed in sleeves with a central axial hole, pressure rings with a stop, the lower sealing assembly is installed with the possibility of limited axial movement between the body stop and the upper sealing assembly with forming a chamber of variable volume, provided in its upper part with a check valve and a plug placed in the radial openings of the housing, the housing is equipped with a cover mounted with the possibility of interacting with the pressure ring of the upper sealing assembly, characterized in that the housing below the radial holes is equipped with an upper stop, and the upper and the lower sealing units - spring-loaded relative to the cups with spacer bushings interacting with the pressure disks and installed with the possibility of interacting with the cover and the upper stop of the body, respectively, at the upper position of the lower sealing unit. 2. The gland according to claim 1, characterized in that the spacer sleeve of the upper sealing assembly is spring-loaded relative to the pressure ring.

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