CA2784163C

CA2784163C - Apparatuses for sealing against a well tubular

Info

Publication number: CA2784163C
Application number: CA2784163A
Authority: CA
Inventors: Craig Hall; Derek Tebay
Original assignee: Brightling Equipment Ltd
Current assignee: Brightling Equipment Ltd
Priority date: 2012-07-30
Filing date: 2012-07-30
Publication date: 2020-08-18
Anticipated expiration: 2032-07-30
Also published as: CA2784163A1

Abstract

An apparatus for a wellhead, the apparatus defining a passage for receiving a well tubular in use, the apparatus comprising: a stuffing box; a housing mounted on an upper end of the stuffing box; and one or more seals within the housing for sealing against the well tubular in use; in which the housing has two or more laterally removable housing segments. Other apparatuses and stuffing boxes are disclosed.

Description

APPARATUSES FOR SEALING AGAINST A WELL TUBULAR
TECHNICAL FIELD
[0001] This document relates to stuffing boxes for wellheads.
BACKGROUND

[0002] Stuffing boxes are used in the oilfield to form a seal between the wellhead and a well tubular passing through the wellhead, in order to prevent leakage of wellbore fluids between the wellhead and the piping. Stuffing boxes may be used in a variety of applications, for example production with pump-jacks, and inserting or removing coiled tubing. Stuffing boxes may incorporate a tubular shaft mounted for rotation in the housing for forming a stationary seal with the piping in order to rotate with the piping. The tubular shaft in turn dynamically seals with the stuffing box housing. Designs of this type of stuffing box can be seen in US 7,044,217 and CA 2,350,047. In other designs, the stuffing box may instead form a dynamic seal directly against the piping without incorporating a rotating tubular shaft. Stuffing boxes may be used for rotating or reciprocating pumps.

[0003] Leakage of crude oil from a stuffing box is common in some applications, due to a variety of reasons including abrasive particles present in crude oil and poor alignment between the wellhead and stuffing box. Leakage costs oil companies money in service time, down-time and environmental clean-up. Leakage is especially a problem in heavy crude oil wells in which oil may be produced from semi-consolidated sand formations where loose sand is readily transported to the stuffing box by the viscosity of the crude oil. Costs associated with stuffing box failures are some of the highest maintenance costs on many wells.
SUMMARY

[0004] An apparatus for a wellhead is disclosed, the apparatus defining a passage for receiving a well tubular in use, the apparatus comprising: a stuffing box; a housing mounted on an upper end of the stuffing box; and one or more seals within the housing for sealing against the well tubular in use; in which the housing has two or more laterally removable housing segments.

[0005] A method is also disclosed comprising: assembling one or more seals around a well tubular received by a stuffing box; assembling a housing around the one or more seals by laterally converging two or more housing segments around the one or more seals; and mounting the housing to an upper end of the stuffing box.

[0006] A stuffing box for a well tubular connected to operate a reciprocating pump is also disclosed, the stuffing box comprising: a housing defining a passage for receiving the well tubular; one or more seals at least partially within a removable portion of the housing for sealing against the well tubular in use; in which the removable portion of the housing is provided in two or more laterally removable housing segments.

[0007] In various embodiments, there may be included any one or more of the following features: The one or more seals comprise packing. The one or more seals are dynamic seals. The housing is bolted to the stuffing box. The housing is split into the two or more laterally removable housing segments along one or more planes running parallel to and originating from a stuffing box axis. The two or more laterally removable housing segments are secured together with bolts. The upper end of the stuffing box is defined by a threaded cap. The apparatus is adapted for production of wellbore fluids. The apparatus is adapted for use in a progressing cavity pump application. The apparatus is adapted for use in a reciprocating pump application. Each of the one or more seals comprise two or more laterally removable seal elements. Before assembling the one or more seals around the well tubular: laterally removing one or more of the housing segments from around the one or more seals; and removing one or more seals previously assembled around the well tubular.
The method is carried out without removing either the stuffing box or a drive head above the housing. The one or more seals are fully within the removable portion of the housing.A
second set of one or more seals is located within the housing for sealing against the well tubular in use.

[0008] These and other aspects of the device and method are set out in the description.

BRIEF DESCRIPTION OF THE FIGURES

[0009] Embodiments will now be described with reference to the figures, in which like reference characters denote like elements, by way of example, and in which:

[0010] Fig. lA is a view of a progressing cavity pump oil well installation in an earth formation for production with a typical drive head, wellhead frame and stuffing box;

[0011] Fig. 1B is a view similar to the upper end of Figure 1 but illustrating a conventional drive head with an integrated stuffing box extending from the bottom end of the drive head;

[0012] Fig. 2 is a side elevation view, in section, of a known stuffing box;

[0013] Fig. 3 is a perspective view of a stuffing box with a laterally removable housing mounted on an upper end of the stuffing box.

[0014] Fig. 4 is a section view taken along the 4-4 section lines of Fig.
3.

[0015] Fig. 5 is a perspective view of a stuffing box for a reciprocating pump and having a laterally removable housing.

[0016] Fig. 6 is a section view taken along the 6-6 section lines of Fig.
5, and illustrating a reciprocating pump.

[0017] Fig. 7 is a perspective exploded view of the stuffing box of Fig. 5.
DETAILED DESCRIPTION

[0018] Immaterial modifications may be made to the embodiments described here without departing from what is covered by the claims.

[0019] Fig. lA illustrates a known progressing cavity pump installation 10.
The installation 10 includes a typical progressing cavity pump drive head 12, a wellhead frame 14, a stuffing box 16, an electric motor 18, and a belt and sheave drive system 20, all mounted on a flow tee 22. The flow tee is shown with a blowout preventer 24 which is, in turn, mounted on a wellhead 25. The drive head 12 supports and drives a drive shaft 26, generally known as a "polished rod". The polished rod is supported and rotated by means of a polish rod clamp 28, which engages an output shaft 30 of the drive head by means of milled slots (not shown) in both parts. Wellhead frame 14 may be open sided in order to expose polished rod 26 to allow a service crew to install a safety clamp on the polished rod and then perform maintenance work on stuffing box 16. Polished rod 26 rotationally drives a drive string 32, sometimes referred to as a sucker rod, which, in turn, drives a progressing cavity pump 34 located at the bottom of the installation to produce well fluids to the surface through the wellhead.

[0020] Fig. 1B illustrates a typical progressing cavity pump drive head 36 with an integral stuffing box 38 mounted on the bottom of the drive head and corresponding to the portion of the installation in Fig. lA that is above the dotted and dashed line 40. An advantage of this type of drive head is that, since the main drive head shaft is already supported with bearings, stuffing box seals can be placed around the main shaft, thus improving alignment and eliminating contact between the stuffing box rotary seals and the polished rod. This style of drive head may also reduce the height of the installation because there is no wellhead frame, and also may reduce cost because there are fewer parts since the stuffing box is integrated with the drive head. A disadvantage is that the drive head must be removed to do maintenance work on the stuffing box. Surface drive heads for progressing cavity pumps require a stuffing box to seal crude oil from leaking onto the ground where the polished rod passes from the crude oil passage in the wellhead to the drive head.

[0021] Referring to Fig. 2, a known stuffing box 16 is shown having a housing 17 defining a passage 19 for receiving a well tubular 52. Mounted within the passage 19 is a series of dynamic seals 21 in the form of packing. The seals 21 are mounted between a first stop defined by a spring 23 compressed by a stationary sleeve 25, and a second stop defined by a threaded cap assembly 27 that defines an upper end 31 of the housing 17.
In use in a progressing cavity pump application, the pump-driven well tubular 52 rotates, with seals 21 dynamically sealing against well tubular 52 to prevent axial leakage of fluids through stuffing box 16.

[0022] When one or more or all of seals 21 fail, the seals 21 must be replaced. To do this cap 27 is axially removed off of well tubular 52, and seals 21 must be axially removed or cut off of the well tubular 52. Alternatively, well tubular 52 may be axially removed. Axial removal and reinstallation of such components may be accomplished using a flush by or workover rig. Once new seals 21 are installed, the stuffing box 16 is reassembled and well production resumed.

[0023] Referring to Figs. 3 and 4, an apparatus 41 for a wellhead 39 (Fig.
4) is illustrated, the apparatus 41 defining a passage 43 for receiving a well tubular 52 in use.
Apparatus 41 comprises a stuffing box 42, a housing 45, and one or more seals 47 (Fig. 4).
Like stuffing box 16, stuffing box 42 may comprise a stationary housing 44, and one or more seals 48 (Fig. 4). Stationary housing 44 defines a passage 50, for example a bore, for receiving a well tubular 52, passage 50 being part of passage 43 when assembled with housing 45. In use, stuffing box 42 may be mounted directly or indirectly to a wellhead 39 (Fig. 4). Housing 45 is mounted on an upper end 49 of the stuffing box 42, and one or more seals 47 are within the housing 45 for sealing against the well tubular 52 in use.

[0024] The housing 45 is provided in two or more laterally removable housing segments 45A and 45B. One or more of segments 45A, 45B may be split or semi-annular in shape. Segments 45A and 45B may be radial segments defined relative to a housing axis 51, such that all segments 45A, B seated within the same plane perpendicular to housing axis 51 collectively cover three hundred sixty degrees of radial coverage about housing axis 51. In further embodiments, each such segment makes up less than or equal to a one hundred eighty degree radial portion of housing 45 defined about housing axis 51, so that each segment may be removed in a lateral direction 53 (Fig. 3) relative to housing axis 51 (Fig. 4).

[0025] As shown in Fig. 3, the housing 45 may be split into the two or more laterally removable housing segments 45A and B along one or more planes, for example the plane identified by the section lines 4-4 and shown in Fig. 4, running parallel to and originating from stuffing box axis (shown as housing axis 51 in Fig. 4 and illustrated by section lines 4-4 in Fig. 3).

[0026] By providing laterally removable housing segments 45A and 45B, housing 45 may be disassembled without interfering with well tubular 52 or other components mounted below the housing 45. Thus, segments 45A and 45B may be laterally removed, each faulty one of seals 47 replaced, and segments 45A and 45B laterally converged all at less expense than repairing faulty seals in a traditional stuffing box such as the stuffing box 16 shown in Fig. 2.

[0027] Referring to Figs. 3 and 4, housing 45 may be mounted to upper end 49 of stuffing box 42, for example bolted using bolts 65 through holes 59 to the stuffing box 42 (holes 59 shown in the embodiment of Fig. 7). Other suitable mounting mechanisms may be used, such as a threaded connection.

[0028] The two or more laterally removable housing segments 45A and B may be secured together, for example with bolts 66. Along each radial face 68 terminating housing segment 45A as shown in Fig. 4 run a series of holes 69, 71, sized to fit either a bolt cap 64 or bolt thread 67 (Fig. 7), respectively. Split rings 61 may be positioned between bolts 66 and holes 69 and 71. Other suitable securing mechanisms may be used here and in other parts of the apparatus 41, such as spring, friction, snap fit, or clamp mechanisms.

[0029] The one or more seals 47 may comprise packing 72 as shown, or may be other suitable seals such as lip seals (not shown). If seals 47 are used in a stuffing box embodiment that uses a rotating tubular shaft, seals 47 may be either dynamic (seal between the rotating shaft and the housing 45) or static (against well tubular 52).
Like laterally removable housing segments 45A, B, seals 47 may be provided in laterally removable segments, for example split or semi-annular in shape. Laterally removable seal segments may also be secured together by suitable mechanisms such as bolts. Packing 72 is advantageous as packing 72 may be installed without a flush by unit or removing well tubular 52 because the packing 72 can be coiled around well tubular 52. Seals 47 may be resilient, non-mechanical seals. One or more of a biasing element (not shown) or an axial compression mechanism (such as spring 74) may be used to improve sealing. One or more rings such as brass rings 78 may be located on either side of seals 47. Brass rings 78 may be split (Fig. 7) to allow lateral installation, and may have aligned outer slots 55 for a gasket such as an o-ring (not shown).

[0030] Referring to Figs. 5 - 7, housing 45 may comprise part of a stuffing box 42, for example in a reciprocating pump 76 application. In such an embodiment, the one or more seals 47 may be at least partially, for example fully, within a removable portion, such as housing 45, of the stuffing box housing 44. A second set of one or more seals 48 may be located within the housing 44 for sealing against the well tubular 52 in use.
A sleeve 85 may be positioned within a base cap 84, the lower portion of which may be connected to a threaded adapter 90 for connecting directly or indirectly with a wellhead 39 (shown in Fig.
4).

[0031] Housing 45 may be retrofitted onto the upper end of an existing stuffing box 42 (Figs. 3 and 4), or supplied as part of a stuffing box 44 (Figs. 5-7).
Retrofitting an existing stuffing box 42 may be carried out in a variety of suitable ways. Referring to Fig. 4 for example, threaded cap assembly 27 (Fig. 2) may be removed, and a threaded base cap 84 threaded onto the upper end 49 of stuffing box 42. Next, an inner flanged sleeve 85 is nested within threaded base cap 84, sleeve 85 having an upper sleeve extension 87 for receiving and axially aligning housing segments 45A and 45B. Sleeve 85 may act as an upper stop for seals 48 and a lower stop for existing stuffing box 42 seals 47 as shown. Next, seals 47 and split rings 78 are installed, and housing segments 45A and 45B laterally converged and mounted by bolting to threaded base cap 84. In other embodiments, an existing stuffing box 42 may be retrofitted by modifying the threaded cap assembly 27 as required, for example by drilling axial holes (not shown) in threaded assembly (shown in Fig. 2) and mounting housing segments 45A and B.

[0032] Referring to Fig. 4, as eluded to above the embodiments described herein may be installed by the following sequence. The one or more seals 47 may be assembled around well tubular 52. Well tubular 52 may be initially received by a stuffing box 42 if the method is a method of retrofitting an existing stuffing box 42. Next, housing 45 is assembled around the one or more seals 47 by laterally converging the two or more housing segments 45A and 45B around the one or more seals 47. Next, the housing 45 is mounted to an upper end 49 of the stuffing box 42, or directly or indirectly to wellhead 39, depending on the application.

[0033] The method described above may form part of a method of replacing the one or more seals 47. In such an embodiment, one or more previously installed seals 47 may need replacing, and the following sequence carried out. One or more of the housing segments 45A and B may be laterally removed from around the one or more seals 47. Next, the faulty seal 47, or all of seals 47 are removed from around the well tubular 52.
Afterwards, the initial stages of the method may be carried out, for example by assembling a new set of the one or more seals 47 followed by assembling the housing 45 and mounting the housing 45. The method may be carried out without removing either the stuffing box 42 or a drive head above the housing 45.

[0034] Stuffing box 42 may be used for production of wellbore fluids, such as production in a progressing cavity pumping application. Stuffing box 42 may be adapted to be retrofitted into a wellhead 39, for example below the drive head (not shown). In other cases stuffing box 42 may be adapted for an integral application, for example in the style shown in Fig. 1B.

[0035] Referring to Fig. 4, it should be understood that various other components may be incorporated into stuffing box 42. For example, primary seals 92 may provided at various points between well tubular 52 and housing 44. Similarly, o-rings 86, gaskets, packing and other components may be used.

[0036] In general, where the word seal is mentioned in this document, one or more seals may be provided to effectively operate as a single seal, for example observed in the stacking of plural lip seals 48(Fig. 6) provided as the stationary seals for sealing against well tubular 52 in use. In addition, it should be understood that various other components may be provided with the stuffing box 42 for various wellhead applications to be carried out. For example, wellhead 39 may include any one or more of the other components illustrated in Fig. lA or 1B. In some applications, a drive head may rotate a well tubular 52, while other applications may incorporate a pump jack attached to reciprocate well tubular 52 as a polished rod. Stuffing box 42 may also be used for injection or pulling of tubulars, for example in a coiled tubing application. Stuffing box 42 may also be used in a slew pump application. Stuffing box 42 may incorporate a lubrication system (not shown) for lubricating various components, such as the one or more seals 47.

[0037] Various components discussed herein may include various sub-components, such as the plural sleeves that thread together to make up the housing 44 of Fig. 4.
Connections between components, or the mounting of one component to another, may be done through intermediate parts.

[0038] Figures may not be drawn to scale, and may have dimensions exaggerated for the purpose of illustration.
In the claims, the word "comprising" is used in its inclusive sense and does not exclude other elements being present. The indefinite article "a" before a claim feature does not exclude more than one of the feature being present. Each one of the individual features described here may be used in one or more embodiments and is not, by virtue only of being described here, to be construed as essential to all embodiments as defined by the claims.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A stuffing box for a well tubular connected to operate a reciprocating pump, the stuffing box comprising:
a housing defining a passage for receiving the well tubular;
one or more seals at least partially within a removable portion of the housing for sealing against the well tubular in use;
in which the removable portion of the housing is provided in two or more laterally removable housing segments; and in which the two or more laterally removable housing segments are secured together with bolts.

2. The stuffing box of claim 1 in which the one or more seals are fully within the removable portion of the housing.

3. The stuffing box of any one of claim 1 - 2 in which the one or more seals comprise packing.

4. The stuffing box of any one of claim 1 - 3 further comprising a second set of one or more seals located within the housing for sealing against the well tubular in use.

5. The stuffing box of any one of claim 1 - 4 in which the one or more seals are dynamic seals.

6. The stuffing box of any one of claim 1 - 5 in which the removable portion of the housing is bolted to the housing.

7. The stuffing box of any one of claim 1 - 6 in which the removable portion of the housing is split into the two or more laterally removable housing segments along one or more planes running parallel to and originating from a stuffing box axis.

8. The stuffing box of any one of claim 1 - 7 in which an upper end of the stuffing box is defined by a threaded cap.

9. The stuffing box of any one of claim 1 - 8 in which the stuffing box is adapted for production of wellbore fluids.

10. The stuffing box of any one of claim 1 - 9 in which the stuffing box is adapted for use in a progressing cavity pump application.

11. The stuffing box of any one of claim 1 - 10 in which each of the one or more seals, at least partially within the removable portion of the housing, comprise two or more laterally removable seal elements.

12. The stuffing box of any one of claim 1 - 11 in which the removable portion of the housing is mounted to the stuffing box through a base cap threaded to the stuffing box.

13. A stuffing box for a well tubular connected to operate a reciprocating pump, the stuffing box comprising:
a housing defining a passage for receiving the well tubular;
one or more seals at least partially within a removable portion of the housing for sealing against the well tubular in use;
in which the removable portion of the housing is provided in two or more laterally removable housing segments; and in which an upper end of the stuffing box is defined by a threaded cap.

14. The stuffing box of claim 13 in which the one or more seals are fully within the removable portion of the housing.

15. The stuffing box of any one of claim 13 - 14 in which the one or more seals comprise packing.

16. The stuffing box of any one of claim 13 - 15 further comprising a second set of one or more seals located within the housing for sealing against the well tubular in use.

17. The stuffing box of any one of claim 13 - 16 in which the one or more seals are dynamic seals.

18 The stuffing box of any one of claim 13 - 17 in which the removable portion of the housing is bolted to the housing.

19. The stuffing box of any one of claim 13 - 18 in which the removable portion of the housing is split into the two or more laterally removable housing segments along one or more planes running parallel to and originating from a stuffing box axis.

20. The stuffing box of any one of claim 13 - 19 in which the two or more laterally removable housing segments are secured together with bolts.

21. The stuffing box of any one of claim 13 - 20 in which the stuffing box is adapted for production of wellbore fluids.

22. The stuffing box of any one of claim 13 - 21 in which the stuffing box is adapted for use in a progressing cavity pump application.

23. The stuffing box of any one of claim 13 - 22 in which each of the one or more seals, at least partially within the removable portion of the housing, comprise two or more laterally removable seal elements.

24. The stuffing box of any one of claim 13 - 23 in which the removable portion of the housing is mounted to the stuffing box through a base cap threaded to the stuffing box.

25. A stuffing box for a well tubular connected to operate a reciprocating pump, the stuffing box comprising:
a housing defining a passage for receiving the well tubular;
one or more seals at least partially within a removable portion of the housing for sealing against the well tubular in use;
in which the removable portion of the housing is provided in two or more laterally removable housing segments; and in which the removable portion of the housing is mounted to the stuffing box through a base cap threaded to the stuffing box.

26. The stuffing box of claim 25 in which the one or more seals are fully within the removable portion of the housing.

27. The stuffing box of any one of claim 25 - 26 in which the one or more seals comprise packing.

28. The stuffing box of any one of claim 25 - 27 further comprising a second set of one or more seals located within the housing for sealing against the well tubular in use.

29. The stuffing box of any one of claim 25 - 28 in which the one or more seals are dynamic seals.

30. The stuffing box of any one of claim 25 -29 in which the removable portion of the housing is bolted to the housing.

31. The stuffing box of any one of claim 25 - 30 in which the removable portion of the housing is split into the two or more laterally removable housing segments along one or more planes running parallel to and originating from a stuffing box axis.

32. The stuffing box of any one of claim 25 - 31 in which the two or more laterally removable housing segments are secured together with bolts.

33. The stuffing box of any one of claim 25 - 32 in which an upper end of the stuffing box is defined by a threaded cap.

34. The stuffing box of any one of claim 25 - 33 in which the stuffing box is adapted for production of wellbore fluids.

35. The stuffing box of any one of claim 25 - 34 in which the stuffing box is adapted for use in a progressing cavity pump application.

36. The stuffing box of any one of claim 25 - 35 in which each of the one or more seals, at least partially within the removable portion of the housing, comprise two or more laterally removable seal elements.

37. A method comprising:
assembling one or more seals around a well tubular;
assembling a housing around the one or more seals by laterally converging two or more housing segments around the one or more seals, in which the housing forms at least part of a stuffing box for the well tubular; and mounting the housing directly or indirectly to a wellhead.

38 The method of claim 37 further comprising, before assembling the one or more seals around the well tubular:
laterally removing one or more of the housing segments from around the one or more seals; and removing one or more seals previously assembled around the well tubular.

39 The method of any one of claim 37 - 38 carried out without removing either the stuffing box or a drive head above the housing.