WO2018049503A1

WO2018049503A1 - Stuffing box with enlarged bore

Info

Publication number: WO2018049503A1
Application number: PCT/CA2016/051532
Authority: WO
Inventors: David Mcadam; Brian MCADAM; James Orr
Original assignee: Western Oiltools Ltd
Current assignee: Western Oiltools Ltd
Priority date: 2016-09-16
Filing date: 2016-12-22
Publication date: 2018-03-22
Anticipated expiration: 2019-03-16

Abstract

A modified stuffing box for a wellhead is provided. More particularly, a modified stuffing box having an enlarged bore in its lower section is provided for allowing convenient removal of downhole tools without the need for removing the entire stuffing box from the wellhead.

Description

STUFFING BOX WITH ENLARGED BORE

CROSS REFERENCE AND RELATED APPLICATIONS

[001] This Application claims priority to the United States Provisional Patent Application No. 62/395,809, filed September 16, 2016, which is incorporated by reference in its entirety.

TECHNICAL FIELD

[002] A stuffing box for a wellhead is provided. More particularly, a modified stuffing box having an enlarged central bore is provided.

BACKGROUND

[003] Stuffing boxes are commonly used in the oilfield to create a seal between the wellhead and the well tubulars, such as rod string, passing through the wellhead to drive the downhole pump. Conventional stuffing boxes typically comprise a stationary box portion adapted to receive and create a seal with the moving tubular passing through the box in order to retain fluid pressures and prevent the leakage of wellbore fluids.

[004] Often, the stuffing box is secured around the uppermost rod, referred to as the "polished rod", and is typically attached to a blowout preventer or flow tee to form part of the wellhead stack using a threaded or flanged connection. Over the life of the well, it is likely that the stuffing box will need to be removed in order to permit the removal and repair of downhole tools, such as the pump. Wellbore stack components below the stuffing box are usually not required to be removed, as their bore diameters are large enough to allow equipment such as the pump to pass through. For instance, as disclosed in International Patent Application No. PCT/CA2016/050373, incorporated herein by reference in its entirety, because the bore of the stuffing box must be sealingly engaged with the polished rod, the internal diameter of the bore is required to be similar to the diameter of the polished rod and to support annular packing encircling the rod. Such a diameter is significantly smaller than even the smallest downhole tools, forcing workers to remove the stuffing box in order to access the downhole tools. [005] For stuffing boxes with a threaded connection, each removal of the stuffing box from the wellhead stack causes wear and tear, and carries a risk of damaging the threads of the stuffing box. Excessive wear or damage to the threads would require the entire stuffing box to be replaced due to safety concerns. For stuffing boxes with flanged connections, removal and reinstallation of the stuffing box from the wellhead stack is a laborious and time-consuming process, requiring the removal of a multitude of bolts and re-tightening to specific torque specifications. Repeated removal and remounting of the stuffing box can also cause wear on sealing surfaces.

[006] There is a need for a modified stuffing box adapted for allowing pumps and other downhole tools to be quickly and easily retrieved, while also reducing the likelihood that the stuffing box threads would be damaged when the stuffing box, or a part thereof, is removed.

SUMMARY

[007] According to embodiments herein a modified stuffing box for sealing around a rod for wellbore operations is provided, the stuffing box enabling an upper portion of box to be separated from a lower portion of the box, such that downhole tools may be retrieved from the wellbore, and passed through the lower portion of the box without removal from the wellhead. [008] In some embodiments, the modified stuffing box comprises a tubular housing forming a central bore, and having releasably coupled top, middle, and bottom housings, the top and bottom housings being configured to each contain at least one seal with the central bore to sealingly engage with a reciprocating rod passing through the central bore, the bottom housing being further configured to provide an enlarged bore for passing downhole tools therethrough.

[009] In some embodiments, the central bore of the tubular body may comprise a first internal diameter and at least one second internal diameter, the at least one second diameter being larger than the first, and sized to allow the passage of downhole tools. In other embodiments, the bottom housing may be configured to provide a central bore having at least two internal diameters, both two internal diameters being larger than the first internal diameter. The central bore of the bottom housing may form a first upper bore section and at least one second lower bore section, the upper and lower bore sections having different internal diameters. In one embodiment, the internal diameter of the upper bore section may be larger than the intemal diameter of the lower bore section, the upper bore section being configured to receive at least one second sealing element therein for sealingly engaging the rod. Preferably, both upper and lower bore sections are sized to allow the passage of downhole tools therethrough.

[010] In other embodiments, a method of retrieving at least one downhole tool from a wellbore through a stuffing box operative to sealingly engage at least one rod for wellbore operations positioned within the wellbore, is provided, the method comprising providing a stuffing box having a tubular body with releasably coupled top, middle and bottom housings, the top housing forming a central bore having a first internal diameter for sealingly engaging the rod, the bottom housing forming a central bore having at least one second internal diameter for sealingly engaging the rod and sized to allow the passage of at least one downhole tool therethrough, the at least one second diameter being larger than the first diameter, uncoupling the top and middle housings from the bottom housing, and passing at least one downhole tool through the enlarged bore of the bottom housing.

DESCRIPTION OF THE DRAWINGS

[011] Figure 1 A is a perspective external side view of a stuffing box according to embodiments herein;

[012] Figure IB is a top view of a stuffing box according to embodiments herein. Figures 1A and IB are collectively referred to herein as "Fig. 1";

[013] Figure 2 is a cross section side view along line AA-AA of the stuffing box shown in Fig. IB;

[014] Figure 3 is a detailed cross section view of the top housing of a stuffing box according to embodiments herein;

[015] Figure 4A is a side view of a stuffing box according to embodiments herein; [016] Figure 4B is a cross section bottom view along line E-E of the stuffing box shown in Fig. 4A. Figures 4A and 4B are collectively referred to herein as "Fig. 4";

[017] Figure 5 is a cross section perspective view of an alternative embodiment of the stuffing box according to embodiments herein; [018] Figure 6 is a side cross sectional view of the lower housing of the stuffing boxes disclosed herein;

[019] Figure 7 A is a side cross sectional view of a blow-out preventer having the bottom housing of the present stuffing box incorporated into the top connection of the blow-out preventer; and [020] Figure 7B is a perspective cross sectional view of Figure 7 A. Figures 7 A and 7B are collectively referred to herein as "Fig. 7".

DESCRIPTION OF EMBODIMENTS

[021] According to embodiments herein, a stuffing box is provided for use in a variety of oilfield applications. For example, the stuffing box may be mounted on a wellhead aboveground for sealing with reciprocating wellbore rods driving an underground pump in the well, and particularly the uppermost "polished" rod. Although the present stuffing box is described in connection with reciprocating rods passing through and moving relative to the stuffing box, an alternative embodiment of the present stuffing box may be configured to receive a rotating rod. The present stuffing box may either be pressurized or non-pressurized. The present stuffing box will now be described having regard to Figs. 1 - 7.

[022] Having regard to Fig. 1, a perspective external side view and a top view of one embodiment of a stuffing box 10 are provided for sealingly engaging a wellbore rod (not shown) passing through, and moving relative to, the stuffing box 10. The stuffing box 10 may comprise a tubular body 12 defining a cylindrical passage or central bore 11 along a central axis for receiving the rod.

[023] Body 12 may be adapted to be attached to directly or indirectly to a wellhead (not shown), or to other wellhead componentry such as a blowout preventer (Fig. 7). It should be understood that body 12 may be removably attached to the wellhead via any means known in the art such as threaded engagement, a plurality of radially spaced nut/bolt assemblies etc. The tubular body 12 may comprise coaxially aligned top 14, middle 16 and bottom 18 housing sections, the top housing 14 being releasably coupled to the middle housing 16, and the middle housing 14 being releasably coupled to the bottom housing 18, such that each housing section can be separated one from the other. It should be understood that reference to terms such as "top", "bottom", "up", or "down" etc., are relative terms for explanatory purposes only.

[024] Having regard to Figure 2, top and bottom housings 14, 18 may be releasably connected via an adjuster 20 external to body 12. Adjuster 20 may comprise a plurality of radially spaced connector assemblies 20a received in corresponding apertures 21 of both top and bottom housings 14,18. In operation, adjuster 20 may be activated (e.g. tightened) to simultaneously compress top, middle and bottom housings 14,16,18, sealingly engaging the box 10 with the rod "R" (e.g. via at least two seals housed within the box 10 and described in detail below). Conversely, adjuster 20 may be deactivated (e.g. loosened) to simultaneously decompress top, middle and bottom housings 14,16,18, releasing the sealing engagement between the box 10 and the rod "R"

[025] In one embodiment, adjuster 20 may comprise a plurality of nut and bolt connector assemblies 20a, and preferably four radially spaced nut/bolt connector assemblies 20a. Accordingly, where misalignment of the rod with the bore 11 of the box 10 occurs, each adjuster 20 may be configured to be independently tightened or loosened (depending upon the desire of the operator), serving to adjust the engagement of the box 10 and account for misalignment of the rod.

[026] Having regard to Fig. 3, top housing 14 may be configured to form an upper neck 22, forming bore 11, and a lower flange 24 portion. In some embodiments, flange 24 may be integral to and protrude radially outwardly from the cylindrical neck 22. Flange may have top and bottom surfaces 23,25, respectively. It would be understood that bore 11, formed by neck 22, may have an intemal diameter configured to receive the rod R and any appropriate sealing means (e.g. first seal 40) surrounding and sealingly engaging the rod R. It is contemplated that bore 11 may have a first internal diameter of approximately 2.0 inches. [027] According to embodiments herein, the bottom surface 25 of top housing flange 24 may be adapted to be releasably coupled to middle housing 16 in sealing engagement. For example, bottom surface 25 may comprise a first inner annular groove

26 forming a central downwardly depending cylindrical recess for receiving the top housing 14 in coaxial alignment with the middle housing 16. In one embodiment, top housing 14 may be slidably connected to the middle housing 16. In another embodiment, top housing 14 may be threadably connected to the middle housing 16.

[028] The bottom surface 25 may further provide a second inner annular groove

27 or seat for receiving a first annular seal 28 (e.g. Variseal, TSS Part # DVA30M353- T07HM), preventing fluid leakage between the top housing 14 and the middle housing

16. It is an advantage of the present stuffing box 10 to provide easy removal (e.g.

unthreading and/or lifting) of the top housing 14 from the middle housing 16, enabling a worker to access to the internal components of both top housing 14 and middle housing 16 and simple realignment thereof upon replacement of the top housing 14. [029] As above, top housing 14 may form a plurality of radially spaced apertures 21 for receiving connector assemblies 20a. Apertures 21 may entirely traverse the flange 24 (i.e. extending from top surface 23 through to bottom surface 25).

Apertures 21 may be sized and shaped to correspond to connector assemblies 20a, and preferably may be circular in diameter and sized to receive, for example, a standard connector (e.g. threaded nut).

[030] Having further regard to Fig. 3, the bottom surface 25 of the top housing 14 may further comprise a plurality of radially spaced nesting recesses 29. Recesses 29 may be sized and shaped to correspond to the connector assemblies 20a, such that the top housing 14 may be mounted on and supported by the connector assemblies 20a (e.g. threaded bolts). As such, in operation, connector assemblies 20a (e.g. nuts/bolts) may be loosened off until top housing 14, along with middle housingl6, can be raised upwardly away from bottom housing 18 of the of the box 10 that remain in place, exposing the internal components of the body 12.

[031] Conventionally, in order to maintain or repair the internal components of a stuffing box mounted on a wellhead, the cap of the box must be raised above the worker's head and then clamped to the polished rod, potentially causing damage to the rod and subjecting the worker to significant danger of the cap falling. According to embodiments herein, it is an advantage of the present box 10 that the top and middle housings 14,16 do not need to be clamped to the rod. Instead, the top and middle housing 14,16 may be lifted and rotated around the rod until the recesses 29 coaxially align with the corresponding connector assemblies 20a (e.g. bolts), and then lowered until the recesses 29 of the top housing 14 slidably receive the connectors 20a (e.g. top and middle housings 14,16 are supported by and resting upon the bolts). As such, the present box 10 enables the worker to safely and easily visualize and access the internal components of the box 10, while at the same time enabling the worker to remove or change the internal sealing elements/packing (i.e. for servicing or maintenance of the box 10).

[032] As above, top housing 14 further comprises neck 22. According to embodiments herein, bore 11 of neck 22 may be slightly larger in diameter than the external diameter of the rod, such that at least one first seal 40 may be releasably housed within bore 11 of neck 22. The first seal 40 may comprise a plurality of circumferential hydraulic seals known in the art. Preferably, the first seal 40 comprises a plurality of individually stacked packing rings 42 (for e.g. Chevron^® seals). It is contemplated that the first seal 40 may be any dynamically-sealing packing elements known in the art whereby the compression of the packing rings results in lateral (inward and outward) deformation of the rings, thereby engaging and sealing with the rod within the bore 11. It is further contemplated that packing rings 42 may comprise packing rings having a central aperture offset from central axis, enabling the offset rings to be used during rod misalignment until the rod may be realigned.

[033] The at least one first seal 40 may be retained within the bore 11 of the neck 22. For example, the at least one first seal 40 may be retained in position within neck 22 by annular seal seat formed by shoulder 41, such that packing rings 42 may rest on (and be stacked above) shoulder 41. The first seal 40 may further be retained in position by an annular retainer ring 43 (e.g. annular split-ring). Retainer ring 43 may be manufactured from any suitable materials, such as metal (e.g. brass), or any other such materials as may prevent damage to the rod. [034] In a preferred embodiment, the at least one first seal 40 may effectively be seated at or above the middle housing 16, enabling the first seal 40 to operate as a "backup" seal (e.g. to at least one second seal positioned below the first seal).

[035] The neck 22 of the top housing 14 may further comprise compression means to, in operation, compress the first seal 40, engaging the seal between the packing rings 42 and the rod. In one embodiment, top housing 14 may be adapted to couple with a cap 44. For example, cap 44 may be threaded onto the neck 22 of top housing 14, preventing upward movement of the packing rings 42 and enabling tightening of the threaded engagement to compress both retainer 43 and packing rings 42 in operation. Cap 44 may be easily removed to access retainer 43 and packing rings 42 for repair or replacement.

[036] The middle housing 16 of the body 12 will now be described in more detail. As above, at its upper end, middle housing 16 is configured to couple with the bottom surface 25 of top housing 14. At its lower end, middle housing 16 is further configured to couple to bottom housing 18.

[037] With reference to Figs. 4 and 5, in embodiments herein, middle housing 16 may be sized to effectively contain various valves or other means of closing off the bore 11 to prevent fluids from flowing through the bore to the environment (e.g. a flapper valve 30 or ball closure 130). For example, middle housing 16 may form fluid cavity 46, 146 for containing said valves or other means of closing off bore 11. Middle housing 16, 1 16 may further provide central channel 48 extending downwardly from the cavity 46, 146, the channel 48 being adapted to couple with the bottom housing 18 in sealing engagement. The external surface of channel 48 may comprise annular seal 58 (e.g. o-ring) nested within annular groove or seal seat 59 formed in the external surface of channel 48. The internal diameter of channel 48 may be substantially similar to the diameter of the rod or may increase towards the bottom end of middle housing 16,1 16.

[038] In embodiments herein, lower housing 18 may be substantially conceptually similar in shape to top housing 16, or lower housing 18 may be

substantially different, enabling an enlarged lower bore 60 to be formed therein, the lower bore 60 being configured to allow the passage of downhole tools being retrieved from the wellbore, without requiring the removal of lower housing 18 from the wellhead. [039] According to embodiments herein, having regard to Figs. 2 and 6, bottom housing 18 may be adapted to form upper and lower flanges 54,55, and enlarged central bore 60. Alternatively, lower housing 18 can form neck 52 and lower flange 55 only, as shown in Fig. 2, or neck 52 and upper flange 54 only, as shown in Fig. 5. In some embodiments, the internal diameter of enlarged lower bore 60 may be larger than the internal diameter of bore 11 of upper housing 14, and may be significantly larger than the diameter of rod R. The internal diameter of lower bore 60 may be continuous, or preferably, may be machined to provide at least two varying internal diameters (e.g. increasingly larger from bottom to top of housing 18). [040] For example, in some embodiments bore 60 of bottom housing 18 may form a first upper bore section 67, an enlarged lower bore section 66, and at least one internal annular shoulder 51 therebetween. In some embodiments, bottom housing 18 may be machined to provide for both lower and upper bore 66,67 having internal diameters of at least 2.44" (compared to approximately 2.0" of bore 11), or any other such diameter as may be desired to pass downhole tools therethrough. It would be understood that enlarged upper bore 67, formed by neck 52, may have an internal diameter configured to receive second seal 50 for encircling and sealingly engaging the rod R. As such, in some embodiments, upper bore section 67 is of a greater diameter than lower bore section 66, enabling upper bore section 67 to accommodate at least one second seal 50 therein for sealingly engaging the rod R. It is understood that the internal diameter of annular seal 50 may be equal to or slightly larger than the outer diameter of rod R, enabling seal 50 to sealingly engage the rod R. It should also be understood that both lower and upper bore 66,67 may be further sized to permit downhole tools to pass through the entire bore 60 without removing lower housing 18 from the wellhead or blowout preventer therebelow. It is an advantage of the present stuffing box that only top and middle housing 14,16 (along with retaining device 62, as described herein) need to be removed when extracting downhole tools from the wellbore, rather than the entire stuffing box 10. Enlarged lower bore 66 may also allow the stuffing box 10 to better accommodate for rod misalignment. [041] According to embodiments herein, the at least one second seal 50 may comprise a plurality of circumferential hydraulic seals known in the art. Preferably, the at least one second seal 50 comprises a plurality of individually stacked conical packing rings. It is contemplated that second seal 50 may be any dynamically-sealing packing elements known in the art whereby the compression of the packing ring results in lateral (inward and outward) deformation of the rings, thereby engaging and sealing with the rod within the bores 11,60. In the depicted embodiment, the packing ring is compressed by the forces exerted upon it when middle housing 16 and bottom housing 18 are compressed towards each other by tightening connector assemblies 20a. It is further contemplated that seal 50 (as with at least one first seal 40) may comprise packing rings having a central aperture offset from central axis, enabling the offset rings to be used during rod misalignment until the rod may be realigned. [042] The at least one second seal 50 may be held in position within upper bore section 67 from above by a retainer ring 53 (e.g. annular split-ring). Retainer ring 53 may be manufactured from any suitable materials, such as metal (e.g. brass), or any other such materials as may prevent damage to the rod. The at least one second seal 50 may be retained in position within neck 52 from below by the annular seal seat formed by shoulder 51, and securably retained by retaining device 62, which is in turn retained in position by the annular seat formed by inner shoulder 64, such that seal 50 may rest on (and be stacked above) shoulder 51.

[043] In a preferred embodiment, the at least one second seal 50 may effectively be seated at or below the middle housing 16, enabling the second seal 50 to operate as a "primary" seal, which, in combination with the at least one first seal 40 provides a dual- pack stuffing box 10 system.

[044] Having an enlarged lower bore 66 below shoulder 51 in bottom housing 18 decreases the surface area of shoulder 51, which may negatively affect the ability of the second seal 50 to sealably engage with the rod R and prevent wellbore fluids from travelling above the seal 50. For example, the seal 50 may expand downwards into the enlarged lower bore 66 when energized as opposed to expanding radially inwards to engage with the rod R. To address this, an inner shoulder 64 can be located adjacent to, and axially downhole from, shoulder 51, providing at least one third intemal diameter 68 within the enlarged bore 60. Retaining device 62 can be removably located on inner shoulder 64, and preferably sized such that its height is about equal to the difference between the heights of shoulder 51 and inner shoulder 64, its outer diameter is about equal to the outer diameter of inner shoulder 64, and its inner diameter is about equal to or greater than the diameter of the rod R. Sized as such, the upper surface of retaining device 62 may be generally flush with the upper surface of shoulder 51, forming a flat surface with which the second seal 50 may be seated. Configured as such, retaining device 62 can provide a larger surface area for the seal 50 to engage with when it is energized. The size of the outer diameter of the inner shoulder 64 can vary from at least slightly larger than the diameter of the enlarged lower bore 66 to about the outer diameter of the upper bore 67.

[045] When retrieval of the rod string and pump, or other downhole tools, is desired, the retaining device 62, second seal 50, and retainer ring 53 may be removed along with the top and middle housing 14,16 to allow the rod string and downhole tools to pass unimpeded through the enlarged lower bore 66 and upper bore 67 of the lower housing 18.

[046] It is an advantage of the present stuffing box 10 that a pump, or other downhole tool, may be retrieved by simply removing the top and middle housings 14,16 (along with annular seal 50 and retaining device 62) as opposed to removing the stuffing box in its entirety. When a threaded stuffing box 10 is used, the risk of damaging the threads of the bottom housing 18 is greatly reduced, as the bottom housing 18 can remain connected to the wellhead stack throughout pump retrieval operations. When a flanged connection is used, the rod string and pump can be retrieved by simply unthreading the nuts and bolt connector assemblies 20a rather than removing the typically 8 or more bolts for a flanged connection.

[047] In some embodiments, the modified stuffing box is configured to withstand wellbore pressures of about 5,000 to about 10,000 psi.

[048] As depicted in Figures 7A and 7B, in another embodiment, the bottom housing 18 may be incorporated into the upper connection 72 of a blowout preventer (BOP) 70. In this configuration, the upper connection 72 of the BOP serves as the neck portion 52. A flange portion 54 can be fit onto the neck portion 52, or can be integral with the neck portion 52. Second seal 50, retaining device 62, and other components of the bottom housing 18 can be located within the bottom housing 18 as described above. Middle housing 16 can be coupled with bottom housing 18 and top housing 14, and adjusters 20 can connect top housing 14 with bottom housing 18, in the same manner as described above. It is an advantage of the present embodiment that the total height of the wellhead stack is reduced due to the removal of a connection point, and a potential leak path is eliminated.

[049] In another embodiment, middle housing 16 can be omitted and the body 12 can comprise only top and bottom housings 14,18 sealingly coupled with each other. In this arrangement, central channel 48 can extend downward from the bottom surface 25 of the lower flange 24 of the top housing 14. As above, adjuster 20 may be activated (e.g. tightened) to simultaneously compress top and bottom housings 14,18, sealingly engaging the box 10 with the rod "R". Such a configuration could be used, for example, in applications where no valves or other means of closing off the bore 11 to prevent fluids from flowing through the bore to the environment are desired.

[050] Although a few embodiments have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications can be made to these embodiments without changing or departing from their scope, intent or functionality. The terms and expressions used in the preceding specification have been used herein as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding equivalents of the features shown and described or portions thereof, it being recognized that the invention is defined and limited only by the claims that follow.

Claims

WE CLAIM:

1. A stuffing box for sealing around a rod for wellbore operations, comprising:

a tubular body having releasably coupled top, middle and bottom housings, the middle housing being positionable between and sealingly engageable with the top and bottom housings,

the top housing adapted to contain at least one first seal within the bore for sealingly engaging with the rod,

the bottom housing adapted to contain at least one second seal within the bore for sealingly engaging with the rod,

wherein the top housing forms a central bore having a first internal diameter for receiving the rod, and the bottom housing forms a central bore having at least one second internal diameter for receiving the rod, the at least one second internal diameter being larger than the first internal diameter.

2. The stuffing box according to Claim 1, wherein the bottom housing is configured to provide a central bore having at least two internal diameters, both two internal diameters being larger than the first diameter.

3. The stuffing box according to Claims 1 or 2, wherein the central bore of the bottom housing is sized to allow at least one downhole tool to pass therethrough.

4. The stuffing box according to any one of Claims 1 - 3, wherein the central bore of the bottom housing forms a first upper bore section and a second lower bore section, the upper and lower bore sections having different internal diameters.

5. The stuffing box according to Claim 4, wherein the internal diameter of the upper bore section is larger than the internal diameter of the lower bore section.

6. The stuffing box according to any one of Claims 1 - 5, wherein the first internal diameter is approximately 2.0 inches.

7. The stuffing box according to any one of Claims 1 - 6, wherein the at least one second diameter is approximately at least 2.44 inches.

8. The stuffing box according to any one of Claims 1 - 7, wherein the bottom housing further comprises at least one inner annular shoulder for receiving at least one annular seal for sealingly engaging the rod.

9. The stuffing box according to Claim 8, wherein the bottom housing further comprises at least one second inner annular shoulder for receiving at least one retaining device for securing the annular seal in place.

10. The stuffing box according to any one of Claims 1 - 9, wherein the bottom housing is configured to be incorporated into a blowout preventer.

11. A method of retrieving at least one downhole tool from a wellbore through a stuffing box operative to sealingly engage at least one rod for wellbore operations positioned within the wellbore, the method comprising:

providing a stuffing box having a tubular body with releasably coupled top, middle and bottom housings, the top housing forming a central bore having a first internal diameter for sealingly engaging the rod, the bottom housing forming a central bore having at least one second internal diameter for sealingly engaging the rod and sized to allow the passage of at least one downhole tool therethrough, the at least one second diameter being larger than the first diameter;

uncoupling the top and middle housings from the bottom housing; and passing at least one downhole tool through the enlarged bore of the bottom housing.

12. The method of Claim 11, wherein the method further comprises removing at least one seal from the enlarged central bore.

13. The method of Claim 11 and 12, wherein the method further comprises removing at least one seal retaining device from the enlarged bore.

14. The method of Claim 11, wherein the bottom housing is, at its lower end, connected to the top end of a blowout preventer.