US20040159441A1

US20040159441A1 - Method of and apparatus for dual packing of capillary tubing in a wellhead

Info

Publication number: US20040159441A1
Application number: US10/366,971
Authority: US
Inventors: Robert Heinonen; Timothy Marshall
Original assignee: Double E Inc
Current assignee: DOUBLE-E Inc; Double E Inc
Priority date: 2003-02-13
Filing date: 2003-02-13
Publication date: 2004-08-19

Abstract

A body having a bore thereThrough for insertion of capillary tubing. A first means slidably coupled into the bore of the body frictionally restrains movement of the tubing by hydraulically engaging the periphery of the tubing with a compressible elastomeric sealing member. A second means slidably coupled into the bore of the body prevents movement of the tubing in the bore of the body by manually engaging the periphery of the tubing with a compressible elastomeric sealing member. A third means suspends the tubing in the bore of the body by manually engaging a plurality of suspension slips around the periphery of the tubing.

Description

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to a pack-off method and apparatus for wellheads and, more particularly, but not by way of limitation, to a system for and method of controlling the movement of small diameter tubing into and out of natural gas wells incorporating a dual packing assembly for a more secure long-term sealing in the pack-off head.

2. History of Related Art

A well known practice that is common in the oil and gas industry is to use wellhead devices which will confine pressure in a well around a member such as a polished rod or wireline extending into a well during emergency conditions, as well as when it is necessary for servicing the well. It is well known for example that the production rates from natural gas wells can be adversely affected by corrosion and the buildup of such substances as scale, paraffin and salt. Producers have traditionally treated the wells by inserting chemicals and soap sticks at the wellhead and relying on gravity to carry the treating agent down the well to where it is needed. Recently a much more effective treatment means has been developed. Small diameter tubing is inserted into the well and the treating chemical is pumped down this capillary tubing, usually ¼ or ⅜ inch (sometimes ⅝ inch), under pressure and allowed to enter the well where it can do the most good. A check valve at the lower end of the tubing controls the release of the treating chemical and prevents well pressure from escaping up the capillary tubing.

A service rig is employed to insert or Asnub in@ the capillary tubing while the well remains pressurized. In this way, the service company does not Akill the well@ by pumping water and/or mud into the well casing to build up a hydrostatic pressure head which contains the well pressure. Accordingly, the wellhead must have a means for sealing around the capillary tubing both during insertion or removal from the well and also on a long-term basis while the well is producing with the capillary tubing in place.

In operation, the insertion of the tubing can be problematic and has been analogized to Apushing on a string,@ due to the upward force or thrust within the well. When the weight of the tubing is less than the upward force or thrust in the well due to the pressure therein acting on the tubing, problems can occur. Once a sufficient depth is reached during tube insertion resulting in the weight of the tubing being sufficient to overcome the upward force or thrust, the so-called “balance point” has been crossed. Likewise, when retrieving the tubing, the same phenomenon can occur as the weight of the tubing depending from the wellhead within the well decreases to the point that the weight is not sufficient to overcome the upward force or thrust placed there against.

Although systems are available for controlling the capillary tubing being inserted through a wellhead, problems exist when the tubing is above the balance point as referenced above. Typically, a spool of capillary tubing is disposed adjacent the wellhead in conjunction with a means for guiding the tubing into and through the wellhead. Such spools and guiding mechanisms are powered, and if for some reason, the power unit providing the appropriate power were to fail, the possibility exists that an operator could lose control of the tubing when it is above the balance point. While it is known in the art to use sealing members around the capillary tubing for insertion into the well, problems ensue in securely retaining the tubing within the sealing members while performing the above-referenced operations. Specifically, loss of hydraulic pressure due to a leakage of the hydraulic fluid used to engage the sealing members can weaken the integrity of the sealing mechanism, thereby causing a loss of control of the movement of the capillary tubing.

For the above mentioned reasons, a reliable method of and apparatus for tubing securement is greatly needed, particularly if it could be quickly actuated prior to damage or danger to the operators. The present invention provides a means for quickly regaining control of tubing within a wellhead that has for one reason or the other not been secured by the conventional, compressible pack-off and securing mechanism currently in use. Although slip caps, used in conjunction with manual slips functioning as locking chucks having serrated teeth extending inwardly toward the capillary tubing may be used to permanently secure tubing, such mechanisms, which require manual actuation and/or twisting with a wrench to impart threaded induced movement therefrom, is not feasible and clearly provides safety issues for the operator. It would be a distinct advantage to provide a second redundant sealing mechanism capable of reliable operation in the event of a capillary tubing control problem.

The present invention addresses such problems by utilizing a combination of manual and hydraulic compressible seals in addition to a mechanical locking mechanism capable of withstanding the wellhead pressures.

SUMMARY OF INVENTION

The present invention relates to a dual pack-off method and apparatus for wellheads. More particularly, the present invention relates to a system and method for controlling the movement of small diameter tubing into and out of wells while providing means for preventing the tubing from being blown out of the well. In one aspect, the invention includes a wellhead pack-off system for controlling the movement of small diameter tubing into and out of a well, comprising a body with a bore extending therethrough for insertion of the tubing, hydraulic sealing means slidably coupled into the bore of the body for frictionally restraining vertical movement of the tubing by hydraulically engaging the periphery of the tube with an upper compressible elastomeric sealing member, and manual sealing means slidably coupled into the bore of the body for frictionally restraining upward vertical movement of the tubing in the bore of the body by manually engaging a redundant lower compressible elastomeric sealing member around the periphery of the tubing.

In another aspect of the invention, the body is divided into an upper body, an intermediate body, and a lower body. Further, the upper body is in threaded engagement with the intermediate body, and the intermediate body is in threaded engagement with the lower body. The upper body further comprises a threaded aperture extending through the sidewall thereof. The upper body also comprises the hydraulic sealing means having a plunger in axial alignment with the bore of the body, an upper spring in axial alignment with the plunger, an upper bushing set disposed within the lower end of the plunger, a conically shaped lower bushing set in axial alignment with the upper bushing set, and an upper compressible elastomeric sealing member in axial alignment with the upper and lower bushing set and disposed therebetween. The flow of hydraulic fluid through the first aperture of the upper body imparts a downward force to the plunger, which compresses the spring and forces the upper bushing set into the lower bushing set, thereby compressing the upper sealing member disposed therebetween. The abutting engagement of the upper sealing member and the conically shaped lower bushing set imparts radially inwardly motion to the upper sealing member . The radially inwardly movement of the upper sealing member forms a seal around the capillary tubing extending through the bore of the body.

The intermediate body and the lower body comprise the manual sealing means having a piston in axial alignment with the bore of the body, a lower spring in axial alignment with the piston, a lower flat bushing in axial alignment with the piston, a conical bushing in axial alignment with the lower flat bushing, and a lower compressible elastomeric sealing member in axial alignment with the conical and lower bushing and disposed therebetween. In a manner similar to the actuation of the first means, a nut in threaded engagement with the lower body engages push rods positioned in the lower body and in abutting engagement with the piston. The engagement of the push rods and the piston imparts an upward force to the piston, which compresses the lower spring and forces the lower flat bushing into the conical bushing, thereby compressing the lower sealing member disposed therebetween. The abutting engagement of the lower sealing member and the conical bushing imparts radially inwardly motion to the lower sealing member. The radially inwardly movement of the lower sealing member forms a seal around the capillary tubing extending through the bore of the body.

In still another aspect of the invention, the upper body further comprises suspension means for suspending the tubing by engaging a plurality of suspension slips around the periphery of the tubing. The suspension means further comprises a slip cap in threaded engagement with the upper body for engaging the suspension slips with the tubing.

In a further aspect, the present invention provides a combination of three sealing means, including a hydraulic sealing means for controlling the capillary tubing while is being inserted or removed from the wellhead under pressure, suspension means for suspending the tubing from the wellhead for a prolonged period of time, and manual sealing means for long-term sealing around the capillary tubing. The advantages of providing a redundant manual sealing means are extra safety due to a redundant sealing means, reliability due to mechanical compression of the lower sealing member, and quick and easy adjustment of the manual sealing means.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described in more detail with reference to preferred embodiments of the present invention, given only by way of examples, and illustrated in the accompanying drawings in which: [0015]
FIG. 1 is a perspective view of a typical wellhead installation showing the insertion of capillary tubing; [0016]
FIG. 2 is an enlarged, side-elevational, full cross-sectional view of the capillary tubing pack-off of the present invention with portions thereof cut away for illustrating the assembly thereof; [0017]
FIG. 3 is a side-elevational, full cross-sectional view of the intermediate body of the capillary tubing pack-off of FIG. 2, illustrating one aspect of the fabrication thereof; [0018]
FIG. 4 is a side-elevational, full cross-sectional view of the intermediate cap of the capillary tubing pack-off of FIG. 2, illustrating one aspect of the fabrication thereof; [0019]
FIG. 5 is a side-elevational, full cross-sectional view of the piston for the capillary tubing pack-off of FIG. 2; [0020]
FIG. 6 is a side-elevational, full cross-sectional view of the lower compressible elastomeric sealing member for the capillary tubing pack-off of FIG. 2; [0021]
FIGS. 7A and 7B are top plan and side-elevational, full cross-sectional views, respectively, of the lower bushing for the capillary tubing pack-off of FIG. 2; [0022]
FIG. 8 is a side-elevational, full cross-sectional view of the conical bushing for the capillary tubing pack-off of FIG. 2; [0023]
FIG. 9 is a side-elevational view of the spring for the capillary tubing pack-off of FIG. 2; [0024]
FIG. 10 is a side-elevational view of a push rod for the capillary tubing pack-off of FIG. 2; [0025]
FIG. 11 is a side-elevational, full cross-sectional view of the nut for the capillary tubing pack-off of FIG. 2; and [0026]
FIG. 12 is a side-elevational, full cross-sectional view of the jam nut for the capillary tubing pack-off of FIG. 2.[0027]

DETAILED DESCRIPTION

It has been discovered that a wellhead pack-off incorporating a manual back-up sealing means of the compressible elastomer variety in the configuration set forth and described below may enhance the operational efficiencies surrounding the insertion or removal of capillary tubing into or out of a well under pressure. The manual sealing means of the present invention also provides a means for suspending the capillary tubing from the wellhead for a prolonged period of time. This system feature provides a definite advantage in those instances when the operators wish to hang off the tubing and leave the job site. The wellhead pack-off of the present invention is specifically adapted for providing a reliable, redundant seal that is mechanically compressed in order to provide a reliable, long-term seal of the capillary tubing at the welhead. [0028]
Referring first to FIG. 1, there is shown a typical installation by a service rig [0029] 6 of capillary tubing 7 at a wellhead 8 utilizing a conventional pack-off 9 specifically adapted for the receipt of the capillary tubing therethrough. The wellhead 8 as shown herein utilizes the typical hardware associated with wellheads, including the wellhead pack-off 9 disposed in an upper portion thereof with the capillary string extending therefrom. It is known in the industry to use wellhead pack-off devices for controlling the capillary tubing while the well remains pressurized. As said above, there are many advantages to the utilization of capillary tubing. The well operator's expectations from the use of such tubing includes obtaining incremental increases in production and reserves, and the elimination of production fluctuations associated with soaping, flaring, and stop cocking. The use of capillary tubing also has been shown to reduce downtime and time requirements to maintain production while improving efficiency and effectiveness of chemical treatments and applications. In wells with liquid loading, the benefits of capillary strings include the improvement of system dynamics and minimization of reservoir damage. The present invention facilitates the above advantages by providing a reliable, redundant seal for increasing the reliability of the wellhead pack-off as set forth and described below.
Referring now to FIG. 2, there is shown an enlarged side-elevational, full cross-sectional view of a capillary tubing pack-off [0030] 10 incorporating the principles of the present invention. The presence of a capillary tube is not shown for purposes of clarity. The pack-off 10 includes an upper body portion 11, an intermediate body portion 100, and a lower body portion 170 in axial alignment with the central axis 90. The upper body portion 11 includes a slip cap 12 disposed on the first terminal end 13 thereof, and a plurality of manual upper slips 14 (preferably 3) disposed therein. The upper slips 14 are formed with serrated teeth 15 facing radially inwardly therefrom for engagement of capillary tubing (not shown) extending through the capillary tubing pack-off 10. The upper body portion 11 further comprises a plunger 16 having a threaded portion 17 formed on an upper end 18 thereof and adapted for threadably engaging the slip cap 12 as shown herein. The upper body portion 11 also comprises a cap 20 adapted for receiving the plunger 16 therein in reciprocal mounting relationship therewith. The plunger 16 reciprocates relative to the cap 20 and maintains sealing engagement therewith by virtue of upper and lower o-rings 22 and 24, respectively. The upper o-ring 22 is disposed in an o-ring groove 26 formed in upper end 28 of the cap 20. The lower o-ring 24 is disposed in an o-ring groove 30 formed around middle section 32 of the plunger 16. The o-rings 22 and 24 are preferably sandwiched between back-up rings 34. As referenced herein, the construction and operation of the upper body portion 11, as herein set forth, shown and described, is conventional in the art, as is the use of the aforesaid backup rings and o-rings. For purposes of specificity, the o-rings 22 and 24 of the 90 Duro Nitrile variety have been found acceptable. Likewise, the back-up rings 34 of 90 Duro Nitrile have also been found acceptable.
Still referring to FIG. 2 and, in particular to the [0031] upper body portion 11 of the pack-off 10, a brief description of the construction, assembly, and actuation thereof will be set forth, described and shown for purposes of specificity. As referenced above, the upper body portion 11, as herein described, does not, in and of itself, comprise the inventive aspect of the present invention. A pack-off assembly incorporating the features of the upper body portion 11 shown herein is embodied in a Type CLS Packoff sold by the Assignee of the present invention. In that regard, the cap 20 is constructed with a threaded aperture 36 disposed between the o-rings 22 and 24 for purposes of communicating hydraulic fluid into a cavity 38 defined between the o-rings 22 and 24 and between an inside surface 40 of the cap 20 and an outside surface 42 of the plunger 16. The pressure of hydraulic fluid within the cavity 38 provides a force acting upon the plunger 16 and imparting movement thereto against an upper spring 44 defined in a cavity 46, which is disposed between the cap 20 and the plunger 16. Movement of the plunger 16 in the direction of arrow 50 imparts movement against a steel upper bushing set 52, which is disposed in abutting engagement against upper end 57 of an upper compressible elastomeric sealing member 54. Lower end 56 of the upper sealing member 54 is formed in a conical configuration and lies in abutting engagement with a lower bushing set 58. The upper sealing member 54 is of generally cylindrical construction, having a central bore 55 formed therethrough adapted for receiving the capillary tube axially therein. Compression of the upper sealing member 54 will impart enhanced sealing engagement of said capillary tube (not shown) within said cylindrical bore 55. Such sealing operations are well accepted in the industry. For purposes of specificity, the upper sealing member 54 of the 70 Duro Nitrile variety have been found acceptable. The present invention as described below does, however, provide an advance over the prior art systems by incorporating a second, redundant lower elastomeric sealing member disposed beneath upper elastomeric sealing member 54. The advantages of the manually actuatable redundant lower sealing member will be defined in more detail below.
Still referring to FIG. 2, there is shown, as referenced above, a [0032] central body 99 of the intermediate body section 100. The central body 99 has disposed therein a lower compressible elastomeric sealing member 102 having a central bore 104 formed therethrough and adapted for receiving a capillary tubing therein. The lower sealing member 102 is disposed within a cylindrical cavity 106 formed within the central body 99. Within an upper end 108 of the cavity 106, and on opposite ends thereof, is disposed a conical bushing 110 and a lower flat bushing 112. Between the bushings 110 and 112 is disposed the lower sealing member 102, the compression of which is regulated by a piston 114 bearing against the flat bushing 112. The position of the piston 114 is controlled by a lower spring 116 urging the piston 114 downwardly in a direction 118 from the lower sealing member 102. A plurality of push rods 120 bearing against an underneath side 122 of a outwardly extending hip portion 124 of the piston 114 urge the piston 114 upwardly in a direction 119 toward the lower sealing member 102. The lower spring 116 is defined in a cavity 117 between the inner surface of the cap 134 and the outer surface of the piston 114. The push rods 120 bear against the underneath side 122 and urge the piston 114 upwardly into the flat bushing 112. The push rods 120, of which six are preferably utilized in accordance with the preferred embodiment of the present invention shown herein, (other numerical combinations can be used) are positioned by a nut 126 positioned around a lower base 128 of the cap 134 of pack-off 10 and in threaded engagement therewith. Threads 130 are shown disposed between the lower base 128 and the nut 126, with a jam nut 132 disposed therebeneath also in engagement with threads 130. Finally, it may be seen that the lower spring 116, piston 114 and push rods 120 are all contained within intermediate cap 134 of the intermediate body portion 100. The intermediate cap 134 is in threaded engagement on an upper end 136 to a lower portion 138 of the central body 99 around which threads 140 are formed. The threaded engagement between the lower portion 138 of the central body 99 and the upper end 136 of the intermediate cap 134 is for the securement of the piston 114 axially disposed beneath lower sealing member 102 for the compression thereof.
Referring still to FIG. 2, and more particularly to the [0033] intermediate body portion 100 thereof, the piston 114 includes an axial bore 150 having a diameter larger than that of the capillary tubing which extends through the axial bore 104 of the lower sealing member 102. Likewise, an axial bore 152 is formed in the lower base 128 of the cap 134 therein providing an even greater diameter. To contain the gas or fluid pressure therein, o- rings 154 and 156 are disposed on opposite ends of the piston 114, as shown herein. The o- rings 154 and 156 permit a degree of reciprocal movement of the piston 114 between the central body 99 and the lower base 128 to facilitate the manual adjustment of said piston. Finally, end 160 of the lower base 128 is constructed with threads 162 formed therearound for securement to the wellhead for the operation herein described.
Referring now to FIG. 3, there is shown a side-elevational, full cross-sectional view of the [0034] central body 99 of the intermediate body portion 100 of FIG. 2. All other elements of the capillary pack-off 10 illustrated in FIG. 2 in association therewith have been removed for purposes of clarity. In this particular view, the fabrication of the central body 99 can be more clearly understood as well as certain functional aspects thereof. What is clearly shown herein is a multi-chambered axial bore 300 of the central body 99 facilitating the receipt of the above-referenced elements therein for the operation thereof, and in axial alignment with central axis 90. The bore 300 includes cylindrical cavity 305 and cylindrical cavity 106 oppositely disposed about a cylindrical region 310 sandwiched therebetween. The inside diameter of bore 300 is decreased from the cylindrical cavity 305 to the cylindrical cavity 106, with an inner lip 301 defining the cylindrical region 310, which provides communication between the cylindrical cavity 305 and the upper end 108 of the cylindrical cavity 106. As described above, various bore diameters may be preferable for receipt, adaptation and operation of the various elements described, set forth and shown in FIG. 2.
Still referring to FIG. 3, the lower-[0035] portion 138 of central body 99 is larger in diameter than, and extends from an upper section 330 at an acute angle relative thereto. Furthermore, the lower outer surface of lower portion 138 is provided with threads 140 for threaded engagement with intermediate cap 134. Likewise, the upper outer surface of the section 330 is provided in a threaded configuration 325 for threaded engagement with the cap 20.
Referring now to FIG. 4, there is shown a side-elevational, full cross-sectional view of the [0036] intermediate cap 134, which comprises the upper portion 136 and the lower base 128. The end 160 of the lower base 128 comprises lower body portion 170 of FIG. 2. All other elements of the capillary pack-off 10 illustrated in FIG. 2 in association therewith have been removed for purposes of clarity. In this particular view, the fabrication of the cap 134 can be more clearly understood as well as certain functional aspects thereof. What is clearly shown herein is a multi-chambered axial bore 400 of the cap 134 facilitating the receipt of the above-referenced elements therein for the operation thereof, and in axial alignment with central axis 90. The axial bore 400 includes cylindrical chamber 405 axially aligned with the axial bore 152. The axially aligned chamber 400 and bore 152 are oppositely disposed about a cylindrical region 415 sandwiched therebetween. The inside diameter of the bore 400 is decreased from the chamber 405 to the axial bore 152. The cylindrical region 415 provides communication between the axial bore 152 and the chamber 405 formed upwardly thereof. A plurality of apertures 410 are formed parallel to the central axis 90 in collar 411 of the cap 134 in communication with the chamber 405 for receipt of the plurality of push rods 120, described in further detail below. Furthermore, the collar 411 of the upper portion 136 of the cap 134 abuts and provides a stop for the push rods 120, preventing further movement of the push rods 120. As described above, the various bore diameters are necessitated for receipt, adaptation and operation of the various elements described, set forth and shown in FIG. 2.
Still referring to FIG. 4, the outer surface of [0037] lower base 128 is provided in the threaded configuration 130 for threaded engagement with the nut 126 and the jam nut 132. The end 160 of the lower base 128 is further formed with the threads 162 formed circumferentially therearound adapted for threadably engaging mating wellhead equipment of conventional nature of the types set forth and shown in FIG. 1. Likewise, the sidewalls of the cavity 405 are provided with internal threads 140 for threaded engagement with the lower portion 138 of the central body 99.
Referring now to FIG. 5, there is shown a side-elevational, full cross-sectional view of the [0038] piston 114 of FIG. 2. The central bore 150 is formed concentrically about the axis 90. The piston 114 is formed with the hip portion 124 and an upper portion 505, with an angled surface 506 therebetween extending at an acute angle relative to the upper portion 505. A lower portion 515 extends rearward of the underside 122 of the hip portion 124 . The upper portion 505 and the lower portion 515 are adapted to receive the o- rings 156 and 154 in o- ring slots 556 and 554, respectively. The upper portion 505 further includes a terminal end 520 abutting the lower sealing member 102. The actuation of the piston 114 within the capillary tubing pack-off 10 will be described in more detail below.
Referring to FIG. 6, there is shown a side-elevational, full cross-sectional view of the [0039] lower sealing member 102. The central bore 104 is formed concentrically about the axis 90. The lower sealing member 102 includes an upper angulated surface 600 in abutting engagement with the conical busing 110, and a lower surface 605 in abutting engagement with the lower bushing 112. As discussed below, the lower sealing member 102 frictionally restrains movement of the capillary tubing (not shown) extending through central bore 104 by forming a seal around the circumference of the capillary tubing in reaction to a force imparted by the piston 114.
Referring now to FIGS. 7A and 7B in combination, there is shown a top plan and a side-elevational view of [0040] lower bushing 112. The central bore 104 is formed concentrically about the axis 90. The low bushing 112 further comprises chamfered edges 712 and 714. Furthermore, the lower flat bushing 112 includes a top surface 710 abutting the lower surface 605 of the lower sealing member 102 and a lower surface 705 abutting the upper terminal end 520 of the piston 114.
Still referring to FIGS. 7A and 7B in combination, there is shown below the plane of the lower surface [0041] 705 a plurality of grooves 701. The grooves 701 allow well pressure to reach the outer perimeter of end 520 of piston 114. This allows pressure to act over the entire area of end 520, so that piston 114 is pressure balanced. If the piston 114 is pressure balanced, the spring 116 can force the piston 114 downwards to relax the compression of the lower sealing member 102 when it is time to pull the tubing our of the well for servicing.
Referring now to FIG. 8, there is shown a side-elevational, full cross-sectional view of the [0042] conical bushing 110, having the central bore 104 formed concencentrically about the axis 90. The central bore 104 is in communication with the cylindrical region 310 of the central body 99. The conical bushing 110 is contained in the upper portion 108 of the cylindrical cavity 106 of the central body 99 The conical bushing 110 includes a conically-shaped lower surface 805 in abutting engagement with the upper angulated surface 600 of lower sealing member 102, and a flat upper surface 810 in abutting engagement with the lower portion of the lip 301 of the central body 99. The function of conical bushing 110 will be discussed in more detail below.
Referring to FIG. 9, there is shown a side-elevational view of the [0043] lower spring 116. The spring 116 includes a central bore 900 in axial alignment with central axis 90, and is defined in the cavity 117. The spring 116 comprises a top surface 910 abutting the lower surface 350 of the lower portion 138 of the central body 99 and a bottom surface 905 in abutting engagement with the topside of the hip portion 124 of the piston 114. The function of the spring 116 will be discussed in more detail below.
Referring now to FIG. 10, there is shown a side-elevational view of one of the plurality of push rods [0044] 120 (preferably 6). The push rods 120 include a first end 915 abutting the underside 122 of the hip 124 of the piston 114, and a surface 916 abutting the collar 411 of the sidewall of cylindrical chamber 405, as shown in FIG. 4. The push rods 120 further include a body portion 919 which extend through the aperture 410, as shown in FIG. 4, and abut the nut 126 at a lower end 917.
Referring now to FIG. 11, there is shown a side-elevational, full cross-sectional view of [0045] nut 126. The nut 126 includes a central bore 940 in axial alignment with central axis 90. The sidewalls of bore 940 include threads 951 for threaded engagement with the threads 130 of the lower base 128 of the cap 134. The nut 126 further includes a top side 942 abutting the lower end 917 of the push rods 120, and an underside 941 abutting the jam nut 132. The outer surface 943 of the nut 126 is provided in a knurled configuration for facilitating engagement of the threads 951 with the threads 130 of the lower base 128. As discussed below, the nut 126 of the present invention provides the mechanical actuation of piston 114 which imparts an upward force to lower sealing member 102 to frictionally restrain the 'capillary tubing extending along the axis 90 through central bore 940.
Referring to FIG. 12, there is shown a side-elevational, full cross-sectional view of the [0046] jam nut 132. The jam nut 132 includes a central bore 950 in axial alignment with central axis 90. The sidewalls of bore 950 are provided in a threaded configuration 954 for threaded engagement with the threads 130 of the lower base 128. The outer surface 953 of the jam nut 132 is provided in a knurled configuration for facilitating engagement of the threads 954 with the threads 130 of the lower base 128. A top surface 952 abuts the lower end 941 of nut 126. As further described below, the jam nut 132 prevents slippage between the threads 954 of the nut 126 and the threads 130 of the lower base 128.
In operation, the redundant pack-off assembly of the pack-[0047] off assembly 10 of the present invention utilizes two temporary pack-off, sealing and securing systems for controlling the capillary tubing extending through capillary pack-off 10. While the upper body portion 11 facilitates the hydraulic actuated sealing of a capillary tube, the intermediate body portion 100 provides a redundant seal.
During the snubbing operation, the [0048] upper body portion 11 is regulated by the flow of hydraulic fluid through the aperture 36 from a hand pump or from a pump on a rig. The hydraulic pressure causes the plunger 16 to apply a variable compressive load to the upper sealing member 54. The flow of hydraulic fluid through the aperture 36 of the upper body portion 11 imparts a downward force to the plunger 16, which compresses the upper spring 44 and forces the upper bushing set 52 into the lower bushing set 58, thereby compressing the upper sealing member 54 disposed therebetween. The abutting engagement of the upper sealing member 54 and the conically shaped lower bushing set 58 imparts radially inwardly motion to the upper sealing member 54. The radially inwardly movement of the upper sealing member 54 forms a seal around the capillary tubing extending through the pack-off 10 of the present invention, thus frictionally restraining movement thereof.
The [0049] intermediate body 100 comprises the redundant, lower compressible sealing member 102. The lower sealing member 102 is, as described above, mechanically compressed via the nut 126 in order to provide a longer term seal than that potentially provided by the upper sealing member 54 of the upper body portion 11. The jam nut 132 prevents the nut 126 from coming loose and releasing the lower compressible member 102. In a manner similar to the actuation of the upper sealing member 54, the nut 126 in threaded engagement with the lower base 128 of cap 134 engages the push rods 120 positioned in the collar 411 of the cap 134 and in abutting engagement with the piston 114. The engagement of the push rods 120 by the nut 126 imparts an upward force to the piston 114, which compresses the lower spring 116 and forces the lower flat bushing 112 into the conical bushing 110, thereby compressing the lower sealing member 102 disposed therebetween. The abutting engagement of the lower sealing member 102 and the conical bushing 110 imparts radially inwardly motion to the lower sealing member 102. The radially inwardly movement of the lower sealing member 102 forms a seal around the capillary tubing extending through the pack-off 10 of the present invention, thus frictionally restraining movement thereof.
As described above, any leak of hydraulic fluid from the [0050] upper body portion 11 can compromise the integrity of the securing and sealing mechanism of the upper compressible elastomeric sealing member 54. By utilizing the redundant, mechanically actuatable lower compressible elastomeric sealing member 102, operators at the wellhead can egress from the job site and have a much higher level of confidence of the integrity of the pack-off unit 10 of the present invention because they will be relying upon a mechanical, long term sealing system which inherently has greater reliability and is not subject to potential pressure loss. Moreover, if the upper sealing member 54 exhibits any leaking, it is quick and easy to snug the lower sealing member 102 by rotation of the nut 126 to stop a leak. Such actuation can occur manually without having to bring in an additional pump and/or going through any more complex procedures than a simple rotation of a threaded member. The advantages of providing a redundant manual sealing means are extra safety due to a redundant sealing means, reliability due to mechanical compression of the lower sealing member, and quick and easy adjustment of the manual sealing means.
Furthermore, when lowering tubing into the well or pulling tubing out of the well, the manual upper slips [0051] 14 described above which are actuated by the slip cap 12 are typically not in place on the capillary tubing pack-off 10 of the present invention. The slips 14 are placed into the upper end 18 after the desired amount of tubing has been inserted into the well. What is in place is the hydraulic actuation of the upper sealing member 54 and the manual actuation of the lower sealing member 102 as discussed above which permits sealing and securement of the capillary tube as long as the pressures within the well do not exceed that capable of being handled by such compressible members. Due to the fact that the upper and lower sealing members 54 and 102 are, however, elastomeric, it includes a relatively smooth surface for creating an effective seal thereagainst to prevent fluids from within the well to escape therefrom.
It should be noted that the specification of the o-rings presented herein are for purposes of illustrating the requirement for sealing, as is typical in most hydraulic actuation systems due to the high pressures involved in the system, the multiple use of o-rings is deemed a preferred embodiment. [0052]
Although a preferred embodiment of the invention as been illustrated in the accompanying drawings and described in the foregoing specification, the wellhead is capable of numerous rearrangements and modifications of parts and elements without departing from the spirit of the invention. [0053]

Claims

We claim:

1. A wellhead pack-off system for controlling the movement of small diameter tubing into and out of a well, comprising:

a body having a bore therethrough for insertion of said tubing;

first means slidably coupled into said bore of said body for frictionally restraining movement of said tubing by hydraulicly engaging the periphery of said tubing with an upper compressible elastomeric sealing member; and

second means slidably coupled into said bore of said body for frictionally restraining movement of said tubing by manually engaging the periphery of said tubing with a lower compressible elastomeric sealing member to impart select engagement or disengagement of the periphery of said tubing for its securement therein.

2. The wellhead pack-off system of claim 1, wherein the body further comprises:

an upper body portion having a cap portion in threaded engagement with said intermediate portion , and having said bore therethrough, said cap portion having an aperture formed therein and extending therethrough;

an intermediate body portion in threaded engagement to said upper body portion and having said bore therethrough and having an intermediate cap portion; and

a lower body portion;

wherein said first means is operable in said upper body, and said second means is operable in said intermediate body.

3. The wellhead pack-off system of claim 2, wherein said first means comprises:

a plunger axially disposed within said cap having a reduced neck portion forming a first cavity between said plunger and said sidewall of said cap, and having a lower end and an upper boss forming a second cavity between the opening of said aperture of said cap and said first cavity;

an upper spring disposed within said first cavity for purposes of the flexing thereof and urging movement against said plunger;

an upper bushing set disposed within the lower end of said plunger, said upper bushing set having a first side abutting the terminal end of said plunger and a second side;

a lower bushing set disposed in and in alignment with said intermediate portion, and having an angulated surface; and

an upper sealing member disposed in axial alignment with said upper bushing and within the walls of said intermediate portion, and having an angulated surface in abutting relationship with the angulated surface of said lower bushing set and an opposite surface in abutting relationship with said second side of said upper bushing set.

4. The wellhead pack-off system of claim 3, wherein said first means is operable to hydraulicly compress said upper sealing member to seal said tubing extending through said bore of said body.

5. The wellhead pack-off system of claim 4, wherein said upper sealing member is compressed by the exertion of an axial force on said surface in abutting relationship with said second side of said upper bushing set by said plunger, whereby said axial force in combination with said angulated surface of said upper sealing member in abutting relationship with the angulated surface of said lower bushing set causes said compressible member to form a seal against said tubing, thereby frictionally restraining the movement of said tubing through said bore.

6. The wellhead pack-off system of claim 5, wherein said second means comprises:

a piston axially disposed within said intermediate cap, said piston having an upper reduced neck portion forming a cavity between said piston and said sidewall of said intermediate cap, and having a lower hip portion;

a spring disposed within said cavity for purposes of the flexing thereof and urging movement against said piston;

a lower flat bushing disposed in and in alignment with said intermediate portion and in abutting engagement with the upper terminal end of said plunger, and having a second side;

a conical bushing disposed in and in alignment with said intermediate portion, and having an angulated surface and an opposite surface in abutting engagement with said intermediate portion;

a lower sealing member disposed in axial alignment with and abutting said lower flat bushing and within the walls of said intermediate portion, and having an angulated surface in abutting relationship with said angulated surface of said conical bushing and an opposite surface in abutting relationship with said second side of said lower flat bushing; and

mechanical means for urging said piston upwardly into said flat bushing, thereby compressing said lower sealing member around said tubing and forming a seal therearound.

7. The wellhead pack-off system of claim 6, wherein said mechanical means comprises:

a nut in threaded engagement with said lower body; and

a plurality of push rods having an upper end bearing against the underneath side of said hip portion of said piston, and a lower end bearing against the upper surface of said nut, and wherein said plurality of push rods extend through apertures extending through the intermediate cap portion.

8. The wellhead pack-off system of claim 7, wherein said second means is operable to mechanically compress said lower sealing member to seal said tubing extending through said bore of said body.

9. The wellhead pack-off system of claim 8, wherein said lower sealing member is compressed by the exertion of an axial force on said surface of said lower sealing member in abutting relationship with said second side of said lower flat bushing by said piston, whereby said axial force in combination with said angulated surface of said lower sealing member in abutting relationship with the angulated surface of said conical bushing forces said lower sealing member to form a seal against said tubing, thereby frictionally restraining the movement of said tubing through said bore.

10. The wellhead pack-off system of claim 9, wherein said nut positions said piston by exerting an axial force against the underside of said plurality of push rods, thereby forcing said piston to impart an axial movement to said flat bushing.

11. The wellhead pack-off system of claim 10, further comprising a jam nut in threaded engagement with said lower body, wherein said jam nut prevents slippage of said nut in threaded engagement with said lower body.

12. The wellhead pack-off system of claim 11, wherein said upper body further comprises a first conical section in communication with said bore extending through said piston.

13. The wellhead pack-off system of claim 12, further comprising a third means for suspending said tubing by engaging a plurality of suspension slips around the periphery of said tubing.

14. The wellhead pack-off system of claim 13, wherein said first conical section comprises a sidewall engaging said plurality of suspension slips is adapted for receiving said plurality of suspension slips.

15. The wellhead pack-off system of claim 14, wherein said third means further comprises a slip cap in threaded engagement with said upper body for engaging said suspension slips with said tubing.

16. A method for controlling the movement of small diameter tubing into and out of a well, comprising the steps of:

inserting said tubing into a body having a bore therethrough;

hydraulically engaging the periphery of said tube with an upper compressible elastomeric sealing member to frictionally restraining movement of said tubing; and

manually engaging the periphery of said tube with a lower compressible elastomeric sealing member frictionally restraining movement of said tubing

17. The method according to claim 16, wherein the step of manually engaging further comprises the step manually engaging a piston so as to compress said lower sealing member, thereby forming a seal around the periphery of said tubing and frictionally restraining movement of said tubing..

17. The method according to claim 16, wherein the step of manually engaging said piston comprises the steps of:

placing a plurality of push rods in contact with said piston; and

threadably engaging a nut to the lower end of said body so as to cause contact between said nut and said push rods, wherein axial motion of said nut imparts axial motion to said piston.

18. The method according to claim 17, further comprising the step of preventing slippage of said nut in threaded engagement with the lower end of said body by threadably engaging a jam nut to the lower end of said body, said jam nut abutting the underside of said nut.

19. The method according to claim 18, wherein the step of frictionally restraining movement of said tubing by hydraulically engaging the periphery of said tube with an compressible elastomeric sealing member comprises the step of hydraulically engaging a plunger so as to compress said sealing member, thereby forming a seal around the periphery of said tubing and frictionally restraining movement of said tubing.

20. The method according to claim 19, further comprising the step of suspending said tubing in said bore of said body by manually engaging a plurality of suspension slips around the periphery of said tubing.