US2994379A

US2994379A - Bleed-off assembly for well pipes

Info

Publication number: US2994379A
Application number: US723251A
Authority: US
Inventors: Cicero C Brown; Virgil D Stone
Original assignee: BROWN
Current assignee: BROWN
Priority date: 1958-03-24
Filing date: 1958-03-24
Publication date: 1961-08-01
Anticipated expiration: 1978-08-01

Description

Aug. 1, 1961 c. c. BROWN ET AL 2,994,379

BLEED-OFF ASSEMBLY FOR WELL PIPES Filed March 24, 1958 C/cero C. Brow V/ry// 17. Jz0/7e INVENTORS ATTORNEY 2,994,379 BLEED-OFF ASSEMBLY FOR WELL PIPES Cicero C. Brown, Brown Oil Tools, Inc., R0. Box 19236, Houston, Tex., and Virgil 1). Stone, Morgan City, La.; said Stone assignor to said Brown Filed Mar. 24, 1958, Ser. No. 723,251 12 Claims. (Cl. 166-81) This invention relates to well apparatus and particularly to a device referred to as a bleed-01f assembly for well pipes by which pressure entrapped in a well pipe may be safely discharged when the sections of the pipe are uncoupled.

In operation of oil and gas wells which produce through tubing extending into a well through a larger diameter casing, it frequently becomes necessary in the operation of the well to pull the tubing string for purposes of repair or replacement, or for conducting work in the well bore. Frequently in such wells, particularly where the pressures of the fluids in the earth formations are high, considerable danger to those working about the well may occur by reason of the entrapment of gas or oil under high pressure in the tubing string, which will be suddenly released upon disconnecting the sections of the tubing string as it is being withdrawn from the well.

Entrapment may occur because of plugging of the tubing by deposits of paraflin, sand, other solid matter, or mixtures of these materials, which may form bridges or plugs in the bore of the tubing against which formation gas may be compressed, either by reason of the pressure I in the earth formations with which the tubing was in communication, or by the hydrostatic pressure of fluid in the surrounding casing which, as the tubing string is being pulled upwardly, may flow into the bottom of the tubing string and by differential pressure compress gas trapped in the tubing string below the plug. As the tubing string containing gas trapped in this manner and under high pressure is drawn to the surface and the coupling below the plug is broken, as by unscrewing the upper joint of tubing, the entrapped high pressure gas will blow out under great force and, as indicated, with serious hazards to workmen in the vicinity.

The present invention has for its principal object the provision of a tool structure, referred to as a bleed-off assembly, which will obviate the hazards above described.

Essentially, the bleed-01f assembly comprises a tubular body adapted to be secured to the wellhead about the tubing string and through which the tubing string may be drawn as it is pulled from the well. The body is provided with longitudinally spaced seal means adapted to form fluid-tight seals between the tubing string and the body above and below the joints in the pipe string as each of the latter is drawn from the well. The assembly includes slips or other releasable anchor means for supporting the pipe string below the joint against downward movement, and a second anchor means or set of slips mounted on the upper end of the body for engaging the pipe string section above the coupling to prevent its being blown upwardly from the tool when the section is released from the coupling. The seal means provided in the bleed-off body are of a resilient contracting type adapted to be compressed by pressure existing in the space between the seal means into tight-sealing engagement between the tubing and the bleed-off body. A slip joint is provided between the upper anchor means and the body to permit limited axial movement between these elements to accommodate unscrewing or uncoupling of the upper pipe section from the tubing string.

Other and more specific objects and advantages of this invention will become more readily apparent from the following detailed description when read in conjunction with the accompanying drawing which illustrates one useful embodiment in accordance with this invention. 1

Fatented Aug. 1, 1961 In the drawing:

FIG. 1 is a generally diagrammatic view showing the bleed-olf assembly positioned at the top of a well, and showing a tubing string being drawn therethrough by conventional hoisting equipment;

FIG. 2 is a view, partly in elevation and partly in section, of the bleed-off assembly proper.

Referring to the drawing and to FIG. 2 in particular, the bleed-off assembly comprises a generally tubular body 10 having bore 11 and provided with

opposite side connections

12 and 13. A pressure gauge 14 is shown connected to connection 12 and a branch pipe 15, fitted with a control valve 16, is secured to connection 13 for bleeding-elf fluid from the interior of body 10. Positioned interiorly of bore 11 near opposite ends of body 10 are a pair of seal units, each designated generally by the numeral 17, the units being longitudinally spaced sufficiently to accommodate between them the screw collar or coupling 18 connecting upper and

lower sections

19 and 20, respectively, of a tubing string, designated generally by the letter T, the latter being shown extending through the bore 11 of the assembly. The lower end of body 11 carries a base structure, designated generally by the numeral 21, which comprises an upper plate 22 having an axial opening 23 into which the lower end of body 10 is extended and secured by means of threads 24!. A lower plate 25 is secured in spaced relation to upper plate 22 by means of spacer bolts 26 to provide a working space 27 between plates 22 and 25. Lower plate 25 is of non-round configuration, being generally of square form, for reception in a correspondingly shaped opening 0 in a wellhead fitting W (FIG. 1) mounted on top of the well from which tubing string T is withdrawn. Wellhead fitting W may be a conventional rotary table having the square or non-round opening 0 for reception of a conventional slip bowl and tubing slips. Lower plate 25 is provided with a central opening 28 of downwardly tapering generally conical shape adapted to receive a set of pipe-gripping wedges or slips 29, of generally conventional form, having upwardly facing buttress teeth 30 on their pipe-engaging faces adapted, when the slips are seated in opening 28, to grip the surface of pipe section 29 and prevent the latter from dropping downwardly through the well. Opening 28 constitutes a slip bowl for the slips 2.9.

A tubular cap 31 is screwed into the upper end of body 10 and is provided with an axial opening 32 in the top thereof, the undersurface of the top of cap 31 defining a downwardly facing annular shoulder 33 spaced from the lower end of cap 31. A sleeve member 34 extends through opening 32 and is provided at its inner or lower end with an outwardly projecting flange 35, the outer edge of which is slidably engageable with the inner wall of cap 31. A resilient shock absorber ring 36 is mounted about the exterior of sleeve member 34 just above flange 35. The upper end of sleeve 34, which projects above cap 31, is externally threaded at 37 to receive a tubular head 38 having internal thread 39 at its lower end engageable with threads 37. Thus sleeve 34 may slide axially relative to body 10 a distance corresponding to the spacing between lip 33 and flange less the thickness of ring 36. The upper portion of head 33 has its inner wall tapered upwardly and inwardly to form a slip bowl or wedge seat 41) for engagement by wedge-shaped slips &1 having downwardly facing buttress teeth 12 on their inner faces adapted to engage the exterior of pipe section 19 to prevent the latter from being forced outwardly from the interior of the assembly by internal pressures, as will be more fully described hereinafter. Slips 41 aresecured at their larger (lower) ends to a spacer collar 43 by means of studs 44, the

lower end of collar 43 being in abutting engagement with 3 the upper end of sleeve 34. Radially extending handles 45 are secured to the upper portion of sleeve 34 for rotating the latter, and a similar pair of operating handles 46 are secured to head 38 for rotating this element.

The seal units 17 are identical in construction and each of these seal units constitutes a device commonly known as a tubing stripper and may be of any suitable or well-known construction commonly employed in such tubing strippers. However, the particular embodiment illustrated herein is of the improved construction illustrated and described in the: copending application of Cicero C. Brown, Serial No. 708,170, filed January 10, 1958.

Each seal unit 17 comprises a sealing sleeve 50 constructed of flexible resilient material and mounted about a tubular body 51 which has one end extending into the interior of sleeve 50. The end portion of sleeve 50, which surrounds body 51, is secured to a support ring 52 which abuts a radially outwardly extending annular flange 53 formed on the outer end of body 51. Support ring 52 has a packing or seal ring 54 mounted in its outer surface adapted to sealingly engage the wall of bore 11. The free end of sealing sleeve Sill is turned inwardly and thickened to form lip 55 having the inwardly sloping inner and outer faces 56 and 57, respectively, these faces being joined by an outwardly flaring face 58. The configuration of lip 55 provides an axial bore 59 therethrough which has a normal diameter such as to frictionally engage the exterior of pipe string T, and by reason of its resilient character may be resiliently expanded by enlargements on the pipe strings, such as the upset portions of the tubing string and collars 18, when the tubing string is drawn through the sealing sleeve. The inner end of body 51 extending into the bore of sealing sleeve 50 is provided with a plurality of complementary segmental pawls or dogs 60 which are circumferentially secured to the inner end of body 51 and mounted for radial movement relative thereto by means of T-heads 61 received in correspondingly shaped T-slots 62 formed in the inner margin of body 51. Pawls 60, provide internal support for lip 55 to prevent destructive extrusion and distortion of lip 55 and the sealing sleeve when under the high pressure which may develop interiorly of body 10. The form of sealing sleeve 50 is such that the greater the pressure in body the tighter will be the seal formed about the tubing string by the sealing sleeve, while packing 54 completes the seal between the tubing string and body 10.

The upper one of the sealing units 17 is retained in its upper position by means of an upwardly facing annular shoulder 64 provided in the wall of bore 11 which engages beneath collar 52. Flange 53 thereby forms a lower limit stop for sleeve 34, and the upper sealing unit is held against upward displacement by a downwardly facing annular shoulder 65 which engages the inner end of collar 52 and the lower seal unit is retained against downward movement by its engagement with upper plate 22 of the base structure 21.

The above-described device is employed in the following manner: The assembly, with head 38 and slips 41 removed, will be slipped over the upper end of the tubing string while the latter is held in position by the usual tubing slips mounted in wellhead fitting W, which, as noted previously, may be a conventional rotary table, and the supporting slips comprising the usual tubing slips are fitted in a conventional slip bowl (not shown) mounted in opening 0. Elevator 65a, suspended from a conventional travelling block 66, will be lowered around tubing T below the uppermost collar 18a, and the tubing string will then be lifted sufficiently to permit removal of the conventional slip bowl and slips from wellhead fitting W, thereupon the assembly 10 will be lowered sufiiciently to fit lower plate in opening 0, and slips 29 will be dropped into place in opening 28 to grip the pipe string so that elevator a may be detached from the tubing string and the tubing string weight will then be fully supported on slips 29. Thereupon head 38 and slips 4-1 will be slipped over the upper end of the tubing string and, by means of handles 46, head 38 will be screwed down over threads 37 on the upper end of sleeve 34. Head 38 may thus be screwed down sufli ciently to drive slips 41 into wedging engagement with tubing string T, and thereby hold the upper section of the tubing string against upward movement relative to the head. At this stage of operations, sleeve 34 will be in its lowermost position illustrated in FIG. 2.

However, before slips 41 are brought into tight gripping engagement with tubing string T, elevator 65a will be reattached to the top of the tubing string and will be caused to lift the string sufliciently to draw the collar 18, which connects the pipe section to be broken out of the string, into the interior of body 10 between sealing units 17. Slips 29 will have been removed temporarily while this movement occurs and will then be dropped back into gripping engagement with the tubing string when the collar 18 is inside the body, as noted. Head 38 will then be screwed down on the upper end of sleeve 34 until slips 41 grippingly engage the upper section 19 of the tubing string. Thereupon conventional pipe tongs are applied in the usual manner to the portion of the tubing string extending above the assembly in order to unscrew upper tubing section 19 from collar 18, the non-round lower plate 25 and slips 29 acting as a back-up wrench for the lower section 20 of the tubing string during this operation. As upper section 19 is thus unscrewed from collar 18, it will necessarily move upwardly and since it is gripped by the 'wedging action of slips 41 in head 38, the latter will be caused to move upwardly and draw sleeve 34 upwardly as upper pipe section 19 is elevated by the unscrewing movement. Sleeve 34 and cap 31 thus form a slip joint between body 10 and head 38 which permits relative upward movement of the latter corresponding to the unscrewing of the pipe section, as well as rotational movement of head 38 and sleeve 34 relative to body 10. Before unscrewing of upper tubing section 19 is begun, valve 15 will be closed and when the joint between upper tubing section 19 and collar 18 is broken sufficiently, any gas or other fluid trapped in the tubing will flow into the interior of body 10 and its pressure will be indicated on gauge 14. If substantial pressure is so indicated, valve 16 will be opened to relieve this pressure through pipe 15 and uncontrolled escape of pressure from the interior of the tubing will thus be prevented, the fluid escaping from the unscrewed joint being confined in body 10 between seal units 17 and will be channeled away from the wellhead through pipe 15. Of course, if the joint is broken and no pressure appears on gauge 14, it will be evident that there is no fluid trapped under pressure, at least in that particular section of the tubing.

The described operation will be repeated for each section of tubing broken out of the string until the entire string is withdrawn, after which the assembly may be removed from the wellhead and further operations in the well conducted in the usual manner.

It will be seen that when pressure fluid released from the tubing enters bore 11, this pressure will be exerted against the opposing sealing units and will act against lips 55 to compress them tightly about the upper and

lower pipe sections

19 and 20, respectively, and with packings 54 which engage the wall of body 10, will effectively confine the fluid pressure inside the body until controllably released through valve 16, so that a hazard to the operators will be obviated.

It will be understood that various modifications and changes may be made in the details of the illustrative embodiment within the scope of the appended claims but without departing from the spirit of this invention.

What we claim and desire to secure by Letters Patent is:

1. A pressure bleed-off assembly for a pipe string being Withdrawn from a well, comprising, a generally tubular body mountable on a wellhead about said pipe string, means carried by the body for non-rotatably seeming the body to said wellhead, a pair of annular re silient sealing units mounted in the bore of the body to form longitudinally spaced circumferential seals between the body and pipe string sections on opposite sides of a coupling joining said sections, spaced anchor means carried by the body for releasably securing the body to the respective pipe string sections at points respectively above and below said sealing units, a rotatable longitudinally slidable connection means between and connecting the upper one of said anchor means and the body, and a fluid passage through the wall of the body intermediate said sealing units.

2. A pressure bleed-off assembly for a pipe string being withdrawn from a well, comprising, a generally tubular body mountable on a wellhead about said pipe string, means carried by the body for non-rotatably securing the body to said wellhead, a pair of annular resilient sealing units mounted in the bore of the body to form longitudinally spaced circumferential seals between the body and pipe string sections on opposite sides of a coupling joining said sections, spaced anchor means carried by the body for releasably securing the body to the respective pipe string sections at points respectively above and below said sealing units, a rotatable longitudinally slidable connection means between and connecting the upper one of said anchor means and the body, said connection means comprising a tubular sleeve member slidably disposed in the bore of the body, means limiting the relative longitudinal movement between the sleeve and the body, and a fluid passage through the wall of the body intermediate said sealing units.

3. A pressure bleed-ofl assembly for a pipe string being withdrawn from a well, comprising, a generally tubular body mountable on a wellhead about said pipe string, a base member carried by one end of the body and adapted to form a nonrotatable connection to the wellhead, a pair of annular resilient sealing units mounted in the bore of the body to form longitudinally spaced circumferential seals between the body and pipe string sections on opposite sides of a coupling joining said sections, spaced anchor means carried by the body for releasably securing the body to the respective pipe string sections at points respectively above and below said sealing units, the lower one of said anchor means being positioned in said base member, a rotatable longitudinally slidable connection means between and connecting the upper one of said anchor means and the body, and a fluid passage through the wall of the body intermediate said sealing units.

4. A pressure bleed-oil? assembly for a pipe string being withdrawn from a well, comprising, a generally tubular body mountable on a wellhead about said pipe string, a base member carried by one end of the body and adapted to form a non-rotatable connection to the wellhead, a pair of annular resilient sealing units mounted in the bore of the body to form longitudinally spaced circumferential seals between the body and pipe string sections on opposite sides of a coupling joining said sections, spaced anchor means carried by the body for releasably securing the body to the respective pipe string sections at points respectively above and below said sealing units, the lower one of said anchor means being positioned in said base member, a rotatable longitudinal slidable connection means between and connecting the upper one of said anchor means and the body, said connection means comprising a tubular sleeve member slidably and rotatably disposed in the bore of the body, means limiting relative longitudinal movement between the sleeve and the body, and a fluid passage through the wall of the body intermediate said sealing units.

5. A pressure bleed-01f assembly for a pipe string being Withdrawn from a well, comprising, a generally tubular body vertically mountable on a wellhead about said pipe string, a base member carried by the lower end of the body and forming a non-rotatable connection to the wellhead, a pair of annular resilient sealing units mounted in the bore of the body to form longitudinally spaced circumferential seals between the body and pipe string sections on opposite sides of a coupling joining said sections, upper and lower spaced anchor means carried by the body for releasably securing the body to the respective pipe string sections at points respectively above and below said sealing units, each of said anchor means comprising a slip bowl having a conically tapered seat and a set of pipe gripping wedge slips seated therein, the seats tapering in opposite directions to each other whereby to restrain the respective pipe sections against relative outward movement, a rotatable longitudinally slidable connection means between and connecting the upper one of said anchor means and the body, and a fluid passage through the wall of the body intermediate said sealing units.

6. A pressure bleed-off assembly for a pipe string being Withdrawn from a well, comprising, a generally tubular body vertically mountable on a wellhead about said pipe string, a base member carried by the lower end of the body and forming a non-rotatable connection to the wellhead, a pair of annular resilient sealing units mounted in the bore of the body to form longitudinally spaced circumferential seals between the body and pipe string sections on opposite sides of a coupling joining said sections, upper and lower spaced anchor means carried by the body for releasably securing the body to the respective pipe string sections at points respectively above and below said sealing units, each of said anchor means comprising a slip bowl having a conically tapered seat and a set of pipe gripping wedge slips seated therein, the seats tapering in opposite directions to each other whereby to restrain the respective pipfe sections against relative outward movement, a rotatable longitudinally slidable connection means between and connecting the upper one of said anchor means and the body, said connection means comprising a tubular sleeve member connected to the upper slip bowl and slidably and rotatably extending into the bore of the body, means limiting the relative longitudinal movement between said sleeve and the body, and a fluid passage through the wall of the body intermediate said sealing units.

7. A pressure bleed-off assembly for a pipe string being withdrawn from a well, comprising, a generally tubular body vertically mountable on a Wellhead about said pipe string, a base member carried by the lower end of the body and forming a non-rotatable connection to the wellhead, a pair of annular resilient sealing units mounted in the bore of the body to form longitudinally spaced circumferential seals between the body and pipe string sections on opposite sides of a coupling joining said sections, upper and lower spaced anchor means carried by the body for releasably securing the body to the respective pipe string sections at points respectively above and below said sealing units, the lower one of said anchor means being positioned in said base member and the upper one of said anchor means being carried by the upper end of the body, a rotatable longitudinally slidable connection means between and connecting the upper one of said anchor means and the body, and a fluid passage through the wall of the body intermediate said sealing units.

8. A pressure bleed-off assembly for a pipe string being withdrawn from a well, comprising, a generally tubular body vertically mountable on a wellhead about said pipe string, a base member carried by the lower end of the body and forming a non-rotatable connection to the wellhead, a pair of annular resilient sealing units mounted in the bore of the body to form longitudinally spaced circumferential seals between the body and pipe string sections on opposite sides of a coupling joining said sections, upper and lower spaced anchor means carried by the body for releasably securing the body to the respective pipe string sections at points respectively above and below said sealing units, the lower one of said anchor means being positioned in said base member and the upper one of said anchor means being carried by the upper end of the body, each of said anchor means comprising a slip bowl having a conically tapered seat and a set of pipe-gripping wedge slips seated therein, the seats tapering in opposite directions to each other whereby to restrain the respective pipe sections against relative outward movement, a rotatable longitudinally slidable connection means between and connecting the upper one of said anchor means and the body, and a fluid passage through the wall of the body intermediate said sealing units.

9. A pressure bleed-off assembly for a pipe string being Withdrawn from a well, comprising, a generally tubular body vertically mountable on a wellhead about said pipe string, a base member carried by the lower end of the body and forming a non-rotatable connection to the wellhead, a pair of annular resilient sealing units mounted in the bore of the body to form longitudinally spaced circumferential seals between the body and pipe string sections on opposite sides of a coupling joining said sections, upper and lower spaced anchor means carried by the body for releasably securing the body to the respective pipe string sections at points respectively above and below said sealing units, the lower one of said anchor means being positioned in said base member and the upper one of said anchor means being carried by the upper end of the body, each of said anchor means comprising a slip bowl having a conically tapered seat and a set of pipegr-ipping Wedge slips seated therein, the seats tapering in opposite directions to each other whereby to restrain the respective pipe sections against relative outward movement, a rotatable longitudinally slidable connection means between and connecting the upper one of said anchor means and the body, said connection means comprising a tubular sleeve member connected to the upper slip bowl and slidably and rotatably extending into the bore of the body, means limiting the relative longitudinal movement between said sleeve and body, and a fluid passage through the wall of the body intermediate said sealing units.

10. A pressure bleed-ofi assembly for a pipe string being withdrawn from a well, comprising, a generally tubular body vertically mountable on a wellhead about said pipe string, a base member carried by the lower end of the body, said base member comprising a plate member of non-round configuration adapted to form a non-rotative connection with said wellhead, a pair of annular resilient sealing units mounted in the bore of the body to form longitudinally spaced circumferential seals between the body and pipe string sections on opposite sides of a coupling joining said sections, upper and lower spaced anchor means carried by the body for releasably v securing the body to the respective p1pe stnng sectlons at points respectively above and below said sealing units, the lower one of said anchor means being positioned in said plate member, a rotatable longitudinally slidable connection means between and connecting the upper one of said anchor means and the body, and a fluid passage through the wall of the body intermediate said sealing units.

11. A pressure bleed-off assembly for a pipe string being withdrawn from a well, comprising, a generally tubular body vertically mountable on a wellhead about said pipe string, a base member carried by the lower end of the body and forming a non-rotatable connection to the wellhead, a pair of annular resilient sealing units mounted in the bore of the body to form longitudinally spaced circumferential seals between the body and pipe string sections on opposite sides of a coupling joining said sec tions, upper and lower spaced anchor means carried by the body for releasably securing the body to the respective pipe string sections at points respectively above and below said sealing units, the lower one of said anchor means being positioned in the base member and comprising a slip bowl having a downwardly and inwardly tapering slip seat coaxial with the bore of the body and a set of pipe-gripping slips arranged in said bowl to hold the lower section of pipe string against downward movement, the upper one of said anchor means being carried by the upper end of said body and comprising a second slip bowl having an upwardly and inwardly tapering slip seat coaxial with the bore of the body and a set of pipe-grip ping slips arranged in said second slip bowl to hold the upper section of said pipe string against outward movement relative to the second slip bowl, a rotatable longitudinally slidable connection means between and connecting said second slip bowl and the body, and a fluid passage through the wall of the body intermediate said sealing units.

12. A pressure bleed-off assembly for a pipe string being withdrawn from a well, comprising, a generally tubular body Vertically mountable on a well head about said pipe string, means carried by the body for non-rotatably securing the body to said wellhead, a pair of annular sealing units mounted in the bore of the body to form longitudinally spaced circumferential seals between the body and pipe string sections on opposite sides of a coupling joining said sections, each of said sealing units including a generally tubular flexible resilient sleeve having one end secured in tight sealing engagement with the bore wall of the body and having its opposite end inwardly tapered into frictional engagement with the exterior of the pipe string, said opposite ends tapering toward each other, upper and lower spaced anchor means carried by the body for releasably securing the body to the respective pipe string sections at points respectively above and below said sealing units, a rotatable longitudinally slidable connection means between and connecting the upper one of said anchor means and the body, and a fluid passage through the wall of the body intermediate said sealing units.

References Cited in the file of this patent UNITED STATES PATENTS 1,530,006 Melton Mar. 17, 1925 1,870,590 Santiago Aug. 9, 1932 2,764,243 Page Sept. 25, 1958