US3006413A - brown - Google Patents

Description

Oct. 31, 1961 c. c. BROWN 3,006,413

PIPE STRIPPER FOR WELLHEADS Filed Jan. 10, 1958 2 Sheets-Sheet 1 C/ce/o C. .Brawn INVENTOR.

Oct. 31, 1961 c. (2. BROWN 3,006,413

PIPE STRIPPER FOR WELLHEADS Filed Jan. 10, 1958 2 Sheets-Sheet 2 F 26 fll Z 3.5 2

C/cero C. 5/0 wn INVENTOR.

'14 T TOR/V5 Y 3,006,413 PIPE STRIPPER FOR WELLHEADS Cicero C. Brown, Brown Oil Tools Inc., P1). Box 19236, Houston, Tex. Filed Jan. 10, 1958, Ser. No. 708,170 Claims. (Cl. 166-82) This invention relates to wellhead equipment and particularly to improved pipe stripper and seal devices for use in wellheads.

In operation of oil and gas Wells, it is frequently necessary to withdraw the production pipe string, such as the conventional tubing string, for replacement, repair, or for reworking of the well or parts of the well equipment. In order to safely withdraw such pipe string, means must ordinarily be provided to form a seal between the pipe string being withdrawn and the surrounding casing or the wellhead through which the well pipe is withdrawn, in order to prevent blow-outs or loss of control of the well during the stripping operation.

Most pipe strippers employ a flexible resilient sealing sleeve through which the pipe string is drawn in order to maintain a continuous seal between the withdrawn pipe and the surrounding pipe string or wellhead fitting, the seal means being such as will flex or expand sufliciently to allow enlargements on the pipe strings, such as couplings and the like, to be withdrawn through the stripping unit while the seal is maintained about the moving string. Very often, high pressure conditions are present or develop in the well bore during the course of the stripping operation and the seal elements are required to prevent escape of such high pressure. The pressures encountered frequently are so high that the sealing sleeve, which is usually rubber or similar resilient composition, may be blown out and release the pressure with attendant hazard to the well and personnel about the Well.

A primary object of the present invention is to provide an improved form of pipe stripper in which is incorporated metal re-enforcing elements arranged to be expandible and contractible in accordance with the changes in dimensions of the pipe string drawn therethrough, and which will act to re-enforce and support the sealing sleeve against the destructive action of high pressures which may be encountered.

An important object is to provide a pipe stripper comprising a resilient sealing sleeve and an internal metal reenforcing core which will effectively withstand high pressures and which is relatively simple in construction and easy to install on a wellhead.

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

In the drawing:

FIG. 1 is a longitudinal view, partly in section and partly in elevation, of a pipe stripper device, showing the position of the parts when contracted about the exterior of a pipe section;

FIG' 2 is a fragmentary view, similar to the upper portion of FIG. 1, showing the parts of the stripper and seal unit in their expanded positions adapted to allow passage of an enlargement carried by the pipe string; and

FIG. 3 is a perspective view of the stripper unit from which the sealing sleeve has been removed to better illustrate the details of the internal metal supporting core and re-enforcing elements thereof.

Referring to the drawing, there is shown a wellhead comprising the upper end of a well casing carrying a flanged wellhead fitting 11 at its upper end on which is mounted the tubular stripper housing 12 which carries at Patented Oct. 31, 1961 its lower end a flange 13 adapted to mate with flange 1'1 and to be bolted thereto in order to secure the stripper housing to the wellhead. It will be understood that instead of the flange connections shown, the stripper housing 12 may be connected directly to casing 10, by any other suitable and known type of connection fittings. Stripper housing 12 has side connections 14 and 15 at intermediate points thereof for discharge or admission of fluids from and into the bore of casing 10 as may be found necessary or desirable during the course of operations. Shown extending through the bore of casing 10 and housing 12 is a pipe string, such as a tubing string, designated generally by the numeral 16, and comprising a plurality of pipe sections 16a and 16b shown connected end-to-end by means of a conventional screw collar or coupling 17. The stripper and seal unit is shown positioned in housing 12 to form the stripper seal and between tubing string 16 and bore 12a of the housing.

The stripper unit comprises a generally tubular sealing sleeve, designated generally by the numeral '18, constructed of flexible resilient material, such as rubber and the like, disposed coaxially in housing 12. Sleeve 18 comprises a substantially cylindrically straight shank portion 19 which merges into an inwardly tapering relative thick lip portion 20 defined by a generally conical inwardly tapering outer wall 21 and a similarly shaped inwardly tapering inner Wall 22. Inner and outer walls 22 and 21 are joined by a generally cylindrical wall defining a constricted bore 23 through lip portion 20 having a nominal diameter slightly less than the external diameter of pipe 16 so as to normally maintain slidable sealing engagement with the exterior of pipe 16 as the latter is drawn through bore 23. The lower end of the wall defining bore 23 tapers outwardly to its juncture with the end of outer wall 21 to form the outwardly flaring surface 24 and providing a guide surface for directing enlargements on pipe 16 into bore 23 of the sealing sleeve.

The opposite end of sleeve portion 19 is secured in any suitable manner, as by vulcanizing, to a metal ring 25 of generally rectangular cross-section, which projects radially slightly with respect to the exterior of sleeve 18 in order to be supportingly engaged on an upwardly facing annular shoulder 26 formed in the wall of bore 12a of the housing, whereby to support the sealing sleeve against movement inwardly of housing 12. Ring 25 has an annular packing groove 26a its outer periphery and a packing 27 of any suitable form is disposed in groove 26a to provide a fluid-tight seal between ring 25 and the bore wall of housing 12. Sleeve 18 is provided with a metal re-enforcing core which includes a tubular body 28 extending slidably into the outer end of sleeve portion 19. The outer end of body 28 has a radially outwardly extending annular flange 29 adapted to overlie ring 25. An annular cap 30, having an axial opening 31 considerably larger in diameter than pipe 16, is provided with internal threads 32 engageable with threads 33 provided on the exterior of the upper end of housing 12 to permit the cap to be screwed down over the end of the housing. Cap 30 carries an inwardly extending annular lip 34 about its upper end defining opening 31 and adapted to bear on the upper end of flange 29 so that when cap 30 is screwed down over threads 33, lip 34 will be operative to clamp body 28 and ring 25 down against shoulder 26 to thereby lock the stripper unit in place in the housing and prevent its displacement in either direction from the bore of housing 12.

Body 28 carries about its inner end :margin a plurality of metal dogs or pawls 35 having T-shaped heads 36 at one end receivable in correspondingly shaped T-slots 37 formed in the inner end margin of body 28. The complementary shapes of the T-heads 36 and T-slots 37 are such as to permit radial movement of pawls 35 without appreciable lateral or pivoting movement with respect to one another.

Each of the dogs or pawls 35 comprises a segment of a cylinder such that when in their fully contracted position, as best seen in FIGS. 1 and 3, they will form a sub stantially closed continuous collar having an internal diameter substantially equal to that of bore 23 and which is radially expandible and contractible. The free ends of pawls 35 are sloped inwardly to form generally conical faces 38 substantially complementary to the slope of inner Walls 22 of the lip of the sealing sleeve and the outer peripheral surfaces of pawls 35 conform generally to the configuration of the adjacent portions of the inner wall of sleeve 18. The inner faces of the free ends of pawls 35 are shaped with outwardly flaring end surfaces 39 merging with faces 38. The radial thickness of pawls 35 is such that they will be in continuously maintained contact both with the exterior of the tubing string and with the inner wall of sleeve 18.

In operation, housing 12 carrying the stripper and seal unit locked in place by cap 30, is positioned over the end of pipe string 16 and secured to wellhead flange 11. As the pipe string 16 is drawn upwardly through the stripper structure, lip 20 of the sealing sleeve will closely engage the exterior of the pipe string. Should any pressure de velop in the annulus between pipe string 16 and casing 10, this pressure will be exerted against the exterior of the sealing sleeve and will urge the latter more tightly about the pipe. The external pressure on the seal sleeve will, of course, urge pawls 35 inwardly tightly about the exterior surface of pipe string 16 and because of their dimensions, the pawls will form a solid buttress ring which will effectively support the resilient material comprising the sealing sleeve and its lip portion so as to prevent any substantial degree of extrusion of the resilient material along the pipe string which might destroy the sealing sleeve and its sealing function, if not thus prevented.

As the pipe string continues to be elevated and a coupling, such as coupling 17, attempts to move through the sealing sleeve, surface 24 will guide the coupling into bore 23 and the natural resilience of lip 20 will permit bore 23 to expand sulficiently to allow the coupling to pass through bore 23 and to then engage the outwardly flaring surfaces 39 of the pawls, which will thereby be thrust radially outwardly sufliciently to allow coupling 17 to pass between the radially expanded pawls, as best seen in FIG. 2. At the same time, since pawls 35 will be thrust against the inner surface of sleeve portion 19, the latter will be radially expanded snfliciently to allow the necessary outward movement of the pawls while at the same time will resiliently resist this movement suflicient-ly to maintain the pawls in tight engagement about coupling 17. The amount of the radial movement of the pawls will be relatively small so that the interstices between the pawls will be quite small in width and too narrow to permit any substantial extrusion of the sealing sleeve through these narrow spaces. Ordinarily the number of pawls 35 will be selected so that a minimum amount of separation will occur as a result of the expansion required to allow passage of the couplings or other conventional enlargements on the pipe string. In the embodiment illustrated, six pawls are shown, but it will be understood that a smaller or larger number of segments may be employed, depending upon the degree of expansive movement expected and the pressures which may be anticipated during the operation of the device.

It will be understood that pipe connections may be made to fittings 14 and 15 for relief of any pressure which may develop in the annular space between the tubing and casing while the stripping operation takes place; or, if desired, weighting fluid may be introduced through these fittings into the casing to kill any pressure tending to cause a blowout.

It will be understood that various modifications and alterations 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 I claim and desire to secure by Letters Patent is:

1. A tubing stripper, comprising, a generally tubular housing mountable on a Wellhead, a flexible resilient sealing sleeve co-axially disposed in the bore of said housing, means securing one end of said sleeve in fluid-tight engagement to the housing, the opposite end of said sleeve comprising a generally conical portion tapering inwardly toward the longitudinal axis of said sleeve and defining a constricted bore through said portion adapted to provide slidable sealing engagement about the exterior of a pipe string being withdrawn therethrough, and a metallic core means for reinforcing said sleeve, said core means com prising a tubular body extending into the bore of said one end of said sleeve in close fitting engagement therein, and a radially expandible and retractible metallic collar member secured to the inner end of said body and disposed inside the bore of the sleeve adjacent the interior of said tapered end portion, said collar member comprising a plurality of complementary arcuate segments, cooperating means on the inner end of said body and the adjacent ends of said segments forming a radially slidable connection between the segments and said body, the configuration of the external periphery of said segments conforming substantially to that of the adjacent inner wall portions of said sleeve, and the radial thickness of said segments being such as to have continuous contact with the exterior of said pipe string and with the inner wall of said sealing sleeve.

2. A tubing stripper according to claim 1 wherein said housing is provided with fluid passage means opening radially through the wall thereof interiorly of the point of fluid-tight engagement of said sleeve to said housing.

3. A tubing stripper, comprising, a generally tubular housing mountable on a wellhead, a flexible resilient sealing sleeve coaxially disposed in the bore of said housing, means securing one end of said sleeve in fluid-tight engagement to the housing, said means including an upwardly facing shoulder in the bore of the housing, a metallic ring secured to said one end of said sleeve and engageable on said shoulder, and means on the housing for clamping the ring against said shoulder, the opposite end of said sleeve comprising a generally conical portion tapering inwardly toward the longitudinal axis of said sleeve and defining a constricted bore through said portion adapted to provide slidable sealing engagement about the exterior of a pipe string being Withdrawn therethrough, and a metallic core means for reinforcing said sleeve, said core means comprising a tubular body extending into the bore of said one end of said sleeve in close fitting engagement therein, and a radially expandible and retractible metallic collar member secured to the inner end of said body and disposed inside the bore of the sleeve adjacent the interior of said tapered end portion, said collar member comprising a plurality of complementary arcuate segments, cooperating means on the inner end of said body and the adjacent ends of said segments form-ing a radially slidable connection between said segments and said body, the configuration of the external periphery of said segments conforming substantially to that of the adjacent inner wall portions of said sleeve, and the radial thickness of said segments being such as to have continuous contact with the exterior of said pipe string and with the inner wall of said sealing sleeve.

4. A tubing stripper, comprising, a generally tubular housing mountable on a wellhead, a flexible resilient sealing sleeve coaxially disposed in the bore of said housing, a metal ring secured to the outer end of the sleeve, an upwardly facing shoulder in the bore of the housing engageable beneath the ring to hold the sleeve against movement inwardly of the housing, a tubular metal body extending into said outer end of said sealing sleeve in close fitting engagement therein, the outer end of said body having an annular flange extending radially outwardly in overlying engagement with said ring, means carried by the housing to urge said flange and ring into clamping engagement against said shoulder, the opposite end of said sleeve comprising a generally conical lip portion tapering inwardly toward the longitudinal axis of said sleeve and defining a constricted bore through said portion adapted to provide slidable sealing engagement about the exterior of a pipe string being withdrawn therethrough, a radially expandible and retractible metallic collar member secured to the inner end of said body and disposed inside the bore of the sleeve adjacent the interior of said tapered lip portion, said collar member comprising a plurality of complementary arcuate segments, cooperating means on the inner end of said body and the adjacent ends of said segments forming a radially slidable connection between the segments and said body, the configuration of the external periphery of said segments conforming substantially to that of the adjacent inner Wall portions of said sleeve, and the radial thickness of said segments being such as to have continuous contact with the exterior of said pipe string and with the inner wall of said sealing sleeve.

5. A tubing stripper, comprising, a generally tubular housing mountable on a wellhead, a flexible resilient sealing sleeve coaxially disposed in said housing and having one end secured in fluid-tight engagement to the housing, the opposite end of said sleeve comprising a relatively thick lip portion defined by inner "and outer generally conical walls tapering inwardly toward the longit-udinal axis of said sleeve, the inner ends of said walls being joined by a substantially cylindrical wall defining a constricted bore through the lip portion adapted to provide slidable sealing engagement about the exterior of a pipe string being withdrawn therethrough, and a metallic core means for reinforcing said sleeve, said core means comprising a tubular body extending into the bore of said one end of said sleeve in close fitting engagement therein, and a radially expandible and retractible metallic collar member secured to the inner end of said body and disposed inside the bore of said sleeve adjacent the inner wall of said lip portion, said collar member comprising a plurality of complementary arcuate segments, cooperating means on the inner end of the body and the adjacent ends of said segments forming a radially slidable connection between the segments and said body, the configuration of the external periphery of said segments confcrming substantially to that of the adjacent inner wall portions of said sleeve, and the radial thickness of said segments being such as to have continuous contact with the exterior of said pipe string and the inner wall of said sealing sleeve.

References Cited in the file of this patent UNITED STATES PATENTS 2,096,882 Chernosky Oct. 26, 1937 2,163,007 ODell June 20, 1939 2,287,205 Stone June 23, 1942 2,555,647 King June 5, 1951 2,609,836 Knox Sept. 9, 1952 2,743,780 Brown May 1, 1956 2,762,638 Brown Sept. 11, 1956 2,808,229 Bauer et al. Oct. 1, 1957 2,832,617 Gibson Apr. 29, 1958

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