Title:
SNUBBING APPARATUS
United States Patent 3797570


Abstract:
Snubbing apparatus for elevating and lowering an elongated tubular structure from and into a well bore while maintaining a seal between the tubular structure and the well head, wherein the tubular structure is releaseably engageable by traveling slip and traveling blowout preventer devices and by stationary slip and stationary blowout preventer devices, alternately, to elevate and lower the tubular structure, without causing movement of the tubular structure through the closed stationary blowout preventer device.



Inventors:
LEUTWYLER K
Application Number:
05/251211
Publication Date:
03/19/1974
Filing Date:
05/08/1972
Assignee:
BAKER OIL TOOLS INC,US
Primary Class:
International Classes:
E21B19/00; E21B33/072; (IPC1-7): E21B41/00
Field of Search:
166/75,77,77.5 173
View Patent Images:
US Patent References:



Foreign References:
CA691340A
Primary Examiner:
Leppink, James A.
Attorney, Agent or Firm:
Kriegel, Bernard
Claims:
I claim

1. In snubbing apparatus for longitudinally moving an elongated structure extending from a well head at the top of a well: support means including stationary support means and vertically traveling support means, traveling slip means carried by said traveling support means within said stationary support means and being accessible laterally through said stationary support means, stationary slip means carried by said stationary support means above said traveling slip means, said slip means respectively being selectively operable to support said elongated structure and to allow free movement of said elongated structure therethrough, traveling blowout preventer means carried by said traveling support means, stationary blowout preventer means carried by said stationary support means, said blowout preventer means respectively being operable to selectively form a seal with said elongated structure and to allow movement of said elongated structure therethrough, means for forming a seal with the well head and with the respective blowout preventer means when said blowout preventer means form a seal with said elongated structure, means releasably securing said traveling slip means to said traveling support means, and means releasably securing said stationary slip means to said stationary support means, whereby non-conformities on said elongated structure can pass through said vertical traveling support means and stationary support means upon selective removal of said traveling slip means and stationary slip means from said traveling support means and stationary support means, respectively.

2. In apparatus as defined in claim 1, said means for forming a seal with the well head comprising a tubular member connected to one of said blowout preventer means, a tubular member connected to the other of said blowout preventer means, said tubular members being telescopically engaged one within the other, sealing means between said tubular members, and actuator means for telescopically shifting said tubular members, said traveling slip means and said traveling blowout preventer means being mounted on said traveling support means with said traveling slip means releasably secured to said traveling blowout preventer means.

3. In apparatus as defined in claim 1, said blowout preventer means each comprising opposed rams shiftable between retracted positions and positions in cooperative sealing engagement with said elongated structure, and fluid pressure operated means for shifting said rams between said positions.

4. In apparatus as defined in claim 1, said traveling slip means and said stationary slip means each comprising upwardly and downwardly holding slip means operable to engage said elongated member and move the same in both vertical directions.

5. In apparatus as defined in claim 1, said traveling slip means and said stationary slip means each comprising upwardly and downwardly holding slip means operable to engage said elongated member and move the same in both vertical directions, said blowout preventer means each comprising opposed rams shiftable between retracted positions and positions in cooperative sealing engagement with said elongated structure, and fluid pressure operated means for shifting said rams between said positions.

6. In apparatus as defined in claim 1, said traveling slip means and said traveling blowout preventer means being mounted on said traveling support means with said traveling slip means releasably secured to said traveling blowout preventer means.

7. In a snubbing apparatus for longitudinally moving an elongated structure extending from a well head to the top of a well; support means including a platform mounted in vertically spaced relation above the well head, stationary blowout preventer means mounted on the well head, stationary slip means mounted on said platform, traveling blowout preventer means and interconnected traveling slip means, telescopic means for forming a seal with the well head and with said stationary and traveling blowout preventer means, and actuator means interposed between said stationary blowout preventer means and said traveling blowout preventer means for actuating said traveling blowout preventer means and interconnected traveling slip means vertically relative to said stationary slip means, whereby said elongated structure is adapted to be alternately moved vertically with respect to said well head and said platform and stationarily supported with respect to said well head and said platform.

8. In a snubbing apparatus as defined in claim 7, said support means comprising a base, post assemblies extending between said base and said platform in spaced relation about telescopic means, said actuator means comprising fluid pressure operated cylinder and piston means incorporated in said post assemblies and connected to said traveling blowout preventer means and interconnected slip means.

Description:
Heretofore, snubbing apparatus or units have been employed for the purpose of running or retrieving tubing or drill pipe into or from a well bore, while the well bore is maintained under pressure, so as to enable the well to be worked over without requiring that the well be killed. This is desirable in that the productivity of the sub-surface well zone may decline so severely after killing the well as to render the workover operation economically infeasible.

Such snubbing operations are comparatively simple, particularly in low pressure wells, when pulling or running flush or semi-flush joint tubing which has good surface quality on the outside diameter, by using conventional snubbing apparatus including a resilient stripper which sealingly engages the tubing to retain pressure in the well casing. In higher pressure snubbing operations, conventional ram type blowout preventers may be employed using resilient inserts on the rams for sealingly and slidingly engaging the well tubing. In either of these events, when the surface quality of the tubing is poor due to scale, corrosion, or the like, the stripper rubbers or ram inserts rapidly deteriorate tending to cause loss of pressure control.

In the case that the snubbing operation involves pulling or running pipe which has non-conformities, such as threaded couplings, or other non-conformities, including packers, side pocket mandrels, and the like, the use of stripper rubbers is not possible, and the use of ram type blowout preventers is necessary, so that the blowout preventer can be operated to allow the passage of the non-conformity through the preventer while another blowout preventer is closed on the pipe and prevents loss of pressure control, as the pipe slides through the latter blowout preventer, into the space between the respective blowout preventers. In such operations, the blowout preventer sealing elements are nevertheless subject to wear and if the pipe is of poor surface quality, the wear will be rapid and the loss of pressure control continues to be a problem.

In some instances, the tubular structure or pipe to be pulled or run from or into the well will not permit movement of the pipe relative to the conventional ram rype devices, for example, when the structure consists of multiple tubing strings, single tubing strings with attached small hydraulic control lines for operating sub-surface valves, electric cables, or signal wires.

The present invention provides snubbing apparatus in which the mechanism for hoisting or lowering tubular structures or pipe and a traveling blowout preventer mechanism are interconnected for unitary movement relative to stationary pipe supporting means and stationary blowout preventer mechanism. The tubular structure or pipe being raised or lowered from or into the well does not slide through the blowout preventer means. Accordingly, the blow out preventer sealing elements are not subject to wear, in the case of tubing of poor surface quality, and in the case of tubular structures or pipe having non-conformities, specially designed blowout preventer sealing elements may be devised for sealing engagement with the irregular forms, since no sliding movement occurs.

An object of the invention is to provide snubbing apparatus whereby pressure control may be maintained with certainty and wherein the sealing elements need not be replaced at frequent intervals.

More particularly, the invention contemplates a supporting structure which is connectable to the well head and which contains stationary blowout preventer means adapted for sealing engagement with the tubular structure extending through the supporting means, and a vertically spaced traveling blowout preventer means. The supporting structure also carries stationary slip means engageable with the tubular structure to support the latter in progressive positions as it is moved from or into the well, and a traveling slip means engages the tubular structure to shift the latter from and into the well, while the stationary slip means are released. Actuator means are provided for shifting the traveling blowout preventer and the traveling slip means in unison.

This invention possesses many other advantages, and has other purposes which may be made more clearly apparent from a consideration of a form in which it may be embodied. This form is shown in the drawings accompanying and forming part of the present specification. It will now be described in detail, for the purpose of illustrating the general principles of the invention; but it is to be understood that such detailed description is not to be taken in a limiting sense, since the scope of the invention is best defined by the appended claims.

Referring to the drawings:

FIG. 1a and 1b, together, constitute a view in vertical section, showing snubbing apparatus made in accordance with the invention, and showing a well pipe supported in the traveling slip assembly for movement from the well and sealingly engaged by the traveling blowout preventer;

FIGS. 2a and 2b, together, constitute a view in vertical section, generally corresponding to FIGS. 1a and 1b, but showing the well pipe supported by the stationary slip assembly in an upwardly shifted position, and sealingly engaged in the stationary blowout preventer;

FIG. 3 is a horizontal section, as taken on the line 3--3 of FIG. 1a; and

FIG. 4 is an enlarged vertical section, showing a typical slip assembly.

As seen in the drawings, a support structure 10 is disposed at the upper end of the well head 11 located at the top of a well into and from which a tubular structure shown as a length of pipe P is to be run and removed by the snubbing apparatus of the invention. The pipe P is shown as having various non-conformities, such as a coupling 12 and a packer 13.

Included in the support structure 10 is stationary support structure comprising a base flange 15 having a central opening 16 therethrough which extends through a neck 17 which carries a second, lower flange 18. The flange 18 seats on a typical blowout preventer assembly which in the present apparatus constitutes a stationary blowout assembly SB. The flange 18 is connected by suitable fasteners 19 to the top of the blowout assembly SB and a suitable packing ring 20 is interposed therebetween. The body 21 of the blowout preventer assembly SB has a central opening 22 through which the pipe P or other tubular structure is adapted to extend and which is larger than the largest non-conformity in the pipe P which must pass through the stationary blowout preventer SB. At its lower end, the body 21 of the stationary blowout preventer SB seats on the top flange 23 of the well head 11 and is connected to the latter by suitable fasteners 24. A packing ring seal 25 is interposed between the blowout preventer body 21 and the well head flange 23.

The blowout preventer assembly SB is more or less conventional and need not be shown in specific detail. An example of a commercially available blowout preventer of the type shown is the type LWS double blowout preventer of Shaffer Tool Works, illustrated at page 4,286 of the "Composite Catalog of Oilfield Equipment and Services," 1970-71. The blow out preventer SB comprises a pair of opposing upper rams 26, 26 and a pair of opposing lower rams 27, 27, respectively, adapted to be actuated between retracted positions, as shown in FIG. 1b, in which the rams 26 and 27 clear the opening 22 through the blowout preventer body 21, and inner positions, as shown in FIG. 2b. Only the actuator means for one of the upper and lower rams 26 and 27 are shown in FIG. 1b, and such actuator means comprises respective upper and lower actuator cylinders 29 and 30 in which actuator pistons 31 and 32 are reciprocable. The rams 26 and 27 have rods 33 and 34 extending through suitable sealing means 35 into the actuator cylinders 29 and 30, and the pistons 31 and 32 are supported on reduced rod sections 36 and 37 which extend through suitable seals 38 and 39. Thus, fluid under pressure may be applied to the respective piston chambers 29 and 30 at either side of the pistons 31 and 32, whereby the rams 26 and 27 are moveable between the retracted positions of FIG. 1b and the inner positions of FIG. 2b for sealing engagement with the pipe P.

For sealing engagement with the pipe P or other tubular structure, each of the rams 26 has resilient sealing elements 26a of elastomeric material and the rams 27 have sealing elements 27a of elastomeric material. These sealing elements 26a and 27a are adaptable to seal about the tubular pipe, as shown, and are also adaptable to seal about other tubular structure, such as multiple pipe strings, control lines or cables associated with one or more pipes, and the like.

Extending upwardly from the base flange 15 of the supporting structure 10 is a central tubular member 40 and a suitable number of angularly spaced tubular cylinder bodies 41. Telescopically, shiftably extending into the central tubular member 40 is an elongated inner tubular member 42, at the upper end of which and above the upper end of the outer tubular member 40 is an outstanding flange 43, having, as seen in FIG. 3, otuwardly projecting portions 44 to which the upper ends 45 of piston rods 46 are connected by fasteners 47. These piston rods 46 extend telescopically downwardly into tubular actuator cylinder bodies 41 through an upper seal ring 48. At the lower ends of the piston rods 46 are pistons 49 having piston rings 50 sealingly engaged within the actuator cylinder bodies 41. Each actuator cylinder body 41 has a base flange 51 connected by fasteners 52 to the base flange 15 of the supporting structure 10, a suitable packing ring 53 providing a seal therebetween. Accordingly, in an obvious manner, pressure fluid is applicable to the actuator cylinder body 41 at either side of the piston 49 to either elevate or retract the piston rods 46 in unison, so as to elevate the supporting flange 43 or lower the latter. To provide a seal around the telescopic tubular body 42, a packing gland 53 is threaded at 54 onto the upper end of the outer tubular body 40. This confines pressure within the well head 11 to the central passage 55 through the telescopic member 42 through which the pipe P extends and is sealingly engageable by the blowout preventer rams 26 and 27 of the stationary blowout preventer SB.

A traveling blowout preventer assembly TB is supported on the support member 43 so as to be vertically moveable therewith. This traveling blowout preventer assembly TB may be, for example, a single Shaffer Tool Works type LWS blowout preventer. The body 56 of the blowout preventer TB is mounted on a support flange 57 which forms a part of the support member 43 by a suitable number of fasteners 58, a packing ring seal 59 being interposed between the blowout preventer body 56 and the flange 57.

This traveling blowout preventer assembly TB has a pair of rams 60, 60 adapted to be actuated between the inner or closed positions of FIG. 1a and the outer retracted positions of FIG. 2a. As in the case of the stationary blowout preventer SB, each of the rams 60 has an actuator rod 61 (only one of which is shown) extending through a suitable seal ring 62 into an actuator cylinder 63. On a reduced end section 64 of the rod 61 is a piston 65, and the rod section 64 extends through an outer seal 66. Thus, the rams 60 are shiftable between the inner and retracted positions by fluid pressure applied to either side of the piston 65, and as is typical of such blowout preventers corresponding actuator means are provided for each of the rams 60.

Suitably supported upon the traveling blowout preventer assembly TB is a traveling slip assembly TS. In the illustrated embodiment, the traveling slip assembly TS comprises a tubular body 67 having a base flange 68 connected by fasteners 68a to the top of the traveling blowout preventer TB. Removably mounted on a top flange 69 of the body 67, by fasteners 70, is a plate 71 having a central opening 72. The traveling slip means TS includes upper slip means 73 and lower slip means 74 adapted, as will be later described, to grip the pipe P, as will be later described, to effect upward or downward movement of the pipe string.

To the top of the actuator cylinders 41 are connected, by fasteners 75, a corresponding number of tubular posts 76, which at their upper ends are connected, by fasteners 77, beneath a work platform 78, preferably provided with an appropriate guard rail 79. The posts 76 are longitudinally slotted as at 80 to receive the outwardly projecting portions 44 of the support plate 43 and thus, the support posts 76 provide a shield about the actuator or piston rods 46 as the traveling blowout preventer TB and the traveling slips TS are elevated and lowered.

Mounted in an opening 81 in the work platform 78 is a stationary slip assembly SS which includes a support plate 82 corresponding to the support plate 71 of the traveling slip assembly TS and having an opening 83. Like the traveling slip assembly TS, the stationary slip assembly SS includes upper pipe engaging slip means 73 and lower pipe engaging slip means 74, as seen in FIG. 4, wherein the stationary slip means SS are illustrated as being typical.

The upper slip means 73 comprises a slip bowl 85 having an upwardly and outwardly tapered inner surface 86, cooperative with a companion tapered surface 87 on the pipe engaging slip elements 88 to wedge the slips inwardly into gripping engagement with the pipe P. The slip elements 88 have internal upwardly facing teeth 89 adapted to engage with the pipe P when the slip elements are lowered in the slip bowl 85, the slip elements 88 releasing the pipe P when the slip elements are elevated from the bowl 85. Actuator means 90 are provided for actuating the slip elements 88 to the upper or released positions from the pipe engaging positions. Such actuator means 90 are shown as comprising actuator cylinders 91 respectively connected at 91a to the supporting plate 82 (or in the case of the traveling slip TS to the plate 71). Reciprocable in the actuator cylinder 90 is a piston 92 having its piston rod 93 connected at 94 to a slip supporting arm 95. Accordingly, pressure fluid applied to the actuator cylinders 91 is effective to elevate the slips 88, but when such pressure fluid is exhausted, these slips are released for downward movement to the pipe engaging positions.

The lower slip means 74 comprises slip bowl 96 having a downwardly and outwardly tapered inner surface 97, cooperative with a companion tapered surface 98 on the pipe engaging slip elements 99 which have internal downwardly facing teeth 100 adapted to engage with the pipe P when the slip elements are elevated into the slip bowl 96, the slip elements 99 releasing the pipe P when the slip elements are lowered in the bowl 96. Actuator means 101 are provided for actuating the slip elements 99 to the lower or release position from the pipe engaging positions. Such actuator means 101 are shown as comprising actuator cylinders 102 respectively connected at 101a to the supporting plate 82. Reciprocable in each actuator cylinder 102 is a piston 104 having its piston rod 105 connected at 106 to a slip supporting arm 107. Accordingly, pressure fluid applied to the actuator cylinders 102 below the pistons 104 is effective to elevate the slips 99, but when such pressure fluid is exhausted, these slips are released for downward movement to the pipe engaging positions.

In the use of the apparatus, say for elevating the pipe string P, the rams 60 of the traveling blowout preventer TB are closed to effect engagement of the sealing elements 60a with the pipe string P. The traveling slip means TS are operated so that the upper slips 88 are engaged in the bowl 85 to support the pipe P. At the same time, the rams 26 and 27 of the stationary blowout preventer SB are retracted so that the sealing elements 26a and 27a clear the opening 22 through the blowout preventer body 21. Also, at the same time, the stationary slip means SS are operated so that the upper and lower slip means 73 and 74 thereof are released from the pipe P. These conditions of operation are illustrated in FIGS. 1a and 1b. Thereupon, pressure fluid is applied to the actuator cylinders 41 below the actuator pistons 49 so as to elevate both the traveling blowout preventer TB and the traveling slip assembly TS to the positions of FIGS. 2a and 2b. During such elevation, the closed blowout preventer rams 60 prevent loss of pressure control of the well as the pipe P moves upwardly. During the upward stroke of the apparatus, the packer 13 on the pipe P will move upwardly through the stationary blowout preventer SB to the upwardly spaced position shown in full lines in FIG. 2b. Thereupon, the rams 26 and 27 of the stationary blowout preventer SB are closed to form a seal about the pipe P and the slip means 73 and 74 of the stationary slip means SS are actuated into engagement with the pipe P, as shown in FIGS. 2a and 2b, to support the pipe P, so that the rams 60 of the traveling blowout preventer TB can be retracted and the slips of the traveling slip means TS opened, so that the traveling slips and traveling blowout preventer can be returned to the lower postion, while the pressure in the well is retained by the stationary blowout preventer and the pipe P remains stationary.

The foregoing operation can then be repeated to move the packer 13 in another stroke of the apparatus further upwardly to the position shown in broken lines in FIG. 2b. The operation can be repeated to continue to elevate the pipe P. In the event that any non-conformity in the tubular structure will not pass through the opening provided by the respective slip means TS and SS, they can be removed during the period that either the oversize non-conformity is passing through the platform 78 or the traveling blowout preventer TB is moving downwardly over the oversize non-conformity.

It will also be recognized that the operations can be reversed to run the tubular structure into the well.