US3371716A - Bridge plug - Google Patents

Description

March 5, 1968 J. H. CURRENT BRIDGE PLUG Filed Oct. 23, 1965 (fa/new h. (u/r enz INVENTOR.

United States Patent 3,371,716 BRIDGE PLUG James H. Current, Houston, Tex., assignor, by mesne assignments, to Schlumberger Technology Corporation, Houston, Tex., a corporation of Texas Filed Oct. 23, 1965, Ser. No. 503,503 2 Claims. (Cl. 166-118) ABSTRACT OF THE DISCLOSURE A well tool having slips and packing and an elastomeric expander member with a high durometer hardness value relative to the packing, whereby the expander can function efliciently to expand the slips as well as preventing extrusion of the packing under pressure.

This invention relates generally to subsurface well tools and, more particularly, to a permanently set bridge plug for blocking fluid flow in a well conduit.

An object of the present invention is to provide a new and improved bridge plug which is economical to manufacture and embodies fewer parts than is normally used in analogous tools.

Another object of the invention is to provide a new and improved bridge plug having novel slip expanders which serve to expand the slips and support them into anchoring engagement with the well conduit and further serve to block cold flow or extrusion of the packing element under pressure.

A further object of the invention is to provide a new and improved locking device for maintaining parts of the bridge plug in expanded positions in a well conduit.

With these and other objects in mind, the invention comprises an elongated tubular body which carries normally retracted anchors and packing. The body is provided with a fixed abutment and a movable abutment. The latter abutment is movable along the body to shift the normally retracted anchors into engagement with the well conduit and to foreshorten and expand the packing. Elastomer expander elements serve to expand the slips and prevent cold flow or extrusion of the packing element. A locking device between the movable abutment and the body locks the bridge plug permanently set in a well conduit. The locking device includes a resilient element which is cooperable with a thread form on the body and is movably disposed in an helical groove on the movable abut-ment, permitting unidirectional relative movement between the body and the movable abutment to lock parts of the plug in expanded positions.

The novel features of the present invention are set forth with particularity in the appended claims. The present invention both as to its structural organization and utility together with further objects and advantages thereof may best be understood by way of illustration and example of one embodiment when taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a longitudinal half-section view of a new and improved bridge plug with parts in their normally retracted positions for running-in to a well conduit;

FIG. 2 is a fragmentary enlarged view of the new and improved locking device of the present invention; and

FIG. 3 is a fragmentary view of the various parts of the bridge plug when permanently set in a well conduit.

Turning now to FIG. 1, the bridge plug includes an elongated tubular body having a lower guide and abutment 11 integrally formed on its lower end. Centrally of the body is a lower blind bore 12 and an upper threaded bore 13. Between these two bores is a solid plug 14 which prevents any fluid flow through the body. The threaded bore 13 provides a means for attaching the body to a conventional setting tool (not shown) in a Well-known manner.

Movably disposed on the upper portion of the body 10 is an upper abutment 15. The upper abutment is in the form of an annular sleeve which is sized for reception on the tubular body. Between the sleeve and body is a locking device 16 for unidirectionally permitting longitudinal relative motion therebetween. The structure and function of the locking device 16 will be more fully described hereinafter.

Abutting an upper shoulder 17 on the lower abutment 11 is an integral, expansible slip member 18 having downward facing wickers or teeth 19 on the periphery thereof. An annular inclined surface 20 is formed on the interior of the slip member 18, Another integral, expansible slip member 21 abuts a lower shoulder 22 on the movable abutment 15 and is substantially identical to the lower slip member but is oppositely disposed and has upwardly facing wickers or teeth 23 on the periphery thereof. Both slip members have peripheral grooves 24 which receive encircling expansible restraining bands 25, 26 of differing predetermined strengths. The bands aid in initially holding the slips in inoperative positions as well as allowing various elements of the bridge plug to be selectively operated in response to setting force of predetermined magnitudes.

Each slip element is made radially expansible by providing a first series of radially cut slots 27 around the circumference thereof and providing a second series of like slots 28 alternately disposed between the first series. These slots extend from one end of each slip element to points 29 near the respective opposite ends of each slip element. Although the slip elements are integrally formed, they have sufiicient resiliency to 'be readily expanded into engagement with the conduit wall.

An annular elastomer packing element 30 surrounds the body 10 and is disposed between an upper expander 31 and a lower expander 32, the elements being slidably carried on body 10. The upper expander is generally frusto-conically shaped. The outer surface 33 thereof is overlaid by a frusto-conical thin metal sheet 34 which extends from near the base of the cone to its apex. The upper expander is cooperable with the upper slip element 21 to laterally shift the slip element outwardly of the body and into gripping engagement with the conduit as the slip element is driven downwardly over the expander during setting of the bridge plug. The lower expander 32 and thin metal overlay 35 are identical in configuration to the upper expander and metal overlay but are oppositely disposed and are cooperable with lower slip element 18 to laterally shift the lower slip element outwardly of body 10.

The expanders 31, 32 are made of an elastomeric material such as Hycar having a significantly greater durometer hardness value than the annular elastomer packing element 30. By way of example, packing element 30 may have a durometer hardness value in a range of 60- 70, while the elastomer expanders 31, 32 may have durometer hardness values in the range of -100. A characteristic of such elastomers is that they behave like incompressible fiuids. External forces applied thereto will generate internal pressures within elastomers which may cause cold flow or extrusion along paths of least resistance. But, if the system is closed, the elastomers will transmit such pressures to the enclosure, there being no substantial change in volume of the elastomers.

The expanders 31, 32 have sufiicient hardness to cause radial expansion of the integral expansible slip elements 18, 21 as the abutments force the slips over the expanders. Metal overlays 34, 35 reduce the frictional drag. Eventually, the wickers or teeth 19, 23 engage the wall of the conduit. A part of the forces transmitted by the abutments to the slip elements during setting of the bridge plug acts to move expanders 31, 32 toward each other to foreshorten and expand packing element 30. Also, peripheral portions 37, 38 of the expanders flow outwardly to engage the wall of conduit 36. When the teeth have engaged the wall as shown in FIG. 3, both the elastomer expanders 3 1, 32 and the elastomer packing element 30 are confined by the wall of conduit 36, the plug body and the metal overlays 34, 35 which are backed by the wall engaged slip elements. The system is then closed. Further increased setting forces generate further pressures within the elastomers. Pressures within packing element 30 create a tight pack-off between the conduit 36 and body 10. Pressures generated within expanders 31, 32 act outwardly on the slip elements to dig the wickers or teeth 19, 23 into the Wall of the conduit and firmly anchor the bridge plug therein.

As previously mentioned, the radially outer portions 37, 38 of the expanders 31, 32 cold flow outwardly to engage the wall of conduit 36. These annular portions, being of high hardness relative to packing element 30 serve to prevent cold flow or extrusion of the packing element under pressure. It will also be noted that the slip elements 18, 21 themselves serve as back-ups for both the outer portions 37, 38 of the expanders and the packing element 30 to aid in effectively packing-01f the annulus between the conduit 36 and body 10.

Turning now to the locking device 16 between the upper movable abutment and body 10, attention is directed to FIG. 2. An upper peripheral portion 39 of body 10 has a special thread form 40 formed thereon. This thread form is a modified coarse buttress variety and defines a helical thread track 41. An upper beveled surface of the thread form 40 provides a helical cam surface 42. Internally formed in movable abutment 15 is a helical groove 43, the grooves having the same lead as thread form 40. Received in track 41 and partially in groove 43 is a locking device in the form of a rectangular wire coil spring 44. The inside diameter of the spring in its unflexed condition is approximately equal to the diameter of thread track 41. The width of the spring is slightly less than the depth of groove 43. If a downward force is exerted on abutment 15 to move its downwardly relative to body 10, cam surface 42 on thread form 40 acts to radially expand the coil spring 44 outwardly into groove 43 until the spring disengages from thread form 40. When the upper face 45 of the spring passes the lower face 46 of the thread form, the inherent resiliency of the spring will cause it to snap inwardly into track 41. Thus, it will be apparent that downward movement of the abutment 15 relative to body 10 is permitted. However, it will also be apparent that upward movement of the abutment relative to the body is not permitted. Abutment between the upper face 45 of spring 44 and the lower face 46 of thread form 40 looks the movable abutment and body together.

In operation, the elements of the bridge plug are assembled as shown in FIG. 1 and the plug is operatively connected to a setting tool which is capable of exerting an upward pull on body 10 and a downward push on abutment 15. Such setting tools are well known and need not be fully described here. The apparatus is then shifted downwardly through the well conduit to a predetermined setting point. When desired, the setting tool is actuated and an upwardly directed setting force is applied to body 10 and a downwardly directed setting force is applied through a setting sleeve (not shown) tomovable abutment 15. Generally, upper restraining band is made to have less strength than lower restraining band 26. Therefore, as upper abutment 15 moves downwardly on the body 10, the top slip element 21 is wedged over the expander 31 and expanded against the well conduit 36 prior to expansion of the lower slip element 18.

When the upper slip element 21 abuts the conduit wall, downward shifting of the movable abutment 15 is halted and the applied setting forces cause body 10 with integral abutment 11 to move upwardly, wedging the lower slip element 18 over the lower expander 32 and expanding the lower slip element against the conduit wall. During this movement, the lower and upper elastomer expanders 31, 32 are moved toward each other to foreshorten and expand the annular elastomer packing element 30 outwardly into firm sealing engagement with the Wall of the well conduit. The outer peripheral portions 37, 38 of the upper and lower expanders are also deformed slightly and engage the conduit so that there is no substantial annular clearance space through which the relatively softer packing element 30 can cold flow or extrude. Further setting forces substantially increase pressure within the expanders 31, 32 which act on slip elements 18, 21 to cause teeth 19, 23 to dig into the wall of conduit 36.

As the upper abutment 15 is moving downwardly relative to the body 10, cam surface 42 on thread form 40 causes the coil spring 44 to resiliently flex outwardly and into the helical groove 43. The spring repeatedly flexes and returns into the helical track 41 until the abutment 15 is in its lowermost position relative to body 10. When the elements of the plug are fully expanded, the aforementioned setting tool releases from the bridge plug automatically and since upward movement of the abutment 15 relative to the body is prevented by abutment between the upper face 45 of the helical coil spring 44 and the lower face 46 of thread form 40, the bridge plug is locked in set condition.

Any tendency of the bridge plug to move upwardly in the well conduit will be desisted by the upper slip element 21, and conversely downward movement is resisted by the lower slip element 18. Pressure differentials acting across the plug from either above or below will only serve to more firmly anchor the plug in the well conduit.

It will be observed from the foregoing that applicant has provided a new and improved bridge plug which is economical to manufacture and will function to effectively plug fluid flow in a well conduit. The slip expanders prevent cold-flow or extrusion of the annular packing element as well as performing the function of wedging and expanding the slips outwardly and supporting the slips in gripping engagement with the well conduit. No heavy steel cones are used. After full expansion of parts of the bridge plug, it is permanently locked in set condition in the well conduit.

Since certain changes may be made in the above-disclosed apparatus without departing from the scope of the inventive concept involved, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A well tool comprising: the body member; normally retracted slip means on said body member which are expandable outwardly for anchoring against a well conduit wall, said slip means having inner inclined surfaces; elastomeric packing means encircling said body member and arranged to be compressed and thereby expanded outwardly to pack off a well bore; and expander means adjacent the end of said packing means and movable relative to said slip means for expanding said slip means, said expander means having outer inclined surfaces cooperable with said inner inclined surfaces to enable outward expansion of said slip means, said expander means being constructed of an elastomeric material having a high durometer hardness value relative to said elastomeric packing means, whereby said expander means has sufficient resistance to deformation to enable eificient outward expansion of said slip means and can further function to prevent extrusion of said packing means under pressure.

2. The well tool of claim 1 further including a thin metallic overlay on said outer inclined surfaces for reducing frictional resistance to relative movement between said expander means and said slip means.

References Cited UNITED STATES PATENTS 2,855,051 10/1958 Holloway 166130 X Graham 166120 X Brown 166-134 X Brown 166-434 Urbanosky 166-134 X CHARLES E. OCONNELL, Primary Examiner.

7 DAVID H. BROWN, Assistant Examiner.

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