US3364997A

US3364997A - Well-packing apparatus

Info

Publication number: US3364997A
Application number: US502936A
Authority: US
Inventors: James H Current
Original assignee: Schlumberger Technology Corp
Current assignee: Schlumberger Technology Corp
Priority date: 1965-10-23
Filing date: 1965-10-23
Publication date: 1968-01-23
Anticipated expiration: 1985-01-23

Description

Jan. 23, 1968 J. H. CURRENT 3,364,997

WELL-PACKING APPARATUS Filed OCt 23, 1965 .f/EzmeJ (bf/enf INVENTOR JKM Jan. 23, 1968 J. H. CURRENT 3,364,997

WELL-PACKING APPARATUS Filed Oct. 23, 1965 5 Sheets-Sheet 2 l ,"J VEN TOR,

www

Jan. 23, 1968 1. H. CURRENT WELL-PACKING APPARATUS 3 Sheets-Sheet 5 c/bmeJ Far/enf Filed Oct.

INVENTOR. v

United States Patent C) 3,364,997 WELL-PACKNG APPARATUS .lames H. Current, Houston, Tex., assignor, by mesne assignments, to Schlumberger Technology Corporation, Houston, Tex., a corporation of Texas Filed ct. 23, 1965, Ser. No. 502,936 Claims. (Cl. 16d-134) ABSTRACT OF THE DISCLOSURE The particular embodiment disclosed herein as illustrative of one form of the invention in well tools includes a mandrel with normally retracted slips and packing element which are expansible by expanders to pack off a well bore. The slips and packing element are releasably retained in expanded position and can be retracted when desired. To enable retraction, a rst member on the mandrel is releasable in response to a predetermined force in one longitudinal direction on the mandrel to permit movement of one slip to retracted position, and a second member on the mandrel is arranged to engage one of the expanders for moving it with the mandrel in the opposite longitudinal direction to permit retraction of the other slip.

This invention relates to Well packers for use in well bores; and, more particularly, to packers which are primarily designed to be set permanently in place within a cased well bore, but, nevertheless, are capable of being retrieved at a later time.

It often becomes necessary to pack-off a Well bore. In such cases, it is common to set a so-called permanent bridge plug or packer at the desired depth to pack-off the well against pressure differentials acting in either direction. in general, such tools are comprised of a central mandrel carrying opposed upper and lower sets of normally retracted slips slidably arranged on expanders and longitudinally spaced from one another by a normally relaxed elastomeric packing element. These tools are typically arranged whereby a setting tool relatively moves the members to foreshorten the packing element between the expanders and expand the slips into anchoring engagement with the casing wall. Then, once the tool is set, a so-called body lock permanently locks the members together.

As a well tool of this type is being positioned, it is not uncommon for an obstruction to engage one of the slips or expanders and force the slip relatively over the expander in such a manner that the slip is at least slightly expanded. This often results in premature setting which, heretofore, has usually required that the incorrectly located tool be drilled out. Then, another well tool of this type is lowered with the hope that it will clear the obstruction and reach the desired depth without being inadvertently set. Even when the packer or plug is successfully set, it is often necessary to subsequently remove it, as by drilling. Although this causes some delay, it has generally been considered more expedient heretofore to employ a permanent tool rather than a so-called retrevable tool Where cost and/ or sealing capabilities are a factor.

lt is therefore, an object of the present invention to provide a new and improved well tool which can be positively set into sealing and anchoring engagement with a casing but is nevertheless still capable of being subsequently retrieved without particularly diiculty.

Accordingly, the well tool of the present invention includes a body having a packing element disposed thereon adjacent to slidably mounted expander members. Normally retracted slip assemblies are arranged to be moved to expanded position by engagement with, and movement 3,364397 Patented Jan. 23, 1968 relative to, the expander members, and the packer element can also be expanded to provide an anchored packoii in the well bore which will remain until it is desirable to remove it. To release the well tool for retrieval from the well, a force exerted in one longitudinal direction on the body will activate means for eiecting retraction of one slip assembly, and then force exerted on the body in the opposite longitudinal direction will effect retraction of the other slip assembly and relaxation of the packing element, whereupon the tool can be retrieved in its entirety from the well bore.

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

FIG. l illustrates one embodiment of a well tool, partly in section, arranged in accordance with the principles of the present invention;

FIG. 2 is a partial cross-sectional View of one embodiment of an extendible slip member employed in the in` vention;

FIGS. 3 and 4 respectively show perspective and front views of one embodiment of an anti-extrusion ring employed in the invention;

FIG. 5 is a view similar to FIG. 1, but showing the bridge plug set into sealing and anchoring engagement with a well casing; and

FIGS. 6-8 are views, similar to FIG. 5, but showing the successive positions of the tool as it is released.

Turning now to PIG. 1, a preferred embodiment is shown in a bridge plug 10 constructed in accordance with the principles of the invention although it will be appreciated that the present invention is not limited to bridge plugs but can be utilized in production packers or the like. The central body of the bridge plug 10 is an elongated cylindrical mandrel 11 having an enlarged frusto-conical nose 12 at its lower end which provides an upwardly facing shoulder 13. The lower end of the nose 12 defines the outer opening of a blind axial bore 14 which extends upwardly into the mandrel 11 for a substantial distance toward its upper end. At th upper end of the mandrel 11, a second blind axial bore 15 extends downwardly through the mandrel but terminates short of the upper end of the axial bore 14 so as to form a solid bridge 16 between the two bores. Internal threads 17 within the upper axial bore 15 provide a means for attaching the mandrel 11 to a conventional setting tool (not shown) in the well-known manner. Where the material of the mandrel 11 is possibly permeable as, for example, by reasons of hidden inclusions, an elastomeric plug 18 is secured in the upper axial bore 15 by a threaded plug 19 to prevent possible leakage through the bridge 16.

An extendible slip member 20, as will be described later with reference to FIG. 2, is slidably disposed around the mandrel 11 and supported on a shoulder 21 formed around the mandrel a short distance above the upwardly facing shoulder 13 on the nose 12. An annular abutment 22 encircles the supporting shoulder 21 and is releasably secured thereto by one or more shear members 23. A frusto-conical slip-expanding member 24 is slidably disposed around the mandrel 11 and has a downwardly converging lower end complementarily tapered and received within the lower slip 20.

Elastomeric packing means 25 having its opposite ends coniined within cup-like anti-extrusion rings 26 and 27 (to be described subsequently with reference to FIGS. 3 and 4) is slidably disposed around the mandrel 11, with the `base of the lower ring 26 resting on the enlarged Y upper end of the lower expander 24. An upper expander 28, substantially identical to but oppositely directed' from the lower expander 24, isslidably disposed around the mandrel 11, with its enlarged lower end resting on the base of the upper anti-extrusion ring 27. An upper extendible slip member 29, identical to but oppositely directed from the lower slip member 20, is slidably disposed around the mandrel 11 and complementarily engaged over the upwardly converging upper end of the upper expander 23.

An annular setting head having a downwardly facing recess 31 is loosely disposed around the upper end of the mandrel 11 and arranged to be advanced downwardly by a setting tool against the upper slips 29 as it pulls the mandrel relatively upwardly therethrough. To secure the mandrel 11 against downward travel, locking means, such as a split expansible ring 32 having upwardly directed external and internal threads or

teeth

33 and 34, is disposed within the recess 31 and cooperatively engaged with complementary downwardly facing threads or teeth and 36 respectively formed around the mandrel and inner circumferential surface of the setting head 30. Resilient energy-storing means, as an O-ring 37, are disposed in the recess 31 and engaged between the setting head 30 and upper end of the ratchet ring 32 to urge the ring downwardly along the mandrel 11 during the setting operation. It will be noted that although the

teeth

33 and 34 on the ratchet ring 32 are upwardly directed, the upper surfaces of its external teeth are sloped slightly outwardly and downwardly. Moreover, a radial clearance is left between the crests and roots of

threads

33 and 36 that is sutiicient to permit the ring 32 to expand radially and disengage its internal teeth 34 from the mandrel threads V35. Thus, as the mandrel 11 is moved upwardly relative to the ring 32'and setting head 30, the mandrel threads 35 will serve as cams against the internal teeth 34 to expand the ring outwardly. As the ratchet ring 32 expands, its external threads 33 will be engaged with threads 36 more tightly and the

threads

34 and 35 momentarily disengaged. Then, once the internal ring threads 34 disengage from the mandrel teeth 35, the mandrel 11 will move upwardly and the resilience of the ring 32 will again contract it to re-engage the internal threads 34 with the next lower set of mandrel teeth. 1t will be understood, of course, that the external ring threads 33 are never totally disengaged from the setting head threads 36. Thus, as the mandrel 11 is pulled upwardly relative to the ratchet ring 32 and setting head 30, the ratchet ring 32 will alternately expand and contract to permit the mandrel threads 35 to pass upwardly through the ring.

As the ratchet ring 32 alternately expands and contracts, it will tend to shift upwardly relative to the setting head 30 as the

threads

34 and 35 are being disengaged. Each time it does so, however, the O-ring 37 will momentarily compress and then expand to advance the ratchet ring 32 downwardly relative to the mandrel 11 as soon as

threads

34 and 35 disengage. Thus, the O-ring 37 will function to momentarily allow the ratchet ring 32 to retrogress as it is being disengaged from the mandrel threads 35; but, once the O-ring is compressed, whenever the ratchet ring clears the mandrel threads, the O-ring will urge the ratchet ring downwardly and over the next lower set of mandrel threads.

To prevent rotation of the ratchet ring 32 relative to the setting head 30, a cylindrical pin 3S is loosely disposed in the gap 39 between the opposed ends of the ring. A longitudinal slot having a semi-circular cross-section is cut through the internal threads 36 in the setting head 30 for receiving the portion of the pin 38 projecting outwardly beyond the crest of the external ratchet-ring threads 33. Thus, with the pia 38 in position, it will be appreciated that the ratchet ring 32 will be unable to rotate relative to the setting head 30 but is still free for rotation and downward travel relative to the upwardly moving mandrel 11. It should also be noted that the loose iit of the pin 3S `within the gap 39-will not hamper the Y expand and contract as their associated expander 24 andV` 28 is respectively inserted and withdrawn therein.

Thus, as depicted in FIG. 2, a preferred embodiment is l shown of a slip member that has the above-mentioned capabilities of being selectively expandable and contractible. The expansible slip member 40 is an integral cylindrical member having a series of wickets or teeth, as at 101, disposed around its outer surface and a central bore which diverges outwardly toward one end to form a uniformly tapered inner surface, as at 102. To make the slip member 100 readily expansible, a series of

longitudinal slots

103 and 104 are cut radially through the wall at regular intervals around the circumference of the member to form a plurality of sectorial segments as at 105, 106 and 107. The

slots

103 and 104 are conversely alternated with one another so that slots 103 extend from one end or" the slip member 100 and terminate at radially directed bores 108 near the opposite end of the member. The other slots 104 are similarly formed but extend from the opposite end of the slip member 100 to their terminus at similar radially directed bores 109 near the first end of the member. Accordingly, the segments 105-107 are interconnected only by a series of alternated webs and 111 of equal cross-sectional area which respectively join Y one end of a particular segment 106 to the corresponding end of the adjacent segment 105 on one side and join the opposite end of that particular segment to the corresponding end of the adjacent segment 107V on the other side thereof. Thus, it will be appreciated that upon application of a laterally directed force on the tapered surface 102, this alternate arrangement of the

slots

103 and 104 will permit the slip member 100 to circumferentially expand as the several segments 105-107 move apart circumferentially and radially outwardly with the connectingwebs 110 and 111 acting somewhat as pivots.

It will be recognized, of course, that other arrangemen could be employed to make the

slips

20 and 29 radially expansible and contractible. By way of illustration, the

several segments

105, 106 and 107 of the slip member 100 could be separated, as by continuing

slots

103 and 104, and joining these segments by elastomeric strips (not shown) within the slots that are bonded on each side thereof to an adjacent segment. Similarly, such individual segments could be bundled together by one or more resilient springdike members.

Turning now to FIGS. 3 and 4, a preferred embodiment is shown of an anti-extrusion member 200 that may be used, as at 26 and 27, for conlining the opposite ends of the packing element 25. As depicted in these iigures, the

anti-extrusion ring 200 is an integrally formed, cup-shapedV expansible member having an annular base portion, as at 201, and a circumferentially expansible skirt portion, as at 202, extending upwardly around the periphery of the base portion. The skirt portion 202 is readily expansible by virtue of several imbricated finger-like segments, as at 203, 204 and 205, which are twisted slightly about their central axes and symmetrically arranged relative to one another so that one edge of each segment, as at 204, slightly overlaps the outer face of the segment 203 adjacent that edge, and the opposite edge of the segment 204 slightly overlaps the inner face of the segment 205 `adjacent that opposite edge. The outer or free end of each segment (204 for example) has an upwardly facing shoulder, as at 206, on that edge which overlaps the outer face of the adjacent segment 203 and a tab portion 207 on the opposite edge which overlaps the inner face of the segment 205 adjacent thereto. Each tab portion 207 is bent radially outwardly over the shoulder 206 of the segment adjacent thereto.

As seen in FIG. 1, the opposite ends of the elastomeric packing element 25 are received within such cup-

like rings

26 and 27 as shown in FIGS. 3 and 4 and, preferably, bonded thereto. Thus, when the packing element 25 is being displaced against the casing, radial forces will be applied uniformly in all directions against the inside of the anti-extrusion rings 26 and 27 by virtue of well-known tendencies of elastomeric materials to behave substantially as relatively non-compressive fluids. As these forces increase, the skirt portion (as at 202 in FIG. 3) will begin expanding radially outwardly. The radial movement will continue until the peripheral surface of the skirt portion 202 firmly engages the inner wall of the casing.

To insure that the

slips

20 and 29 remain in their retracted positions as the bridge plug is being positioned in a rough well casing as well as to control the sequence of setting the bridge plug, continuous rings or stop

bands

40 and 41 of a ductile material, such as brass, are disposed within peripheral grooves (as shown at 112 in FIG. 2) around the upper and lower ends of the lower and upper slips. These ductile rings 40 and 41 provide an additional restraining influence to the inherent resiliency of the slip members and 29 so that they will better withstand substantial accidental engagements as the bridge plug 10 is being maneuvered within a bell bore. Although it is preferable that the

stop bands

40 and 41 be at the thinner edges of the

slip members

20 and 29, it would be equally feasible to position them elsewhere around their respective member.

In addition to initially preventing premature expansion of the

slip members

20 and 29, it has also been found that, as they stretch, the

stop bands

40 and 41 continue to exert a uniform restraint as the slip members expand which insures that the slip segments move outwardly in unison. Thus, it will be appreciated that all slip segments (such as at 105, 106 and 107 in FIG. 2) will contact the casing at substantially the same time to centralize the bridge plug -10 as well as to insure that the outwardly directed forces applied against the casing will be substantially uniform.

Should the lower expander 24 encounter an obstruction as the bridge plug 10 is being lowered, it will be appreciated that there will be an upwardly directed force tending to foreshorten the packing element 25 which could, in some instances, expand the element at least partially against the casing. Thus, to avoid any upward movement of the lower expander 24 relative to the mandrel 11, a circumferential groove 42 is formed around the mandrel to provide a downwardly facing shoulder 43 at the upper end of the groove and a downwardly and outwardly diverging bevel 44 at the other end thereof. An expansible split-ring 45 is received within the groove 42 and normally disposed in the annular recess 46 formed in the upwardly facing end of the lower expander 24.

This lower stop-ring 45 is engaged with the upper shoulder 43 of the circumferential groove 42 to prevent the lower expander 24 from being accidently forced upwardly. On the other hand, in the usual setting operation, when the mandrel 11 is pulled upwardly relative to the lower expander 24, the beveled surface 44 of the groove 42 will expand the lower stop-ring 45 sutliciently to allow it to ride freely down the mandrel. The groove 42 could also be extended downwardly a sufficient distance to eliminate the beveled surface 44 and ring 45 would merely ride down the groove without having to expand. Thus, it will be appreciated that the mandrel 11 can be moved upwardly relative to the lower expander 24 but the lower expander cannot move upwardly relative to the mandrel.

Similarly, an expansible split-ring 47 is received within an annular recess 48 around the lower end of the upper expander 28 and a peripheral groove 49 formed in the mandrel 11 adjacent thereto. The upper groove 49 is reversely arranged from the lower groove 42 so that the shoulder 50 will prevent upward movement of the upper stop-ring 47 and packing element 25 relative to the mandrel 11. However, as the mandrel 1-1 begins to travel upwardly, the upper stop-ring 47 will be expanded outwardly in the same manner as the lower stop-ring 45 by the bevel 51 at the lower end of the upper groove 49 to free the mandrel for upward travel.

A continuous band 52 of ductile material, such as brass, is disposed around the upper stop-ring 47 to prevent its expansion until a predetermined force is applied thereto. In addition to controlling the sequence of setting of the bridge plug 10, it will be appreciated that should either the upper expander 28 or slip member 29 be struck while pulling the bridge plug upwardly while it is still retracted, if it were not for the stop-ring 47 and band 52, the upper expander 28 could shift downwardly to force the packing element 25 outwardly and possibly against the casing.

As in the case of the slip-

stop bands

40 and 41, the stopring band 52 is made of a particular predetermined strength so as to require a substantial force to expand the upper stop-ring 47, which force is still somewhat less than the required force applied to the setting tool (not shown) to set the bridge plug 10. The relative strength of the stop-ring band 52 with respect to slip-

stop bands

40 and 41 can, of course, be predetermined to vary the order of operation as will subsequently be explained in detail.

To set the bridge plug 10, a conventional setting tool (not shown) is connected to the bridge plug in the usual manner, with the outer sleeve of the setting tool being engaged on the upper face 53 of the setting head 30 and the inner mandrel of the setting tool coupled by a conventional shear stud (not shown) threadedly engaged in threads 17. Once the bridge plug 10 has been positioned at the depth it is to be set, the setting tool is actuated to pull the mandrel 11 upwardly as the setting head 30 is urged downwardly, then the shear stud will subsequently fail to disengage the setting tool whenever the applied forces reach the fail point of thestud.

As previously mentioned, various operational sequences can be obtained by varying the relative strengths of the stop-

rings

45 and 47 and the stop-ring band 52 with respect to the slip-

stop bands

40 and 41. Furthermore, the strength of the slip-

stop bands

40 and 41 can also be varied with respect to one another. Thus, the Various rings and bands disclosed herein eliminate the need for shear pin members as employed in prior art devices and can be used wherever shear pins appear.

It will be appreciated, of course, that as the setting tool applies an upwardly directed force on the mandrel 11 and the downwardly directed force on the setting head 30, the mandrel can not begin to move upwardly relative to the other elements until these forces have reached the predetermined magnitude sutlicient to stretch the stop-ring band 52 and allow the upper and lower stop-

rings

45 and 47 to respectively expand over the

bevels

44 and 51 of the

grooves

42 and 49. Thus, once the mandrel 11 is freed of the restraint of the stop-

rings

45 and 47, the oppositely directed forces applied by the setting tool will then be respectively directed against the bases of the

slip members

20 and 29 to 4begin forcing them upon their

respective expanders

24 and 28.

The preferred manner of operation is to make the stop ring band 52 somewhat stronger than the upper slip-stop band 41 but somewhat weaker than the lower slip-stop band 40. With this arrangement, the mandrel 11 will be initially held fixed relative to the upper expander 28 which will cause the Lipper slip member 29 to be driven downwardly over the upper expander whenever the applied forces reach a suicient magnitude to stretch the upper slip-stop band 41. After the upper slip member 29 has been fully expanded into anchoring engagement with the casing and the upwardly directed force on the mandrel 11 continues to increase, the stop-ring band 52 will then stretch suiciently to allow the upper stop-ring 47 and lower stop-ring 45 to ride up onto their respective

beveled surfaces

51 and 44 and free the mandrel relative to the

expanders

24 and 28. The continuing upwardly directed force will then move the mandrel 11 upwardly along with the lower slip member 20 and lower expander 24 to foreshorten the packing element 25 against the now firmly anchored upper expander 28 and slip 29 until the packing element is fully displaced into sealing engagement with the casing 54.

Although it is optional whether the lower slip-stop band 4t) is made stronger than the force -required to fully displace or expand the packing element 25 into sealing engagement, it is preferred to make it so to allow the packing element to be fully displaced before the lower slips 29 are fully expanded against the casing 54 to minimize the dragging of that slip member against the casing wall. In any event, once the

slips

20 and 29 are firmly anchored to secure the sealingly engaged packing element 25, the

' forces of the setting tool will continue to increase until the shear stud fails to release the setting tool for retrieval.

Accordingly, it will be appreciated that lonce the bridge plug 10 has been set in the position illustrated in FIG. 5, the packing element 25 will be securely compressed between the opposed slips 20 and 29 and can neither move upwardly or downwardly until these slips are released. Thus, until the

slips

20 and 29 are retracted, it will be understood that the bridge plug 1t) is permanently set.

Returning to FIG. l, it will be noted that the upper end of the upper expander 2S is relieved to provide an upwardly directed concentric recess 55 therein immediately adjacent to the mandrel 11. Furthermore, a circumferential groove 56 is formed around the mandrel 11 above the upper stop-ring groove 49, with this circumferential groove being appropriately located so as to remain below the concentric recess when the bridge plug 10 has been set. An expansible split-ring 57 having a normal relaxed diameter of the order of that of the concentric recess 55 is contracted and disposed into the circumferential groove 56; and, as the bridge plug 10 is being assembled, the expander 28 is disposed therearound to maintain the ring tightly contracted. The upper and lower faces of the ring 57 are preferably sloped downwardly and outwardly, as are their mating surfaces in the groove 56 and concentric recess 55, to provide more positive co-engaging surfaces.

It should also be noted by comparison of FIGS. l and 5 that so long as the lower slip member 20 is retracted, its base overlaps the upper surface of the mandrel shoulder 21; but, as the slip member is expanded over the lower expander 24, its base moves outwardly and is supported only by the annular abutment 22. It will be understood, of course, that the combined strength of the shear members 23 is suiiicient to withstand the forces required to set the bridge plug and release the setting tool.

Accordingly, to release the bridge plug 10 from the fully-set position as seen in FIG. 5, a tool (not shown) is coupled to the upper end of the mandrel 11. For reasons that will soon become apparent, this tool (or a combination of tools).must be capable of alternately imparting substantial upward and downward forces to the mandrel 11. Those skilled in the art will, of course, recognize that such forces could be supplied in any number of ways as, for example, by a setting tool coupled to a jar or by merely coupling a tubing string to the mandrel 11.

As seen in FIG. 6, once this tool or a tubing string is coupled to the mandrel 11, a substantial upward force 58 is applied to shear the shear members 23. Once these members 23 fail, the abutment 22 will fall and come to rest on the upper face 13 of the nose 12. By enlarging the mandrel 11,'as at 59, the abutment 22 will be coaxially aligned rather than skewed to avoid the possibility of its contacting an obstruction as the bridge plug 10 is re- 8 moved. It will be appreciated, of course, that the abutment 22 could be permitted to fall free of the mandrel 11 but it and other parts would leave objectionable debris in the well bore.

As the abutment 22 is released, the force 58 will dislodge the lower slip member 2i) as well. As it falls, the resilience of the slip member 2d will contract it to substantially its original position-Then, the lower expander 24- will be caught on the mandrel shoulder' 21 as the mandrel 11 is pulled upwardly. It will be seen that with the shoulder 21 supporting the expander 24, the expander can not move rfurther downwardly to re-extend the lower slips 20. Thus, inasmuch as the upper slips 29 willremain Vset as the force 58 is applied, the packing element 25 will be somewhat `further compressed as the mandrel 11 continues to move upwardly.

As the force 5S shifts the mandrel 11 upwardly rel-ative to the upper expander 28 (which is prevented from moving upwardly by the upper slips 29), the contracted ring 57 will be displaced above the upper expander and the setting head 30 shifted above the upper slips. Once the ring 57 is freed from the upper expander 28, it will expand to its normal diameter. Thus, as best seen in FIG. 7, by applying a shanp downward force 60 on the mandrel 11, t-he expanded ring 57 will strike the upper end of the expander 28 and drive it downwardly from under the upper slips 29. Once the expander 28 is freed from the upper slip member 29, the slips will return to substantially its original retracted position.

It will be recognized by comparison of FIGS. 5 and 6, that the expandable ring 57 must be slightly below the upper end of the upper expander 28 when the bridge plug 10 is `set (FIG. 5). Thus, when the mandrel 11 is pulled upwardly to release the lower slips 20 (FIG. 6), the ring 57 will stop at a position closer to the expander recess 55 than the spacing between the opposed surfaces of the setting head 30 and base of the upper slips 29. If this relative spacing -is not observe-d, the setting' head 30 will re-engage the upper slips 29 before the ring 57 can strike the upper expander 28. Moreover, as best seen in FIG. 7, this relative spacing must be arranged t-o permit the force 60 to shift the upper expander 28 `downwardly relative to the Vstill-iixed upper slips 29V a sucient distance to enable the upper slips to retract before the setting head 30 re-engages them.

With the upper slips 29 retracted, the bridge plug 10 is ready to be retrieved. Accordingly, as depicted in FIG. 8, the mandrel 11 is pulled upwardly and the bridge plug 10 removed from the well. It will be noted that although the anti-extrusion rings 25l and 27 may still Ybe partially expanded, they will not .present a material drag to prevent the retrieval of the bridge plug. i

Accordingly, it will be appreciated that the present invention has provided a new `and improved well tool such as a ibridge plug or a packer that is capable of being firmly set in a well bore to withstand substantial pressure differentials acting in either direction. Then, at. -any subsequent time, the well tool is easily released to a retractedV position land is capable of bein-g retrieved.

While a particular embodiment of the present invention has been shown and described, it is apparent that changes and modifications may be made without departing Vfrom said invention in its broader aspects; and, theret fore, the aim in the appended claims is to cover all suoh changes and modifications as fall within the true spirit and scope of this invention.

I claim:

1. Well apparatus comprising: a bodyg'rneans for anchoring said apparatus including first and second normally-retracted opposed slip members; means responsiveV to -force in a predetermined direction on said body for extending said slip members; means responsive to force on said body in said direction for permitting retraction of said lirst slip member; and means responsive to move- 9 ment of said body in the opposite direction for permitting retraction of said second slip member.

2. Well apparatus comprising: a body; means for anchoring said apparatus including first and second opposed expander .means slidably mounted on said body and first .and second normally-retracted opposed slip means respectively cooperatively arranged on said expander means and relatively slidable lthereon toward one another from retracted positions to extended positions; means releasably restraining said expander and slip means Ifrom sliding relative to one another and releasable in response to a first force in a predetermined `direction on said body for freeing said slip means for sliding relative to said expander means to said extended positions; means between said body fand first slip means releasably retaining said first slip means on said first expander means and releasable in response to a second greater force in said direction on said body 'for releasing said rst slip means from said first expander means for return to its said retracted position; and means responsive to la third force in the opposite `direction on said body for releasing said second slip means from said second expander means.

3. Well-packing `apparatus comprising: a body member; means for anchoring said lapparatus lincluding first and second opposed expander members spaced apart and slidably mounted on said body member and first and second normally-retracted opposed slip members respectively cooperatively arranged on said expander members and slidable thereon toward Ione another from retracted positions to extended positions; expansible packing means on said body member .between said expander members and ladapted to be foreshortened and expanded therebetween into sealing engagement with a wall surface in la well bore; means between one of said expander members and an 'adjacent one lof said members releasably :restraining said two members from sliding relative to one another, said restraining means being releasable in respouse to a first longitudinal force in a predetermined direction on said tbody member for extending said slip member and foreshortening said packing means; retainer means on said body member normally maintaining said first slip -member on said first expander member and releasable in response to a second Igreater longitudinal force in said direction on said body member for freeing said first slip member from said first expander member for return to said retracted position; and means to enable yreturn of said second slip member to said retnacted position.

4. Well-packing apparatus comprising: a body member; means for anchoring said apparatus including first and second opposed expander members spaced apart and slidably mounted on said body member and first and second normally-retracted opposed slip members respectively cooperatively arranged on said expander members and slidable thereon toward one another from retracted to extended positions; expansible packing means on said body member between said expanders and adapted to be foreshortened and expanded therebetween into sealing engagement with a wall surface in a well bore; means between said first expander member and an adjacent one of said members releasably restraining said adjacent members from sliding relative to one another, said restraining means being releasable in response to a first longitudinal force in a predetermined direction on said body member for extending said slip members and foreshortening said packing means; retainer means on said body member normally maintaining said first slip member on said first expander member and releasable in response to a second greater longitudinal force in said direction on said body member for retracting said first slip member; and means on said body member and responsive to a third force in the opposite direction on said body member for shifting said second expander in said opposite direction and away from said second slip member for retracting said second slip member.

5. Well apparatus comprising: a body having stpp means thereon; means foranchoring said apparatus including an expander member slidably mounted on said body member and a normally-retracted slip member between said stop means and expander member, said slip member being slidably engaged with said expander member and cooperatively arranged to be urged outwardly thereby from a retracted position abutting said stop means to an extended position laterally displaced from said stop means as said members are advanced toward one another; and means normally engageable with said slip member in said extended position for maintaining said slip member in engagement with said expander member and responsive to a predetermined -force for releasing said slip member from engagement with said expander member.

6. The apparatus of claim 5 further including means releasably securing said slip member in a retracted position and releasable n response to a lesser force than said predetermined force.

7. In well-packing apparatus including a body, opposed lower and upper expanders slidably mounted on said body, opposed lower and upper slip members respectively engaged with said expanders and slidable thereon from retracted to extended positions, and expansible packing means on said body between said expanders `and adapted to be foreshortened therebetween as said body is shifted upwardly relative to said upper expander and slip member, the improvement comprising: first abutment means normally engaging said lower slip in said retracted position and normally disengaged therefrom in said extended position for maintaining said slip against said lower expander; second abutment means releasably engaging said lower slip in said extended position and responsive to a predetermined upward force on said body for releasing said slip from said expander; and third abutment means on said body normally constrained between said body and upper expander and expansible upon upward travel of said body relative to said expander to provide a shoulder for engaging said expander upon subsequent downward travel of said body relative to said expander.

8. A well tool for packing off' a well bore comprising: a mandrel; upper and lower normally retracted slip means movable to expanded position for anchoring against movement in a well bore; normally retracted packing means for packing off the well bore; first and second expander means for expanding said slip and packing means into anchoring and sealing engagement with a well bore Wall; means for retaining said slip and packing means in expanded condition; and means for releasing said retaining means to permit retraction of said slip and packing means including a rst member which is releasable in response to a predetermined force in one longitudinal direction on said mandrel to permit movement of one of said slip means relative to said mandrel to retracted position, said releasing means further including a second member on said mandrel engageable with one of said expander means for moving said one expander means with said mandrel in the opposite longitudinal direction to permit movement of the other of said slip means to retracted position.

9. A well tool arranged to be releasably anchored in a well bore comprising: a body member; expander means slidable on said body member; normally retracted slip means engageable by said expander means to be shifted outwardly to expanded position by said expander means; abutment means on said body member engageable with said slip means for supporting said slip means in expanded position; and releasable means between said body member and abutment means operable in response to manipulation of said body member for permitting longitudinal movement of said abutment means away from said expander means and movement of said slip means to retracted position.

10. A well tool arranged to be releasably anchored in a well bore comprising: a body member; expander 1i r2 means on said body member; normally retracted slip y i References Cited means moveable relative to said expander means to be UNITED STATES PATENTS shifted outwardly to expanded position by said expander means; and means for moving said expander means Iela- Y lsgvlerl lg'gg tive to said slip means in a manner to permit retraction 5 3036636 5/1962 Cclarge -f 166:12?, of said slip means including recess means in said body 3244233 4/1966 VillalO- 6 173 5X member adjacent to said expander means, and expansible 3270819 9/1966 Thrane et'gl 166 135 X meansin said recess means capable of engaging said ex- 313033885 2/1967 Kisling 166 134 pander means to couple said expander means to said body member for movement therewith in a direction to 10 CHARLES E O CONNELL Pnmay Exammer enable retraction of said slip means. DAVID H. BROWN, Examiner.