US2753942A - Bridging plug - Google Patents

Description

July 10, 1956 J. T. GARDINER 2,753,942

BRIDGING PLUG Filed July 23, 1948 2 Sheets-Sheet 1 40 y 38 ea 9 35 27" 12 45 45 11 2? 22 INVENTOR.

July 10, 1956 J. T. GARDINERI BRIDGING PLUG 2 Sheets-Sheet 2 Filed July 23, 1948 4%? &

INVENTOR. JOHN Z GAQD/NEQ,

197' TOENEY.

U ed Sara 2,753,942 BR 1D 'GING PLUG John T.. Gardiner, Long Beach, Calif., assignor, by Inesne assignments, to Lane-Wells Company, Los Angeles, Calif., a corporation of California Applicifibn July 23, 1948, serial No. 216,152 11 Claims. (Cl. 166-123) I This invention relates generally to well packing devices and more particularly to bridging plugs and the like apparatus adapted to be set within well boreholes and casings. V n

Packer devicesparticularly of the bridging type are usually employed for the well knownpur'pose of closingtor sealing off a lower portion ofthewell orto separate upper and lower sections t ereo f for various purposes. Such bridging or plugging oprationsare often employed, for example, when a lower zone in an oii, well has ceased to be sufiiciently productive, or where the well bore has been found to extend into water producing zone or thief sands, or for any other reason it beco nes desirable to plug back or close-ofi a lower zone or portion of the well and produce from .a higher zone in the well. In some such cases where the bottom zone into w'hich a well has been drilled fails or ceases to be sufi'iciently productive, it may be desirable to explore and tes t a number of higher zones in relatively rapid succession for their possible productivity and this may require pluggingoperations for each such test. e a Heretofore the process and apparatus required, for lowering, positioning and setting bridging plugsin weils and for releasing the setting tools has been, nioretin e; consuming than is desirable, particularly in extrernely deep wells of the present day. Suchbridgingplugs after being. set must be capable of ithstandingtremendMS differential pressures without displacement and with x as little leakage as possible. In addition to these qualities, it is desirable that such bridging plugs be capableof being set by suitable setting tools exerting relatiyely low setting forces and at the same time becapableo'f being run into fluid-containing, deep well bores at relatively high speed without the packing body caused by the resultant fluid forces and pressures to expand and set the plug prematurely at some undesirable point in thewell. n v V In bridging plugs of the usual type employing double ended packing sleeves and a pair of sets of oppositely acting casing gripping devices such as serratedslipsi it frequently happens that premature setting of he plug in the well occurs ,as a result of exceeding'a of lowering the plug into the well. Such premature settingof ,the plug has been found to be caused, in s on e cases, by the pressure and fluid forces exerted upquthe packer body by the relatively high velocity of fiow of fluid around and past the plug as it is lowered therethrough ,or, in other cases by shocks or ac ieratign forces caused by sudden changes of lowering' rate jattendant upon impact of the plug with a fluid surface or with sand bridges or other obstructions the vvellr in an effort to improve the holding ability of bridging plug packings and to render them practically non-leaking the packing sleeves have often been constructed in such manner as to be substantially free-floating up on the blo dynr mandrel of the plug and formed in such rnanner'asjco tend to be self-sealing by the action of the differential fluid pressure impressed across them after being" initially expanded.

' yslq tr lative,

However, by sodoin'g', such packing devices have been rendered rnoreqsusceptible ,to premature setting in the weils as hereinbeforer:mentioned. Such premature setting o'f a, b idgingplug.in a well is usuallyextremely iirne consuming andexpensive often requiring that the P h t iq djb' d n -1 r It is,. a'ccordi ngly, an object of this invention tofprovide a bridging plug in which many of thesundes'irable and limiting features heretofore prevalent in briding ,plugs and the like packeriapparatus have been eliminated.

'It is also an object to providea bridging plug of novel and improved construction which, will be resistant to premature pack-o if and setting by the effects of high to the fluid in the bore hole ,or by acceleratipn ,forces to which it may be subjected during lowering a well borehole. v .t It is further object ofthis invention to .provide :a Wi l? fssnluswh h will a mp v holding and sealing capabilities under high differential pressures. The 'gbjetgts of the invention are accomplished,v in en ra br n. im' oys Pea n l eve p k expander andpacker body design in which the said sleeve-is so formed as to be set withrelatively low setting, force yet Is ue sdsp at s a e b d n such. n as to be less s e'ptible to undesirable d iOlmation and preg under the hydraulic', .inertia and frictional throughout the several. views s Figure l is a longitudinal elevational view of lhe gen eral assembly of the bridging pIug as .it appears, when assembled ready, to be lowered into a well, or when being lowered or suspended within a well casing just prior to setting. V I I d H Figure 2 is a longitudinal sectional view of theapparatus of Figure l showing its assembled appearance and i gs art but pr to Settingcin a c i Figure 3 is alon'gitud'inal sectional view of the, apparatus showing its, appearance and positions of its parts just after completion of setting in a lcasing v v, V

I Fig'urejl is an enlarged longitudinal sectional view of a fragmentary portion of the central part of the bridging plug.

'IIhe apparatus is as follows; H

is Referring now to the drawings and primarily toliig- 'ures 1 2 and 4, the rrain structure ofthe apparatus comprises a centrally located, elongated, tubular body or mandrel 10 of substantially uniform. external diameter hg t ti en th and l erm a ng at ts lower e "in a nose piece or shoe member 11 of slightly, increased q e l u wa y. fa in la h ul being h q ms js tlt l c q .Q .s lm n rel ya d 'saidshoemember, A plug 2) threadedinto the bottom of the shoe 11 closes a threadedopening which may be employed for attachment of other apparatus such as, for exarnple,' a lower string of tubi'ngor a circulating valve not shown A At a lower intermediate ,portion, the mandrel is formed with ashortsection 13 of slightly reduced diameter serving as a groove about which a split ring 14 is placed and is retainedtherein with freedom for liini tedlong'itudinal sliding motion to .act as-a means for retaining an annularpac'king body 37 in place and inproper longitudinal position upon the mandrelas more fully described hereinafter. At an upper intermediate portion of the external cylindrical surface-of the mandrel a length of downwardlytacing ratchet grooves or buttress threads 16 is provided, and these grooves or threads are adapted to ratchet through and make one-way locking engagement with a correspondingly toothed split lock ring 17. The lock ring 17 is retained in an inwardly facing, annular groove formed between upper and lower, threadedly interconnected halves 18 and 19 respectively, of a lock ring adapter fitting 20 hereinafter also more fully described. A shallow annular groove 21 is formed in the upper portion of the mandrel adjacent the upper end thereof which serves as a detent to receive the inner toothed portion of the lock ring 17 when the packer is in the unset condition as illustrated in Figures 1 and 2.

The upper end of the mandrel 10 is provided with internal threads 23 into which a relatively short, externally threaded connector sleeve 24 is screwed.

A plurality of lower, wedge shaped slips 25 having downwardly facing serrations or wickers are normally positioned about a lower, upwardly diverging slip cone 35 carried upon the lower end of the mandrel 10 as best shown in Figure 2 and retained there by a slip retainer ring 26, attachment between each of said slips and said retainer ring being effected by a dove-tail interconnection comprising a radially directed dove-tail slot 27 formed in the upper face of the retainer ring 25 into which a time tail 28, formed on the lower base end of the slip, fits and has limited freedom for radial sliding motion therein to permit radial expansion of the slip.

A like set of upper slips 32 having upwardly facing serrations is provided about an upper, downwardly diverging slip cone 36 carried upon an intermediate portion of the mandrel 10 adjacent the lower end of the beforementioned lock ring adapter fitting and these slips are similarly provided as shown at 33 with dovetail connections to the lower half 19 of the lock ring adapter fitting 20, permitting radial expansive movement of said slips.

Intermediate the beforementioned sets of upper and lower slips are the beforementioned lower, upwardly diverging slip cone 35, the upper downwardly diverging slip cone 36 and the resilient, sleeve shaped packing element 37 positioned intermediate the said slip cones, all longitudinally slidably retained upon the mandrel 10 except as initially restricted by various releasable interconnecting means hereafter described. The upwardly facing base end 38 of the lower slip cone 35 and the downwardly facing base end 39 of the upper slip cone 36 serve respectively as lower and upper abutments or expander rings between which the resilient packer element 37 is retained and in operation is adapted to be compressed longitudinally for deformation or expansion radially into sealing engagement with a surrounding borehole wall or casing.

The bore of the packing sleeve 37 is formed or molded with an inner annular groove 40 adjacent its lower end to receive the outer portion of the hereinbefore mentioned retaining ring 14. The retaining ring 14 which is made of a suitable metal, preferably a metal such as brass or cast iron which may be easily drilled-up is usually placed in the molded groove in the packer body after its manufacture although it may, if desired, be placed or molded in place in the packer body at the time of its manufacture and thus in the latter case may be firmly bonded thereto to form a unitary part thereof.

Several of the lower slips are provided with a posltioning pin fixed therein as shown at 41, having its inner end extending with a relatively loose fit into a shallow annular groove formed in the mandrel as shown at 42. Each of the slips of both the upper and lower set of slips is initially anchored to the slip cone face upon which it slidably bears, by means of a shear pin or screw as shown respectively at 43 and 44.

The lower set of slips 25 is urged upwardly by means of a plurality of coil springs 45 retained in circumferentially spaced holes extending axially through the flanged or shouldered portion 12 of the nose piece 11. and each 4 acts under compression between the lower face of the slipretainer ring 26 and a threaded, spring-retainer plug as shown at 46.

As best shown at Figure 4, the lower packer-abutting end 39 of the upper slip cone 36 which as beforementioned serves as an upper abutting member or expander ring for the packing sleeve, is formed with a short counterbore 48 preferably having, as viewed in the drawing, an outer or lower cylindrical entrance portion 51 of uniform inside diameter, an intermediate portion 53 of inwardly or upwardly diverging tapered form and an inner or upper end portion terminating in a chamfer or upwardly converging conical shoulder 49. The counterbore may be formed, if desired, with a uniform diameter throughout its depth with satisfactory results in operation. In either construction it has been found to be advantageous to have an outer portion of the recess of uniform diameter for a sufiicient depth to permit the outer lip portion of the packing body to move freely into packing position between the outside of the slip cone and the inside surface of the casing as hereinafter more fully described. The outer, lower end portion of the slip cone surrounding the before-mentioned counterbore is formed with a downwardly converging conical surface as shown at 50 terminating at its intersection with the inside cylindrical surface 51 of the counterbore 48, in a downwardly directed, relatively sharp, beveled edge 52.

The upper, adjacent end of the resilient packing sleeve 37 is preferably formed with an outer conical end portion 54 or corresponding slope and adapted to fit and normally abut the before-described conical surface 50 of the slip cone 36. The packing sleeve is also provided with a longitudinally directed cylindrical slit 55, commencing at the inner terminus of the conical end surface 54 of the packer and extending longitudinally and coaxially inward or downward as viewed in Figure 4, for a short distance preferably along a cylindrical surface formed by the downward projection of the inside cylindrical surface of the slip cone counterbore 48. A pair of separate, concentric, annular projections or lips are thus formed on the upper end of the packing sleeve, separated from one another by the slit 55, but joined together at the inner terminus thereof, the inner annular lip 56 being positioned at the entrance to the counterbore 48 and initially projecting a short distance within the outer cylindrical portion 51 and thereby being in position to be wedgingly thrust into the inner tapered portion of the annular space within the counterbore 48 around the packer mandrel. The upper end of the said inner annular lip 56 is preferably, although not necessarily, formed with a conical or beveled end as shown at 58 adapted to fit the chamfered end 49 of the annular recess 48 when the packing is fully set as illustrated in Figure 3. The outer annular lip portion 57 of the packing sleeve is likewise in position to be expanded over the beveled surface 54 and thrust into the outer annular space formed between the outside surface of the lower end portion of the slip cone 36 and the inside surface .of a surrounding casing as, shown in Figure 3, upon application of longitudinal compressive force to the packing sleeve 37. The lower circumferentially overlapping ends of the slips 32 serve to seal off the upper end of this outer annular space into which the packer is thrust as shown in Figure 3.

Referring now primarily to Figure 2, a lower fragmentary portion of a tubular ram adapter sleeve of a setting tool is shown at 60 extending upwardly from a separable coupling connection 61 located at the top of the bridging plug locking ring adapter fitting 20.

A lower tubular strut portion of the setting tool is also shown fragmentarily at 79. Adjustably threaded into internal threads formed in the lower end of the strut portion 79 of the setting sleeve is a short, externally threaded connector member 84 the lowermost unthreaded end portion ofv which extends or plugs into the top openitig of the beforementioned connector sleeve and is secured there by means of a shear 84a which extends crosswise through holes drilled through both the connector sleeve 24 and the connector member 84. The adapter sleeve 60 and the setting sleeve strut 79 may comprise the outer sleeve extension of the cylinder and the inner piston parts respectively of a setting tool of any suitable type, for example, as disclosed respectively at 60 and '79 in Forsythet al. Patent N0. 2,566,323, at 11 and 13 in Spengler 2,326,404 or at 6 and 16 in Batchelder 2,382,770.

A shear pin 96 making a light driving fit through a drilled hole in the lower end portion of the adapter sleeve '60 extends into an aligned, drilled hole or socket formed in the upper end of the mandrel The shear pin 96 serves as a means for initially positioning and locking the packer mandrel relative to the setting mechanism and to support the Weight of the sleeve -6i) and other portions of the setting tool thereabove which mightotherwise tend to force the upper slips 3?. and slip cone 36 downward against the packer sleeve 37 and thus tend t6 cause premature setting of the packer.

The operation is as follows:

In running in and setting the bridging plug apparatus of this invention the bridging plug, assembled as shown in Figures 1 and 2 is lowered into the borehole upon a suitable setting tool as hereinbefore nientiOned to the point at which it is desired to bridge the well. Setting force is then applied to the bridging plug from the setting tool, an upward tension being thereby transmitted through the setting strut 79, the connector member 8 and thence through the shear pin 84a and the connector sleeve 24 to the top' of the bridging plug mandrel '16) such upward tension being balanced by an equal down-ward, eompres siv'e force applied from the said setting tool through the adapter sleeve 60 and coupling 61 to the body of the bridging plug. The upward force thus applied to the bridging plug mandrel it) tends to move the said mandrel 10 upward with respect to the adapter sleeve 60 to a position such as that illustrated in Figure 3. However, shear pin 95 initially resists such relative motion until the upward force applied to the mandrel 10 reaches a value equal to the shearing strength of the pin. Upon'shea ring of the pin 96 the upward force thus applied to the bridging plug mandrel 1G is suddenly transferred downward through the lower portion of the mandrel to the nose or slide 11 and from there is transmitted upward from the shoulder 12 through the bottom slip retainer ring 26, lower slips 25, shear pins or screws 43', lower slip cone 35, packing element 37, upper slip cone 36, shear pins or screws 44, upper slips 32', and thence through the lock ring adapter fitting 19 and 2t) and the coupling 61 to the adapter sleeve 6% of the setting tool. The force thus applied after first shearing the positioning pin 96 next results in shearing of the upper slip shear screws 44, followed soon thereafter by the shearing of the lower slip shear screws 43, thereby permitting the upper and lower slips 32 and 25 to move outward upon the sloping surface of their respective slip cones 36 and 35 into gripping engagement with the inside surface of the well casing. Following this and upon further application of the upward force through the mandrel 10, the slip cone 35 is' caused to move upward relative to the slip cone 36 a distance sufficient to thrust the inner annular "lip 56 firmly into the annular recess 43 to form a fluid-tight seal between the inside of the slip cone 36 and the surface of the mandrel lid and at the same time to expand and thrust the outer hp 57 out and into the annular clearance Space formed between the outside surface of the .slip cone and the inside of the surrounding casing and to some 6mm compressing laterally and thereby deforming the resilient or deformable packing sleeve 37 into sealing engagement with the inside surface of the surrounding casing, all as best illustrated in Figure 3. In so doing as before stated, the inner annular'lip 56 of the upper end of the packing is' fir-st thrust farther into the tapered annular recess 48 from the initially entered position shown in Figures 2 and 4 to that shown in Figure 3 to form a tight fluid seal between the hereof the slip cone 36 and the outside surface of the inandre'l l0 and at the same time firmly anehor the upper end of the packing sleeve to the end of the slipcone, against radial displacement or pulling away from the mandrel, both before and after the setting operation. A particular feature-of this invention resides in this arrangement whereby the inner annular lip 56 of the packing sleeve is initially entered into the annulus 43 prior to setting whereby rolling up, radial expansion or over-riding of the adjacent end of the slip coneby the packing sleeve material is avoided upon subsequent application of longitudinal settingpressure to the packing sleeve either inadvertently during lowering in a well or intentionally during normal setting operations. 7 7

At the same time, while the inner annular lip of the packing sleeve is being thrust into the annulus 48, as before-described, the outer annular lip 57 is divided therefrom along the slit 55 by the beveled end '52 of the slip cone and thereby expanded and thrust into the annul'ar clearance space surrounding the outside surface of the slip cone 36 and the inside surface of the surrounding casing to form a fluid tight seal=therebetween, as shown in Figure 3; The principal sealing effect of the packing sleeve thus occurs at upper end portion of the packing sleeve adjacent to and surrounding the lower end portion of the upper slip cone 36. This type of seal has been found to possess so-called self-sealingcharacteristics such that fluid pressure differentials in either direction across the plug tend to set the packing seal more firmly the greater such pressure may be. 1

Another important feature of .this invention resides in the employment of the retaining ring 14 adjacent the lower end of the packing sleeve. Initially prior to setting the packer it is to be noted thatthe retaining ring 14 occupies its uppermost possible position in the ring groove 13 of the mandrel 10. The packing sleeve is thus initially anchored to the mandrel 10 against upward motion thereon prior to setting, and is thus prevented from being forced upward against the abutting end of the upper slip cone 36 when lowered at highspeed through well fluid in a well or by frictional contact with obstructions in the well and is thereby prevented from being prematurely expanded. The forming of the packing sleeve with a fiat or square cut lower end as shown at 38 also assists in preventing the development of combined radial and upwardly directed forces, both mechanical and hydraulic, tending to move the packing sleeve upward and outward intosetting position.

The hereinbefo're described arrangement results in a packing which has the highly desirable characteristics of being readily deformed and thus sensitive to setting pressures and therefore capable of being set to form a good fluid seal in the well with relatively low setting forces, while at the same time being relatively insensitive to high running-in speeds in fluid-containing wells and the effect of obstructions and the like difficulties.

The location of the retaining ring '14 near the lower end of the packingsleeyeisadvantageous in preventing the packing sleeve from being subjected to longitudinal compression by fluid forces or frictional contacts to which it may be subjected during running-in operations as would be the case with the ring located in a higher position. With the retaining ring 14 positioned adjacent the lower end, the packing body is placed in longitudinal tension by any upward drag from the fluid or other frictional effects during such operations. g g

At this stage in the before-described setting p rocess the bridging plug mandrel 10 will have been mouedvupward relative to the'lock ring adapter fitting 291a distance sufficient to carrythe ratchet grooves or buttress threads 16 of the mandrel upward through and into locking engagement with the lock' ring 17. The bridging plug is thereby locked in the set condition within the casing with both the upper and the lower sets of slips 32 and 25 in holding engagement with the inside surface of the casing as shown in Figure 3.

After setting the apparatus in the casing as hereinbefore described, continued and increased setting force is applied from the setting tool finally resulting in the shearing of the pin 84a thereby resulting in the disconnection and separation of the setting strut 79 and the associated connector member 84 from the connector sleeve 24 permitting the entire setting tool including the setting tool ram which bears upon the ram adapter sleeve 60 to part from the briding plug at the separable joint therebetween, not shown and to be withdrawn from the well, leaving the bridging plug set in the casing. If desired a set of jars of any well known type such as, for example, that shown in the United States patent to H. C. Otis, No. 1,920,103, may be placed immediately above the setting tool to facilitate this latter disconnecting operation. The several retainer members, shear pins and screws hereinbefore mentioned are designed to shear in the order named, namely, first the pin 96, followed by screws 44 and 43 and finally pin 84a. Normally pins 41 are not sheared but merely move outward laterally with the lateral motion of the slips 25, thereby simply withdrawing the inner ends of the pins from the groove 42 in the mandrel. The pins 41 serve, prior to setting of the packer to hold the slips 25 retracted and bottomed against the shoe shoulder 12 against the upward force of coil springs 45. The force of the coil springs 45 is thus prevented from being applied against the bottom of the packing sleeve 37 prior to the setting operations which might otherwise result in premature setting of the packing sleeve and lower slips during lowering of the device into the well.

Ordinarily the lower slips 2S and their retaining ring 26 remain, before and after setting, bottomed upon the upper surface of the shoulder 12 of the shoe 11. However, in event movement of the plug should occur after setting such that the resultant relative motion between the lower slip cone 35 and the shoulder 12 tended to release the lower slips 25, then the coil spring 45 would force the said slips to follow any such motion of the slip cone and remain in wedging position between the slope of the cone and the inside surface of the surrounding casing.

In a bridging plug of the type herein disclosed substantially all of its principal parts are preferably constructed of materials which are relatively easily drillable by ordinary well drilling tools whereby the bridging plug after being set can, if necessary, be removed by drilling. All of the parts except the packing sleeve and the small springs are therefore preferably made of soft metals such as cast iron, brass and the like. The packing sleeve may be molded rubber, preferably a synthetic rubber such as neoprene resistant to the solvent effects of petroleum and having a shore hardness of approximately 60.

It is to be understood that the foregoing is illustrative only and that the invention is not limited thereby but may include various modifications and changes made by those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

I claim:

1. In a bridging plug: a mandrel; an expander body encircling said mandrel and formed with a counterbore extending upwardly from the lower end thereof, said counterbore defining with said mandrel a coaxial annular recess; a packing sleeve encircling said mandrel below said expander body and having a concentric cylindrical slit extending axially downward from the upper end thereof adjacent said expander body and dividing said packing sleeve end into inner and outer concentric annular lips joined together at the lower termination of said slit; and means positioning said packing sleeve on said mandrel relative to said expander body initially with the upper end of said outer annular lip in end to end abutment with the lower end surface of the portion of said expander body surrounding the entrance to said annular recess and with the upper end portion of said inner annular lip extending partially into the said annular recess.

2. In a bridging plug: a mandrel; an expander body encircling said mandrel and formed with a counterbore extending upwardly from the lower end thereof, said counterbore defining with said mandrel a coaxial, annular recess and the lower end portion of said expander body surrounding the entrance to said annular recess being beveled in an upwardly diverging direction with respect to the entrance to said recess; a packing sleeve encircling said mandrel below said expander body and having a concentric cylindrical slit extending axially downward from the upper end adjacent said expander body and dividing said packing sleeve end into inner and outer concentric annular lips joined together at the lower termination of said slit, said outer annular lip terminating at its upper end in a downwardly converging beveled end surface; and means positioning said packing sleeve relative to said expander body initially with the upper bevel of said end of said outer annular lip in abutment with the bevel of the said lower end portion of said expander body surrounding said annular recess entrance and with the upper end portion of said inner annular lip extending partially into the said annular recess.

3. In a bridging plug: a mandrel; an expander body encircling said mandrel and slidable longitudinally thereon said expander body being formed with an inwardly tapering counterbore extending inwardly from one end thereof, said counterbore defining with said mandrel a coaxial annular recess; a packer sleeve encircling said mandrel and having one end flat and in the other end a concentric, cylindrical slit extending axially inward from the end adjacent said expander body and having a diameter substantially equal to the maximum inside diameter of said annular recess, said slit dividing the end portion of said packing sleeve into inner and outer concentric annular lips joined together at the inner termination of said slit; means positioning said packing sleeve relative to said expander body initially with the outer end of said outer annular lip in end to end abutment with the end portion of said expander body surrounding the entrance to said annular recess and with the outer end portion of said inner annular lip extending partially into the said annular recess; and anchoring means adjacent the said flat end of said packing sleeve associated with said packing sleeve and said mandrel to limit the longitudinal sliding motion of said packing sleeve relative to said upper expander body.

4. In a bridging plug: a mandrel; an expander body encircling said mandrel; a packing sleeve encircling said mandrel and positioned in end to end abutment with said expander body; releasable means to lock said expander body against longitudinal movement on said mandrel toward said packing sleeve; means to lock said packing sleeve to said mandrel with freedom for limited longitudinal sliding motion thereon, said last mentioned means preventing said packing sleeve initially from being forced against the abutting end of said expander body with sufficient force to deform said packing sleeve; and means to release said releasable means to permit said expander body to be moved into forceful engagement with the abutting end of said packing sleeve.

5. In a bridging plug: a deformable tubular packing sleeve, one end of said sleeve being flat and lying substantially in a plane perpendicular to the longitudinal axis of said sleeve and the other end of said sleeve being formed with a concentric cylindrical slit extending axially inward from the said end thereof and dividing the said end portion of said sleeve into inner and outer concentric annular pressure lips joined together at the inner 9 termination of said slit; an inwardly facing ,aiml 'lar groove formed in the bore of said sleeve adjacent the flat end thereof; and a ring in said groove, said ji'ing having a radial thickness greater than the depth of said groove.

6. In a bridging plug: a deformable tubular packing sleeve, the lower end of said sleeve being flat and lying substantially in a plane perpendicular to the longitudinal axis of said sleeve and the upper end of said sleeve being formed with a concentric cylindrical slit extending axially inward from the said end thereof and dividing the said end portion of said sleeve into inner and outer concentric annular pressure lips joined together at the inner termination of said slit; an inwardly facing annular groove formed in the bore of said sleeve adjacent the fiat end thereof; a ring in said groove, said ring having a radial thickness greater than the depth of said groove; a mandrel extending through said packing sleeve, an axially elongated groove formed around said mandrel with said ring extending into and longitudinally slidable therein; an expander body initially fixed to said mandrel and abutting the upper end of said packing sleeve, said groove and said expander body being located relative to one another initially with said ring positioned at the upper extremity of said groove to prevent said packing ring from being forced upwardly on said mandrel into forceful engagement with said expander body but permitting said mandrel to be moved upwardly relative to said packing sleeve for a distance determined by the length of said groove.

7. In a bridging plug: a mandrel; upper and lower expander bodies on said mandrel and slidable longitudinally relative to one another, the lower expander body being formed with a substantially flat upwardly facing end surface and the upper expander body being formed with a counterbore extending upwardly from the lower end thereof said counterbore defining with said mandrel a coaxial annular recess; a packing sleeve encircling said mandrel intermediate said expander bodies and having the lower end thereof substantially fiat and adapted to abut the said upwardly facing end surface of said lower expander body and in the upper end of said packing sleeve a concentric cylindrical slit extending axially downward from the upper end thereof adjacent said upper expander body and having a diameter substantially equal to the inside diameter of said annular recess, said slit dividing the upper end portion of said packing sleeve into inner and outer concentric, annular lips joined together at the lower termination of said slit; and means positioning said expander bodies relative to said packing sleeve initially with the lower end of said packing sleeve in abutment with the upper end of said lower expander body and with the upper end of said outer annular lip of said packing sleeve in end to end abutment with the lower end portion of said upper expander body surrounding the entrance to said annular recess and with the upper end portion of said inner annular lip extending partially into the said annular recess.

8. In a bridging plug: a mandrel; upper and lower expander bodies on said mandrel and slidable longitudinally relative to one another, the lower expander body being formed with a substantially flat upwardly facing end surface and the upper expander body being formed with a counterbore extending upwardly from the lower end thereof said counterbore defining with said mandrel a coaxial annular recess; a packing sleeve encircling said mandrel intermediate said expander bodies and having the lower end thereof substantially flat and adapted to abut the said upwardly facing end surface of said lower expander body and in the upper end of said packing sleeve a concentric cylindrical slit extending axially downward from the upper end thereof adjacent said upper expander body and having a diameter substantially equal to the inside diameter of said annular recess, said slit sleeve initially with the lower end of said packing sleeve in abutment with the upper end of said lower expander body and with the upper end of said outer annular lip of said packing sleeve in end to end abutment with the lower end portion of said upper expander body surrounding the entrance to said annular recess and with the upper end portion of said inner annular lip extending partially into the said annular recess; and anchoring means included in said positioning means located adjacent the said lower end of said packing sleeve and extending between said packing sleeve and a longitudinally elongated slot in said mandrel initially to prevent upward longitudinal sliding motion of said packing sleeve relative to said mandrel but permitting limited upward sliding motion of said mandrel relative to said packing sleeve.

9. In a bridging plug: a mandrel; upper and lower expander bodies on said mandrel and slidable longitudinally relative to one another, the lower expander body being formed with a substantially flat upwardly facing end surface and the upper expander body being formed with a counterbore extending upwardly from the lower end thereof said counterbore defining with said mandrel a coaxial annular recess; a packing sleeve encircling said mandrel intermediate said expander bodies and having the lower end thereof substantially flat and adapted to abut the said upwardly facing end surface of said lower expander body and in the upper end of said packing sleeve a concentric cylindrical slit extending axially downward from the upper end thereof adjacent said upper expander body and having a diameter substantially equal to the inside diameter of said annular recess, said slit dividing the upper end portion of said packing sleeve into inner and outer concentric, annular lips joined together at the lower termination of said slit; means positioning said expander bodies relative to said packing sleeve initially with the lower end of said packing sleeve in abutment with the upper end of said lower expander body and with the upper end of said outer annular lip of said packing sleeve in end to end abutment with the lower end portion of said upper expander body surrounding the entrance to said annular recess and with the upper end portion of said inner annular lip extending partially into the said annular recess; frangible means initially fixing said upper expander body to said mandrel and a projection extending inwardly from said packing sleeve into a groove in said mandrel said groove being located in said mandrel in position initially to prevent upward movement of said packing sleeve relative to said upper expander body while said upper expander body is fixed to said mandrel.

10. In a bridging plug apparatus according to claim 7 in which the upper and lower expander bodies comprise upwardly and downwardly converging slip expander cones respectively; upper and lower slips on said cones; and resilient means urging said lower slips upwardly on said lower slip cone.

11. In a bridging plug apparatus according to claim 7 in which the upper and lower expander bodies comprise upwardly and downwardly converging slip expander cones respectively; upper and lower slips on said cones; resilient means urging said lower slips upwardly on said lower slip cone; upper and lower slips on said slip cones;'a slip retainer ring positioned around the lower portion of said mandrel below said slips; radially slidable dove-tail connections between said slip retainer ring and the bottom ends of said lower slips; and resilient means acting between said retainer ring and said mandrel urging said retainer ring and said slips attached thereto by said dovetail connections, upwardly relative to said mandrel.

(References on following page) 1 1 References Cited in the file of this patent 2,249,155

, UNITED STATES PATENTS 530,631 Warner Dec. 11, 1894 Y 5 1,536,370 Becker May 5, 5 2 331 1 5 2,043,492 Reynolds June 9, 1936 12 Meddick July 15, 1941 Quintrell July 15, 1941 Burt July 14, 1942 Baker Apr. 6, 1943 Gordy Oct. 5, 1943

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