US3082824A

US3082824A - Well packing devices

Info

Publication number: US3082824A
Application number: US803063A
Authority: US
Inventors: Francis A Taylor
Original assignee: Lane Wells Co
Current assignee: Lane Wells Co
Priority date: 1959-03-20
Filing date: 1959-03-20
Publication date: 1963-03-26
Anticipated expiration: 1980-03-26

Description

F. A. TAYLOR ETAL 3,082,824

wELL PACKING DEVICES 2 sheds-sheet 2 FRANCIS A. TAYLOR om Wm Mmm DH. N/D A L F S. E 6 R O E G EVRM VV. M01/aw ATTORNEY March 26, 1963 Filed March 20, 1959 United States Patent @hure 3,082,824 WELL PACKlNG DEVICES Francis A. Taylor, Lane-Wells Co., R0. Box 1407,

Houston 1, Tex., and George S. Flanders, deceased,

late oi Houston, rEex.

Filed Mar. 20, 1959, Ser. No. 363,063 3 Claims. (Qi. 16e-434) (Filed under Rule 47th) and 35 U.S.C. 118) This invention relates to well packing devices and more particularly to bridging plugs and similar apparatus adapted to be set within well boreholes and casings.

Packing devices, particularly of the bridging plug type, are usually employed for the well-known purpose of closing or `sealing olf a lower portion of a well bore or to separate upper and lower sections thereof for various purposes. -In bridging plugs of the usual type employing a double-ended resilient packing sleeve body and a pair of sets of oppositely acting casing gripping devices, such as serrated slips, the holding action of .the plug is directly proportional to the amount of pressure exerted by a setting tool in axially compressing the resilient packing member and forcing it to expand radially `against the well bore casing. ln conventional packers, the slips or similar holding devices are forced into wedging engagement with the well casing incident to the same longitudinal compressive action that expands the packing elements radially and under such conditions both sets of slips may be in gripping engagement with the casing while the setting -tool is still acting to compress the packing element. 4As a result, a substantial portion of the setting force applied to the plug is used in dragging the slips along the casing against their very considerable holding force and therefore is not fully converted to an etfective packer expanding force. The limiting in this way of the compressive holding force actually applied to the packer elements in turn limits the holding power of the bridging plug and frequently results in `an imperfect setting with subsequent failure under high fluid pressure. Such bridging plug failures may be very troublesome and costly during well completion or workover operations.

It is, therefore, an object of this invention to provide a bridging plug of improved effectiveness in sealing off well casings Iand more elfective as a seal against very high pressures.

It is a further object of this invention to provide a bridging plug of such construction that more of the compressive -force applied thereto by the setting tool is effectively transferred to radially expand the packer elements and thus increase the sealing and holding power of the plug.

It is another object of this invention to provide a well bridging plug of the aforesaid nature which is of relatively simple and inexpensive construction yet capable of providing improved sealing, and being adapted for setting by the use of conventional tools and techniques.

These objects are attained in general by the provision of means `for holding at least one of the sets of slips against release into friotonal engagement with the casing until the maximum desired pressure has been directly applied therethrough axially of the bridging plug to expand the packing members. In the present invention such means takes the form of shear pins which interconnect the slips and slip cone. These pins are of relatively high predetermined `strength and such that they will not shear to release the slips until a predetermined axial compressive force has been applied through the slips and slip cone and is fully transmitted therefrom to the packing elements fully to expand them into sealing engagement with a surrounding casing wall. After this predetermined loading of the packing elements has been reached, the pins shear and the slips are thereby released and forced against 3,082,824 Patented Mar. 26, 1963 the side of the well casing thus holding the entire bridging plug against axial movement in either direction. During the time the compressive force is thus applied to the packing elements, -a safety ratchet ring engages a series of buttress threads on the mandrel of the plug in such manner as to restrain the packing against retrograde axial expansion and resultant loosening at the instant of shearing of the shear pins and the following movement of the slips into engagement with the casing.

In the `accompanying drawings:

FIG. l is a longitudinal sectional view of a preferred form of bridging plug embodying the present invention as the latter appears when assembled ready to be lowered into a well or when being lowered or suspended within a well casing just prior to setting;

FIG. 2 is a longitudinal sectional view of said bridging plug in reduced scale showing its appearance and positions of its parts after a setting operation has` been initiated;

FIG. 3 is a longitudinal sectional view of said plug showing its appearance and positions of its pants just after completion of the setting operation; `and FIG. 4 is a longitudinal sectional view of said plug showing its appearance and positions of its parts after the setting operation has been completed and its setting tool has -been withdrawn.

Referring to the drawings and particularly FIG. l thereof, a preferred form of bridging plug embodying the present invention includes a centrally located, elongated tubular Ibody or mandrel 10 of substantially uniform external diameter throughout its length and terminating at its lower end in a bull plug 11 of greater diameter. A packing body 12 of resilient material encircles the intermediate portion of the mandrel 10 with its lower end in abutment with a lower cone member 46 and its upper end in abutment with a back-up ring 68. The packing assembly 12 initially has substantial clearance with the walls of the conning enclosure, such as a well casing 20, to insure its unimpeded lowering through the well bore to the desired point at which it is to be set. This is the condition indicated in FIG. l. When the bridging plug reaches the portion of the well bore at which it is to be set the packing body is axially compressed by suitable means to be fully described hereinafter. This axial compression of the packing body 12 effects its radially outward expansion against the well casing 20, as indicated in FGS. 2, 3 and 4.

More particularly, and with continued reference to FIG. l, the lower portion of the mandrel 10 is formed with a countenbore 26 of slightly enlarged diameter with this counterbore having internal threads 2S. The bull plug 11 is fonmed with a boss .30 that has external threads 32 received by the threads 2S of counterbore 26. The upper portion of boss 30 is formed with an outwardly-@facing annular groove 33 wherein is disposed a resilient se'al ring, such as an 0 ring 34. The bull plug 11 includes an upwardly-facing annular shoulder 35 which abuts the lower end of the mandrel 10. The upper intermediate portion of the external cylindrical surface of the mandrel 1t) is formed with a length of downwardly-facing ratchet grooves or .buttress threads 36 for a purpose to be described hereinafter. The upper portion of the mandrel 10 is formed with a counterbore 38 of enlarged diameter that receives the lower end of a pull-out sleeve 40. The latter is normally aixed within the counterbore 38 by a plurality of upper shear screws 42. A plurality of lower wedge-shaped slips 44 having downwardly-facing serrations or wickers are normally positioned upon the upwardly facing annular shoulder -35 of the bull plug 11, with their upper portions being positioned upon an upwardly dii/erging, lower slip wedging 'means which in this embodiment takes the form of a cone 46- that longitudinally slidably encircles the lower portion of the lmandrel 10. The upper portion of the lower slips 44 are initially axed to the lower portion of the lower slip cone 46 by a plurality of lower shear screws 48. The lower slips 44 are adapted to undergo radial expansive movement towards the well casing 20 upon relative downward axial movement of the lower slip cone 46 following shearing of the screws 48.

The lower end of the packing body 12 abuts the upper end of the lower cone member 46. The packing body 12 .consists of three separate rings designated 60, 62 and 64, preferably formed of a molded rubber of the synthetic type, such as neoprene, which material is resistant to the solvent eifects of petroleum. A back-up ring 68 abuts the upper end of the top packing ring 60, the backup ring 68 being axially slidably carried by the upper end of the mandrel 10.

The upper end of 'the back-up ring 68 abuts the lower end of a wedging means which in this embodiment takes the form of an upwardly converging upper slip cone 74, the latter being axially slidably carried upon the pull-out sleeve 40. The upper slip cone 74 is initially fixed against axial movement relative to the pullout sleeve 40 by a shear pin 76. The lower portion of the upper slip cone 74 is formed with a counterbore 78. A split lock ring 80 is disposed within this counterbore 78. The inner diameter of the locking ring 80 is formed with upwardly-facing buttress shaped grooves or threads 82 adapted to ratchet over and make one-way locking engagement with the downwardly-facing buttress shaped grooves or threads 36 of the mandrel 10. A plurality of wedge-shaped upper slips 84 having upwardly-facing serrations or wickers are positioned upon the upper portion of the upper slip `cone 74 with their upper portions encircling the pull-out sleeve 40. The upper slips S4 are initially aiixed to the upper slip cone 74 by a plurality of top shear screws 86.

The upper surfaces of the upper slips 84 abut the lower end of a tubular ram adapter sleeve 88 forming a part of a conventional setting tool, the details of which are not encompassed within the present invention. The lower portion of the adapter sleeve 88 slidably telescopes over the upper end of the pull-out sleeve 40. The lower tubular strut portion or connector rod 90 of the aforementioned setting tool depends coaxially through the pullout sleeve 40 and into the bore of the mandrel 10. The lower end of this connector rod 90 is threadedly connected to the upper end of a rupture stud 92. The lower end of the rupture stud 92 is threadedly connected to the upper end of boss 30 of the bull plug 11. The rupture stud 92 is provided with a reduced-diameter necked portion 94. The ram adapter sleeve 88 and the connector rod 90 may essentially resemble 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 Forsyth et al. Patent No. 2,566,323, at 11 and 13 in Spangler Patent No. 2,326,404, or at 6 and -16 in Batchelder Patent No. 2,382,770.

In the operation of the aforedescribed bridging plug, the plug assembled as shown in FIG. l is lowered into the well bore upon a suitable setting tool as hereinbefore mentioned 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 connector rod 90 to the bull plug boss 30 and thence as a compressive force from the bull plug 11 upward through the bridging plug mandrel 10. This upward force is initially balanced by an equal downward compressive force applied from the setting tool through the adapter sleeve 88, slips 84, shear pins 86, slip cone 74 and shear pin 76. The upward force thus applied to the bridging plug mandrel tends to move the mandrel 10 and pull-out sleeve 40 upwardly with respect to and in opposition to the downward force from the adapter sleeve 88 to a position such as that indicated in FIG. 2. However, shear pin 76 initially resists such relative motion and opposing forces until the force reached a value equal to the shearing strength of the pin. In one embodiment of the invention, shear pin 76 is a 5/16 inch diameter stud of AISI 4130 steel with a shear strength of 4500 pounds. Upon shearing of the pin 76, the opposing forces thus initially applied upwardly through the mandrel 10 and downwardly through the adapter sleeve 88 are suddenly transferred into a longitudinal compressive force acting through the several bridging plug elements on the mandrel between the bull plug shoulder 35 and the lower slips 44 and the adapter sleeve 88 and the upper slips 84. This force causes the bottom shear 'screws 48 to be next sheared. Screws 48 are commercial fn inch diameter brass screws and fail immediately upon application of such downward force. This permits further movement of the adapter sleeve 88 and bull plug 11 toward one another so as to cause the lower slip cone 46 to Wedge the lower slips 44 radially outwardly into engagement with the walls of the well casing 20, as indicated in FIG. 2. The beforementioned compressive force acting through the several bridging plug elements will also cause the packing body 12 to be squeezed longitudinally and thereby expanded radially outwardly against the walls of the well casing 20, as indicated in FIG. 2.

Since the upper slips 84 are at this stage of the setting operation still held in retracted position by shear screws 86, none of the `downward force of adapter sleeve 88 is dissipated in dragging them along the inner walls of casing 20. Thus, all of the applied force is applied to packing body 12 and used to radially expand it into a tight t.

Referring now to FIG. 3, continued downward movement of the adapter sleeve 88 relative to upward movement of the bull plug 11 will nally cause the top shear screws 86 to rupture. In the embodiment described, which has a diameter of 5.7 inches with its packing body uncompressed and adapted for use within a 7 inch outside diameter casing, there are six top shear screws each made of AISI 4140 steel and 1/4 inch in diameter by 2% inch long. Each has a shearing strength of about 3400 pounds so that a total compression of over 20,000 pounds can be applied to expand packing body 12 before shearing takes place. The upper slips 84 will then move downwardly relative to the slip cone 74 under continued downward movement of adapter sleeve 88 so as to be wedged thereby radially outwardly against the walls of the well casing 20. Both the upper and

lower slips

84 and 44, respectively, will now be in tight gripping engagement with the inside surface of the well casing 20. Additionally, the packing body 12 has been expanded into fluidtight sealing engagement with the inside surface of the well casing. During the relative movement of the various parts carried by the mandrel 10, the lock ring will have ratcheted downwardly over the grooves 36. When shear screws 86 rupture, there will be a tendency for packing body 12 to expand axially. However, a very slight axial expansion carries back-up ring 68 against lock ring 80 as shown in FIGS. 3 and 4. Lock ring 80 is held against upward movement by buttress thread 36 and is thus effective to hold packing body 12 under substantially full axial compression and lateral expansion.

The mandrel 10, and the parts encircling the mandrel are now positively xed against longitudinal movement relative to the well casing 20. Accordingly, upon continued application of tensile force through the connector rod balanced by downward force through adapter sleeve 88, the necked portion 94 of the rupture `stud 92 will nally fail in tension. The connector rod will then be free to move upwardly. Such upward movement of the connector rod 90 will be directly transferred to the upper wall of the pull-out sleeve 40 by Imeans of an enlarged-diameter threaded portion 122 of the rod. This threaded portion 122 of the connector rod 90 was originally screwed downwardly through complementary internal threads 124 formed on the pull-out sleeves top wall 120, when the parts of the bridging plug were assembled as shown in FIG. 1. When the upwardly moving connector rod 90 thus exerts sufficient upward force on top wall 120 of the pull-out sleeve 40, the shear screws di?, will fall and the pull-out sleeve 4d will be free to be withdrawn upwardly from the remainder of the bridging plug, the entire aforementioned setting tool being withdrawn upwardly through the well bore, leaving the bridging plug element set as shown in FIG. 4.

With the bridging plug set as shown in FlG. 4, the upper slips S4 securely anchor it in place against upwardlydirected forces produced by fluid pressures below the plug. The lower slips 44 similarly anchor ne plug in place against the downwardly-directed forces produced by iiuid pressures acting downwardly upon the plug. The expanded packing body 12 will serve to form a Huid-tight seal within the annulus between the mandrel body and the inside surface of the well casing 20. The bull plug 11 blocks liuid flow through the mandrel 10. The material of the packing body is under the maximum applied compressive force since all of the downward movement through slips 84- and cone 70 has been effectively retained. Accordingly, the bridging plug will fullill its well sealing function until such time as the plug is to be removed from the well bore. In a bridging plug of the type herein disclosed, substantially all of its principal part-s are preferably constructed of materials which are relatively easily rilla'ole by ordinary well drilling tools. This permits removal of the bridging plug if necessary after the plug has been set.

It is to be understood that the foregoing is illustrative only and tthat the invention is not limited thereby, but may include various modilications and changes made by those skilled in the art without departing rom the spirit of the invention or the scope of the following claims.

What is clairned is:

1. In a bridging plug having in combination a'mandrel, first and second slips arranged adjacent opposite ends of said mandrel respectively, a resilient packing body circumferentially mounted on said mandrel intermediately of said slips, and irst and second slip expanders slidably mounted on said mandrel intermediately of said packing body and said first and second slips respectively and each further adapted and arranged to wedge its respective slip outwardly of said mandrel when such respective slip is urged toward said packing body, :the improvement in combination therewith comprising a tir-st shear pin arranged to secure said lirst slip to said rst expander, a second shear pin arranged to secure said second slip to said second expander and having a shear strength greater than that of said first shear pin, and latching means arranged between said mandrel and said second expander and adapted to oppose movement of said second expander slidably along said mandrel and away from said packing body.

2. in a bridging plug having in combination a mandrel, lirst and second slips arranged adjacent opposite ends of said mandrel respectively, a resilient packing body circumferentially mounted on said mandrel intermediately of said slips, and rst and second slip expanders slidably mounted on said mandrel intermediately of said packing body and said first and second slips respectively and each further adapted and arranged to wedge its respective slip outwardly of said mandrel when such respective slip is urged toward said packing body, the improvement in com* bination therewith comprising a first retaining means arranged and adapted to tix said first slip to said lirst expander and further adapted to release Said lirst slip when subjected to a force of a lirst magnitude, a second retaining means arranged and adapted to fix said second slip to said second expander and further adapted to release said second slip when subjected to a force of a second greater magnitude, and stopping means arranged and adapted to oppose slidable movement of said second expander along said mandrel and away from said packing body.

3. In a bridging plug having in combination a mandrel, lirst and .second slips arranged adjacent opposite ends of said mandrel respectively, a resilient packing body circumferentially mounted on said mandrel intermediately of said slips, and -iirst and second slip expanders sli-dably mounted on said mandrel intermediately of said packing body and said iirst and second `slips respectively and each further adapted and arranged to wedge its respective slip outwardly of said mandrel when such respective slip is urged toward said packing body, the improvement in combination therewith comprising a irst retaining means tixedly engaging said tirst slip and expander and adapted to disengage said irst slip and expander when subjected to a force of a first magnitude, a second retaining means lixedly engaging said second slip and expander and adapted to disengage said second slip and expander when subjected to a force of a second greater magnitude, and holding means arranged and adapted to subject said packing body to said force of said second magnitude when `said second retaining means disengages said second slip and expander.

References Cited in the tile of this patent UNITED STATES PATENTS 2,121,050 Ragan et al June 2l, 1938 2,665,763 Baker Ian. 12, 1954 2,695,064 Ragan etal Nov. 23, 1954 2,713,910 Baker et al July 26, 1955 3,002,561 Baker et al Oct. 3, 1961

Claims

1. IN A BRIDGING PLUG HAVING IN COMBINATION A MANDREL, FIRST AND SECOND SLIPS ARRANGED ADJACENT OPPOSITE ENDS OF SAID MANDREL RESPECTIVELY, A RESILIENT PACKING BODY CIRCUMFERENTIALLY MOUNTED ON SAID MANDREL INTERMEDIATELY OF SAID SLIPS, AND FIRST AND SECOND SLIP EXPANDERS SLIDABLY MOUNTED ON SAID MANDREL INTERMEDIATELY OF SAID PACKING BODY AND SAID FIRST AND SECOND SLIPS RESPECTIVELY AND EACH FURTHER ADAPTED AND ARRANGED TO WEDGE ITS RESPECTIVE SLIP OUTWARDLY OF SAID MANDREL WHEN SUCH RESPECTIVE SLIP IS URGED TOWARD SAID PACKING BODY, THE IMPROVEMENT IN COMBINATION THEREWITH COMPRISING A FIRST SHEAR PIN ARRANGED TO SECURE SAID FIRST SLIP TO SAID FIRST EXPANDER, A SECOND SHEAR PIN ARRANGED TO SECURE SAID SECOND SLIP TO SAID SECOND EXPANDER AND HAVING A SHEAR STRENGTH GREATER THAN THAT OF SAID FIRST SHEAR PIN, AND LATCHING MEANS ARRANGED BETWEEN SAID MANDREL AND SAID SECOND EXPANDER AND ADAPTED TO OPPOSE MOVEMENT OF SAID SECOND EXPANDER SLIDABLY ALONG SAID MANDREL AND AWAY FROM SAID PACKING BODY.