US3851707A

US3851707A - Uni-directional unitary anchor slip

Info

Publication number: US3851707A
Application number: US00412239A
Authority: US
Inventors: M Jett
Original assignee: Dresser Industries Inc
Current assignee: Dresser Industries Inc
Priority date: 1973-11-02
Filing date: 1973-11-02
Publication date: 1974-12-03
Anticipated expiration: 1991-12-03
Also published as: GB1483071A; CA1002448A; DE2452434A1; DE2452434C3; DE2452434B2

Abstract

An improved unitary anchor slip utilizes a partially flat, partially curved abutment surface for allowing pivoting, setting, and later dislodgement of the slip in the casing, said abutment surface eliminating the need for pivot pins, supporting sleeves and pivot clearances with the improved unitary anchor slip.

Description

United States Patent 1191 Jett [ Dec.3,1974

[ 1 UNI-DIRECTIONAL UNITARY ANCHOR SLIP [75] Inventor:

[73] Assignee: Dresser Industries, Inc., Dallas, Tex.

[22] Filed: Nov. 2, 1973 [21] Appl. No.: 412,239

Marion Barney Jett, Seagoville, Tex.

[52] US. Cl. 166/212, 166/134 [51] Int. Cl E211) 23/00 [58] Field of Search 166/206, 212, 216, 217,

[56] References Cited UNITED STATES PATENTS 5/1953 Soberg et al 166/136 12/1968 Prescott 1 166/206 X 12/1970 Kilgore 166/217 X 3,687,196 8/1972 Mullins 166/217 3,714,984 2/1973 Read 1. 166/206 X 3,731,740 5/1973 Douglas. 166/120 3,735,814 5/1973 Tucker 166/217 3,739,849 6/1973 Meripol 166/216 3,779,314 12/1973 Read 166/216 3,804,164 4/1974 Ellis 166/120 Primary ExaminerDavid H. Brown Attorney, Agent, or FirmMichael .1. Caddell 5 7] ABSTRACT An improved unitary anchor slip utilizes a partially flat, partially curved abutment surface for allowing pivoting, setting, and later dislodgement of the slip in the casing, said abutment surface eliminating the need for pivot pins, supporting sleeves and pivot clearances with the improved unitary anchor slip.

7 Claims, 36 Drawing Figures PATENTELBEB 31914 sum n: if 13 PAIENTELUEB 31914 saw on E13 PATENTELBEB 31w 3,851,707

sum as ar 13 PATENTEL sac 3mm sum as 0F 13 mQ w; n

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sum 10 at FIG? 5 FIG. I5BI PATENTELBEB 3W 3.851.701" sum '11- 13 v FIG. I68

PATENTEL 115C sum 13or13 FIG. 20a

FIG. 2|

UNI-DIRECTIONAL UNITARY ANCHOR SLIP BACKGROUND OF THE INVENTION Often during the producing life of an oil well it becomes desirable or necessary to produce from two or more different underground formations penetrated by the wellbore. This is commonly achieved through the use of packer assemblies containing two or more strings of conduit passing therethrough.

An example of such apparatus is shown in U.S. Pat. No. 2,965,173 in which a packer apparatus having dual conduit strings passing side-by-side therethrough has located on its outer surface resilient sealing cups having outwardly flared ends which are moved into sealing engagement by fluid pressure differentials above and below the cups.

Other types of multi-string packers include the inflatable or bladder type such as disclosed in U.S. Pat. No. 2,991,833 and the hydraulically actuated, compressible element, multi-string packer such as disclosed in U.S. Pat. No. 3,167,127. All known multi-string packers using mechanical anchors to lock the assembly to the casing wall utilize the wedge-type slip segments having teeth which are cammed or wedged into contact with the casing wall by the action of a wedging mandrel being forced inside the slip segments forcing them outwardly into contact with the casing. Other known types of slips include the hydraulic button type which are spring-retained radial pistons slidably located in the wall of the packer body and actuated outwardly against the spring retainer by hydraulic force applied from inside the packer assembly. An example of the button type slips is shown in U.S. Pat. No. 3,3l 1,169.

The dual-string or dual-conduit packers normally are used with a standard single string packer located on the tubing string below the dual-packer, which tubing string communicates with a lower formation below the standard packer and is connected to one conduit in the dual packer and from there to a tubing string passing to the surface. The second formation is normally located between the standard packer and the dual packer and can be produced through the second conduit passing through the dual packer and communicating with v a second tubing string extending to the surface.

The disadvantages of the prior art dual string packers are their complexity, extended length, and the ten- 4 dency of the wedge-type slips to become disengaged by shifting or stretching of the tubing and/or casing during the production life of the packer.

These and other disadvantages of prior devices are overcome by the present invention which comprises a dual string packer having simplified design shortened length, and highly efficient tubular unitary slip means.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is'a top view of the dual packer assembly; FIGS. 2A and 23 comprise a lateral cross-sectional view of the assembly taken at line 2-2 of FIG. 1;

FIG. 5, shows an axial cross-sectional view of the assembly taken at line 5-5 of FIG. 2;

FIG. 6 is a cross-section side view of the improved unitary tubular slip;

FIG. 7 is a top view of the improved unitary slip;

FIG. 7a is a side view of the improved unitary slip;

FIG. 8 illustrates a cross-sectional view of the apparatus in its engaged position;

FIG. 9 illustrates the top view of an alternate embodiment of the apparatus;

FIGS. 10A through 10C comprise a cross-sectional view of the embodiment of FIG. 9 taken at line 10-10 in FIG. 8;

FIGS. through 110 are cross-sectional views of the embodiment of FIG. 9 taken at line 11-11;

FIG. 11d is a cross-sectional axial view of a key retaining sleeve;

FIG. 1 leis a side cross-sectional view of a key retaining sleeve;

FIG. 11f is an axial end view of a retaining key;

FIGS. 12A through 12C comprise a cross-sectional view of the embodiment of FIG. 9 taken at line 12-12 of FIG. 9;

FIG. 13 is an isometric view of the shearable ratchet pins;

FIG. 14 is an isometric view of one of the setting cylinder releasing keys in the piston assembly;

FIGS. 15a and 15b are schematic cross-sectional views of the gripping teeth on the anchor slip;

FIGS. 16a and 16b show axial and radial crosssectional views of the wedge-cone heads disassembled from the apparatus;

FIG. 17 illustrates a cross-sectional view of the slip of the second embodiment;

FIG. 18 shows a side view of the slip of FIG. 17;

FIG. 19 is an axial cross-sectional view of a mandrel locking assembly;

FIG. 20 is a lateral cross-sectional side view of the mechanism of FIG. 19 taken at line 20-20;

FIG. 21 is a lateral cross-sectional top view of the mechanism of FIG. 19 taken at line 21-21.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the invention is illustrated in FIGS. 1 through 5 in which a packer assembly 1 is comprised of an upper mandrel assembly head 2, resilient packer assembly 3, upper slip 4, lower slip 5, and piston assembly 6, all mounted more or less in encircling relationship about primary mandrel 7 and secondary mandrel 8.

The upper mandrel assembly head consists of an integral cylindrical mandrel head 9 having longitudinal

parallel bore passages

10 and 11 passing therethrough having internal threaded section's 10a and 11a in which are threadedly engaged the cylindrical tubular

elongated mandrels

7 and 8. A receiver collar 12 is connected by bolts 13 to mandrel head 9 and has bore passages 10b and 11b coinciding and axially aligned with

passages

10 and 11 of head 9. Collar 12 has a concave cupped upper surface 12a arranged to guide a tubing string connector 14 into bore 11b of the assembly. Mandrel head 9 further has a threaded internal section 10c adapted to receive a section of conduit or tubing in threaded engagement therein.

Tubular mandrels

7 and 8, fixedly attached by threaded connection to head 9, extend in parallel relationship to the longitudinal axis of the packer assembly 1 and generally parallel to the well-bore and have bottom threaded sections 7a and 8a extending downward out of the piston assembly 6 whereby either or both may be threadedly engaged into a lower tubing string extending downward into the wellbore.

Slidably mounted on

mandrels

7 and 8 are, in descending order, the upper unitary slip 4, upper packer head 31, one or more resilient packer elements 32, and lower packer head 33. Upper and lower packer heads 31 and 33 are metal cylindrical plates having a cupped surface on one side and having two axial bores therethrough for receiving

mandrels

7 and 8.

Resilient packer elements 32 are made of a resilient material such as synthetic rubber and are generally cylindrical, with dual bore passages passing axially therethrough to snugly receive

mandrels

7 and 8. Packer elements 32 are located in close fitting relationship with each other and with the cupped surfaces of

plates

31 and 33. A flanged retainer ring 34 abutting an external shoulder 18 on mandrel 8 limits downward movement of the resilient packer assembly 3 on the mandrels by also abutting the lower surface of lower head 33.

Lower unitary slip 5 is located on the mandrels in encircling relationship about the mandrels and slidably mounted thereon; slip 5 is similar to slip 4 but is mounted on the mandrels in an inverted orientation to slip 4.

Piston assembly 6 is mounted on

mandrels

7 and 8 in encircling relationship and consists of cylindrical setting piston 61 and cylindrical setting cylinder 62. Setting piston 61 is a substantially solid cylindrical piece having dual axial bore passages therethrough to receive

mandrels

7 and 8 and an upper annular space 63 around mandrel 8. Referring to FIG. 5, setting piston 61, as shown in cross-section, has a plurality of transverse lateral cylindrical bore passages 64 intersecting the longitudinal axis of bore passage 11 and having internal helical threads. Shearable cylindrical ratchet pins 65 are slidably located in passages 64 and are urged into engagement with mandrel 8 by the expansive forces of leaf, helical, or belleville springs 66 which are held in compression against pins 65 by abutting engagement with threaded plugs 67 which are snugly secured into threaded passages 64. v

Pins 65 have a reduced section 65a designed to shear at a predetermined load and a toothed ratchet head 65b having a curved face adapted to match the curvature of mandrel 8, with a plurality of cammed teeth c thereon designed to match and engage external annular teeth 8b formed on mandrel 8. FIG. 13 illustrates a second view of the shearable ratchet pins showing the relationship of the teeth 650 on ratchet head 65b. The teeth 8b and those on head 65b are arranged to allow upward movement of the pins on mandrel 8 but prevent downward movement of the pins and thus prevent downward movement of piston 61. The cammed faces of

teeth

8b and 65c allow the piston 61 to move upward by camming the pins back against the springs 66, compressing them and allowing the ratchet teeth to slide over one another. Upon attempted downward movement of piston 61 on mandrel 8 the perpendicular faces of teeth 65c abut the perpendicular faces of teeth 8b and prevent the backward motion. Further operation and function of the ratcheting arrangement will be described in connection with operation of the entire packing assem-. y-

Setting cylinder 62 is a cylindrical element having a substantially solid lower section 62a and an upwardly extending outer collar 62b passing exteriorly around piston 61. Lower section 62a is solid except for two longitudinal bore passages therethrough which receive in snug slidable relationship the

mandrels

7 and 8. Cylinder 62 is temporarily attached to piston 61 by means of a plurality of shear pins 68 passing through upper collar 62b in threaded engagement therewith and seating in exterior channel 61a passing circumferentially around piston 61.

Setting cylinder 62 is temporarily attached to mandrel 8 by means of a plurality of curved locking keys 69 having inwardly projecting shoulder 69a thereon for engaging a matching exterior channel in mandrel 8. Keys 69 are held inward by overlapping abutment of annular shoulder 61b on the lower end of piston 61. The keys, by abutment with the grooved channel in mandrel 8, the lower end of piston 61, and the upper end of solid end 620 of cylinder 62 temporarily prevent any sliding motion of the piston assembly 6 with respect to

mandrels

7 and 8. One or more ports are located through the wall of mandrel 8 to communicate with the area between piston 61 and cylinder end 62a from bore 11 to release keys 69 in a manner which will be more fully described in relation to the operation of this tool.

At the lower end of mandrel Son external threaded end 8a is a standard threaded collar 19 attachedand alow fluid pressure to be applied through ports 80.

Referring specifically to FIGS. 2 and 4, the tubing string connector 14 is more particularly described as a cylindrical tubular upper sleeve having internal threads 14a for engaging a standard conduit section and an annular external depression 14b for receiving a seal carrier ring 15. A lower spring collet sleeve 16 is threadedly attached at 16a to the upper sleeve 14c and has collar 16b thereon for abutting and retaining carrier ring 15 which has a plurality of circular seals 17 thereon for sealing engagement between connector 14 and head 9.

Collet sleeve 16 is temporarily restrained in head 9 by the abutment of annular exterior shoulder 16c with interior annular projection 9a in head 9. Removal of shoulder 16c upward past projection 9a can be accomplished by application of a predetermined lifting force which causes inward deflection of the shoulder 16c and allows it to move upward past projection 9a. Deflection inward of shoulder 16c is made possible by the forming of several longitudinal slots 16d in collet sleeve 16 thereby lending flexibility to the metal remaining in the areas between the slots. The amount of lifting force required to move collet sleeve 16 out of head 9 can be adjusted as desired by the number and/or width of slots 16d and/or the angle of engagement between and 9a.

Referring now to FIGS. 6, 7, 7a, 15a, and 151;, a more detailed description of the improved unitary slip members can be given. Each

slip

4 and 5 comprises a generally cylindrical gripping unit having on the extended outer reaches of opposing sides a plurality of teeth 41 curved about the slip body with an axis of curvature at an angle to the central longitudinal axis of the slip member. The teeth are also arranged so that the intersection of a plane passing through the slip longitudinal axis with the teeth extreme outer'tips would circumscribe a curve as shown in FIGS. a and 15b. This is to allow the use of this apparatus in casings having varying inner diameters and obviates the need for a separate set of unitary slips for each weight rating of casing. In smaller ID casings, as shown in FIG. 15a, i.e., those of heavier weight, the two sets of teeth near the center of the slip, having the shortest distance between them will contact the casing wall with greatest area contact; while in larger ID, lighter weight casing as shown in FIG. 1512, the teeth at the two outer ends of the slip will contact the casing due to the greater distance between the upper outer teeth and the lower outer teeth.

The curved boundary tooth profile as shown in FIGS. 15a and 15b allows this versatility of use by providing greater tooth-casing wall contact area regardless of which teeth are called upon to anchor the packer assembly.

Looking at FIGS. 6, 7 and 7a, it is clear that each unitary slip has a dual-axis bore passage for each mandrel to pass therethrough. One axis of each bore passage generally parallels the central longitudinal axis of the slip and the other axis is located at an angle thereto in the same plane.

In FIG. 6, the intersecting bore passages are illustrated more clearly and their longitudinal axes are designated as XX and Y -Y. This view is taken from the side with the two mandrels lying in line with one another so that only one can be seen in cross section. The axis XX defines bore passages 43 which are shown by the dashed lines in the figure. When the slip is oriented so that the mandrels occupy these bore passages, the

' grippingteeth are at their innermost orientation, out of contact with the casing wall.

When the slip has been rotated to bring the passages 44 into fitting relationship with the mandrels, then the gripping teeth are at their outermost extension from the mandrels and can engage the casing wall. Bore passages 44 are shown by the solid lines in the figure.

The angle between axes XX and Y-Y can be from 5 up to about 35 but preferably is around 18 to Referring specifically to FIG. 6, a significant improvement in the unitary anchor slip 5 is illustrated in the cross-sectional view which shows the abutment surface 51. This surface is at the opposite end of the slip from abutment edge 52 and provides a dual purpose surface on the slip.

Rotation of the slip into casing engagement is achieved by moving an abutment means such as piston 61 against compound surface 51 which moves the slip along the mandrel until abutment edge 52 encounters an opposing abutment surface. The resultant effect is a rotational moment established in the slip from the reactant force on edge 52. This is aided by abutment forces introduced into the slip from surface 51.

Surface 51 has been termed a dual or compound surface. This is because of the flat portion 51a and the tangentially curved section 51b joining the flat surface. The curve of surface 51b is preferably on a radius R substantially equivalent to lL where L is the axial length of the slip along axis XX. The curved surface is tangential to flat surface 51a at the point where axis XX intersects the end of the slip at surface 51.

The slip is arranged to pivot about a point C located at the intersection of axes XX and Y Y at a distance of approximately V2 of the slip length L from surface 51.

A phantom line P is drawn on the slip at the edge containing surface 51b to indicate the construction of the prior art slip means. Such a slip is disclosed in US. Pat. No. 3,739,849 to Robert B. Meripol. While the slip of that disclosure is a significant improvement over the art, the existence of the extended shoulder P requires significant additional apparatus in the packer on which it is used.

Primarily a significant clearance must be maintained with the prior art slip between the slip in its unset position and the lower abutment means to allow pivoting of the slip into casing engagement position. This is because the radius Rp is considerably greater than the dis tance /2L and therefore a minimum clearance equivalent to Rp-R must be maintained below the flat surface of the prior art slip to allow it to rotate into the set position.

To maintain the clearance and also to support the slip in a rotatable position and allow a moment force to be applied to abutment surface 52 without driving the slip downward on the abutment surface, the prior art slip was necessarily supported by pivot pins at C which passed through the slip and were engaged in an inner support sleeve. The downward force at 52 was countered by the oppositely reacting upward force of the pins on the slip which set up the desired rotational moment. The inner sleeve and the pins also served to hold the slip up off of the lower abutment means so that it could be pivoted. The inner sleeve and pivot support pins are illustrated in FIG. 1 of the aforementioned Meripol patent and designated therein as 20 and 34 respectively. The clearance under the slip is not illustrated in that figure since the slip has been rotated to the engaging position.

The improved slip of this invention eliminates the need for the supporting sleeve, the pivot pins, and the pivot clearance necessary to the prior art device.

Since the radius of the curvature of surface 5 lb about the pivot center C is equivalent to the distance of surface 51a from C, it is obvious that the slip 5 can be pivoted about C in the same space as that occupied by the slip in the unset position. This eliminates the need for the support sleeve, the pins, and the clearance below surface 51. Furthermore surface 51 may remain in constant abutment with adjacent abutment means to provide the necessary rotational moment from forces on surface 52 which further obviates the need for support pins at C.

Another advantage of the improved slip is in the guaranteed setting of the slip. In the aforementioned patented slip, should the clearance below the slip ever be decreased due to stretching of the parts, accumulated debris in the clearance area, failure of one or more of the parts, or incorrect assembly of the tool during manufacture, to the point where the clearance is substantially less than the amount Rp- /L, it is clear that edge P will abut the lower surface or the debris in opposition to the setting forces at edge 52 and the desired rotational'moment about C will be cancelled.

This situation is non-existent since the slip can rotate without the needed clearance and due to the simplicity of having no pins, nor sleeves; and incorrect assembly and part failure are almost absolutely eliminated.

One further advantage of the improved slip is that, when used as the lower slip, should it become lodged in the casing to the point that the releasing spring 4% hereinafter described is insufficient to rotate it out of engagement, dislodgement can be accomplished by merely bumping upward on the slip with the lower abutment means. Since some point on the curved surface Slb will be located directly below C and will receive the upward abutment it is clear that no rotational v moment will be introduced into the slip, and the simple upward driving force, in addition to the disengaging force of the releasing spring 4% will dislodge the slip from the casing. The upper surface 52 will of course be free from abutment during this releasing step.

Although the slip 5 has been described above, it is emphasized that slip 4 is identical to slip 5 and operates in the same manner, and the above description appertains thereto as well. Thus it can be seen that these two side-by-side dual bore passages and the compound curved-flat abutment surface 511 allow the unitary slip to pivot about the two

parallel mandrels

7 and 8 from a non-engaging position to a casing contact position without any interference between the slips and the mandrels.

Each slip also has a releasing slot 46 as shown in FIG. 3 which runs partially the length of the slip and passes through the wall thereof in a plane perpendicular to the plane of the two dual-axis bore passages and the central slip axis. A third bore passage 47 passes from the inner terminal wall 46a of the slot 46 through the slip to the opposite end. The cross-sectional view of FIG. 3 reveals the purpose of slot 46 and passage 47 to be for the location of the threaded L-shaped releasing lug 48 and release spring 48a in the upper slip 4; and in the lower slip 5, retaining bolt 49, flanged bolt collar 49a, and coil spring 49b. A spring cavity 49c is formed in each slip and a spring cavity 48b is formed in the L-shaped bolt to receive coil spring 48a. Lug 48 passes through passage 47 and is threadedly secured into the lower end of head 9. Likewise, bolt 49 passes through passage 47 of the lower slip 5 and is threadedly secured to the upper end of setting piston 61.

In FIGS. 2 through 5 the packer assembly is illustrated in its unset'orientation with the

mandrels

7 and 8 lying in bore passages 43 parallel to the central longitudinal axis. In FIG. 8 the packer apparatus has been activated and expanded into sealing and anchoring engagement with the casing wall. In this position, the slips have been rotated to bring the mandrels into the second bore passages 44 at the angle to the longitudinal bore passages 43 mentioned above.

OPERATION OF THE PREFERRED EMBODIMENT In a typical use of the described apparatus in a dual zone formation the apparatus is interconnected into a tubing production string by threaded connection of threads'lllc and 7a to mating threads of standard tubing sections. The string will have a standard packer located in the string below this apparatus capable of sealing off the annulus between the tubing and the casing at the predetermined desired time.

The tubing string with the standard packer and the packer apparatus 1 is lowered into the well until the lower packer passes the upper producing formation and is situated between the two subject formations. The packer apparatus 1 will be located above the upper producing formation.

By appropriate means, such as manipulation of the tubing or hydraulic pressure applications, the lower packer is set in the casing. Alternately, the lower packer may be set by wireline or other means before the primary and secondary tubing strings are lowered into the hole and then the primary string can be stung into the lower packer. The second production string may then be lowered down the well with the connector sleeve 14 threadedly attached at the lower end. When the string has been lowered sufficiently, the sleeve 14 will engage head 9 and snap into place. The second string will then be sealingly communicating with mandrel 8 via bore 11 of head 9.

A sealing ball or'plug 20 is dropped run in on a wireline, or pumped into the secondary tubing string to seal on seat 21 and allow fluid pressure to be applied to the fluid in the secondary string and act through bore 11 and ports against the lower end of the setting piston 61. When sufficient pressure has been reached in bore 11, piston 61 will shear pins 68 and move upward against the lower edge 51 of lower slip 5 sliding the slip upward until upper abutment edge 52 of the slip contacts the lower edge of lower head 33. Movement upward of piston 61 on mandrel 8 is allowed by the ratcheting action of ratchet pins 65 over mandrel teeth 8b which ratchet mechanism simultaneously prevents downward movement of piston 61 on mandrel 8 under normal operating conditions.

As piston 61 moves upward in response to hydraulic pressure acting upward, the upward force is transferred to lower slip 5, and from slip 5 to packer elements 3 and into the upper slip 4. This abutment of the slips with the packer assembly serves to rotate the slips into contact with the casing simultaneously with compression of the packer elements 32. Thus, continued application of hydraulic pressure of sufficient magnitude for a short period of time will set the two unitary slips into the casing and will expand the resilient packer elements outward into sealing engagement with the casing as shown in FIG. 8.

Upon release of hydraulic pressure in bore 1 l, the resilient packer elements will attempt to expand longitudinally and contract radially. This will provide a constant upward force on slip 4 and a constant downward force on slip 5 maintaining them engaged in the casing. Also, ratchet pins 65 will maintain mandrel 8 telescoped within piston 61 thereby preventing the packer from unsetting should mandrel 8 try to move upward in the wellbore for any reason.

Should it become desirable to unseat the packer apparatus 1, this can be done selectively by applying an upward force on mandrel 7 and thus on mandrel 8 sufficient to shear pins 65 through their reduced area 65a. In order to prevent a bending or collapsing of shear head 65b along the gap at 65a, a relatively soft filler material such as lead or plastic can be filled in the gap at 65a to absorb the bending moment and insure proper shearing of the pins.

Upon shearing pins 65

mandrels

7 and 8 move upward with respect to the

slips

4 and 5 and packer assembly 3. Releasing lug 48 will move upward and work through spring 48a to pivot upper slip 4 back to its nonengaging position, also pulling it upward off of the packer assembly 3, allowing the resilient packer elements to contract to their normal unseated orientation.

Continued upper movement of the

mandrels

7 and 8 will disengage the lower head 33 from abutment shoulder 52 of slip allowing disengagement of the lower slip from the casing. Coil spring 4% will then expand against slip 5, thereby pivoting slip 5 into its retracted position. The packer assembly 1 is now completely unset and may be removed from the hole. The secondary tubing string may be removed from passage 11 before or after unsetting the packer assembly 1, or may be removed from the hole with the primary string if desirable.

MANDREL LOCKING MEANS FOR HIGH WELL PRESSURES Occasionally the apparatus of this invention must be used in a well having extremely high formation pressures or used in treatments of wells whereby fluids under high pressure must be pumped into the well formations through this apparatus.

For instance, pressures below the above described packer assembly may reach the range of 5,000 PSI or higher, and in this range a considerable upward force is exerted by the fluid upon the conduit strings in the wellbore, creating a buoyancy effect on the packer mandrels tending to drive them upward through the packer assembly resulting in unsetting of the slips and consequently the packer elements. This buoyancy effect is termed the piston? or end area effect.

To avoid this tendency towards disengagement of the slips caused by the pipe buoyancy, a special locking mechanism is'provided which is actuated by pressure below the packer elements and serves to lock the mandrels in the packer assembly.

Referring to FIGS. 19, 20, and 21 the locking mechanism is illustrated. FIG. 19 is an axial view in crosssection taken at line 19-19 of FIG. 20. In the modified embodiment, the packer assembly 3 of FIGS. 1-4 is replaced by the modified locking packer assembly 203.

Packer assembly 203 consists essentially of an upper head 231, resilient packer elements 232 and lower head 233, all encircling mandrel 7 and modified mandrel 208.

Modified mandrel 208 is substantially similar to mandrel 8 except for the existence of a plurality of tooth ridges 210 formed in the outer surface of the mandrel. Each ridge 210 has an abrupt upper face 210a and a sloping lower face 21%. The angle that face 210a makes with a plane normal to the tubular axis of mandrel 208 is preferably about ten degrees but may vary from 1 to 40 depending upon the amount of restraining force desired. The angle of face 2l0b with face 210a may be from 130 to about with a preferable angle of around 90 degrees. Ridges 210 preferably circle mandrel 208 entirely but this is not absolutely essentiaL.

I The packer assembly 203 contains two fluid bore

passages

204 and 205 passing through lower head 233, resilient packer elements 232, and part of the way into upper head 231. The bore passages generally run parallel to the mandrels '7 and 208 and communicate with the formation annular area below the packer assembly 203.

Rigid tubes

206 and 207 line the bores through the resilient elements 232 to prevent collapse and closure of the passages upon compression and deformation of the resilient packer elements.

The bore passages 204 and 20S intersect

pin channels

211 and 212 passing from the longitudinal bore passage 209 in head 231 containing mandrel 208, going radially outward from mandrel 208 through head 231 and through the outer surface of the head.

The

radial passages

211 and 212 contain outer threaded

portions

211a and 212a-and smooth piston sections 21 1b and 212b. The radial passages preferably are of a cylindrical configuration for ease and convenience of manufacture but may be of any reasonable configuration.

Located slidably in piston sections 211k and 21212 of the radial passages are locking

pistons

213 and 214 having curved toothed faces 213a and 214a. The teeth on these faces match and complement the teeth of mandrel 208 so that full surface contact between the two sets of teeth will occur. The radius of curvature of

faces

213a and 214a is substantially equal to that of the outer surface of mandrel 208.

Threaded

sections

211a and 212a contain threaded

plugs

215 and 216 snugly engaged therein in sealing contact, which plugs, in conjunction with

pistons

213 and 214, serve to form

hydraulic expansion chambers

217 and 218 in each radial passage. Circular seals 219 and 220 in the outer wall of

pistons

213 and 214 serve to prevent leakage of fluid from the expansion chambers into the mandrel bore passages 209.

Operation of the locking mechanism is automatic when this modified embodiment of packer mechanism 203 is installed in the previously described packer apparatus 1, and consists of hydraulic pressure from the annular area below the packer mechanism 203 communicating through

bores

204 and 205 and

intopressure actuation chambers

217 and 218. The pressure is prevented from moving radially outward by

plugs

215 and 216 and therefore it acts inwardly against the

pistons

213 and 214 driving them against the mandrel teeth 210 thereby gripping the mandrel 208 and holding it in the packer assembly 203. I Since the packer anchors 4 and 5 are normally released by pulling upward on the tubing strings and thus on the mandrels, the angle of faces 210a on the mandrel teeth should be around 5 to 15 to allow upward movement of the mandrels upon application of external lifting force on the mandrels. Also, the pressure area of piston faces 213 and214 may be designed so that the gripping force of the piston teeth on the mandrel teeth is just equal to or slightly greater than the buoyant upward force on the mandrels so that little additional upward lifting of the mandrels'is required to wedge the piston teeth out of engagement with the mandrel teeth when unsetting the packer to remove it from the wellbore.

It should be noted that the back or lower edges 210bof the mandrel teeth are at a relatively flat angle compared to the upper faces 210a so that movement of the upper head upward on the mandrels is hardly impeded.

In addition to the hydraulic force on

pistons

213 and 214 it is clear that any known spring means such as coil springs could be compressed and placed in

chambers

217 and 218 to supplement the actuating pressure.

ALTERNATE EMBODIMENTS The packer apparatus 101 essentially comprises uppper connector assembly 102, upper head asembly 103,

cylindrical member. The upper portions of the dual bore passages have internal threads 112a for receiving

tubular sections

110 and 113.

Tubular receiving member 113 has an enlarged chamber area 114 attached to a standard tubular section or neck- 115 and containing an annular inwardly encircling member 110 is upper receiver dish 117 which is a generally cylindrical section having a concave upper face 121 and

dual bore passages

119 and 120 to receive member 110 and the secondarytubing string collet sleeve 118. Collet sleeve'118 is a tubular member having an annular shoulder 123 sized to abut slots 122 are formed through the wall to give the remainder of the sleeve flexibility and allow shoulder 123 to flex inward and traverse shoulder 116. A cylindrical, tubular seal carrier collar 124 is threadedly attached to Upper head 112 contains inner annular abutment ridges 112b in

bore passages

130 and 131 to receive in fitting relationship the primary and secondary Each

mandrel

107 and 108 has an annular exterior shear shoulder 107a and 108a for abutment with'and selective shear means for shear scr'ews 127 which project through the wall of head 1 12 and into the shear chamber 128 formed between head 112, shoulders 107a and 1080 and

mandrels

107 and 108.

A cylindrical abutment shell 129 is secured to head 112 by threaded bolts 1 32 passing through the head engaging shell 129 as shown in the disslidably telescoped over

mandrels

107 and 108. The milled sides are shown in cross section in FIG. 12 and the normal sides are shown in FIG. 10. FIG. 11d shows a cross-sectional axial view of one of the key-retaining

sleeves

133 and 134, and FIG. He shows a crosssectional axial view of a sleeve.

Shell 129 also consists of a thick wall area and a thin wall area as shown in FIGS. 11 and 12. The narrowed walls of shell 129 and of

sleeves

133 and 134 are to sleeves 135 and cally located within sleeves 135.

Sleeves 135 each have a small spring lip 135a onvthe abutment and retention of upper packer plate 137 to head 112. This prevents head 1 12 from floating upward on bolts 136 away from plate 137 and prematurely shearing of screws 127 while going in the hole with the tool.

134 are arranged so that slots in the sleeves are located directly over paralrarily locks the mandrels to the upper head assembly 103 by means of keys 140,

ridges

138 and 139 and

sleeves

133 and 134 and allows the operator to pick up on the string and reciprocate it to dislodge sediment or going in the hole. This propins 127 from premature shearing. Keys 140 are held within the slots in

sleeves

133 and 134 by abutof head 112. FIGSQlla and keys disassembled understanding of their structure.

The resilient packer assembly is located slidably about the

mandrels

107 and 108 below upper packer plate 137 and consists of resilient packer elements 141, rigid spacer plates 142 and lower packer plate 143.

A dual wedge-cone head 144 is abutted against lower plate 143 in encircling relationship about

mandrels

107 and 108 and wedge anchors 14S. Anchors 145 are wedge shaped inserts having a plurality of angled gripping teeth on their inner surface contacting the outer wall of the mandrels.

Movement upward of the anchor inserts 145 on the mandrels is possible because of the angle of the upper faces of the wedge teeth but movement downward on 110 gives views of the sleeves chor moves upward, will result in a pressing inward of more detailed view of the dual shown in FIGS. 16a and 16b.

Guide pins 146 slots l45b formed in the outer portron'of wedge inserts from the apparatus for a better

Claims

1. A unitary well tool anchor slip for ahchoring a well tool or well packer in the casing of an oil well, said slip comprising: a generally cylindrical tubular member having a dual axis bore passage therethrough; a plurality of gripping teeth having a curved boundary profile, said teeth being located on one side of said member near one end; a second plurality of gripping teeth having a curved boundary profile, said second plurality of teeth located on the opposite side of said member near the opposite end; an abutment shoulder located at one edge of one end of said member, said member end having a canted surface leading away from said abutment shoulder; and, a compound abutment surface on the member end opposite said abutment shoulder, said compound surface having a flat surface extending from the central cylindrical axis to the edge of said member containing said gripping teeth and a radially curved surface extending from said central axis to the opposite edge of said member end.

2. The anchor slip of claim 1 wherein said dual axis bore passage is arranged to contain a plurality of tubular mandrels therein and is further adapted to pivot about said mandrels on dual axes, with the first of said dual axes substantially coinciding with the central, longitudinal cylindrical axis of said anchor slip, and said second axis beng canted from said first axis at an angle of from 5 to 45*, with a preferable angle of about 18*.

3. The anchor slip of claim 2 wherein said member has a pivoting center of rotation along the central, longitudinal cylindrical axis of said member and located at a distance of one-half of the cylindrical length of said member from said flat surface, and the radius of curvature of said radially curved surface is equivalent to one-half the cylindrical length of said member, with said curved surface being tangent to said flat surface at said central cylindrical axis.

4. The anchor slip of claim 3 wherein said member further comprises a longitudinal slot passing through one side of said member from the inner bore to the outer surface thereof and extending only partially along said one side of said member; said slot arranged adjacent to a cylindrical spring slot formed into the remaining portion of said member wall and aligned substantially parallel with the central cylindrical axis of said member.

5. A uni-directional gripping member for use on one or more conduit strings in a wellbore, said gripping member adapted for gripping the wellbore in one direction of longitudinal movement of said member and further adapted to allow non-gripping movement of the member in either longitudinal direction in the wellbore comprising: a generally cylindrical tubular member having a first bore passage passing longitudinally there-through generally parallel to the longitudinal central axis thereof and adapted to receive said one or more conduit strings in slidable relationship; a second bore passage passing through said member and intersecting said first bore passage at an angle thereto, whereby said member can be pivoted on said conduits from a well-bore non-engaging position to a wellbore contact position whereby diametrically opposite edges of said member contact the wellbore simultaneously; gripping teeth on said member along said diametrically opposite edges of said member, said teeth arranged to contact and grip the wellbore upon pivoting of said member on said conduit string; a canted face on one end of said member, said face having an abutment surface thereon along the outer edge of said member arranged to abut a flat surface on said conduit string and introduce rotational moments in said member; and, a dual surface end on said member opposite said canted face end, said dual surface end having a flat surface normal to the central cylindrical axis of said member and a curved surface tangent to said flat surface at said central axis said curved surface being on the same side of said member as said abutment surface but longitudinally spaced therefrom, and said curved surface having a radius of curvature equal to the distance from the point of said tangency to the pivot center of said member.

6. The gripping member of claim 5 wherein said member has a cylindrical length which is substantially greater than the diameter of the wellbore and a cylindrical diameter smaller than the diameter of the wellbore, with said curved surface having a center of curvature coinciding with the pivot center of said member, said pivot center lying on the central, cylindrical longitudinal axis of said member and being a distance of one-half the cylindrical length of said member from said point of tangency.

7. The gripping member of claim 6 wherein said first and second bore passages are each adapted to receive two parallel, spaced apart, conduit strings and said second bore passage intersects said first bore passage at an angle of from 5 to 45*, with a preferable angle of from 16 to 20*.