Well Packer

Abstract

A single piece, tubular mandrel extends centrally through a closely surrounding composite outer body. The outer body includes metal anchoring slips and resilient packers to respectively anchor the outer body and supporting central mandrel to a surrounding well pipe and to seal the annular space formed between the mandrel and the surrounding well pipe. The outer body includes setting components which are moved axially by hydraulic setting pressure introduced through the mandrel into expandable chamber means formed in the outer body. The setting components wedge under the anchoring slips and axially foreshorten the packer, forcing the slips and packer radially outwardly into engagement with the surrounding well conduit. Reverse axial movement of the setting components is prevented by a one-way acting friction lock which retains the anchoring slips and packer in engagement with the well conduit even after reduction of the hydraulic setting pressure. The anchoring slips and packers are released from their set position by moving the mandrel axially with respect to the expanded slips and packer in the outer body. Undesired relative movement of the mandrel is prevented by a pressure expanded, normally retracted mechanical hold-down linkage extending between the mandrel and the set outer body. In the absence of a pressure differential across the set packer, the mechanical linkage returns to a normally retracted position which provides no obstacle to relative movement between the mandrel and outer body. In the preferred form of the invention, the hold-down linkage includes a series of radially movable pistons acting against a resilient snap ring to retain the snap ring in engagement with a groove in the outer body. In a modified form, the hold-down linkage is an outwardly biased annular ring having internal grooves adapted to mate with external grooves formed on the mandrel. The ring is moved toward the mandrel by axially movable, tapered wedging means driven by hydraulic pressure.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to expandable packer tools employed for forming pressure seals within conduits. More specifically, the present invention relates to hydraulically set, retrievable well packers which may be employed in oil and gas wells to form a pressure seal in the annular area formed between a tubular well conduit such as production tubing and a surrounding conduit such as well casing.

2. Brief Description of the Prior Art

U.S. Pat. No. 3,361,209 assigned to the assignee of the present invention discloses a hydraulically set well packer tool which is particularly adapted for use in "multiple completion" wells employed to produce a series of vertically separated petroleum bearing formations penetrated by a single well bore. The packer of the foregoing patent includes a central tubular body or mandrel about which is mounted a composite outer body including metallic anchoring slips and a resilient sealing means. The slips and seal are set within the well conduit by introducing a relatively high hydraulic pressure into the tool mandrel which is concentrically mounted with and forms a part of the production tubing string. The setting pressure is communicated to an expandable chamber in the outer body to move the setting components of the outer body axially causing the desired radial expansion of the seals and slips. The packer is then released by moving the mandrel of the packer axially with respect to anchored components of the outer body to sever a connecting shear pin which permits relative movement between components of the packer. The relative axial movement between the mandrel and the anchored outer body is generally imparted by raising the tubing string through the casing with the result that the packer has been termed a "straight-pull release packer."

Because of restrictions imposed by various governmental agencies controlling oil and gas production, simultaneous production of several vertically spaced formations is often prohibited, and the lowermost formation in such multiple completion wells must be produced first. Single formation production requires that each of the vertically separated producing formations be separated by means of suitable packers set in the well conduit so that production fluid may selectively be permitted to enter the production tubing from any given one of the vertically spaced formations. After production is completed in the lowermost formation, the tubing extending down into such formation is plugged by means of any suitable plugging means and the next higher formation is then produced. This procedure is repeated until each of the succeedingly higher zones is produced whereupon the packers are released and retrieved from the well along with the production tubing.

In the past, there have been difficulties associated with plugging of the lowermost packer in multiple completion wells since the pressure in the lower formation acts against the entire cross sectional area of the tubing at the point where the mandrel extends through the packer. The increase in effective area exposed to the formation pressure permits the formation pressure to exert an upwardly directed force on the packer mandrel which in turn results in an upward movement relative to the set seal and anchor slips of the packer. This action duplicates the retrieval action for the tool and thus causes undesirable release of the packer before the next higher zone has been fully produced.

SUMMARY OF THE INVENTION

The hydraulically set, retrievable production packer of the present invention includes a pressure actuated locking linkage which mechanically locks the mandrel to relatively movable components in the outer body of the packer to prevent inadvertent release of the packer by pressure induced forces. When the pressure differential across the set packer falls below a predetermined minimum value, below that necessary for pressure induced release, the linkage automatically releases the mandrel to permit normal retrieval by straight pulling of the tubing from the surface.

Basically, the packer of the present invention includes a tubular central mandrel extending through a closely surrounding body which includes metallic anchoring slips, cone spreaders adapted to expand the slips radially into engagement with the surrounding well tubing or casing and a radially expandable seal assembly adapted to engage with and seal the annulus between the mandrel and the casing. The packer is hydraulically set by increasing the hydraulic pressure within the production tubing string with the increased pressure acting through a port in the mandrel to expand a pressure chamber in the outer body causing sequential severing of shear pins employed to retain the outer body members in retracted position. The resulting relative axial movement of the outer body members moves the cones under the slips and compresses the resilient sealing means to provide the desired anchor and seal in the casing.

After use, the packer tool of the present invention is retrieved by pulling upwardly on the tubing string which moves the mandrel of the packer axially relative to the set slips and sealing means to shear a release pin. Rupture of the shear pin permits relative axial movement between the tool components permitting retraction of the slips and sealing assemblies. A back-up release mechanism is provided by the interlocking of left hand threads in the outer body whereby rotation of the tubing string to the right separates the packing components to permit relative axial movement between the set anchor slips and sealing assemblies to thereby permit retrieval of the packer.

The set packer tool is held in position subsequent to plugging of the mandrel by a mandrel hold-down assembly which includes pressure actuated, radially movable pistons adapted to expand a resilient snap ring into mechanical engagement with portions of the outer body. The mandrel hold-down assembly prevents relative movement between releasing components of the packer to thereby prevent undesired shearing of the release pin. The radially movable pistons of the hold-down assembly are moved outwardly anytime the formation pressure is greater than the pressure in the annulus above the set packer to ensure mechanical interlock under pressure conditions tending to move the mandrel upwardly through the set anchor slips and sealing assembly. Thus, the mandrel hold-down means of the present invention is automatically actuated under pressure conditions permitting inadvertent release of the bottom packer.

In a modified form of the invention, an axially movable piston is employed to wedge a resilient snap ring into locking engagement with the mandrel any time the pressure in the formation below the sealed packer is greater than in the annulus above the packer. When the pressure differential across the packer seal is substantially zero or the pressure is greatest from above, the resilient ring automatically releases the mandrel. In the event the mandrel hold-down is engaged when release of the packer is desired, the annular area above the packer seal is pressured to a pressure value equal to or above that existing below the set packer. By such means, the hold-down assembly in both forms of the present invention is returned to its normally released position permitting relative movement between the releasing components of the packer with an upwardly directed force, or a rotating action as the case may be, exerted from the well head.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a quarter sectional view, partially in elevation, illustrating the well packer of the present invention as it appears in its radially contracted condition preliminary to being set in a surrounding well conduit;

FIG. 2 is the tool of FIG. 1 illustrated in its radially expanded condition, set within the surrounding well conduit;

FIG. 3 is the upper portion of the tool of the present invention illustrating the mandrel hold-down assembly in its activated or locked condition;

FIG. 4 is a modified form of the present invention illustrating a modified mandrel hold-down assembly in released condition;

FIG. 5 is the tool of FIG. 4 illustrating the hold-down assembly in locked condition;

FIG. 6 is a horizontal cross-sectional view taken along line 6--6 of FIG. 2;

FIG. 7 is a horizontal cross-sectional view taken along line 7--7 of FIG. 3;

FIG. 8 is a horizontal cross-sectional view taken along line 8--8 of FIG. 4; and

FIG. 9 is a horizontal cross-sectional view taken along line 9--9 of FIG. 5 .

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIG. 1, the well packer tool of the present invention is indicated generally at 10 as it appears in its unset condition within a surrounding well conduit C. FIG. 2 illustrates the tool 10 in set condition. It will be understood that the conduit C may be a well casing or a tubing string extending down through the well casing. The packer tool 10 includes a one piece, central mandrel 11 which is threadedly engaged at its upper end (not shown) and lower end with a tubing string T. The tubular bore of the mandrel 11 is concentric with and forms a continuation of the tubular bore of the tubing string T. A composite outer body disposed about the mandrel 11 includes a plurality of metallic anchoring slip segments 12 and two resilient elastomeric packer seals 13 and 14.

As will be seen, during the setting of the packer tool 10, relative axial movement between components in the outer body of the tool radially expands the slip segments 12 and the seals 13 and 14 into engagement with the surrounding conduit C to respectively anchor the mandrel 11 and outer body to the conduit C and to form a complete seal between the mandrel and conduit. During the setting action, the slip segments 12 are spread radially outwardly by means of an upper cone spreader 15 and a lower cone spreader 16 which, when moved axially toward each other move under internally tapered surfaces of the slip segments 12 to wedge the segments outwardly into locking engagement with the conduit C. As will also be seen, upper and lower bearing members 17 and 18 respectively are adapted to move axially toward each other during the setting of the packer tool 10 to axially foreshorten the sealing elements 13 and 14 causing them to expand radially into engagement with the well conduit to provide the desired seal. An annular, axially movable dual taper element 19 disposed between the two sealing elements 13 and 14 provides separation between the seals and assists in directing the seals into proper sealing engagement with the surrounding well conduit. Downward axial movement of the element 19 is limited by an annular shoulder formed on the internal circumferential area of the element which is adapted to engage an annular stop ring 20. The ring 20 limits only the downward movement of the element 19 to ensure proper positioning of the upper sealing member 14 and, as may be seen by reference to FIG. 2, to permit the seal 14 to be moved axially upwardly during the compression and radial expansion of both of the seals.

The tool 10 of the present invention is hydraulically set with the desired axial setting movement of the cone spreaders 15 and 16 and the seal bearing members 17 and 18 being effected by increasing the hydraulic pressure of fluid contained within the central bore of the mandrel 11 and tubing string T. When setting is desired, a suitable plugging member P is pumped down the tubing string T until it engages an annular seat S formed internally of the tubing below the mandrel 11. With the plug P positioned as illustrated in FIG. 2, the hydraulic pressure of the fluid within the mandrel 11 may be increased from the well surface to produce the required setting movement.

During the setting procedure, the hydraulic pressure existing within the mandrel 11 is communicated into the outer body of the packer tool 10 through a radial bore 11a extending through the mandrel wall. The bore 11a communicates with a pressure activated expansion chamber 21 formed between movable components in the outer body of the packer tool. As best illustrated by joint reference to FIGS. 1 and 2, the expansion chamber 21 is formed in the annular space bounded between a tubular sleeve 22 and a second radially spaced tubular housing sleeve 23. The lower surface of the chamber 21 is formed by an annular spacing collar 24 which is threadedly engaged between the tubular members 22 and 23. The upper surface of the chamber 21 is formed by a composite movable assembly which includes an annular piston 25 designed to slide axially between the tubular sleeve 22 and the lower internal wall of the spreader cone 16. The piston 25 is retained in position between the sleeve 22 and the cone spreader 16 by means of an annular snap ring 26 which is set in an annular groove formed on the internal cylindrical surface at the spreader base. A sliding seal is maintained between the sleeve 22 and the piston 25 by means of an O-ring 27 with a similar sliding seal being formed between the piston 25 and the internal surface of the cone spreader 16 by means of an O-ring 28. An O-ring 29 forms a sliding seal between the outer surface of the cone spreader 16 and the inner surface of the housing sleeve 23 whereby the piston 25 and the cone spreader 16 cooperate to form a pressure-tight, axially movable upper surface to the expansion chamber 21. In addition to the seal at the upper end of the expansion chamber, the chamber is further sealed by means of O-rings 30, 31 and 32 with the O-rings 30 and 31 forming a sliding seal between the outer body components and the mandrel 11 and the O-ring 32 sealing the threaded connection between the spacing collar 24 and the housing sleeve 23.

In the setting components of the outer body, helical springs 35 positioned between the slip segments 12 and a retaining cage 34 bias the slip segments radially inwardly to a normally retracted position. Pins 16a and 15a extend radially from the cone spreader 16 and 15 respectively into axially extending slots 34a formed in the cage 34 for maintaining suitable alignment between the movable components of the outer body. During the setting of the packer 10, expansion of the chamber 21 under the influence of hydraulic pressure moves the piston 25 and the lower cone 16 upwardly. The initial upward movement of the spreader cone 16 severs a shear pin 33 connecting the housing sleeve 23 with the cone 16. Continued upward movement of the cone 16 advances the cone over the sleeve 22 and under the concavely tapered internal surfaces of the slip segments 12. The upward movement of the cone spreader 16 begins to move the slip segments 12 outwardly against the biasing force of the springs 35 and the segments 12 continue to move radially outwardly until a collar 36 secured to the lower cone spreader 16 by means of a shear pin 37 engages the lower ends of the slip segments 12. Continued upward movement of the spreader 16 moves the slip members 12 upwardly through the cage 34 causing the upper end of the slip member 12 to engage an annular collar 38 secured to the upper cone spreader by means of a shear pin 39. With the collars 36 and 38 engaging the slip segments 12 and with the shear pins 37 and 39 intact, upward movement of the cone spreader 16 is transmitted through the slips 12 to the upper cone spreader 15 and to the lower bearing member 18 to compress and radially expand the seals 13 and 14. By this means, the seals 13 and 14 are set before the slips 12 engage the surrounding walls of the conduit C. When the seals 13 and 14 have firmly engaged the walls of the surrounding conduit C, continued upward movement of the upper cone spreader 15 and attached collar 38 is prevented, resulting in severance of the shear pin 39. When the pin 39 has sheared, continued upward movement of the cone spreader 16 advances the slip segments 12 over the tapered surface of the cone spreader 15 causing them to move radially outwardly against the biasing force of the spring 35 into engagement with the walls of the conduit C. With the slips thus set, continued upwardly directed movement of the cone spreader 16 forces the slips 12 into firm locking engagement with the walls of the conduit C locking the slips in place and causing the pin 37 connecting the collar 36 to the cone spreader 16 to shear.

During the previously described setting action, the upward movement of the piston 25 in the upper assembly of expansion chamber 21 acts to move an annular tapered locking ring 40 upwardly with the upward movement of the assembly. Hydraulic pressure acting against the piston 25 drives the locking ring 40 into wedging engagement between the external surface of the sleeve 22 and a tapered internal surface formed on the cone spreader 16 to prevent downward movement of the spreader 16 relative to the tubular member 22. It will be appreciated that downward motion of the locking ring 40 is prevented by the frictional engagement formed between circumferentially extending teeth provided on the internal surface of the locking ring which engage and dig into the external surface of the sleeve 22. The lock ring 40 therefore acts to maintain the components of the packer tool 10 in set position even after the hydraulic pressure in the chamber 21 has been relieved.

MANDREL HOLD-DOWN ASSEMBLY

A mandrel hold-down assembly indicated generally at 41 is included with the packer 10 of the present invention for the purpose of preventing undesired release or unsetting of the tool. The assembly 41 mechanically locks the relatively movable components of the outer body to the mandrel 11 to prevent undesired, pressure induced movement between the mandrel 11 and the outer body components. The hold-down assembly 41 includes a plurality of cylindrical, radially movable pistons 42 which are adapted to be moved radially outwardly under the influence of a pressure differential existing between the annular areas A--1 and A--2, respectively below and above the seals 13 and 14. As illustrated in FIGS. 3 and 7, movement of the pistons 42 forces a split, annular snap ring 43 into locking engagement with a groove 44 formed in a tubular housing member 45 positioned at the upper portion of the outer body. The mechanical interlock between the mandrel 11 and housing 45 prevents severance of a release shear pin 46 extending between the housing 45 and a piston bore sleeve 47 threadedly engaged along its upper circumferential area with the mandrel 11. The lower circumferential surface of the housing 45 is threadedly engaged with an annular connecting member 48 which in turn is threadedly engaged with the upper bearing member 17 and a tubular sleeve 49. The sleeve 49 telescopes over the mandrel 11 and is releasably attached to the lower sleeve 22 to form part of the release mechanism of the packer tool as will subsequently be more fully described.

When the tool 10 is set, the pressure existing in the annular well area A--1 is communicated past the seals 13 and 14 to the hold-down assembly 41 by means of a path described by radial bores 15a extending through the upper cone spreader 15, longitudinal slots 22a formed in the lower sleeve 22, and an annular space formed between the mandrel 11 and the composite structure formed by the upper tubular connecting member 49, the member 48 and the piston sleeve member 47. The pressure conducting path extending from the area A--1 to the hold-down assembly 41 is maintained pressure-tight by means of O-rings 50, 51, 52, 53 and 54 with a pressure seal being maintained between the radially movable pistons 42 and the piston bore sleeve 47 by means of O-rings 55.

OPERATION OF THE WELL PACKER

With joint reference to FIGS. 1 and 2, the packer 10 of the present invention is lowered into the conduit C as an integral part of the tubing string T with one or more vertically spaced packers being included in the tubing string as desired. When the string T and included packers 10 have been properly placed vertically in the well conduit C, a plug P is set in the tubing to permit the tubing pressure to be increased. The density of the plug P is such that the plug is buoyant in the hydraulic fluid employed to pressurize the tubing T thus permitting the plug to "float" to the well surface after the packer tools have been set. It will be understood that other plugs, such as a tapered plug member having annular O-rings and adapted to engage a suitable seat formed within the tubing T or mandrel 11 may also be employed. Similarly, different plugs may be employed for selective setting of only certain ones of the packers included in the tubing string.

Once the plug P has been set in the seat S, the pressure of the hydraulic fluid in the tubing T is increased from the well surface by a suitable pump or other means. The increasing hydraulic pressure within the mandrel 11 is communicated through the mandrel bore 11a to the expansion chamber 21 to exert an upwardly directed force on the lower cone member 16 which causes the pin 33 to shear. Once pin 33 has sheared, the cone spreader 16 is permitted to move upwardly through the outer housing sleeve 23 to slide under the slip segments 12 until the lower end of the slip segments engage the lower collar 36 attached to the cone spreader 16. Continued upward movement of the cone spreader moves the slip segments 12 axially upwardly into engagement with the upper collar 38 secured to the upper cone spreader 15. With the collars 38 and 36 engaging the spreader 12 and with the shear pins 39 and 37 intact, continued upward movement of the cone spreader 16 produces no further radial expansion of the slip segments 12 and an upward force is exerted against the upper cone spreader 15 causing the spreader and attached bearing member 18 to move axially upwardly.

The upward movement of bearing member 18 compresses the sealing members 13 and 14 causing them to expand radially outwardly into contact with the surrounding surface of the conduit C. When the seals 13 and 14 have been firmly seated against the conduit C, continued upward movement of the bearing member 18 and cone spreader 15 is essentially terminated and continued upward force exerted by the slip segments 12 severs the shear pin 39 to permit the collar 38 to move axially upwardly over the cone spreader 15. Once the pin 39 has sheared, the two cone spreaders 15 and 16 are permitted to advance axially toward each other which in turn expands the slip segments radially outwardly against the biasing force of the springs 35 and into engagement with the surrounding walls of the conduit C. When the slip segments 12 have firmly engaged the well conduit C, further axial movement of the segments is prevented and continued upward movement of the lower cone spreader 16 severs the pin 37 permitting the cone spreader 16 to continue to move under the slips 12 to firmly set them against the conduit C.

With the well packer 10 set as previously described, the hydraulic pressure induced from the well head may be relieved. Once such pressure is relieved, the cone spreader 16 is no longer driven upwardly by pressure existing within the expansion chamber 21 and tends to move axially downwardly. The locking ring 40 which is also driven axially upwardly under the influence of the pressure existing in the expansion chamber 21 acting through the annular piston 25, is wedged radially inwardly by the cooperating tapered surfaces between the cone spreader 16 and the ring 40 causing the downwardly pitched teeth of the lock 40 to dig into and frictionally lock with the sleeve 22. By this means, the frictional locking engagement of the lock ring 40 prevents the cone spreader 16 from moving axially downwardly to thus retain the packer 10 in its set condition irrespective of the pressure existing in the expansion chamber 21. When the packing members 13 and 14 are sealed against the conduit C, the pressure in the annular space A--1 is communicated behind the set sealing members to the mandrel hold-down assembly 41. With the pressure in the well area A--1 greater than that in the area A--2, the snap ring 43 and tubular member 45 are thus mechanically engaged to prevent relative axial movement between the tubular member 45 and the mandrel 11. By this means, the components of the packer 10 are held fixed relative to each other by the automatic action of the mandrel hold-down assembly 41 to prevent pressure induced relative movement between the mandrel 11 and the outer body components which, if unchecked, would sever the pin 46 causing release and unsetting of the packer 10.

RELEASE OF THE WELL PACKER

When it is desired to retrieve the well packer from the conduit C, the mandrel 11 must be moved axially upwardly with respect to the set seals 13 and 14 and slip segments 12. The retrieving action is normally effected by raising upwardly on the tubing string T and attached mandrel 11 to sever the shear pin 46 which permits the desired axial movement between the mandrel 11 and the slips and seals. It will be appreciated that axially upwardly directed movement of the mandrel 11 is prevented when the snap ring 43 is in engagement with the groove 44. As previously described, engagement of the snap ring 43 and groove 44 occurs when the pressure in the annular area A--2 is less than the pressure in the area A--1 below the set packer. When retrieval of the packer is desired under the foregoing pressure conditions, the area A--2 is pressurized from the well surface to raise the pressure in the area up to or above that existing in the annular area A--1. Once the pressure differential has thus been eliminated or reversed, the piston 42 is permitted to move radially inwardly under the biasing force of the resilient split ring 43 to the position illustrated in FIGS. 1, 2 and 6. With the ring 43 thus radially retracted, the upwardly directed forces exerted from the surface on the mandrel 11 are effective to sever the pin 46, permitting the mandrel 11 to be moved axially upwardly with respect to the outer body of the packer.

Relatively small axial movement between the mandrel 11 and the outer body draws a recessed mandrel area 11b under the joint between the two connecting sleeve members 49 and 22. With the recess 11b below the joint area of the two sleeve members, the slotted upper portion of sleeve 22 is free to move radially inwardly into the recess 11b, permitting the upper sleeve 49 to separate and be moved axially upwardly. It will be appreciated that upward movement of the sleeve 22 is prevented by the cooperating wedging of the lock ring 40, lower cone spreader 16 and slips 12. An annular ridge 11c formed at the upper portion of the mandrel 11 is adapted to engage the tubular member 45 in the outer body so that continued upward movement of the mandrel 11 draws the sleeve 45, connecting member 48 and sleeve 49 upwardly which separates the two bearing members 17 and 18 to permit retraction of the packers 13 and 14. Continued upward mandrel movement engages the lower end of the sleeve 49 with the lower bearing member 18 to pull the cone spreader 15 out from under the set slip segments 12. Once the upper cone spreader 15 has been pulled away from the slip segments, the segments are free to return to their radially retracted position under the influence of the compressed springs 35 to completely release the tool from the surrounding well conduit C.

As a back-up or alternative release means, the tool 10 is adapted to be retrieved by imparting a rotational movement to the tubing string T from the well head to rotate the mandrel 11c causing it to unthread from its engagement with the piston cylinder sleeve 47. It will be appreciated that in the normally anticipated application, the cooperating threads between the cylinder sleeve 47 and mandrel 11 are left hand whereby a right hand rotation (as viewed looking downwardly from the well head) effect separation of the two mating components without releasing the adjoining pipe segments forming the tubing string T. Once the mandrel 11 has been separated from the sleeve 47, the mandrel is free to move relative to the outer body even with the shear pin 46 intact and the lock ring 43 engaged in the groove 44. When the mandrel 11 and cylinder sleeve 47 have been separated, retrieval of the tool follows the same process as previously described.

MODIFIED HOLD-DOWN ASSEMBLY

FIGS. 4, 5, 8 and 9 illustrate a modified form of the mandrel hold-down assembly which may be employed with the packer of the present invention. With the exception of the hold-down assembly and the alternate release means to be described, the packer tool 110 illustrated in FIGS. 4, 5, 8 and 9 is the same as the previously described packer tool 10. Similar components in the modified packers have been designated by numbers of 100 or above which include as the last two digits the same numerals as the corresponding or similar segment in the packer tool 10. With reference to FIGS. 4 and 8, the modified hold-down assembly indicated generally at 141 includes an annular, axially movable piston 142 sealed by means of O-rings 155a and 155b between the mandrel 111 and the outer tubular housing member 145 respectively. After the packer has been set in the manner described with reference to the packer tool 10, the pressure existing in the area below the set seals acts through the annular space formed between the mandrel 111 and the sleeve member 149 and connecting member 148 to move the annular piston 142 axially upwardly into engagement with the annular, split snap ring 143. It will be understood that the O-rings 155a, 155b, 153, 152 and 150 cooperate with the set seals of the tool to maintain a continuous seal between the mandrel and the walls of the conduit C. When the piston 142 is moved axially upwardly, the internally tapered surface of the piston engages the lower tapering surface of the snap ring 143 which moves the ring 143 radially inwardly into engagement with the mandrel 111. Threads 143a formed on the internal surface of the snap ring 143 engage and lock with threads 111d formed on the external surface of the mandrel 111. The engagement of the snap ring 143 and mandrel 111 prevents relative movement between the mandrel and the outer body components to retain the packer 110 in set position.

The engaged position of the snap ring 143 and mandrel 111 is illustrated in FIGS. 5 and 9. When release of the tool 110 is desired, the mandrel 111 is rotated to the right by means of force applied at the well head. Rotation to the right (clockwise as viewed looking down from the well head) separates or unthreads the left hand mandrel threads 111d from the mating snap ring threads 143a to raise the threads 143a axially above the snap ring 143. During the rotation of the mandrel 111, rotation of the snap ring 143 is prevented by means of an index pin 180 which, as best illustrated in FIGS. 8 and 9, extends through the tubular body member 145 and into the ring 143. When the mandrel 111 has been separated from the ring 143, retrieval of the packer tool 110 may be effected in the manner previously described with reference to the well packer tool 10. It will be appreciated that in the modified form of the invention illustrated in FIGS. 4, 5, 8 and 9, release of the tool is possible without having to increase the pressure in the annular area A--2 to or above that existing below the set packer seals.

As an alternate release means for the tool 110, the annular area A--2 may be pressured to a pressure value above that existing below the packer seals. The increased pressure existing in the area A--2 is transmitted through the opening in the tubular member 145 housing the index pin 180 to drive the piston 142 downwardly away from locking engagement with the snap ring 143. Thereafter, an upwardly directed pull on the mandrel 111 will bias the radially unrestricted snap ring open to permit the mandrel teeth 111d to slide freely over the snap ring teeth 143a which frees the mandrel to permit complete release of the packer 110.

The foregoing disclosure and description of the invention is illustrative and explanatory thereof, and various changes in the size, shape and materials as well as in the details of the illustrated construction may be made within the scope of the appended claims without departing from the spirit of the invention.

Claims

I claim:

1. A well tool adapted to be set in a surrounding well conduit comprising:

a. anchoring means for selectively engaging said well conduit to anchor said tool to said conduit;

b. sealing means included with said tool for selectively engaging said well conduit to form a seal between said tool and said conduit whereby the area in said well conduit at the first end of said sealing means is sealed away from the area in said well conduit at the second end of said sealing means;

c. releasable locking means included with said tool for locking said anchoring means and said sealing means in engagement with said well conduit;

d. pressure sensitive hold-down means included with said tool for selectively locking said anchoring means and said sealing means in engagement with said well conduit when the pressure at said first sealing means end is less than the pressure at said second sealing means end to prevent pressure induced release of said releasable locking means;

e. tubular support means extending centrally through said anchoring means and said sealing means;

f. pressure actuated setting means mounted on said tubular support means for setting said anchoring means and said sealing means in said well conduit by moving said anchoring means and said sealing means into gripping and sealing engagement with said well conduit to respectively hold said tool against axial movement in said conduit and to form a pressure seal between said tubular support means and said conduit; and

g. releasing means included with said releasable locking means and connecting said setting means and said tubular support means whereby axial movement of said tubular support means unsets said tool by releasing said anchoring means and said sealing means from engagement with said well conduit.

2. The tool as defined in claim 1 wherein said hold-down means includes:

a. pressure communication means extending within the well tool between said second sealing means end and said hold-down means and opening into the well conduit area adjacent said second sealing means end for communicating the pressure in said well conduit at said second sealing means end to said pressure sensitive hold-down means; and

b. movable actuating means connected with said pressure communication means and movable when the pressure at said first sealing means end is less than the pressure at said second sealing means end to mechanically lock movable components of said tool to each other to prevent relative movement between said components.

3. The tool as defined in claim 1 wherein said releasing means includes threads carried by said tubular support means cooperating with threads carried on said setting means whereby rotation of said tubular support means releases said cooperating threads to permit said tubular support means to be moved axially to unset said tool.

4. The well tool as defined in claim 3 wherein said hold-down means includes:

a. pressure communication means extending within the well tool between said second sealing means end and said hold-down means and opening into the well conduit area adjacent said second sealing means end for communicating the pressure in said well conduit at said second sealing means end to said pressure sensitive hold-down means; and

b. movable actuating means connected with said pressure communication means and movable when the pressure at said first sealing means end is less than the pressure at said second sealing means end to mechanically lock movable components of said tool to each other to prevent relative movement between said components.

5. The well tool as defined in claim 4 wherein said movable actuating means includes radially movable piston means adapted to move a resilient snap ring radially.

6. The well tool as defined in claim 4 wherein said movable actuating means includes axially movable annular piston means adapted to engage and move a resilient snap ring radially.

7. The tool as defined in claim 3 wherein said release means further includes severable connecting means securing said tubular support means to said setting means for preventing relative movement between said support means and said setting means with said connecting means being severable by axial movement of said support means to unset said tool.

8. The well tool as defined in claim 7 wherein said hold-down means includes:

a. pressure communication means extending within the well tool between said second sealing means end and said hold-down means and opening into the well conduit area adjacent said second sealing means end for communicating the pressure in said well conduit at said second sealing means end to said pressure sensitive hold-down means; and

b. movable actuating means connected with said pressure communication means and movable when the pressure at said first sealing means end is less than the pressure at said second sealing means end to mechanically lock movable components of said tool to each other to prevent relative movement between said components.

9. The well tool as defined in claim 8 wherein said movable actuating means includes radially movable piston means adapted to expand a resilient snap ring radially outwardly.

10. The well tool as defined in claim 8 wherein said movable actuating means includes axially movable annular piston means adapted to engage and compress a resilient snap ring radially inwardly.

11. A well tool adapted to be set in a surrounding well conduit comprising:

a. anchoring means for selectively engaging said well conduit to anchor said tool to said conduit;

b. sealing means included with said tool for selectively engaging said well conduit to form a seal between said tool and said conduit whereby the area in said well conduit at the first end of said sealing means is sealed away from the area in said well conduit at the second end of said sealing means;

c. releasable locking means included with said tool for locking said anchoring means and said sealing means in engagement with said well conduit;

d. pressure sensitive hold-down means included with said tool for selectively locking said anchoring means and said sealing means in engagement with said well conduit when the pressure at said first sealing means end is less than the pressure at said second sealing means end to prevent pressure induced release of said releasable locking means;

e. pressure communication means in said hold-down means extending within the well tool between said second sealing means end and said hold-down means and opening into the well conduit area adjacent said second sealing means end for communicating the pressure in said well conduit at said second sealing means end to said pressure sensitive hold-down means;

f. movable actuating means connected with said pressure communication means and movable when the pressure at said first sealing means end is less than the pressure at said second sealing means end to mechanically lock movable components of said tool to each other to prevent relative movement between said components; and

g. radially movable piston means included in said movable actuating means adapted to move a resilient snap ring radially.

12. A well conduit adapted to be set in a surrounding well conduit comprising:

a. anchoring means for selectively engaging said well conduit to anchor said tool to said conduit;

b. sealing means included with said tool for selectively engaging said well conduit to form a seal between said tool and said conduit whereby the area in said well conduit at the first end of said sealing means is sealed away from the area in said well conduit at the second end of said sealing means;

c. releasable locking means included with said tool for locking said anchoring means and said sealing means in engagement with said well conduit;

d. pressure sensitive hold-down means included with said tool for selectively locking said anchoring means and said sealing means in engagement with said well conduit when the pressure at said first sealing means end is less than the pressure at said second sealing means end to prevent pressure induced release of said releasable locking means;

e. pressure communication means in said hold-down means extending within the well tool between said second sealing means end and said hold-down means and opening into the well conduit area adjacent said second sealing means end for communicating the pressure in said well conduit at said second sealing means end to said pressure sensitive hold-down means;

f. movable actuating means connected with said pressure communication means and movable when the pressure at said first sealing means end is less than the pressure at said second sealing means end to mechanically lock movable components of said tool to each other to prevent relative movement between said components; and

g. axially movable annular piston means included in said movable actuating means adapted to engage and move a resilient snap ring radially.