Automatically vented fluid pressure operated apparatus

July 16, 1957 m. b. conrad 2,799,343

AUTOMATICALLY VENTED FLUID PRESSURE OPERATED APPARATUS

Filed June 20, 1955 2 Sheets-Sheet 1

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INVENTOR.

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July 16, 1957

Μ. B. CONRAD

2,799,343

AUTOMATICALLY VENTED FLUID PRESSURE OPERATED APPARATUS

Filed June 20, 1955

Sheets-Sheet 2

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United States Patent Office Patented July 16, 1957

2,799,343

AUTOMATICALLY VENTED FLUID PRESSURE OPERATED APPARATUS

Martin B. Conrad, Downey, Calif., assignor to Baker Oil Tools, Inc., Los Angeles, Calif., a corporation of California

Application June 20, 1955, Serial No. 516,478

Claims. (Cl. 166—63) ing, Fig. lb forming a lower continuation of Fig. la, and Fig. la forming a lower continuation of Fig. 1, the parts occupying a position in which the well packer portion of the apparatus has been anchored in packer-off condition in the well casing;

Fig. 2 is an enlarged longitudinal section through a portion of the apparatus for releasing the pressure therewithin, the parts occupying the position just prior to release of the pressure;

Fig. 3 is a longitudinal section similar to Fig. 2, disclosing the parts in the position they occupy when the pressure has been released.

The invention is shown in the drawing as applied to a setting tool C releasably secured to a well packer A anchored in packed-off condition against the well casing B, the setting tool being attached to the lower end of the running-in string D, such as a wire line, extending to the top of the well bore. It is to be understood, however, that the invention has wider applications than is specifically disclosed, and that the setting of the well packer is merely illustrative of the invention.

The apparatus disclosed in the drawings may take the form specifically described and illustrated in the patent to Martin B. Conrad, 2,618,343, patented November 18, ²⁵ 1952, for “Gas Pressure Operated Well Apparatus,” to which attention is directed for certain details of construction and relative locations of parts which are not specifically disclosed in the present application. In both the patent and the present application, a well packer A ³⁰ is shown anchored in packed-off condition within a well casing. This well packer includes a tubular main body 10 whose central passage 11 may be closed by a plug 12. A guide 13 is secured to the lower end of the body to prevent the tool from catching or hanging up in the cas³⁵ ing or coupling spaces during its lowering in the well casing B.

The well packer has been anchored against downward movement in the well casing by a plurality of lower segmental slips 14 engaging the guide 13 and the lower 16 of the slips are tapered in a downward and inward direction for slidable engagement with a corresponding or externally tapered surface 17 on a frusto-conical expander 18 slidable on the body. This expander is connected to the lower end of a packing sleeve 19 of rubber or similar material disposed around the body 10, the upper end of this packing sleeve being connected to an upper expander 20 having an upwardly and inwardly inclined externally tapered surface 21 having wedging engagement with corresponding tapered surfaces 22 on a plurality of upper segmental slips 23.

Initially, the slips 14, 23 and packing element .19 are retained in retracted position with respect to the packer Shear screws 24, 25, or other suitable frangible connecting elements, secure the upper and lower expanders 20,18 to the body, with the intervening packing sleeve held in retracted position. The upper and lower slips 23, 14 are also held in retracted position by shear screws 26, 27 attaching them to their associated upper and lower expanders 20, 18.

The shear screws 26 attaching the upper slips 23 to the upper expander 20 have a combined shear strength which is substantially less than the shear value of the screws fatter screws have a lesser shear value than the screws 25, 27 securing the lower expander 18 to the body and the lower slips 14 to the lower expander. These relative shear values are selected to secure detachment, at first, 70 of the upper slips 23 from the upper expander 20, and the movement of the upper slips downwardly along the upper expander and radially outward into anchoring en10

The present invention relates to subsurface apparatus adapted to perform certain desirable operations in oil, gas and similar oil wells.

Certain types of well apparatus are operated in well bores by utilizing a gaseous medium under pressure to supply the necessary motivating force. As an example, a well packer may be set in a well bore through the exertion of a gaseous force thereon that might be present in a setting tool attached to the well packer, the setting tool being released from the latter after it has been set.

Heretofore, care had to be exercised in disassembling the setting tool after it has been retrieved from the well bore to assure release and bleeding off of the gas pressure trapped within the tool. At times, which fortunately occurred very infrequently, dismantling of the setting tool has been attempted improperly without first releasing the gas pressure in the tool, allowing the gas pressure to forcibly and suddenly separate the partially dismantled tool parts, and possibly injuring persons or damaging property.

Accordingly, it is an object of the present invention to provide gas pressure operated subsurface apparatus, of improved and comparatively simple construction, from which the gas pressure is released automatically following the performance of the required operations in the -.- —=-=-° -- “j ' tu r well bore thereby eliminating the danger of accident abutment or flange 15 on the body. The inner surfaces when the’apparatus is dismantled improperly following .....- ”-----------^{J J}--------¹ its removal from the well bore.

Another object of the invention is to provide a setting tool for a well packer to be set in a well bore, in which the setting tool is operated by gas pressure, and in which the eras pressure is released automatically after the well packer has been set, the gas pressure release feature of the setting tool being of simple, strong and sturdy construction, and easy to assemble, disassemble and maintain in proper operating condition.

A further object of the invention is to provide a gas pressure operated apparatus for use in a well bore in which the gaseous force is exerted upon a piston structure disposed within a confining cylinder, and in. which an im- ₆₅ body 10. proved by-pass around the piston is provided to release &lt;· the gas under pressure into the surrounding well bore after the apparatus has performed its desired function in the well bore.

This invention possesses many other advantages, and has other objects which may be made more clearly apparent from a consideration of a form in which it may be embodied. This form is shown in the drawings accompanying and forming part of the present specification. χ„ ---------It will now be described in detail, for the purpose of 24 holding the upper expander to the body 10. these illustrating the general principles of the invention, but it is to be understood that such detailed description is not to be taken in a limiting sense, since the scope of the invention is best defined by the appended claims.

Referring to the drawings: .

Figures 1, la and lb together constitute a longitudinal section through well apparatus positioned in a well cas45

2,799,343 ³ gagement with the casing wall. A subsequent upward strain or pull on the packer body shears the screws 24 holding the upper expander to the body 10 and moves the lower expander 18 and slips 14 with the body toward the upper expander 20 and slips 23, to effect compression 5 of the packing 19 between the expanders and its outward expansion into firm sealing engagement with the wall of the casing.

Thereafter, an increase in the upward pull or force on the packer body 10 substantially simultaneously shears 10 the screws 25, 27 holding the lower expander 18 to the body and the lower slips 14 to the lower expander, to cause the lower flange 15 and guide 13 on the body to shift the lower slips 14 upwardly along the lower expander and radially outward into anchoring engagement 15 with the wall of the casing B. A split retractor ring 28 may be disposed in the expander 20 for engagement with one of several buttress thread ratchet teeth 29 formed on the exterior of the body 18 to lock the latter against downward movement. The packer is now anchored in 20 packed-off condition within the well casing, as disclosed in Fig. lb.

As shown in the drawings, setting of the well packer A. is dependent upon the development of a gas pressure within the setting tool C releasably secured initially to 25 the well packer. This gas pressure is developed within the upper portion of a cylinder 3®, consisting of a generally cylindrical upper sleeve 31, an upper head 32 threaded into this sleeve and also an intermediate head 33 threaded into this sleeve. A lower cylinder sleeve 34 30 is threadedly secured on the intermediate head 33 and is, in turn, threaded onto a lower cylinder head 35.

The upper head 32, upper sleeve 31 and intermediate head 33 form an upper cylinder portion 30α, whereas the intermediate head 33, lower cylinder sleeve 34 and 35 lower head 35 form a lower cylinder portion 306. These two cylinder portions 30α, 306 are separated by the intermediate head 33, but are communicable with each other through a central passage 36 formed through the intermediate head. Leakage from the cylinder through 40 the several threaded connections may be prevented by suitable side seals 37 in the heads 32, 33, 35 engaging the inner walls of the cylinder sleeves 31, 34.

A motivating gas under pressure is provided in the upper cylinder portion 30α, and the force of this gas is 45 transmitted through a suitable liquid medium 38 to the lower cylinder portion 306 through the intermediate head passage 36 for operation upon a piston 39 slidably mounted in the lower cylinder portion. This piston 39 has one or more ring grooves 4® in its periphery for the 50 accommodation of seal rings 41 to prevent leakage in both directions between the piston 39 and lower cylinder sleeve 31.

The upper end of a piston rod 42 is threadedly connected to the piston 39, the rod extending downwardly 55 through the lower cylinder head 35 to a point therebelow. An anvil or cross-piece 43 is mounted within a transverse slot 44 in the rod. Leakage between the rod 42 and lower cylinder head 35 is prevented by suitable rod packing 45 disposed within suitable ring grooves 46 60 in the head 36, to prevent leakage of liquids from the well casing into the cylinder 396 below the piston 39, insuring that air under atmospheric pressure is present below the piston when the apparatus is assembled and lowered in the well casing B. 65

It is desired to transfer the downward movement of, or force imposed upon, the piston 39 and the piston rod 42 to the upper slips 23 of the packer body 10, to secure the desired anchoring of the packer in the well casing. To accomplish this purpose, a tubular actuat- 70 ing mandrel 47 is threadedly connected to the lower end of the lower cylinder head 35. The lower end of the mandrel 47 is secured, through the agency of the frangible connecting pins 48, to a sleeve 49 threaded to the upper end of the body 10. As specifically disclosed, the 75 lower end of the mandrel 47 is of reduced diameter and is piloted within the sleeve 49, the pin 48 extending transversely through the sleeve and pilot mandrel portion.

The piston rod 42 is movable downwardly within the bore 50 of the actuating mandrel 47, the cross-piece 43 projecting in opposite directions from the rod through diametrically opposed longitudinally extending slots 51 formed through the mandrel wall. The cross-piece also extends through opposed slots 52 formed through a setting ring or sleeve 53 slidably mounted on the actuating mandrel 47 to form a connection between the piston rod 42 and the cross-piece 43. A setting sleeve or skirt 54 is adjustably threaded on the setting ring 53, its lower end engaging the top of the upper slips 23.

As indicated above, a force or pressure is imposed on the liquid 38, such as oil or water, resting on top of the piston 39. This force moves the piston 39 and piston rod 42 downwardly and the cylinder 30 in a relatively upward direction. The downward movement of the rod 42 is transmitted to the setting sleeve or skirt 54 through the anvil 43 and setting ring 53, whereas the upward movement of the cylinder 30 is transmitted to the packer body 10 through the actuating mandrel 47, frangible pin 48 and sleeve 49. Accordingly, it is apparent that the development of sufficient pressure in the cylinder 30 acting upon the piston 39 will eventually shear the screws 26 holding the upper slips 23 to the expander 20 and move the slips outwardly against the casing B. Thereafter, the cylinder 30 will move upwardly to pull the body 10 in the same direction for the purpose of expanding the packing sleeve 19 against the casing B and the lower slips 14 against the casing, in the manner described above.

To secure the desired operational sequence, gas under pressure is provided within the upper end of the cylinder 30. Such gas under pressure may be generated in the upper end of the cylinder, as by burning a combustible charge 60 in the cylinder. As specifically illustrated and described in Patent 2,618,343, the charge is ignited by a blank cartridge 61 contained within a gun barrel 63 inserted within the upper end of the upper cylinder head 32. Leakage between the barrel and the cylinder head is prevented by a suitable side seal 64 in the barrel engaging the wall of the head 32. This barrel 63 is threaded into a firing head 65 which, in turn, is threadedly secured to the upper end of the cylinder head 32. The wire line running-in string D is suitably secured to the firing head, in a known manner, and has the lower end of its electrically conductive wire or core 66 connected electrically to a heating filament 67 contained within the cartridge 6.

_ When the combustible fuel or power charge 60 is ignited, evolved gas under pressure is produced within the upper end the upper cylinder portion 30α, or some other form of gas under pressure may be provided therein. This gaseous force acts downwardly upon an upper or floating piston structure 70 disposed initially adjacent the upper cylinder head 32. The piston portion 71 cf this structure carries one or more suitable seal rings 72 in one or more peripheral grooves 73 that are engageable with the wall of the upper cylinder sleeve 31 to prevent leakage around the exterior of the piston in both directions.

Originally, as disclosed in Patent 2,618,343, the piston structure 70 rests upon the fluid medium 38, which substantially entirely fills the cylinder space between the upper piston structure and the lower piston 39, including the volume of the passage 36 through the intermediate head. This fluid medium is predominantly and almost entirely a liquid, such as water or oil. For the puipose of delaying a transfer of the liquid medium 38 from the upper cylinder portion 30α into the lower cylinder portion 306 as the floating piston structure 70 is forced downwardly by the gaseous pressure in the upper portion of the cylinder 30α, a flow restricting device 74, such as

2^0,343 an upward direction to shift the latter radially outward into engagement with the casing B. _ ,

The pressure in the cylinder 30 continues to increase as combustion of the charge proceeds, and all of the packer elements are engaged more firmly with the casing B (as disclosed in Fig. lb). When the pressure exceeds the shear strength of the connecting pin 48 securing the lower end of the actuating mandrel 47 to the sleeve 49, this pin is sheared to release automatically the setting tool C from the well packer A. All of the mechanism, with the exception of the packer A can now be removed from the well casing B.

The orifice 74 retards the downward movement ot the floating piston structure 70 in the cylinder as the gas pressure increases and as the sequence of operation on the well packer takes place, so that no sudden movements can occur, particularly the sudden descent of the piston structures 70, 39 relatively within the cylinder 30 following disruption of the shearable connector pin 48.

When this occurs, the upper piston structure 70 can only move downwardly at a relatively slow rate (which may consume several seconds) until the piston structure 70 engages the intermediate cylinder head 33. The lower piston 39 will only move downwardly to the extent 25 determined by the volume of liquid 38 thereabove that has been forced through the orifice 74 into the lower cylinder portion 30b. Accordingly, the parts of the apparatus will come to rest without any sudden shock blows being struck against portions of the cylinder 30, on which might damage the apparatus. However, the upper cylinder 30α above the piston structure 70 will still contain gas under relatively high pressure (which may be as high as 7500 p. s. i.) which pressure could remain trapped within the cylinder until the setting tool C is withdrawn from the well bore to the top of the hole. Extreme care must be exercised in releasing this gas pressure at the top of the hole, during disassembly of the setting tool, to obviate a dangerous condition and to prevent injury to persons and damage to property.

Following the disruption of the shear pin 48 connecting the setting tool C to the well packer A, which actually completes the operation in the well bore with the specific apparatus illustrated, it is desired to automatically vent or bleed the pressure within the upper cylinder 30α into the surrounding well bore. It is also a desirable feature to bleed the liquid 38, or relieve the pressure in the liquid, disposed in the cylinder 30 into the surrounding well bore, so that the removal of the setting tool C to the top of the hole can occur with assurance that there is substantially no fluid pressure within the cylinder 30.

As disclosed, the upper piston structure 70 is of a composite character. It includes a central piston portion 76 from which a stem or rod 77 depends to a sub55 stantial extent. The periphery of the central portion 76 is disposed a substantial distance inwardly from the wall of the upper cylinder. The piston construction includes the outer piston portion or shell 71 which slidably seals against the wall of the upper cylinder, as heretofore described. The inner surface 78 of the hollow piston shell 71 is adapted to seal against the upper peripheral portion 79 of the piston rod 77 when the piston shell is disposed in its uppermost position substantially abutting the central piston portion 76. Thus, the piston shell is adapted to seal against a suitable seal ring 80, such as a rubber O ring, contained within a peripheral groove 81 in the piston stem.

The piston shell 71 has an upwardly extending skirt 82 encompassing the central piston portion 76 and slidable along the cylinder wall. This skirt is preferably spaced outwardly from the periphery of the central portion 76 to allow the gas pressure in the upper cylinder 30α above the piston structure 70 to be exerted between the opposed faces 76α, 71α of the central piston portion 75 and the piston shell. To assure that fluid under pres&amp; bean or orifice, is threaded into the lower end of the passage 36 through the intermediate head 33. The cross-sectional area of the hole 75 through the bean or orifice 74 is much less than the area of the passage 36 itself, the orifice area being so chosen as to allow fluid to flow from the upper cylinder 30α into the lower cylinder portion 30Z&gt; for action upon the lower piston at a slow or retarded rate, for a purpose to be explained below. , .,

The apparatus is lowered in the well bore with tne slips and packing elements of the well packer disposed in their initial retracted position, with the lower piston 39 adjacent the lower end of the intermediate cylinder head 33 and with the floating piston structure 70 in its upper position adjacent the upper cylinder head. The oil or water 38 substantially completely fills the cylinder between the upper piston structure 70 and the lower piston 39. , . , ,. , .,

When the depth in the casing is reached at which the well packer A is to be set, the electric circuit through the cartridge filament 67 is completed to fire the cartridge 61. The flame issuing therefrom ignites the upper end of the combustible charge 60 resting upon the upper piston structure 70, initiating its combustion. This charge contains its own source of oxygen to support combustion. As combustion proceeds, a gaseous pressure is developed within the upper portion of the cylinder 30α above the floating piston structure 70. As the pressure increases the floating piston structure is urged downwardly and the cylinder 30 relatively upwardly. The force imposed on the floating piston structure 70 is transmitted through the fluid medium 38 to the lower piston 39, and from this piston through the rod 42, cross-piece 43 and setting sleeve 53 to the sleeve 54, which bears against the upper slips 23. Downward movement-of the lower 35 piston 39 takes place against the relatively slight resistance of the air in the lower cylinder portion 30α below the piston 39, which is initially at atmospheric pressure, and also against the hydrostatic head of fluid in the well casing acting upwardly across the cross-sectional area of the 40 piston rod 42. When sufficient pressure has been developed within the upper cylinder portion 30α by the gaseous medium and has been transmitted through the piston structure 70, fluid medium 38, lower piston 39, piston rod 42, cross-piece 43, setting ring 53, and sleeve 45 54 to the slips 23, to overcome the shear strength of the shear screw 26, and also the hydrostatic head of fluid acting upwardly on the piston 42, the slips 23 are released from the expander 20 and are pushed downwardly along the latter into outward engagement with the casing B.

As the combustible charge 60 continues to burn, the gas pressure within the upper cylinder portion 30α progressively increases to a further extent, and the increased pressure and force is transmitted to the lower piston 39 through the intervening fluid medium 38. Since the upper slips 23 are wedged against the casing B, the piston 39 cannot move downwardly to an further appreciable extent. Instead, the cylinder 30, actuating mandrel 47, sleeve 49 and packer body 10 are urged in an upward direction. When the pressure and force within the cylinder 30 is increased sufficiently to overcome the shear strength of the screws 24 holding the the upper expander 20 to the body, such screws are disrupted and the packer body is then moved upwardly within the upper expander 20 to compress the rubber packing sleeve 19 between the upper and lower expanders 20, 18, forcing the packing sleeve into firm sealing engagement with casing wall.

Further increase in the cylinder gas pressure, as a result of the continued combustion of the charge 60, effects shearing of the screws 25, 27 attaching the lower expander 18 to the body 10, and the lower slips 14 to the lower expander, allowing the cylinder 30 to move upwardly and carry the body 10 and lower slips 14 in

2,799,343 sure can be exerted on the upwardly facing surface 71α of the piston shell, the central piston portion 76 may be provided with a plurality of longitudinal passages 83 extending from its upper surface to its downwardly facing surface 76α. 5

As described hereinbelow, when the piston shell 71 is moved downwardly along the piston stem or rod 77, its inwardly projecting surface 78 will ride off the upper sealing portion 79 of the stem or rod and come to rest in a position therebelow. At this time, a by-pass passage 10 84 will be opened through the piston structure 70, the fluid in the cylinder 30α above the piston structure 70 being capable of passing around the periphery of the central piston 76, and between the central portion and the upper end of the piston shell 71, thence between the 15 periphery of the stem 77 and the interior of the piston shell 71 to a location below the piston structure 70. The piston shell 71, in effect, is a valve member adapted to be disposed in an upper position in sealing engagement with the piston rod seal ring 80 to close the by-pass 84. ²⁰When moved downwardly, as has just been described, the by-pass is opened.

The piston rod 77 depends to a substantial extent below the piston shell 71, being adapted to operate upon an internal sleeve valve 85 located within the intermediate ²⁵head passage 36, for the purpose of shifting the sleeve valve downwardly to an open position. Initially, this sleeve valve 85 is disposed across one or more relief or bleeder ports 86 extending through the intermediate cylinder head 33 between its passage 36 and the exterior ³θ thereof. The sleeve 85 has a central passage 87 therethrough surrounded by an upwardly facing tapered valve seating surface 88. When the valve 85 is disposed across the bleeder ports 86, leakage between the wall of the passage 36 and the periphery of the sleeve is prevented ³⁵by one or .more side seals 89 disposed in peripheral grooves 90 in the sleeve and sealingly engaging the wall of the passage 36 on opposite sides of the bleeder ports 86.. The sleeve valve 85 is releasably retained in this initial position by a latch device, which may take the ⁴⁰form of a split, expansible latch ring or snap ring 91 located within, a peripheral groove 92 in the sleeve and normally tending to be disposed outwardly into an internal groove 93 in the intermediate cylinder head. Both the latch ring 91 and the internal groove 93 have opposed ⁴⁵tapered side walls 94, 95 that converge toward each other in a lateral outward direction to facilitate inward retraction of the latch ring 91 when the sleeve valve member 85 is to be shifted downwardly within the intermediate head passage 36. 50

In the use of the apparatus, the upper piston structure 70 moves downwardly as a unit as the gas pressure increases in the upper cylinder 30α thereabove, forcing the liquid 38 down through the intermediate head passage 36,. the orifice 74 at its lower end, and into the lower °'^Jcylinder 30δ for action upon the lower piston 39, to secure the full setting of the well packer A in the well bore. When the release or shear pin 48 is disrupted, the apparatus is relieved of load, which then allows the upper piston structure 70 to move downwardly to a further extent, the. lower end 96 of the rod or stem entering the intermediate head passage 36 and coming to rest on the valve seat surface. 88 of the sleeve valve 85. During all of this time, the piston shell 71 remains in its uppermost ..position against the central piston portion 76, so that the gas under pressure above the upper piston structure 70 cannot by-pass around it. As the piston structure 70 moves downwardly after engaging the valve sleeve 85, it effects an inward retraction and release of the snap ring 91 from the intermediate head groove 93, pushing the ' sleeve valve 85 downwardly to its fullest position below the relief or bleeder ports 85, opening the latter and establishing communication between the intermediate head passage 36 and the surrounding well bore. 75

When the inner sleeve valve engages the intermediate head at the lower end of the passage 36, the sleeve valve 85 and the piston rod 77 cannot move downwardly to any further extent. However, the gas under pressure is still acting on the piston shell 71, which at that time is still disposed above the upper end of the intermediate head 33. This gas under pressure then shifts the piston shell 71 downwardly relative to the central piston portion 76 and the rod 77, to shift its inwardly directed valve portion 78 off the seal ring 80 on the rod and into a position in which the by-pass 84 through the shell 71 is opened, such as disclosed in Fig. 3. With the parts in this position, the gas under pressure can then pass from the upper cylinder 30α above the piston structure 70, between the piston shell 71 and the central piston portion 76 and the rod 77 into the intermediate head passage 36, making its exit through the relief ports 86 into the well bore. Following the venting of the gas, the liquid 38 under pressure in the lower cylinder 30&amp; can then exert a force in an upward direction to lift the stem 77 off the valve seat 88, which will then allow the liquid to pass through the sleeve valve 85 and out through the relief ports 86 to the exterior of the apparatus.

It is preferred that the lower end 96 of the piston rod 77 make a seal witn the valve seat 88 in the inner sleeve valve 85, so that as a result of the initial engagement of these parts, no further liquid below the upper piston structure 70 can be forced down through the sleeve valve 85 and into the lower cylinder 30έ. In effect, the liquid will tend to be trapped between the upper end of the sleeve valve 85, when the latter is disposed in its closed position, and the lower portion of the piston shell 71. Accordingly, the full force of the gas under pressure acting downwardly on the upper piston structure 70 is available to shift the sleeve valve 85 downwardly, which will insure the retraction of the snap ring 91 completely within the sleeve valve groove 92, and assure the downward sliding of the sleeve valve to its lowermost position, in which the relief ports 86 are open. If, for some reason, the stem or rod 77 does not move downwardly following its engagement with the sleeve valve 85, then the piston shell 71 will move downwardly along the rod 77 to exert the pressure on the liquid therebelow and cause the liquid under pressure to act downwardly on the sleeve valve 85 and effect the retraction of the snap ring 91 and the downward shifting of the sleeve valve 85 to the bleeder port opening position. As a matter of fact, the sleeve valve 85 need not move downwardly slowly Upon release of the latch ring 91, it can, in effect, be impelled to its downward position, remaining in such downward position because of the friction of the seal rings 89 and of the snap ring 91 against the wall of the passage 36.

With the apparatus disposed in the fluid in the well bore, the fluid pressure will diminish to the extent corresponding to the hydrostatic head of fluid in the well bore. As the setting tool C is raised through the fluid m the well bore, and the hydrostatic head acting thereupon progressively decreases, the pressure within the apparatus will also be correspondingly decreased until it is substantially zero when the apparatus is removed from the. wefl at its top portion. The apparatus can then be dismantled, with assurance that there is no substantial pressure within the equipment that could injure persons or impose damage to property.