US3812911A

US3812911A - Retrievable blanking plug

Info

Publication number: US3812911A
Application number: US00368717A
Authority: US
Inventors: R Vann
Original assignee: Individual
Current assignee: Halliburton Co; GEO INTERNATIONAL CORP
Priority date: 1973-06-11
Filing date: 1973-06-11
Publication date: 1974-05-28
Anticipated expiration: 1991-05-28

Abstract

Combination wireline fishing tool and retrievable blanking plug for use in conjunction with a seating nipple. The blanking plug has a fishing neck which extends from a shoulder located thereon. The fishing neck includes spaced overshot engaging members so that a fishing tool in the form of an overshot can be forced into engagement with either of the members. An axial counterbore extending into the blanking plug has a combination stop means and pressure relief means located therein, in the form of spaced breakable plugs. The counterbore further includes means for releasing the blanking plug from the seating nipple. Attached to the overshot in axially aligned relationship therewith is a probe arranged whereby part of the overshot must be positioned in attached relationship between the two spaced members in order for the probe to break a relief plug and equalize the pressure across the blanking plug. Part of the overshot must next be moved into a position between the shoulder and the lowermost overshot engaging member and the second breakable plug broken by the probe in order for the release device to be actuated.

Description

nited States Patent Vann May 28, 1974 RETRIEVABLE BLANKING PLUG [57] ABSTRACT [76] n entor Roy R- van, PO. BOX 38, Artesia, Combination wireline fishing tool and retrievable N. Mex. 88210 blanking plug for use in conjunction with a seating nipple. The blanking plug has a fishing neck which ex- [22] plied June 1973 tends from a shoulder located thereon. The fishing [2l] Appl. No.: 368,717 neck includes spaced overshot engaging members so that a fishing tool in the form of an overshot can be 52 us. (:1. 166/135, 166/192 engagement members" [51] Int. Cl E2lb 23/00 An axial ee e extending to the blanking p g [58] Field of Search 166/119, 135, 114, 203, a a m ina t p means and pr ssur r li l66/l92 194, 125 means located therein, in the form of spaced breakable plugs. The counterbore further includes [56] References Cited means for releasing the blanking plug from the seating UNITED STATES PATENTS nipple. Attached to the overshot in axially aligned relationship therewith is a probe arranged whereby 3 2:2? part of the overshot must be positioned in attached 2 905 246 9/1959 Rodger s i... :IIIIIIII: 166 114 x relationship between the two Spaced members Order 3:020:958 2/1962 Kenneday l66/l 18 for the probe to break a relief P and equalize the 3,055,429 9/1962 Tausch 1 1 192 X pressure across the blanking plug. Part of the overshot 3,250,331 5/1966 Boyle 166/135 X must next be moved into a position between the 3,633,668 l/l972 Vazquez et al. 166/135 shoulder and the lowermost overshot engaging member and the second breakable plug broken by the Przmary Examiner-David H. Brown probe in order for the release device to be actuated. Attorney, Agent, or FirmMarcus L. Bates 10 Claims, 9 Drawing Figures WIB 62 I l l. l 61 34 ll 1 28 35 l 33 l 1 a? s5 36 l l i l l 64 PATENTEWYZBIW 3812.911

SHE] 2 if 4 Ti FIG. 5

PATENIEI] m 28 m4 sum 3 or 4 FIG. 5

r I l. 'RETRIEVABLE BLANKING PLUG BACKGROUND OF THE INVENTION Seating nipples for accommodating retrievable blanking plugs take on many different forms and configurations and may be used in a variety of locations so as to attain any number of different desirable goals. For example, seating nipples often are associated with casing packers so that part of a production string can be located downhole in the borehole by attachment to the packer. A blanking plug is then placed within the sealing nipple, and the upper part of the production tubing removed from an on/off sealing connection positioned above the packer assembly in order to enable that portion of the borehole located above the packer to be subjected to various operations, such as described in my U.S. Pat. No. 3,706,344 issued Dec. 19, I972. At other times, the seating nipple may be placed elsewhere within a tubing string in order to isolate one portion of the production string from another.

When the seating nipple is used in conjunction with a tubing string leading to a high pressure gas formation, great care must be exercised in removing the retrievable plug from its seating nipple because several thousand pounds upthrust will propel the plug in a manner similar to a projectile should the plug be released from its nipple prior to equalizing the pressure thereacross. Should the plug be actuated by a wireline fishing tool, the plug, upon being thrust uphole, will become entangled in several thousand. feet of wireline or slickline, thereby bringing about a very difficult fishing job.

It is possible to equalize the pressure across the packer by the utilization if inert gas pumped into the tubing string. Others have proposed. a single breakable equalizing plug located within the bridge plug which can be broken by a wireline actuated tool so as to communicate the upper and lower separated lengths of the tubing string; however, when this last expedient is employed, it is still possible for upthrust of the fishing tool to occur. Furthermore, assuming the last expedient is successfully carried out,-two costly round trips must be made into the borehole in order to retrieve the blanking plug. Accordingly, it is desirable to have a combination fishing tool and retrievable bridge plug which can be used in conjunction with the seating nipple and which overcomes all of the above drawbacks, while at the same time taking advantage of the benefits of the prior art.

SUMMARY OF THE INVENTION This invention comprehends a combination retrievable blanking plug and fishing tool which enables wire line retrieval of the plug from a seating nipple when the plug is used to isolate or plug off a portion of the interior of a high pressure tubing string.

The fishing tool preferably is in the form of an improved overshot having a cylindrical skirt and an axially aligned longitudinally extending probe of different diameters. The blanking plug is comprised of a main body having a shoulder from which there upwardly depends a fishing neck having a lifting means in the form of an overshot engaging member so that the overshot can engage the member. The probe is receive through a counterbore which forms an axial passageway extending through the fishing neck and through most of the main body of the plug.

Located within the axial passageway are spaced stop means in the fonnof breakable relief plugs. A release means for actuatinga set of dogs is disposed above the breakable plugs and include an actuating means located within the axial passageway by which the dogs may be released from the seating nipple.

The probe has a small inside diameter (id) surface which freely passes the actuating means of the dogs, and engages and breaks one plug when the overshot is captured by the overshot engaging member. A large outside diameter (od) portion of the probe engages the release means of the dog when the overshot is lowered into further engagement with the lifting means, and after the second breakable plug has been ruptured.

This expeident enables the fishing tool to be latched .onto the fishing neck at all times while removing the blanking or bridge plug, and further enables the pres sure differential across the blanking plug to be safely equalized before the blanking plug is released from the seating nipple. Y

Accordingly, a primary object of the present invention is the provision of an improved combination of elements which enables a blanking plug to be removed from a seating nipple in an improved and safe manner, and in a single trip into the borehole.

Another object of the invention is to provide improvements in wireline actuated blanking plugs which enables the pressure across the plug to be equalized before the plug is released from its seating nipple.

A further object of this invention is to provide both method and apparatus for use in downhole flow restricting apparatus which enables a blanking plug to be removed from the hole by a wireline operated fishing tool in a safe and heretofore unavailable manner.

A still further object of this invention is to provide an improved combination retrievable packer and fishing tool which enables the packer to be positioned downhole in a borehole and then retrieved in a single trip by the novel wireline actuated fishing tool by latching the tool and packer together, relieving the pressure across the packer apparatus, releasing the packer apparatus from the borehole, and then pulling the entire assembly to the surface of the earth by the wireline.

Another object of the invention is the provision of a method of retrieving a blanking plug from a seating nipple in a single trip by a wireline operated fishing tool.

These and various other objects and advantages of the invention will become readily apparent to those skilled in the art upon reading the following detailed description and claims and by referring to the accompanying drawings.

The above objects are attained in accordance with the present invention by the provision of apparatus fabricated in a manner substantially as described in the above abstract and summary.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a part diagrammatical, part schematical representation of a cross-sectional view of a borehole formed within the earth, with apparatus made in conjunction with the present invention being disclosed therewithin, with some parts being-broken away and the remaining parts being shown in cross-sections so as to best disclose one operative form of the invention;

FIG. 2 is an enlarged, fragmentary, part crosssectional, side elevational view of part of the apparatus disclosed in FIG. 1;

FIG. 3 is an enlarged, fragmentary, part crosssectional, side elevational view of part of the apparatus disclosed in the foregoing figures;

FIG, 4 is a further enlarged cross-sectional view taken along line 4-4 of FIG. 3;

FIG. 5 is a part cross-sectional, enlarged, sideelevational view of a fishing tool used in'conjunction with the apparatus of FIGS. 3 and 4;

FIG. 6 is an enlarged, fragmentary, part crosssectional view of part of the apparatus disclosed in FIG. 5;

FIGS. 7 and 8 are part cross-sectional illustrations of the operation of part of the apparatusdisclosed in the foregoing figures; and

FIG. 9 is a broken, part-cross-sectional view'of a modification of FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS I FlG. l discloses a well head 10 located at the top of a borehole formed within the ground II, with the borehole being cased at 12 so as to provide access to a production formation 13 located downhole in the borehole. Production tubing 14 provides for flow of hydrocarbons at 15, while a lubricator l6 admits wireline 17 into the production tubing in sealed relationship therewith, as is known to those skilled inthe art.

The wireline is supportingly attached to a fishing tool I8, which for the purposes of illustration of this invention'is disclosed as being in the form of an improved and novel overshot.

Annulus 19 has a conventional packer assembly, schematically illustrated by numeral 20, located therein which maytake on any number of different forms, as for example a Baker retrievable casing packer product number 646-12, described on page 498 of Baker Oil Tool l970-7l catalog, 7400 East Slauson Avenue, Los Angeles, California. Located in close proximity of the packer is a seating nipple 21 of conventional design, such as product number 801-50 seen on page507 of the before mentioned catalog. The seating nipple screws into the top of the packer, although it can be placed anywhere in the production tubing string desired. Underlying the packer is a perforated nipple 22 having perforations 23 therein.

The nipple is flow connected to a sub 24 and affixed to the packer for supporting a perforating gun 25 such as described in U.S. Pat. No. 3,650,640 so that the easing can be perforated as indicated by number 26, thereby communicating the interior of the production string with the hydrocarbon bearing formation.

A retrievable blanking plug 27, having a fishing neck 28, has been placed within the seating nipple and it is accordingly necessary to be able to remotely remove the plug from the nipple in order to gain access to the lower portion of the borehole through packer 20. Sub 29 is an on/off sealing connector such as seen on page 499 of the above mentioned catalog, which enables the upper tubing string to be removed from the packer assembly should free access to the upper portion of the borehole be required.

The perforated nipple is provided with a sliding sleeve 30 having ports therein which enables the apertures 23 to be aligned therewith or opened or closed to 4 flow therethrough according to the position of the sleeve 30.

As best seen illustrated in FIG. 5, together with certain other figures of the drawings, the before mentioned fishing tool is disclosed in its simplest and preferred form as an overshot having a swivel 31 connected to a reinforced head portion 32 from which there downwardly depends a downwardly opening skirt member 33'. The skirt member is formed of a plurality of lands 34 which are formed by the vertical cutouts 35, thereby forming elongated resilient members which can be outwardly biased from one another. The lowermost circumferentially disposed terminal edge portion 36 is upwardly turnedat innermost edge portion 37 for engagement with the underside of the spaced members located on the fishing neck.

Axially aligned in a concentric manner respective of the skirt and the wireline is a special elongated probe 38 having one end thereof rigidly affixed to member 32. The probe reduces in diameter at shoulder 39 to form reduced diameter portion 40 which terminates at the free terminal end 41.

The seating nipple can take on any number of different forms so long as the inside diameter 42 thereof admits the plug in sealed relationship thereinto and enables the formation ,of a lock means 43 which, for purposes of this disclosure, is shown in the form of a circumferentially extending concavity having an upwardly directed portion 44.

The main body of the plug is of a constant diameter 45 and has associated therewith seal means 46 which are made for sealingly engaging the inner wall surface of the seating nipple. Any number of design variations are possible respective to the seal means.

The body includes radially disposed passageways aligned normally to the axial passageway, and within which there is threadedly affixed spaced

breakable plugs

47 and 48. The plugs have axially aligned counterbores 49 formed therewithin, and a free end portion 50 extending into the lower portion of axial counterbore SI. The counterbore forms an axial passageway of limited length, with the passageway terminating as indicated by the arrow at numeral 52. The bottom of the main body of the retrievable plug is indicated by the numeral 53, while the opposed end of the main body terminates in the form of a circumferentially disposed horizontal alined annular shoulder 54.

Anchor means in the form of dogs 55,. 56 are pivotally mounted in journaled relationship to the main body by diametrically opposed pins positioned at 57, so that each of the radially spaced dogs are articulated within the illustrated body cavity.

Opposed cavity walls

58 and 59 form a stop means against which the dogs may be abuttingly received. Each dog has an external free end portion which engages the wall surface of groove 43 and further includes a free inner end portion 60 which forms a release means located within the axial passageway for causing the dogs to be moved into a retracted position against wall 58.

The first or uppermost fishing neck member 61 has a contoured upper surface over which the overshot skirt is guided and a concave lower surface 62 against which the inside rim of the skirt of the overshot can be attached in order to lift the plug in an upward direction. Passageway 51 extends from end wall 52 through most of the main body and'continues through the fishing neck to where the passageway is outwardly flared at 63 for guidably receiving the free end of the probe therewithin.

The second or lower member 64 is made substantially identical to member 61 with the second member being spaced from the first member and from the shoulder 54 so as to provide lost motion of the overshot along the longitudinal portions or

areas

65 and 66.

In the illustration of FIG. 7, the overshot has been lowered so that the skirt member has been forced to receive the upper lifting member therewithin. It will be noted that the rim 37 of the skirt is captured between the upper and lower members along the area 65. It will be further noted that end portion 41 of the reduced diameter portion of the probe has ruptured the free end portion of the upper stop and relief plug 47, and is spaced from stop and relief plug 48 with shoulder 39 of the-probe being spaced from the release means 60 of the extended dogs. When the overshot is further lowered, the rim or lifting element of the skirt will be brought into close proximity of the upper face of the lower lifting member, with end 41 of the probe resting against the lower stop member 48.

In FIG. 8 it will be noted that the overshot has been forced to receive the lower member therewithin, thereby forcing the probe to rupture the lower stop and relief member 48, with the rim of the skirt being captured between the lifting edge of the lower lifting member and the shoulder 54, and with end portion 41 of the probe being slightly spaced from bottom wall 52. The large outside diameter portion 38 of the probe is in engagement with the release means at 60 which has caused the dogs to be moved from the illustrated dotted extended position into the illustrated retracted position.

In the embodiment of FIG. 9, overshot 133 has a plurality of lands 134, each of which are provided with a plurality

ofupturned edge portions

136, 136, 136" for single or plural engagement with one or two lifting

members

61, 64.

OPERATION In operation, with the blanking plug being used in conjunction with the apparatus disclosed in FIG. 1, the plug has already been run to setting depth and positioned within the seating nipple so as to isolate the upper and lower portions of the production string from one another, and to enable the upper tubing string to be removed at the on/off sealing connector thereby enabling one to accomplish various desirable operations on the well. The presence of the plug prevents debris from falling into the lower production string below the packer as well as placing the formation in a shut-in condition. When the upper tubing string has been replaced and it is desired to remove the plug from the seating nipple, it must be remembered that there is often several thousand pounds of pressure differential across the plug, and accordingly, should this pressure fail to be equalized, the plug, when released will be accelerated uphole in the manner of a projectile, thereby entangling the wireline, the overshot. and the plug, which brings about a very expensive and complicated fishing job.

Preferably, a mechanical jar 70 and sinker bar is affixed to the upper member of the overshot by means of sub 71 so that ajarring action can be imparted in either direction into the overshot as may be required. The tool string of FIG. 1 is run downhole on the wireline,

and as the free end of the probe enters the entrance passageway to the fishing neck, the rim of the overshot will come to rest upon the upper face of member 61. This position gives the wireline operator an indication that the upper member 61 is ready to be received within the overshot. The overshot is next moved down so that it assumes the illustrated position as seen indicated in FIG. 3. Further lowering of the overshot brings reduced diameter portion 40 into engagement with the combination stop and relief means in the form of upper breakable plug 47,'with the reduced diameter portion of the probe being freely received within the free area formed between the spaced release means in the illustrated manner of FIG. 4. The latch formed by the rim or lower skirt portion of the fishing tool can now be reciprocated along length 65 of the fishing neck, thereby enabling plug 47 to be broken or sheared. As impact causes plug 47 to become broken, the free end 41 of the probe-moves into engagement with the lower plug, with shoulder 39 of the probe being spaced above the release means, while the overshot latch means rests above lower member 64. If care has been exercised in carrying out this last step, free end portion 41 of the probe will come to rest upon unsheared plug 48 prior to shoulder 39 engaging the release means of the dog. This action enables the pressure across the retrievable plug to be equalized as gaseous flow occurs along the annulus formed between the outer peripheral surface area of the main body of the retrievable plug and the inside peripheral wall surface of the seating nipple, through the passageway formed within plug 47 which now intercommunicates passageway 51 with the .plug annulus, and from passageway 51 out of the bugle 63 where flow continues to the well head.

After the pressure has been safely equalized, with the overshot latched onto the neck, the overshot is jarred down again until the lower plug is ruptured, thereby bringing the apparatus into the illustrated position of FIG. 8 where the overshot can now reciprocate along portion 66 of the fishing neck, all as set forth in the illustrated manner of FIG. 8. This expedient causes shoulder 39 of the probe to engage the release means at of the dogs, thereby retracting the dogs into the illustrated configuration seen in FIG. 8. Since the blanking plug is now released from the seating nipple, the wireline can be used to raise the blanking plug from the well bore, with the rim or latch means formed by the inwardly turned lifting edge 37 of the skirt engaging the concavity provided on the underside of the lower member of the neck. The bridge plug is removed from the lubricator of the well in the usual manner, and any subsequent operation can now be carried out on the well bore, as for example, perforation of the well bore casing, treatment of a lower formation, or placing the well back onto production, as may be required.

One of the essential teachings of the present invention lies in the proper

relative distance

65, 66 respective to the

relative distance

36, 39, 41 and 60, 47, 48, 52 of the overshot and plug. By making the relative ratios of these various distances an amount according to the teachings of this invention, the above novel practice can be carried out efficiently so as to safely remove a bridging plug or a retrievable blanking plug from a seating nipple or the like. Those skilled in the art, having reviewed this disclosure, will contemplate utilizing anchor means other than

dogs

55, 56 together with the concavity 43. Moreover, it is possible to use seal means 7 on the main body other than the embodiment disclosed at 46. The plug of instant invention can be provided with dogs which prevent upthrust, downthrust, or a combination of the two. The practice of the present invention enablesa retrievable plug means to be retrieved from a well bore in a single trip using a wireline actuated fishing and release tool. Heretofore, it has been necessary to make several trips into a borehole in order to equalize pressure and to remove blanking plugs from seating nipples, whereas now the plug can be safely removed in a single trip. The novel practice of latching the fishing tool onto the plug during all of the manipulative operations thereof further enhances the desirability of the retrieving operation. The unexpected advantages of time, labor, safety, and efficiency brought about by the new method and combination, along with the improved design of the plug and overshot have heretofore been unavailable in well bore operations using retrievable plugs of the type disclosed herein.

The use of either embodiment of the overshot disclosed in FIGS. and 8 in conjunction with the bridge plug of the present invention prevents upthrust of the plug upon equalization of the pressure thereacross; and upon release of the plug from its seating nipple, as well as enabling this sequence of operations to be carried out in a single trip into a borehole. The combination of two spaced relief and stop means in the tool provides a positive surface indication of the below ground action being carried out relative to retrieval of the plug.

The relief plugs should be made of a material which must be broken when impacted with several hundred pounds of force imparted by the jar, so as to provide a positive stop means which deliberately must be destroyed or broken for, the step-wise passage of the probe therethrough. The relief plugs should be breakable, not bendable, for the reason that a bent plug could cause malfunction of the tool combination, as will now be understood by those skilled in the art.

In using the overshot of HO. 9, only single lifting member 61 need be fabricated onto the fishing neck, although two lifting members are preferred for safety.

I claim: I 1. ln a well bore having a flow conduit located therewithin and a seating nipple located in the flow conduit so that a wireline operated fishing tool can retrieve a retrievable blanking plug from the seating nipple, in combination:

said plug having a main body portion for sealingly engaging the inside peripheral wall of the seating nipple, anchor means connected to said plug and being movable from an extended into a retracted position relative to said main body for engagement with the seating nipple; a fishingneck means formed on said plug, an axial passageway formed through said fishing neck means and into said main body; said fishing neck means having at least one lifting member which can be engaged by said fishing tool;

said fishing tool being in the form of an overshot having a downwardly depending skirt engageable with said lifting member and a probe axially aligned with said skirt and slidably received within said axial passageway; said probe having a large outside diameter portion affixed to said overshot and a small outside diameter free end portion;

release means located in said axial passageway movable by said large outside diameter portion of said probe for releasing said anchor means from the seating nipple; spaced upper and lower stop means,

" said upper stop means being a combination stop and pressure equalizing means, said spaced stop means being located in said passageway in underlying relationship respective to said release means in a position so that said upper stop and pressure equalizing means must be engaged by' said small outside diameter portion of said probe before said release means can be engaged by the large outside diameter portion of said probe;

the relative position of said lifting member, said release means, said spaced upper and lower stops, the length of said probe, and the relative position of said large and small outside diameter portion of said probe being arranged so that part of the overshot must be engaged with the lifting member in order for the probe to actuate the pressure equalizing means, andso that the probe must be positioned below the lowermost stop means in order for the large outside diameter of the probe to actuate the release means.

2. The combination of claim 1 wherein said lower stop means is a pressure equalizing means positioned to be actuated by said probe before the release means causes the'anchor means to be retracted.

3. The combination of claim 1 wherein said anchor means is a pivoted member journaled to said main body .and having opposed free ends, one free end being pivoted away from said body to provide for the anchor action while the remaining free end is pivoted into the passageway to provide for the engagement with the probe;

said small outside diameter of said probe passing free of said remaining free end of said pivoted member while said large outside diameter of said probe engages and moves said remaining free end of said pivoted member so that said one free end of said pivoted member can be retracted relative to said main body.

4. The combination of claim 1 wherein said skirt member has an expandable inwardly directed lower circumferentially extending edge portion; said lifting member is in the form of an enlargement about which said skirt member is received when the skirt member is moved in a downward direction, so that the inwardly directed edge portion of the skirt can be latched onto the enlargement, to thereby provide for a lifting action respective to said plug.

5. The combination of claim 1 wherein said lower spaced stop means is a pressure equalizing means, said upper and lower pressure equalizing means being positioned to be contacted and actuated by said probe before the release means is retracted;

said skirt member includes an expandable inwardly directed lower circumferentially extending edge portion; said fishing neck includes a second lifting member to provide for both an upper and a lower lifting member, said lifting members being enlargements about which said skirt member is received in latched relationship respective thereto when the skirt member is moved in a downward direction, so that the inwardly directed edge portion of the skirt can be latched onto both of the enlargements.

6. In combination, a retrievable blanking plug and a wireline operated fishing tool for use in a flow conduit located within a borehole;

said retrievable blanking plug having a main body,

means on said main body by which said plug can be placed in sealing engagement with the inside peripheral wall surface of the flow conduit; a lifting member connected to said main bodyfor engagement with said fishing tool;

anchor means including release means connected to said main body for releasably engaging the inside peripheral wall of the flow conduit so that the plug can be anchored therewithin; means forming an obstructed flow passageway through said main body; means on said fishing tool by which said obstructed flow passageway is made unobstructed when engaged by the last said means so that the pressure across the plug can be equalized when said fishing tool is placed in a first position of engagement with said lifting member;

means connected to said fishing tool for causing said anchor means to be disengaged from the flow conduit when said fishing tool is placed in a second position of engagement with said lifting member; whereby said fishing tool can be positioned in said first position of engagement relative to said plug to enable the pressure across the plug to be equalized, whereupon said fishing tool can then be placed in the second position of engagement with said lifting member so that the plug is released from engagement with respect to the conduit, thereby enabling the fishing tool to lift the plug from the flow conduit.

7. The improvement of claim 6 wherein said fishing tool is a wireline operated overshot having a skirt member located thereon;

said skirt member has an expandable inwardly directedlower circumferentially extending edge portion; said lifting member being an enlargement about which said skirt member is received when the skirt member is telescopingly moved in a downward direction thereover so that the inwardly directed edge portion of the skirt can be latched onto the enlargement thereby enabling the fishing tool to lift the plug from the conduit.

8. The improvement of claim 7 wherein said fishing tool has a probe thereon and said pressure equalizing means include a combination stop and pressure equalizing means positioned to be contacted by said probe before the release means is retracted.

9. The improvement of claim 7 wherein said skirt member has an expandable inwardly directed lower circumferentially extending edge portion; said lifting member includes upper and lower members in the form of enlargements about which said skirt member is received when the skirt member is moved in a downward direction, so that the inwardly directed edge portion of the skirt can be latched onto the enlargements.

10. The improvement of claim 7 wherein said fishing tool includes a probe for providing said releasing means; said pressure equalizing means include a stop means, and further including a lower stop means positioned to be contacted by said probe before the release means is retracted;

said lifting member includes an upper and lower enlargement about which said skirt member is received when the skirt member is moved in a downward direction, so that the inwardly directed edge portion of the skirt can be latched onto either of the enlargements.

Claims

1. In a well bore having a flow conduit located therewithin and a seating nipple located in the flow conduit so that a wireline operated fishing tool can retrieve a retrievable blanking plug from the seating nipple, in combination: said plug having a main body portion for sealingly engaging the inside peripheral wall of the seating nipple, anchor means connected to said plug and being movable from an extended into a retracted position relative to said main body for engagement with the seating nipple; a fishing neck means formed on said plug, an axial passageway formed through said fishing neck means and into said main body; said fishing neck means having at least one lifting member which can be engaged by said fishing tool; said fishing tool being in the form of an overshot having a downwardly depending skirt engageable with said lifting member and a probe axially aligned with said skirt and slidably received within said axial passageway; said probe having a large outside diameter portion affixed to said overshot and a small outside diameter free end portion; release means located in said axial passageway movable by said large outside diameter portion of said probe for releasing said anchor means from the seating nipple; spaced upper and lower stop means, said upper stop means being a combination stop and pressure equalizing means, said spaced stop means being located in said passageway in underlying relationship respective to said release means in a position so that said upper stop and pressure equalizing means must be engaged by said small outside diameter portion of said probe before said release means can be engaged by the large outside diameter portion of said probe; the relative position of said lifting member, said release means, said spaced upper and lower stops, the length of said probe, and the relative position of said large and small outside diameter portion of said probe being arranged so that part of the overshot must be engaged with the lifting member in order for the probe to actuate the pressure equalizing means, and so that the probe must be positioned below the lowermost stop means in order for the large outside diameter of the probe to actuate the release means.

2. The combination of claim 1 wherein said lower stop means is a pressure equalizing means positioned to be actuated by said probe before the release means causes the anchor means to be retracted.

3. The combination of claim 1 wherein said anchor means is a pivoted member journaled to said main body and having opposed free ends, one free end being pivoted away from said body to provide for the anchor action while the remaining free end is pivoted into the passageway to provide for the engagement with the probe; said small outside diameter of said probe passing free of said remaining free end of said pivoted member while said large outside diameter of said probe engages and moves said remaining free end of said pivoted member so that said one free end of said pivoted member can be retracted relative to said main body.

5. The combination of claim 1 wherein said lower spaced stop means is a pressure equalizing means, said upper and lower pressure equalizing means being positioned to be contacted and actuated by said probe before the release means is retracted; said skirt member includes an expandable inwardly directed lower circumferentially extending edge portion; said fishing neck includes a second lifting member to provide for both an upper And a lower lifting member, said lifting members being enlargements about which said skirt member is received in latched relationship respective thereto when the skirt member is moved in a downward direction, so that the inwardly directed edge portion of the skirt can be latched onto both of the enlargements.

6. In combination, a retrievable blanking plug and a wireline operated fishing tool for use in a flow conduit located within a borehole; said retrievable blanking plug having a main body, means on said main body by which said plug can be placed in sealing engagement with the inside peripheral wall surface of the flow conduit; a lifting member connected to said main body for engagement with said fishing tool; anchor means including release means connected to said main body for releasably engaging the inside peripheral wall of the flow conduit so that the plug can be anchored therewithin; means forming an obstructed flow passageway through said main body; means on said fishing tool by which said obstructed flow passageway is made unobstructed when engaged by the last said means so that the pressure across the plug can be equalized when said fishing tool is placed in a first position of engagement with said lifting member; means connected to said fishing tool for causing said anchor means to be disengaged from the flow conduit when said fishing tool is placed in a second position of engagement with said lifting member; whereby said fishing tool can be positioned in said first position of engagement relative to said plug to enable the pressure across the plug to be equalized, whereupon said fishing tool can then be placed in the second position of engagement with said lifting member so that the plug is released from engagement with respect to the conduit, thereby enabling the fishing tool to lift the plug from the flow conduit.

7. The improvement of claim 6 wherein said fishing tool is a wireline operated overshot having a skirt member located thereon; said skirt member has an expandable inwardly directed lower circumferentially extending edge portion; said lifting member being an enlargement about which said skirt member is received when the skirt member is telescopingly moved in a downward direction thereover so that the inwardly directed edge portion of the skirt can be latched onto the enlargement thereby enabling the fishing tool to lift the plug from the conduit.

10. The improvement of claim 7 wherein said fishing tool includes a probe for providing said releasing means; said pressure equalizing means include a stop means, and further including a lower stop means positioned to be contacted by said probe before the release means is retracted; said lifting member includes an upper and lower enlargement about which said skirt member is received when the skirt member is moved in a downward direction, so that the inwardly directed edge portion of the skirt can be latched onto either of the enlargements.