WELLBORE OVERSHOT

Abstract: An overshot (100) is provided for engaging and retrieving a collapsed coiled tubing in a wellbore. In one aspect the overshot has a body member (102) with a top, a bottom, and a body channel (109, 110, 111, 112) therethrough from top to bottom, the body member having a slip chamber (123, 124), at least one slip (121, 122) movably disposed in the slip chamber of the body member, and movable on at least one inclined rail (130) in the slip chamber so that, upon contacting the collapsed coiled tubing, upward movement of the body member results in downward movement of the at least one slip (121, 122) which also moves the at least one slip inwardly in the body member (102) thereby increasing gripping force of the at least one slip on the collapsed coiled tubing. Methods are also provided for using such overshots.

Description: WELLBORE OVERSHOT BACKGROUND OF THE INVENTION Field Of The Invention The present invention is directed to wellbore overshots and, in one particular aspect, to overshots for tubing. In one specific embodiment the present invention is directed to an overshot for engaging and retrieving collapsed coiled tubing. Description of Related Art The prior art discloses a wide variety of wellbore overshots for engaging and retrieving tubulars and other "fish" used in a wellbore. Often in using coiled tubing, the tubing collapses. There has long been a need for an overshot useful in a wellbore to effectively engage and retrieve collapsed coiled tubing. Fig. 1 shows a prior art overshot 10 with an outer cover sleeve 20, a mandrel 30 disposed substantially within the cover sleeve 20, and a body member 40 disposed within the cover sleeve 20 opposite the mandrel 30. One or more set screws 21 secures the mandrel 30 within the cover sleeve 20. A lower end 22 of the cover sleeve 20 projects down below a lower end 31 of the mandrel 30 and a lower end 41 of the body member 40. Preferably the lower end 22 of the cover sleeve is sized and disposed for encompassing a top of collapsed coiled tubing or a fish. A top end 32 of the mandrel 30 has a threaded portion for releasably connecting the overshot to a work string. The body member 40 has an upper shoulder 42 that abuts a lower shoulder 33 of the mandrel 30. An alignment pin 11 extends through the body member 40 and the mandrel 30. A plurality of slips 60 are each movably disposed in a corresponding slip channel 43 of the body member 40. A spring 61 biases each slip downwardly. A portion of each spring 61 extends through a spring channel 63 in each slip body 62. The mandrel 30 has an inner wall 35 with upwardly directed teeth 36. Each slip 60 has an outer surface 64 with upwardly directed teeth 65. The inner wall 35 of the mandrel 30 and an inner wall 45 of the body member 40 define a space S into which part of a fish or coiled tubing may project for gripping between the mandrel 30 and the slips 60. Each slip 60 has a lower inclined surface 66 which corresponds to and rides on a lower inclined surface 46 of each slip channel 43 of the body member 40. Each slip 60 has an upper inclined surface 68 which corresponds to and rides against an upper inclined surface 48 of the slip channels 43. Each slip 60 has a lower inclined surface 80 against which a fish or tubing may push or be pushed to push the slip up in its slip channel thereby permitting the fish or tubing to enter into the space S between a slip and the inner wall of the mandrel so that the fish or tubing may be gripped therebetween. The slips are sized so that they cannot exit their slip channels into the space S and cannot fall out of the overshot. A shoulder 69 of each slip abuts a shoulder 49 of the body member to prevent further upward slip movement. A pointed end 37 of the mandrel 30 and a pointed end 47 of the body member 40 facilitate reception of a fish or tubing within the overshot and movement of the fish or tubing into the space S. SUMMARY OF THE PRESENT INVENTION The present invention, in certain embodiments, discloses an overshot for engaging and retrieving a collapsed coiled tubing in a wellbore, the overshot having a body member with a top, a bottom, and a body channel therethrough from top to bottom, the body member having at least one slip chamber, at least one slip movably disposed in the at lest one slip chamber of the body member, the at least one slip movable on at least one inclined rail in the at least one slip chamber so that, upon contacting the collapsed coiled tubing, upward movement of the body member results in downward movement of the at least one slip which also moves the at least one slip inwardly in the body member thereby increasing gripping force of the at least one slip on the collapsed coiled tubing. The invention, in certain embodiments, also provides an overshot for engaging and retrieving a collapsed coiled tubing in a wellbore, the overshot com- prising: a body- member with a top, a bottom, and a body channel therethrough from top to bottom, the body member having four slip chambers, two pairs of slips, one pair above the other, each slip movably disposed in the slip chamber of the body member, each slip movable on two inclined rails in its slip chamber so that, upon contacting the collapsed coiled tubing, upward movement of the body member results in downward movement of the slips which also moves the slips inwardly in the body member thereby increasing gripping force of the slips on the collapsed coiled tubing, and each slip removably held in its respective slip chamber by a releasable stop member, and each slip having a toothed outer gripping surface to facilitate gripping of the collapsed coiled tubing. In certain aspects, the present invention discloses a method for engaging collapsed coiled tubing in a wellbore with an overshot, the method including: introducing an overshot into a wellbore to contact the collapsed coiled tubing in the wellbore, the overshot having a body member with a top, a bottom, and a body channel therethrough from top to bottom, the body member having two slip chambers, two slips each movably disposed in each slip chamber of the body member, each slip movable on an inclined rail in a corresponding slip chamber so that, upon contacting the tubing, upward movement of the body member results in downward movement of the slips which also moves the slips inwardly in the body member thereby increasing gripping force of the slips on the collapsed coiled tubing; engaging the tubing with the overshot, and removing the overshot and tubing from the wellbore. DESCRIPTION OF PREFERRED FEATURES In a preferred form of the overshot, there are provided two opposed slips, a first slip and a second slip opposite the first slip, each slip being located in a slip chamber in the body member, and each slip being movably mounted on at least one inclined rail. In an overshoot as aforesaid, there may be provided a third slip and a fourth slip opposite the third slip, each in a slip chamber in the body member and movably mounted on at least one inclined rail, the third and fourth slips being located lower than the first and second slips. A slip as aforesaid may further comprise a bearing body, another member connected to said body member, and a bearing providing a rotatable connection between the bearing body and said other member. Preferably the at least one slip has a toothed outer gripping surface to facilitate gripping of the collapsed coiled tubing. A hollow sub may be connected to the top of the overshot for receiving a portion of the collapsed coiled tubing and the method of the invention preferably also includes receiving a portion of the collapsed coiled tubing in the hollow sub. For a better understanding of the invention reference will now be made, by way of example only, to the accompanying drawings, in which: Fig. 1 is a side view in cross-section of a prior overshot; and Figs. 2A and 2B are side views in cross-section of an overshot according to the present invention; and Fig. 2C is a cross-section view of the overshot taken on line 2C-2C of Fig. 2S. DESCRIPTION OF PREFERRED EMBODIMENTS Figs. 2A - 2C show an overshot 100 according to the present invention with a body 102 secured with pins 103 to a rotatable member 104. The member 104 is rotatable with respect to an upper sub 105 on bearings 106 disposed between the bushing 104 and upper sub 105. The sub 105 and any hollow tubular(s) above it may "swallow" part of a collapsed coiled tubing. A lower body 106 is secured with pins 107 to the body 102. A downwardly extending lip or profile 108 on the lower body 106 facilitates entry of a fish or collapsed tubing into a channel 109 that extends through the body 102. Fluid is flowable through the overshot 100 through a channel 110 of the upper sub 105, a chan- nel 111 of the connector 104, the channel 109 of the body 102, and a channel 112 of the lower body 106. The body 102 is generally cylindrical as are the various channels mentioned above. An upper slip pair 120 includes movable slip mem- bers 121 and 122 which are movable in chambers 123 and 124. Stop blocks 125, 126 secured to the body 102 with bolts or pins 128 hold the movable slip members on lips or rails 130 that project into recesses 127 on each slip. Lower slip members 128, 129 are like the slip members 121, 122 and move in chambers 163, 164. As shown in Fig. 2C, each movable slip member may have a serrated or toothed outer surface 140 to facilitate gripping of a fish or tubing. As shown in Fig. 2A, the movable slip members 121, 122, 128, 129 are initially in an "up" position in their respective chambers. As the overshot 100 moves down and encounters and engages a fish or tubing, part of the fish or tubing moves up in the channel 109 and may move into the sub 105. Once the fish or tubing is gripped between the pairs of slips and an upward pull is applied to the overshot, the body 102 may move upwardly with respect to the fish or tubing therein. If the fish or tubing moves down with respect to the body 102, the movable slip members move down with the fish or tubing and, as they move down, their grip on the fish or tubing increases in force due to the generally inward movement of the movable slip members as they move down ( see slip member position in Fig. 2B). The inward movement of the movable slip members is effected by the inclination of the lips or rails 130, the inclination of the slip chambers, and the corresponding inclined rear surface 170 of each slip and inclined inner surfaces 172 of each chamber.

Claims: CLAIMS : 1. An overshot for engaging and retrieving a collapsed coiled tubing in a wellbore, the overshot comprising a body member with a top, a bottom, and a body channel therethrough from top to bottom, the body member having at least one slip chamber, at least one slip movably disposed in the at least one slip chamber of the body member, and at least one inclined rail in the at least one slip chamber on which the at least one slip is movable so that, upon contacting the collapsed coiled tubing, upward movement of the body member results in downward movement of the at least one slip which also moves the at least one slip inwardly in the body member thereby increasing gripping force of the at least one slip on the collapsed coiled tubing. 2. The overshot of Claim 1, wherein there are a first slip and a second slip opposite the first slip, each slip being located in a slip chamber in the body member, and each slip being movably mounted on at least one inclined rail. 3. The overshot of Claim 2, further comprising a third slip and a fourth slip opposite the third slip and a fourth slip, each in a slip chamber in the body member and movably mounted on at least one inclined rail, the third and fourth slips being positioned lower than the first and second slips. 4. The overshot of any preceding claim, further comprising a bearing body, another member connected to said body member, and a bearing providing a rotatable connection between the bearing body and said other member. 5. The overshot of any preceding claim, wherein the at least one slip has a toothed outer gripping surface to facilitate gripping of the collapsed coiled tubing. 6. An overshot for engaging and retrieving a collapsed coiled tubing in a wellbore, the overshot comprising a body member with a top, a bottom, and a body channel therethrough from top to bottom, the body member having four slip chambers, two pairs of slips, one pair above the other, each slip movably disposed in the slip chamber of the body member, each slip movable on two inclined rails in its slip chamber so that, upon contacting the collapsed coiled tubing, upward movement of the body member re- suits in downward movement of the slips which also moves the slips inwardly in the body member thereby increasing gripping force of the slips on the collapsed coiled tubing, and each slip removably held in its respective slip chamber by a releasable stop member, and each slip having a toothed outer gripping surface to facilitate gripping of the collapsed coiled tubing. 7. A method for engaging collapsed coiled tubing in a wellbore with an overshot, the method comprising introducing an overshot into a wellbore to contact the collapsed coiled tubing in the wellbore, the overshot comprising a body member with a top, a bottom, and a body channel therethrough from top to bottom, the body member having two slip chambers, two slips each movably disposed in each slip chamber of the body member, each slip movable on an inclined rail in a corresponding slip chamber so that, upon contacting the tubing, upward movement of the body member results in downward movement of the slips which also moves the slips inwardly in the body member thereby increasing gripping force of the slips on the collapsed coiled tubing, engaging the tubing with the overshot, and removing the overshot and tubing from the wellbore. 8. The method of Claim 7, wherein a hollow sub is connected to the top of the overshot for receiving a portion of the collapsed coiled tubing and the method further comprising receiving a portion of the collapsed coiled tubing in the hollow sub.

Inventors: GAMPER JOSEPH WILLIAM, GAMPER, JOSEPH, WILLIAM
Applicants: LUCAS BRIAN RONALD, WEATHERFORD LAMB, LUCAS, BRIAN, RONALD, WEATHERFORD/LAMB, INC.
Application year: 1998
Main classification: E21B31
IPC codes: E21B31