APPARATUS AND METHOD FOR RETRIEVING AN OBJECT FROM A WELLBORE

Abstract: Apparatus (1; 100) for retrieving an object (30) from a wellbore (35), the apparatus comprising a hollow body (2; 104) able to be secured at its uphole end to a well string or tube (36), the hollow body (2; 104) having mounted on it an actuator (6, 106) which is movable longitudinally of the body (2; 104) between a rest position and an operative position and is biased towards its rest position by a spring (12, 114) and a plurality of circumferentially-spaced, longitudinally-extending fingers (20; 140) at its downhole end, the fingers (20; 140) having radially-directed ends (145) adapted to engage in an annular recess (31) in the uphole end of the object (30) to be retrieved, the fingers (20; 140) being movable between an inoperative position, in which, in use, the apparatus is able to move longitudinally relatively to the object (30) and an operative position, in which the fingers enter and engage the recess (31) in the object (30) so as to secure the object against relative longitudinal movement, wherein the movement of the fingers is facilitated by movement of the actuator relative to the fingers, which movement is effected by the flow of hydraulic fluid through the body (2; 104) so as to counteract the spring bias. The apparatus may take the form of a spear fishing tool or an overshot fishing tool.

Description: Apparatus and Method for retrieving an object from a Wellbore This invention relates to an apparatus and a method for retrieving an object from a wellbore. According to one aspect of the present invention there is provided an apparatus for retrieving an object from a wellbore, the apparatus comprising a hollow body able to be secured at its uphole end to a well string or tube, the hollow body having mounted on it an actuator which is movable longitudinally of the body between a rest position and an operative position and is biased towards its rest position by a spring and a plurality of circumferentially-spaced, longitudinally-extending fingers at its downhole end, the fingers having radially-directed ends adapted to engage in an annular recess in the uphole end of the object to be retrieved, the fingers being movable between an inoperative position, in which, in use, the apparatus is able to move longitudinally relatively to the object and an operative position, in which the fingers enter and engage the recess in the object so as to secure the object against relative longitudinal movement, wherein the movement of the fingers is facilitated by movement of the actuator relative to the fingers, which movement is effected by the flow of hydraulic fluid through the body so as to counteract the spring bias. Further features of this invention can be gathered from Claims 2 to 7. The present invention also provides a method of gripping and selectively releasing an object in a wellbore which method comprises the steps of: lowering into the wellbore a retrieving apparatus having a body, at least one finger in the body, the finger having a lobe on one end for engaging the object, and a fluid-responsive actuator movable with respect to the body, and moving the actuator with respect to the body to move the finger(s) to engage the object. Further features of the invention will be gathered from Claims 9 et seq. For a better understanding of the present invention and to show how the same may be carried into effect reference will now be made, by way of example, to the accompanying drawings, in which: Fig. 1 is a side view, partially cut-away, of one embodiment of an apparatus in accordance with the present invention in use; Fig. 2 is a longitudinal sectional view of a second embodiment of an apparatus in accordance with the pre- sent invention; Fig. 3 is an end view taken on line III-III of Fig l; Fig. 4 is an end view taken on line IV-IV of Fig 2; Fig. 5 is an exploded view of the apparatus of Figs. 2, 4 and 5; Figs 6A to 6D show sequential steps in the recovery of a fish using the apparatus shown in Figs. 2, 4 and 5, the apparatus being shown mainly in cross- section and the fish being shown in side elevation with a major portion cut-away to show the interaction between the components of the apparatus and the fish; and Figs. 7A and 7B are cross-sectional views of a third embodiment of an apparatus in accordance with the present invention. Figures 1 and 3 and Figures 2, 4 and 5 of the accompanying drawings show two embodiments of an apparatus in accordance with the present invention in the form of spear fishing tools; i.e. tools which are arranged to recover a fish by engagement with the internal surface thereof. Since the only difference between the two embodiments is the number of fingers 20 ( four in the case of the embodiment of Figs 1 and 3 and three in the case of the embodiment of Figs, 2, 4 and 5) the same reference numerals have been used on each embodiment. Referring to Fig 2, the spear fishing tool has been generally identified by the reference numeral 1. The spear fish tool 1 comprises a cylindrical housing 2 which is attached to a male portion 27 of a top sub 26 by screw threads 3. A seal 9 is provided between the cylindrical housing and the top sub 26 as shown. The top sub 26 is provided with a bore 29 and an internal thread 28 for attachment to a length of tubing 36 having a complementary male thread 37. The exterior of the cylindrical housing 2 is step- ped and has an intermediate portion 4 which is provided with threads and a nose portion which is provided with circumferentially spaced latch seats 15 (Fig 5) and terminates in a bevelled tip 2a. The interior of the cylindrical housing 2 is also stepped terminating in an internal shoulder 5 which supports one end of a spring 12 which extends upwardly through a chamber 14 and a chamber 13 and engages against a shoulder 11 of a piston 6 which is slidably disposed within the cylindrical housing 2. A bore 6a having a frusto-conical opening 10 extends longitudinally along the interior of the piston 6 whilst the exterior is provided, at one end, with a groove 7 and, at the other end, with two 0-ring seals 8. A cap 16 having threads 17 is screwed onto the intermediate portion 4 of the cylindrical housing 2. The cap 16 retains captive the bases 23 of latch fingers 20 which are each provided with a lobe 22 having bevelled surfaces 24. The bottom of the lobes 22 normally rest on the bottom 15a of the latch seats 15. Each of the latch fingers 20 has a shoulder 21 which faces the bottom 18 of the cap 16 which is provided with a central opening 19. The operation of the spear fishing tool Figs. 2, 4 and 5 will now be described with reference to Fig 6A to 6D. For this purpose it will be assumed that it is desired to recover a fish 30 from within a casing 35. The fish 30 has an entrance opening 32 which leads to a recovery groove 31 which is shaped to accommodate the lobes 22 of the latch fingers 20. At the commencement of the retrieval operation the spear fishing tool 1 is lowered by means of the top sub 26 and the tubing 36 (or other suspension apparatus) into the well bore 34. As the spear fishing tool 1 approaches the fish 30 the nose of the cylindrical hous- ing 2 enters the entrance opening 32 and the lower bevelled surface 24 of each latch finger 20 contacts the fish 30. Hydraulic fluid, for example sea water or drilling mud, is pumped down the tubing 37 initially at a rate such that it passes through the bore 6a and removes any sediment from the recovery groove 31 (Fig. 6A). The flow of hydraulic fluid is then increased so that the piston 6 is forced downwardly against the bias of spring 12 to occupy the position shown in Fig. 6 B. In this position the groove 7 is aligned with the respective lobes 22 of the latch fingers 20, and the pressure of the fish 30 against the respective lower bevels 24 of the latch fingers 20 pivots each latch finger 20 about its base 23 and urges the lobes 22 radially into the groove 7, thus facilitating penetration of the spear fishing tool 1 further into the entrance opening 32, as illustrated in Fig. 6C. Each of the latch fingers 20 remains depressed, with its lobe 22 seated in the groove 7 as the working end of the spear fishing tool 1 moves into the entrance opening 32 and the latch fingers 20 align with the conventional recovery groove 31 provided in the fish 30, as illustrated in Fig. 6C. When alignment of the latch fingers 20 with the recovery groove 31 is effected, hydraulic fluid 33 pres- sure is released from the tubing 36 and the spring 12 extends, thus moving the piston 6 upwardly with respect to the cylindrical housing 2, as shown in Fig. 6D. This action misaligns the groove 7 with the corresponding lobes 22 in the latch fingers 20 and forces the lobes 22 radially outwardly from the groove 7 and pivotally from the base 23, such that the latch fingers 20 now engage and are seated in the recovery groove 31 of the fish 30. The tool 1 is now securely, yet removably, engaged with the fish 30, and the fish 30 may be removed by lifting the spear fishing tool 1. When it is desired to disengage the spear fishing tool 1 from the fish 30, after either relocating the fish 30 or for other purposes, hydraulic fluid 33 is again pumped down the tubing 36 at a rate sufficient to displace the piston 6 downwardly against spring 12, to align the groove 7 with the lobes 22 of the fingers 20. The spear fishing tool 1 is then lifted and, as pressure is exerted against the top bevel 24 by the fish 30, each lobe 22 is depressed into the aligned groove 7 and the spear fishing tool 1 is quickly and easily disengaged from the fish 30, through the entrance opening 32, as illustrated in Figs. 6C and 6B. When the flow of hydraulic fluid 33 is reduced the piston 6 returns to the position illustrated in Fig. 6A by operation of the spring 12. The spear fishing tool 1 incorporates a single internal spring and requires no external springs for operation of the respective latch fingers 20. The spear fishing tool 1 may be quickly and easily repaired, and the latch fingers 20 removed, replaced or repaired, by unthreading the collar 16 from the cylindrical housing 2. Furthermore, referring to Fig. 3 of the drawings, a selected number of latch fingers 20, can be mounted in the spear fishing tool 1 depending upon the lifting force required to remove the fish 30 and the desired diameter of the cylindrical housing 2. Moreover, fishing tools in accordance with the present invention can be constructed in substantially any size for operation in cased and uncased wellbores of varying diameter and with engagement of fish of varied description, in substantially any working environment. Moreover, the spear fishing tools are compatible with fluid pumps, including conventional mud pumps, hydraulic pumps and other hy- draulic fluid and working fluid pressure apparatus for downhole operation, since working fluid pressure is applied to the tubing in a conventional manner. Referring again to Figs. 1 and 2 of the drawings, the groove 7 can be either a continuous groove, as illustrated or multiple short grooves, depending upon the desired design of the working end of the cylindrical housing 2. For example, separate and discrete grooves 7 could be provided where the fingers 20 are mounted radially around the diameter of the cylindrical housing 2 and in the areas where the respective lobes 22 align with the piston 6. In each case, the lobes 22 of the respective latch fingers 20 are able to be housed in the groove(s) during operation of the spear fishing tool 1, as described. Figs. 7A and 7B show a third embodiment of an apparatus in accordance with the present invention in the form of an overshot fishing tool i.e. a tool which is arranged to recover a fish by engagement with the external surface thereof. The overshot fishing tool, which is generally identified by the reference numeral 100, has an upper sub 102 screw-threaded to an inner body 104. A sleeve 106 is movably disposed around the upper sub 102 and inner body 104. Several latch fingers 140 (three shown in Fig. 7A ) are disposed in slots 152 in the inner body 104 and are hingedly connected to a lower end of the inner body 104 and biased outwardly by springs 108. The upper sub 102 has a fluid flow bore 110 which is in fluid communication with a fluid flow bore 112 of the inner body 104. A spring 114 acts between the lower end 116 of the upper sub 102 and a shoulder 118 of the sleeve 106. Seals (e.g. 0-rings) 120 in recesses 122 of the sleeve 106 and 123 of the inner body 104 seal the sleeve/inner body interfaces. An outer surface 124 of the inner body 104, and an inner surface 126 of the sleeve 106, define a chamber 150 which is in fluid communication with the fluid flow bore 112 of the inner body 104 via channels 128. The introduction of fluid (e.g. pumped from the surface down through a tubular string to which the overshot fishing tool 100 is connected) at sufficient rate maintains the spring 114 in the compressed "run-in" position of Fig. 7A. The pumped fluid (e.g. water or drilling fluid) flows out through the lower end 130 of the inner body 104. Reduction of the flow of the pumped fluid allows the spring 114 to push the sleeve 106 down to contact projections 142 of the latch fingers 140, overcoming the force of the springs 108 which are interconnected between ribs 136 of the inner body 104 and the ends 148 of the latch fingers 140, thereby pivoting the latch fingers 140 about pivots 141. The latch fingers 140 have inner projections 145 which are movable inwardly to grasp a fish and to enter into a recess or recesses on the outside of the fish (not shown) to facilitate gripping thereof and removal. The sleeve 106 maintains the fingers 140 in the "set" position of Fig. 7B until fluid at sufficient flow to generate the required pressure is again pumped into the chamber 150, pushing the sleeve 106 up against the force of the spring 114 and releasing the fingers 140 from their "set" positions for return to their "run-in" positions of Fig. 7A.

Claims: CLAIMS 1. Apparatus (1; 100) for retrieving an object (30) from a wellbore (35), the apparatus comprising a hollow body (2; 104) able to be secured at its uphole end to a well string or tube (36), the hollow body (2; 104) having mounted on it an actuator (6; 106) which is movable longitudinally of the body (2; 104) between a rest position and an operative position and is biased towards its rest position by a spring (12, 114) and a plurality of circumferentially-spaced, longitudinally- extending fingers (20, 140) at its downhole end, the fingers (20; 140) having radially-directed ends (145) adapted to engage in an annular recess (31) in the uphole end of the object (30) to be retrieved, the fingers (20; 140) being movable between an inoperative position, in which, in use, the apparatus is able to move longitudinally relatively to the object (30) and an operative position, in which the fingers enter and engage the recess (31) in the object (30) so as to secure the object against relative longitudinal movement, wherein the movement of the fingers is facilitated by movement of the actuator relative to the fingers, which movement is effected by the flow of hydraulic fluid through the body (2; 104) so as to counteract the spring bias. 2. Apparatus as claimed in Claim 1, in which the actuator takes the form of a piston ( 6 ) having a stem provided at its downhole end with one or more recesses ( 7 ) able to accommodate at least part of the end of at least one finger when radially aligned therewith, to allow the finger to move inwardly into its inoperative position, the piston (6) being movable axially against the spring bias between its rest position, in which the finger is maintained in its outwards, operative posi- tion, and its operative position, in which the finger can move inwardly into its inoperative position. 3. Apparatus as claimed in Claim 2, in which the piston stem has in it a passage (6a) for liquid by means of which a jet of liquid may issue from the end of the stem to flush out loose debris from the interior of a recovery groove (31) adjacent the end of the object (30), and in which the face of the piston has in it a recess (10) on which hydraulic fluid may act to move the piston against the force of the bias spring. 4. Apparatus as claimed in Claim 2 or 3 , in which the uphole end of each finger is captive in a chamber (18) formed between the piston stem, the body (2) and a collar (16) secured to the body intermediate its ends. 5. Apparatus as claimed in Claim 1, in which the actuator takes the form of a sleeve (106) slidable on the outside of the body (104), the sleeve forming with the body a chamber in which the bias spring (114) is housed and a chamber (150) which is in communication with a central passage (112) in the body via transverse passages (128) and in which the body ends at its down- hole end in a cuff (130) intended to fit over the end of an object to be retrieved, the fingers (140) being pivotally mounted on the cuff for pivotal movement relative to radially-aligned openings (152) in the cuff, in which in its rest position the sleeve allows the free ends of the fingers to move outwardly into their inoperative position and, in its operating position the sleeve holds the finger ends inwardly in their operative positions. 6. Apparatus as claimed in Claim 5, in which each finger (140) is biased outwardly into its inoperative position by means of a biasing spring (108) positioned between a rib (136) projecting inwardly from the cuff body and the free end of the respective finger. 7. Apparatus as claimed in any preceding claim, in which the hollow body (2) is connected to a hollow upper sub (26, 102) connectable to, or forming part of, a tubular string or tube by means of which hydraulic fluid at a controllable flow rate is supplied to the apparatus so as to control the position of the actuator. 8. A method of gripping and selectively releasing an object (30) in a wellbore (35) which method comprises the steps of: lowering into the wellbore a retrieving apparatus (1; 100) having a body (2; 104), at least one finger (20; 140) in the body, the finger having a lobe (145) on one end for engaging the object, and a fluid-responsive actuator (6; 106) movable with respect to the body, and moving the actuator with respect to the body to move the finger(s) to engage the object. 9. A method according to Claim 8, further comprising the steps of: sending operating fluid under pressure into a chamber (150) of the retrieval apparatus, of which the body (104) has a longitudinal fluid flow channel (112) from one end to the other, and at least one lateral channel (128) in fluid communication with the channel, the downhole end (130) having in it an opening for receiving therein a portion of an object to be re- trieved, the actuator (106) being reciprocable with respect to the body, and being biased by a spring (114) towards a limit position with respect to the body, the chamber being between the body and the actuator, a plurality of slots (152) in the downhole end, a plural- ity of fingers (140) movably connected to the body, each finger being initially disposed in one of the slots, and the actuator disposed so that the spring can push the actuator to contact the fingers and move them into the bore of the body to engage the object when in the open- ing when the fluid pressure in the chamber is insuffi- cient to overcome the bias ; lowering the retrieval apparatus into the wellbore to contact and embrace the uphole end of the object to be retrieved; stopping the flow of fluid to the retrieval apparatus so that the bias moves the actuator to contact and move the fingers through their slots to engage the object; and removing the retrieval apparatus and object from the wellbore. 10. A method according to Claim 9, further comprising the step of: ejecting a stream of fluid from the apparatus to flush loose debris from the end of the object.

Inventors: BEEMAN ROBERT STEPHEN, HAWN CLIFFORD W, BEEMAN, ROBERT, STEPHEN, HAWN, CLIFFORD, W.
Applicants: LUCAS BRIAN RONALD, WEATHERFORD LAMB, LUCAS, BRIAN, RONALD, WEATHERFORD/LAMB, INC.
Application year: 1997
Main classification: E21B31
IPC codes: E21B31