Abstract:
A releasable coupling which can be interposed within a tubing string and the string subsequently parted by separating parts of the coupling from one another. A wire line fishing tool is used for actuating the releasing mechanism.

Description:
BACKGROUND OF THE INVENTION 
     In completing and producing oil wells, one can often foresee that a lower part of a tool string must subsequently be disconnected from the string and left downhole in the borehole. This is especially so in well completion work, wherein the lower tubing string is sometimes severed by use of clever explosive devices and dropped to the bottom of the hole. An important example of the desirability of separating a tool or pipe string is found in U.S. Pat. No. 3,706,344 to which reference is made for further background of this invention. 
     Accordingly, it is desirable to be able to separate a tool string at any predetermined location along its length. It is further desirable that the separation of the string be achieved while avoiding explosives because of the inherent dangers associated with the use of explosive devices, especially when used downhole in boreholes. Moreover, it is especially desirable that the separation of the string be effected by a wireline operation, and that it be brought about in an inexpensive and foolproof manner. 
     SUMMARY OF THE INVENTION 
     This invention relates to downhole tools, and specifically to a fluid conducting releasable coupling which can be interposed within a tool string for parting the string somewhere along its length by manipulation with a wireline fishing tool. An upper member telescopingly receives a lower member therein, with each member having means forming a plurality of radially spaced cavities within the overlaping marginal end portions thereof. A load transferring member is held into each cavity by a releasing member. The releasing member, upper member, lower member, and load transferring members are concentrically arranged relative to one another so that a fishing tool can engage and move the releasing member, thereby allowing the load transferring members to move from their respective cavities, whereupon the upper and lower members are then free to telescopingly move apart from one another. 
     Accordingly a primary purpose of this invention is the provision of a fluid conducting releasable coupling which ties together a tubing string in a releasable manner. 
     Another object of the invention is to provide a wireline actuated releasable coupling apparatus. 
     A further object of this invention is to provide a releasable coupling member having an internal member which is axially movable to cause one part of the coupling to be released from another part of the coupling. 
     A still further object of the invention is to provide a releasable coupling assembly having an unobstructed axial passageway formed therethrough. 
     The above objects of the invention are attained by the provision of telescoping members tied together by a load carrying member with the load carrying member being held in position by a releasing member, all of which are concentrically arranged respective to one another, in a manner whereby movement of the releasing member enables the telescoping members to be untied from one another. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a part schematical, part diagrammatical representation of a borehole formed within the earth, with apparatus made in accordance with the present invention being disposed therewithin; 
     FIG. 2 is an enlarged, exploded, perspective view of part of the apparatus disclosed in FIG. 1; 
     FIGS. 3 and 4 are enlarged, longitudinal, part cross-sectional representations of some of the apparatus disclosed in FIGS. 1 and 2, with some parts being removed therefrom; 
     FIGS. 5 and 6, respectively, are cross-sectional views taken along lines 5--5 of FIG. 3 and 6--6 of FIG. 4, respectively; 
     FIG. 7 is an enlarged, fragmentary, cross-sectional view of a detail of part of the apparatus disclosed in the foregoing figures; 
     FIG. 8 is a fragmentary cross-sectional view taken along line 8--8 of FIG. 9; and, 
     FIG. 9 is a fragmentary elevational view of a modification of the apparatus disclosed in FIG. 4. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In FIG. 1 there is disclosed a well head or christmas tree 10 in fluid communication with an oil producing strata 11 by means of borehole 12 which extends through the surface of the ground 14 so that production fluid flows uphole through production tubing 15. 
     Packer 16 separates the upper and lower borehole annulus and receives the production tubing therethrough. The production tubing continues at 17 and 18 in order to connect a vent string 19 to a releasable coupling 20 made in accordance with the present invention. Perforating gun 21 is connected to the releasable coupling and can be separated from the vent string at any subsequent time by manipulating the releasable coupling with a wireline actuated fishing tool of a type known to those skilled in the art. 
     Looking now to the details of the releasable coupling disclosed in the remaining figures, and especially the embodiment of FIGS. 2-7, it is seen that the coupling apparatus has an upper terminal end 22 spaced from a lower terminal end 23. The coupling is made of an upper cylindrical member 24 having a lower terminal end 25; a lower cylindrical member 26 having an upper terminal end 27; and an internal member 28, hereinafter referred to as a releasing element. The last named element can be moved to disengage the upper member from the lower member when the balls 29 are displaced from their seats as best seen diversly illustrated in FIGS. 2 and 6, and as will be more fully disclosed later on as this disclosure is more fully digested by those skilled in the art. 
     As seen in various other figures of the drawing, the tubing 15 is axially aligned with passageway 30 of the releasing element. The lower terminal end 31 of the releasing element is spaced from the inverted frusto cone 32 which forms the upper marginal end of the releasing element. The inside wall surface 33 of the upper member, inside wall surface 30 of the releasing member, and the inside wall surface 34 of the lower member form concentrically arranged chambers through which communication can be established between tubing lengths 15 and 18. 
     Radially spaced apart ball receiving chambers 35 are spaced from a seal chamber 36 within which there is disposed a resilient seal such as a Chevron ring 37. 
     The ball receiving chamber is formed by annulus 38 of the upper member which can be properly aligned with the radially spaced apart apertures 39 of the lower member, with the interior of the individual apertures being closed by the exterior wall surface 40 of the releasing member. 
     In the modification set forth in FIGS. 8 and 9, a clutch, or splined connection 44 and 46 is incorporated into a marginal outer edge portion of the lower skirt portion of the upper member so as to render the upper and lower members non-rotatable respective to one another. 
     In operation, the box end of the releasable coupling is tied into the tubing with the pin end looking downhole and connected to whatever one might desire to subsequently release therefrom. When it is desired to separate the upper and lower members from one another, a wireline fishing tool is run downhole and through the releasing member 28, with the tool engaging shoulder 31 of the releasing member. The releasing member is easily lifted so that the radially spaced balls 29 are forced from cavity 35 and into passageway 30, thereby enabling the upper member to move relative to the lower member. 
     Where it is desired to run a dry tubing into the hole, the Chevron packing prevents fluid flow into the interior of the coupling. 
     The apparatus is assembled by applying grease to the apertures 39 so that the individual balls may be held properly positioned within the individual apertures while the upper and lower members are carefully telescoped together and into the illustrated position of FIG. 3. The releasing member is placed into the illustrated position of FIG. 4, thereby capturing the balls within their individual cavities, as best seen illustrated in FIG. 6, thereby completing assembly of the tool. 
     The tool can now be interposed within a tubing string in the manner of FIG. 1, until it is desired to part the string by actuating the releasing member. The tool can be built to carry loads in excess of the breaking strength of the tubing string within which it is interposed. The individual balls rest against the curved side-wall of the annulus formed within the upper member, and against the upper wall surface of the aperture formed within the lower member, thereby developing a large bearing surface between the two members. The location of the balls within their respective cavities is such that the balls are urged radially inward with a slight force which is resisted by the outer peripheral wall surface of the releasing member. Accordingly, reciprocal movement of the releasing member allows the balls to be forced radially inwardly, thereby releasing the upper and lower members from one another. 
     Where orientation of the lower string is necessary, a splined connection is incorporated into the co-acting members at a location externally of the seal. This expedient enables the lower portion of the string to be rotated by rotational movement of the upper portion of the string. 
     The tool can be series connected between adjacent guns, a gun and a vent string, or any other tool string combination that one may desire to release from the lower end of a tubing.