Patent Publication Number: US-6338504-B1

Title: Connector

Description:
This invention relates to a connector, and relates more particularly but not exclusively to a connector for connecting coiled tubing to a Bottom Hole Assembly (BHA) in a manner allowing for selective action at a remote location to cause the connector to disconnect the coiled tubing from the BHA. 
     Coiled tubing is a form of non-rigid hollow pipe designed for use in well bores to transmit mechanical torque and tension from a surface location to a BHA or other downhole entity, and to convey hydraulic fluid at pressure along the hollow interior of the tubing. At the same time (and unlike a conventional rigid drillstring), coiled tubing has sufficient flexibility to allow a substantial length of tubing to be stored on a reel in the manner of a hose. (This gives rise to the term “coiled”; in normal use, “coiled” tubing is de-coiled and is more or less straight, at least when in a wellbore). 
     With the continued and increasing use of coiled tubing for drilling, milling and workover applications in oilfield well-bores there is a need for more reliable and robust equipment which can be attached to the end of coiled tubing depending on the application and the work which is to be performed in the well-bore. Such equipment and tools are generally termed the “Bottom Hole Assembly” or “BHA”. On the majority of coiled tubing jobs, irrespective of application or equipment being used, there is the potential for the BHA to become stuck in the well-bore. In order to help alleviate the problems this can cause, certain “emergency release” tools are available which can be used along with the BHA. These emergency release tools or “disconnects” are widely available from many suppliers and are fairly generic in design and method of activation. This familiarity and common design has the advantage that people are familiar in the way they operate and perform so eliminating potential problems that might arise from unfamiliarity with different methods of operation. 
     Disconnect tools are only utilised in an emergency situation if the BHA becomes stuck and the coiled tubing cannot be removed from the well-bore. The disconnect allows the coiled tubing to be safely parted at a known point within or adjacent the BHA, thus permitting the coiled tubing to be removed from the well-bore and a ‘fishing’ string to be used to remove the stuck tools separately. This fishing string would latch into a retrieval profile on the lower half of the disconnect tool with a specifically designed pulling tool. 
     In order to activate the disconnect tool, most known designs require a ball of specific size to be dropped from the surface through the coiled tubing until it reaches a ball seat within the disconnect. Once the ball has reached the disconnect, fluid flow is no longer possible through the coiled tubing. At this point the internal hydraulic pressure in the coiled tubing is increased to activate the release mechanism within the disconnect. This allows controlled separation of the upper and lower parts of the disconnect. 
     Conventional disconnect tools comprise two body members which are rotationally coupled together by a torque clutch mechanism in the form of corresponding castellations mounted on each coupling face of the body members. The conventional disconnect tools are longitudinally coupled by sprung outwardly loaded fingers which extend through the inner bore from one of the body members, over the castellated coupling, and latch onto a recess on the inner bore of the other body member. 
     The sprung outwardly loaded fingers are further pushed out, prior to disconnect, by a moveable piston which seats the fingers into the recess. When a ball is introduced, it lands on the piston, and moves the piston so that the fingers are no longer pushed into the recess, and which can move inwardly when the two body members are pulled apart, which disconnects the two body members. 
     According to the present invention there is provided a connector comprising first and second body members for connection to respective first and second entities to be connected together such that in use of the connector when the first and second body members are connected to the first and second entities respectively, the connector forms a substantially rigid connection between the first and second entities and is capable of transmitting mechanical forces therebetween, the first and second body members being mutually coupled by a first coupling arrangement on the first body member and a second coupling arrangement on the second body member, said first coupling arrangement comprising a plurality of discrete segments having respective segment surfaces which together define a formation engageable with a formation of the second coupling arrangement, and support means to support the segments in respective connection positions on the first body member in which the respective segment surfaces collectively form the first coupling arrangement, and release means selectively operable to disable the support means to cause or allow the segments to be displaced from their respective connection positions and disengage from the second coupling arrangement thereby mutually disconnecting the first and second body members of the connector. 
     Preferably, the first coupling arrangement is a first screw thread surface, the second coupling arrangement is a second screw thread surface, and the first and second screw thread surfaces are engaged when the first and second body members are connected. 
     Said segments may each be part-cylindrical. The segment surfaces collectively forming the first screw thread surface may be radially external surfaces of the segments, with the segments being displaced from their respective connection positions in respective directions each including a respective radially inward component. The support means may comprise a retainer member to retain each segment in a respective radially outwardly displaced position, and the release means may comprise retainer withdrawal means selectively operable to withdraw the retainer member from a segment-retaining position so as to allow the segments to move radially inwards and thereby disengage from the second screw thread surface. The retainer member may comprise wedges or slips insertable radially under each segment, and withdrawable by an axial sliding movement. The support means and the release means may be conjoined into a single component or assembly including a normally-open longitudinal through passage selectively closable to allow the application of fluid pressure sufficient to cause the axial sliding movement inducing withdrawal of the retainer member from the segments. 
     The connector may comprise a capture means to catch the support means after operation of the release means. The capture means is preferable mounted on the first body member. 
     The segments may be located, in use, within slots, where the slots may be formed on the outer circumference of the first body member. The segments and their respective slots may comprise differing circumferential extents. The segments and their respective slots may comprise a varied width along their longitudinal axis. The segments and their respective slots may comprise tapered side edges which taper in from the radially innermost surface of the segments and their respective slots to the radially outermost surface of the segments and their respective slots. 
     Typically, the connector further comprises a load bearing member which, in use of the connector, abuts an end of the segments. 
     The first entity may be coiled tubing and the second entity may be a bottom-hole assembly, the connector functioning as a selectively operable disconnect for separating the coiled tubing from the bottom-hole assembly. 
    
    
     An embodiment of the invention will now be described by way of example, with reference to the accompanying drawings wherein: 
     FIG. 1 is an exploded half-sectional longitudinal elevation of a preferred form of connector in accordance with the invention; 
     FIG. 2 is a half-sectional longitudinal elevation of a sub-assembly of the connector; 
     FIG. 3 is a cross-section of the sub-assembly of FIG. 2, taken on the line III—III in FIG. 2; 
     FIG. 4 is a cross-section equivalent to FIG. 3 but showing the reconfiguration of components upon disconnection of the connector; 
     FIG. 5 is a half-sectional longitudinal elevation of the sub-assembly of FIG. 2 with a further component assembled thereon to form one half of the connector; 
     FIG. 6 is a half-sectional longitudinal elevation of the connector half of FIG. 5 being offered the other half of the connector; 
     FIG. 7 is a half-sectional longitudinal elevation of the fully assembled connector; 
     FIG. 8 is a half-sectional longitudinal elevation of the connector in the process of disconnecting; and 
     FIG. 9 is a schematic view of the fully assembled connector connected to a Bottom Hole Assembly (BHA) and a coiled tubing. 
    
    
     Referring first to FIG. 1, this is a half-sectional longitudinal elevation of the mutually separated components of a connector  10 . 
     The components of the connector  10  comprise an upper body member  12  and a lower body member  14 , three part-cylindrical segments  16  (only two of which are shown in FIG.  1 ), a load ring  18 , a segment support  20 , and a retainer sleeve  22 . (Further components, which are not shown in FIG. 1, will be detailed subsequently). 
     The upper body  12  is hollow and has a through bore  24  (not visible in FIG. 1 but shown in FIGS. 3 and 4 ). An end of the upper body  12  (the left end as viewed in FIG.  1 ), which will be the upper end of the connector  10  in use, is internally formed with a standard tapered thread box connector  26  (not visible in FIG. 1 but shown in FIG.  8 ). The other end of the upper body  12  is formed with three longitudinally extending slots  28  in its periphery, and a screw-threaded portion  30  which is circumferentially interrupted by the slots  28 . 
     The segments  16  each comprise a part-cylindrical member, where the first, second and third segments  16  preferably respectively have a circumferential extent of slightly less than, equal to, and slightly greater than one-sixth of a revolution, and the respective slots  28  are of a matching width. This ensures that only one segment  16  will fit into, and be retained by, each slot  28 . The radially outer surface of each segment.  16  is formed with screw-threaded portions, as an interrupted male thread whose lands correspond to the angular width of each segment  16 , the pitch circle diameter of this segment thread being somewhat greater than the pitch circle diameter of the thread on the screw-threaded portion  30  of the upper body  12 . Each segment  16  has a circumferential extent which renders it a sliding fit in a respective slot  28  (see FIGS. 3 and 4 ), and with each segment  16  only fitting in one slot  28 , this ensures that the interrupted male thread formed thereby is always correctly formed. 
     Also, the slots  28  are preferably formed to have a smaller gap at their upper most, in use, end than their lower most end, and the segments  16  are preferably formed with a correspondingly smaller width at their uppermost end. This ensures that each segment  16  will only fit in its respective slot  28  in one orientation, thereby aiding correct assembly of the connector  10 . Also, each segment  16  is preferably formed with tapered side edges  32  which are tapered from the radially innermost to the outermost surface such that the width of the radially innermost surface of the segment  16  is greater than the width of the radially outermost surface of the segment  16 . The respective slots  28  are preferably correspondingly tapered, which ensures that each segment  16  is retained within its respective slot  28 , and cannot fall radially outwardly therefrom. 
     The load ring  18  is annular, and comprises three ridges (not shown) which project radially inward to an extent to be a close but slidable fit with the outer surface of fingers  40  (which will be detailed subsequently), and which are circumferentially distributed to also lie within the slots  28 . 
     The segment support  20  comprises an annular portion  38  at its lower end (the right end as viewed in FIG. 1) from which three equi-spaced fingers  40  extend upwards (to the left as viewed in FIG.  1 ). The fingers  40  are each laterally curved at a constant radius about the longitudinal axis of the segment support  20  (which axis is coincident with the longitudinal axis of the connector  10  as a whole). The inner surface of each finger  40  is a sliding fit over the radially outer surface of a respective slot  28 , and the angular extent of each finger  40  renders it an axially sliding fit in its respective slot  28  (see FIG.  3 ). The annular portion  38  of the segment support  20  is formed with a circumferentially extending external slot  42 , for a purpose to be detailed subsequently. The annular portion  40  also has a through bore  44 . 
     The retainer sleeve  22  is generally cylindrical in form, with an inturned lip  46  at its lower end (the right end as viewed in FIG.  1 ). The inside diameter of the sleeve  22  allows the segment support  20  to be an axially sliding fit inside the sleeve  22  (see FIGS. 5-7 ), except that the inturned lip  46  catches the annular portion  38  and thereby prevents the segment support  20  sliding out of the retainer sleeve  22  when the connector  10  is separating (see FIG.  8 ). The upper end of the sleeve  22  (the left end as viewed in FIG. 1) is internally formed with a screw thread  48  dimensioned for screw-threaded engagement with the screw-threaded portion  30  on the upper body  12  when the connector  10  is assembled (see FIGS.  5 - 7 ). A series of threaded and non-threaded radially extending through holes  50  are circumferentially distributed around the sleeve  22  at about its mid-length. There are six threaded holes  50  and three non-threaded holes  50  distributed around the sleeve  22 , for a purpose to be detailed subsequently. The inner surface of the sleeve  22  is relieved around the radially inner ends of the holes  50  by means of a radially shallow circumferential slot  52 . 
     The components  12 ,  16 ,  18 ,  20  and  22  (together with shear pins (not shown in FIG. 1) which fit through the threaded holes  50  and into the slot  42  ) are assembled (as will subsequently be described) to form the upper half of the connector  10 . The lower body  14  per se forms the lower half of the connector  10 , and will now be described as a separate component. 
     The lower body  14  is a hollow cylinder and has a through bore  54 . An end of the lower body  14  (the right end as viewed in FIG. 1) which will be the lower end of the connector  10  in use, is externally formed with a standard tapered thread pin connector  56 . Near the upper end of the lower body  14  (the left end as viewed in FIG.  1 ), the lower body  14  is internally formed with a screw thread  58  dimensioned for screw-threaded engagement with the screw-threaded outer surfaces of the segments  16  in the assembled connector  10 , as will subsequently be detailed. A series of radially extending non-threaded through holes  60  is circumferentially distributed around the lower body  14  at about its mid-length. The inner surface of the lower body  14  is relieved around the radially inner ends of the non-threaded circulation holes  60  by means of a radially shallow circumferential slot  64 . 
     The non-threaded holes  60  of the lower body  14  allow circulation of fluid to occur during separation of the upper  12  and lower  14  bodies, and will be detailed subsequently. 
     Assembly of the connector components will now be described. 
     Starting with the individual components shown in FIG. 1, the first few stages of connector assembly are illustrated in FIGS. 2 and 3. The three segments  16  are slid into their respective slots  28 ; the preferable form and co-operation of the segments  16  and slots  28  ensures that (a) each segment  16  can only correctly fit within, and be retained by one slot  28 , (b) each segment  16  can only be inserted into its slot  28  in one orientation, and (c) once fully inserted into its respective slot, each segment  16  cannot fall radially outwardly therefrom. The load ring  18  is then slid over the lower (right) end of the upper body  12  (initially free of other components except for the three segments  16  ) until the three ridges of the load ring  18  are located within the lower (right) end of each slot  28 . The load ring  18  is further slid (from right to left) until its uppermost end butts the lowermost (widest) ends of the segments  16 . Thus, there is a gap between the radially innermost surface of the ridges and their respective slot  28 , into which the respective finger  40  can be slid. Next, the segment support  20  is fitted over the lower end of the upper body  12  such that the fingers  40  slide along the slots  28 , until the annular portion  38  abuts the lower end of the upper body  12 . At the same time, the fingers  40  have slid through the gap between the ridges of the load ring  18  and the slots  28 , and have also slid between the radially innermost surface of the segments  16  and the slots  28 . The upper end of the load ring  18  thus provides a load bearing surface for the segments  16 , and also prevents them from sliding (from left to right) out of their respective slot  28 . The part-assembled configuration is illustrated in FIG. 2 (elevation) and in FIG. 3 (cross-section). 
     It should be noted at this point that segments  16 , the slots  28 , and the fingers  40  are such that when the fingers  40  are fully inserted into the slots  28 , the segments  16  are held radially outwards to an extent that their threaded outer surfaces stand proud of the upper body  12  as particularly shown in FIG.  3 . However, when the fingers  40  are axially withdrawn from the slots  28 , the segments  16  are no longer held radially outwards, and it becomes feasible for the threaded outer surfaces of the segments  16  to retract radially inwards to lie substantially flush with the upper body  12 , as particularly shown in FIG.  4 . 
     As the next step in the assembly of the connector  10 , the retainer sleeve  22  is screwed on to the intermediate sub-assembly shown in FIG. 2, such that the internal thread  48  on the sleeve  22  forms a screw-threaded connection with the circumferentially interrupted thread of the screw-threaded portion  30  on the upper body  12 . When the screw threads  30  and  48  are fully engaged, the upper end of the retainer sleeve  22  (the left end as viewed in FIGS. 1 and 5) butts against the lower end of the load ring  18 , and the upper end of the load ring  18  butts against the lower end of the segments  16  as shown in FIG.  5 . For the time being, the segments  16  are supported in the particular places on the exterior of the upper body  12 , with the underlying fingers  40  of the segment support  20  holding the segments  16  radially outwards, the load ring  18  and the slots  28  together providing axial restraint while also preventing the segments  16  escaping radially outwards. It is arranged that when so anchored, the threaded outer surfaces of the segments  16  collectively form a screw thread for eventual connection with the screw thread  58  in the lower body  14 . 
     To obviate premature withdrawal of the fingers  40  from under the segments  16 , the segment support  20  is locked into place within the screwed-on retainer sleeve  22  by means of shear pins (not shown) which are screwed into the threaded holes  50  (which are internally threaded for this purpose) so as to project radially inwards of the holes  50  and into the slot  42  around the annular portion  38  forming the lower end of the segment support  20 . 
     The upper half of the connector  10  is now assembled and ready for mating with the lower half (constituted by the lower body  14  ). 
     Referring next to FIG. 6, the upper half of the connector  10  (constituted by the FIG. 5 assembly) is presented to the lower body  14 , lower end to upper end respectively. The two halves are slid together along their common longitudinal axis until the segments  16  on the upper half contact the internal thread  58  on the lower body  14 , whereupon the two halves are relatively rotated to complete the screw-threaded mutual coupling of the two halves of the connector  10 , as shown in FIG.  7 . The two halves are relatively rotated up to a pre-determined torque, the level of which will normally be the same as, or higher than the torque value of the rest of the screw connections in the string. 
     The completed connector  10  (as shown in FIG. 7) can have the box connector  26  at the upper end of the coupling  10  connected to the lower end of a coiled tubing  100 , and the pin connector  56  at the lower end of the connector  10  connected to a BHA  102  (Bottom-Hole Assembly). Thereby the connector  10  couples the coiled tubing to the BHA  102  in a mechanically rigid manner, which is optimal for downhole use, while also providing a through passage for pressurised hydraulic fluid by way of the bores  24 ,  44  and  54 . At the same time, the connector  10  allows for disconnection of the coiled tubing  100  from the BHA  102  by action taken on the surface above the well, at a time of the operator&#39;s choosing and by a standard procedure, as will now be described. 
     Referring to FIG. 8, when it is desired to separate the two halves of the connector  10 , a dropball  62  of suitable size is introduced into the bore of the coiled tubing at the surface installation above the wellbore in which the connector  10  is deployed. The dropball  62  travels through the bore of the coiled tubing along the length of the tubing, and eventually reaches the connector  10  where it passes through the box connector  26  and the bore  24 , coming to rest against the annular portion  38  at the lower end of the segment support  20 . The bore  44  through the annular portion  38  is selected to be sufficiently smaller (typically one three thousandth of an inch) than the bore of the coiled tubing, and sufficiently smaller than the bore  24  through the upper body  12 , that a dropball  62  of predetermined dimensions can readily reach the interior of the connector  10  but will inevitably be trapped against the lower end of the segment support  20 . 
     With hydraulic passage through the connector  10  blocked by seating of the dropball  62  against the upper rim of the bore  44  through the segment support  20  (as particularly shown in FIG.  8 ), enough hydraulic pressure can readily be applied down the coiled tubing leading to the upper end of the connector  10  that the piston effectively formed by the combination of segment support  20  and dropball  62  exerts a force on the shear pins projecting radially inwards from the threaded holes  50  into the slot  42  around the segment support  20  sufficient to break these shear pins and so release the segment support  20  from being locked to the retainer sleeve  22 . The same hydraulic pressure in the effective piston  20  will force the piston (dropball-blocked segment support)  20  down the sleeve  22 , so dragging the fingers  40  down the slots  28  until the fingers  40  no longer underlie the segments  16 . Now free of radially outward support, the segments  16  will tend to move radially inwards under their wedging interaction with the screw thread  58 , so taking up the positions shown in FIG.  4 . Once the segments  16  are free of the screw thread  58 , the upper and lower halves of the connector  10  are no longer rigidly coupled, and are free to move apart as depicted in FIG.  8 . 
     However, after the shear pins have been sheared, but before the two halves have reached the level of separation as depicted in FIG. 8, the connector  10  has the ability to circulate fluid from the bore  24  above the piston  20 , through the space between the fingers  40 , around the circumferential slot  52  on the sleeve  22 , through the three non-threaded circulation holes  50  in the sleeve  22 , around the circumferential slot  64  on the lower body  14 , and out through the non-threaded circulation holes  60  in the lower body  14  into the annulus between the outer surface of the connector  10  and the inner surface of the borehole. 
     If shear pins have not been inserted into some of the threaded holes  50 , then these threaded holes  50  will also aid the circulation of fluid. This circulation of fluid can occur from the time when upper ‘O’ ring seal  70  mounted in the segment support  20  moves downwardly past the threaded and non-threaded holes  50  in the sleeve  22 , until lower ‘O’ ring seal  82  mounted on the sleeve  22  moves upwardly past the non-threaded holes  60  in the lower body  14 . Prior to the ball  62  being dropped down the coiled tubing, the upper  70 ,  80  and the lower  72 ,  82  ‘O’ ring seals prevent fluid communication between the bore  24  of the connector  10 , and the annulus of the borehole. 
     The advantage of this circulation function is that the pressure drop of fluid upon commencement of circulation gives an indication to the operator at the surface that the shear pins have been sheared, and the tool is in the process of disconnecting. 
     This axial separation of the connector halves is not limited, and ultimately the two halves of the connector  10  will completely separate, so releasing the coiled tubing from the BHA. 
     A retrieval profile  85  is formed on the interior, toward the upper end, of the lower body  14 , and after the coiled tubing and upper body  12  have been removed from wellbore, a fishing tool can be inserted into the wellbore to latch onto the retrieval profile  85 . 
     Considered as both a connector for normal use, and an emergency disconnect tool, the various embodiments can yield the following advantages over the prior art: 
     1 Behaves like a conventional threaded connection until tool is activated; 
     2 Provides torsional and tensile properties of conventional threaded connection; 
     3 Elimination of clutches for torque transmission ensures maximum strength under high vibrational loading; 
     4 Strength and tool life extended due to elimination of vibration on key load-bearing parts; 
     5 Improved ease of use in the field due to minimum number of parts and no requirement for specialised equipment for assembly or disassembly; 
     6 Circulation regained once tool is activated giving surface indication that tool has functioned and allowing acid etc to be pumped if required; 
     7 No overpull required to separate upper and lower sections once the tool has been activated; 
     8 Short overall length allows it to be used in areas where height restrictions exist; 
     9 Design allows large through bore whilst maintaining optimum strength; 
     10 No internal parts remain in the lower body following disconnect, ensuring easy entry by subsequent fishing equipment; and 
     11 Standard retrieval tool can be used to latch on to the lower body. 
     While a preferred embodiment of the invention has been described above, the invention is not restricted thereto. For example, a suitable number of segments other than three could be utilised, and alternative shapes of segment supports are possible. Further, the support means could be formed from a suitable alloy known from the art which is dissolved to a substantial extent by passing an electrical current through the connector  10 , thus obviating the requirement to drop the ball  62  in order to operate the segment support  20  to disable the fingers  40 . Alternatively, the fluid pressure within the bore of the coiled tubing can be increased by a large degree such that the segment support  20  is displaced without the requirement to drop the ball  62 . Other modifications and variations can be adopted without departing from the scope of the invention.