Patent Publication Number: US-6712146-B2

Title: Downhole assembly releasable connection

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not Applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a releasable connection for a downhole assembly and more particularly to a releasable connection connecting a downhole tool to a coiled tubing string and still more particularly to a connection electrically actuated from the surface to disengage the coiled tubing string from a stuck downhole drilling tool or bottom hole assembly (BHA). 
     2. Description of the Related Art 
     Increasingly, the drilling of oil and gas wells is no longer a matter of drilling a vertically straight bore hole from the surface to the desired hydrocarbon zone. Rather, technology and techniques, such as directional drilling, have been developed to drill deviated, lateral or sometimes upwardly sloping boreholes. It is often not economically feasible or practical to use jointed drill pipe in extended reach wells. Therefore, tools and methods have been developed for drilling bore holes using coiled tubing, which may include one or more lengths of continuous, unjointed tubing spooled onto reels for storage in sufficient quantities to exceed the maximum length of the borehole. The coiled tubing may be metal coiled tubing or, using more current technology, composite coiled tubing. 
     In well drilling applications, a BHA, having various components, such as a downhole motor, steering assembly, and bit, is connected to the end of a coiled tubing string for drilling the borehole. Circumstances can arise in which it is desirable to disconnect the tubing string from the BHA, such as, for example, when the BHA gets stuck in the borehole during drilling and the tubing string must be disconnected from the BHA in order to facilitate fishing, jarring, or other operations for retrieving the BHA. 
     In using jointed pipe for drilling, torque can be applied to the threaded connections to actuate traditional disconnect means to disconnect the BHA. However, when using continuous tubing, such as metal or composite coiled tubing, torque can not be applied to disconnect the tubing string from the BHA, and an axial disconnection means must be utilized. Pre-installation of one or more axial release devices between the tubing string and the BHA assembly can provide a means to disconnect the coiled tubing string downhole if and when disconnection becomes necessary. 
     A variety of axial disconnect means have been used to disconnect a coiled tubing string, some of which use hydraulic or electrical lines that extend from the surface to the disconnect means to actuate a piston and cause release. One such device, described in U.S. Pat. No. 5,984,006, includes an emergency release tool that can electrically release coiled tubing from one or more downhole tools. The release tool includes a releasable slip forced against the coiled tubing by a loading nut. The coiled tubing is released by sending an electrical signal to a downhole release means. Once activated, the release means forces a piston upward until the piston engages a slip housing. The slip housing is coupled to the loading nut. The release means continues to force the piston and, consequently, the slip housing upward to separate the loading nut from the releasable slip, thereby disengaging the releasable slip from the coiled tubing. 
     Another such means, described in U.S. Pat. No. 5,323,853, includes redundant releasing mechanisms depending alternatively on either hydraulic or electrical actuation of a piston. The additional lines and cables, which run inside the well bore that are required to actuate the release, have the disadvantage of creating an obstruction to fluid flow during normal drilling operations. 
     Another type of known release means depends for actuation on directing fluid flow so as to create backpressure and actuate a piston. U.S. Pat. No. 5,718,291 describes one such release mechanism that depends for actuation on either the use of backpressure created by flow through the mechanism, or if flow is prevented, the use of built-up pressure within a passage in the mechanism. In the first mode, backpressure created by flow through a restrictor above a shiftable sleeve overcomes a biasing spring to move the sleeve through a J-slot assembly until a passage is obstructed. Thereafter, pressure buildup in a second passage overcomes a shear pin, causing a piston to move and release dogs that lock two segments of the mechanism together. If flow is prevented, pressure buildup in the second passage causes the piston to move against the shifting sleeve to overcome the force of the spring and selectively move the sleeve through the J-slot assembly. A disadvantage of this release mechanism is that aligning the sleeve properly to engage the top of the J-slot assembly is cumbersome, requiring that pressure be created and removed by turning pumps on and off from the surface. 
     Still another conventional release device depends for actuation on dropping a ball into a well from the surface, sealing a flow passage, and building up pressure behind the ball to cause a disconnection. One such ball-drop release device is described in U.S. Pat. No. 5,419,399 and includes a housing with a slideable piston disposed within and releasably connected to the housing by shear screws. A ball is dropped into the well from the surface to seat with the upper end of the piston and block the flow passage, thereby creating pressure on a mandrel of the piston sufficient to overcome the shear screws. The mandrel moves downward such that keys align to fit into annular grooves on the mandrel to disengage notches, allowing the tubing to be disconnected from the drilling apparatus. A disadvantage of this device is that the operator must pull back or agitate the device to cause the keys to drop into the grooves should they fail to do so. 
     A further ball-drop release device is described in U.S. Pat. No. 5,526,888 and includes an upper and lower housing insertably connected and locked together by latch blocks, a slotted piston that operates the latch blocks, a pilot piston, and a lock-out mechanism operated by movement of the pilot piston. A sealing ball is dropped into the well and seats with the pilot piston to create a pressure differential sufficient to overcome shear pins, thereby allowing the pilot piston to axially shift downward. Movement of the pilot piston releases a lock-out mechanism such that the slotted piston extends axially to retract the latch blocks and thereby disconnect the upper and lower housings. 
     The present invention overcomes the deficiencies of the prior art. 
     SUMMARY OF THE INVENTION 
     The disconnect assembly of the present invention connects two portions of a downhole assembly having a downhole apparatus attached to a coiled tubing string. The disconnect assembly includes a first housing connected to one portion of the downhole assembly and a second housing connected to another portion of the downhole assembly. The housings are releasably connected by a release assembly. The release assembly is coupled to a drive train on a motor by a connection transferring rotational motion into translational motion. The release assembly includes locking members having a connected position engaging both housings and a disconnected position disengaging one of the housings. The motor is connected to the surface by conductors extending through the coiled tubing whereby the motor may be actuated from the surface to move the release assembly between the connected and released positions. 
     One embodiment features a selectively actuated disconnect assembly comprising: an outer housing; an inner housing having a cavity and disposed within the outer housing; a locking assembly disposed within the cavity for releasably locking the inner housing with the outer housing; an electrically actuatable power source housed in the cavity for actuating the locking assembly; a drive train coupled to the power source; and a connection coupling the locking assembly with the drive train for engaging and disengaging the locking assembly. In one embodiment of the invention, the disconnect assembly is disposed in a downhole assembly having a bottom hole assembly attached to a coiled tubing with conductors extending to the surface to an electric motor selectively actuatable from the surface; a lead screw having first and second ends and being coupled at the first end to the electric motor; a lead sleeve coupled to the first end of the lead screw and connected to a release shaft by a universal joint, the release shaft having an exterior surface with annular grooves and a plurality of locking pins disposed in transverse bores in the inner housing with one end disposed in the release shaft grooves in the unlock and released position and another end disposed in internal grooves about the outer housing in the locked and connected position. 
     The present invention also includes methods of disengaging a bottom hole assembly from coiled tubing, a method comprising: actuating an electric motor via a command signal; rotating a lead screw that is coupled to the electric motor and to a release shaft; axially moving the release shaft a distance sufficient to align grooves on the release shaft with the inner ends of radially extending pins, and moving the release shaft to cam the other ends of the pins out of the outer housing grooves. 
     In one embodiment of the present invention, the disconnect assembly used to release a portion of the downhole assembly above a stuck point. The disconnect assembly of the present invention is most useful in coiled tubing drilling operations. A plurality of these disconnect assemblies can be deployed at different positions in the downhole assembly. This allows selective actuation of one or more of the disconnect assemblies in the downhole assembly to release that disconnect assembly which is the closest to the stuck point, thereby minimizing the length of the downhole assembly to be fished out, greatly increasing the chance of a successful fishing operation, and minimizing the damages to the BHA components during fishing. 
     A feature of the invention is that the disconnect assembly has a common electrical and mechanical connection. Further, the disconnect assembly is selectively reconnectable. This allows an operator to activate the disconnect assembly in an attempt to remove the downhole assembly. If the downhole assembly remains stuck despite the disconnect assembly having been activated, the stuck point for the downhole assembly is likely up-hole from the disconnect assembly. The operator can signal the disconnect to reconnect. The operator can then activate a disconnect assembly up-hole from the initially activated disconnect assembly. Another feature of the invention is that it does not use a taper wedge lock mechanism, which is a simple and common employment for this type of application. However, a taper wedge lock tends to seize up and become self-locking after a long period of down hole vibration in drilling, which makes release operation difficult, if not impossible. The disconnect assembly of the present invention utilizes locking pins and a release shaft. Being round in geometry, it minimizes the chance of being self-locking to prevent release. 
     Thus, the present invention comprises a combination of features and advantages which enable it to overcome various deficiencies of prior devices. The various characteristics described above, as well as other features, will be readily apparent to those skilled in the art upon reading the following detailed description of the preferred embodiments of the invention, and by referring to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more detailed description of the preferred embodiment of the present invention, reference will now be made to the accompanying drawings, wherein: 
     FIG. 1A is a schematic view of an example well with a downhole assembly; 
     FIG. 1B is an enlarged view of the bottom hole assembly shown in FIG. 1A; 
     FIG. 2 is a cross-sectional view of the composite coiled tubing of FIGS. 1A and 1B showing conductors in the wall of the tubing; 
     FIG. 3 is a longitudinal cross section of an embodiment of the disconnect assembly of the present invention in the connected position; 
     FIG. 4 is a cross sectional view along plane  4 — 4  in FIG. 3; 
     FIG. 5 is an enlarged view of a portion of the disconnect assembly shown in FIG. 3; 
     FIG. 5A is an enlarged exploded view of the universal joint shown in FIG. 5; 
     FIG. 5B is an enlarge view of the universal joint shown in FIGS. 5 and 5A; 
     FIG. 6 is a longitudinal cross-sectional view of the disconnect assembly of FIGS. 3-5 in the released position; and 
     FIG. 7 is a longitudinal cross-sectional view of the disconnect assembly of FIGS. 3-5 in the disconnected position. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention is susceptible to embodiments of different forms. There are shown in the drawings, and herein will be described in detail, specific embodiments of the present invention with the understanding that the present disclosure is to be considered an exemplification of the principles of the invention, and is not intended to limit the invention to that illustrated and described herein. 
     The downhole assembly of the present invention preferably includes a composite coiled tubing string attached to a bottom hole assembly. Various embodiments of the present invention provide a number of different constructions of the bottom hole assembly, each of which is used for a downhole operation in one of many different types of wells including a new well, an extended reach well, extending an existing well, a sidetracked well, a deviated borehole, and other types of boreholes. It should be appreciated that the bottom hole assembly may be only a downhole tool for performing an operation downhole in the well. Often the downhole operation relates to the drilling and completing of a pay zone in the well but the present invention is not limited to such operations. The embodiments of the present invention provide a plurality of methods for using the system of the present invention. It is to be fully recognized that the different teachings of the embodiments discussed below may be employed separately or in any suitable combination to produce desired results in a downhole operation. In particular the present system may be used in practically any type of downhole operation. Reference to “up” or “down” are made for purposes of ease of description with “up” meaning towards the surface and “down” meaning towards the bottom of the borehole. Use of the term “coupled” herein means a direct or indirect connection that can be permanent or selectively connectable. Thus, if a first device “couples” to a second device, that connection may be through a direct connection, or through an indirect connection via other devices and/or connections. 
     Referring initially to FIG. 1A, there is shown an exemplary operating environment for the disconnect assembly  10  of the present invention. At the surface, an operational system  12  includes a power supply  14 , a surface processor  16 , and a coiled tubing spool  18 . An injector head unit  20  feeds and directs coiled tubing  30  from the spool  18  into the well  22 . The downhole assembly  24  extending into the well  22  includes the coiled tubing string  26  and a bottom hole assembly  28 . The bottom hole assembly  28  is shown attached to the lower end of composite coiled tubing string  26  and extending into a deviated or horizontal borehole  32 . The lower end of the tubing string  26  may be connected to the bottom hole assembly  28  by a disconnect assembly  10   a.    
     Although the coiled tubing  30  is preferably composite coiled tubing, hereinafter described, it should be appreciated that the present invention is not limited to composite coiled tubing and may be steel coiled tubing with electrical conductors mounted on the steel coiled tubing. The composite tubing string  26  may include a plurality of lengths  30   a  and  30   b  of composite coiled tubing. The adjacent ends of the lengths  30   a  and  30   b  of coiled tubing  30  may be connected by the disconnect assembly  10   b  of the present invention. In the preferred embodiment described, disconnect assembly  10   c  connects one set of components making up the bottom hole assembly with another set of components of the bottom hole assembly  28 . It should be appreciated that this embodiment is described for explanatory purposes and that the present invention is not limited to a particular location in the downhole assembly. If a disconnect assembly  10  is not used to connect lengths  30   a ,  30   b  of composite coiled tubing  30  or to connect composite coiled tubing  30  to bottom hole assembly  28 , one type of alternative connector is disclosed in U.S. patent application Ser. No. 09/534,685 filed Mar. 24, 2000 and entitled “Coiled Tubing Connector.” It should be appreciated that the disconnect assembly  10  may be used in conjunction with the connector disclosed in the above identified application. 
     Referring now to FIG. 1B, there is shown one type of bottom hole assembly  28  made up of various components. Bottom hole assembly  28  has a first group of components including a bit  34  mounted on a drive shaft  36 , a bearing assembly  38 , a steering assembly  40  including an electronics section  42  and preferably a near bit orientation sensor  44  having an inclinometer and magnetometer, an upper constant velocity (CV) sub  46 , a power section  48  with wire subs, a check valve  50 , and a resistivity sub  52 . The bottom hole assembly  28  also has a second group of components including a sensor sub  54  with an orientation package, additional sensors and downhole control devices, a propulsion system  56  including a lower tractor back pressure control module  58 , a lower tension/compression sub  60 , pressure measurement sub  62 , an upper tractor back pressure control module  64 , an upper tension/compression sub  66 , and a supervisory sub  68 . 
     Disconnect  10  releasably connects the first and second groups of components of bottom hole assembly  28  and in particular releasably connects the bit  34 , steering assembly  40  and power section  48  with the propulsion system  56 . If a disconnect  10  is not used to connect composite coiled tubing  30  to bottom hole assembly  28 , one type of alternative connector is a flapper ball drop release  70 . See for example U.S. patent application Ser. No. 09/504,569 filed Feb. 15, 2000 and entitled “Recirculatable Ball-Drop Release Device for Lateral Oilwell Drilling Applications”, hereby incorporated herein by reference. 
     It should be appreciated that other tools may be included in the bottom hole assembly  10 . The tools making up the bottom hole assembly  10  will vary depending on the operation to be conducted downhole. It should be appreciated that the present invention is not limited to a particular bottom hole assembly and other alternative assemblies may also be used. Further it should be appreciated that the disconnect  10  may be used to connect any two groups of components making up the bottom hole assembly  28 . 
     Referring now to FIG. 2, the coiled tubing  30  making up the string  26  preferably includes a tube made of a composite material and includes an impermeable fluid liner  72 , a layer of glass fiber  74 , a plurality of conductors around the liner  72  and glass layer  74  including power conductors  76 ,  78  embedded in a protective resin  80 , a plurality of load carrying layers  82  forming a carbon fiber matrix, a wear layer  84 , a layer of polyvinylidene fluoride (PVDF)  86 , and an outer wear layer  88  formed of glass fibers. Impermeable fluid liner  72  is an inner tube preferably made of a polymer, such as polyvinyl chloride or polyethylene, or any other material which can withstand the chemicals in the drilling fluids to be used in drilling the well  22  and the temperatures to be encountered downhole. The inner liner  72  is impermeable to fluids and thereby isolates the load carrying layers  74  from the drilling fluids passing through the flow bore  89  of liner  72 . The load carrying layers  82  are preferably a resin fiber having a sufficient number of layers to sustain the required load of the string  26  suspended in fluid, including the weight of the string  26  and bottom hole assembly  28 . The fibers of load carrying layers  82  are preferably wound into a thermal setting or curable resin. Load carrying fibers  82  provide the mechanical properties of the string  26 . The wear layer  84  is preferably the outermost load carrying layer  82  and may be a sacrificial layer. Although only one wear layer  84  is shown, there may be additional wear layers as required. The PVDF layer  86  is impermeable to fluids and isolates the load carrying layers  82 . The outer wear layer  88  is preferably the outermost layer of fiber and is a sacrificial layer. Composite coiled tubing is also described in U.S. patent application Ser. No. 09/081,961 filed May 20, 1998 and entitled “Well System”, hereby incorporated herein by reference. 
     The power conductors  76 ,  78  housed within the composite tubing wall extend along the entire length of composite coiled tubing string  26  and are connected to bottom hole assembly  28 . Conductors  76 ,  78  are connected to power supply  14  and to surface processor  16 . Their downhole ends are connected to an electronics package in the bottom hole assembly  28 . The conductors  76 ,  78  provide both power and command signals to the bottom hole assembly  28 . Further data may also be communicated through the conductors  76 ,  78 . 
     Referring now to FIGS. 3 and 4, there is shown a disconnect assembly  10  having an inner housing  90  and an outer housing  92 . Inner housing  90  includes a threaded connection  94  for threaded engagement with the first grouping of BHA components and an electrical connection  96  for electrical connection to the first grouping of BHA components. A plurality of flow paths  95 , best shown in FIG. 4, extend through the longitudinal length of inner housing  90  for the flow of drilling fluids. Outer housing  92  includes a threaded connection  98  for threaded engagement with the second grouping of BHA components and an electrical connection  100  for electrical connection to the second grouping of BHA components. The electrical connections are electrically connected to conductors  76 ,  78  in the wall of the composite tubing string  26  with conductors passing through passageways  101  extending longitudinally through the wall  128  of inner housing  90 . Outer housing  92  includes uphole and downhole sections  92   a ,  92   b  threadingly connected at  102  to facilitate the assembly of housing  92  with inner housing  90 . Outer housing  92  also has a pair of longitudinally spaced internal circumferential grooves  91 ,  93  on its inside diameter. Internal locking grooves  91 ,  93  have a rounded cross-section providing a camming surface. Inner housing  90  includes an upper fishing neck  106  having an electrical connector  108  making electrical connection with an electrical connector  112  mounted in the uphole section  92   b  of outer housing  92 . Inner housing  90  releasably couples with outer housing  92 , preferably via involute splines  104 . Splines  104  transmit any torque transferred between inner and outer housings  90 ,  92 . 
     Referring now to FIG. 5, inner housing  90  further includes an axially extending longitudinal cavity  110  with a reduced diameter uphole portion forming a bore  114 . The uphole end of the bore  114  terminates at a transverse aperture  116  in alignment with plugged ports  118   a ,  118   b  in outer housing  92 . The uphole bore  114  forms a downwardly facing annular shoulder  122 . A medial reduced diameter portion of cavity  110  forms a reduced diameter cavity  120  disposed between bore  114  and the remainder  124  of cavity  110 . Reduced diameter cavity  120  forms an annular shoulder  121 . A plurality of transverse bores  126  extend from bore  114  through the outer wall  128  of inner housing  90 . 
     A release assembly  130  is disposed within inner housing  90  and includes a plurality of locking pins  132  engaging a release shaft  134 . Locking pins  132  are disposed in inner housing  90  by retainers  136  threaded into transverse bores  126 . Release shaft  134  has its uphole end slidably received in reduced diameter bore  114  and its downhole end connected by a connection  135 , hereinafter described, to a drive train  140  attached to an electric motor  138  housed in cavity  110 , hereinafter described. Release shaft  134  has a longitudinally extending, elongated slot  142  therein which receives a guide pin  144  mounted in the wall  128  of inner housing  90  to prevent relative rotation between release assembly  130  and inner housing  90 . 
     Each locking pin  132  has an inner and an outer end  146  and  148 , respectively, and extends radially from release shaft  134  towards outer housing  92 , best shown in FIG.  4 . Release shaft  134  further comprises external circumferential release grooves  150  alignable with the inner pin ends  146  in the release position shown in FIG. 6 whereby locking pins  132  are received in release grooves  150 . External release grooves  150  have a cross-section with a generally flat bottom and tapered sides. As shown in FIGS. 3-5, inner pin ends  146  are not aligned with external circumferential release grooves  150  in the connected position. 
     Still referring to FIGS. 3-5,  5 A, and  5 B release assembly  130  further includes a lead screw sleeve  152  connected to release shaft  134  by a universal joint  154 . Universal joint  154  allows rotational movement between release shaft  134  and lead screw sleeve  152  to accommodate bending of the downhole assembly  24 . Universal joint  154  is a coupling of preferably three pieces, namely release shaft  134 , segment  220 , and lead screw sleeve  152 . Release shaft  134  has aperture  156 , lead screw sleeve  152  has aperture  160  and segment  220  has apertures  225  and  230 . When universal joint  154  is assembled (see FIG.  5 B), aperture  156  and aperture  230  are aligned, and aperture  160  aperture  225  are aligned. Pins  164  are inserted into the apertures to prevent separation of release shaft  134  and lead screw sleeve  152 . 
     The drive train  140  is supported within cavity  110  by a support sleeve  166  having a central aperture  168  therethrough with an annular restrictive flange  172  in the central portion thereof forming a bushing  174  therethrough for receiving the drive train  140 . Seals  167 ,  169  are disposed between inner housing  90  and support sleeve  166 . The drive train  140  includes a lead screw  170  threadingly received at one end by lead screw sleeve  152 . Lead screw  170  includes a central blind bore  176  and an external annular bearing flange  178  engaging a bearing washer  180  disposed between annular restrictive flange  172  and annular bearing flange  178 . 
     A converter  182  is coupled to drive shaft  184  of motor  138  at its downhole end and to lead screw  170  at its uphole end via a pin  186 . Converter  182  rotates within the bushing  174  of the support sleeve  166 . Seals  194  are disposed between bushing  174  and lead screw  170 . 
     Support sleeve  166  has a flanged end  190 . Flanged end  190  engages the annular shoulder  121 . A pressure compensator piston  192  is disposed about lead screw sleeve  152  and within support sleeve  166 . A seal  196  is disposed between lead screw sleeve  152  and pressure compensator piston  192 , and seal  198  is disposed between piston  192  and support sleeve  166 . 
     A lubricating fluid fills the space around release assembly  130  and drive train  140  including bore  114 , lead screw sleeve  152 , and central aperture  168 . As the release assembly  130  and drive train  140  move, the lubricating fluid must be allowed to flow and not inhibit the movement of the release assembly  130  or drive train  140 . Therefore an uphole pressure release port  200  is disposed adjacent the uphole end of release shaft  134  in transverse aperture  116  and a downhole pressure release ports  202  are disposed in central blind bore  176 . 
     Electrical motor  138  is coupled via cap screws  204  to a retainer sleeve  206  mounted on an electronics package  208  disposed downhole of motor  138  in cavity  110 . Electric motor  138  is connected through conductors  76 ,  78  to the surface  212  and can be commanded from the surface  212  to rotate in either clockwise or counterclockwise direction, i.e., either the release direction or the connect direction. A retainer  210  is threaded into the downhole end of cavity  110  to mount motor  138  and the electronics package  208  in cavity  110  of inner housing  90 . Male electrical connector  96  extends through the retainer  210  connecting the electronics package  208  with the bottom hole assembly  28  threadingly connected to the downhole end  94  of inner housing  90 . As best shown in FIG. 4, wire ways  101  extend longitudinally through the wall  128  of inner housing  90  to maintain an electrical connection from the surface  212  through the disconnect assembly  10  to the bottom hole assembly  28 . 
     In operation, the electric motor  138  is actuated from the surface  212  causing drive shaft  184  to rotate drive train  140 . As drive train  140  rotates, lead screw  170  rotates within lead screw sleeve  152 . Depending upon the direction of rotation of the electric motor  138 , the connection  135  causes release shaft  134  to either reciprocate towards or away from motor  138 . Thus, upon command from the surface, electric motor  138  moves release shaft  134  either to the connecting position shown in FIGS. 3-5 or the releasing and released positions shown in FIGS. 6-7. 
     One or more of release shaft  134 , locking pins  132 , internal circumferential grooves  91 ,  93 , and/or external circumferential grooves  150  comprise a lock  214  that is capable of releasably locking outer housing  92 , connected to the second grouping of BHA components, to inner housing  90 , connected to a first grouping of BHA components, while connection  146  serves a means for engaging and disengaging lock  214 . 
     In the connected position as shown in FIGS. 3-5, locking pins  132  are aligned and disposed within internal circumferential grooves  91 ,  93  of outer housing  92  and carry the axial load between outer housing  92  and inner housing  90 . Locking pins  132  are maintained in the locked position by release shaft  134 . 
     FIG. 6 shows disconnect assembly  10  in the released position. Upon command from the surface, electric motor  138  actuates, thereby actuating and rotating lead screw  170 . As lead screw  170  rotates within screw sleeve  152 , release shaft  134  moves axially downhole by virtue of the threaded engagement between lead screw  170  and lead screw sleeve  152  forming connection  135 . Thrust of lead screw  170  is taken by bearing flange  178  and bearing washer  180 . As previously stated, guide pin  144  and longitudinally elongated slot  142  prevent relative rotation between shaft  134  and inner housing  90  causing release shaft  134  to move axially, but prevent release shaft  134  from rotating. As shown in FIG. 6, lead screw  170  has moved release shaft  134  axially such that external circumferential grooves  150  are now aligned with locking pins  132 . 
     Still referring to FIG. 6, disconnect assembly  10  is shown in the released position after a command signal has been sent to electric motor  138  to disengage disconnect assembly  10 . Actuation of motor  138  preferably occurs directly from the surface  212 , preferably via conductors  76 ,  78  extending through the wall of composite coiled tubing string  26 . For example, the operator can send a command signal to electric motor  138  directing motor  138  to disengage disconnect assembly  10 . If there are multiple disconnect assemblies  10  used in downhole assembly  24 , each disconnect assembly  10  is assigned a unique command address. The command from the surface  212  includes the command address of the disconnect assembly  10  to be disconnected. If the address of a particular disconnect assembly  10  matches the command signals, electric motor  138  of that disconnect assembly  10  is activated and rotates lead screw  170 . When lead screw  170  is actuated by electric motor  138  in response to a disengage command, lead screw  170  axially pulls release shaft  134  toward electric motor  138 . Once external circumferential grooves  150  align with locking pins  132 , the released position of FIG. 6 occurs and pins  132  can move radially into external circumferential grooves  150 . After pins  132  have moved out of internal circumferential grooves  91 ,  93  and into external circumferential grooves  150 , disconnect assembly  10  is in the released a position and outer housing  92  is ready to be separated from inner housing  90  and pulled out of the hole while the inner housing  90  with the first grouping of BHA components remains in the borehole. 
     FIG. 7 shows outer housing  92  and inner housing  90  in the disconnected position. As shown, pins  132  have moved into external circumferential grooves  150  and outer housing  92  has been disconnected from inner housing  90 . Outer housing  92  can then be pulled out of the borehole, leaving fishing neck  106  exposed uphole for a fishing operation to retrieve that portion of the BHA stuck in the borehole. 
     On occasions, outer housing  92  cannot be separated from inner housing  90  after disconnect assembly  10  being activated and placed in the released positions. This indicates that the stuck point for the downhole assembly  26  is up-hole from disconnect assembly  10 . The present invention allows a command signal to be sent to electric motor  138  to turn lead screw  170  in the opposite direction, i.e., in the direction to push release shaft  134  axially away from electric motor  138 . Release shaft  134  will then be moved axially until locking pins  132  are cammed radially outwards and outer ends  148  engage internal circumferential grooves  91 ,  93 . This locks the tool for normal operation, as shown in FIGS. 3-5. The operator can now choose to activate another disconnect assembly  10  above the one just being activated to attempt a release further uphole. 
     While preferred embodiments of this invention have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit or teaching of this invention. The embodiments described herein are exemplary only and are not limiting. Many variations and modifications of the system and apparatus are possible and are within the scope of the invention. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims.