Abstract:
A cable release apparatus includes a housing and latch mounted at one end of the housing. The latch has a central opening and a plurality of projecting members extending into the housing. A releasable connector is mounted inside the housing. An actuator has one end disposed in the central opening in the latch and another end in contact with the releasable connector. The actuator is movable between a first position prior to activation of the releaseable connector and a second position wherein the releasable connector is activated. Prior to activation of the releasable connector, the latch is held in place by an interference fit between the projecting members and the housing. When the releasable connector is activated, the projecting members are deflected by applying tension to the latch, thereby releasing the latch from the housing.

Description:
FIELD OF THE INVENTION 
   The invention relates to a downhole electrically controlled release device. The release device is adapted for releasing downhole apparatus such as a conveyance from a downhole tool or a portion of a tool string. 
   BACKGROUND 
   Various devices and methods have been provided in the oilfield service industry for releasing downhole apparatus such as wireline from the conveyance head and tools. Traditionally, such apparatus have relied upon mechanical weakpoints. U.S. Pat. No. 6,431,269, incorporated herein by reference, assigned to Schlumberger Technology Corporation addressed disadvantages and shortcomings of the prior art devices and methods. 
   Therefore, it is a desire to provide a release device that overcomes deficiencies of the prior art devices. It is a further desire, to provide a release device that provides additional benefits. 
   SUMMARY OF THE INVENTION 
   An embodiment of the present invention provide a device for releasably connecting downhole apparatus. The device comprises a housing; a latch mounted at one end of the housing having a central opening and a plurality of projecting members extending into the housing; an actuator having a first end disposed in the central opening; and a shape memory alloy member functionally connected to the actuator in a manner such that the actuator is held in a first position prior to activation of the shape memory alloy member and the actuator is moveable to a second position after the shape memory alloy member is activated. The latch is held in connection with the housing by an interference fit between the projecting members and the housing when the actuator is in the first position. The latch is disengaged from the housing when the actuator is in the second position. 
   Another embodiment of the present invention provides a device for releasably connecting a wireline to a downhole tool. In this embodiment, the device comprises a housing; a latch mounted at one end of the housing, the latch having a central opening and a plurality of projecting members extending into the housing; an actuator having a first end disposed in the central opening; and a shape memory alloy member positioned in parallel with the load path of the actuator and functionally connected to the actuator in a manner such that the actuator is held in a first position prior to activation of the shape memory alloy member and the actuator is moveable to a second position after the shape memory alloy member is activated. The projecting members have inner surfaces for engagement of an outer surface of the actuator, the inner surfaces of the projecting members and the outer surface of the actuator being substantially parallel to one another and the longitudinal axis of the actuator. The latch is held in connection with the housing by an interference fit between the projecting members and the housing when the actuator is in the first position, and wherein the latch is disengaged from the housing when the actuator is in the second position. 
   Another embodiment of the present invention provides a device for releasably connecting a conveyance to a downhole tool. In this embodiment, the device comprises a housing; a latch mounted at one end of the housing, the latch having a central opening and a plurality of projecting members extending into the housing; an actuator having a first end disposed in the central opening; and a releasable connector functionally connected to the actuator in a manner such that the actuator is held in a first position prior to activation of the releasable connector and the actuator is moveable to a second position after the releasable connector is activated. The projecting members have inner surfaces for engagement of an outer surface of the actuator, the inner surfaces of the projecting members and the outer surface of the actuator being substantially parallel to one another and the longitudinal axis of the actuator. The latch is held in connection with the housing by an interference fit between the projecting members and the housing when the actuator is in the first position, and wherein the latch is disengaged from the housing when the actuator is in the second position. 
   The foregoing has outlined the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other features and aspects of the present invention will be best understood with reference to the following detailed description of a specific embodiment of the invention, when read in conjunction with the accompanying drawings, wherein: 
       FIG. 1  is a cross-sectional view of an embodiment of the electrically controlled release device of the present invention; 
       FIG. 2  is a cross-sectional view of the electrically controlled release device along the line  2 - 2  of  FIG. 1 ; 
       FIG. 3  is a cross-sectional view of another embodiment of the electrically controlled release device of the present invention; 
       FIG. 4  is a cross-sectional view of a conveyance head of the present invention; and 
       FIG. 5  is a cross-sectional view of a the present invention in a wellbore. 
   

   DETAILED DESCRIPTION 
   Refer now to the drawings wherein depicted elements are not necessarily shown to scale and wherein like or similar elements are designated by the same reference numeral through the several views. 
   As used herein, the terms “up” and “down”; “upper” and “lower”; and other like terms indicating relative positions to a given point or element are utilized to more clearly describe some elements of the embodiments of the invention. Commonly, these terms relate to a reference point as the surface from which drilling operations are initiated as being the top point and the total depth of the well being the lowest point. 
   The present invention provides an electrically controlled release device. It should be understood that the release device is equally applicable to releasing a conveyance from a downhole tool as it is to releasing a part of a tool string from the remainder of the tool string. However, for purposes of illustrating the principles of the release device, the release device will primarily be described as releasing a conveyance from a downhole tool. 
   The electrically controlled release device has two modes of operation. In the first mode of operation, the electrically controlled release device transmits the tension applied to the conveyance head (or tool head) by a conveyance to the downhole tools coupled to the conveyance head without releasing the conveyance from the conveyance head. In the second mode of operation, the electrically controlled device releases the conveyance from the conveyance head when a low tension is applied to the conveyance head. The electrically controlled release device can be activated to release the wireline cable regardless of the tensile load it is transmitting. 
     FIG. 1  is a cross-sectional view of an embodiment of the electrically controlled release device, generally denoted by the numeral  2 , of the present invention. Release device  2  includes an upper housing body  4  and a lower housing body  6 . Upper housing body  4  is coupled to lower housing body  6  by a threaded connection  8 , for example. An O-ring  7  provides a seal between upper housing body  4  and lower housing body  6 . Upper housing body  4  is provided with a central opening  10 , and lower housing body  6  is provided with a central chamber  12 . 
   A latch  14  is mounted on upper housing body  4 . Latch  14  has a latching head  16  and fingers  18  which extend from latching head  16 . Fingers  18  extend into central opening  10  of upper housing body  4 . Fingers  18  have wedge-shaped surfaces  20  which are adapted to engage with a wedge-shaped surface  22  in the inner wall of the upper housing body  4 . An O-ring  24  provides a seal between latching head  16  and upper housing body  4 . 
   An actuator  26  is disposed within a central opening  28  in latch  14 . A lower portion  30  of actuator  26  extends through upper housing body  4  into the central chamber  12  of lower housing body  6 . Actuator  26  has an outer surface  100  substantially parallel to the longitudinal axis of actuator  26 . Actuator surface  100  is adapted for engagement with the inner surface  102  of fingers  18 . Inner finger surfaces  102  are substantially parallel to the longitudinal axis of actuator  26  and actuator outer surface  100 . Co-owned U.S. Pat. No. 6,431,269 incorporated by reference herein, teaches that if surface  100  was parallel to the axis of release device  2  the frictional forces would prevent actuator  26  from moving when release device  2  was transmitting tension. The present invention teaches that actuator surface  100  being substantially parallel to the axis of release device  2  provides benefits and addresses disadvantages recognized in the prior release technology. 
   A first benefit of the inventive parallel actuator surface  100  and finger surfaces  102  is that the assembly of release device  2  is facilitated because the elements may be moved relative to each other to allow for tolerance. In the prior art invention, more precise control during assembly was required to ensure that loads would not be inadvertently translated to releasable connector  36 . An additional benefit is that the release device of the present invention provides a safety feature to prevent accidental release of the carried tool at the surface. In the present invention release device  2  tends to self-lock when tension is applied to it. The weight of the tool string, when hanging in the derrick, creates sufficient tension to keep actuator  26  from moving even if release device  2  has been triggered to release. When release device  2  is lowered into the wellbore, the well pressure acts on latch  14  as a result of the pressure differential between the latch and the housing forcing the latch back into the housing, relieving any tension that may be present. In effect, the surface safety release is turned off when release device  2  is lowered in the wellbore. 
   Release device  2  includes a releasable connector  36  in functional connection with actuator  26  for triggering the device from mode  1  operation to mode  2 . Releasable connector  36  is illustrated as a split bobbin assembly disposed in central chamber  12  of lower housing body  6 . As shown in  FIG. 2 , split bobbin assembly  36  includes quartered bobbin pieces  44  and a resistive heater  46  arranged in a ring structure. Bobbin pieces  44  are preferably made of a heat-resistant material. A metal spring or coil  45  is tightly wound around bobbin pieces  44  and resistive heater  46  and soldered in place, as shown at solder joint  47 . In this way, bobbin pieces  44  are held together. In one embodiment, metal spring  45  is made of a heat-resistant conductive material such as beryllium-nickel alloy. As will be further discussed below, the purpose of resistive heater  46  is to melt the solder joint  47  so that the metal spring  45  expands. When metal spring  45  expands, bobbin pieces  44  separate. 
   Returning to  FIG. 1 , lower housing body  6  includes two apertures  48 ,  50  for receiving insulating electrical feed-throughs  52 ,  54 , respectively. O-rings  49 ,  51  provide seals between lower housing body  6 , and feed-throughs  52 ,  54  respectively. Electrical feed-throughs  52 ,  54  provide the electrical current needed to power resistive heater  46  (shown in  FIG. 2 ). A plate  38  made of insulating material is positioned between split bobbin assembly  36  and lower housing body  6 . A nose portion  40  of actuator  26  is in contact with split bobbin assembly  36 . A biasing mechanism  42 , shown as a spring, disposed between actuator  26  and upper housing body  4  applies a biasing force to actuator  26 , such that nose portion  40  of actuator  26  is held against bobbin pieces  44  (shown in  FIG. 2 ) of split bobbin assembly  36 . 
   Release device  2  has two modes of operation. In mode one, the release device transmits tension applied to latch  14  without fingers  18  separating from upper housing body  4 . In mode two, fingers  18  can be separated from upper housing body  4  with a small tension applied to latch  14 . 
   In mode one, a tensile load may be applied to latch  14  through surface  55  of latch  14 . The tension applied to latch  14  is transmitted to upper housing body  4  through the interference fit of fingers  18  and housing  4  at surfaces  20 ,  22 . The wedging effect of surfaces  20 ,  22  tends to cause fingers  18  to deflect, causing a compressive force to be applied to actuator  26  at surfaces  100 ,  102 . This compressive force in addition to the force from the pressure differential between the wellbore and the housing maintains actuator  26  against split bobbin assembly  36 . This compressive force is reacted by split bobbin assembly  36  and lower housing  6  and thus, latch  14  in connection with upper housing  4 . As long as this compressive force is reacted, and actuator  26  remains in the first position, fingers  18  remain in connection with upper housing  4  via the interference fit. 
   In mode two, fingers  18  can be separated from upper housing body  4  with a small tension applied to latch  14 . To switch release device  2  from mode one to mode two, a command is sent to a switching circuit (not shown) to power resistive heater  46  (shown in  FIG. 2 ). The switching circuit (not shown) directs current to resistive heater  46  (shown in  FIG. 2 ) through electrical feed-throughs  52 ,  54 . Resistive heater  46  (shown in  FIG. 2 ) melts solder joint  47  in metal spring  45 , as previously described, thus allowing metal spring  45  to expand and bobbin pieces  44  to separate. The force which causes actuator  26  to move downward is provided by the compressive forces and biasing mechanism  42 . In this state, the compressive loop described above can no longer be reacted and actuator  26  is moved to a second position. A small tension applied to upper housing body  4  will separate fingers  18  from upper housing body  4 . Once fingers  18  disengage from upper housing body  4 , latch  14  can be removed from release device  2 . 
   Desirably, the seal provided by O-ring seal  35  is broken when bobbin pieces  44  separate and as actuator  26  moves downward. This allows release device  2  to be flooded with wellbore fluid so the pressure is equalized between the interior and the exterior of release device  2 . This is necessary because the interior of release device  2  is initially at atmospheric pressure and release device  2  may need to be separated at ambient external pressures as high as 20,000 psi. If release device  2  were not pressure balanced, the pressure forces holding latch  14  and upper housing body  4  would be too great to allow fingers  18  to disengage from upper housing body  4 . The flooding of release device  2  also provides additional force for moving actuator  26  downward. 
     FIG. 3  is a cross-sectional view of another embodiment of the electrically controlled release device, generally denoted by the numeral  2 , of the present invention. Relief device  2  may include substantially parallel actuator outer surface  100  and finger inner surfaces  102  as illustrated or may include the wedged shaped actuator outer surface and finger inner surfaces as described in U.S. Pat. No. 6,431,269, which has been incorporated herein by reference. 
   As illustrated, bobbin assembly type releasable connector  36  of  FIG. 1  has been eliminated and replaced with a sleeve assembly type releasable connector  104  functionally connected to actuator  26 . This embodiment of the present invention isolates the transfer of any potential load to the releasable connector which increases the longevity of release device  2 . Additionally, in installations wherein the tool string may include gun strings or other shock producing tools, a longer string may be utilized than with previous release devices. 
   Sleeve assembly  104  includes an expandable sleeve  106 , a heater  108  and a releasable stop  110 . Sleeve  106  of the present embodiment is a shaped memory alloy (SMA) that when heated elongates. Sleeve  106  is positioned in parallel with biasing mechanism  42  and the load path of actuator  26 . Sleeve  106  is positioned between a lip  112  of housing  4  and a shelf  114  extending from actuator  26  in a manner such that when sleeve  106  is heated and elongates it urges actuator  26  downward. A stop  110  is positioned to maintain actuator  26  in a set and non-moving position in mode  1  operation. Releasable stop  110  may be, but is not limited to, a shear pins, a Truarc ring, a rupture disc, or a reusable mechanism such as a collet latch or press fit washer. Heater  108  is positioned in functional connection with sleeve  106 . Operation of, and functional connections with, heater  108  are not provided herein as they are well known in the art and addressed in more detail in relation to  FIG. 1 . 
   In mode  1 , fingers  18  are maintained in engagement with housing  4  by actuator  26  which is held in place by attachment of latch  14  to housing  4  and releasable stop  110 . To release, heater  108  is activated heating sleeve  106  which elongates. The elongation of sleeve  106  results in breaking or separating releasable stop  110  releasing actuator  26  for movement. Biasing mechanism  42  will urge actuator  26  downward releasing fingers  18  from engagement with house  4 . The movement of actuator  26  breaks seal  35  equalizing the pressure inside and out of release device  2  facilitating the removal of latch  14  from housing  4 . 
     FIG. 4  is a cross-sectional view of a conveyance head  60 . It should be noted that conveyance head  60  is not shown in its entirety to avoid obscuring the invention. In operation, the lower end of conveyance head  60  would be coupled to a logging tool assembly (not shown). Conveyance head  60  includes an outer housing  62 . Release device  2  is mounted inside outer housing  62 . A fishing neck  66  is mounted at the upper end of outer housing  62 . Fishing neck  66  has a central bore  68  for receiving a shell  70 . The lower end of shell  70  is secured to latching head  16  of release device  2 . A housing  73  is attached to the upper end of shell  70 . Inside housing  73  is a rope socket  72  which has an aperture  74  for receiving a wireline cable type conveyance (not shown). A conductor sleeve  76  is mounted inside shell  70 . Conductor sleeve  76  connects the terminal ends of conductors in the wireline cable (not shown) to a connector  78  in shell  70 . Connector  78  is in turn connected to the rest of the tool by electrical wiring  80 . In this way, signals can be transmitted to and from the surface through the wireline cable (not shown). 
     FIG. 5  is a schematic of an embodiment of the present invention in a wellbore in which the device is used to release a conveyance head  60  from a downhole tool assembly  64 . Conveyance head  60  is suspended in a wellbore  82  on the end of a conveyance  84 . Conveyance  84  is illustrated as a wireline cable, however, it should be recognized that other types of conveyances including, but not limited to, slick lines and coiled and non-coiled tubulars may be utilized. Wireline cable  84  is fed from a surface winch  86 . In operation, tension from surface winch  86  is transmitted down to conveyance head  60  via wireline cable  84 . The tension transmitted to conveyance head  60  is then transmitted to the downhole tool assembly  64  attached to conveyance head  60  through release device  2  ( FIGS. 1 and 2 ) in conveyance head  60 . During normal operations, release device  2  in conveyance head  60  is in mode one in which it will transmit high tensions without separating. When desired, release device  2  in conveyance head  60  is actuated to mode two and will separate with only a small tensile force applied to it. 
   From the foregoing detailed description of specific embodiments of the invention, it should be apparent that an electrically controlled release device that is novel and unobvious has been disclosed. Although specific embodiments of the invention have been disclosed herein in some detail, this has been done solely for the purposes of describing various features and aspects of the invention, and is not intended to be limiting with respect to the scope of the invention. It is contemplated that various substitutions, alterations, and/or modifications, including but not limited to those implementation variations which may have been suggested herein, may be made to the disclosed embodiments without departing from the spirit and scope of the invention as defined by the appended claims which follow.