Abstract:
A well tool for applying a pulling or a pushing force to an object in an interior of a well bore comprising: a) an inner member comprising a first elongated member, a second elongated member and an actuation means axially interconnecting the first elongated member and the second elongated member; b) an outer elongated member longitudinally moveably engaged with the inner member; c) a first seal defined between the first elongated member and the outer elongated member; d) a second seal defined between the second elongated member and the outer elongated member; e) a first piston area defined at a first end portion of the outer elongated member between an outer diameter of the outer elongated member and a sealed outer diameter of the first elongated member; f) a second piston area defined at a second end portion of the outer elongated member between the outer diameter of the outer elongated member and a sealed outer diameter of the second elongated member; and g) a sealed chamber defined between the first seal and the second seal, the sealed chamber including a fluid at a fluid pressure; wherein operation of the actuation means axially reversibly moves the outer elongated member relative the inner member while the fluid pressure remains constant; and wherein the first piston area and the second piston area are substantially equal and external pressure acting on these two piston areas, generates two opposing forces substantially balanced during relative movement.

Description:
PRIORITY CLAIM 
     This is a U.S. national stage of application No. PCT/CA2006/001114, filed on 7 Jul. 2006. Priority is claimed on the following application: Country: US, application Ser. No.: 11/181,592, Filed: 14 Jul. 2005; the content of which is incorporated here by reference. 
     FIELD OF THE INVENTION 
     This invention relates to equipment for generating a force in a wellbore and more particularly but not limited to setting and retrieving tools for use in oil and gas wells. 
     BACKGROUND OF THE INVENTION 
     The structure of a wellbore of an oil or gas well generally consists of an outer production casing and an inner production tubing installed inside the production casing. The production tubing extends from the surface to the required depth in the wellbore for production of the oil or gas. Various tools such as plugs, chokes, safety valves, check valves, etc. can be placed in landing nipples in the production tubing to allow for different production operations or the downhole control of fluid flow. Also, tools like bridge plugs, packers and flow control equipment are placed in the production casing to control production or stimulation operations. Force generating tools are needed both to exert a pushing force to set tools in the production tubing or casing and to provide a pulling force to retrieve these tools. It is preferable to have the force generating tools wellbore pressure balanced so that the same force may be applied both in pulling and in pushing operations, irrespective of the pressure in the wellbore. 
     A downhole force generator is disclosed in U.S. Pat. No. 6,199,628. A downhole force generator is disclosed in U.S. Pat. No. 5,070,941. A locator and setting tool is disclosed in Canadian Patent No. 2,170,711. These 3 patents describe virtually the same technology, in different variations. None of these prior art tools are pressure balanced to provide equal force in pulling and pushing operations. As detailed in the article published by Halliburton Energy Services in the June 1996 edition of the SPE Drilling &amp; Completion magazine, “Any pressure differential increases the available force with the DPU in tension and decreases the setting force in the extension mode. This is because (1) the DPU is sealed to the well pressure through redundant sealing elements maintaining internal parts at near-atmospheric pressure, and (2) the well pressure acts on the power rod&#39;s sealed diameter.” This is a disadvantage, especially in high-pressure wells. A high enough downhole pressure will render these tools unusable. Additionally, none of these tools provide a simple mechanical tool, particularly for the retrieving of downhole tools. 
     SUMMARY OF THE INVENTION 
     According to one broad aspect, the invention provides a well tool for applying a pulling or a pushing force to an object in an interior of a well bore comprising: a) a drive mandrel; b) an engaging mandrel; c) an actuation means; d) a housing sealing a portion of the drive mandrel and a portion of the engaging mandrel within an interior space, the drive mandrel and the engaging mandrel extending from opposite ends of the housing; e) a drive mandrel piston area defined at a drive mandrel end portion of the housing between an outside diameter of the housing and a sealed diameter of the drive mandrel; and f) an engaging mandrel piston area defined at an engaging mandrel end portion of the housing between the outside diameter of the housing and a sealed diameter of the engaging mandrel; wherein the actuation means is adapted to reversibly move the housing longitudinally relative to the drive mandrel and the engaging mandrel and wherein the drive mandrel piston area and the engaging mandrel piston area are substantially equal and external pressure acting on these two piston areas, generates two opposing forces that are substantially balanced during relative movement. 
     According to another broad aspect, the invention provides a well tool for applying a pulling or a pushing force to an object in an interior of a well bore comprising: a) an inner elongated member; b) an outer elongated member; c) a sealed interior defined between the inner elongated member and the outer elongated member; and d) an actuation means defined at least partially within the sealed interior; wherein the actuation means is adapted to reversibly move the outer elongated member longitudinally over the inner elongated member and wherein the inner elongated member and the outer elongated member are arranged such that a volume of the sealed interior occupied by the inner elongated member remains substantially constant as the inner elongated member and the outer elongated member move relative to each other. 
     According to a further broad aspect, the invention provides a well tool for applying a pulling or a pushing force to an object in an interior of a well bore comprising: a) an inner elongated member; b) an outer elongated member encircling an intermediate segment of and longitudinally moveably engaged with the inner elongated member; c) a screw component of the inner elongated member, the screw component being coupled for rotation about a longitudinal axis; and d) a threaded component of the outer elongated member engaged with the screw component; wherein rotation of the screw component reversibly moves the outer elongated member relative to the inner elongated member. 
     According to a still further broad aspect, the invention provides a well tool for applying a pulling or a pushing force to an object in an interior of a well bore comprising: a) an inner member comprising a first elongated member, a second elongated member and an actuation means axially interconnecting the first elongated member and the second elongated member; b) an outer elongated member longitudinally moveably engaged with the inner member; c) a first seal defined between the first elongated member and the outer elongated member; d) a second seal defined between the second elongated member and the outer elongated member; e) a first piston area defined at a first end portion of the outer elongated member between an outer diameter of the outer elongated member and a sealed outer diameter of the first elongated member; f) a second piston area defined at a second end portion of the outer elongated member between the outer diameter of the outer elongated member and a sealed outer diameter of the second elongated member; and g) a sealed chamber defined between the first seal and the second seal, the sealed chamber including a fluid at a fluid pressure; wherein operation of the actuation means axially reversibly moves the outer elongated member relative the inner member while the fluid pressure remains constant; and wherein the first piston area and the second piston area are substantially equal and external pressure acting on these two pistons areas, generates two opposing forces that are substantially balanced during relative movement. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred embodiments of the invention will now be described with reference to the attached drawings in which: 
         FIGS. 1A ,  1 B and  1 C are partial schematic cross-sectional views of a first embodiment of the invention; 
         FIGS. 2A ,  2 B and  2 C are detailed upper, middle and lower cross-sectional views, respectively, of the first embodiment of the invention in a first position; 
         FIGS. 3A ,  3 B and  3 C are detailed upper, middle and lower cross-sectional views, respectively, of the embodiment of  FIGS. 2A ,  2 B and  2 C in a second position; 
         FIGS. 4A ,  4 B and  4 C are detailed upper, middle and lower cross-sectional views, respectively, of the embodiment of  FIGS. 2A ,  2 B and  2 C in a third position; 
         FIGS. 5A ,  5 B and  5 C are detailed upper, middle and lower cross-sectional views, respectively, of a second embodiment of the invention; 
         FIGS. 6A ,  6 B and  6 C are detailed upper, middle and lower cross-sectional views, respectively, of a third embodiment of the invention; and 
         FIGS. 7A ,  7 B and  7 C are partial cross-sectional views of a forth embodiment of the invention in first, second and third positions, respectively. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1A  shows cross-sectional view of a simplified embodiment of the invention. A tool  10  has an inner elongated member which includes a drive mandrel  50 , a screw  62  and an engaging mandrel  66 . The engaging mandrel may be a setting or a retrieving mandrel. The drive mandrel  50  and the screw  62  are axially coupled for both rotational and longitudinal movement. The engaging mandrel  66  and the screw  62  are preferably coupled for longitudinal movement only. The cross-sectional area of the drive mandrel  50  is substantially equal to the cross-sectional area of the engaging mandrel  66 . 
     The tool  10  also includes an outer elongated member or main housing  64 . The outside diameter of the main housing  64  is preferably constant. Fixed to the interior of the main housing  64  is a threaded component or nut  58 . The nut  58  is threaded on the screw  62 . One end of the main housing  64  is sealed to the drive mandrel  50  by a seal  48 . The other end of the main housing  64  is sealed to the engaging mandrel  66  by a seal  70 . The sealed interior of the main housing  64  is preferably equalized with the wellbore pressure. The connection between the screw  62  and the nut  58  is not fluid tight, i.e. chambers  65  and  67  on either side of the nut  58  are enclosed by the main housing  64  and are in fluid communication through gaps between the screw  62  and nut  58  and/or channels milled on the outside of the nut  58 . 
     The drive mandrel  50  is coupled at its other end to a motor  24 . The motor  24  is contained within a motor housing  14 . A connector  12  is provided at the other end of the motor for electrically and mechanically connecting the tool  10 . Cap screws  44  are provided in a guide sleeve  38  formed at the end of the motor housing  14  which encircles the drive mandrel  50  and an electronics seal  46  is provided around the drive mandrel  50  which seals the guide sleeve to the mandrel  50  to protect the inside of the motor housing  14  from the environment. A guide housing extension  40  of the main housing  64  slidably encompasses a portion of the guide sleeve  38 . The cap screws  44  travel in slots in the guide housing extension  40  and prevent rotation of the main housing  64 . 
     In operation, the connector  12  is electrically and mechanically connected to a wireline. The motor  24  rotates the drive mandrel  50 . Rotation of the drive mandrel  50  causes the screw  62  to rotate. The main housing  64  is held against rotation so that rotation of the screw  62  causes the main housing  64  to move longitudinally over the inner elongated member. At all times, the volume of the drive mandrel entering/exiting the interior space is the same as the volume of the engaging mandrel exiting/entering the interior space so that the free volume, and therefore also the pressure, in the interior space remains constant. The seals  48  and  70 , define two hydraulic pistons between the outside diameter of the main housing  64  and the outside diameter of the drive mandrel  50  and the outside diameter of the engaging mandrel  66  respectively. The two piston areas, shown schematically in  FIGS. 1B and 1C , have the same area. Any outside well pressure P acting on these two hydraulic piston areas will create two equal opposing forces that cancel each other. The constant volume in the interior and the matched piston areas enable the same force to be applied by the tool in both the pushing and the pulling operations. The main housing  64  and/or the engaging mandrel  66  are coupled to engaging tools for setting or retrieving of downhole tools. 
     In greater detail,  FIGS. 2A to 4C  depict a well tool, in particular a wireline retrieving tool for applying a pulling force to an object in the interior of a wellbore. The wireline retrieving tool  110  is generally tubular in shape. A connector  112  is located at the proximal end of the wireline retrieving tool  110 . The proximal end is the upper or trailing end when the wireline retrieving tool  110  is inserted into a wellbore. The connector  112  allows for mechanical and electrical connection of the wireline retrieving tool  110  to a wireline. The connector  112  connects to a proximal end of a tubular electronics housing  114 . Seals  116  are provided at the interface between the connector  112  and the electronics housing  114  to seal the interior of the electronics housing  114  from the environment. The electronics housing  114  houses an electronics carrier  118 , a printed circuit board  120 , a digital positioning encoder  122  and a gear motor  124 . The electronics carrier provides mechanical support for the printed circuit board  120 . The connector  112  is connected to the printed circuit board  120  to provide power to the printed circuit board from the wireline. The printed circuit board  120  provides control for the operation of the digital positioning encoder  122  and the gear motor  124 . The digital positioning encoder  122  is connected at one end of the gear motor  124 . The digital positioning encoder  122  counts the rotation of the gear motor  124  to allow precise calculation and control of the movement of the distal end, i.e. lower or leading end, of the wireline retrieving tool  110 . 
     A distal end of the electronics housing  114  is connected to a guide sleeve  138 . The guide sleeve is generally tubular. Seals  116  are provided between the guide sleeve  138  and the electronics housing  114  to seal the interior from the environment. A drive mandrel  150  extends at least partially through the guide sleeve  138 . The drive mandrel  150  is generally an elongated solid member with a circular cross-section. The drive mandrel  150  is interconnected to the gear motor  124  through a spline adapter  130 . The spline adapter  130  interconnects the gear motor  124  to the drive mandrel  150  through axial splines so that rotation of an output of the gear motor  124  results in rotation of the drive mandrel  150  at the same speed. The spline adaptor  130  is threaded to the drive mandrel  150 . Set screws  136  hold the drive mandrel  150  in position relative to the spline adaptor  130 . 
     Thrust bearings  134  are provided at support ends of the spline adapter  130  to facilitate smooth rotation of the drive mandrel  150  relative to the guide sleeve and the electronics housing. A drive mandrel lock nut  132  is provided to retain the bearings  134  and the spline adaptor in the guide sleeve  138  and cap screws  128  are provided to fasten the gear motor to the distal end of the electronics housing  114 . 
     Cap screws  144  are provided at a distal end of the guide sleeve  138 . The heads of the cap screws  144  project outward from the surface of the guide sleeve  138 . An upper guide housing  140  slidably encompasses a portion of the guide sleeve  138 . Longitudinal slots are defined in the upper guide housing  140 . The cap screws  144  travel within the longitudinal slots in the upper guide housing  140  when the upper guide housing  140  slides relative to the guide sleeve  138 . The cap screws  144  rest against the ends of the longitudinal slots to retain the upper guide housing  140  in contact with the guide sleeve  138  at the limits of relative travel and prevent relative rotation between the guide housing  138  and the upper guide housing  140 . 
     A glide ring  142  is also provided adjacent the cap screws  144  between the guide sleeve  138  and the drive mandrel  150  to facilitate the smooth rotation of the drive mandrel  150 . An electronics seal  146  is provided around the drive mandrel  150  at the distal end of the guide sleeve  138 . The electronics seal  146  seals the electronic section from external contaminants and keeps it at atmospheric pressure. 
     The distal end of the upper guide housing  140  mates with a proximal end of an upper housing  152 . The upper housing  152  is also generally tubular. The upper guide housing  140  and the upper housing  152  are retained relative to one another by a threaded connection. An upper interior area seal  148  is provided at a proximal end of the upper housing  152  and seals the upper housing  152  to the drive mandrel  150 . The upper internal area seal  148  seals the interior of the upper housing  152 . The electronics seal  146  and the upper internal area seal  148  allow for rotation of the drive mandrel  150 . 
     A distal end of the upper housing  152  is coupled to a proximal end of an actuator housing  160 . The actuator housing  160  is generally tubular. An actuator nut  158  is non-rotatably held within the actuator housing  160 . An actuator screw  162  extends through the actuator nut  158 . The actuator screw  162  is coupled to a distal end of the drive mandrel  150 . The coupling is provided by an anti-rotational lug so that the actuator screw  162  rotates with the drive mandrel  150 . A drive mandrel retainer  154  is provided within the upper housing  152  which maintains the drive mandrel  150  in contact with the actuator screw  162 . Glide rings  156  are provided around the circumference of the drive mandrel retainer  154  to allow smooth rotation of the drive mandrel retainer  154  within the upper housing  152 . 
     Upper chambers  165 A and  165 B ( FIGS. 3B and 3C ) are defined within the upper housing  152  which accommodate the drive mandrel retainer  154  when the upper housing  152  moves longitudinally relative to the drive mandrel  150 . Upper chambers  165 A and  165 B are in permanent communication. 
     Seals  116  are provided at the interface of the upper housing  152  and the actuator housing  160  to protect the interior of the upper chambers from the environment. A bottom housing  164  connects to the distal end of the actuator housing  160 . Seals  116  are provided between bottom housing  164  and the actuator housing  160  to protect the interior from the environment. 
     The actuator screw  162  extends through the bottom housing  164 . The actuator nut  158  is engaged with the actuator screw  162  such that rotation of the actuator screw  162  moves the actuator nut  158  relative to the actuator screw  162 . Other screw components and threaded components may be utilized. 
     The distal end of the actuator screw  162  is coupled to a retrieving mandrel  166 . The retrieving mandrel  166  is generally an elongated solid member with a circular cross-section of substantially the same diameter as the drive mandrel  150 . The actuator screw  162  is coupled to the retrieving mandrel  166  by a retrieving mandrel retainer  168 . The proximal end of the retrieving mandrel  166  adjacent to the actuator screw  162  has a shoulder  177 . On either sides of the shoulder  177  are thrust bearings  134 . The thrust bearings  134  allow longitudinal movement of the actuator screw  162  to be transmitted to the retrieving mandrel  166  but rotational movement of the actuator  162  is not transmitted to the retrieving mandrel  166  such that retrieving mandrel  166  moves longitudinally but does not rotate. Glide rings  156  are positioned between the retrieving mandrel retainer  168  and the bottom housing  164  to allow smooth longitudinal and rotational movement of the retrieving mandrel retainer  168  relative to the bottom housing  164 . 
     Bottom chambers  167 A and  167 B ( FIGS. 3B and 3C ) are defined within the bottom housing  164  which accommodate the retrieving mandrel retainer  168  when the bottom housing  164  moves longitudinally relative to the retrieving mandrel  166 . The bottom chambers  167 A and  167 B are in permanent communication. 
     A distal end of the bottom housing  164  is coupled to a setting cone  174 . Seals  116  are provided between the bottom housing  164  and the setting cone  174 . A lower internal area seal  170  is provided between the setting cone  174  and the retrieving mandrel  166 . A lower secondary interior area seal  172  is provided between the bottom housing  164  and the retrieving mandrel  166 . The lower internal seal  170  provides a primary seal to seal the interior of the bottom housing  164  from the external environment. The lower secondary interior seal  172  provides a backup seal. 
     A slip cage  178  holds a set of slips  180  on the setting cone  174 . Cap screws  176  connect the slip cage  178  to the setting cone  174 . The slip cage  178  is moveable relative to the setting cone  174  by movement of the cap screws  176  in slots defined in the slip cage  178 . The slips  180  are biased inward by springs  182 . 
     A C-ring  190  is provided which sits in a circumferential recess in the retrieving mandrel  166 . The C-ring  190  sits inside a C-ring housing  186  which is connected to the setting cone  174  by cap screws  184 . The C-ring  190  is retained within the C-ring housing  186  by a C-ring retainer  192 . A segment of the production tubing or casing  188  is shown to facilitate the explanation of the operation of the wireline retrieving tool  110 . 
     The drive mandrel  150  and the retrieving mandrel  166  are of substantially the same diameter so that the volume of either mandrel entering the sealed interior defined by the upper housing  152 , the actuator housing  160 , and the bottom housing  164  is substantially the same as the volume of the other mandrel exiting the sealed interior so that the free volume within the sealed interior remains substantially constant. A hydraulic piston defined between the outside diameter of the upper housing  152  and the outside diameter of the drive mandrel  150  and a hydraulic piston defined between the outside diameter of the bottom housing  164  and the outside diameter of the retrieving mandrel  166  are equal in area. Any outside well pressure acting on these two hydraulic piston areas will create two equal opposing forces that cancel each other. This provides the same power availability for pushing and pulling. 
     The operation of the wireline retrieving tool  110  is explained with reference to  FIGS. 2A to 2C ,  3 A to  3 C and  4 A to  4 C which show the wireline retrieving tool  110  in three different positions. The same reference characters are used in all three figures to refer to the same elements. In operation, the wireline retrieving tool  110  is connected by connector  112  to a wireline, both electrically and mechanically. The wireline retrieving tool is lowered into a segment of the production tubing or casing  188  to a desired location. At that location, the gear motor  124  is operated via the printed circuit board  120 . The digital positioning encoder  122  counts the rotations of the gear motor  124  so that an exact position of the retrieving mandrel  166  can be obtained. Rotation of the gear motor  124  is translated to the drive mandrel  150  to provide rotation of the drive mandrel  150 . 
     In the initial position depicted in  FIGS. 2A to 2C , only chambers  165 A and  167 A are open. The drive mandrel  150  is coupled to the actuator screw  162  as noted above so that rotation of the drive mandrel  150  provides rotation of the actuator screw  162  at the same rate of rotation. Rotation of the actuator screw  162  moves the actuator nut  158  downward along the actuator screw  162  as seen in  FIGS. 3A to 3C . This opens up chambers  165 B and  167 B at the same rate that chambers  165 A and  167 A are closed. The movement of the actuator nut  158  in turn moves the upper guide housing  140 , the upper housing  152 , the actuator housing  160  and the bottom housing  164  downward. The bottom housing  164  in turn pushes the setting cone  174  downward. 
     The C-ring housing  186  is held against downward movement by the C-ring  190  seated in the recess on the retrieving mandrel  166 . This also holds the slips  180  stationary relative to the retrieving mandrel  166 . The setting cone  174  slides relative to the slips  180 . The setting cone  174  has a narrower end initially within the slips  180  and expands along a shoulder  181  to a wider section. As the shoulder  181  is forced through the slips  180 , the slips are moved outward, the springs  182  are compressed and the slips bite into the segment of production tubing or casing  188  and hold the slips stationary relative to the production tubing or casing  188  (see  FIGS. 3A to 3C ). Further rotation of the actuator screw  162  no longer moves the housing downwardly, instead, further rotation of the actuator screw  162  will force the expansion and release the C-ring  190  from the retrieving mandrel  166  and the proximal end of the wireline retrieving tool  110  moves upwardly to the upper limit of travel shown in  FIGS. 4A to 4C . In this final position, chambers  165 A and  167 A are completely closed and chambers  165 B and  167 B are completely open. 
     All of chambers  165 A,  165 B,  167 A and  167 B are in fluid communication through gaps between the actuator screw  162  and the actuator nut  158  and gaps between the coupling assemblies interconnecting the actuator screw  152  to the mandrels  150  and  166  and the housings  152  and  164 . The mandrels  150  and  166  have substantially the same cross section. As a result, the combined free volume of the chambers  165 A,  165 B,  167 A and  167 B remains substantially constant throughout the relative movement of the housings so that the pressure within the sealed interior of the tool  110  remains constant. Also, because the mandrels  150  and  166  have the same cross section, any outside well pressure acting on the two opposing hydraulic pistons defined by the outside diameters of the housings  152  and  164  and the outside diameters of the mandrels  150  and  166 , would generate two equal opposing forces that would cancel each other and would not affect the function of the tool in pushing or pulling operations. 
     In operation, a fishing tool is attached to the distal end of the wireline retrieving tool  110 . The further rotation of the actuator screw  162  pulls the fishing tool upward against the holding force of the slips against the segment of production tubing or casing  188 . Thus, the pulling force is not provided by the wireline but instead by the action of the retrieving mandrel  166  against the slips  180 . 
     To reset the tool, the actuator screw  162  is rotated in the opposite direction causing the upper guide housing  140 , the upper housing  152 , the actuator nut  158 , the actuator housing  160 , the bottom housing  164  and the setting cone  174  to move upward. The withdrawal of the shoulder  181  of the setting cone  174  from the slip  180  results in the springs  182  retracting the slips  180  from contact with the segment of production tubing or casing  188 . The wireline retrieving tool  110  can then be withdrawn from the production tubing or casing. Alternatively, if the object to be retrieved is not completely free, the wireline retrieving tool  110  can be partially withdrawn up the production tubing or casing  188  and reset to perform a second or other subsequent pulling operations in the same manner as described above. 
       FIGS. 5A to 5C  depicts a wireline setting tool  198 . The same reference characters are used in  FIGS. 5A to 5C  for the same components as identified in  FIGS. 2A to 4C . It can be seen that the only difference between the wireline retrieving tool  110  of  FIGS. 2A to 4C  and the wireline setting tool  198  of  FIGS. 5A to 5C  is the assembly at the distal end. In particular, the wireline setting tool  198  does not contain a slip assembly. Instead, a setting housing  194  is connected at the distal end of the bottom housing  164 . As with the wireline retrieving tool  110 , a lower internal area seal  170  seals against a mandrel, in this case a setting mandrel  169 , of substantially the same diameter as the upper interior seal  148  which seals against the drive mandrel  150 . A setting adapter  196  is fixed to the distal end of the setting mandrel  169 . A tool to be set is fixed to the end of the setting housing  194  and the setting adapter  196 . When the wireline setting tool  198  is actuated in the manner as described with regard to the wireline retrieving tool  110 , the housings  140 ,  152 ,  160 ,  164  and  194  move downward over the setting mandrel  169  and the force thus exerted is used to set a tool to be placed in the production tubing or casing (not shown). In  FIGS. 5A to 5C , the wireline setting tool  198  is shown with the actuator nut  158  in an intermediate position such that the housings are partly but not fully extended. 
     The tools depicted in  FIGS. 1A to 5C  are intended to be deployed by a wireline. A wireline is flexible and uses gravity to lower a tool into position. For horizontal or highly deviated wells, a wireline alone may not allow a tool to be properly positioned in the well. Instead coiled tubing with a wireline installed inside it, also known as stiff wireline, is used. Coiled tubing consists of a hollow tube that surrounds the wireline and can be used to push a tool into a horizontal well. Coiled tubing is typically relatively thin walled. As a result, to prevent the tubing from collapsing under well pressure and mechanical forces, it is necessary to allow pressurized completion fluids to flow through the coiled tubing and through the tool. 
       FIGS. 6A to 6C  depict an embodiment of a retrieving tool that has been adapted for use with coiled tubing.  FIGS. 6A to 6C  use the same reference characters that are used in  FIGS. 2A to 4C  for the same components.  FIGS. 6A to 6C  will be described only in respect to how they differ from  FIGS. 2A to 4C .  FIGS. 6A to 6C  depict a retrieving tool  200 . A flow path is defined through the retrieving tool  200  to allow fluid to flow through the coiled tubing as detailed in the following description. 
     At a proximal end of the retrieving tool  200  there is the connector  112  for connecting to a wireline as explained above.  FIG. 6A  depicts additional components at a proximal end of the connector  112 , not shown in  FIGS. 2A to 4C . In particular, an electrical contact sub  208  and a rubber boot  204  are shown as interconnecting between a segment of wireline  202  and the connector  112 . The electrical contact sub  208  and the rubber boot  204  do not form part of the retrieval tool  200 . They serve to mechanically and electrically interconnect the connector  112  to the wireline  202 . 
     The connector  112  is connected at its distal end to the electronics housing  114  as in  FIGS. 2A to 4C . However, in  FIG. 6A , the electronics housing  114  is surrounded by a bypass sleeve  218 . A proximal end of the bypass sleeve  218  is connected to a coiled tubing connector  206 . The bypass sleeve  218  and the coiled tubing connector  206  are both hollow, and may be tubular. The coiled tubing connector  206  is adapted to connect to the coiled tubing at its free end so that the coiled tubing can be used to position the retrieving tool  200  in the well. 
     As can be seen in  FIG. 6A , the combination of the coiled tubing connector  206  and the bypass sleeve  218  define an outer hollow member in fluid connection with the coiled tubing. The wireline  202 , the rubber boot  204 , the electrical contact sub  208 , the connector  112 , and the electronics housing  114  define an inner member surrounded by the outer hollow member. An elongated fluid chamber or conduit  212  is defined between the inner member and the outer member which allows fluid to flow down the coiled tubing and around the electronics. The electronics remain sealed from the fluid chamber  212 . 
       FIGS. 6A to 6C  also depict an inner elongated member comprised of a drive mandrel  250 , an actuator screw  262  and a retrieving mandrel  266  comparable the drive mandrel  150 , the actuator screw  162  and the retrieving mandrel  166 . The difference between the inner elongated member of  FIGS. 6A to 6C , from the inner elongated member of  FIGS. 2A to 4C , is that the inner elongated member of  FIGS. 6A to 6C  has a fluid flow port or conduit  224  defined longitudinally therethrough. The drive mandrel  250  the actuator screw  262  and the retrieving mandrel  266  are connected to each other in a fluid tight manner by the seals  234  at either end of the actuator screw  262 . This prevents any fluid exchange between the fluid flow port  224  and the chambers  165 A,  165 B,  167 A and  167 B. 
     The elongated fluid chamber  212  is in fluid communication with the fluid flow port  224  such that fluid entering the coiled tubing can exit through the distal end of the retrieving mandrel  266 . In particular, the distal end of the bypass sleeve  218  is attached to the proximal end of the guide sleeve  138  through a threaded connection and the connection is sealed with the seals  116 . Interconnection ports  244  are defined between where the elongated fluid chamber  212  ends adjacent to the end of the bypass sleeve  218  and where the fluid flow port  224  begins at the proximal end of the drive mandrel  250 . These interconnection ports extend through the guide sleeve  138  and the drive mandrel  250  generally perpendicular to the direction of the elongated fluid chamber  212  and the fluid flow port  224 . Fluids pumped through the coiled tubing will flow through the space (i.e. chamber  212 ) between the bypass sleeve  218  and the outside diameter of the tool (i.e. electronics housing  114 ) then it will cross over to the inside of the tool through the ports  244  in the guide sleeve  138  and the drive mandrel  250  to the fluid flow port  224 . Although the coiled tubing connector  206  and the bypass sleeve  218  are depicted as separate from the electronics housing  114 , it will be appreciated that they may be interconnected such that flow passages, rather than a complete chamber  212 , may be defined. 
     The flow path through the tool may be used for other purposes. For example, fluids may be pumped through to perform clean-outs for fishing jobs or for formation stimulation. Another option is to pump fluids, particularly cold fluids, around the electronics. If the tool is being run into a hot well whose temperature exceeds the temperature rating of the tool, by pumping cold fluids through the tool, the electronics section will be cooled thereby enabling the tool to perform. 
       FIGS. 2A to 4C  and  6 A to  6 C depict the slips  180  as the means of fixing the tool  110  in place. Other means may also be used.  FIG. 7  provides an example of a portion of a retrieving tool  300 . The tool  300  is shown within three segments of tubing or casing  388 ,  386  and  384 . The middle segment of tubing or casing  386  is a landing nipple which has a profile  390  defined around the interior surface. 
     The tool  300  comprises a bottom housing  364  comparable to bottom housing  164  previously described. The bottom housing  364  is connected to a retrieving housing  374  which in turn connects to a locking lug holder  326 . Locking lugs  350  are movably held within the locking lug holder  326 . The outer contour of the locking lugs  350  matches the profile  390  so that the locking lugs  350  fit into the profile  390 . 
     A retrieving mandrel  366  extends axially through the centre of the bottom housing  364 , the retrieving housing  374 , the locking lug holder  326 , and the locking lugs  350 . The retrieving mandrel  366  has an essentially constant circular diameter. However, the retrieving mandrel  366  has two necked down portions  327  and  328  which are used to position and release the locking lugs. Springs or other biasing means  352  are positioned between the retrieving mandrel  366  and the locking lugs  350 . The locking lugs  350  are movable inwards and outwards perpendicular to the direction of travel of the retrieving mandrel  366 . The springs  352  bias or push the locking lugs  350  in the outwards direction. 
     In use, the springs  352  are initially positioned in the necked down portion  327  of the retrieving mandrel  366 . The tool  300  is inserted into the well with the mandrel  366  held in this position until the locking lugs  350  reach the profile  390  of the landing nipple  386 . The locking lugs  350  are forced outward and locked in position in the profile  390  as shown in  FIG. 7A . Actuation of the tool  300  will cause the retrieving mandrel  366  to move upward (to the left in the  FIGS. 7A to 7C ) relative to the locking lugs  350  and the housings  364  and  374  to perform its retrieving function. A larger diameter portion of the mandrel  366 , as shown in  FIG. 7B  will come between the locking lugs  350  and further compress the spring  352 . The larger diameter portion of the mandrel  366  will lock the locking lugs  350  in place. As the retrieving function is performed, the retrieving mandrel  366  is moved upwards relative to the locking lugs  350  until the second necked down portion  328  of the mandrel is positioned under the lugs  350  and the springs  352 . The locking lugs  350  can now be forced inward in the second necked down portion  328  of the retrieving mandrel  366  so that the locking lugs  350  are drawn out of the landing nipple  386  and the tool  300  can be withdrawn from the well. Other locking means may also be used. 
     In addition to the setting and retrieving applications already described, the tools described herein can also be used for other applications such as shifting of sleeves and measuring the location of an object in the well. For example, if the tool is locked in a known position in the well, the mandrel can be extended and the positioning encoder  122  or other counter can be used to precisely determine the location of the end of the tool and therefore the location of an object contacted by the tool. 
     Extended reach slip assemblies can be used to perform retrieving, shifting or measuring operations in through tubing applications. 
     The number of housings and configurations depicted in  FIGS. 2A to 7C  is based, at least in part, on manufacturing concerns. The invention encompasses tools having more or fewer housings. The tubular shape of the housings is preferred but not essential. 
     Although seals are depicted throughout the figures, seals may be unnecessary between the relatively stationary parts if a sufficiently tight fit is present. 
     The mechanical means of interconnecting the various components of the tool shown in the figures are exemplary only. Other known mechanical means of interconnecting the various components are contemplated by the invention. 
     Numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.