Apparatus and method for running and retrieving tubing using an electro-mechanical linear actuator driven downhole tractor

Abstract

An electric motor-actuated tractor (e-Tractor) apparatus and method for use in downhole operations. The apparatus includes a power subassembly, a tractor subassembly and one or more gripper subassemblies and can be: run in a single or multiple e-Tractor configuration; run in either intermittent-motion tractoring mode or continuous-motion tractoring mode with the ability to switch between the two modes; used to generate both distal and proximal longitudinal forces to move the run-in string into or out of the wellbore; repeatedly activated and deactivated without run-in string manipulation or hydraulic pressure; and combined with tensiometer and other sensor package options to provide real-time data to the surface to optimize tractoring operations. The apparatus and method are well-suited for application in an c-coil conveyed workover or completion system, and for use in extended reach laterals in horizontal wells.

Claims

1. An electric motor-actuated tractor (e-Tractor) apparatus for use in a wellbore comprising: a longitudinally extending inner body assembly; a gripper assembly movable between (i) a retracted position and (ii) an outward gripping position for engaging an inner surface in the wellbore; a linear actuator subassembly, in the inner body assembly, comprising a longitudinally extending screw, at least one bi-directional electric motor which is directly or indirectly coupled to an end of the screw, and a nut which is positioned on the screw, the nut being locked against rotation; and the rotation of the screw by the at least one bi-directional electric motor in a first rotational direction when using the e-Tractor apparatus in the wellbore causes the nut to move in a first longitudinal direction with respect to the inner body assembly which causes the gripper assembly to move from its retracted position to its outward gripping position and then, with the gripper assembly in its outward gripping position, the continued rotation of the screw by the at least one bi-directional electric motor in the first rotational direction pulls or pushes the inner body assembly in a second longitudinal direction, opposite the first longitudinal direction, with respect to the gripper assembly.

2. The e-Tractor apparatus of claim 1 comprising: the at least one bi-directional electric motor being a first bi-directional electric motor; the end of the screw being a first end of the screw; and the linear actuator subassembly further comprising a second bi-directional electric motor in the inner body assembly which is directly or indirectly coupled to a second end of the screw opposite the first end of the screw.

3. The e-Tractor apparatus of claim 2 further comprising the linear actuator subassembly including: a first motor control electronics unit, within the inner body assembly, which is electronically connected to the first bi-directional electric motor; a second motor control electronics unit, within the inner body assembly, which is electronically connected to the second bi-directional electric motor; and the first and second motor control electronics units operating the first and second bi-directional electric motors in synchronization in opposite rotational directions at identical speeds for rotating the screw.

4. The e-Tractor apparatus of claim 3 further comprising the linear actuator subassembly including: a first battery, within the inner body assembly, which is electrically connected to the first bi-directional electric motor for at least temporarily powering the first bi-directional electric motor and a second battery, within the inner body assembly, which is electrically connected to the second bi-directional electric motor for at least temporarily powering the second bi-directional electric motor.

5. The e-Tractor apparatus of claim 1 further comprising: a longitudinally extending outer housing having a first end and a second end; the inner body assembly being longitudinally translatable within and relative to the outer housing, the inner body assembly including an end segment which projects from the first end of the outer housing; and the gripper assembly being positioned on the end segment of the inner body assembly, the end segment being longitudinally translatable through the gripper assembly, and at least a portion of the gripper assembly being connected or linked to the outer housing for moving the gripper assembly between its retracted position and its outward gripping position.

6. The e-Tractor apparatus of claim 5 further comprising: an inner sleeve which is positioned within the outer housing and outside of the inner body assembly; a mechanical linkage, between the nut and the inner sleeve, which extends through a slot in the inner body assembly; and a carrying structure for the outer housing which is engaged by the inner sleeve to move the outer housing longitudinally with respect to the inner body assembly to move the gripper assembly to the outward gripping position.

7. The e-Tractor apparatus of claim 6 further comprising the mechanical linkage comprising: a lug; a pair of lug retainers which retain the lug on the nut; and a plurality of pins which extend through the lug retainers and the lug to the inner sleeve.

8. The e-Tractor apparatus of claim 6 further comprising: the movement of the nut in the first longitudinal direction with respect to the inner body assembly carries the inner sleeve, outside of and with respect to the inner body assembly, in the first longitudinal direction into engagement with the carrying structure for the outer housing so that the inner sleeve also moves the outer housing in the first longitudinal direction with respect to the inner body assembly; the movement of the outer housing in the first longitudinal direction moves the gripper assembly to its outward gripping position; and the movement of the gripper assembly to its outward gripping position in the wellbore stops the movement of the nut, the inner sleeve, and the outer housing in the first longitudinal direction relative to the wellbore so that the continued rotation of the screw by the at least one bi-directional electric motor in the first rotational direction will pull or push the inner body within and relative to the inner sleeve, and within and relative to the outer housing, in the second longitudinal direction.

9. The e-Tractor apparatus of claim 1 further comprising: the gripper assembly being a first gripper assembly; the e-Tractor apparatus further comprising a second gripper assembly movable between (i) a retracted position and (ii) an outward gripping position for engaging the inner surface in the wellbore; when the first gripper assembly is in its outward gripping position in the wellbore and the at least one bi-directional electric motor rotates the screw in a second rotational direction opposite the first rotational direction, the rotation of the screw in the second rotational direction causes the nut to move in the second longitudinal direction with respect to the inner body assembly to move the first gripper assembly from its outward gripping position to its retracted position; and with each of the first and the second gripper assemblies in its retracted position, rotation of the screw in the second rotational direction causes the nut to move in the second longitudinal direction which causes the second gripper assembly to move from its retracted position to its outward gripping position, and then, as the at least one bi-directional electric motor continues to rotate the screw in the second rotational direction with the second gripper assembly in its outward gripping position, the continued rotation of the screw in the second rotational direction pulls or pushes the inner body assembly in the first longitudinal direction with respect to the second gripper assembly.

10. The e-Tractor apparatus of claim 9 further comprising: a longitudinally extending outer housing having a first end and a second end; the inner body assembly being longitudinally translatable within and relative to the outer housing, the inner body assembly including a first end segment which projects from the first end of the outer housing and a second end segment which projects from the second end of the outer housing; the first gripper assembly being positioned on the first end segment of the inner body assembly, the first end segment being longitudinally translatable through the first gripper assembly, and at least a portion of the first gripper assembly being connected or linked to the outer housing for moving the first gripper assembly between its retracted position and its outward gripping position: and the second gripper assembly being positioned on the second end segment of the inner body assembly, the second end segment being longitudinally translatable through the second gripper assembly, and at least a portion of the second gripper assembly being connected or linked to the outer housing for moving the second gripper assembly between its retracted position and its outward gripping position.

11. The e-Tractor apparatus of claim 10 further comprising: an inner sleeve which is positioned within the outer housing and outside of the inner body assembly; a mechanical linkage, between the nut and the inner sleeve, which extends through a slot in the inner body assembly; a first carrying structure for the outer housing which is engaged by the inner sleeve to move the outer housing in the first longitudinal direction with respect to the inner body assembly to move the first gripper assembly to its outward gripping position; and a second carrying structure for the outer housing which is engaged by the inner sleeve to move the outer housing in the second longitudinal direction with respect to the inner body assembly to move the second gripper assembly to its outward gripping position.

12. The e-Tractor apparatus of claim 11 further comprising: the movement of the nut in the first longitudinal direction with respect to the inner body assembly carries the inner sleeve, outside of and with respect to the inner body assembly, in the first longitudinal direction into engagement with the first carrying structure for the outer housing so that the inner sleeve also moves the outer housing in the first longitudinal direction with respect to the inner body assembly; the movement of the outer housing in the first longitudinal direction moves the first gripper assembly to its outward gripping position; the movement of the first gripper assembly to its gripping position in the wellbore stops the movement of the nut, the inner sleeve, and the outer housing in the first longitudinal direction relative to the wellbore so that the continued rotation of the screw by the at least one bi-directional electric motor in the first rotational direction will pull or push the inner body assembly within and relative to the inner sleeve, and within and relative to the outer housing, in the second longitudinal direction; the movement of the nut in a second longitudinal direction with respect to the inner body assembly carries the inner sleeve, outside of and with respect to the inner body assembly, in the second longitudinal direction into engagement with the second carrying structure for the outer housing so that the inner sleeve also moves the outer housing in the second longitudinal direction with respect to the inner body assembly; the movement of the outer housing in the second longitudinal direction moves the second gripper assembly to its outward gripping position; and the movement of the second gripper assembly to its outward gripping position in the wellbore stops the movement of the nut, the inner sleeve, and the outer housing in the second longitudinal direction relative to the wellbore so that the continued rotation of the screw by the at least one bi-directional electric motor in the second rotational direction will pull or push the inner body within and relative to the inner sleeve, and within and relative to the outer housing, in the first longitudinal direction.

13. The e-Tractor apparatus of claim 11 further comprising: the first end segment of the inner body assembly being a first mandrel which projects from the first end of the outer housing and extends through the first gripper assembly; the second end segment of the inner body assembly being a second mandrel which projects from the second end of the outer housing and extends through the second gripper assembly; and the inner body assembly also includes a screw housing in which the screw is rotatably positioned, the screw housing having the slot formed therein through which the mechanical linkage extends.

14. The e-Tractor apparatus of claim 11 further comprising: the second gripper assembly comprising a second gripper sub which is connected to the second end of the outer housing; the second gripper sub including the first carrying structure for the outer housing the first carrying structure being engaged by a second end of the inner sleeve; the first gripper assembly comprising a first gripper sub which is connected to the first end of the outer housing; and the first gripper sub including the second carrying structure for the outer housing, the second carrying structure being engaged by a first end of the inner sleeve, the second end of the inner sleeve being opposite the first end of the inner sleeve.

15. The e-Tractor apparatus of claim 1 further comprising at least one sensor for real-time sensing which senses or measures a pressure, a temperature, a load, a stress, a tension, a position of the e-Tractor apparatus or of a component thereof, an orientation of the e-Tractor apparatus or of a component thereof, or a combination thereof.

16. The e-Tractor apparatus of claim 1 wherein the inner surface in the wellbore is an inner surface of a casing installed in the wellbore.

17. The e-Tractor apparatus of claim 1 wherein the inner surface in the wellbore is an interior wall of a borehole.

18. A downhole apparatus for use in a wellbore comprising: a run-in string and one or more electric motor-actuated tractor (e-Tractor) apparatuses, each of the one or more e-Tractor apparatuses comprising a longitudinally extending inner body assembly having an end which is connected or linked to the run-in string, a gripper assembly movable between (i) a retracted position and (ii) an outward gripping position for engaging an inner surface in the wellbore, a linear actuator subassembly, in the inner body assembly, comprising a longitudinally extending screw, at least one bi-directional electric motor which is directly or indirectly coupled to an end of the screw, and a nut which is positioned on the screw, the nut being locked against rotation, and a motor control which is electronically connected to the at least one bi-directional motor, the motor control being operable to control the at least one bi-directional motor to rotate the screw in a first rotational direction, in a first stage of operation, which causes the nut to move in a first longitudinal direction with respect to the inner body assembly which moves the gripper assembly from its retracted position to its outward gripping position at a first setting location in the wellbore, and then continue to rotate the screw in the first rotational direction, in a tractoring stage of operation, with the gripper assembly in its outward gripping position, which pulls or pushes the inner body assembly and the run-in string in a second longitudinal direction, opposite the first longitudinal direction, with respect to the gripper assembly, and then rotate the screw in a second rotational direction opposite the first rotational direction, in a third stage of operation, which causes the nut to move in the second longitudinal direction with respect to the inner body assembly to a point for releasing the gripper assembly, and then continue to rotate the screw in the second rotational direction, in a fourth stage of operation, which causes the nut to continue to move in the second longitudinal direction with respect to the inner body assembly to release the gripper assembly and then move the gripper assembly in the second longitudinal direction to a next setting location in the wellbore.

19. The downhole apparatus of claim 18 further comprising: the downhole apparatus comprising a plurality of the e-Tractor apparatuses and the motor controls of the plurality of the e-Tractor apparatuses being operable for operating the e-Tractor apparatuses together in a continuous tractoring mode in which whenever any of the e-Tractor apparatuses is operating in any of the first, the third, or the fourth stage of operation, at least one other of the e-Tractor apparatuses will be operating in the tractoring stage of operation.

20. The downhole apparatus of claim 19 further comprising the motor controls of the plurality of the e-Tractor apparatuses being operable for changing from the continuous tractoring mode to an intermittent tractoring mode in which all of the e-Tractor apparatuses operate simultaneously, in unison, in each of the first, the tractoring, the third, and the fourth stages of operation.

21. The downhole apparatus of claim 19 further comprising the motor controls of the plurality of the e-Tractor apparatuses operating the at least one bi-directional electric motor of each of the e-Tractor apparatuses at a higher rotational speed in the first, the third, and/or the fourth stage of operation than in the tractoring stage of operation.

22. The downhole apparatus of claim 18 further comprising the run-in string comprising a coiled tubing, an c-coil, a cable, or a wireline.

23. The downhole apparatus of claim 18 further comprising the run-in string having an electric cable, an electric wireline, a fiberoptic cable, or a combination thereof which extends through or is incorporated in the run-in string.

24. The downhole apparatus of claim 18 further comprising each of the one or more e-Tractor apparatuses having a fluid passageway for delivering a fluid therethrough.

25. The downhole apparatus of claim 18 further comprising each of the one or more e-Tractor apparatuses also comprising: a longitudinally extending outer housing having a first end and a second end; the inner body assembly being longitudinally translatable within and relative to the outer housing, the inner body assembly including an end segment which projects from the first end of the outer housing; the gripper assembly being positioned on the end segment of the inner body assembly, the end segment being longitudinally translatable through the gripper assembly, and at least a portion of the gripper assembly being connected or linked to the outer housing for moving the gripper assembly between its retracted position and its outward gripping position; an inner sleeve which is positioned within the outer housing and outside of the inner body assembly; a mechanical linkage, between the nut and the inner sleeve, which extends through a slot in the inner body assembly; and a carrying structure for the outer housing which is engaged by the inner sleeve to move the outer housing longitudinally with respect to the inner body assembly to move the gripper assembly to the outward gripping position.

26. A method of moving a run-in string longitudinally in a wellbore, the method comprising the steps of: a) providing a plurality of electric motor-actuated tractor (e-Tractor) apparatuses, each of the plurality of the e-Tractor apparatuses being connected or linked to the run-in, and each of the plurality of the e-Tractor apparatuses comprising a gripper assembly and at least one bi-directional electric motor which is operated to turn a screw in the e-Tractor apparatus to cause the e-Tractor apparatus to repeatedly (1) perform a first operation in which the gripper assembly is moved from a retracted position to an outward gripping position in contact with an inner surface in the wellbore at a first location in the wellbore, and then (2) perform a tractoring operation which pulls or pushes the run-in string in a first longitudinal direction in the wellbore, and then (3) perform a third operation which includes retracting the gripper assembly from its outward gripping position to its retracted position, and then (4) perform a fourth operation in which the gripper assembly is moved in the first longitudinal direction from the first location to a next setting location in the wellbore and b) operating the plurality of the e-Tractor apparatuses in a continuous tractoring mode in which whenever any one of the e-Tractor apparatuses is performing any of the first, the third, or the fourth operations, at least one other of the plurality of the e-Tractor apparatus is performing the tractoring operation.

27. The method of claim 26 further comprising changing the plurality of the e-Tractor apparatuses from operating in the continuous tractoring mode to operating in an intermittent tractoring mode in which all of the e-Tractor apparatuses simultaneously perform each of the first, the tractoring, the third, and the fourth operations in unison.

28. The method of claim 26 further comprising operating the at least one bi-directional electric motor of each of the e-Tractor apparatuses at a higher rotational speed when performing the first, the third, and/or the fourth operation than when performing the tractoring operation.

29. A method of moving a run-in string longitudinally in a horizontal or deviated wellbore, the method comprising the steps of: a) providing at least one electric motor-actuated tractor (e-Tractor) apparatus, which is connected or linked to the run-in string, the at least one e-Tractor apparatus comprising a gripper assembly, a rotatable, longitudinally extending screw in the e-Tractor apparatus, a nut which is positioned on the screw and locked against rotation to translate a rotation of the screw to a linear movement of the nut on the screw, and at least one bi-directional electric motor for rotating the screw and b) operating the at least one bi-directional electric motor to turn the screw so that the nut is moved linearly on the screw to cause the e-Tractor apparatus to repeatedly (1) perform a first operation in which the gripper assembly is moved from a retracted position to an outward gripping position in contact with an inner surface of the horizontal or deviated wellbore at a first location in the horizontal or deviated wellbore, and then (2) perform a tractoring operation which pulls or pushes the run-in string in a first longitudinal direction in the horizontal or deviated wellbore, and then (3) perform a third operation which includes retracting the gripper assembly from its outward gripping position to its retracted position, and then (4) perform a fourth operation in which the gripper assembly is moved in the first longitudinal direction from the first location to a next setting location in the horizontal or deviated wellbore.

30. The method of claim 29 further comprising moving the run-in string in the horizontal or deviated wellbore using only the tractoring operation of the at least one e-Tractor apparatus to pull or push the run-in string without using surface injection, applied hydraulic pressure, or vibration or agitation techniques.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 provides a cross-sectional view of a wellbore having been completed in a horizontal orientation with a triple e-Tractor assembly configuration depicted on the proximal end of the coiled tubing string.

(2) FIG. 2 provides a cross-sectional view of a wellbore having been completed in a horizontal orientation with a single e-Tractor assembly configuration depicted on the proximal end of the coiled tubing string.

(3) FIG. 3 is a cross-sectional view of the Coiled Tubing Specialties' e-Tractor as shown in three segments representing a single e-Tractor assembly.

(4) FIG. 4 is an inset of the mechanical linkage sub assembly and some of its components.

(5) FIG. 5 is an inset of the upper gearhead and some of its components.

(6) FIG. 6 is an inset of the lower gearhead and some of its components.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(7) FIG. 1 is a cross-sectional view of an illustrative horizontal wellbore 1 with multiple inventive, e-coil conveyed, electric motor-actuated e-Tractor assemblies 7 deployed in triple-tractor configuration. Multiple e-Tractors 7 are shown in FIG. 1 to represent both the intermittent-motion tractoring mode and the continuous-motion tractoring mode. The intermittent mode is used when the tractoring force available is more critical than the pace of the tractoring motion. In the intermittent mode, all the e-Tractors 7 in the multiple-tractor tool string can be used simultaneously to create the maximum pull or push, depending on motor rotation direction and the desired direction of CT movement. The ability to run and selectively actuate multiple c-Tractor assemblies 7 to switch from continuous to intermittent mode as needed helps optimize each tractoring operation. Likewise, the option to vary the pulling (pushing) force based on CT and/or well configuration as a function of the power applied from the surface and the ability of the electronics controls to monitor rotation and torque in each e-Tractor assembly helps further improve each phase of CT tractoring operations.

(8) In the depicted example, when running in the continuous mode, three e-Tractors 7 are run in series such that while two of the tractors 7 are gripping and pulling, the third e-Tractor is resetting along the length of its roller screw such that the third e-Tractor 7 will engage as another e-Tractor travels to the end of its effective roller screw length, at which point that e-Tractor begins resetting. With this synchronized gripping-pulling-resetting sequence, two of the three e-Tractors 7 are always pulling such that the e-coil 6 is maintained in continuous motion. The ability to provide continuous movement of the e-coil 6 makes the tractoring operation more efficient by eliminating non-productive pauses between tractor-enabled, run-in string movement cycles. Further, and perhaps more importantly, the overall stresses on e-coil 6 are reduced and the incrementally higher force requirements (to overcome static friction, as opposed to kinetic) imposed on the e-Tractors 7 are avoided by maintaining constant (versus intermittent) motion.

(9) The multiple e-Tractor 7 series configuration can also be operated in intermittent tractoring-motion mode. That is, in FIG. 1, all three c-Tractors would be maintained at the same approximate points in their respective tractoring strokes. Say, for example, subsequent to drilling out a frac plug at a specific depth the wellbore was being circulated clean while the CT was stationary. To proceed to the next frac plug location further downhole, the static friction force on the CT is 35,000 #, and after initiating CT movement the kinetic friction force reduces to 25,000 #. In this example, all three e-Tractors 7 (pulling up to 15,000 # each, or a maximum of 45,000 # combined) could be initially placed in intermittent mode to initiate CT movement, then the series switched to continuous mode (with up to 30,000 # pulling force) to maintain downhole advancement of the CT 6.

(10) FIG. 2 is a cross-sectional view, similar to FIG. 1, of an illustrative horizontal wellbore 1 with an inventive, e-coil conveyed, electric motor-actuated, e-Tractor assembly 7 deployed in a single-tractor configuration depicted in the wellbore lateral C. The single c-Tractor 7 is shown in FIG. 2 to represent the intermittent-motion tractoring mode, as the continuous-motion tractoring mode requires more than a single e-Tractor configuration which enable one e-Tractor to be resetting while another e-Tractor assembly is applying longitudinal force to the run-in string. Running the e-Tractor, in the intermittent-motion tractoring mode, however, does allow for the full force-generating capability of 15,000 lbs. for each e-Tractor to be leveraged in both single and multiple tractor configurations. Also, as depicted in FIG. 2, the single e-Tractor configuration creates a less complex, shorter bottomhole assembly (BHA) for applications not requiring the additional pulling force or pace of motion provided by a multiple e-Tractor configuration, thus providing greater efficiencies in less critical CT tractoring applications.

(11) In shorter laterals and those applications requiring less tractoring speed than available in a continuous tractoring mode configuration, a single e-Tractor assembly provides nearly 50% greater tractoring capacity than other 5½″ OD casing compatible tractors, rendering even the single e-Tractor configuration better suited to address more demanding tractoring load requirements as lateral lengths continue to grow.

(12) Utilizing the power and data transmitting capabilities of e-coil, often including fiber optic capabilities embedded within the wireline cable, the present disclosure also describes the method and apparatus of an electric coiled tubing tractor, or “e-Tractor”. The fiber optic-enabled cable, can provide both electric and fiber optic capability in a single wireline cable. Any number of sensors of any type can be used in or in association with the inventive e-Tractor assembly 1000. For purposes of illustration, a sensor 8 is shown in FIG. 1 for real-time sensing and/or measurement of a pressure, a temperature, a load, a stress, a tension, a position of the e-Tractor apparatus or of a component thereof, an orientation of the e-Tractor apparatus or of a component thereof, or a combination thereof.

(13) FIG. 3 is a half-section view of the e-Tractor assembly 1000, an e-coil conveyed and operated downhole tractor used to pull coiled tubing into and push the coiled tubing out of the casing in a horizontal wellbore. The e-Tractor assembly 1000 comprises two main subassemblies, i.e. the tractor subassembly 100 and the power subassembly 200. The tractor subassembly 100 generally comprises the outer components of the e-Tractor assembly 1000 and incudes upper 100.1 and lower 100.2 gripper subassemblies that grip the casing 4 ID, thereby providing an anchor against which the coiled tubing 6 and power subassembly 200 can be pulled. The power subassembly 200 includes the inner assemblies for the upper 200.3 and lower 200.4 motors, upper 200.5 and lower 200.6 gearheads, upper 200.8 and lower 200.9 motor control electronics and roller screw shaft 300.1. The power subassembly 200 receives electric power from the e-coil unit power pack on the surface (not shown) through the electric cable 200.7 contained within the e-coil string 6 and converts it to longitudinal motion for pulling the coiled tubing 6 and e-Tractor assembly 1001) into the well casing 4.

(14) As used herein and in the claims, the term “screw” refers to and includes a roller screw shaft or any other type of elongate screw or bolt which can be used for translating rotational motion into linear motion in the inventive e-Tractor assembly 1000.

(15) FIG. 4 is an inset drawing of the mechanical linkage subassembly 400 and some of its various components, including the lug 100.8, roller screw nut 200.1, upper 100.9 and lower 100.10 lug retainers, four pins 100.7 and the partial external upset 100.6 on the inner sleeve 100.4. Other mechanical linkage subassembly 400 components are indicated on FIG. 3 such that the components may be seen in the context of the entire c-Tractor assembly 1000.

(16) As used herein and in the claims, the term “nut” refers to and includes a roller screw nut or any other type of nut or other internally threaded element which is compatible with the screw for translating rotational motion into linear motion in the inventive e-Tractor assembly 1000.

(17) FIG. 5 is an inset of the upper gearhead output shaft 200.27 and related components. This includes the upper gearhead 200.5, cap screws 200.30, torque keys 200.28, and upper key coupling 200.29. Given the scale of FIG. 3 and the relative size of these components, the inset is provided for additional clarity.

(18) FIG. 6 is an inset of the lower gearhead output shaft 200.33 and related components. This includes the lower gearhead 200.6, cap screws 200.32, torque keys 200.34, and lower key coupling 200.35. Given the scale of FIG. 3 and the relative size of these components, the inset is provided for additional clarity.

(19) The tractor subassembly 100 comprises the upper 100.1 and lower 100.2 gripper subassemblies that are connected by the outer sleeve or other outer housing 100.3. The outer sleeve (housing) 100.3 transfers the load from the inner sleeve 100.4 to the upper and lower gripper subassemblies. 100.1 and 100.2, respectively.

(20) The upper gripper assembly 100.1 comprises an upper gripper sub 100.12 which is threadedly connected or otherwise made up to the upper end of outer housing 100.3. Similarly, the lower gripper assembly 100.2 comprises a lower gripper sub 100.13 which is threadedly connected or otherwise made up to the lower end of the outer housing 100.3.

(21) The upper gripping sub 100.12 includes an end or shoulder 100.14 which is positioned within the upper end of the outer housing 100.3 for engagement by the upper end of the inner sleeve 100.4 to provide a carrying structure for the outer housing 100.3 so that when the upper end of the inner sleeve 100.4 contacts the carrying structure 100.CS1 and then continues to move upward, the outer housing 100.3 is also carried upward, with respect to the inner body assembly 200.IB of the e-Tractor assembly (identified below), which in turn pulls the cone piece 100.CL of the lower gripper assembly 100.2 upward beneath the slips or other gripper elements 100.GL of the lower gripper assembly 100.2 to thereby force the gripping elements 100.GL outward into engagement with the inner surface of the well casing or the borehole.

(22) Similarly, the lower gripping sub 100.13 includes an end or shoulder 100.15 which is positioned within the lower end of the outer housing 100.3 for engagement by the lower end of the inner sleeve 100.4 to provide a second carrying structure for the outer housing 100.3 so that when the lower end of the inner sleeve 100.4 contacts the second carrying structure 100.CS2 and then continues to move downward, the outer housing 100.3 is also carried downward, with respect to the inner body assembly 200.IB which in turn pulls the cone piece 100.CU of the upper gripper assembly 100.1 downward beneath the slips or other gripper elements 100.GU of the upper gripper assembly 100.1 to thereby force the gripping elements 100.GU of the upper gripper assembly 100.1 outward into engagement with the inner surface of the well casing or the borehole.

(23) The annulus between the outer sleeve 100.3 ID and inner sleeve 100.4 OD form part of the fluid flow path 100.5 through the e-Tractor. The inner sleeve 100.4 is made up on the OD of the power subassembly 200 and transfers longitudinal load from the roller screw nut 200.1. The inner sleeve 100.4 has a partial external upset 100.6 in the center 100.5 with the remainder of the external upset machined down to the inner sleeve 100.4 OD, providing a fluid flow path 100.5 around the external upset. Pins 100.7 located in radial holes through the partial external upset 100.6 extend through aligned radial holes in the lug 100.8 and upper 100.9 and lower 100.10 lug retainer. The roller screw nut 200.1 is made up on roller screw shaft 300.1 in the power subassembly 200. Rotary motion of the roller screw shaft 300.1 is translated into longitudinal motion of the roller screw nut 200.1 as power is directed to the upper 200.3 and lower 200.4 opposing bi-directional electric motors in each e-Tractor assembly 1000, through the respective upper 200.5 and lower 200.6 gearheads and into the roller screw shaft 300.1. Power is provided to the upper 200.3 and lower 200.4 electric motors through the cable 200.7 from the surface. The upper 100.9 and lower 100.10 lug retainers are sleeves shouldered against the upper and lower ends of the roller screw nut 200.1 and are used to transfer longitudinal force from the roller screw nut 200.1 to the lug 100.8 through pins 100.7 that extend through radial holes in the upper 100.9 and lower 100.10 lug retainers and shoulders at each end of the lug 100.8. A key 100.11 is inserted in an external slot on the roller screw nut 200.1 and internal slot in the lug 100.8 to rotationally lock the roller screw nut 200.1 and the lug 100.8 together. The lug 100.8 is assembled in the slot in the screw housing 300.2 in the inner sleeve 100.4 and over the roller screw nut 200.1 and upper 100.9 and lower lug 100.10 retainers. The lug 100.8 is held in place with pins 100.7 extending through radial holes in the inner sleeve 100.4, lug 100.8, and upper 100.9 and lower 100.10 lug retainers. Longitudinal load is transferred from the roller screw nut 200.1 through the upper 100.9 and lower 100.10 lug retainers, and the lug 100.8 and pins 100.7 to the inner sleeve 100.4. The lug 100.8 also prevents rotation of the roller screw nut 200.1 by contacting the sides of the slot in the screw housing 300.2. The pins 100.7 are inserted through radial holes in the inner sleeve 100.4, lug 100.8, and upper 100.9 and lower 100.10 lug retainers, locking the components together to transfer longitudinal loads from the roller screw nut 200.1 to the upper 100.1 and lower 100.2 gripper assemblies. The upper end of pins 100.7 has external o-rings 100.99 in grooves which seal against the ID of radial holes through the inner sleeve 100.4.

(24) Alternatively, it will be understood that the mechanical linkage subassembly 400 used in the inventive e-Tractor apparatus can be any type of assembly which will relay the linear force imparted by the linear actuator assembly of the inventive apparatus to the gripper assemblies 100.1 and 100.2 and other components as needed.

(25) The power subassembly 200 contains the upper mandrel 200.10 which is made up to the upper end of the upper motor subassembly 200.11. The upper mandrel 200.10 ID contains power/control cable 200.7 and forms part of the fluid flow path 100.5 through the e-Tractor assembly 1000. The OD of the upper mandrel 200.10 is a sealing surface against which internal seals 200.12 in the upper gripper subassembly 100.1 seal. The annulus between the upper mandrel 200.10 OD and inner sleeve 100.4 ID form part of the fluid flow path through the e-Tractor assembly 1000. The upper motor subassembly 200.11 applies torque to the upper end of the roller screw shaft 300.1. The upper torque key 200.13 fits in aligned slots in the lower end of the upper motor housing 200.15, upper screw housing cap 300.3, and upper end of the screw housing 300.2, rotationally locking all three components together. Screws 200.14 are inserted through radial holes in the torque key 200.13 and made up in aligned radial threaded holes in the bottom of the slot in the upper screw housing cap 300.3 to hold the upper torque key 200.13 in place. The upper split ring shoulder 200.16 fits in an internal groove in upper end of the screw housing 300.2 and is retained in place by the upper split ring shoulder retainer 200.17. It provides an internal shoulder for the upper grooved roller bearing 300.4, preventing downward movement relative to the screw housing 300.2. The screw housing 300.2 has a longitudinal slot 300.2S through which the lug 100.8 in the tractor subassembly 100 extends, connecting the roller screw nut 200.1 to the tractor subassembly inner sleeve 100.4 made up on the OD of the power subassembly 200. The screw housing 300.2 also has an external slot extending its length in which the power/control cable 200.7 is assembled. The lower motor subassembly 200.18 applies torque to the lower end of the roller screw shaft 300.1. The lower split ring shoulder 200.19 fits in the internal groove in lower end of the screw housing 300.2 and is retained in place by the lower split ring shoulder retainer 200.20. It provides an internal shoulder for the lower grooved roller bearing 300.5, preventing downward movement relative to the screw housing 300.2. The lower torque key 200.21 fits in aligned slots in the upper end of the lower motor housing 200.31, lower screw housing cap 300.6, and lower end of the screw housing 300.2, rotationally locking all three components together. Screws 200.23 are inserted through radial holes in the torque key 200.21 and made up in aligned radial threaded holes in the bottom of the slot in the lower screw housing cap 300.6 to hold the lower torque key 200.21 in place. The pressure equalizing piston 300.7 is made up on the lower end of the lower actuator shoe 200.22 on the lower motor subassembly 200.18 and transfers hydraulic pressure in the e-Tractor assembly 1000 to the hydraulic oil 200.23 in the power subassembly 200. The pressure equalizing piston 300.7 has internal seals 300.8 that seal against the lower end of the lower actuator shoe 200.22 and external seals 300.9 that seal against the ID at the lower end of the inner sleeve 100.4. The lower mandrel split ring shoulder 200.24 fits in internal groove in upper end of lower mandrel 200.25 and is retained in place by the lower end of the lower actuator shoe 200.22 and provides an internal shoulder against which the lower actuator shoe 200.22 can be tightened. The lower mandrel 200.25 is made up to the lower end of the lower motor subassembly 200.18. The ID of the lower mandrel 200.25 contains the power/control cable 200.7 and forms part of the fluid flow path 100.5 through the e-Tractor. The OD of the lower mandrel 200.25 provides a sealing surface against which internal seal 100.11 in the lower gripper subassembly 100.2 seals against. The annulus between lower mandrel 200.25 OD and inner sleeve 100.4 ID form part of the fluid flow path 100.5 through the e-Tractor assembly 1000. The roller screw shaft subassembly 300 is made up in the screw housing 300.2 with the upper 200.11 and lower 200.18 motor subassemblies made up at each end. Torque is applied to each end of the roller screw shaft 300.1 by the motor subassemblies 200.11 and 200.18 generating a longitudinal force to the roller screw nut 200.1 in the tractor subassembly 100. The power/control cable 200.7 is run through the coiled tubing 6 from the surface A into and through the e-Tractor assembly 1000. The power/control cable 200.7 is connected to the upper 200.8 and lower 200.9 motor control electronics and is used to power and control the upper 200.3 and lower 200.4 motors.

(26) Alternatively, it will be understood that the electro-mechanical linear actuator assembly used in the inventive e-Tractor apparatus can be any type of assembly which converts rotational motion provided by one or more DC or AC motors in the tool to linear motion for setting the one or more gripper assemblies 100.1 and/or 100.2 and/or pulling or pushing the run-in string longitudinally within the well casing or the borehole.

(27) As seen in FIGS. 3-6 and as described above, in the embodiment of the inventive e-Tractor assembly 1000 depicted in FIG. 3, the inner body assembly 200.IB of the e-Tractor apparatus 1000 is longitudinally translatable within and relative to the outer housing 100.3 and preferably comprises: the upper mandrel 200.10, which is made up to the upper actuator shoe 200.26 of the upper motor sub-assembly 200.11, which is made up to the upper motor housing 200.15, which is made up to the upper screw housing cap 300.3, which is made up to the screw housing 300.2, which is made up to the lower screw housing cap 300.6, which is made up to the lower motor housing 200.31, which is made up to the lower actuator shoe 200.22 of the lower motor sub-assembly 200.18, which is made up to the lower mandrel 200.25.

(28) The upper mandrel 200.10 provides an upper end segment of the inner body assembly 200.1B which projects from the upper end of the outer housing 100.3, the upper gripper assembly 100.1 being positioned on the upper mandrel 200.10 such that the upper mandrel 200.10 is longitudinally translatable through the upper gripper assembly 100.1. The lower mandrel 200.25 provides a lower end segment of the inner body assembly 200.1B which projects from the lower end of the outer housing 100.3, the lower gripper assembly 100.2 being positioned on the lower mandrel 200.25 such that the lower mandrel 200.25 is longitudinally translatable through the lower gripper assembly 100.2.

(29) The upper motor subassembly 200.11 is comprised of the upper actuator shoe 200.26, upper motor control electronics 200.8, upper motor 200.3, upper gearhead 200.5, upper motor housing 200.15, upper battery 200.51 and the upper screw housing cap 300.3. The upper actuator shoe 200.26 is made up on the upper end of the upper motor housing 200.15 and has an ID bore through which the power/control cable 200.7 is run. An off-center hole runs the length of the upper actuator shoe 200.26 and is used to fill the center section of the power subassembly 200 with hydraulic oil 200.23. The upper end of the off-center hole has a pipe thread in which a pipe plug 200.50 is made up to contain the hydraulic oil 200.23. An external seal 200.28 at the upper end seals against the ID at the upper end of the inner sleeve 100.4. The upper motor control electronics 200.8 are used to control the upper motor 200.3 using power and control signals sent through the power/control cable 200.7. The upper battery 200.51 is used to provide a fail-safe means of releasing the grippers in the event cable power from the surface is lost such that retrieval and subsequent repair procedures are possible. The upper motor 200.3 is a DC motor used to apply torque to the upper gearhead 200.5. The upper gearhead 200.5 is used to reduce speed and increase torque that is applied to the upper end of the roller screw shaft 300.1. As depicted in FIG. 5, an upper gearhead output shaft 200.27 contains a torque key 200.28 to transfer torque from the upper gearhead 200.5 to an upper key coupling 200.29. The upper motor housing 200.15 is used to contain the upper motor 200.3, upper gearhead 200.5, and upper motor control electronics 200.8. The upper motor housing 200.15 has a radial hole and longitudinal external groove providing a path for the power/control cable 200.7. The upper motor housing 200.15 also has a radial slot at the lower end allowing it to be rotationally locked to the upper end of the upper screw housing cap 300.3. An internal upset at the lower end contains longitudinal holes through which cap screws 200.30 are inserted and made up in the upper gearhead 200.5. The upper screw housing cap 300.3 is made up in the lower end of the upper motor housing 200.15. The upper screw housing cap has a longitudinal slot that aligns with slots in the lower end of the upper motor housing 200.15 and upper end of the screw housing 300.2. The upper torque key 200.13 fits in the aligned slots and is held in place with torque key screws 200.14 made up through aligned radial holes in the upper torque key 200.13 and upper screw housing cap 300.3.

(30) The lower motor subassembly 200.18 comprises the lower screw housing cap 300.6, lower motor housing 200.31, lower gearhead 200.6, lower motor 200.4, lower battery 200.52, lower motor control electronics 200.9, and lower actuator shoe 200.22. The lower screw housing cap 300.6 is made up in the upper end of the lower motor housing 200.31 and has a longitudinal slot that aligns with slots in the upper end of the lower motor housing 200.31 and lower end of the screw housing 300.2. The lower torque key 200.21 fits in the aligned slots and is held in place with torque key screws 200.40 made up through aligned radial holes in the torque key 200.21 and lower screw housing cap 300.3. The lower motor housing 200.31 is used to contain the lower motor 200.4, lower gearhead 200.6, and lower motor control electronics 200.9. The lower motor housing 200.31 has a radial hole and longitudinal external groove providing a path for the power/control cable 200.7. It also has a radial slot at the upper end allowing it to be rotationally locked to the lower end of the lower screw housing cap 300.6. An internal upset at the upper end contains longitudinal holes through which cap screws 20032 are inserted and made up in the lower gearhead 200.6. The lower gearhead 200.6 is used to reduce speed and increase torque applied to the lower end of the roller screw shaft 300.1. As depicted in FIG. 6, the lower gearhead output shaft 200.33 contains a torque key 200.34 to transfer torque from the lower gearhead 200.6 to the lower key coupling 200.35. The lower motor 200.4 is a bi-directional electric DC or AC motor used to apply torque to the lower gearhead 200.6. The lower motor control electronics 200.9 are used to control the lower motor 200.4 using power and control signals sent through the power/control cable 200.7. The lower actuator shoe 200.22 is made up on the lower end of the lower motor housing 200.31. The lower actuator shoe 200.22 has an ID bore through which the power/control 200.7 cable is run. An off-center hole runs the length of the lower actuator shoe 200.22 and provides a path for hydraulic oil 200.23. The lower end is elongated and provides an OD sealing surface on which the pressure equalizing piston 300.7 is assembled.

(31) The roller screw shaft subassembly comprises the upper key coupling 200.29, the upper split ring shoulder 200.16 and retainer upper split ring shoulder retainer 200.20, upper grooved roller bearing 300.4, roller screw shaft 300.1, lower grooved roller bearing 300.5, and lower roller bearing spacer 300.10. As depicted in FIG. 5, the upper key coupling 200.29 has an internal slot into which keys 200.28 on the upper gearhead output shaft 200.27 and upper end of the roller screw shaft 300.1 are inserted to transfer torque from the upper gearhead 200.5 to the upper end of the roller screw shaft 300.1. The upper split ring shoulder 200.16 has multiple internal grooves which match multiple external grooves on the upper end of the roller screw shaft 300.1. The split ring shoulder 200.16 is fitted over the external grooves and the upper split ring shoulder retainer 200.17 is slipped over the upper split ring shoulder 200.16 to lock the shoulder in place on the roller screw shaft 300.1. The upper split ring shoulder 200.16 prevents upward movement of the upper grooved roller bearing relative to the roller screw shaft 300.1. The upper grooved roller bearing 300.4 is similar to a roller screw assembly except the rollers have multiple grooves instead of threads. The upper grooved roller bearing 300.4 transfers longitudinal loads between the roller screw shaft 300.1 and the screw housing 300.2 through the upper split ring shoulder retainer 200.17 and upper split ring shoulder 200.16. The roller screw shaft 300.1 contains external keys 200.28/200.34 at each end to transfer torque from the upper 200.5 and lower 200.6 gearheads. Multiple external grooves at each end allow the fitting of external split ring shoulders 200.16/200.19 and retainers 200.17/200.20 that prevent upward movement of the upper grooved roller bearing 300.4 and downward movement of the lower grooved roller bearing 300.5 relative to the roller screw shaft 300.1. The center of the roller screw shaft 300.1 contains an external roller screw thread that matches the threads on mating roller screw bearings within roller screw nut 200.1. The lower end of the roller screw shaft 300.1 is machined to the root diameter of the roller screw thread to allow assembly of the roller screw nut 200.1. The lower grooved roller bearing 300.5 is similar to a roller screw assembly except the rollers have multiple grooves instead of threads. The lower grooved roller bearing transfers longitudinal loads between the roller screw shaft 300.1 and screw housing 300.2 through the lower split ring shoulder 200.19 and the screw housing 300.2. The lower roller bearing spacer 300.10 is made up between the lower grooved roller bearing 300.5 ID and lower end of the roller screw shaft 300.1. The lower split ring shoulder 200.19 has multiple internal grooves which match multiple external grooves on the lower end of the roller screw shaft 300.1. The lower split ring shoulder 200.19 is fitted over the external grooves and the lower split ring shoulder retainer 200.20 is slipped over the shoulder 200.19 to lock the shoulder in place on the roller screw shaft 300.1. The lower split ring shoulder 200.19 prevents downward movement of the lower grooved roller bearing 300.5 relative to the roller screw shaft 300.1. The lower key coupling 200.35 has an internal slot into which keys 200.34 on the lower gearhead output shaft 200.33 and lower end of the roller screw shaft 300.1 are inserted to transfer torque from the lower gearhead 200.6 to the lower end of the roller screw shaft 300.1.

(32) In operation, the e-Tractor 1000 is run into the wellbore 1 with the upper 100.1 and lower 100.2 gripper assemblies collapsed to avoid contacting the casing 4 ID. Once the e-Tractor 1000 is in position, control signals and electric power are applied to the upper 200.3 and lower 200.4 motors through the power/control cable 200.7 and motor control electronics 200.8 and 200.9. The upper 200.3 and lower 200.4 motors will rotate in opposite directions at the same rpm to apply right hand torque to the roller screw shaft 300.1 through the upper 200.5 and lower 200.6 gearheads. Right hand rotation of the roller screw shaft 300.1 will apply an upward longitudinal load to the roller screw nut 200.1 which is transferred to the upper 100.9 and lower 100.10 lug retainers, pins 100.7, lug 100.8, and inner sleeve 100.4. The upward load is then transferred through the inner sleeve 100.4 to the upper grippers 100.GU in the upper gripper subassembly 100.1 and the outer sleeve 100.3. This movement and load is used to set the lower grippers 100.GL in the lower gripper subassembly 100.2 against the casing 4 ID. Once the lower grippers 100.GL are set, the load then starts pulling the power subassembly 200 and coiled tubing 6 distally downhole. At the end of the stroke, rotation of the upper 200.3 and lower 200.4 DC motors, upper 200.5 and lower 200.6 gearheads and roller screw shaft 300.1 is reversed, moving the roller screw nut 200.1, upper 100.9 and lower 100.10 lug retainers, lug 100.8, pins 100.7, inner sleeve 100.4, upper gripper subassembly 100.1, and outer sleeve 100.3 downward. This movement and load unsets the lower grippers 100.GL in the lower gripper subassembly 100.2 and repositions the tractor subassembly 100 back to its original position and ready for another stroke. In this operation, the grippers 100.GU in the upper gripper subassembly 100.1 have remained retracted.

(33) Stroke length and position of the tractor subassembly 100 relative to the power subassembly 200 is determined by the electronics 200.8/200.9 counting the motor 200.3/200.4 revolutions. This leads to the gearhead 200.5/200.6 output and roller screw shaft 300.1 revolutions from which longitudinal movement of the roller screw nut 200.1 can be determined.

(34) To push the coiled tubing 6 proximally (uphole) within wellbore 1, the above sequence is reversed with the grippers 100.GU in the upper gripper subassembly 100.1 being set and unset and the grippers 100.GL in the lower slip subassembly 100.2 remaining retracted.

(35) This operation, which utilizes a single e-Tractor assembly 1000, will generate start-stop, intermittent movement of the coiled tubing 6. Continuous movement of the coiled tubing 6 can be achieved by using two e-Tractors 1000 so that the first e-Tractor 1000 is applying a longitudinal force and thereby movement of the CT 6, while the second e-Tractor 1000 is resetting. As the e-Tractor assembly 1000 nears the end of its stroke and is slowing down, the second e-Tractor assembly 1000 is beginning its stroke and speeding up.

(36) Increasing the amount of longitudinal force available for CT movement in a continuous motion mode can be achieved by using a series of three or more e-Tractors. Likewise, the e-Tractors 1000 in a multi-assembly configuration can be switched to intermittent mode to utilize the pulling capacity of all the e-Tractors 1000 simultaneously. Continuous motion mode requires one e-Tractor assembly 1000 to be in its respective resetting sequence at all times to provide the continuous movement.

(37) The power subassembly 200 comprising the motor control electronics 200.8/200.9, motors 200.3/200.4, gearheads 200.5/200.6, roller screw shaft 300.1 and components of the tractor subassembly 100 in the inner sleeve 100.4 ID is filled with hydraulic oil 200.23 for lubricating and cooling the components. As hydrostatic and circulating pressure in the e-Tractor assembly 1000 ID increases, the pressures act on the lower end of the pressure equalizing piston 300.7 at the lower end of the lower motor subassembly 200.18 and move the equalizing piston 300.7 upward until the pressure of the hydraulic oil 200.23 is equal to that of the e-Tractor assembly 1000 ID. The equalizing piston 300.7 therefore eliminates the differential pressure across the internal 300.8 and external 300.9 seals that separate the hydraulic oil 300.7 from circulating fluid in the fluid flow path 100.5 of the e-Tractor 1000. The inner sleeve 100.4 ID-power subassembly 200 OD annulus encapsulated between the external seals 200.28/300.9 at each end of the power subassembly 200, the annulus between the DC motors 200.3/200.4 and gearheads 200.5/200.6 OD and motor housings 200.15/200.31 ID, holes and slots in the power subassembly 200 components allow for hydraulic oil 200.23 movement and pressure equalization in the power subassembly 200.

(38) Thus, the present invention is well adapted to carry out the objectives and attain the ends and advantages mentioned above as well as those inherent therein. While presently preferred embodiments have been described for purposes of this disclosure, numerous changes and modifications will be apparent to those in the art. Such changes and modifications are encompassed within this invention as defined by the claims.