Patent Publication Number: US-7896086-B2

Title: Logging tool deployment systems and methods without pressure compensation

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to the field of conveying equipment into wells, and more particularly to transporting equipment through an open end of a well that may contain pressure, while maintaining a pressure barrier at all times. 
     BACKGROUND OF THE INVENTION 
     Underground formations may exist at substantial elevated pressures posing challenges during exploration and production. In many instances, the pressures are great enough to produce an elevated pressure differential at a wellhead relative to ambient pressure. Failure to control such pressure differentials could result in an undesirable situation referred to as a blowout—an uncontrolled flow of reservoir fluids into the wellbore, and sometimes catastrophically to the surface. 
     Typically, a wellhead fixture including a pressure controller is mounted on the upper of the well to isolate wellbore pressures from an ambient pressure. During exploration and production, however, there remains a need to install and/or remove down-hole devices from the well. For example, logging tools designed to evaluate a formation and/or well conditions are inserted into the well, lowered to various depths as may be required during exploration, and later removed from the well, without jeopardizing crew, equipment, or production of the well. Presently, transfer of such logging tools through an open of a well under pressure can be accomplished using a pressure-controlling wellhead fixture configured to allow for transfer of the logging tool while maintaining a pressure barrier at the wellhead. One such class of fixtures is known generally as Christmas trees, including a configuration of valves and access fittings. Another such class of wellhead fixtures is known generally as blowout preventors (BOPs). Either class of wellhead fixtures can be configured with facilities to enable safe access for well intervention apertures. For example, BOPs can include an open channel with one or more reversibly sealable elements configured to open to allow passage of the logging tool, drill string, or thrust tube and closing thereafter to form a pressure barrier. 
     At least one such process of putting drill pipe or other down-hole devices into a well under pressure with BOPs maintaining a pressure barrier is referred to as snubbing. If the well has been closed with a so-called ram-type BOP, larger diameter features of the down-hole devices, such as tools or joints will not pass by the closed ram element. To keep the well closed another ram-type BOP or an annular BOP is included in series. The first ram element must be opened manually, then the down-hole device lowered until the larger diameter feature is just below the ram element, and then closing the first ram element again. The second ram element is then opened allowing the larger diameter element to pass. This procedure is repeated whenever a larger diameter feature, such as a tool or tool joint must pass by a ram-type BOP. Exercising such care in dealing with larger diameter features by snubbing is generally a time consuming proposition. 
     If only an annular BOP has been closed rather than the ram-type BOP, the drill pipe or other down-hole device may be slowly and carefully lowered into the wellbore, since the annular BOP opens slightly to permit the larger diameter feature to pass through. In snubbing operations, the pressure in the wellbore acting on the cross-sectional area of the tubular element (i.e., down-hole device) can exert sufficient force to overcome the weight of a drill string, so the string must be pushed (or “snubbed”) back into the wellbore. Such thrust can be provided by a coil tubing unit pushing to a proximal end of a tool or axial array of tools within the wellbore. Such an axial array of tools is referred to as a tool string. 
     Applying down-hole axial thrust to such an elongated tool or string of tools generally requires the use of a rig or derrick providing lateral support to the tool or string of tools suspended above the wellhead fixture. Such strings are typically assembled vertically above a wellhead fixture before insertion, requiring tall rigs. The rig itself is constructed above the open end of the wellhead fixture and directed along the wellbore axis and may extend from 10 to 100 feet or more, depending upon the length of the tool or tool string. An array of multiple interconnected tools is referred to as a tool string. Such strings are typically assembled vertically above a wellhead fixture before insertion, requiring tall rigs. Unfortunately, construction of such a rig or derrick adds to time and complexity on-site during any such deployment and extraction procedure. The rigs must be provided, constructed, used, deconstructed and removed. Such on-site access time can be quite expensive, particularly for offshore applications, thus any procedures leading to delay, such as snubbing and rig construction, are highly undesirable. 
     SUMMARY OF THE INVENTION 
     Systems and processes are described for facilitating rapid transfer of down-hole devices through a pressure controlling wellhead fixture capping a well under pressure, without requiring a rig and without jeopardizing operators, equipment, or the well itself. An adaptive seal assembly is provided that is sized and shaped to accommodate down-hole devices of varying cross section. The assembly includes a housing with a mating flange for coupling the open end to a reversibly sealable wellhead fixture. One or more dynamic sealing elements are disposed between the housing and the down-hole device forming a pressure barrier between the well and ambient environment. Once the pressure barrier has been established, any reversible seals in the wellhead fixture can be opened, allowing for substantially unhindered transfer of the down-hole device in a preferred direction, either into or out of the well. Preferably, the dynamic seal element is configured to maintain a seal against varying cross section of the down-hole device as it is translated along axis. 
     One embodiment of the invention relates to a process for transferring a down-hole device across an open end of a well under pressure. The process includes attaching one end of an adaptive seal assembly to an open end of the well under pressure. The adaptive seal assembly is accessible at both ends and defines a passage therethrough. The down-hole device is positioned at least partially within the passage defined by the adaptive seal assembly. An interior region defined between an interior surface of a housing of the adaptive seal assembly and an adjacent periphery of the down-hole device is sealed. The seal provides a barrier isolating an elevated wellbore pressure within the well from an ambient pressure. An axial force is applied to a proximal end of the down-hole device, translating the down-hole device through the open end of the well under pressure. The seal between the housing and the down-hole device is automatically readjusted responsive to any cross sectional variations of the down-hole device. Readjustment of the seal maintains pressure isolation as the down-hole device is translated through the assembly. 
     Another embodiment of the invention relates to a system for transferring a down-hole device across an open end of a well under pressure. The system includes an adaptive seal assembly having a housing with an enclosed side wall open at both ends and defining a passage therethrough. The housing includes a mounting flange at one end, configured for securely mounting the adaptive seal assembly in relation to the open end of the well under pressure. At least one dynamic seal element is positioned within an interior region defined between an interior surface of the enclosed side wall and an adjacent periphery of the down-hole device. The dynamic seal element is configured to seal an elevated pressure in the wellbore with respect to ambient pressure. The assembly also includes an actuator configured to adjust the at least one dynamic seal element between open and closed configurations. A sealing engagement can be maintained by readjustment of the dynamic seal element allowing pressure isolation to be maintained as the down-hole device is translated through the assembly. 
     Yet another embodiment of the invention relates to a process for transferring a down-hole device across an open end of a well under pressure. The process includes at least one of robotically transferring the down-hole device between a storage location and the open end of the well under pressure and robotically positioning the down-hole device relative to the open end of the well under pressure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. 
         FIG. 1  is a sectional schematic view of one embodiment of an adaptive seal assembly according to the present invention. 
         FIG. 2  provides a flow diagram illustrating an exemplary procedure for transferring a device through an opening of a well under pressure according to the present invention. 
         FIG. 3  is a sectional schematic view illustrating in more detail an embodiment of a dynamic seal element according to the present invention. 
         FIG. 4A  and  FIG. 4B  illustrate a simplified axial end view of the reversible dynamic seal of  FIG. 3 . 
         FIG. 5A  and  FIG. 5B  illustrate an axial end view of the reversible dynamic seal of  FIG. 3  mounted within one embodiment of a housing. 
         FIG. 6A  and  FIG. 6B  illustrate a cross sectional elevation view of the reversible dynamic seal element of  FIG. 3  mounted within the embodiment of a housing. 
         FIG. 7  is a plan view of an embodiment of a dynamic seal actuator according to the present invention. 
         FIG. 8  is a cross-section schematic diagram of one embodiment of an adaptive sealing thrust assembly according to the present invention. 
         FIG. 9  is a perspective view of an embodiment of an exemplary reversible seal of the adaptive sealing thrust assembly of  FIG. 8 . 
         FIG. 10A  through  FIG. 10L  together illustrate the adaptive sealing thrust assembly of  FIG. 8  applying thrust to a tool according to the present invention. 
         FIG. 11  is a schematic diagram of another embodiment of an adaptive sealing thrust assembly according to the present invention. 
         FIG. 12A  through  FIG. 12H  together illustrate the adaptive sealing thrust assembly of  FIG. 11  applying thrust to a tool according to the present invention. 
         FIG. 13A  and  FIG. 13B  are perspective views of an embodiment of a robotic system for automatically manipulating a wellbore deployment system during use according to the present invention. 
         FIG. 14  is a side elevation view of an embodiment of a coiled tubing system for injecting or removing coiled tubing from a borehole according to the present invention. 
         FIG. 15  is a side elevation view of another embodiment of a coiled tubing system for injecting or removing coiled tubing from a borehole according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An adaptive seal assembly including at least one dynamic seal is provided in a housing mountable to a wellhead fixture. The adaptive seal assembly includes facilities to vary an aperture of the dynamic seal to maintain a pressure along a wellbore side of the reversible seal including devices having variations in cross section when translated along a wellbore axis. The reversible seal is sized and shaped to accept any cross section of the down-hole device. Having sealed against wellbore pressure, safety sealing features provided by the wellhead fixture are necessary. Thus, insertion or extraction of the device can be accomplished rapidly, without the need for snubbing. Once transfer of the tool has been completed, the wellhead fixture can be re-sealed either against the device, a coil tube or drill string applying thrust to the device, or completely sealed, allowing the well to resume normal operations. 
     The dynamic seal includes an aperture than can be opened wide enough to allow the widest portion of a device to pass. Each tool of a tool string can be inserted individually with interconnections performed at the wellhead fixture. Accordingly, there is no need for a separate rig or derrick, since the tools are supported in the assembly. In some embodiments, support equipment can be provided to manipulate the tools and chamber, such as a crane or one or more robotic arms. 
     An exemplary embodiment of an adaptable seal assembly  25  is illustrated in  FIG. 1 . The adaptive seal assembly  25  includes a housing  34  having a user access aperture  36  at one end and a wellbore access aperture  38  at an opposite end. Preferably the housing  34  includes a mounting flange  40  adjacent to the wellbore access aperture end adapted for attachment to an open end of a wellhead fixture  30 . When the housing  34  is attached to an open end of the wellhead fixture  30 , the user access aperture  36  is also aligned with the wellbore access aperture  38 , both positioned along an axis of the wellbore  32 . 
     The adaptive seal assembly  25  includes an array of dynamic sealing elements  42   a ,  42   b ,  42   c  (generally  42 ). Each dynamic sealing element  42  of the array is disposed at a respective location along the wellbore axis. In some embodiments, the dynamic sealing elements  42  are annular structures including a central aperture centered along the wellbore axis. The dynamic sealing elements  42  are actuatable such that the dimensions of the internal aperture vary when actuated between open and closed positions. When a down-hole device such as a logging tool  46  is inserted within the central aperture of the dynamic sealing element  42 , the dynamic sealing element  42  can be actuated to close against an external surface of the logging tool  46  forming a seal along a perimeter of an adjacent cross section of the tool  46 . 
     Each of the dynamic seal elements  42  can be held in place with respect to the housing  34 . For example, each of the dynamic seal elements can be supported by a respective dynamic seal support bracket  44   a ,  44   b ,  44   c  (generally  44 ) securely attached to the housing  34 . The dynamic seal supporting brackets  44  maintain the relative axial positioning of the dynamic seal elements  42  while allowing the dynamic seal elements  42  to vary between open and closed positions. 
     In some embodiments, one or more of the dynamic seal elements  42  include a respective compliant seal  43  positioned along an internal perimeter of its respective central aperture. The compliant seal  43  is pinched between the perimeter of the internal aperture of the dynamic seal  42  and the adjacent exterior surface of the logging tool  46 . For cylindrical applications, the compliant seal can include an annular structure formed of an elastomeric material extending for a restricted length along the wellbore axis. When the dynamic seal  42  is in a closed position, the compliant seal  43  forms a sufficient seal to maintain a pressure barrier between a wellbore pressure P 1  along one side of the dynamic seal  42  and a different pressure along an opposite side of the dynamic seal  42 , without requiring the dynamic seal to clamp hard against the external surface of the logging tool  46 . Consequently, the logging tool  46  is slidable along the wellbore axis when a thrust is applied, while still maintaining a seal. One or more sealing members  49  can be included between one or more of the dynamic seal elements  42  and an adjacent surface of the housing  34  to maintain a pressure differential thereacross. 
     The dynamic seal elements  42  can be formed as a closed-loop kinematics mechanism having the following capabilities: (i) converts the area of a circle into a ring that has an outer diameter larger than the initial diameter of the circle, and (ii) modifies the inner radius of a cylindrical device enlarging or reducing its diameter. The closed-loop kinematics mechanism can be formed from a series of basic linkages that pivot with respect to each other. As one of the rigid linkages pivots with respect to the other, the other pairs of rigid linkages of the closed-loop mechanism similarly pivot. Operation of the dynamic seal elements  42  can be controlled by one or more of the shapes of the rigid linkages and the locations of the pivots. Such closed-loop mechanisms can be referred to as deployable structures, which are described in more detail in U.S. patent application Ser. No. 11/247,918, entitled “Mechanical crawler”, filed on Oct. 11, 2005, commonly owned and incorporated herein by reference in its entirety. Although the exemplary embodiments are directed to cylindrical applications, dynamic seal elements can be provided having internal apertures shaped to accommodate polygonal tools (e.g., rectangular), ellipsoidal tools, and complex-shaped tools having perimeters with a combination of linear and curvilinear shapes. 
     The adaptive seal assembly  25  includes at least one actuator  50  configured to actuate the actuatable dynamic seal elements  42  between open and closed positions. In the exemplary embodiment, the adaptive seal assembly  25  includes a single actuator  50 , such as a rotary motor positioned at one end of an elongated drive shaft  52 . An opposite end of the drive shaft  52  is retained in a bearing  54  allowing the drive shaft  52  to rotate when a torque is provided by the motor  50 . A respective transmission  56   a ,  56   b ,  56   c  (generally  56 ) is provided between the elongated drive shaft  52  and each of the dynamic seal elements  42 . Each of the dynamic seal elements  42  can include a respective dynamic seal drive shaft  58   a ,  58   b ,  58   c  (generally  58 ) coupled to the respective transmission  56 . Rotation of the elongated drive shaft  52  rotates the dynamic seal drive shaft  58  linked through the transmission  56  thereby actuating the respective dynamic seal element  42  between open and closed configurations depending upon direction of the rotation. 
     In some embodiments, the adaptive seal assembly  25  is automatically controllable. For example, a controller  62  provides commands to the actuator  50 . One or more of the dynamic seal elements  42  can include a respective sensor  60   a ,  60   b ,  60   c  (generally  60 ). The sensors  60  are configured to provide an indication of the seal between the internal aperture of a respective dynamic seal element  42  and an adjacent external perimeter of the logging tool  46 . In some embodiments, the sensor  60  can be a strain gauge provided within or along a surface of the compliant seal member  43 . The strain gauge measures strain which is indicative of the seal with a greater strain indicating a tighter seal. One or more of the sensors  60  can be coupled to the controller  62 . The controller  62  can be configured to operate in a feedback-loop control automatically adjusting the actuation of the one or more dynamic seal elements  42  as a function of input received from the sensors  60 . The one or more actuators  50  and sensors  60  can be coupled to a remote controller  62  through a wire, an optical fiber, or a wave guide. In some embodiments, the one or more of the actuators  50  and sensors  60  can be coupled to the remote controller  62  via a wireless communications link. In some embodiments, the controller  62  is not remote, but provided within the housing  34  for a self-contained assembly  25 . 
     An exemplary process  70  for transferring a down-hole device such as a logging tool through an open end of a well under pressure is illustrated in  FIG. 2 . A top end of the well typically includes one or more wellhead fixtures. The wellhead fixtures generally include one or more reversible seals adjustable to establish a pressure barrier between a wellbore pressure and ambient pressure at the wellhead. To transport tools into and out of the well according to the present invention, an adaptable seal assembly is first attached to an open end of the wellhead fixture ( 72 ). The adaptable seal assembly includes a user access aperture and a wellbore access aperture, each positioned respectively at opposite ends of the assembly, such as the exemplary device illustrated in  FIG. 1 . An end portion of a logging tool is at least partially inserted into one of the apertures of the adaptable seal assembly ( 74 ). For example, in an insertion process for inserting a logging tool into the open end of the well, a distal end portion of the logging tool is inserted into the user access aperture of the adaptable seal assembly. For a removal process, a portion of the logging tool is inserted into the wellbore access aperture. 
     The adaptable seal assembly includes one or more dynamic seal elements. At least one of the dynamic seal elements is adjusted to form a seal against an adjacent perimeter along an external surface of the end portion of the logging tool ( 76 ). The dynamic seal can be an annular device extending in a plane perpendicular to the wellbore access. Once a seal has been established, an elevated wellbore pressure is isolated from ambient pressure surrounding the wellhead fixture. Once such a pressure barrier has been established at the adaptive seal assembly, any reversible seals provided within the wellhead fixture can be opened providing access to the depths of the wellbore ( 77 ). 
     A thrust is applied to the logging tool urging it in a preferred direction along the wellbore axis. The thrust translates a substantial portion of the logging tool through the adaptable seal assembly ( 78 ). Preferably one or more of the dynamic seal elements are automatically adjustable or readjusted to maintain a seal against an external surface of varying cross-section of the logging tool as the tool is translated along the axis of the well ( 80 ). Preferably such readjustment of the dynamic seals is accomplished automatically such that the seal is adjusted to maintain a controlled pressure against the adjacent external surface of the logging tool. Such pressure can be regulated using a pressure sensor at the seal and a feedback controller configured to adjust the dynamic seal actuator according to the sensed pressure thereby maintaining a pressure within a preferred pressure range. 
     A more detailed view of an exemplary reversible seal  42 ′ of an exemplary adaptive sealing assembly  25 ′ is provided in the sectional view of  FIG. 3 . In some embodiments, the reversible seal  42 ′ is formed using a dynamic-sealing, deployable structure  45 . The deployable structure  45  includes at least three pivotally-joined double lever assemblies forming an enclosed mechanical linkage. Such reversibly-expandable structures are described in more detail in U.S. patent application. Ser. No. 11/962,256, entitled “System and Methods for Actuating Reversibly Expandable Structures,” filed on Dec. 21, 2007, and incorporated herein by reference in its entirety. Although the exemplary embodiments are directed to cylindrical applications, reversibly-expandable structures can be provided having internal apertures shaped to accommodate polygonal tools (e.g., rectangular), ellipsoidal tools, and complex-shaped tools having perimeters with a combination of linear and curvilinear shapes. 
     In the illustrative embodiment, the enclosed linkage  45  forms an annular structure disposed between an interior surface of a housing  34 ′ and an outer surface of a tool  46  positioned therein. An internal aperture of the annular enclosed mechanical linkage  45  is configured selectively to expand and contract when one or more of the double lever assemblies are manipulated. In the illustrative embodiment, an outer perimeter of the annular structure  45  remains in sealable contact with the inner wall of the housing  34 ′ while an inner perimeter of the annular structure  45  is allowed to vary between maximum and minimum diameters according to adjustment of the mechanical linkage. Thus, the annular structure  45 , when engaging the tool  46  with its inner perimeter forms a seal between the inner wall of the housing  34 ′ and the outer surface of the tool  46 . In some embodiments, a sealing member  43 ′ is inserted between the inner perimeter of the annular structure  45  and the outer surface of the tool  46 . For example, an elastomeric material  43 ′ can be applied or fixed to the inner perimeter of the annular structure  45  such that when the inner perimeter is enclosed to engage the outer surface of the tool  46 , the elastomeric material  43 ′ is entrapped between the inner perimeter and the tool  46  forming a fluid-tight seal. In some embodiments, the elastomeric material  43 ′ is segmented around the inner perimeter to provide a continuous seal when closed, but allowing substantial expansion without damage to the elastomeric material  43 ′. In some embodiments, the elastomeric material includes multiple layers of varying compliance. 
     A pressure sensor  60 ′ such as a strain gauge can be positioned between the inner perimeter and the outer surface of the tool  46  as shown. For example, the pressure sensor  60 ′ can be impregnated within the elastomeric material and configured to sense a strain indicative of the pressure exerted between the inner perimeter of the annular structure  45  when engaging the outer surface of the tool  46 . Alternatively or in addition, the pressure sensor  60 ′ can be included between the outer perimeter of the annular structure  45  and the interior surface of the housing  34 ′, once again sensing pressure exerted when the reversible seal  42 ′ is adjusted to form a seal. One or more pressure sensors  60 ′ can be coupled to an external pressure monitor (not shown) providing the user with an indication of the pressure exerted. More preferably, the one or more pressure sensors  60 ′ can be connected to a controller in a feedback control loop configuration such that the controller adjusts the reversible seal  42 ′ in response to monitored output pressure provided by the pressure sensor  60 ′. The controller adjusts the inner perimeter of the reversible seal  42 ′ until a predetermined sealing pressure is obtained. Once the desired sealing pressure is obtained, further adjustment of the annular structure terminates. 
     In some embodiments, one or more sealing members  81  are provided along the outer edge of the annular structure  45  and the inner surface of the housing  34 ′. As shown, these may include one or more elastomeric seals, washers, or o-rings  81  disposed between the outer perimeter of the deployable structure  45  and a flange  44 ′ coupled to the inner wall of the housing  34 ′. 
     A planar view along the wellbore axis of an exemplary dynamic seal having an annular shape is illustrated in an open position in  FIG. 4A  and in a closed position in  FIG. 4B . In an open position, the dynamic seal  45  defines an internal aperture having an internal diameter ID 1  and an external diameter of OD 1 . In a closed configuration shown in  FIG. 4B , the internal aperture has an internal diameter ID 2  less than the open internal diameter ID 1  and an outside diameter OD 2  that can be the same, greater, or less than the open outside diameter OD 1 . 
     As shown in  FIG. 6A , at least a portion of the dynamic seal  45  is retained within a bracket  44 ′ retaining the dynamic seal  45  in a fixed position relative to the housing  34 ′. As shown in  FIG. 5A , the dynamic seal  45  when opened can be at least partially or entirely contained within the bracket  44 ′. In the open position, a space  92  can be provided between an interior perimeter of the dynamic seal  45  and an adjacent external surface of the logging tool  46 . That is, the inside diameter of the open dynamic seal ID 1  is greater than an adjacent outside diameter of the logging tool  46 . Thus, in an open configuration, the logging tool is allowed to pass freely along the wellbore axis with respect to the dynamic seal  45 . 
     When closed, an internal perimeter of the dynamic seal  45  is urged against an adjacent external surface of the logging tool  46 . Thus, the internal diameter of the closed dynamic seal ID 2  is approximately equal to an external diameter of the logging tool  46 . Preferably, the dynamic seal  45  extends within the plane perpendicular to the wellbore axis to occlude any opening between the logging tool  46  and the bracket  44 ′ or housing  34 ′. A cross-sectional side view is shown in  FIG. 6B  in which the dynamic seal  45  is closed against an adjacent external perimeter of the logging tool  46  with at least an outer portion of the dynamic seal  45  still residing within the bracket  44 ′. The bracket  44 ′ and closed dynamic seal  45  together form a pressure barrier along the wellbore axis. In some embodiments, one or more sealing members  81  are provided to seal the outer portion of the dynamic seal  45  against the bracket. When such a seal is established, an elevated well pressure P 1  is maintained against a different ambient pressure P 2 . 
       FIG. 7  illustrates one embodiment of an actuator  83  configured to manipulate one of the joined double lever assemblies of the mechanical linkage of the reversible seal  42 ″, thereby causing the reversible seal  42 ″ to change its dimensions. The exemplary embodiment includes a driving wheel  82  providing a torque positioned adjacent to a driven wheel  84  coupled to one of the double lever assemblies. When the driven wheel  84  is rotated, it causes a corresponding rotation of the double lever assembly. The driving wheel  82  and driven wheel  84  can include pulleys about which a drive belt  86  is coupled. The driving wheel  82  can be connected to an electric motor providing torque to drive the driven wheel  84 . Rotation of the driving wheel  82  rotates the drive belt  86 , which also rotates the driven wheel  84 . The driven wheel  84  typically moves in relation to the driving wheel  82  by expansion and contraction of a reversible seal  43 ″. In the exemplary embodiment, the driven wheel  84  moves along a straight line path between the centers of the driving wheel  82  and the driven wheel  84 . In some embodiments, a third wheel  88  is also provided in communication with the drive belt  86  such that the center of the third wheel  88  is displaceable in a direction non-parallel to the line joining the driving wheel  82  and the driven wheel  84  as illustrated. Preferably, the third wheel  88  is rotatably coupled to a device that displaces the third wheel with respect to the driving wheel  82  and the driven wheel  84  to maintain tension of the belt  86  when the driven wheel  84  moves toward or away from the driving wheel  82 . In some embodiments, the driving wheel  82 , the driven wheel  84 , and the third wheel  88  can be replaced by cogs and the belt  86  replaced by a chain, to the same effect. 
     In some embodiments, the adaptive seal assembly is configured to apply a thrust to a down-hole device while also maintaining a peripheral seal about an outer surface of the down-hole device. One such class of adaptive seal assemblies providing an internal thrust capability is illustrated in  FIG. 8 . The adaptive seal assembly  100  includes a housing  102  having a user access aperture  103  and a wellbore access aperture  105 . A down-hole device, such as a logging tool  46 , can be translated through either of the user access aperture  103  or the wellbore access aperture  105 , depending upon the direction of travel, through an internal cavity of the housing  102 , and out the opposite side of the adaptive seal assembly  100 . 
     In the exemplary embodiment, the adaptive seal assembly  100  includes six dynamic sealing elements  104   a  through  104   f  (generally  104 ). Each of the dynamic seal elements  104  includes an annular structure having a central aperture through which the logging tool  46  can traverse. Each of the dynamic seal elements  104  is also configured to vary its internal aperture between open and closed positions. In an open position, the dynamic seal element  104  is open substantially such that the logging tool  46  can pass through its central aperture without any hindrance. In a closed position, the central aperture of the dynamic seal element  104  is urged against an adjacent outer surface of the logging tool  46  forming a seal thereabout. In at least some embodiments, each dynamic seal element  104  resides in a parallel plane, orthogonal to and spaced apart along a longitudinal axis of the logging tool  46 . The dynamic seal element  104  can remain orthogonal to the longitudinal axis during transitions between open and closed positions. One or more actuators  106   a  through  106   f  (generally  106 ) are provided to independently adjust the dynamic seal elements  104  between open and closed positions. 
     To provide longitudinal thrust to the logging tool  46 , one or more of the dynamic seal elements  104  is configured such that it is translatable along the longitudinal axis of the logging tool  46 , at least when the dynamic seal element  104  is in a closed position. Travel distances of each of the dynamic seal elements  104  are generally limited by spacing of other adjacent dynamic seal elements  104 . Preferably, the at least one of the dynamic seal elements being translated clamps to the tool, such that the tool is also translated by a corresponding distance. 
     The adaptive seal assembly  100  also includes one or more translation actuators  108   a  through  108   f  (generally  108 ). The exemplary embodiment includes eight such translation actuators, one for each of the eight dynamic seal elements  104 . In some embodiments, each of the translation actuators  108  is configured to translate a respective one of the dynamic seal elements at limited distance δ along the longitudinal axis of the logging tool  46 . Such translation can be provided by a rotating threaded shaft linked to a mounting bracket supporting the dynamic seal element  104 . Preferably, the mounting bracket is slidable along the longitudinal axis of the logging tool  46 . Rotation of the threaded shaft urges the respective mounting bracket in a longitudinal direction according to the direction of rotation of the shaft. Alternatively or in addition, one or more of the dynamic seal elements is bendable allowing a perimeter of the internal aperture to translate a limited distance along the longitudinal axis according to bending of the dynamic seal  104 . As illustrated, a third dynamic seal element  104   c  is configured in a closed position and bent downward while adjacent dynamic seal  104   d  is in a closed position. By a sequencing of the reversible seal actuators  106  and the translation actuators  108 , a controlled thrust can be applied to the logging tool  46 . 
     An exemplary embodiment of a dynamic seal  104   a  is schematically illustrated in cross section in  FIG. 9 . The dynamic seal  104   a  includes a deployable structure  114 . The deployable structure  114  can include one or more apertures  116   a ,  116   b  to allow passage of one or more elongated threaded drive shafts  118   a ,  118   b  therethrough. The deployable structure  114  can be an annular structure similar to those described above in relation to the reversible seals. The annular structure  114  includes an internal perimeter  110  adapted to frictionally engage an adjacent outer surface of the logging tool  46 . Once clamped, a translation actuator ( FIG. 8 ) (i.e., vertical) urges the reversible seal  104   a , now clamped to the logging tool, in a preferred direction according to the rotation of the extended threaded drive shafts  118   a ,  118   b . The slots  116   a ,  116   b  allow for travel of the deployable structure  104   a  within the housing  102  ( FIG. 8 ). 
       FIG. 10A  through  FIG. 10L  together illustrate a sequencing of the dynamic seal elements  104  in a controlled manner for applying a thrust to the logging tool  46  urging the logging tool  46  in a downward direction through the internal cavity of the adaptive seal assembly  100 . In the exemplary embodiment, there are twelve phases, phase  0  through phase  11 . Referring to  FIG. 10A  illustrating phase  0 , a first dynamic seal element  104   a  is illustrated in a closed position while a sixth dynamic seal element  104   f  is illustrated in a closed and translated position. A zero reference is drawn at the top of the logging tool  46  for reference as the logging tool is translated throughout the different phases. Referring next to  FIG. 10B , the sixth dynamic seal element  104   f  has opened, while the first dynamic seal element  104   a , still in a closed position, has translated downward by an amount δ, the logging tool being clamped by the first dynamic seal element  104   a  is also translated by a corresponding amount δ. In a third phase shown in  FIG. 10C , the second dynamic seal element  104   b  is closed to engage an outer surface of the logging tool  46  while all other dynamic seal elements can remain in the same position. In a fourth phase, the first dynamic seal element  104   a  opens while the second dynamic seal element  104   b  is translated by an amount δ also translating the logging tool  46  by the same amount δ, now 2 δ from the Ø reference position. 
       FIG. 10E  illustrates a fifth phase in which a third dynamic seal element  104   c  is closed to engage an outer surface of the logging tool  46 . The process is repeated for the lower dynamic seal elements in lower phases, essentially walking the logging tool  46  downward through the internal cavity of the adaptive seal assembly  100 . By the end of the twelfth phase illustrated in  FIG. 10L , the logging tool  46  has traveled a distance of six δ. In each phase of the sequence, at least one of the dynamic seal elements remains closed about the periphery of the logging tool  46  to maintain a pressure barrier between the user access aperture and the wellbore access aperture of the adaptive seal assembly  100 . 
     The configuration of dynamic seal elements not involved in the particular step of the respective phase are illustrated in an open position, away from the logging tool  46 . In some embodiments, one or more of these unused dynamic seal elements  104  can remain in a closed configuration without clamping the tool contributing to sealing against the logging tool while allowing translation of the tool. Sequencing of the dynamic seal elements  104  can be accomplished by a remote controller coupled to the actuators  106 ,  108  and preprogrammed with a preferred sequence. Thrust to the logging tool  46  can be provided in an opposite direction by essentially reversing the ordering of the phases. In some embodiments, other sequences of the dynamic seal elements can be used. Although six dynamic seal elements are provided in the illustrative embodiment, different numbers of dynamic seal elements can be provided to the same effect, with at least two elements to provide a step capability while maintaining a seal against the logging tool  46 . 
     Another class of adaptive seal assemblies also including a thrust capability is illustrated in  FIG. 11 . The adaptive seal assembly  120  includes a housing  102  having a user access aperture  123  and a wellbore access aperture  125 . A down-hole device, such as a logging tool  46 , can be translated through either of the user access aperture  123  or the wellbore access aperture  125 , depending upon the direction of travel, through an internal cavity of the housing  122  and out the opposite side of the adaptive seal assembly  120 . 
     In the exemplary embodiment, the adaptive seal assembly  120  includes eight dynamic sealing elements  124   a  through  124   h  (generally  124 ). Each of the dynamic seal elements  124  includes an annular structure having a central aperture dimensioned to accommodate passage therethrough of a maximum cross section of a logging tool  46  can traverse. Each of the dynamic seal elements  124  is also configured to vary its internal aperture between open and closed positions. In an open position, the dynamic seal element  124  spaced away from the logging tool  46  leaving an open space between the perimeter of the aperture and a tool  46  disposed therein. In a closed position, the central aperture of the dynamic seal element  124  is urged toward the outer surface of the logging tool  46  substantially closing any open space. In at least some embodiments, each dynamic seal element  124  resides in a parallel plane, orthogonal to and spaced apart along a longitudinal axis of the logging tool  46 . The dynamic seal element  124  can remain orthogonal to the longitudinal axis during transitions between open and closed positions. 
     In some embodiments, a single actuator, such as a rotary motor  126  rotates an elongated drive shaft  128 , held at an opposite end by a rotary bearing  130 . The drive shaft  128  can be coupled to each of the dynamic seal elements  124  through a respective transmission, transferring motor torque to the dynamic seal element  124 . Sequencing of the different dynamic seal elements  124  can be accomplished by an initial positioning, or keying of the dynamic seal elements  124  with respect to each other. As the motor is turned, the relative positioning of the dynamic seal elements is maintained. In other embodiments, more than one actuators are provided. For example, each dynamic seal element  124  can be configured with a respective actuator to independently adjust the dynamic seal elements  124  between open and closed positions. A controller can be used to provide a control signal to each of the dynamic seal elements  124 , maintaining a relative positioning of the dynamic seal elements throughout the phase sequence. 
     In some embodiments, the assembly  120  also includes an elongated, flexible tubular membrane  132  disposed between the logging tool  46  and the internal apertures of the dynamic seal elements  124 . Preferably, the tubular membrane  132  is attached to each of the dynamic seal elements  124 , such that the membrane flexes with opening and closing of the dynamic seal elements  124 . With such a configuration, thrust can be generated in the logging tool  46  by expanding and contracting each of the dynamic seal elements  124  according to a controlled sequence of expansions and contractions. In some embodiments, the sequence of expansions and contractions form an undulating wave directed along the wellbore axis. When a fluid  134  is trapped between the tubular membrane  132  and the outer surface of the logging tool  46 , the annular wave entrapping a portion of the fluid pushes against the fluid trapped therein, causing the logging tool  46  to be displaced along the wellbore axis, in the direction of the traveling wave according to thin film fluid mechanics. The first three dynamic seal elements  124   a ,  124   b ,  124   c  are sequenced to form a wave entrapping fluid  134  in a pocket formed in the tubular membrane  132 . Exemplary devices are described in U.S. patent application Ser. No. 11/247,918, entitled “Mechanical crawler”, filed on Oct. 11, 2005. 
     Referring now to  FIG. 12A  through  FIG. 12H  together, a sequencing of the dynamic seal elements in a controlled manner is illustrated for applying a thrust to the logging tool  46 , urging the logging tool in a downward direction through the internal cavity of the adaptive seal assembly  120 . In the exemplary embodiment, there are eight phases, phase  0  through phase  7 . Referring to  FIG. 12A  illustrating phase  0 , a first and third dynamic seal elements  124   a  and  124   c  are illustrated in a partially open position, a second dynamic seal element  124   b  is illustrated in a full open position, and the remainder of the dynamic seal elements  124   d  through  124   h  are in a closed position. The first three dynamic seal elements  124   a ,  124   b ,  124   c  form an annular wave open at the top end to allow a fluid to enter and fill a void caused by the wave. A zero reference is drawn at the top of the logging tool  46  for reference as the logging tool is translated through the different phases. 
     Referring next to  FIG. 12B , the first through fourth dynamic seal elements  124   a  through  124   d  form a closed annular wave. Essentially, the wave created in phase Ø has progressed downward by an amount δ, the spacing between adjacent dynamic seals, the logging tool also being translated by a corresponding amount δ according to thin film principles. The process is repeated for subsequent phases illustrated in  FIG. 12C  through  FIG. 12H  with the wave motion urging the logging tool  46  downward through the internal cavity of the adaptive seal assembly  120 . By the end of the twelfth phase illustrated in  FIG. 12H , the logging tool  46  has traveled a distance of about seven δ. Thus, an axial thrust can be produced along the wellbore axis by dynamic seal elements variations in planes orthogonal to the axis. In each phase of the sequence, at least one of the dynamic seal elements remains closed about the periphery of the logging tool  46 . This insures that a pressure barrier is established between the user access aperture and the wellbore access aperture of the adaptive seal assembly  120 . Sequencing of the dynamic seal elements  124  can be accomplished by a remote controller coupled to the actuator  126  and preprogrammed with a preferred sequence. Thrust to the logging tool  46  can be provided in an opposite direction by essentially reversing the order of the phases. Although eight dynamic seal elements are provided in the illustrative embodiment, different numbers of dynamic seal elements can be provided to the same effect. 
     Referring now to  FIG. 13A  and  FIG. 13B , a robotic system  250  can be provided to assist in manipulation and positioning of at least one of the down-hole device  252  and the adaptive seal assembly  254 . A pick-and-place robotic system  250  can include a base member  258  and a positionable arm  260  attached at one end to the base unit  258 . A releasably grasping fixture  268  is provided at an opposite end of the arm  260 . In some embodiments, the releasably grasping fixture can be a clamp or a grasper  262  as shown. The elements of the pick-and-place robotic system  250  are configured to provide multiple degrees of freedom. In some embodiments, the robotic system  250  includes a controller  264  in electrical communication with the system  250 . The controller  264  can include a processor executing preprogrammed instructions coupled to the robotic system  250  through a cable. Alternatively or in addition, the controller  264  includes a user interface to allow an operator to at least contribute to operation of the robotic system  250 . Preferably, the robotic system  250  requires minimal operator intervention during use, to expedite manipulations of the tool  252  or assembly  254 . 
     In some embodiments, the robotic system  250  is positioned in relation to a stowed tool  252  and a user access aperture  256  of the adaptive seal assembly  254  such that the grasper  262  is moveable between the stowed tool  252  and the assembly  254  without having to relocate the base unit  258 . The robotic system  250  includes sufficient degrees of freedom to allow the grasper  262  to access the stowed tool  252  and translate the stowed tool  252  to a position above the user access aperture  256  of the assembly  254 . In some embodiments, the robotic system  250  is also capable of lowering the tool  252  into an internal cavity of the assembly  254  and into a wellhead fixture  36  as shown. The tools  252  can be stowed on the bed of a tool delivery vehicle such as a truck or rail vehicle as shown. Such precise robotic manipulation of tools  252  and/or assemblies  254  with respect to the wellhead fixtures  36  reduces the time and complexity associated with inserting and extracting tools from a well under pressure. 
     In some embodiments, the pick-and-place robotic system  250  includes a vertical mast  266  coupled at one end to the base unit  258  and at an opposite end to one end of an arm  260 . The vertical mast  266  can be angled in some embodiments. Alternatively or in addition, the vertical mast can include an extendable portion allowing the mast to extend and contract along an axis of the mast. A first joint  268   a  is attached between the vertical mast  266  and the arm  260  allowing relative movement between the arm  260  and the vertical mast  266 . The arm  260  includes a boom  270  coupled at one end to the first joint  268   a  and at an opposite end to a second joint  268   b . A third joint  268   c  can be coupled between the second joint  268   b  and the grasper unit  262 . Preferably, at least one of the base unit  258  and the vertical mast  262  is able to rotate with respect to the other. 
     In some embodiments, the robotic system includes a seven degrees-of-freedom (DOF) similar to that of a human arm. Such a configuration provides mobility for the robotic system  250  to grasp items such as tools  252  and/or adaptive seal assemblies  254  from different angles or directions. More or less degrees of freedom can be provided in various embodiments of the robotic system  250 . 
     In some embodiments, a robotic system  251  includes a selective compliant assembly robot arm (SCARA). Such a SCARA configuration can provide a four-axis robot arm able to move to any XYZ coordinate within a work envelope. The fourth axis of motion is a wrist allowing a rotation of a grasper about the arm. Such a configuration can be accomplished with three parallel axis rotary joints. Vertical motion can be provided at an independent linear axis at the wrist or in the base of the robotic system  250 . SCARA robots  251  are particularly useful in situations in which a final movement is to insert a grasped part using a single vertical move. Thus, the SCARA robot  251  is advantageous for many types of pick-and-place assembly applications, particularly those in which an elongated item is placed within a hole without binding. 
       FIG. 14  illustrates a general rigless coiled tubing deployment system  299  architecture in which a coiled tubing injector  204  exerts thrust onto one or more tools of a tool array. The deployment system  299  can include mobile platform, such as a truck  300  having a trailer portion with a coiled tubing reel  302  mounted thereon, onto which a length of coiled tubing  304  is at least partially wound. The system  299  also includes a coiled tubing thrust unit  308  positioned along a length of the coiled tubing  304  between the reel  302  and the tool  40   a . In some embodiments, the thrust unit  308  is supported by a boom  306  pivotally attached to a trailer portion of the truck  300 . 
     During an insertion procedure, the coiled tubing thrust unit  308  provides a thrust directed away from the coiled tubing reel  302 . The thrust unit  308  extracts a length of coiled tubing  304  from the reel and directs it upward at a slope and through a bend  310  into vertical alignment above the tool  40   a . The tool  40   a  can be at least partially positioned within a wellhead fixture  36  as illustrated. Thrust applied by the coiled tubing thrust unit  308  extracts greater lengths of coiled tubing  304  from the coiled tubing reel  302 , forcing it around the bend  310  and directing it downward into the well. The wellhead fixture  36  can include seals adapted to seal against the coiled tubing allowing the coiled tubing to thrust the tool  40   a  further down-hole while maintaining pressure differential within the well. Also illustrated is a robotic system  250  adjacent to the wellhead fixture  36  that can be used in combination with the rigless coiled tubing system  299 . The robotic system  250  is shown grasping a second instrument  40   b  in anticipation for positioning it above an open end of the wellhead fixture  36  once the first instrument has been inserted. The end of the coiled tubing  304  coupled to the first tool  40   a  can be disconnected once the first tool  40   a  is sufficiently inserted into the open end of the wellhead fixture  36 , and reconnected to a proximal end of the second tool  40   b . The process can be repeated as necessary for additional tools of a tool array. 
     An alternative embodiment of a coiled tubing deployment system  299 ′ is illustrated in  FIG. 15 . In this embodiment, a second boom  320  is provided attached at a base end to a portion of the truck  300  and having at its opposite end a bearing surface  322 . The second boom is positioned between the coiled tubing thrust unit  308  and the wellhead fixture  36 . Preferably, the second boom aligns the bearing surface  322  at the bend  310  portion of the coiled tubing. The bearing surface  322  can be used to assist in directing the coiled tubing  304  around the bend from the coiled tubing thrust unit  308  and into vertical alignment with a proximal end of logging tool  40   a  or wellhead fixture  36 . 
     While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.