Patent Publication Number: US-10774604-B2

Title: Slick line, fiber optic cable or tubing wellbore pulling tool and propulsion module

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a pulling tool and to a propulsion module of a pulling tool used for pulling itself and other equipment into a wellbore or tubing. 
     2. Description of Related Art 
     Wellbores and tubing typically include long vertical and horizontal runs. In many wells there is a need for installing a fiber optic cable to obtain real-time measurements of flow, pressure, and temperature, among other things. In itself, a fiber optic cable is very thin and weak. Therefore, several types of claddings are used for protecting the fiber optic cable such as metal, Kevlar, or carbon rods. Common to all these cables are that they are very lightweight and a bit flexible, which present some challenges when they are to be installed in horizontal wells. 
     Since a fiber optic cable is a signal cable only, most pulling tools need to be battery operated. Therefore, it is essential that the pulling tool is as efficient and lightweight as possible to limit the necessary power consumption. Currently, no pulling tool exists that is specially designed for these applications. 
     In addition to fiber optic cable installation, there is also a need for a pulling tool for performing light slick line well interventions. Similarly to a fiber optic cable, the same challenges are encountered when a slick line is run into horizontal wells. Due to the limited rigidity of the slick line, it is not possible to push it very far into horizontal wells. In order to be able to perform light well interventions by way of slick line in horizontal wells, a battery operated pulling tool is needed. 
     Wells in which there is a need for running light well interventions have small internal diameters and have nipple profiles as small as 40 mm. Therefore, it is necessary to construct the pulling tool small enough to be able to pass through the smallest nipple profiles. To enable this, known gearing solutions are used in a new manner herein. The diameter of the well may be larger than the combined diameters of the pulling tool and the cable to be pulled by the pulling tool. 
     Several variants of pulling tools or well tractors are available in the market. A known solution includes an electric motor driving a hydraulic pump which in turn drives a hydraulic motor of the propulsion wheel. Such a system is technically complex and not very efficient. Other variants available use an electric motor that translates the rotation directly by way of an angular gear and on to the wheel either by way of chain/belt drive or straight gears. Such systems present a challenge in that the gear ratio is not high enough to allow the use a high efficiency, brushless permanent magnet motor operating at a relatively high revolutions per minute (RPM). It is known to include a planetary gear in the propulsion wheel itself, of which the moving outer gear constitutes the propulsion wheel of the pulling tool, in order to reduce the rotational speed between the motor and the propulsion wheel. However, there is a limitation on how small a planetary gear can be made since such a gear includes a number of components located inside each other, each of which needs to resist the torque applied. Also, the achievable gear ratio is relatively low. 
     SUMMARY OF THE INVENTION 
     Through the present invention a robust and efficient gear system having a higher gear ratio than those of existing systems is obtained. In general, smaller diameter motors operate at a higher RPM and it is therefore desirable to have a higher gear ratio between the motor and the propulsion wheel. By this invention, a higher gear ratio is obtained in a more compact design, and consequently a higher gear ratio between the motor and the propulsion wheel is provided. 
     As compared to a planetary gear solution of the same size, this invention provides a gear ratio that is 5-10 times higher within the same dimensions. 
     Another object of the invention is to enable the construction of a pulling tool whose diameter is smaller than that of the pulling tools currently available in the market. 
     The present invention provides a small-sized, lightweight, high performance propulsion unit, which is preferably battery-operated. 
     The present invention discloses a slick line and/or fiber optic cable pulling wellbore and/or tubing pulling tool including a propulsion module having a main section. A propulsion arm is hinged to the main section, the propulsion arm having a propulsion wheel with a gear system. The gear system of the propulsion wheel comprises an eccentric, internally toothed gear system including a fixed inner gear and a moving outer gear. The moving outer gear includes the internal toothing and constitutes the propulsion wheel of the pulling tool. An electric motor for driving the propulsion wheel via the gear system is located in the hinged propulsion arm. 
     A “slick line”, as the term is used herein, may also include an electric cable. 
     In the present invention, a high efficiency, high RPM, low torque, submergible brushless motor can be used which exhibits good moisture resistance and wear resistance and that does not lose power and efficiency over time. This is enabled through the use of a gear system in the propulsion wheel, which gear system includes an eccentric, internally toothed gear system in the form of a hypocycloid gear, or a cycloid gear exhibiting a rated transformer ratio and an output torque that is significantly larger than what can be achieved with a planetary gear of the same size. 
     The pulling tool may further comprise a cable transition, a battery module including one or more batteries for operating the electric motor, an electronics module, and at least two propulsion modules. 
     The pulling tool may further comprise four propulsion modules and a nose connection. 
     The electric motor may comprise a rotor having an anchor with an output shaft and a pinion fixed to the output shaft. 
     The electric motor may be a brushless motor having a longitudinal axis perpendicular to an axis of rotation of the propulsion wheel, and the pulling tool may further comprise a brushless motor controller. 
     An electric actuator can be provided between the main section and the hinged propulsion arm, with the hinged propulsion arm being configured for assuming a first, retracted position inside the propulsion module and a second, actuated position against a wellbore or tubing wall. 
     The pulling tool may have an external diameter of less than 40 mm. 
     The transmission ratio between the electric motor and the propulsion wheel can be greater than 1:50, and may be between 1:50 and 1:200 or higher so that a very low gearing can be achieved. 
     The eccentric, internally toothed gear system may be a cycloid gear. 
     The eccentric, internally toothed gear system may be a hypocycloid gear. 
     The invention further comprises a pulling tool propulsion module including a main section and a propulsion arm hinged to the main section, the propulsion arm having a propulsion wheel with a gear system. The gear system of the propulsion wheel comprises an eccentric, internally toothed gear system with a fixed inner gear and a moving outer gear exhibiting the internal toothing. The moving outer gear constitutes the propulsion wheel of the pulling tool. An electric motor drives the propulsion wheel through the gear system. 
     The electric motor may include a rotor with an anchor having an output shaft and a pinion fixed to the output shaft. 
     The electric motor may be a brushless motor having a longitudinal axis perpendicular to an axis of rotation of the propulsion wheel, with the pulling tool further including a brushless motor controller. 
     The transmission ratio between the electric motor and the propulsion wheel of the propulsion module can be greater than 1:50. 
     The eccentric, internally toothed gear system of the propulsion module may be a cycloid gear. 
     The eccentric, internally toothed gear system of the propulsion module may be a hypocycloid gear. 
     The present invention comprises a pulling tool having a tilting arm, a gear arrangement, and a wheel, in which an eccentric, internally toothed gear system is intended to include a cycloid gear, or hypocycloid gear with a fixed inner gear and a moving outer gear, which outer gear constitutes the propulsion wheel of the pulling tool. The eccentric, internally toothed gear system is not intended to include centric gear systems such as planetary gear systems. 
     A propulsion module for use in a wellbore, consisting of a main section and a propulsion arm including a propulsion wheel driven by a motor through a gear arrangement. The propulsion arm can be tilted from the main section by means of an electric motor or hydraulic piston action. The principle of the tilting arm is not described in this invention. 
     The gear arrangement between the motor and the wheel consists of an angular gear, straight gears, and the wheel itself. 
     A pulling tool includes at least one propulsion arm. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an embodiment of a propulsion module of a pulling assembly according to this invention; 
         FIG. 2  is a perspective view of the propulsion arm; 
         FIG. 3  shows the drive mechanism of the propulsion arm; 
         FIG. 4  shows the propulsion wheel; 
         FIG. 5  shows the propulsion wheel with a cycloid gear in a sectional view; 
         FIG. 6  shows the wheel with a cycloid gear with all parts in an exploded view; 
         FIG. 7  shows the wheel with a cycloid gear with all parts in an exploded view; 
         FIG. 8  shows the propulsion wheel with a hypocycloid gear in a sectional view; 
         FIG. 9  shows the wheel with a hypocycloid gear with all parts in an exploded view; 
         FIG. 10  shows the wheel with a hypocycloid gear with all parts in an exploded view; 
         FIG. 11  shows an embodiment of a pulling tool with two propulsion modules and two centralization modules; and 
         FIG. 12  shows an embodiment of a pulling tool with four propulsion modules. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention will now be explained in more detail using a cycloid gear, with reference to the drawings: 
       FIG. 1  is a perspective view of an embodiment of a pulling assembly according to the present invention. The pulling assembly includes a main section  1  supporting a complete propulsion arm  2 . The complete propulsion arm  2  is connected to main section  1  via a hinge joint  3  by way of which the complete propulsion arm  2  can be tilted outwards. 
       FIG. 2  shows the complete propulsion arm  2  comprising an arm body  4 , a pivoting hole  5 , the drive mechanism of  FIG. 3 , a complete propulsion wheel  6  and a cover  7 . 
       FIG. 3  shows the drive mechanism comprising a motor  8 , an angular gear which includes a pinion  9  fixed to the drive shaft of the motor, and a crown gear  10  supported in arm body  4  (shown in  FIG. 2 ) by way of a bearing  11 . Pinion  9  is supported in arm body  4  (shown in  FIG. 2 ) by way of a bearing  12 . Crown gear  10  is connected to a straight toothed wheel  13  connected to a straight toothed wheel  14 , which is in turn connected to a straight toothed wheel  15  being part of the complete propulsion wheel  6 . 
     The motor  8  rotates pinion  9  which transfers rotation to crown gear  10  which, through straight toothed wheel  13 , transfers rotation to straight toothed wheel  14  which transfers rotation to straight toothed wheel  15  which transfers rotation to the complete propulsion wheel  6 . 
     Toothed wheel  14  is supported by way of a bearing  16  supported on a shaft  17  attached to arm body  4  (shown in  FIG. 2 ). Straight toothed wheel  15  includes a concentric shaft section  49  and is supported by way of a bearing  19  in arm body  4  (shown in  FIG. 2 ). 
     The complete propulsion wheel  6  comprises a static component  20  fixed to arm body  4  (shown in  FIG. 2 ) by fixing screws  21 . 
       FIGS. 4 and 5  show a complete propulsion wheel  6  comprising a straight toothed wheel  15  including a concentric shaft section  22 , a concentric shaft section  23 , a concentric shaft section  49 , and an eccentric shaft section  24 . Concentric shaft section  22  is supported by way of a bearing  25  of the static component  20 . Concentric shaft section  23  is supported by way of a bearing  26  of static component  20 . Eccentric shaft section  24  rotates via a bearing  27  moving the center axis of toothed wheel  28  about the center axis of concentric shaft sections  22  and  23 . The center axis of toothed wheel  28  and eccentric shaft section  24  rotates about the center axis of concentric shafts  22  and  23 . Toothed wheel  28  is prevented from rotating about its own center axis by eccentric roller pins  29  connected between toothed wheel  28  and static component  20 . The external toothing  30  of toothed wheel  28  has fewer teeth than the internal toothing  31  of an outer propulsion wheel  32 . Outer propulsion wheel  32  is supported by way of a bearing  33  of the static component  20  and connected by way of a mounting  34 . 
     When toothed wheel  28  is moved eccentrically as the center axis thereof rotates about the center axis of concentric shafts  22  and  23 , toothed wheel  28  will force outer wheel  32  to rotate by the meshing between toothing  30  and toothing  31 . The gear ratio between toothed wheel  28  and outer propulsion wheel  32  equals the difference in number of teeth between toothings  30  and  31 . If, for example, the number of teeth of wheel  30  is 49 and the number of teeth of wheel  31  is 50, then the gear ratio is (50−49)/50=1:50. 
     Toothed wheel  15  is supported by way of bearing  19  in arm body  4  (cf.  FIG. 2 ). Static component  20  is fixed to arm body  4  (shown in  FIG. 2 ) by way of fixing screws  21  (shown in  FIG. 3 ) in threaded holes  54 . 
       FIGS. 6 and 7  are exploded views of the complete propulsion wheel  6 . Toothed wheel  15  includes a gear rim with straight toothing  71 , concentric shaft section  49 , concentric shaft section  22 , concentric shaft section  23 , and eccentric shaft section  24 . Bearing  19  is mounted to shaft section  49  and against arm body  4  (shown in  FIG. 2 ). Bearing  25  is mounted to concentric shaft section  22  and in a housing raceway  50 . Bearing  26  is mounted to concentric shaft section  23  and in a housing raceway  58 . Bearing  27  is mounted to eccentric shaft section  24  and in a housing raceway  56 . Bearing  33  is mounted to a bearing raceway  57  and a bearing raceway  55  is fitted over bearing  33 . Eccentric roller pins  29  include a concentric shaft section  51  and an eccentric shaft section  52 , the concentric shaft section  51  being mounted in a roller housing  59  and the eccentric shaft section  52  being mounted in a roller housing  53 . Static component  20  is fixed in arm body  4  (shown in  FIG. 2 ) by way of fixing screws  21  (shown in  FIG. 3 ) in threaded holes  54 . Toothed wheel  28  includes roller housing  53 , housing raceway  56 , and outer gear rim  30 , meshing with internal gear rim  31 . Outer propulsion wheel  32  includes internal toothing  31  and an internal thread  69 . An external thread  66  is engaged with internal thread  69 , thereby keeping outer propulsion wheel  32 , toothed wheel  28 , eccentric roller pins  29 , static component  20 , and mounting  34  together via bearing  33 . 
     In another embodiment of the invention, a hypocycloid gear may be used. 
     In this embodiment,  FIGS. 1, 2, 3, and 4  are as set forth in the above example using a cycloid gear. In this embodiment,  FIGS. 5, 6, and 7  are replaced with  FIGS. 8, 9, and 10 , respectively. 
       FIG. 8  shows a complete propulsion wheel  67  including a straight toothed wheel  42  which includes a concentric shaft section  68  and an eccentric shaft section  44 . Concentric shaft section  68  is supported by way of a bearing  41  of a static component  38 . Eccentric shaft section  44  rotates via a bearing  40 , moving the center axis of a double cycloid disk  39  about the center axis of concentric shaft section  68 . Double cycloid disc  39  has a cycloid toothing  46  (also shown in  FIGS. 9 and 10 ) and a cycloid toothing  47  (also shown in  FIGS. 9 and 10 ). Cycloid toothing  46  moves in eccentric circles meshing with an internal cycloid toothing  45  (also shown in  FIGS. 9 and 10 ) of static component  38 . Cycloid toothing  47  moves in concentric circles meshing with an internal toothing  48  (also shown in  FIGS. 9 and 10 ) of outer propulsion wheel  37 . 
     The difference in number of teeth of cycloid toothing  46  relative to internal cycloid toothing  45  results in a gear ratio, so that double cycloid disc  39  rotates relative to the center axis of concentric shaft section  68 . For example, if the number of teeth of cycloid toothing  46  is 7 and the number of teeth of internal cycloid toothing  45  is 8, then the gear ratio between static component  38  and double cycloid disc  39  is 1:7. 
     Similarly, the difference in number of teeth between cycloid toothing  47  and internal toothing  48  provides an additional gearing step for the rotation of outer propulsion wheel  37 . 
     Propulsion wheel  37  is connected to static component  38  via an axial bearing  33  mounted between an angled bearing raceway section  35  and an angled bearing raceway  36  screwed to outer propulsion wheel  37 . 
     Straight toothed wheel  42  is supported in arm body  4  (shown in  FIG. 2 ) via a bearing  43 . 
       FIGS. 9 and 10  are exploded views of the complete propulsion wheel  67 . Toothed wheel  42  comprises a concentric shaft section  70 , a gear rim with straight toothing  71 , concentric shaft section  68  and eccentric shaft section  44 . Concentric shaft section  70  is supported in arm body  4  (shown in  FIG. 2 ) by bearing  43 . 
     Bearing  41  is mounted to concentric shaft section  68  and in a housing  73 . A bearing  72  is mounted to eccentric shaft section  44  and in housing  74 . Double cycloid disc  39  is mounted in static component  38  so that outer cycloid toothing  46  meshes with inner cycloid toothing  45 . Oppositely, outer cycloid toothing  47  is mounted so as to mesh with inner cycloid toothing  48  included by outer propulsion wheel  37 . Axial bearing  33  is mounted on bearing raceway  75 . Angled bearing raceway section  35  is mounted in internal housing  76 . Bearing raceway  36  is mounted outside of axial bearing  33  and in internal housing  76 . 
       FIGS. 11 and 12  show two pulling tools including two and four propulsion modules  64  according to the invention, respectively. The propulsion modules may include fasteners at each end for attaching a similar propulsion module or a different unit. The fasteners may comprise bayonet joints or threaded members. Each propulsion module may include a male fastening means at one end and a female fastening means at the other end, the male fastening means being configured for fitting attachment in the female fastening means. The fastening means may also include members or connectors for the transfer of power for operation and signalling. 
       FIG. 11  shows a battery-operated pulling tool comprising a cable transition  60 , a battery module  61 , an electronics module  62 , two centralization modules  63 , two propulsion modules  64  and a nose connection  65 . 
       FIG. 12  shows a battery-operated pulling tool comprising a cable transition  60 , a battery module  61 , an electronics module  62 , four propulsion modules  64 , and a nose connection  65 .