Patent Publication Number: US-2016222733-A1

Title: Torque stabilization for a rig mast

Description:
RELATED APPLICATIONS 
     This Application claims the benefit of Canadian Application No. 2,881,002, filed Feb. 3, 2015, said prior application being hereby fully incorporated by reference herein. 
     TECHNICAL FIELD 
     This disclosure relates to the field of well drilling and servicing rigs and in particular a system for resisting torque forces on the mast of such rigs. 
     BACKGROUND 
     A typical rig for drilling and servicing wells, such as oil and gas wells, comprises a mast mounted on a transport vehicle for movement from one work site to another. The mast typically has a winch mechanism at the top thereof for drawing tubing out of a well. The mast is laid down horizontally on the vehicle for transport, and moved to a vertical position at the work site, typically by tipping the front end of the mast up so the mast extends upward from the rear end of the vehicle. 
     Typically as well the mast is extended vertically when at the well site, since a taller mast allows for multiple lengths of tubing to be handled which reduces the time required for the various drilling or servicing operations which require the tubing to be pulled out of the well or placed in the well. A common configuration is for the mast to comprise two or more frame members that telescope up and down to extend and retract the mast. The lengths of tubing are commonly supported vertically by a racking board which extends rearward from the mast at a middle vertical location on the mast. 
     Examples of such rigs are disclosed in U.S. Pat. No. 7,246,983 to Zahn et al. and U.S. Pat. No. 4,290,495 to Elliston. 
     A significant surface area is presented to wind loading when the racking board is filled with tubing extending rearward from the mast. A wind pushing laterally on the tubing puts a considerable torque force on the mast and causes same to twist. The upper ends of the tubing may move laterally in response to the wind forces causing them to lean against the racking board and add further torque forces on the mast. These torque forces must be resisted to avoid damage to the mast. Typically external guy wires are attached from the mast and/or racking board to anchors spread across the ground, however these interfere with activities taking place around the work site. It is also known to provide internally guyed rigs, typically with outriggers at the rear end of the transport vehicle which extend laterally to stabilize the vehicle and mast, and with the guy wires anchored to the outriggers and to the vehicle itself as well with no actual anchors on the ground. 
     SUMMARY 
     The present disclosure provides a system for resisting torque forces on the racking board of a rig mast that overcomes problems in the prior art. 
     The present disclosure provides a rig mast torque stabilization system comprising a mast pivotally mounted on a vehicle for transport, the mast movable from a substantially horizontal mast transport position to a substantially vertical mast operating position extending upward from a rear end of the vehicle. A racking board extends, when in a board operating position, rearward from a vertical location in a middle portion of the mast when the mast is in the mast operating position. Right and left elongated braces are movably attached to corresponding right and left sides of the middle portion of the mast, and are movable from a brace transport position where outer ends of the braces are in proximity to the mast, to a brace operating position where the braces extend laterally outward from corresponding right and left sides of the mast to the outer ends of the braces. Right and left mast tethers are each connected at a lower end thereof to the corresponding right and left brace, and each is connected at an upper end thereof to the mast at a location above the corresponding right and left brace. The mast tethers are configured to be in tension when the racking board is in the board operating position, the mast is in the mast operating position, and the braces are in the brace operating position. Right and left board tethers are each connected at an outer end thereof to an outer end of the corresponding right and left brace, and each is connected at an inner end thereof to the racking board. The board tethers are configured to be in tension when the racking board is in the board operating position, the mast is in the mast operating position, and the braces are in the brace operating position. Right and left vehicle tethers are each connected at an upper end thereof to the corresponding right and left brace, and connected at a lower end thereof to a forward location on the vehicle. The vehicle tethers are configured to be in tension when the racking board is in the board operating position, the mast is in the mast operating position, and the braces are in the brace operating position. 
     The tethers, braces, etc. will be sized and connected at locations suitable for a particular rig configuration. The tension on the board tethers exerts lateral right and left forces on the racking board that resists torque forces caused by wind, leaning tubing, or the like. Positioning the braces just below the racking board provides a large proportion of the tension force in the board tethers providing lateral force on the racking board with little downward force exerted on the racking board. The system can be configured for a variety of rig configurations to suitably stabilize the racking board against torque forces from wind, leaning tubing and like factors 
     The above summary is not intended to describe each illustrated embodiment or every implementation of the subject matter hereof. The figures and the detailed description that follow more particularly exemplify various embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Subject matter hereof may be more completely understood in consideration of the following detailed description of various embodiments in connection with the accompanying figures, in which: 
       While the invention is claimed in the concluding portions hereof, preferred embodiments are provided in the accompanying detailed description which may be best understood in conjunction with the accompanying diagrams where like parts in each of the several diagrams are labeled with like numbers, and where: 
         FIG. 1  is a schematic top view of an embodiment of the rig mast stabilization system of the present disclosure in the operating position; 
         FIG. 2  is a schematic side view of the embodiment of  FIG. 1  in the operating position; 
         FIG. 3  is a schematic top view of the embodiment of  FIG. 1  in the transport position; 
         FIG. 4  is a schematic side view of the embodiment of  FIG. 1  in the operating position; 
         FIG. 5  is a schematic side view of the embodiment of  FIG. 1  in an intermediate position with the mast vertical but not yet extended; 
         FIG. 6  is a schematic side view of the embodiment of  FIG. 1  in the operating position with the mast fully extended and all tethers in tension; 
         FIG. 7  is a schematic side view of an internally guyed rig of the prior art; 
         FIG. 8  is a rear view of the prior art internally guyed rig of  FIG. 7 ; 
         FIG. 9  is a schematic perspective view of the outer end of the brace of the embodiment of  FIG. 1 ; 
         FIG. 10  is a schematic end view of the outer end of the brace illustrated in  FIG. 9 ; 
         FIG. 11  is a schematic front view of the braces of the embodiment of  FIG. 1  showing the braces pivoting from the brace transport position to the brace operating position; 
         FIG. 12  is a schematic front view of an alternate arrangement of braces of showing the braces telescoping from the brace transport position to the brace operating position. 
     
    
    
     While various embodiments are amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the claimed inventions to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the subject matter as defined by the claims. 
     DETAILED DESCRIPTION OF THE DRAWINGS 
       FIGS. 1-6  schematically illustrate an embodiment of a rig mast stabilization system  1  of the present disclosure. The system  1  comprises a mast  3  pivotally mounted on a vehicle  5  for transport. The mast  3  is movable from a substantially horizontal mast transport position shown in  FIGS. 3 and 4  to a substantially vertical mast operating position shown in  FIG. 2  extending upward from a rear end of the vehicle  5 . In the illustrated system  1  the mast pivots about a horizontal mast pivot axis MPA to move between horizontal to vertical. Typically such masts operate slightly off exact vertical by about three to four degrees. 
     A racking board  7  extends, when in a board operating position, rearward from a vertical location in a middle portion of the mast  3  when the mast  3  is in the mast operating position shown in  FIG. 2 . 
     Right and left elongated braces  9 R,  9 L are movably attached to corresponding right and left sides of the middle portion of the mast  3 . The braces  9  are movable from a brace transport position  9 A where outer ends  11  of the braces  9  are in proximity to the mast  3  as shown in  FIG. 3 , to a brace operating position  9 B where the braces  9  extend laterally outward from corresponding right and left sides of the mast  3  to the outer ends  11  of the braces  9 . 
     Right and left mast tethers  13 R,  13 L are each connected at a lower end thereof to the corresponding right and left brace  9 R,  9 L, and each mast tether  13  is connected at an upper end thereof to the mast  3  at a location above the corresponding right and left brace  9 . The mast tethers  13  are configured to be in tension when, as shown in  FIG. 2 , the racking board  7  is in the board operating position, the mast  3  is in the mast operating position, and the braces  9  are in the brace operating position. The mast tethers  13  will typically be connected to the braces  9  at or near the outer ends  11  thereof. 
     Right and left board tethers  15 R,  15 L are each connected at an outer end thereof to the outer end  11  of the corresponding right and left brace  9 R,  9 L, and each board tether  15  is connected at an inner end thereof to the racking board  7 , and for best advantage to the outer corners of the racking board  7 . Like the mast tethers  13 , the board tethers  15  are configured to be in tension when, as shown in  FIG. 2 , the racking board  7  is in the board operating position, the mast  3  is in the mast operating position, and the braces  9  are in the brace operating position. 
     Finally, right and left vehicle tethers  17 R,  17 L are each connected at an upper end thereof to the corresponding right and left brace  9 R,  9 L, typically at or near the outer ends  11  thereof, and each vehicle tether  17  is connected at a lower end thereof to a forward location  19  on the vehicle  5 . Like the mast tethers  13  and the board tethers  15 , the vehicle tethers  17  are configured to be in tension when, as shown in  FIG. 2 , the racking board  7  is in the board operating position, the mast  3  is in the mast operating position, and the braces  9  are in the brace operating position. 
     Further cables and lines extend between the mast  3 , the vehicle  5 , and the racking board  7  as is known in the art and are not further illustrated to allow clear illustration of the present rig mast stabilization system  1 . 
     With all the tethers  13 ,  15 ,  17  in tension, it can be seen that lateral right and left stabilizing forces RFR and RFL are exerted on the racking board  7 . These forces stabilize the mast  3  by resisting lateral forces from wind, tubing leaning on the racking board, and the like which tend to twist the mast  3 . The forces RFR, RFL are equal to the right and left components of the tension forces BF exerted on the board tethers  15 . It can be seen that as the length of the braces  9  increases, the angle N increases as well and the lateral component of the tension force F, which provides the racking board forces RFR, RFL, increases as well. Typically in the present system  1  the length of the braces  9  is selected to provide sufficient lateral right and left forces RFR and RFL on the racking board  7  while still being practical to use. 
     In the prior art, rigs are stabilized by external guy wires where guy wires connect ground anchors to the racking board however these ground anchors interfere with the work area on the ground around the rig and so are undesirable. Internally guyed systems are also known, for example as schematically illustrated in the system  101  in  FIGS. 7 and 8 , where guy wires  117  connect the racking board  107  with outriggers  121  which extend outward from the transporting vehicle  105 . It can be seen that, because of the limited length of the outriggers  121 , the angle N′ between the guy wires  117  and the mast  103 , which provides the lateral force component RF′ on the racking board  107 , is quite small compared to the angle N in the system  1  of the present disclosure. 
     Thus in the internally guyed systems of the prior art the lateral component RF′ of the tension force F′ is a small proportion of the total, and so a significantly greater tension force F′ must be exerted to achieve a satisfactory stabilizing lateral force RF on the racking board  107 . It can be seen as well that the downward component of force DF′ pulling down on the outer end of the racking board  107  is very significant, requiring further guy wires extending up to the upper part of the mast  103  and from the mast  103  to the vehicle  105 . 
     In contrast it can be seen in  FIG. 2  that the downward component DF of the tension force BF in the board tether  15  is a small proportion of the total. 
     As is common with service and drilling rigs of the type contemplated the mast  3  is extendable. As schematically illustrated in  FIGS. 3-6 , the mast  3  is retracted when in the mast transport position seen in  FIGS. 3 and 4 , and when moving from the mast transport position to the mast operating position the mast  3  is moved from the horizontal transport position of  FIG. 4  to a vertical retracted position shown in  FIG. 5  with a lower mast section  3 A extending upward from the rear end of the vehicle  5 , and then an upper mast section  3 B is moved upward with respect to the lower mast section  3 A to extend the mast  3  vertically to the mast operating position shown in  FIG. 6 . The braces  9  are attached to an upper portion of the lower mast section  3 A and the racking board  7  is attached to a lower portion of the upper mast section  3 B, such that the racking board  7  moves upward with the upper mast section  3 B to a vertical position in proximity to the braces  9  when the mast  3  moves to the mast operating position. 
     The tethers  13 ,  15 ,  17  can be installed and tensioned after the mast  3 , racking board  7 , and braces  9  are in their operating positions, and this may be most convenient where the mast is of a fixed length and not extendable. Where as is common the industry, the mast is extendable, installing the tethers and tensioning them can be more problematic. 
     The illustrated system  1  with the extendable mast  3  conveniently facilitates installation and tensioning of the tethers by using right and left main tethers  23 R,  23 L to provide the corresponding right and left board tethers  15 R,  15 L and right and left vehicle tethers  17 R,  17 L. Each main tether  23  comprises a board section  23 A between the upper end thereof connected to the racking board  7  and a stop member  25  attached to the main tether  23  at a distance from the racking board  7  that corresponds to a length of the board tether  15 , and a vehicle section  23 B between the stop member  25  and the lower end thereof attached to the forward location on the vehicle which corresponds to the length of the vehicle tether  17 . 
     The vehicle section  23 B of each main tether  23  passes through a hole  27  in a stop plate  29  attached to the outer end  11  of the corresponding brace  9  and then over a pulley  31  attached to the corresponding brace  9 , and then downward and forward to the forward location  19  on the vehicle. 
     As is common in the art, the racking board  7  is pivotally attached to the upper mast section  3 B about a horizontal board pivot axis BPA and the racking board  7  pivots upward to a board transport position lying against the upper mast section  3 B as seen in  FIGS. 3 and 4 , and then pivots downward to the board operating position extending rearward from the mast as shown in  FIGS. 5 and 6  when the mast  3  is moved from the horizontal transport position of  FIG. 4  to the vertical position of  FIG. 5 . 
     In operation, when moving the system  1  from a transport position to an operating position the braces  9  are moved from the transport position  9 A shown in phantom lines in  FIG. 3  lying against the lower mast section  3 A out to the board operating position . When the mast  3  and racking board  7  are in their transport positions as shown in  FIGS. 3 and 4 , and when the mast  3  is moved to the vertical position and the racking board  7  moves to the board operating position as shown in  FIG. 5 , the vehicle section  23 B of each main tether  23  is loose, as shown with the lower end thereof lying coiled on the ground in  FIG. 4  and coiled lying on the vehicle  5  in  FIG. 5 . 
     The lower end of the main tether  23  is pulled downward as the upper mast section  3 B, and the racking board  7  and board section  23 A of the main tether  23  attached thereto, moves upward, and when the mast  3  is in the mast operating position of  FIG. 6  the lower end of the main tether  23  is connected to a tensioning device  33  at the forward location on the vehicle  19 . The tensioning device  33 , such as a winch, turnbuckle, or the like is operative to exert tension on the main tether  23  such that the stop members  25  on the right and left main tethers  23 R,  23 L bear against the stop plates  29  on the corresponding right and left braces and exert a forward force on the stop plates  29 . The stop members  25  is located on the main tethers  23  at locations such that when the stop member  25  contacts the stop plate  29 , the board section  23 A of the main tether  23  is in tension. The mast tethers  13  have a length selected such that the downward force exerted by the tension in the vehicle section  23 B of the main tether  23  exerts tension in the mast tethers  13 . 
     The combination of forces FM, FB, and FV exerted by the mast tether  13 , board tether  17 ,  23 A, and vehicle tether  17 ,  23 B on the outer end  11  of the brace  9  result in a force B on the brace  9  that is generally inward toward the mast  3 . 
     Typically the stop member  25  is releasably clamped to the main tether  23  with a clamp device  35  so that its location on the main tether can be adjusted to conveniently set up the system initially, and to adjust the position to compensate for stretch or like variations during continued use. 
     For most applications it is contemplated that the outer ends  11  of the braces  9  will be just slightly below the board pivot axis BPA when the racking board  7  is in the board operating position, the mast  3  is in the mast operating position, and the braces  9  are in the brace operating position. This results in a small downward force component DF as shown in  FIG. 2 , which prevents the racking board  7  from moving upward, and yet keeps a large proportion of the force FB acting perpendicular to the racking board  7  to maximize the lateral stabilizing forces RFR, RFL. 
     In the illustrated system  1  the right and left braces  9 R,  9 L are pivotally attached to corresponding right and left sides of the mast  3 , and pivot from the brace transport position  9 A folded substantially into alignment with the mast  3 , to the brace operating position  9 B extending substantially perpendicularly outward from the mast  3 , as schematically illustrated in  FIG. 11 . 
     It is also contemplated that the braces could be movably attached in other ways, for example  FIG. 12  schematically illustrates the braces  9 ′ telescopically attached to corresponding right and left sides of the mast  3 ′, where the braces  9 ′ telescope outward from the brace transport position  9 B′ to the brace operating position  9 A′. 
     The tethers will typically be wire cable, but could also be chain or the like if same suited a particular application. The exact configuration of the system, such as dimensions, attachment locations of the tethers, braces, etc. will depend on the particular rig in question, and further stabilization equipment such as outriggers or the like will typically be required to support the mast vertically, however the tethers and braces described herein can be configured for a variety of rig configurations to suitably stabilize the racking board against torque forces from wind, leaning tubing and like factors. 
     The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous changes and modifications will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all such suitable changes or modifications in structure or operation which may be resorted to are intended to fall within the scope of the claimed invention. 
     Various embodiments of systems, devices, and methods have been described herein. These embodiments are given only by way of example and are not intended to limit the scope of the claimed inventions. It should be appreciated, moreover, that the various features of the embodiments that have been described may be combined in various ways to produce numerous additional embodiments. Moreover, while various materials, dimensions, shapes, configurations and locations, etc. have been described for use with disclosed embodiments, others besides those disclosed may be utilized without exceeding the scope of the claimed inventions. 
     Persons of ordinary skill in the relevant arts will recognize that the subject matter hereof may comprise fewer features than illustrated in any individual embodiment described above. The embodiments described herein are not meant to be an exhaustive presentation of the ways in which the various features of the subject matter hereof may be combined. Accordingly, the embodiments are not mutually exclusive combinations of features; rather, the various embodiments can comprise a combination of different individual features selected from different individual embodiments, as understood by persons of ordinary skill in the art. Moreover, elements described with respect to one embodiment can be implemented in other embodiments even when not described in such embodiments unless otherwise noted. 
     Although a dependent claim may refer in the claims to a specific combination with one or more other claims, other embodiments can also include a combination of the dependent claim with the subject matter of each other dependent claim or a combination of one or more features with other dependent or independent claims. Such combinations are proposed herein unless it is stated that a specific combination is not intended. 
     Any incorporation by reference of documents above is limited such that no subject matter is incorporated that is contrary to the explicit disclosure herein. Any incorporation by reference of documents above is further limited such that no claims included in the documents are incorporated by reference herein. Any incorporation by reference of documents above is yet further limited such that any definitions provided in the documents are not incorporated by reference herein unless expressly included herein. 
     For purposes of interpreting the claims, it is expressly intended that the provisions of 35 U.S.C. §112(f) are not to be invoked unless the specific terms “means for” or “step for” are recited in a claim.