Patent Publication Number: US-7900716-B2

Title: Vibratory unit for drilling systems

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/018,945 filed Jan. 4, 2008, which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. The Field of the Invention 
     The present invention relates to drilling systems and to down-hole vibratory units in particular. 
     2. The Relevant Technology 
     Core drilling allows samples of subterranean materials from various depths to be obtained for many purposes. For example, drilling a core sample and testing the retrieved core helps determine what materials are present or are likely to be present in a given formation. For instance, a retrieved core sample can indicate the presence of petroleum, precious metals, and other desirable materials. In some cases, core samples can be used to determine the geological timeline of materials and events. Accordingly, core samples can be used to determine the desirability of further exploration in a given area. 
     Although there are several ways to collect core samples, core-barrel systems are often used for core sample retrieval. Core-barrel systems include an outer tube with a coring drill bit secured to one end. The opposite end of the outer tube is often attached to a drill string that extends vertically to a drill head that is often located above the surface of the earth. The core-barrel systems also often include an inner tube located within the outer tube. As the drill bit cuts formations in the earth, the inner tube can be filled with a core sample. Once a desired amount of a core sample has been cut, the inner tube and core sample can be brought up through the drill string and retrieved at the surface. 
     While such a configuration allows for the retrieval of core samples, the core sample can occasionally become jammed. For example, when using a core-barrel system to retrieve core samples in formations that contain unconsolidated or blocky ground, the core sample can jam or become lodged within the inner tube. This jamming can cause the weight of the drill string to be transferred substantially away from the outer tube to the core sample and the inner tube. This weight transfer can cause the core sample to fracture, which in turn can cause the slow or stop the core drilling operation entirely. Even if drilling continues, the head of the core sample in the bit can mill the formation and render that portion of the formation permanently unrecoverable. Thus, a core sample that is jammed in the inner tube can slow the drilling process and reduce the overall productivity of the drilling process. 
     The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate one exemplary technology area where some embodiments described herein can be practiced 
     BRIEF SUMMARY OF THE INVENTION 
     A down-the-hole vibratory unit for a drilling system includes a casing comprising a fluid inlet, and a plurality of eccentrically weighted rotor assemblies positioned at least partially within the casing and in fluid communication with the inlet, the eccentrically weighted rotor assemblies that are unbalanced relative to a central axis and are configured to rotate in response to a fluid flow directed thereto to apply centrifugal forces to the casing. 
     A core barrel vibratory unit can include a casing comprising a fluid inlet and a fluid outlet, a fluid-driven vibrating mechanism that produces vibrations in a drilling direction without producing any substantial vibrations in a non-drilling direction by rotating multiple rotors that are each unbalanced about a central axis, and a damping mechanism that reduces or eliminates the vibrations before they are transmitted to another part of a drilling system to which the vibrating mechanism is connected. 
     Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or can be learned by the practice of the invention. The features and advantages of the invention can be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. These and other features of the present invention will become more fully apparent from the following description and appended claims, or can be learned by the practice of the invention as set forth hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       To further clarify the above and other advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
         FIG. 1  illustrates a vibratory unit and associated drilling system according to one example; 
         FIG. 2A  illustrates a down-hole assembly according to one example; 
         FIG. 2B  illustrates an exploded view of the down-hole assembly of  FIG. 2A ; 
         FIG. 3A  illustrates a vibratory unit with unbalanced rotors in a first position according to one example; 
         FIG. 3B  illustrates the vibratory unit of  FIG. 3A  with the unbalanced rotors in a second position; 
         FIG. 3C  illustrates the vibratory unit of  FIGS. 3A-3B  with the unbalanced rotors in a third position; 
         FIG. 3D  illustrates the vibratory unit of  FIGS. 3A-3C  with the unbalanced rotors in a fourth position; and 
         FIG. 4  illustrates an exploded view of a vibratory unit according to one example. 
     
    
    
     The figures illustrate specific aspects of the vibratory unit and the associated methods of making and using such a unit. Together with the following description, the figures demonstrate and explain the principles of vibratory unit and these associated methods. In the Figs., the thickness and configuration of components can be exaggerated for clarity. The reference numerals in different figures represent similar, though not necessarily identical, components. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Systems, devices, and methods are provided herein for sampling a formation. In at least one example, a vibratory unit is provided that includes eccentrically weighted rotors. Due to the eccentric weighting of the rotors, as the rotors rotate they generate centrifugal forces. The rotors may be oriented and positioned in such a manner that axial components of the centrifugal forces sum together while radial components cancel each other. Such a configuration can allow a vibratory unit to generate axial, cyclically oscillating centrifugal forces, or axial vibratory forces. These forces can be transmitted to other components of a drilling system, such as a core barrel. The application of axial vibratory forces to a core-barrel system may reduce the possibility that a core barrel will become jammed as the core barrel retrieves a sample from an unconsolidated or loose formation. 
     The following description supplies specific details in order to provide a thorough understanding. Nevertheless, the skilled artisan would understand that the vibratory unit and methods of making and using the device can be implemented and used without employing these specific details. Indeed, the vibratory unit and associated methods can be modified and used in conjunction with any apparatus, systems, components, and/or techniques used in the drilling field. Additionally, while the description below focuses on implementing the vibratory unit with core-barrel systems used to retrieve core samples in unconsolidated or blocky ground, the vibratory unit can be implemented in core-barrel systems used to retrieve core samples from any desired formation, including fragmented, consolidated, soft, conglomerated, sandy, wet, and clay formations. Indeed, the vibratory unit could be used in any down-the-hole application. 
       FIG. 1  illustrates a drilling system  100  that includes a drill head  110 . The drill head  110  can be coupled to a mast  120  that in turn is coupled to a drill rig  130 . The drill head  110  is configured to have a drill rod  140  coupled thereto. The drill rod  140  can in turn couple with additional drill rods to form a drill string  150 . In turn, the drill string  150  can be coupled to a drill bit  160  configured to interface with the material to be drilled, such as a formation  170 . 
     In at least one example, the drill head  110  illustrated in  FIG. 1  is configured to rotate the drill string  150  during a drilling process. In particular, the rotational rate of the drill string  150  can be varied as desired during the drilling process. Further, the drill head  110  can be configured to translate relative to the mast  120  to apply an axial force to the drill head  110  to urge the drill bit  160  into the formation  170  during a drill process. The drilling system  100  also includes a down-the-hole assembly, such as a core-barrel assembly  200 . The down-the-hole assembly  200  includes or has a vibratory unit  210  coupled thereto. In at least one example, the vibratory unit  210  can be located down the borehole between the drill string  150  and the drill bit  160 . 
     The vibratory unit  210  provides a vibratory force relative to at least one direction. For example, the vibratory unit  210  can be configured to provide an axial vibratory force to a down-hole component, such as a core barrel, a radial vibratory force generally perpendicular to the down-hole component, a vibratory force in some other direction, and/or combinations thereof. For ease of reference, the vibratory unit  210  unit will be described as applying an axial force to the core barrel assembly  200  and/or the drill string  150 . 
     In at least one example, the drill head  110 , the drill rig  130 , and/or some other unit can include a pressure generator. The pressure generator can be configured to pressurize a fluid to provide motive power to drive the vibratory unit  210 , as will be described in more detail below. In at least one example, the fluid can include water or other liquids, indicated by waterline  180 . 
     While one configuration is illustrated, it will be appreciated that the vibratory unit  210  can be located at any position along the drill string  150 . Further, while one type of motive power will be described, it will be appreciated that other types of motive power can be provided in any suitable manner, such as by hoses or other devices that are coupled to the vibratory unit  210 . Further, while a core barrel assembly  200  is described, it will be appreciated that the vibratory unit  210  can be part of and/or coupled to any number of down-the-hole assemblies. 
       FIGS. 2A-2B  illustrates the core-barrel assembly  200  in more detail. In particular,  FIG. 2A  illustrates the core-barrel assembly  200  positioned within a formation  170  while  FIG. 2B  illustrates an isolated, exploded view of the core-barrel assembly  200 . As illustrated in  FIG. 2A , the core-barrel assembly  200  includes a head assembly  205 , the vibratory unit  210 , and a core-lifter assembly  215 . 
     In the illustrated example, the core-barrel assembly  200  can be a wire-line type core-barrel assembly. Accordingly, the head assembly  205 , the vibratory unit  210 , and the core lifter assembly  215  can be located at least partially within an outer tube  220 . The drill bit  160  can in turn be coupled secured to the outer tube  220  such that as the outer tube  220  rotates the drill bit  160  also rotates. 
     As illustrated in  FIG. 2B , the head assembly  205  includes a head end  205 A and a bit end  205 B, the vibratory unit  210  includes a head end  210 A and a bit end  210 B, and the core-lifter assembly  215  includes a head end  215 A and a bit end  215 B. In the illustrated example, the core-barrel assembly  200  is wire-line type core-barrel assembly. Accordingly, the head end  205 A of the head assembly  205  can include a spear-point assembly that is configured to engage an overshot. The head assembly  205  can further include latches  225 . 
     As illustrated in  FIG. 2A , the latches  225  are configured to be deployed to thereby secure the core-barrel assembly  200  to the outer tube  220 . Such a configuration causes the core-barrel assembly  200  to rotate with the outer tube  220 . As the outer tube  220  rotates, it forces the drill bit  160  into the formation  170 . As the drill bit  160  rotates, the drill bit  160  cuts the formation  170  thereby forcing a core-sample  20  into the core-lifter assembly  215 . 
     As a core-sample is forced into the core-lifter assembly  215 , the vibratory unit  210  applies a vibratory force to at least the core-lifter assembly  215  in at least one direction to thereby help ensure the core sample does not become jammed within the core-lifter assembly  215 . As previously introduced, the vibratory unit  210  can be powered by any motive force desired. 
     Referring again to  FIG. 2B , the vibratory unit  210  can include one or more eccentrically weighted rotor assemblies (rotor assemblies)  235 ,  235 ′,  235 ″,  235 ′″. As previously introduced, the rotor assemblies  235 - 235 ′″ can be eccentrically weighted. The rotor assemblies  235 - 235 ′″ can be weighted eccentrically in any manner. One or more of the rotor assemblies  235 - 235 ′″ includes a gear  240 ′- 240 ′″. Further, at least one of the rotor assemblies  235 - 235 ′″ includes at least one eccentric weight assembly  245 - 245 ′″ coupled to one of the gears  240 - 240 ′″. 
     In the illustrated example, eccentrically weight assemblies  245 - 245 ′″ are associated with the gears  240 - 240 ′″ respectively. As will be described in more detail below, the eccentric weight assemblies  245 - 245 ′″ cause the rotor assemblies  235 - 235 ′″ to rotate in an unbalanced manner to transmit vibratory forces to at least a portion of the core-barrel assembly  200  ( FIG. 2B ). While one configuration is illustrated that includes separate eccentric weight assemblies  245 - 245 ′″ coupled to a corresponding gear  240 - 240 ′″, it will be appreciated that the eccentric weight assemblies  245 - 245 ′″ can be integrally formed with the gears  240 - 240 ′″. Further, the eccentric weight assemblies  245 - 245 ′″ can be coupled to the gears  240 - 240 ′″ in any manner. Additionally, any number of eccentric weight assemblies  245 - 245 ′″ can be coupled to any of the gears  240 - 240 ′″. 
     The gears  240 - 240 ′″ are operatively associated with a casing  250 . In particular, the gears  240 ,  240 ′″ can be positioned within a compartment  250 C and can rotate about pin assemblies  251 - 251 ′″ that are secured to the casing  250 .  FIG. 2B  illustrates that, for example, the compartment  250 C can be contoured so as to limit space between the compartment  250 C and the rotor assemblies  235 - 235 ′″ so as to limit flow around the rotor assemblies  235 - 235 ′″. In this way, a path of least resistance is created to maximize the amount of fluid that comes in contact with the unbalanced rotors in the desired flow direction. 
     Further, the rotor assemblies  235 - 235 ′″ are positioned within the casing  250  in such a manner that rotor assembly  235  engages rotor assembly  235 ′, which in turn engages rotor assembly  235 ″, which in turn engages rotor assembly  235 ′″. In particular, gear  240  meshes with gear  240 ′, which in turn meshes with gear  240 ′″, which in turn meshes with gear  240 ′″. As a result, gear  240 - 240 ′″ can form a gear chain such that rotation of one gear result in rotation of one or more of the other gears. 
     With continued reference to  FIG. 2B , the vibratory unit  210  can include a nozzle  252  positioned in the casing  250  and in fluid communication with rotor assembly  235 . As a result, fluid passing through the nozzle  252  is directed to rotor assembly  235 . The incidence of the fluid on rotor assembly  235  causes the rotor assembly  235 , including the gear  240  to rotate in the direction indicated by the arrow. The vibratory unit  210  can function in any manner that allows the vibratory unit  210  to vibrate and transmit a vibration to another component, such as the core-lifting assembly  215 . Typically, as a fluid travels down the inside of the drill string, the fluid enters the head end  210 A of the vibratory unit  210 . Although any liquid or gas (both referred to as fluid) used in core drilling can enter the vibratory unit  210 , some non-limiting examples of typical fluids can include water, polymer-based drilling fluid, drilling mud, pneumatic gas, or combinations thereof. 
     Engagement between the gears  240 - 240 ′″ as described above causes the rest of the gears  240 ′- 240 ′″ to rotate in response to rotation of gear  240 . In particular, the vibratory unit  210  includes a connecting joint  254 . The connecting joint  254  can be configured to be coupled to a bit end of an upstream component, such as the bit end  205 B of the head assembly  205 . A damper shaft  256  is seated relative to and extends at least partially through and beyond the connecting joint  254 . The damper shaft  256  is also in fluid communication with a head end   of the casing  250  and with a channel  258  defined in the head end  250 A in particular. The channel  258  in turn is in fluid communication with the nozzle  252 . 
     As a result, a fluid flow entering the vibratory unit passes through the connecting joint  254 , the damper shaft  256  and the channel  258  where it is then directed to the nozzle  252 . From the nozzle  252  is incident on one or more of the rotor assemblies  235 - 235 ′″ to cause the rotor assemblies  235 - 235 ′″ to rotate as described above. The fluid can be outlet from the vibratory unit in any manner desired. For example, the casing can include one or more outlets in communication with the compartment  250 C in the casing  250  described above. These outlets can include head end outlets  259 A and bit end outlets  259 B. Accordingly, fluid directed to the vibratory unit  210  can escape through the outlets  259 A,  259 B as the rotor assemblies  235 - 235 ′″ rotate. 
     The eccentric weighting of the rotor assemblies  235 - 235 ′″ due to the eccentric weight assemblies  245 - 245 ′″ results in an unbalanced centrifugal force acting away from a center of the rotor assemblies  235 - 235 ′″. Continued rotation of the rotor assemblies  235 - 235 ′″ results in a cyclical force in one or more direction. This cyclical force can be transmitted to other portions of the core-barrel assembly  200 , such as core-lifter assembly  215 . For ease of reference, one configuration of the vibratory unit  210  will be discussed in which the cyclical force is transmitted primarily in an axial direction. It will be appreciated that other configurations are possible to transmit the cyclical force in a desired direction, such as a radial direction, angular directions, or combinations thereof. 
       FIGS. 3A-3D  illustrate the vibratory unit  210  as the rotors  235 - 235 ′″ in first, second, third, and fourth positions as the rotors  235 - 235 ′″ move through a complete revolution in which the first position is an initial position and each of the subsequent positions represent approximately 90 degrees of rotation of each of the rotor assemblies  235 - 235 ′″. In  FIGS. 3A-3D , centrifugal forces acting on the rotor assemblies  235 - 235 ′″ are represented generally as F-F′″ respectively. The centrifugal forces can further be characterized as including an axial component that acts parallel to the drilling direction and a radial component that acts perpendicular to the axial component. 
     As illustrated in  FIG. 3A , the radial component of the centrifugal forces F-F′″ are the primary components. Further, as illustrated in  FIG. 3A , the radial component of forces F and F″ act in a radially opposite direction as centrifugal forces F′ and F′″. Accordingly, in the first position the centrifugal forces and the radial components in particular, cancel one another. As the rotor assemblies  235 - 235 ′″ move toward the position in  FIG. 3B , rotor assemblies  235  and  235 ″ move in the opposite direction of rotor assemblies  235 ′ and  235 ′″. As a result, the radial component of centrifugal forces F-F′″ will continue to cancel each other out. While the radial component of the centrifugal forces F-F′″ act opposite each other to cancel each other, the axial components of the centrifugal forces F-F′″ act in the same direction as the rotor assemblies  235 - 235 ′″ rotate toward the positions illustrated in  FIG. 3B . 
     The axial components of the centrifugal forces F-F′″ increase to a maximum value while the radial components are at a minimum value, such as when the rotor assemblies  235 - 235 ′″ are at the position shown in  FIG. 3B . In the position shown in  FIG. 3B , the centrifugal forces F-F′″ act axially toward the bit end  210 B. As previously introduced, pin assemblies  251  couple the rotor assemblies  235 - 235 ′″ to the casing  250 . The pin assemblies  251  further transmit the centrifugal forces F-F′″, and the axial components in particular, to the casing  250 . The casing  250  in turn transmits the centrifugal forces F-F′″ to other components, including the core-lifting assembly  215  ( FIG. 2A ). 
     As the rotor assemblies  235 - 235 ′″ rotate to the third position illustrated in  FIG. 3C , the axial components of the centrifugal forces F-F′″ decrease while the radial components increase to a maximum value at the position shown in  FIG. 3C . As previously introduced, while the radial components of the centrifugal forces F-F′″ increase they are in opposite directions and can be generally equal so as to cancel each other out. As a result, while the rotor assemblies  235 - 235 ′″ are at the position shown in  FIG. 3C , the centrifugal forces F-F′″ cancel each other out while at a maximum. 
     As the rotor assemblies  235 - 235 ′″ continue to rotate to the position shown in  FIG. 3D , the radial components of the centrifugal forces F-F′″ will continue to cancel each other out as they decrease while the radial components will increase. The radial components act together axially toward the head end  210 A. The axial components will decrease and the radial components will increase and cancel each other out as the rotor assemblies  235 - 235 ′″ return to the position shown in  FIG. 3A . 
     Accordingly, in at least one example, axial components of the centrifugal forces F-F′″ generated due to unbalanced rotation of the rotor assemblies  235 - 235 ′″ will oscillate between a maximum force directed toward the bit end  210 B and a maximum force directed toward the head end  210 A while radial components of the centrifugal forces F-F′″ substantially cancel one another. Accordingly, rotation of the rotor assemblies  235 - 235 ′″ results in cyclical axial forces. The cyclical axial forces can also be described as vibratory forces. In some example, it can be desirable to transmit the vibratory forces axially toward the head end  210 A and the bit end  210 B. 
     In other examples, it can be desirable to transmit the axial forces to components to one of the head end  210 A or the bit end  210 B and to isolate other components from axial forces in the other direction. Accordingly, it can be desirable for the vibratory unit  210  to damp axial forces. In at least one example, the vibratory unit  210  can include means for damping or isolating forces that would otherwise be transmitted in a selected direction, such as toward the head assembly  205  ( FIG. 2B ). In the illustrated example, the damping means includes at least one shock absorber  260  located at least partially between the inlet joint  254  and the casing  250 . Means for damping forces can also include vibratory isolators, pads, dampers, damping shaft, rubber bushings, shock absorbers, grommets, crash stops, gaskets, seals, and/or other suitable components that damp, isolate, and/or absorb vibration. Additionally, the components of the damping mechanism can be made of any suitable material that damps vibration. Some non-limiting examples of vibration damping materials can include one or more rubbers, polymers, composites, etc. 
     Further, the damping means can be disposed in any desired location, such as any location that allows the mechanism to damp vibrations before they reach the latches  225  in the core barrel head assembly  200  (both shown in  FIGS. 2A and 2B ). In the illustrated example, the shock absorber  260  and/or other damping components are substantially exposed from the casing  250 . In other examples, the damping mechanism can be substantially disposed within the casing  250 . In still other embodiments, however, a portion of the damping mechanism can be disposed within the casing  250  while another portion of the damping mechanism is exposed from the casing  250 . 
       FIG. 4  illustrates additional components of the vibratory unit  210  in more detail. These components and their assembly will now be described in more detail. In the illustrated example, the casing  250  includes a main body  400  and a cover  405 . Further, as illustrated in  FIG. 4 , each of the rotor assemblies  235 - 235 ′″ can be substantially similar. Accordingly, in at least one example the discussion of rotor assembly  235  can be applicable to rotor assemblies  235 ′- 235 ′″. 
     In the illustrated example, rotor assembly  235  includes gear  240 , an eccentric weight  410  and one or more insert  415 . The inserts  415  can be secured to the eccentric weight  410  and the gear  240  in suitable manner, such as by way of spring pins  420 . The gear  240  and the eccentric weight  410  can have complimentary shapes that allow the gear  240  to receive at least a portion of the eccentric weight  410 . One such shape of the gear  240  includes a recessed gear. Such a configuration may increase the weight eccentricity of the rotor assembly  235  as a relatively large percentage of the rotor assembly  235  may be associated with the eccentric weight  410  and the inserts  415 . 
     As previously introduced, the rotor assembly  235  is configured to rotate about pin assemblies  251 . The pin assembly  251  shown includes a shaft  425  and a roller bearing  430 . The shaft  425  can be secured to the casing  250  as described above. The roller bearings  430  may reduce the friction associated with rotation of the rotor assembly  235  in response to a fluid flow. 
     The vibratory unit  210  may also include a filter screen  440  placed upstream of the rotor assemblies  235 - 235 ′″. The filter screen  440  may be configured to capture particulates within the fluid stream to prevent the particulates from entering the recess in the casing  250 . As previously introduced, the casing  250  may include outlets defined therein. In addition to providing an inlet to drive the rotor assemblies  235 - 235 ′″, an inlet  455  may be provided in the bit end  210 B. The inlet  455  can have a ball  460  associated therewith to form a check valve. The ball  460  is maintained in proximity with the inlet  455  by way of a check valve pin  465 . With such a configuration, the ball  460  remains in contact with the inlet  455  as fluid enters from the head end  210 A but is moved out of contact with the hole when fluid is introduced from the bit end  210 B. By allowing fluid to flow through the compartment  250 C, the ball  460  and inlet  455  can operate as a check valve to decrease resistance and allow the core barrel assembly  200  to travel through the drill string faster and easier. When the head assembly  205  and vibratory unit  210  are being retrieved, the check valve can also prevent fluid from exerting pressure down on the proximal end of the core sample. In this manner, the check valve can help avoid causing a core sample to be dislodged and lost from the core lifting assembly  215 . Instead, the check valve can force fluid to exit through the fluid outlet(s)  259 A,  259 B located on the sides of the vibratory unit  210 . The fluid can then flow around the outside of the core lifting assembly  215  and vibratory unit  210  without dislodging the core sample. 
     In at least one example, each of the components described above may be separately formed through any desired process. Once the individual components have been prepared they may be assembled as desired. For example, the rotor assemblies  235 - 235 ′″ may be assembled and then have the pin assemblies  251  coupled thereto. The rotor assemblies  235 - 235 ′″ and the pin assemblies may then be positioned relative to the main body  400 . The nozzle  252  can also be positioned relative to the main body  400 , such that the nozzle  252  is in communication with the channel  258 . The ball  460  may also be positioned relative to the main body  400 . Thereafter, the cover  405  can be secured to the main body  400  to form the assembled casing  250 . The filter screen  440  can then be positioned relative to the head end   of the casing, after which the damper shaft  256  can be passed through the inlet joint  254  and the shock absorber  260  and into engagement with the head end  250 A of the casing. The vibratory unit  210  and its constituent components can be made in any suitable manner. For example, the various components of the vibratory unit  210  can be molded, extruded, stamped, etc. Additionally, the various components of the vibratory unit  210  can be connected to each other in any appropriate manner. Some non-limiting examples of methods for connecting the components of the vibratory unit  210  can include mechanically fastening, welding, clampingly fastening, or otherwise fastening the components together to form an assembled vibratory unit  210 . For example,  FIG. 4   a  depicts that fasteners  465 , as well as the threaded connector joints can be used to connect the components of the vibratory unit  210  together. While such steps are described, they are provided by way of illustration only and not by way of limitation. 
     Further, the casing  250  can have any characteristic or component that allows the vibratory unit to be connected to a drill system, including a core barrel assembly and to vibrate within the inner tube so that the core sample is aided to slide up within the inner tube. For instance, the casing  250  can be any shape that allows the casing  250  to house the rotor assemblies  235 A and still fit within the outer tube  200  ( FIG. 2A ). In some non-limiting examples, the casing  250  can be substantially cylindrical. For example, the exploded view of the vibratory unit  210  in  FIG. 4  illustrates that the casing  250  can be substantially cylindrical in shape. In some embodiments, the casing  250  can have a diameter that is substantially smaller than the diameter of the core-lifting assembly  215  and/or head assembly  205 . Further, the casing  250  can be any length that allows the casing  250  to house one or more rotor assemblies  235 . While one example is illustrated, it will be appreciated that the casing  250  can comprise more or less pieces than are illustrated in the Figures and that the casing  250  can be split in any manner desired. 
     The vibratory unit  210  can comprise any fluid-driven mechanism that produces dynamic forces in the desired drilling direction. In the embodiments illustrated in the Figures, the fluid-driven vibrating mechanism can comprise one or more unbalanced rotors, or rotors that are unbalanced about their central axis or a central point of the rotor assembly  235  about which the rotor rotates. Some non-limiting examples of suitable rotors can include waterwheels, turbines, the aforementioned gear rotors, or any other mechanism comprising a rotor with vanes, buckets, blades, paddles, etc. where the mechanism is driven by the pressure, momentum, and/or reactive thrust of a moving fluid, occurring as the fluid passes through and/or fills the compartment  250 C around the rotor. Further, the vibratory unit  210  can have any number of rotors that are unbalanced about their central axis  130  (shown in  FIG. 1 ). For example, the vibrating mechanism can comprise as few as 1 or 2 unbalanced rotors, or as many unbalanced rotors as the hole depth allows. 
     Similarly, rotor assemblies  235 - 235 ′″ can have any unbalanced characteristic that allows one section of the rotor to weigh more than another. Some non-limiting examples of rotor characteristics that can cause an unbalance in the rotor can include connecting or forming the previously mentioned offset weight on one section of the rotor; forming a section of the rotor with a heavier material than the material used to form the rest of the rotor; having one section of the rotor contain more material than the rest of the rotor contains; or removing material from one section of the rotor. 
     The present invention can be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.