Patent Publication Number: US-11384603-B1

Title: Rotational vibration absorber with tangential dampers cap

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     None. 
     TECHNICAL FIELD/FIELD OF THE DISCLOSURE 
     The present disclosure relates generally to damping vibrations or rotational oscillations during drilling operations using rotary steerable systems, and specifically to inertial damping systems converting vibration energy into heat energy, resulting in the desired damping effect. 
     BACKGROUND OF THE DISCLOSURE 
     In hydrocarbon drilling operations, boreholes are typically drilled by rotating a drill bit attached to the end of a drill string. The drill bit can be rotated by rotating the drill string at the surface and/or by a fluid-driven downhole mud motor, which may be part of a bottom hole assembly (BHA). For example, a mud motor may be used when directional drilling using a rotary steerable system (RSS). The combination of forces and moments applied by the drill string and/or mud motor and forces and moments resulting from the interaction of the drill bit with the formation can have undesirable effects on the drilling system, including reducing the effectiveness of the cutting action, damage to BHA components, reduction in BHA components&#39; life, and interference in measuring various drilling parameters. 
     SUMMARY 
     To mitigate such negative effects, a BHA may be equipped with a damping system to draw vibration energy from the BHA and thereby damping the effects associated with torsional vibration excitation. A vibration damping device may be used with and adapted for use with a downhole tool. The downhole tool may have a tool axis and may include a drill string component. 
     A vibration damping device may comprise a body integral with or mechanically coupled to the drill string component, an inertial mass slidably disposed in the lateral bore, and a cap mechanically coupled to the lateral bore. The body may include a longitudinal bore therethrough and at least one lateral bore, the lateral bore having a bore opening and an end wall. The lateral bore may be orthogonal to a radius of the body and lies in a plane normal to the tool axis. The body may include a plurality of lateral bores in a co-planar arrangement or a plurality of co-planar arrangements. Each lateral bore may be a blind hole and may be positioned in the body so that it does not intersect the longitudinal bore or another lateral bore. The cap may enclose the bore opening. 
     The device may further include a first biasing means positioned between one end of the inertial mass and the lateral bore and a second biasing means positioned between another end of the inertial mass and the cap. The lateral bore may be a stepped hole comprising a first bore section and a second bore section. The second bore section may define the inner end of the lateral bore and may have a smaller diameter than the first bore section, and one end of the first biasing means may be disposed in the second bore section. 
     The cap and the lateral bore may define a bore chamber and a portion of the bore chamber that is not occupied by the inertial mass may be occupied by a liquid. The device may further include a cartridge housing disposed in and mechanically coupled to the lateral bore. The cap may enclose the cartridge housing and define a bore chamber therewith, and the inertial mass may be slidably disposed in the bore chamber. The device may further include a first biasing means positioned between one end of the inertial mass and the cartridge and a second biasing means positioned between another end of the inertial mass and the cap. 
     A portion of the bore chamber not occupied by the inertial mass may be occupied by a liquid. The inertial mass may include at least one fluid passage therethrough. Each lateral bore may further include a fluid-filled piston chamber and each inertial mass may include a piston extending into the piston chamber. The piston may include fluid orifices therethrough such that as the piston reciprocates within the piston chamber, fluid in the piston chamber flows through the orifices. The fluid in the piston chamber may be the same or different from the fluid in the bore chamber. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion. 
         FIG. 1  is a schematic view of a drilling system in which embodiments of the current invention can be used. 
         FIGS. 2-4  schematically illustrate possible locations for a damping device and its different setups for installation in a drilling system. 
         FIGS. 5-7  schematically illustrate additional possible locations for a damping device and its different setups for installation in a drilling system. 
         FIG. 8  is a view of a device in accordance with an embodiment of the invention. 
         FIG. 9  is cross-section along lines  9 - 9  of  FIG. 8 . 
         FIGS. 10A-C  are three cross-sectional views of a component of a device in accordance with an alternative embodiment of the invention, showing the component in three different operating positions (neutral, maximum right, maximum left). 
         FIG. 11  is cross-section of a device in accordance with an alternative embodiment of the invention. 
         FIG. 12  is cross-section of a device in accordance with another alternative embodiment of the invention. 
         FIG. 13  is a schematic illustration of torsional vibrational nodes of part of a drill string. 
         FIGS. 14A and 14B  are plots of models illustrating damping of torsional vibration at target frequencies. 
     
    
    
     DETAILED DESCRIPTION 
     It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of various embodiments. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. 
     The present disclosure hereby includes the concepts and features described in U.S. Application Ser. No. 62/952,233, filed Dec. 21, 2019 and entitled “Method and Apparatus for Damping/Absorbing Rotational Vibrations/Oscillations,” and U.S. Application Ser. No. 62/976,898, filed Feb. 14, 2020 and entitled “Method and Apparatus for Damping/Absorbing Rotational Vibrations/Oscillations,” each of which is hereby incorporated herein in its entirety. 
     Referring initially to  FIG. 1 , a drilling system  100  in which the present apparatus may be used may include a drilling rig  101  positioned above a wellbore  102  that extends into a subsurface formation  110 . A drill string  105  may extend from drilling rig  101  into wellbore  102  and may terminate in a bottom hole assembly (BHA)  103 . Drill string  105  may be driven by the surface equipment of the rig. In some embodiments, BHA  103  may include a drill bit  107 , a motor  106 , which may be a mud motor or other downhole motor, and a steerable system  104 , which may be a rotary steerable system (RSS). BHA  103  may optionally include various other devices, such as logging or measurement devices, communications devices, and the like. If present, steerable system  104  may be used to steer the bit as the wellbore is drilled. The rotational force (torque) required to rotate drill bit  107  can be provided by a torque creating or applying apparatus, which may be a drill string  105 , motor  106 , or a combination thereof. 
     According to  FIGS. 2-4 , in some embodiments, one or more damping devices  10  may be positioned between the torque applying or creating apparatus and drill bit  107 . By way of example only, a damping device  10  may be positioned between drill string  105  and drill bit  107  or between steerable system  104  and drill bit  107 . Alternatively or additionally, a damping device may be part of the drill bit. In  FIG. 2 , damping device  10  is integrated in BHA  103 . In  FIG. 3 , damping device  10  is provided on one or more standalone subs as an add-on to BHA  103 .  FIG. 3  shows a “modular” device, in which the functional features can be selectively added or removed at a rigsite.  FIG. 4  shows a setup in which the functional features are integrated into a different component of the BHA (e.g. a stabilizer or a flex sub). If the damping device is included (integrated) in the BHA, adding or removing the damping device at the rigsite is only possible if the entire BHA component is added or removed. The optimal position of the damping device depends on a multitude of parameters. Optimal efficacy is reached when placed at an anti-node of the respective modal-shape. 
     The damping device may be part of any BHA component.  FIGS. 5-7  show various possible locations for the damping device  10  in the drillstring. Specifically,  FIG. 5  shows several possible locations for the damping device  10  on a motor driven RSS BHA.  FIG. 6  shows several possible locations for damping device  10  on a conventional motor driven BHA.  FIG. 7  shows several possible locations for damping device  10  on a conventional BHA without motor and RSS. 
     Referring now to  FIGS. 8 and 9 , some embodiments of the present damping device  10  may comprise a body  20  and at least one energy-absorbing damping cartridge  40  disposed therein. Body  20  is generally cylindrical and has an outer surface  22 , wall  24 , longitudinal axis  25 , and central bore  26 . Body  20  may form a portion of drill string  105  or may be mechanically coupled to or integral with drill string  105  such that rotational vibrations of the drill string  105  are transmitted to body  20 . 
     Body  20  may include at least one lateral bore  30  extending from outer surface  22  of body  20  into wall  24 . In some embodiments, each lateral bore  30  may be orthogonal to a radius of body  20  and lie in a plane normal to longitudinal axis  25 . In some embodiments, body  20  may include a plurality of bores  30  located in a plane, i.e. at the same point along the longitudinal axis of body  20  and may include a plurality of such co-planar arrangements. In the embodiment shown in  FIG. 8 , body  20  includes three sets of three co-planar bores. 
     As best illustrated in  FIG. 9 , each bore may be a blind hole and may be positioned in body  20  so that it does not intersect central bore  26  or another lateral bore. Each lateral bore  30  has an opening  31  and may be formed in body  20  by any suitable method, including but not limited to casting or machining. In some embodiments, each lateral bore  30  may be a stepped hole, having a first bore section  32  and a second bore section  34 . Second bore section  34  defines the inner end of lateral bore  30  and has a smaller diameter than the first bore section  32 . Each bore may also include a countersink  35 . Opposite the opening  31  lateral bore  30  has an end wall  38 . If lateral bore  30  is a stepped hole, end wall  38  may be defined at the interface of first and second bore sections  32 ,  34 . 
     In some embodiments, a damping cartridge  40  may be received in and mechanically coupled to each lateral bore  30 . Each damping cartridge  40  may be retained in its respective bore  30  by any suitable means, including but not limited to friction, adhesive, set screws, and/or threads. Damping cartridge  40  may include a cartridge housing  49  having a first body section  42  and a second body section  44  having a smaller diameter than the first body section  42 . Second body section  44  is adjacent to first body section  42  and a shoulder  48  is defined at the interface of first and second body sections  42 ,  44 . First body section  42  may have inner and outer surfaces  41 ,  43 , respectively. In some embodiments, first body section  42  may be sized such that outer surface  43  forms a friction fit with first bore section  32  of lateral bore  30 . Similarly, second body section  44  may have inner and outer surfaces  45 ,  47 , respectively. In some embodiments, second body section  44  may be sized such that outer surface  47  forms a friction fit with second bore section  34  of lateral bore  30 . Damping cartridge  40  may be positioned in lateral bore  30  so that first body section  42  is disposed with first bore section  32 , second body section  44  is disposed with second bore section  34 , and shoulder  48  abuts end wall  38 . 
     Damping device  10  may further include a cap  60  affixed to and enclosing cartridge housing  49 . Together, cartridge housing  49  and cap  60  define a bore chamber  62 . 
     Still referring to  FIG. 9 , each damping cartridge  40  may also include an inertial mass  50  slidably disposed in first body section  42  of cartridge housing  49 . Inertial mass  50  may include one or more fluid passages  52  therethrough and may have a longitudinal dimension that is less than the longitudinal dimension of first body section  42 , so as to allow inertial mass  50  to shift longitudinally within cartridge housing  49 . Shifting may be the result of alternating forces applied to damping cartridge  40  as a result of rotational vibration of damping device  10  as illustrated at arrow  55  in  FIG. 8 . In some embodiments, one or more energy-storing and/or energy-absorbing biasing members may be positioned between the ends of inertial mass  50  and the ends of bore chamber  62 . In the embodiment illustrated in  FIG. 9 , each end of inertial mass  50  includes a recess  54   a ,  54   b . A coil spring  65  is positioned in each recess and serves as a biasing member. One coil spring extends from recess  54   a  into second body section  44  and the other coil spring extends from recess  54   b  into a corresponding recess in cap  60 . 
     The portion of each bore chamber  62  that is not occupied by inertial mass  50  or optional elastomeric members may be occupied by a damping fluid and/or one or more elastomeric members. The fluid may be a specifically selected damping fluid, such as a viscous medium including, for example, silicone oil. The damping fluid may have a high viscosity, such as for example up to 1,000,000 cSt at 25° C. In some embodiments, body  20 , inertial mass  50 , and/or cap  60  may include ports and/or channels (not shown) for evacuating or filling chambers  62 ,  82  and/or  83  with damping fluid. Such damping fluid and/or elastomeric members may absorb energy from the movement of inertial mass  50  and dissipate it as heat. In some embodiments, inertial mass  50  may comprise multiple stacked pieces arranged within first body section  42 . In other embodiments, inertial mass  50  may include one or more surface features, such as fins, that serve to resist movement of inertial mass  50  through a fluid. 
     In some embodiments, a volume compensation element  68  may be included in bore chamber  62 . The damping fluid may expand and contract, depending on surrounding pressure and temperature. To allow an equalization of pressure between bore chamber  62  and the annulus, the volume needs to adapt. Volume compensation element  68  may comprise a compressible elastomeric element, variable-volume gas-containing enclosed chamber, volume-adjusting piston, or any other suitable device. 
     Referring now to  FIGS. 10A-C , the operation of damping device  10  is illustrated. As the drill string rotates in the borehole, such as during drilling, it may be subject to rotational vibrations, indicated by arrow  55  in  FIG. 8 . The rotational vibrations may cause inertial mass  50  to oscillate between positions within damping cartridge  40 . In  FIG. 10A , inertial mass  50  is in a neutral position. In  FIG. 10B , inertial mass  50  has shifted to the right (as drawn), and in  FIG. 10C , inertial mass  50  has shifted to the left (as drawn). Movement of inertial mass  50  within damping cartridge  40  may be limited by more energy-storing and/or energy-absorbing members such as springs  65 , if present or by contact with shoulder  48  and cap  60 . Movement of inertial mass  50  within damping cartridge  40  changes the relative volumes of first and second chamber portions  62   a ,  62   b . The resulting pressure differential causes fluid to flow from whichever chamber portion is shrinking through fluid passage  52  to the chamber portion that is expanding. In addition to fluid passage  52 , fluid may also flow between chamber portions between inertial mass  50  and inner surface  41  of cartridge housing  49 . During oscillation, fluid may flow back and forth between first and second chamber portions  62   a ,  62   b . Friction within the fluid and between the fluid and the solid components of damping device  10  converts some of the vibrational energy into heat, thereby damping the oscillation. 
     In some instances, it may be desired to include one or more adjustable flow restrictors in one or more of the fluid flow paths. Higher restriction causes higher damping and a stiffer characteristic. The desired damping characteristic may be tunable and may require an adjustment of one or more factors including but not limited to restriction, fluid viscosity, spring stiffness, inertia, and the like. In some embodiments, it may be desirable to provide a magnetorheological fluid in each bore chamber  62  and to adjust the properties of the magnetorheological fluid by applying a variable magnetic field across all or a portion of damping device  10 . 
     In some embodiments, all or a portion of one or more bore chambers  62  may be also occupied by an elastomer or one or more elastomeric bodies. The elastomer may have specific elastic and damping properties so that it can deform and dissipate energy while deforming. For both choices (a high viscosity fluid and an elastomer) it is required that the molecular chains of the material move relative to each other so as to dissipate energy. 
     Referring now to  FIG. 11 , an alternative embodiment is illustrated, in which each co-planar set of damping cartridges comprises two, instead of three damping cartridges. Further, in the embodiment of  FIG. 11 , cartridges  40  are omitted and each damping cartridge comprises inertial mass  50  and a cap  60  positioned in a lateral bore  30 . Cap  60  may cooperate with lateral bore  30  to define an alternative form of bore chamber  82 . The portion of bore chamber  82  not occupied by inertial mass  50  may be occupied by a fluid and or one or more elastomeric members (not shown). Cap  60  and lateral bore  30  may each include a recess for receiving a biasing member such as springs  65 . 
     It may be desirable to tune the components of each damping device so as to achieve damping over a broader range of frequencies. In some embodiments, damping device  10  may be tuned to an eigenfrequency that matches one or more eigenfrequencies of the system to which it is mechanically coupled. 
     Parameters that can be adjusted as part of the tuning process may include but are not limited to: the mass, material, and configuration of inertial mass  50 , the size and configuration of fluid passage  52  therethrough, the width and length of any shear gap, various coefficients of friction, preload, the distance between lateral bore  30  and axis  25 , the number of damping cartridges  40 , the properties of the optional biasing members, and the properties of any fluid and/or elastomeric members included in chambers  62 ,  82 . Damping device  10  may be provided as an integral part of the BHA or one of its components, where all needed elements are integrated into readily available tools, or damping device  10  may be provided as a module or unit separate from the BHA. 
       FIG. 12  shows another alternative embodiment, in which each lateral bore includes a fluid-filled piston chamber  83  at its inner end and each inertial mass  50  includes a piston  89  extending into piston chamber  83 . As inertial mass  50  reciprocates within lateral bore  30 , piston  89  reciprocates within piston chamber  83 . Fluid in piston chamber  83  may flow through orifices  88  in piston  89  and/or may flow around the perimeter of piston  89 . Movement of piston  89  through the fluid in piston chamber  83  results in frictional energy loss. As in  FIG. 11 , the portion of bore chamber  62  not occupied by inertial mass  50  may also be occupied by a fluid and or one or more elastomeric members (not shown). The fluid in piston chamber  83  may be the same or different from the fluid in bore chamber  62 ; if the fluids are different, piston  89  may extend through a sealed opening in the end wall of lateral bore  30 . One or more biasing members such as springs  65  may be included between inertial mass  50  and/or cap  60  and lateral bore  30 . 
     Referring again to  FIGS. 2-7 , a damping device  10  can be used to increase the reliability of an RSS and/or components of the RSS or BHA. Damping device  10  is especially advantageous in operations that have no designated vibration damping drill string component. Damping device  10  can be integrated into a drill string as a separate device, and/or as a separate device positioned within another drill string member (cartridge), or by integrating its components into a torque-transmitting member of the drill string. 
     It may be desirable to tune the components of each damping device so as to achieve damping over a broader range of frequencies. In some embodiments, damping device  10  may be tuned to an eigenfrequency that matches one or more eigenfrequencies of the system to which it is mechanically coupled. 
     In some embodiments, damping device  10  can be tuned to at least one torsional natural frequency of the tool or component it is intended to protect, which may include, for example, the BHA, RSS, or other components of the RSS. In these embodiments, the tool or component is modeled and its natural frequency(ies) is(are) calculated. 
     According to some embodiments, damping device  10  can be adapted to a drill string or component thereof using the following steps:
         a) Calculate the torsional natural frequencies, also referred to as Eigen Values or eigenfrequencies, and mode shapes (Eigen Vectors) based on the mechanical properties of the BHA (ODs, IDs, Lengths, and Material Properties). The calculation may be based on a finite elements analysis or the like. Boundary conditions may be selected such that the system being examined is free to rotate at one end and can be fixed, free, or weakly supported at the opposite end.   b) Tune the damping device characteristics to match the desired frequencies. Each damping device  10  will have frequency dependent damping properties; tuning entails adjusting the frequency dependent damping properties of the device to correspond to the at least one desired frequency. The frequency dependent damping properties can be adjusted by adjusting one or more parameters including the inertia (mass, material density, lever to axis of rotation, etc.) and damping characteristics (type of fluid, fluid viscosity, shear gap width, shear gap length, coefficient of friction, preload, etc.) of the damping device. In some instances, the target frequency may be from 30 Hz up to 1000 Hz. The tuning may be carried out empirically or using mathematical models.   c) Use the calculated mode shapes to select a location for the damping device. As illustrated schematically in  FIG. 13 , for a given tool and frequency, a mathematical model can be used to calculate the amplitude of vibration at each point along the tool. As illustrated in  FIG. 13 , the amplitude will tend to vary between antinodes A 1 , A 2 , A 3  . . . , i.e. points along the Eigen Vector in which the amplitude is a local maximum or minimum, along the length of the tool, with a node N (zero value) between each pair of adjacent antinodes. Depending on the tool, the antinodes may increase or diminish in amplitude along the length of the tool, with the greatest amplitude (greatest maximum) being closest to one end of the tool.       

     In some embodiments, it may be advantageous to position a damping device  10  at each of one or more anti-nodes. In some instances, it may be desirable to position a damping device  10  close to or at the point with the largest absolute value of modal displacement.  FIG. 14  illustrates damping of torsional vibration measured in degrees ( FIG. 14A ) and rpm ( FIG. 14B ). 
     A system including one or more damping devices may be configured to damp vibrations at one or more frequencies. In some embodiments, damping devices tuned to different frequencies can be used to damp multiple (separate) frequencies. In other embodiments, a single damping device that is capable of damping a broad range of frequencies can be used. The effective frequency range of a damping device can be influenced by various parameters, as set out above. 
     The purpose of the present damping device is to protect the BHA, or certain parts of said BHA, from torsional vibrations that exceed detrimental magnitudes. In some instances, the device may be used for damping loads that occur during drilling operation, such as torque peaks and/or torsional accelerations/oscillations. A drilling system may include one or a plurality of said damping devices in different locations. The damping device can be an integral part of the BHA or one of its components, where all needed elements are integrated into readily available tools. It can also be added to the BHA as a separate device (module), where all elements are integrated into a tool on its own. 
     The foregoing outlines features of several embodiments so that a person of ordinary skill in the art may better understand the aspects of the present disclosure. Such features may be replaced by any one of numerous equivalent alternatives, only some of which are disclosed herein. One of ordinary skill in the art may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. One of ordinary skill in the art may make various changes, substitutions, and alterations without departing from the scope of the present disclosure.