Abstract:
A wedging apparatus including an outer polygonal surface configured to secure a screen to a shaker, the outer polygonal surface having a bottom surface, a top surface opposite the bottom surface, and at least one end surface joining the top surface and the bottom surface, and an inner core defined by the outer polygonal surface, wherein the inner core defines a cavity is disclosed. A method of forming an apparatus for securing a screen to a shaker is disclosed, the method including forming a mold of a wedging apparatus configured to secure a screen to a shaker, wherein a shape of the mod is an inverse of an outer polygonal surface having a bottom surface, a top surface opposite the bottom surface, and at least one end surface joining the top surface and the bottom surface, and an inner core defined by the outer polygonal surface, wherein the inner core defines a cavity, injecting a liquid resin into the mold, allowing the liquid resin to solidify, and removing the wedging apparatus from the mold.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application, pursuant to 35 U.S.C. § 119(e), claims priority to U.S. Provisional Application Ser. No. 60/827,582, filed Sep. 29, 2006. That application is incorporated by reference in its entirety. 
     
     BACKGROUND 
       [0002]    1. Field of the Invention 
         [0003]    The present disclosure relates generally to apparatuses for securing a shaker screen to a shaker. In particular, the present disclosure relates to wedging apparatuses and methods of forming wedging apparatuses. 
         [0004]    2. Background Art 
         [0005]    Oilfield drilling fluid, often called “mud,” serves multiple purposes in the industry. Among its many functions, the drilling mud acts as a lubricant to cool rotary drill bits and facilitate faster cutting rates. Typically, the mud is mixed at the surface and pumped downhole at high pressure to the drill bit through a bore of the drillstring. Once the mud reaches the drill bit, it exits through various nozzles and ports where it lubricates and cools the drill bit. After exiting through the nozzles, the “spent” fluid returns to the surface through an annulus formed between the drillstring and the drilled wellbore. 
         [0006]    Drilling mud provides a column of hydrostatic pressure, or head, to prevent “blow out” of the well being drilled. This hydrostatic pressure offsets formation pressures thereby preventing fluids from blowing out if pressurized deposits in the formation are breached. Two factors contributing to the hydrostatic pressure of the drilling mud column are the height (or depth) of the column (i.e., the vertical distance from the surface to the bottom of the wellbore) itself and the density (or its inverse, specific gravity) of the fluid used. Depending on the type and construction of the formation to be drilled, various weighting and lubrication agents are mixed into the drilling mud to obtain the right mixture. Typically, drilling mud weight is reported in “pounds,” short for pounds per gallon. Generally, increasing the amount of weighting agent solute dissolved in the mud base will create a heavier drilling mud. Drilling mud that is too light may not protect the formation from blow outs, and drilling mud that is too heavy may over invade the formation. Therefore, much time and consideration is spent to ensure the mud mixture is optimal. Because the mud evaluation and mixture process is time consuming and expensive, drillers and service companies prefer to reclaim the returned drilling mud and recycle it for continued use. 
         [0007]    Another significant purpose of the drilling mud is to carry the cuttings away from the drill bit at the bottom of the borehole to the surface. As a drill bit pulverizes or scrapes the rock formation at the bottom of the borehole, small pieces of solid material are left behind. The drilling fluid exiting the nozzles at the bit acts to stir-up and carry the solid particles of rock and formation to the surface within the annulus between the drillstring and the borehole. Therefore, the fluid exiting the borehole from the annulus is a slurry of formation cuttings in drilling mud. Before the mud can be recycled and re-pumped down through nozzles of the drill bit, the cutting particulates must be removed. 
         [0008]    One type of apparatus used to remove cuttings and other solid particulates from drilling mud is commonly referred to in the industry as a “shale shaker.” A shale shaker, also known as a vibratory separator, is a vibrating sieve-like table upon which returning used drilling mud is deposited and through which substantially cleaner drilling mud emerges. Typically, the shale shaker is an angled table with a generally perforated filter screen bottom. Returning drilling mud is deposited at the top of the shale shaker. As the drilling mud travels down the incline toward the lower end, the fluid falls through the perforations to a reservoir below thereby leaving the solid particulate material behind. The combination of the angle of inclination with the vibrating action of the shale shaker table enables the solid particles left behind to flow until they fall off the lower end of the shaker table. 
         [0009]    The above described apparatus is illustrative of one type of shale shaker known to those of ordinary skill in the art. In alternate shale shakers, the top edge of the shaker may be relatively closer to the ground than the lower end. In such shale shakers, the angle of inclination may require the movement of particulates in a generally upward direction. In still other shale shakers, the table may not be angled, thus the vibrating action of the shaker alone may enable particle/fluid separation. Regardless, table inclination and/or design variations of existing shale shakers should not be considered a limitation of the present disclosure. 
         [0010]    Preferably, the amount of vibration and the angle of inclination of the shale shaker table are adjustable to accommodate various drilling mud flow rates and particulate percentages in the drilling mud. After the fluid passes through the perforated bottom of the shale shaker, it may either return to service in the borehole immediately, be stored for measurement and evaluation, or pass through an additional piece of equipment (e.g., a drying shaker, a centrifuge, or a smaller sized shale shaker) to remove smaller cuttings and/or particulate matter. 
         [0011]    Because shale shakers are typically in continuous use, repair operations, and associated downtimes, need to be minimized as much as possible. Often, the filter screens of shale shakers, through which the solids are separated from the drilling mud, wear out over time and subsequently require replacement. Therefore, shale shaker filter screens are typically constructed to be quickly removable and easily replaceable. Generally, through the loosening of several bolts, the filter screen may be lifted out of the shaker assembly and replaced within a matter of minutes. While there are numerous styles and sizes of filter screens, they generally follow similar design. 
         [0012]    Typically, filter screens include a perforated plate base upon which a wire mesh, and/or other perforated filter overlay, is positioned. The perforated plate base generally provides structural support and allows the passage of fluids therethrough. While many perforated plate bases are flat or slightly arched, it should be understood that perforated plate bases having a plurality of corrugated or pyramid-shaped channels extending thereacross may be used instead. Pyramid-shaped channels may provide additional surface area for the fluid-solid separation process while guiding solids along their length toward the end of the shale shaker from where they are disposed. 
         [0013]    In some shale shakers, a fine screen cloth is used with the vibrating screen. The screen may have two or more overlying layers of screen cloth and/or mesh. Layers of cloth or mesh may be bonded together and placed over a support, supports, or a perforated or apertured plate. The frame of the vibrating screen is resiliently suspended or mounted upon a support and is caused to vibrate by a vibrating mechanism (e.g., an unbalanced weight on a rotating shaft connected to the frame). Each screen may be vibrated by vibratory equipment to create a flow of trapped solids on top surfaces of the screen for removal and disposal of solids. The fineness or coarseness of the mesh of a screen may vary depending upon mud flow rate and the size of the solids to be removed. 
         [0014]      FIG. 1  shows a conventional shaker apparatus that includes a lower frame  12  and an upper basket  14 . The shaker apparatus  10  may have a variety of shapes and configurations, but generally it is intended to receive solids-laden mud from a distribution box (not shown) into the basket  14  that is vibrated by a motor (not shown) relative to the frame  12 . The basket  14  includes an upstream end  18 , a downstream end  20 , a back wall  22  at the upstream end  18 , and two side walls  24 . The downstream end  20  is open. In operation, drilling mud including suspended solids is poured into the basket  14  over the back wall  22  and onto screen  16 . Once on the screen  16 , the solids-laden mud is vibrated toward the downstream end  20 , which causes the mud to pass through the screen  16  into a collection box (not shown), and out of the shaker apparatus  10  for further processing. The flow of the solids-laden mud is indicated at  25  in  FIG. 1 . The solids continue to be conveyed downstream on the screen  16  toward the open end  26  where they are either dropped onto another screen for further separation or discarded. 
         [0015]    Screen  16  may be mounted in the basket  14  with wedges  30   a  that are hammered into place under wedge angles  32  that are welded to the inside of basket  14  at an angle corresponding to the angle of the wedge  30   a . In this manner, the screens  16  were installed by placing a pre-tensioned screen  16  onto support rails (not shown) in basket  14 . Once in place, a wedge  30   a  is placed on top of the pre-tensioned screen  16  under wedge angle  32  and then hammered into engagement with the wedge angle  32  to apply a downward force on the screen  16 . Accordingly, contact between the screen  16  and the support rail (not shown) in basket  14  may be maintained. 
         [0016]    Typically, wedges are formed by, for example, casting or compression molding. As known in the art, casting is a process by which a material is introduced into a mold while it is liquid, allowed to solidify in the shape of the mold, and then removed producing a fabricated part. Compression molding is a method in which molding material that is generally preheated is first placed in an open, heated mold cavity. The mold is closed with a top force or plug member, pressure is applied to force the material into contact with all mold areas, and heat and pressure are maintained until the molding material has cured. However, both of these manufacturing methods tend to be expensive. 
         [0017]    Accordingly, there exists a need for a wedge for a shaker screen that is economically efficient in manufacturing and structurally robust to withstand the forces generated during installation. 
       SUMMARY OF INVENTION 
       [0018]    In one aspect, embodiments disclosed herein relate to a wedging apparatus including an outer polygonal surface configured to secure a screen to a shaker, the outer polygonal surface having a bottom surface, a top surface opposite the bottom surface, and at least one end surface joining the top surface and the bottom surface, and an inner core defined by the outer polygonal surface, wherein the inner core defines a cavity. 
         [0019]    In another aspect, embodiments disclosed herein relate a method of forming an apparatus for securing a screen to a shaker, the method including forming a mold of a wedging apparatus configured to secure a screen to a shaker, wherein a shape of the mold is an inverse of an outer polygonal surface having a bottom surface, a top surface opposite the bottom surface, and at least one end surface joining the top surface and the bottom surface, and an inner core defined by the outer polygonal surface, wherein the inner core defines a cavity, injecting a liquid resin into the mold, allowing the liquid resin to solidify, and removing the wedging apparatus from the mold. 
         [0020]    Other aspects and advantages of the invention will be apparent from the following description and the appended claims. 
     
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0021]      FIG. 1  is a perspective view of a conventional shaker screen system. 
           [0022]      FIG. 2  is a side view of a shaker screen and wedging apparatus assembly in accordance with embodiments disclosed herein. 
           [0023]      FIGS. 3A and 3B  are perspective views of wedging apparatuses in accordance with embodiments disclosed herein. 
           [0024]      FIG. 4A  is a cross-sectional view of a wedging apparatus in accordance with embodiments disclosed herein.  FIG. 4B  is a perspective view of  FIG. 4A  in accordance with embodiments disclosed herein. 
           [0025]      FIGS. 5A and 5B  are cross-sectional views of wedging apparatuses in accordance with embodiments disclosed herein. 
           [0026]      FIGS. 6A and 6B  are cross-sectional views of wedging apparatuses in accordance with embodiments disclosed herein. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]    In one aspect, embodiments disclosed herein relate to shale shakers. More specifically, embodiments disclosed herein relate to wedging apparatuses for securing screens to a shale shaker. In another aspect, embodiments disclosed herein relate to methods of forming a wedging apparatus. 
         [0028]      FIG. 2  shows an end view of a shaker screen assembly in accordance with embodiments disclosed herein. In this embodiment, a wall  50  of a shaker basket is illustrated including a wedge bracket  52 . A wedging apparatus  54  may be disposed between wedge bracket  52  and a shaker screen  56 . Wedging apparatus  54  may include any generally polygonal shaped structure capable of applying compressive force on shaker screen  56  and a shaker basket perimeter or support rail  58 . A sealing element  60  may be disposed between shaker screen  56  and support rail  58  to, for example, reduce leakage of drilling fluid and/or particulate matter therethrough. 
         [0029]      FIG. 3A  shows a wedging apparatus  300  in accordance with embodiments disclosed herein. As shown, wedging apparatus  300  includes an outer polygonal surface  302  that includes a top surface  304 , a bottom surface  306 , and two end surfaces  308  joining top surface  304  and bottom surface  306 . One of ordinary skill in the art will appreciate that wedging apparatus  300  may be any shape known in the art such that the wedging apparatus may wedge between two shaker components, thereby securing a screen. Referring briefly to  FIG. 3B , in alternate embodiments, wedging apparatus  300   b  may include only one end surface  308 , thereby forming a wedging apparatus  300   b  of a substantially triangular shape. 
         [0030]    Referring now to  FIG. 4A , a cross sectional view of a wedging apparatus  400  in accordance with embodiments disclosed herein is shown. Similar to wedging apparatus  300  in  FIG. 3A , wedging apparatus  400  includes an outer polygonal surface  402  that includes a top surface  404 , a bottom surface  406 , and two end surfaces  408  that join top surface  404  and bottom surface  406 . 
         [0031]    Top surface  404  may be configured to slidably engage a wedge bracket (not shown) attached to an inside wall of a shaker basket (not shown). One of ordinary skill in the art will appreciate that the wedge bracket may be attached to the shaker basket at any angle to correspond with an angle of top surface  404 . Accordingly, top surface  404  may be formed at any angle α with respect to horizontal axis A, as known in the art. For example, in one embodiment, the angle α of top surface  404  may be 0 degrees, 5 degrees, 30 degrees, 45 degrees, or any angle as known to one of ordinary skill in the art. In an alternate embodiment, top surface  404  may be formed at an angle of 0 degrees while bottom surface  406  may be formed at any angle with respect to a horizontal axis. 
         [0032]    As shown, outer polygonal surface  402  defines an inner core  410 . In one embodiment, as shown in  FIG. 4B , inner core  410  may extend from a first side  414  though wedging apparatus  400  to a second side  416 , thereby forming a cored wedging apparatus  400 . Alternatively, first side  414  and second side  416  may substantially enclose inner core  410 , thereby forming a hollow wedging apparatus (not independently illustrated). Accordingly,  FIG. 4A  may represent a cross-sectional view of a hollow and substantially enclosed wedging apparatus  400 . Thus, inner core  410  defines a cavity (not independently illustrated). In some embodiments, the cavity may be filled, partially filled, traversed by ribs, or enclosed as described in greater detail below. In at least one embodiment, the cavity may be bisected to form two or more cavities. 
         [0033]    Still referring to  FIGS. 4A and 413 , outer polygonal surface  402  may be formed from any material known in the art. For example, outer polygonal surface  402  may be formed from a plastic, such as polyurethane, polypropolene, or nylon. In an alternate embodiment, the polygonal surface  402  may be formed from a composite material, such as glass-filled polypropolene. With reference to the embodiments shown in  FIGS. 4A and 4B , inner core  410  may be filled with any material known in the art. For example, inner core  410  may be filled with a material that provides structural rigidity to wedging apparatus  400 . Alternatively, in one embodiment, inner core  410  may be filled with a plastic, such as, polyurethane, polypropolene, or nylon. In yet other embodiments, inner core  410  may be filled with a foam or gas. 
         [0034]      FIG. 5A  shows a cross sectional view of a wedging apparatus  500  in accordance with embodiments disclosed herein. Wedging apparatus  500  includes an outer polygonal surface  502 , including a top surface  504 , a bottom surface  506 , and two end surfaces  508  that join top surface  504  and bottom surface  506 , thereby defining an inner core  510 . A plurality of ribs  512  may be disposed within core  510  and may extend, for example, from top surface  504 , bottom surface  506 , or at least one end surface  508  to the bottom surface  506 , at least one end surface  508 , or top surface  504 . Accordingly, in one embodiment, the plurality of ribs  512  may form a plurality of truss-like structures. Alternatively, in another embodiment, as shown in  FIG. 5B , a plurality of ribs  512   b  may also extend between a first rib and a second rib or between a first rib and top surface  504 , bottom surface  506 , or end surface  508 . In one embodiment, wedging apparatus  500  may include a first side (not shown) and/or a second side (not shown), wherein the first side joins a first edge of top surface  504  and a first edge of bottom surface  506 , and the second side joins a second edge of top surface  504  and a second edge of bottom surface  506 . Accordingly, first and second sides may enclose inner core  510 . 
         [0035]    In the embodiments shown in  FIGS. 5A and 5B , plurality of ribs  512 ,  512   b  may be formed from any material known in the art. For example, plurality of ribs  512 ,  512   b  may be formed from a plastic, such as polyurethane, polypropolene, or nylon. In an alternate embodiment, plurality of ribs  512 ,  512   b  may be formed from a composite material, such as glass-filled polypropolene. Inner core  510  may be filled in and around the plurality of ribs  512 ,  512   b  with any material known in the art. In one embodiment, inner core  510  may be filled with a material that provides additional structural rigidity to the plurality of ribs  512 ,  512   b  and wedging apparatus  500 . For example, in one embodiment, inner core  510  may be filled with a foam or a gas. 
         [0036]    In another embodiment, as shown in  FIGS. 6A and 6B , a wedging apparatus  600  may include an outer polygonal surface  602  having a top surface  604 , a bottom surface  606 , two end surfaces  608  that join top surface  604  and bottom surface  606 , a first side  614 , and a second side  616 . Outer polygonal surface  602  defines an inner core  610  enclosed within top and bottom surfaces  604 ,  606 , end surfaces  608 , and first and second sides  614 ,  616 . A plurality of ribs  612 ,  612   b  may be formed in first and/or second sides  614 ,  616 . The plurality of ribs  612  may extend from top surface  604 , bottom surface  606 , or at least one end surface  608  and extend to the bottom surface  606 , at least one end surface  608 , or top surface  604 . In another embodiment, the plurality of ribs  612   b  may also extend between a first rib and a second rib or between a first rib and top surface  604 , bottom surface  606 , or end surface  608 . 
         [0037]    In one embodiment, the plurality of ribs  612 ,  612   b  may extend a selected distance z from first side  614  into inner core  610  of wedging apparatus  600 . For example, the plurality of ribs  612 ,  612   b  may extend half the width w of wedging apparatus  600 . Alternatively, the plurality of ribs  612 ,  612   b  may extend along the entire width w of wedging apparatus  600 , that is, ribs  612 ,  612   b  extend from first side  614  through wedging apparatus  600  to second side  616 . In such an embodiment, distance z would be substantially the same a width w. One of ordinary skill in the art will appreciate that the ribs  612 ,  612   b  may extend any distance into wedging apparatus  600  such that the structural integrity of the wedging apparatus  600  is substantially maintained. In one embodiment, second side  616  may substantially enclose the wedging apparatus  600 , while first side  614  includes a plurality of ribs  612 ,  612   b , as described above. Cavities formed between each rib may be filled with any material known in the art, for example, a foam or gas. When placed in a shaker, the first side  614  of wedging apparatus  600  may be positioned proximate a wall of the basket and the enclosed second side  616  of wedging apparatus  600  may be positioned to face the inside of the basket. Thus, mud flowing over the shaker screen may not come into contact with first side  614 , and therefore, inner core  610 . Because drilling fluid or mud will not contact the material in the inner core  610 , materials used to fill the cavities between the ribs of first side  614  may include materials with a lower chemical resistance. 
         [0038]    In still other embodiments, a plurality of ribs  612 ,  612   b  may be formed on both the first and second sides  614 ,  616  of wedging apparatus  600  and extend back a selected distance z (as shown, z denotes the selected distance from first side  614 , a selected distance is not independently illustrated for second side  616 ) into inner core  610 , such that the plurality of ribs  612 ,  612   b  extending back from first side  614  do not contact the plurality of ribs  612 ,  612   b  extending back from second side  616 . In one embodiment inner core  610  may include an additional cavity (not shown) formed between the two sets of ribs  612 ,  612   b  extending back from the first and second sides  614 ,  616 . The cavity may be filled with any material known in the art, for example, a foam or gas. Alternatively, inner core  610  may be formed from a plastic as described below. 
         [0039]    In the embodiments shown in  FIGS. 6A and 6B , outer polygonal surface  602 , including both first and second sides  614 ,  616 , may be formed from any material known in the art. For example, outer polygonal surface  602  may be formed from a plastic, such as polyurethane, polypropolene, or nylon. In an alternate embodiment, the polygonal surface  602  may be formed from a composite material, such as glass-filled polypropolene. In one embodiment, inner core  610  may be integrally formed with outer polygonal surface  602 . Accordingly inner core  610  may be formed from a plastic, such as polyurethane, polypropolene, or nylon, or a composite material, as described above. In an alternate embodiment, enclosed inner core  610  may be filled with a foam or gas. 
         [0040]    In accordance with embodiments described above, a wedging apparatus may be formed by injection molding. In such an embodiment, a molten plastic is injected at a high pressure into a mold having an inverse shape of a desired wedging apparatus. The shape of the wedging apparatus may be, for example, any shape as detailed above and/or shown in  FIGS. 3-6 . The mold may be formed by a toolmaker or moldmaker from metal, typically either steel or aluminum, and precision-machined to form smaller, more detailed features. Once the mold is filled with molten plastic, the molten plastic is allowed to cure and is then removed from the mold. As detailed above, the mold may be filled with any molten plastic known in the art, for example, polyurethane, polypropolene, or nylon. In alternate embodiments, the mold may be filled with a molten composite material, such as glass-filled polypropolene. One of ordinary skill in the art will appreciate that other materials may be used without departing from the scope of embodiments disclosed herein. 
         [0041]    Alternatively, a wedging apparatus in accordance with embodiments described above may be formed by gas-assist injection molding. In this embodiment, molten plastic is injected into a mold, partially filling it with a predetermined amount of resin or molten plastic. A gas, for example, nitrogen, is introduced into the mold cavity. The gas forms hollow channels as it follows a path of least resistance, thereby directing the molten plastic to fill all areas of the mold. As the gas expands in the cavity, forcing the molten plastic outward, all of the surfaces receive substantially equal pressure. The molten plastic is allowed to cure, the gas may be vented through a nozzle or vent, and the wedging apparatus may be removed from the mold. 
         [0042]      FIGS. 6A and 6B  show an example of a wedging apparatus  600  in accordance with the embodiments disclosed herein that may be formed by injection molding. In such an embodiment, molten plastic may be injected at pressure into the mold, wherein the molten plastic is allowed to cure, and the solid plastic wedging apparatus  600  is removed from the mold. The wedging apparatus  600 , once removed, may be substantially solid with a plurality of ribs  612 ,  612   b  formed on the first and/or second sides  614 ,  616  of the wedging apparatus  600 . 
         [0043]    One of ordinary skill in the art will appreciate that any material known in the art may be used for both injection molding and gas-assist injection molding wedging apparatuses. In one embodiment, an outer polygonal surface of a wedging apparatus may be formed of any material with a low compression set and high impact performance. For example, an outer polygonal surface of a wedging apparatus may be formed of a plastic, such as polyurethane, polypropolene, or nylon, or a composite material, such as a glass-filled polypropolene. Further, an inner core of a wedging apparatus, defined by an outer polygonal surface, may be formed of or filled with any material known in the art. For example, an inner core of a wedging apparatus may be filled with a plastic, such as polyurethane, polypropolene, or nylon, or a composite material, such as a glass-filled polypropolene. Alternatively, an inner core of a wedging apparatus may be filled with a foam or gas. In embodiments where an inner core of a wedging apparatus is substantially enclosed, and therefore not in contact with drilling fluid flowing over a shaker screen, the inner core may be formed from or filled with a material of lower chemical resistance. 
         [0044]    Advantageously, wedging apparatuses formed in accordance with embodiments disclosed herein may provide shortened cooling cycles, reduced surface warps, and increased structural stability. Advantageously, wedging apparatuses formed in accordance with embodiments disclosed herein may also be more cost efficient to manufacture. Moreover, wedging apparatuses formed in accordance with embodiments disclosed herein may be formed of more cost efficient materials, thereby providing more cost effective methods of forming wedging apparatuses. 
         [0045]    Conventional wedges are often formed by open casting or compression molding. Injection molding a conventional wedge, having a basic wedge block structure, may result in warped edges due to the relative thickness of the wedge. Because the wedge is conventionally a solid piece of plastic, the molten plastic towards the middle of the wedge would cool much more slowly than the plastic towards the outer perimeter of the wedge, thereby causing the outer edges of the wedge to warp and deform out of shape. Advantageously, embodiments disclosed herein describe a wedging apparatus and a method of forming a wedging apparatus that may reduce the expenses of manufacturing and reduce the warp of the wedging apparatus during manufacturing, while maintaining the structural integrity of the wedging apparatus. 
         [0046]    While the present disclosure has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments may be devised which do not depart from the scope of the present disclosure. Accordingly, the scope of the present disclosure should be limited only by the attached claims.