Patent Application
20080078703
In one aspect, embodiments disclosed herein relate to pre-tensioned composite screens for an oilfield shaker. More specifically, embodiments disclosure herein relate to pre-tensioned composite screens including removable screen assemblies. More specifically still, embodiments disclosed herein relate to pre-tensioned composite shaker screens and methods of manufacturing and rebuilding such screens.
Generally, embodiments disclosed herein include a composite frame) at least one removable grid attached to the composite frame, and at least one filtering element attached to the at least one removable grid. In at least one embodiment, such screens provide a shaker operator the ability to remove the grid from the composite frame and attach a new grid to the original composite frame.
Referring to
While the embodiment shown in
Referring to
Composite frame 402 may be formed from any material and by any method known in the art. In one embodiment, composite frame 402 may be formed from a frame sub-structure including high-strength steel beams, having a hollow cross-section, and high strength steel rods. The frame sub-structure may be enclosed in a high-strength, glass reinforced plastic outer frame, wherein the frame sub-substructure forms part of both cross-members 408 and/or transverse ribs (not shown). The composite material may include high-strength plastic, mixtures of high-strength plastic and glass, high-strength plastic reinforced with high-tensile-strength steel rods, and any combination thereof. One of ordinary skill in the art will appreciate that the frame sub-structure and the outer frame may be formed in any configuration and from any material or combination or materials known in the art. Alternatively, composite frame 402 may be formed through injection molding, gas-assisted injection molding, extrusion, and/or any other process known in the art.
Referring now to
Removable grid 502 may be formed by, among other processes, injection molding, gas injection molding, and/or extrusion. In embodiments using injection molding, a molten material is injected at a high pressure into a mold having an inverse shape of a desired grid. The configuration of the grid may be, for example, any configuration described above, and/or shown in
Alternatively, a removable grid 502 in accordance with embodiments described herein may be formed by gas-assist injection molding. In this embodiment, molten material is injected into a mold, partially filling it with a predetermined amount of resin or molten material. A gas (e.g., nitrogen) is introduced into the mold cavity. The gas forms hollow channels as it follows a path of least resistance, thereby directing the molten material to fill all areas of the mold. As the gas expands in the cavity, forcing the molten material outward, all of the surfaces receive substantially equal pressure. Subsequently, the molten material is allowed to cure, the gas may be vented through a nozzle or vent, and the grid may be removed from the mold. In other embodiments, removable grid 502 may be formed by any of the processes of forming a frame discussed above such as, for example, sub-structure framing.
Filtering element 501 may include, for example, a mesh, a fine screen cloth, combinations thereof, and/or any other materials known to one of ordinary skill in the art. Furthermore, filtering elements 501 may be formed from, for example, plastics, metals, alloys, fiberglass, composites and/or polytetrafluorethylene. In certain embodiments, multiple layers of filtering elements 501 may be used, and in such multiple layer filtering elements 501, filtering elements 501 with different size perforations may be used. In such embodiments, the filtering element layers should preferably be arranged wherein coarser filtering elements are disposed closer to removable grid 502, while finer layers are disposed on top of the coarser layers.
While attaching filtering element 501 to removable grid 502, in accordance with any of the methods described above, filtering element 501 may be pre-tensioned. In one embodiment, filtering element 501 may be stretched over attachment points 512 so that filtering element 501 is tensioned to a pre-selected level. Filtering element 512 may then be attached to removable grid 502 by, for example, heat staking, ultrasonic welding, mechanical fastening, chemical adhesion, and/or thermal bonding. Alternatively, one of ordinary skill in the art will appreciate that filtering element 501 may be attaching to removable grid 502 in accordance with any method known in the art.
Removable grid 502 may also be coated with polymer, epoxies, of combinations thereof to further enhance the anticorrosion properties of the grid. In certain embodiments, removable grid 502 may be coated in materials such as, powder epoxies and/or polymers, such as polyethylene and/or polypropylene. Those of ordinary skill in the art will appreciate that additional polymers and epoxies not specifically disclosed may also be used to coat removable grid 502. In alternate embodiments, wherein removable grid 502 is formed from a metal, the metal surfaces may also be coated with polymers, epoxies, or combinations thereof.
Referring to
Removable grid 603 may be attached to composite frame 602 according to any attachment method known to one of ordinary skill in the art including, but not limited to, bonding, mechanical fastening, and chemical adhesion. In one embodiment, removable grid 603 may be attached to composite frame 602 using heat staking. Referring briefly to
In alternate methods of heat staking, the contact point may be externally affixed to composite frame 602, rather than being integral to composite frame 602. In embodiments where external attachment points are affixed to composite frame 602, external attachment points may be formed from any material known to one of ordinary skill in the art, including, acrylonitrile butadiene styrene, modified phenylene oxide, and polypropylene. Generally, other appropriate heat staking materials may include thermoplastics, crystalline polymers, and amorphous polymers.
In another embodiment, removable grid 603 may be attached to composite frame 602 using ultrasonic welding. Ultrasonic welding is the conversion of high-frequency electrical energy to high-frequency mechanical energy. The mechanical energy is applied to a plastic material as a vertical vibrating motion under pressure, and heat is generated at the contact point of two materials (e.g., composite frame 602 and removable grid 603) such that the two materials become attached. Contact points for attaching composite frame 602 to removable grid 603 may include portions of composite frame 603 which are integral, or external attachment points attached to composite frame 603 either before or after manufacture.
One of ordinary skill in the art will appreciate that any method of bonding composites to metal and/or composites to composites may be used so as to attach removable grid 603 to composite frame 602. In methods of ultrasonic welding wherein external attachment points are affixed to composite frame 602, external attachment points may be formed from any material known to one of ordinary skill in the art, including, styrene-maleic-anhydride, polycarbonates, acrylonitrile butadiene styrene, and combinations thereof. Generally, other appropriate ultrasonic welding materials may include thermoplastics, crystalline polymers, and amorphous polymers.
In still another embodiment, removable grid 603 may be attached to composite frame 602 using mechanical fastening. Mechanical fasteners may include bolts, rivets, screws, and any other fastening device capable of attaching removable grid 603 to composite frame 602. One mechanical method of attaching removable grid 603 to composite frame 602 may include fasteners attached to removable grid 603 that are configured to engage a fastening structure of composite frame 602. While not independently illustrated, one of ordinary skill in the art will appreciate that any method of mechanically fastening a metal to a composite and/or a composite to another composite may be used so as to attach removable grid 603 to composite frame 602. Preferably, the mechanical fasteners will include corrosion resistant and or coated material, such as plastics and/or composites, to reduce failure of the fasteners. Certain embodiments may include a combination of mechanical fasteners and, for example, heat staking, to attach removable grid 603 to composite frame 602.
Possible methods of detaching removable grid 603 from composite frame 602 may include a mechanical stripping process or removal of the fasteners connecting the two parts. Methods used to detach removable grid 602 from composite frame 603 may vary depending on the method by which removable grid 602 was attached to composite frame 602. When threaded fasteners were used, removable grid 603 and composite frame 602 may be separated by unscrewing the threaded fasteners. Alternatively, if non-threaded fasteners are used, a different method of removal, such as by severing the fasteners, may be appropriate. When removable grid 603 is attached to composite frame 602 by heat staking, they may be separated by severing the stakes, by heating the stakes until they are soft enough that removable grid 603 and composite frame 602 may be separated, or by another method known to one of ordinary skill in the art. Alternative embodiments may use any other methods known to those of ordinary skill in the art, such as for example, chemical stripping, to separate removable grid 603 from composite frame 602.
Certain embodiments in accordance with the present disclosure may have filtering elements that are attached to the removable grid before the removable grid is attached to the composite frame. In these embodiments, the tension in the filtering elements, resulting from their attachment to the removable grid, may prevent the grid and filtering element assembly from lying substantially flat, that is, the grid may be bowed. The attachment of the removable grid to the composite frame may force the grid to conform to the overall shape of the composite frame. Such screen assemblies may be substantially flat after the grid is attached to the composite frame. Other embodiments may include removable grids that are rigid enough to remain substantially flat, even when filtering elements are attached to the removable grid before the removable grid is attached to the composite frame.
Advantageously, embodiments disclosed herein may provide for a more efficient pre-tensioned composite shaker screen design. Embodiments presently disclosed may allow the composite frame to be reused after one or more of the screen assemblies attached to it are worn out. Certain embodiments may also allow a shaker operator to change the screen assembly as is required to adjust the rate of separation of differing drilling fluids from particulate matter.
Also advantageously, embodiments disclosed herein may allow an existing composite frame to be rebuilt with various filtering element configurations for different applications. Thus, entire shaker screens will not need to be discarded; rather, only the removable grid and/or filtering elements will need to be replaced. By decreasing the cost associated with replacing entire shaker screens, the cost of separating drilling fluid from solids may be substantially decreased, thereby decreasing the overall cost of the drilling operation.
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 can be devised which do not depart from the scope of embodiments disclosed herein. Accordingly, the scope of embodiments disclosed herein should be limited only by the attached claims.
| Number | Date | Country | |
|---|---|---|---|
| 60827601 | Sep 2006 | US |
