Abstract:
An apparatus and method of manufacturing a wellscreen for subterranean use in oil, gas, and water wells, incorporating numerous automated processes, whereby layers of mesh are continuously sintered to a perforated strip, formed into a tube, placed over a perforated base pipe, and sealed with end rings.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention generally relates to an apparatus and method of manufacturing a wellscreen for subterranean use in oil, gas, and water wells.  
           [0003]    2. Description of the Related Art  
           [0004]    The problem of reliably removing particulates from liquids or gasses (production fluids) exists in many types of wells including oil and gas wells, water wells, geothermal wells, and wells for ground remediation. Typical particulates needing to be filtered out are sand and clay including unconsolidated particulate matter, also known as “formation sand”. A major problem in producing hydrocarbon fluids from unconsolidated formations is the intrusion of formation sand, which is typically very fine, into production fluid and equipment. The presence of sand in production fluid often leads to the rapid erosion of expensive well machinery and hardware.  
           [0005]    Subterranean filters, also known as “sand screens” or “wellscreens”, have been used in the petroleum industry for years to remove particulates from production fluids. They are generally tubular in shape, comprising a perforated inner member or pipe, at least one porous filter layer wrapped around and secured to the pipe, and an outer cover. The wellscreens are used where fluid enters a production string. For example, a common way to achieve the filtration is to mount a wellscreen in the production string near the area of fluid production such that the produced fluid must pass through the filter layers and into the perforated pipe prior to entering the production string and being pumped to the surface.  
           [0006]    A typical method of constructing a wellscreen involves wrapping and seamwelding mesh layers of filtering material around a perforated base pipe. An alternative method involves forming a tube of the mesh material, seam welding it longitudinally and then sliding it over the perforated base pipe. The mesh layers typically consist of sintered mesh filter elements and more coarse wire mesh drainage elements. A protective outer shroud consisting of a perforated tube is then placed over the mesh layers and the perforated base pipe and end rings are then welded in place to seal the ends of the filter elements and protective shroud to the base pipe.  
           [0007]    There are problems associated with the forgoing wellscreens and their construction. For example, a conventional vacuum furnace used to manufacture the sintered mesh material needed for the filter elements restricts the maximum size of the mesh material, typically to two feet by four feet. This requires multiple sections of the sintered mesh material be welded together to produce filter elements greater than four feet in length. In a wellbore, wellscreen must typically extend as much as one hundred feet to fully access the surrounding formations. This results in many individual sections of sintered mesh material being welded together to form elements of the required lengths. Each layer of mesh must also be individually cut, wrapped around the base pipe, and then seam-welded. These numerous steps result in a labor-intensive process that is both expensive and requires significant manufacturing time.  
           [0008]    In addition, the burst strength, or the ability of the wellscreen to withstand radially applied pressure, is limited to the weakest layer. This is important because hydrocarbons and sand from a surrounding formation may enter the wellbore and hit the wellscreen at high velocity. This problem exists in prior art wellscreens because each layer of mesh is individually assembled and there is a tendency for the layers to be extruded through the holes in the base pipe as radial pressure is applied from the outer diameter of the wellscreen. A similar problem exists with the layers being extruded through holes in the outer shroud as radial pressure is applied from the inner diameter of the wellscreen.  
           [0009]    Therefore, a need exists for a wellscreen that is less expensive and requires less time to manufacture than conventional wellscreens.  
           [0010]    There is a further need for a wellscreen that is more robust and exhibits higher burst pressure than conventional wellscreens.  
           [0011]    There is yet a further need for a wellscreen that can be manufactured in a variety of lengths.  
         SUMMARY OF THE INVENTION  
         [0012]    The present invention generally relates to an apparatus and method of manufacturing a wellscreen for subterranean use in oil, gas, and water wells. The present invention provides a method of manufacturing a wellscreen whereby layers of porous material are continuously sintered to a perforated metal strip to form a laminate, and the laminate is shaped to form a tube. The tube is then disposed over a base pipe and the ends of the tube are sealed to the base pipe.  
           [0013]    In addition, the invention relates to a wellscreen comprised of a laminate shaped to form a tube, whereby the laminate includes a plurality of layers of continuously sintered porous material.  
           [0014]    In one aspect of the invention, the laminate is either spiral welded or longitudinally welded into a straight tube.  
           [0015]    In another aspect of the invention, the laminate is either spiral welded or longitudinally welded into coiled tubing. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    So that the manner in which the above recited features, advantages and objects of the present invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings.  
         [0017]    It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.  
         [0018]    [0018]FIG. 1 is a sectional view showing a wellscreen in an uncased, horizontal wellbore.  
         [0019]    [0019]FIG. 2 is an exploded view illustrating individual layers of material used to construct the wellscreen.  
         [0020]    [0020]FIG. 3 is a sectional view of the wellscreen within a wellbore, showing the various layers of the screen, including the base pipe, filter and drainage mesh, and the outer shroud.  
         [0021]    [0021]FIG. 4 is a sectional end view of a wellscreen, showing the various layers of the screen, including the base pipe, filter and drainage mesh, and the outer shroud.  
         [0022]    [0022]FIG. 5 is an exploded view of an exemplary expansion tool.  
         [0023]    [0023]FIG. 6 is a sectional view of an expanded wellscreen within a wellbore, showing the various layers of the screen, including the base pipe, filter and drainage mesh, and the outer shroud. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0024]    [0024]FIG. 1 is a sectional view showing a wellscreen  10  in an uncased, horizontal wellbore  11 . The horizontal wellbore  11  is typically formed at the lower end of vertical wellbore  32  that is lined with casing  33 . An annular area between the wellbore  32  and the casing  33  is filled with cement. Extending into the wellbore  32  from the surface of the well is a string of production tubulars  14  connected with joints  16 . A packer  40  seals the annular area between the casing  33  and the string of production tubulars  14 . The horizontal wellbore  11  is unlined to facilitate the flow of hydrocarbons into the wellbore. Disposed on the production string of tubulars  14  in the horizontal wellbore  11  are wellscreens  10  according to the present invention. Multiple wellscreens  10  are illustrated and are connected together end to end with joints  16 . A hydrocarbon-bearing formation  12  adjacent the horizontal wellbore is illustrated.  
         [0025]    The wellscreen of the present invention is constructed of multiple layers of similar and dissimilar materials. FIG. 2 is an exploded view showing the various layers of the wellscreen that are sintered together as part of the manufacturing process to form the wellscreen. The sintering process involves increasing the temperature of the various components to approximately eighty percent of the melting temperature and fusing the components together. The layers consist of: drainage mesh  17 , filter mesh  18 , drainage mesh  19 , filter mesh  20 , drainage mesh  21 , and protective shroud  22 . The alternating nature of the filter  18  and  20  and drainage  17 ,  19 , and  21  meshes ensures filtering without restricting the flow of fluids into and along the surface of the wellscreen.  
         [0026]    In addition, the sintering of the mesh layers  17 - 21  to the perforated plate used to construct the outer protective shroud  22  increases the burst pressure of the wellscreen by creating a single unit of laminated layers. The laminate created by the mesh layers and the perforated plate is much stronger than the individual layers of mesh, which, in prior art wellscreens, remain independent from one another after the manufacturing process.  
         [0027]    Also, the use of the continuous sintering process does not restrict the length of the elements used in the construction of the wellscreen.  
         [0028]    [0028]FIG. 3 is a sectional view of a portion of the wellscreen  10 , after construction of the wellscreen  10  has been completed by shaping the sintered layers  17 - 22  into a tube, sliding the layers over a perforated base pipe  24 , and welding on an end ring  25 . The layers consist of: drainage mesh  17 , filter mesh  18 , drainage mesh  19 , filter mesh  20 , drainage mesh  21 , and protective shroud  22 . The opposite end (not shown) of the sintered layers  17 - 22  is identical to the end shown in FIG. 3. Typically, one end of the wellscreen  10  would consist of the male portion of a threaded coupling (not shown), while the other end of the wellscreen  10  would consist of the female portion of a threaded coupling (not shown). This allows a wellscreen  10  to be connected to a production string or additional wellscreens as needed.  
         [0029]    As shown in FIG. 3, the outer perforated member  22  provides a protective layer for the internal components, namely filter mesh  18  and  20  and drainage mesh  17 ,  19 , and  21 . The outer member  22  should be constructed with a sufficient wall thickness to withstand the down hole radial pressures in the well, including pressure created by collapsing walls of the wellbore. A plurality of perforations  28  is formed in the outer member  22 . The diameter and number of perforations  28  may be approximately the same as perforations  30  in inner member  24 . The mesh layers  17 - 21  may be attached to inner member  24  using welded end ring  25 , and sealed with weld metal  30  and  31 .  
         [0030]    [0030]FIG. 4 is a sectional end view of a wellscreen  10  within a wellbore  11 . FIG. 4 includes the layers of filter mesh  18  and  20  and drainage mesh  17 ,  19 , and  21  as well as protective shroud  22 . These components have been sealed with weld metal  29 , and disposed over a perforated base pipe  24 . An annular area  34  exists between the wellscreen  10  and the wellbore  11 .  
         [0031]    As shown in FIGS. 1 and 4, the filter mesh  18  and  20  is a fine mesh material used to remove small particulates from the production fluid  12 . In this manner, the production fluid  12  is filtered before it enters the production string  14  to prevent erosion of well machinery and hardware, and to prevent the production of particulate matter. The drainage mesh  17 ,  19  and  21  is a more coarse mesh material which serves as a spacer material between the filter mesh  18  and  20  and either the base pipe  24 , outer protective shroud  22 , or additional filter material  18  and  20 . The drainage mesh  17 ,  19 , and  21  reduces the pressure drop of the production fluid  12  as it passes through the wellscreen by allowing the production fluid  12  to pass through the entire surface area of the filter mesh  18  and  20 . The drainage mesh  17 ,  19  and  21  also assists in conducting particulate through the filter mesh  18  and  20  that may otherwise clog the filter mesh  18  and  20  over time.  
         [0032]    In one embodiment of the present invention, the outer member  22  is either 304 SS or 316 SS material. The drainage mesh  18  and  20  in one embodiment is 10×10 mesh of 316 SS material, and the filter mesh  17 ,  19 , and  21  is comprised of 24×10 mesh of 316 SS material. The outside diameter of the tube formed by the laminate in one embodiment is about 2.5 to 7 inches in diameter, and the length of the tube is about 10 to 40 feet.  
         [0033]    In a method of manufacturing the wellscreen, a significant number of steps are automated, thereby reducing manufacturing costs and time. For example, the plate that is used as the outer protective shroud is perforated in an automated process while it is still flat, prior to forming the tubular shape. Using this method, the edge of each piece of steel must be left intact to allow for a continuous seam when the tube is formed. The desired number of drainage and filter mesh elements are then placed on the flat perforated plate and sintered together in another automated process. The equipment used to sinter the pieces together utilizes a continuous sintering process and is capable of accommodating pieces of various lengths.  
         [0034]    In addition to the processes described, the tube can be formed by shaping the laminate into a tubular shape and then utilizing either a straight or a spiral weld to seal the seams that are created when the flat plate is formed into the tube. Both the shaping and welding of the laminate may be accomplished in an automated process. This leaves only the final assembly, consisting of sliding the tube over a perforated base pipe and sealing the ends of the tube to the base pipe, as non-automated processes. Typically, the ends of the tube will be sealed to the base pipe by welding end rings to both the ends of the tube and the base pipe.  
         [0035]    In an alternative embodiment, the base pipe of the wellscreen may be a section of perforated coiled tubing. In this embodiment, a laminate comprised of the layers in FIG. 2 are formed into a tubular shape, as previously described. The desired length of the tubular laminate is disposed over an equal length of perforated coiled tubing and is then sealed to the tubing by welding on end rings. The wellscreen with a perforated coiled tubing base pipe may be connected to standard, non-perforated coiled tubing used as production tubing. In this embodiment, a length of coiled tubing wellscreen can be manufactured and then added to the end of a length of standard coiled tubing. The entire length of standard and coiled tubing wellscreen can then be placed in a single reel and transported to a well site and inserted into a well. This embodiment could be used when the desired length of wellscreen was known before transporting the wellscreen to the production site. In this embodiment, the wellscreen and production tubing are both included on one spool of coiled tubing.  
         [0036]    Alternatively, the standard coiled tubing and the coiled tubing wellscreen can be housed in separate spools. Utilizing tubing connectors, the coiled tubing wellscreen can be connected to standard coiled tubing used as production tubing. This method of use is especially useful when the desired length of wellscreen is not known prior to transporting spools of coiled tubing to a well site.  
         [0037]    In an alternative embodiment of the invention, the wellscreen may be run into a horizontal wellbore and then its inner and outer diameter may be expanded through the use of an expander tool. FIG. 5 is an exploded view of an exemplary expansion tool  100 . The expansion tool  100  has a body  102  which is hollow and generally tubular with connectors  104  and  106  for connection to other components (not shown) of a downhole assembly. The connectors  104  and  106  are of a reduced diameter compared to the outside diameter of the longitudinally central body part of the tool  100 . The central body part has three recesses  114  to hold a respective roller  116 . Each of the recesses  114  has parallel sides and extends radially from a radially perforated tubular core (not shown) of the tool  100 . Each of the mutually identical rollers  116  is somewhat cylindrical and barreled. Each of the rollers  116  is mounted by means of an axle  118  at each end of the respective roller and the axles are mounted in slidable pistons  120 . The rollers are arranged for rotation about a respective rotational axis that is parallel to the longitudinal axis of the tool  100  and radially offset therefrom at 120-degree mutual circumferential separations around the central body  102 . The axles  118  are formed as integral end members of the rollers and the pistons  120  are radially slidable, one piston  120  being slidably sealed within each radially extended recess  114 . The inner end of each piston  120  is exposed to the pressure of fluid within the hollow core of the tool  100  by way of the radial perforations in the tubular core. In this manner, pressurized fluid provided from the surface of the well, via a tubular, can actuate the pistons  120  and cause them to extend outward whereby the rollers  116  contact the inner wall of a tubular to be expanded.  
         [0038]    In use the expander tool is run into the well on a separate string of tubulars or is run into the well disposed in the interior of the wellscreen and attached thereto with some temporary mechanical connection. In order to utilize the expander tool, the rollers are extended outwards radially to contact the inner walls of the wellscreen. By moving the actuated tool  100  within the wellscreen, both rotationally and axially, the screen is expanded to take on an appearance illustrated in FIG. 6, which is a cross section view of the expanded wellscreen  10  within the wellbore  11 . FIG. 6 includes the layers of filter mesh  18  and  20  and drainage mesh  17 ,  19 , and  21  as well as protective shroud  22 . These components have been sealed with weld metal  29 , and disposed over a perforated base pipe  24 . By expanding the diameter of the wellscreen  10  until it contacts the wellbore  11 , the annular area  34  is significantly reduced or eliminated. The wellscreen  10  is then able to provide support to the surface of the wellbore  11  and reduce the amount of sediment and debris that breaks free from the wellbore  11  and restricts the flow of production fluid through the wellscreen  10 . If necessary, the wellscreen  10  may be annealed before being inserted into the wellbore  11  for improved ductility during the expansion process.  
         [0039]    The present invention displays significant advantages over previous manufacturing methods. The advantages include the reduced time and cost of manufacturing. For example, many of the wellscreen manufacturing steps can be automated. The perforation of the outer protective shroud, the sintering of the mesh material, and the forming of the tubes are all automated processes. The only labor needed is sliding the tube (consisting of the outer protective shroud and mesh material) over the base pipe and welding on end rings.  
         [0040]    Another advantage of the present invention is the increased burst pressure of the wellscreen. This is due to the strength of the laminate and its resistance to extruding through perforations in the base pipe or outer shroud.  
         [0041]    Still a further advantage of the present invention is the ability to manufacture wellscreens in lengths greater than previous methods allowed.  
         [0042]    While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow. For example, the number of either filter or drainage layers may be altered, depending on each application. In addition, material other than the mesh described may be used for either filter or drainage layers.