Patent Publication Number: US-2010122810-A1

Title: Well screens and method of making well screens

Description:
SUMMARY 
     In one example, a screen is provided for use in wells for producing fluids from an underground reservoir. The screen includes first and second sections of mesh tube that encircle a base pipe and that filter reservoir fluids flowing radially into the base pipe. The first section has an end portion that is connected to an end portion of the second section by a lap joint. The lap joint can be welded by a weld in such a way that either the first or second end portions provide a backing for the weld. In a further example, the end portions are swaged towards and away from the base pipe, respectively, and include chamfered edges. 
     In another example, an arrangement for producing fluids from an underground reservoir is provided. An axially elongated base pipe is radially encircled by an inner layer comprising a wire tube. The inner layer and base pipe define an axial flow path. A sand screen comprising a mesh tube encircles the inner layer and a shroud comprising a perforated tube encircles the sand screen. The sand screen has first and second sections that are connected by a lap joint. In a further example, the base pipe is impermeable except for a flow restriction located at a downstream end portion of the axial flow path. The flow restriction has a fixed flow cross section sized to receive reservoir fluids and to permit pressure reduction to thereby control reservoir fluid flow by fluid collision between reservoir fluid that has passed through the flow restriction and fluid downstream of the flow restriction. 
     In another example, a method of making a screen for use in an underground reservoir is provided. First and second sections of sand screen comprising mesh tubes are provided and a portion of the first section is overlapped onto a portion of the second section. The edges of the overlapped portions are welded so that the second section of the sand screen provides a backing during the welding step. In yet another example, the ends of the first and second sections are chamfered and swaged towards and away from the base pipe, respectively. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The best mode of carrying out the invention is described herein with reference to the following drawing figures. 
         FIG. 1  is a sectional view of a prior art inflow control device for controlling reservoir fluid flow into a well. 
         FIG. 2  is a view of Section  2 - 2  taken in  FIG. 1 . 
         FIG. 3  is a sectional view of a prior art arrangement for joining two mesh screen sections. 
         FIG. 4  is a view of Section  4 - 4  taken in  FIG. 3 . 
         FIG. 5  is a sectional view of an arrangement for joining two screen sections end to end. 
         FIG. 6  is a view of Section  6 - 6  taken in  FIG. 5 . 
         FIG. 7  is a sectional view of one example of a screen for incorporation into an inflow control device in accordance with the concepts described in the present application. 
         FIG. 8  is a view of Section  8 - 8  taken in  FIG. 7 . 
         FIG. 9  is a view of another example of the screen depicted in  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     In the following description, certain terms have been used for brevity, clearness, and understanding. No unnecessary limitations are to be implied therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes only and are intended to be broadly construed. The different arrangements and method steps described herein may be used alone or in combination with other arrangements, systems, and method steps. For example, the examples described herein are depicted in the context of inflow control devices. However, the examples are applicable for use with other types of well production equipment. It is to be expected that various equivalents, alternatives and modifications are possible within the scope of the appended claims. 
       FIG. 1  depicts a conventional inflow control device  10  for use in a production well. The device  10  is specially designed to minimize fluctuating production rates and uneven drainage of fluids from a surrounding reservoir  12 , as described in U.S. Pat. No. 7,419,002, the disclosure of which is incorporated herein by reference. The device  10  includes an axially elongated substantially non-perforated production tube or base pipe  14 . An inner layer or wire tube  16  encircles the exterior of the base pipe  14 . As shown in  FIG. 2 , the wire tube  16  includes a series of spaced apart axially extending wires  18  and a series of spaced apart laterally extending wires  20  that extend transversely to the wires  18 . A sand screen or mesh tube  22  encircles the outside of wire tube  16  and a shroud  24  containing a series of perforations  26  overlaps the mesh tube  22 . A series of radial flow paths  28  allow reservoir fluids to flow radially towards the base pipe  14  through the perforations  26 , the mesh tube  22 , and the wire tube  16 . 
     An axial flow path  30  extends along the exterior of the non-perforated base pipe  14  and has a height H defined by the spacing between the exterior face of the based pipe  14  and the interior face of the wire tube  16 . One or more inlets  32  are provided in the base pipe  14  at the upstream end of the axial flow path  30 . As explained in the aforementioned U.S. Pat. No. 7,419,002, at least one flow restriction such as the inlet  32  itself or an insert (not shown) is provided in the flow channel. The insert can include a nozzle or an orifice in the shape of a slit or a hole or any other flow restriction. The flow restriction (e.g., 32) has a fixed flow cross-section sized to receive reservoir fluids and to permit pressure reduction and thereby control of reservoir fluid flow by fluid collision between reservoir fluid that has passed through the flow restriction and downstream fluid. 
     Inflow control devices  10  are often designed to extend axially more than 32 feet in length to achieve the desired reservoir contact and/or flow control characteristics. However sand screens such as the mesh tube  22  shown in  FIG. 1  are typically manufactured in sections that are 16 feet or less in axial length. Therefore, the applicant has found that it is necessary to join two or more screen sections in series (i.e., end-to-end) to create an inflow control device  10  that is longer than 16 feet. While pursuing this objective, the applicant was unsuccessful in its attempts to effectively incorporate several known arrangements for joining two or more sections of sand screens in series (i.e., “end-to-end”) into the inflow control device  10 . Some of these arrangements are described herein below with reference to  FIGS. 3-6 . 
       FIG. 3  depicts one arrangement  34  considered by the applicant for joining two or more sand screen sections in an inflow control device  10 . The arrangement includes a base pipe  36  having a high-density pattern of perforations  37 . An inner layer or wire tube  38  is wrapped around the exterior of the base pipe  36 . The wire tube  38  includes a series of spaced apart axially extending wires  40  and spaced apart laterally extending wires  42  that extend transversely to the wires  40 , as shown in  FIG. 4 . A sand screen or mesh tube  44  is wrapped around the outside of wire tube  38  and a shroud  46  containing a series of perforations  48  overlaps the mesh tube  42 . A series of radial flow paths  50  are defined for reservoir fluids to flow radially into the base pipe  36  through the perforations  48 , the mesh tube  44 , the wire tube  38 , and perforations  37 . The mesh tube  44  includes a first section  52  and a second section  54  that are joined by a junction ring  56 . The junction ring  56  contains an outwardly extending lip or flange portions  58 . The flange portions  58  underlie an end portion  60  of the first section  52  of the mesh tube  44  and an end portion  62  of the second section  54  of mesh tube  44 . The junction ring  56  thus provides a backing for the filter mesh  26  and a point at which the filter mesh  26  can be welded together at defined welding points  64 . 
     The arrangement shown in  FIGS. 3 and 4  may not be effectively and efficiently incorporated into the inflow control device  10  shown in  FIG. 1 . The junction ring  56  extends towards or up to the exterior surface of the base pipe  36  and therefore substantially prevents or blocks fluid from flowing axially along (i.e., adjacent to) the exterior surface of the base pipe  36 . This “blocking effect” presents a significant problem if the junction ring  56  is incorporated into the inflow control device  10  shown in  FIG. 1 , which is designed to promote both radial flow along flow paths  28  and axial flow along flow path  30 . In other words, in the inflow control device  10 , it is necessary to minimize the amount of restriction along the length of the axial flow path  30  to prevent fluid pressure losses and maintain a constant flow. The presence of the junction ring  56  protruding into or blocking the axial flow path  30  disrupts flow of fluid through the path  30  and thus interferes with the operation of the inflow control device  10 . 
       FIG. 5  depicts another arrangement  66  considered by the applicant for joining two or more sand screen sections in an inflow control device  10 . The arrangement includes a perforated base pipe  68 . An inner layer or wire tube  70  is wrapped around and encircles the exterior of the base pipe  68 . The wire tube  70  includes a series of spaced apart axially extending wires  72  and spaced apart laterally extending wires  74  that extend transversely to the wires  72 , as shown in  FIG. 6 . A sand screen or mesh tube  76  is wrapped around the outside of the wire tube  70  and a shroud  78  containing a series of perforations  80  overlaps the mesh tube  76 . A series of radial flow paths  82  are defined for reservoir fluids to flow radially towards the base pipe  68  through the perforations  80 , the mesh tube  76 , and the wire tube  70 . The mesh tube  76  includes a first section  84  and a second section  86 . An axial end  88  of the first section  84  is welded directly to an axial end  90  of the second section  86  by a butt weld  92 . 
     The arrangement shown in  FIGS. 5 and 6  may not be effectively and efficiently incorporated into the inflow control device  10  because the quality of the butt weld  92  shown in  FIG. 5  is very difficult to control or verify. The quantity of weld penetration can vary widely from partial to full penetration. Full penetration of the weld results in the best joint achieving the maximum joint strength. However in the arrangement  66 , there is no efficient quality control measure during production that could ensure that full weld penetration was achieved. 
       FIG. 7  depicts an arrangement  100  for producing fluids from an underground reservoir that surprisingly overcomes many of the disadvantages of the attempts shown in  FIGS. 2-6 . 
     An inner layer or wire tube  102  is wrapped around the exterior of an axially elongated substantially non-perforated production tube or base pipe  104 . The wire tube  102  includes a series of spaced apart axially extending wires  106  and a series of spaced apart laterally extending wires  108  that extend transversely to the wires  106 , as shown in  FIG. 8 . A sand screen or mesh tube  110  is wrapped around the outside of wire tube  102  and a shroud  112  containing a series of perforations  114  overlaps the mesh tube  116 . A series of radial flow paths  118  are defined for reservoir fluids to flow radially towards the base pipe  104  through the perforations  114 , the mesh tube  116 , and the wire tube  102 . 
     An axial flow path  120  extends along the exterior of the non-perforated base pipe  104  and has a height H defined by the spacing between the exterior of the based pipe  104  and the interior of the wire tube  102 . One or more inlets  122  are provided in the base pipe  104  at the upstream end of the axial flow path  120 . At least one flow restriction (e.g.,  122 ) is provided in the flow path  120  and can include a nozzle or an orifice in the shape of a slit or a hole or any other flow restriction. The flow restriction (e.g.,  122 ) has a fixed flow cross-section sized to receive reservoir fluids and to permit pressure reduction and thereby control of reservoir fluid flow by fluid collision between reservoir fluid that has passed through the flow restriction (e.g.,  122 ) and downstream fluid. 
     The sand screen or mesh tube  110  includes first and second sections  124 ,  126  that filter reservoir fluids flowing radially into the base pipe  104  along flow paths  118 . The first section  124  has a downstream end portion  128  and the second section  126  has an upstream end portion  130 . The downstream end portion  128  and upstream end portion  130  are overlapped and connected by a lap joint  132 . In the example shown, the lap joint  132  is formed by swaging the downstream end portion  128  out away from the base pipe  104  and swaging the upstream end portion  130  in towards the base pipe  104 . Note that this is one preferred arrangement and could be modified accordingly. For example, the lap joint could be formed by having only one of the downstream and upstream end portions  128 ,  130  swaged in towards the base pipe  104  or out away from the base pipe  104 . The lap joint  132  is welded by a weld  134  which can be for example a butt weld, fillet weld or like in such a manner that the downstream portion  124  forms a backing for the weld  134  which can be for example a butt weld, fillet weld or like. This ensures a quality weld and overcomes the disadvantages of the arrangement  66  shown in  FIG. 5 . 
       FIG. 9  depicts an additional example wherein each end portion  128 ,  130  comprises an edge  136 ,  138  that is chamfered to achieve a better fit between the end portions. 
     The arrangements and methods described with reference to  FIGS. 7-9  surprisingly provide several functional advantages over the prior art. For example, the lap joint  132  facilitates a smaller radial clearance between the shroud  112  and the mesh tube  110 , which greatly improves burst characteristics of the mesh tube  110 . That is, the smaller the radial clearance between the shroud  112  and the mesh tube  110 , the less likely the mesh tube  110  is to expand towards the shroud  112 . This helps maintain the pore size in the mesh under burst conditions and thus does not compromise the filtering ability of the mesh tube  110 . The lap joint  132  also facilitates a larger radial clearance H between the outside of the base pipe  104  and the inside surface of the wire tube  102 . As discussed above, this is highly advantageous because it minimizes the amount of flow restriction on fluids flowing axially through the axial flow path  120 . 
     The arrangements shown in  FIGS. 7-9  allow for design of an inflow control device  10  that utilizes multiple mesh tube sections to achieve the desired screen to reservoir contact length. Although  FIGS. 7-9  show two sections of sand screen joined together, it is recognized that additional sections can be connected in series to arrive at a substantially longer inflow control device  10 .