WO2004035235A1

WO2004035235A1 - A screen support

Info

Publication number: WO2004035235A1
Application number: PCT/IB2003/000769
Authority: WO
Inventors: George Alexander Burnett
Original assignee: Varco I/P, Inc.; Lucas, Brian, Ronald
Priority date: 2002-10-17
Filing date: 2003-02-27
Publication date: 2004-04-29
Also published as: GB0224155D0; AU2003208496A1; AU2003208496A8

Abstract

A screen support (1) having an interface provided with a seal member (44), characterized in that said interface further comprises at least a second seal member (45). A screen support (1) having an interface provided with a seal member (44) and a further seal member (45), the seal member arranged on a surface and, when in use, sealing contact with two further surfaces. The invention also provides a screen provided with the screen support (1) of the invention and a shale provided with a screen of the invention.

Description

Description A SCREEN SUPPORT

[1] The present invention relates to a screen support, a screen comprising a screen support and a shale shaker comprising a screen.

[2] In the drilling of a borehole in the construction of an oil or gas well, a drill bit is arranged on the end of a drill string and is rotated to bore the borehole. A drilling fluid known as "drilling mud" is pumped through the drill string to the drill bit to lubricate the drill bit. The drilling mud is also used to carry the cuttings produced by the drill bit and other solids to the surface through an annulus formed between the drill string and the borehole. The drilling mud contains expensive synthetic oil-based lubricants and it is normal therefore to recover and re-use the used drilling mud, but this requires the solids, to be removed from the drilling mud. This is achieved by processing the drilling fluid. The first part of the process is to separate the solids from the solids laden drilling mud. This is at least partly achieved with a shale shaker, such as those disclosed in US 5,265,730, WO 96/33792 and WO 98/16328.

[3] Shale shakers generally comprise an open bottomed basket having one open discharge end and a solid walled feed end. A number of rectangular screens are arranged in the basket, which are held in C-channel rails located on the basket walls, such as those disclosed in GB-A-2,176,424. The basket is arranged on springs above a receptor for receiving recovered drilling mud. A skip or ditch is provided beneath the open discharge end of the basket. A motor is fixed to the basket, which has a drive rotor provided with an offset clump weight. In use, the motor rotates the rotor and the offset clump weight, which causes the basket and the screens fixed thereto to shake. Solids laden mud is introduced at the feed end of the basket on to the screens. The shaking motion induces the solids to move along the screens towards the open discharge end. The recovered drilling mud is received in the receptor for further processing and the solids pass over the discharge end of the basket into the ditch or skip.

|4J The screens are generally of one of two types: hook-strip; and pre-tensioned.

[5] The hook-strip type of screen comprises several rectangular layers of mesh in a sandwich, usually comprising one or two layers of fine grade mesh and a supporting mesh having larger mesh holes and heavier gauge wire. The layers of mesh are joined at each side edge by a strip which is in the form of an elongate hook. In use, the elongate hook is hooked on to a tensioning device arranged along each side of a shale shaker. The shale shaker further comprises a crowned set of supporting members, which run along the length of the basket of the shaker, over which the layers of mesh are tensioned. An example of this type of screen is disclosed in GB-A-1 ,526,663. The supporting mesh may be provided with or replaced by a panel having apertures therein.

[6] The pre-tensioned type of screen comprises several rectangular layers of mesh, usually comprising one or two layers of fine grade mesh and a supporting mesh having larger mesh holes and heavier gauge wire. The layers of mesh are pre-tensioned on a rigid support comprising a rectangular angle iron frame and adhered thereto. The screen is then inserted into C-channel rails arranged in a basket of a shale shaker. An example of this type of screen is disclosed in GB-A-1, 578,948.

[7] A further example of a known rigid support is disclosed in WO 01/76719, which discloses, amongst other things, a flat plate like portion having openings therein and wing portions which are folded to form a support structure, which may be made from a single sheet of material. This rigid support has been assigned the Trade Mark "U IBODY" by the applicants.

[8] The layers of mesh in the screens wears out frequently and therefore needs to be easily replaceable. Shale shakers are generally in the order of 5ft wide and 10ft long. A screen of dimensions 5ft wide by 10ft long is difficult to handle, replace and transport. It is known to use two, three, four or more screens in a single shale shaker. A standard size of screen currently used is of the order of 4ft by 3ft.

[9] It has been found that, in use, solids pass between adjacent screens and around the ends of screens. This is unsatisfactory, as contamination of the recovered drilling mud could cause damage to other processing equipment and damage to the oil or gas well and well tools and equipment.

[10] An attempt at solving this problem is disclosed in GB-A-2 ,206,501, which discloses a tongue and groove interface between adjacent frames of screens.

[11] PCT Publication Number WO 01 Λ97947 discloses in Figures 1 to 5H improvements in a tongue and groove interface by the addition of a sealing member and in two embodiments, by the addition of two sealing members.

[12] PCT Publication Number WO 01/97947 also discloses a "UNIBODY" rigid support structure disclosed in WO 01/76719, having a lip on one end and a lap on the other, such that, in use, the lap of a first rigid support structure fits under the lip of a second rigid support structure. Either of the lip or lap or both may be provided with a seal member.

[13] In certain circumstances, such as when drilling through porous rock formations, it is desirable to turn porous rock formations surrounding the borehole non-porous. This is achieved by circulating Lost Circulation JMaterial through the drill pipe and back through die annulus formed by the drill string and the borehole. Lost Circulation Material generally comprises a fibrous material. When recovering used drilling mud, it is desirable to separate the fibrous Lost Circulation Material from the drilling mud.

[14] The present invention attempts to provide a seal which will prevent solids from passing between adjacent screens and passing between the end of a screen and a fitting in the shale shaker into which it cooperates in use.

[15] The present invention also attempts to provide a seal, which will last at least as long as the life of the layers of mesh. [16] The present invention also attempts to provide a seal, which inhibits solids falling into the receiver where drilling mud is recovered during replacement of the screen.

[17] The present invention also attempts to retain rigidity in the screen at its interface with another screen or the end fitting arranged in the basket of the shale shaker.

[18] The present invention also provides a seal, which is easily replaceable during reconditioning of the screen.

[19] According to the present invention, there is provided a screen support having an interface provided with a seal member, characterised in that said interface comprises at least a second seal member.

[20] Preferably, the screen support comprises a lap, on which the seal member is located and preferably the further seal member.

[21] The seal member and the second seal member are arranged such that, in use, they seal against at least four surfaces; all four surfaces adjacent one another; two in the same plane as the top surface of the panel and two in perpendicular planes to the top surface of the top surface. The seal seals against two perpendicular surfaces and the further seal seals against two further perpendicular surfaces, this is in addition to the surface on which the seal is arranged, which may be the lap. According to the invention also provides a screen support having an interface provided with a seal member and a further seal member, the seal member arranged on a surface and, when in use, sealing contact with two further surfaces. Preferably, the two further surfaces are perpendicular to one another. Advantageously, the further seal member is arranged on a surface and, when in use, sealing contact with two further surfaces. Preferably, both the seal member and further seal member are arranged on the same surface, which is most preferably a lap provided on the screen support.

[22] Advantageously, the interface comprises a substantially vertical member, below which the seal member is arranged. In use, solids may collect in the gap formed by the substantially vertical member, a wall of an adjacent screen structure and the seal member to inhibit solids from passing though the gap.

[23] Preferably, the seal member spans the entire width of the screen support. Advantageously, the seal member and the further seal member are part circular in cross section. Preferably, the seal member and the further seal member comprise a rubber butyl or a synthetic rubber.

[24] Advantageously, the seal member and the further seal member are arranged on a base, which preferably comprises a rubber butyl or a synthetic rubber. Advantageously, a gap is arranged between the seal member and the base. In use, solids may collect between the seal member and the base to maintain the seal member in contact with or push the seal against a sealing surface on an adjacent screen.

[25] Preferably, the screen support comprises a reinforcing panel comprising at least one folded portion. Advantageously, one of the folded portions retains the seal member or the further the member or both. [26] Advantageously, the screen support comprises a panel having openings therein, which preferably has a least one folded portion. Preferably, at least one of the folded portions retams the seal member or the further seal member or both.

[27] Preferably, interface is located on the forward end of the screen support.

[28] Advantageously, the screen support further comprises a second interface comprising a lip, which preferably has an underside arranged at angle to receive a sealing member. The angle is preferably between 5° and 30° and most preferably 10°.

[29] The invention also provides a screen comprising the screen support of the invention.

[30] The invention also provides a shale shaker comprising a screen of the invention.

[31] For a better understanding of the present invention, reference will now be made, by way of example to the accompanying drawings, in which:

[32] Figure 1 is a side cross-sectional broken view of two screen supports in accordance with the present invention;

[33] Figure 2 A is top plan view of a blank used in the construction of a panel of the screen support in accordance with the present invention;

[34] Figure 2B is a top plan view of a second blank used in the construction of a reinforcing panel of the screen support in accordance with the invention; and

[35] Figure 3 is a scrap side cross-sectional view of an end of part of one of the screen supports shown in Figure 1 having a layer of mesh thereon and located in an end fitting of a shale shaker.

[36] Referring to Figure 1 there is shown two screen supports generally identified by reference numerals 1 and 2 respectively. The screen supports 1 and 2 are substantially identical. Each screen support has a forward end 3, 4 and a trailing end 5, 6. The centre section of each screen has been omitted for clarity.

[37] Screen support 1 comprises a panel 7 and a reinforcing panel 8. A blank from which the panel 7 is formed is shown in Figure 2 A. The panel 7 is made from a 3mm mild steel plate. The panel 7 has a plurality of triangular openings 9 therein, arranged in a pattern as disclosed in PCT Publication Number WO 01/76719 and may be of the type disclosed in PCT Publication Number WO 94/23849 or of any other suitable arrangement of openings. The triangular openings 9 may be punched, cut or cast and have portions 10 folded downwardly along each side of the triangular opening 9. Each side of the triangular opening 9 is adjacent another side of a neighbouring triangular opening 9. The folded portions 10 form channels 11. Twenty channels 11 are arranged at right angles to the left and right sides 12 and 13; perpendicular to the direction of flow of material thereover, when in use. Each channel 11 is continuous, straight and parallel to adjacent channels 11. The panel 7 may be of the type that is fully described in co-pending application entitled "Screen Support" filed with even date. The triangular openings 9 cover a substantial portion of the panel 7. Left side portion 12 and right side portion 13 are not provided with openings. The area of panel 7 comprising the triangular openings 9, the left side portion 12 and right side portion 13, all lie in the same plane to form a flat top surface. Wing portions 14 and 15 approximately 1 cm wide extend the entire length of the panel 7. The wing portions 14 and 15 are folded downwardly to stand approximately at right angles to the top surface. The forward end of the panel 7 has a forward end portion 16 extending the width of the panel 7 and is folded downwardly along line 17 to form an end face of a screen interface. The forward end portion 16 has a further portion 18 folded along line 19, projecting forwardly. The trailing end of the panel 7 has a rear end portion 20 folded downwardly along fold line 21, such that the rear end portion 20 lies at approximately right angles to the top surface. The folded wing portions 13 and 15 and the folded end portions 16 and 20 meet at their respective edges, at which they may be welded together, soldered or otherwise joined.

[38] The reinforcing panel 8 is formed from a blank, which is shown in Figure 2B. The blank is made from a 3mm mild steel plate. The reinforcing panel 8 has five openings 22 therein. Each opening 22 has been punched, cut or cast into the blank having a central oblong opening 23 and slots 24 approximately 4cm long extending longitudinally at each end of the central oblong opening 23 to form ten structural support portions 25, which are folded upwardly along fold lines 26 to stand approximately at right angles to the surface of the reinforcing panel 8. The reinforcing panel 8 has a left side portion 27 and a right side portion 28. The left and right side portions 27 and 28 extend the entire length of the reinforcing panel 8 and are not provided with openings. Wing portions 29 and 30 approximately 4cm wide extend the entire length of the reinforcing panel 8. The wing portions 29 and 30 are folded upwardly along lines 31 and 32 respectively to stand approximately at right angles to the surface of the reinforcing panel 8. The forward end of the reinforcing panel 8 has a forward end portion 33 extending the width of the reinforcing panel 8 and from the reinforcing panel 8 to form a lap of the screen interface. A further portion 34 is folded upwardly along line 35. The trailing end 5 of the reinforcing panel 8 has a rear end portion 36 folded upwardly along fold line 37, such that the rear end portion 20 lies at approximately right angles to the surface of the reinforcing panel 8. The further portion 38 is folded outwardly from the reinforcing panel to an angle of approximately 10° upwardly from the plane in which the reinforcing panel 8 lies. A final portion 40 extends vertically to a level which is in the same plane as the tops of the structural support portions 25, approximately 4cm from the surface of the reinforcing panel 8. The folded wing portions 29 and 30 and the folded end portions 33 and 36 meet at their respective edges, at which they may be welded together, soldered or otherwise joined.

[39] The downwardly folded wings 14 and 15 of the panel 7 are located over the upwardly folded wings 29 and 30 of the reinforcing panel 8 and welded together. Each of the ten structural supporting members 25 of the reinforcing panel 8 are located in every other of the twenty channels 11 and welded therein. [40] A sealing member 42 comprises an elongate rubber butyl or synthetic rubber having, in section, a square base 43 and two part circular seal members 44 and 45 lying adjacent one another forming a gully 46. The part circular seal members 44 and 45 are arranged on an upper part of the square base 43 and are adhered or integral with one another. The square base 43 of the sealing member 42 is located on the forward end portion 33 of the reinforcing member 8 and on a forward side of the seal by the further portion 34 of the reinforcing member 8. The further portion 18 of the panel 8 embeds itself into the square base of the sealing member 42, which may have a slot therein for receiving the further portion 18. The sealing member extends across the entire width of the screen support 1.

[41] Layers of mesh, not shown, are laid on top of the panel 7 of the screen support 1 and adhered, bonded or otherwise attached to the panel 7 to form a screen. The layers of mesh may be pre-tensioned and then bonded to the panel 7.

[42] Referring to Figure 3, in use, the screen support 1 has at least one layer of mesh 47 adhered thereto over the area of the openings 9 to form a screen 48. The screen 48 may be fitted into a shale shaker by sliding it into C-channel rails located on sidewalls of a shale shaker, one of which is shown and identified by reference numeral 49 on sidewall 50 of the basket of the shale shaker. The C-channel rail 49 has a bottom element 51 on which the screen support 1 rests and an upper element 52 on which a pneumatic bladder 53 is fixed. The pneumatic bladder 53 is inflated to hold the screen in place and to provide a seal between the left and right side portions 12 and 13 of the screen support 1 and the C-channel rails 49. An end fitting generally identified by reference numeral 54 is located in a C-channel rail 55 formed by a top curved section rail 56 and a bottom curved section rail 57. The end fitting 54 comprises a block 58 extending at least the width of the screen support 1. The block 58 is welded to the C- channel rail 55 at points 59 and 60. A buffer 61 also extend the width of the screen support 1 and is bolted to the block 58. The buffer 61 comprises an end seal member 62 made from a rubber butyl or a synthetic rubber, which extends the entire width of the screen support 1 for abutting the end face of the forward end of the screen support 1. The buffer 61 also comprises a recess 63 having an angled upper face 64 at the mouth of the recess, at an angle of 25° from the plane in which the screen support 1 lies. The part circular seal members 44 and 45 of the seal member 44 contact the angled upper surface 64 and may contact an upper surface 65 of the recess, forming a seal, inhibiting solids such as drill cuttings, lost circulation material, and other particles from passing between the interface between the screen 48 and the end fitting 54 into which the screen 48 is fitted.

[43] A further screen may be slid into the C-channels 49 behind the screen 48. The way in which the further screen interfaces with the screen 48 is shown in Figure 1. A forward end portion 16a of the further screen support 2 abuts the rear end portion 20. Part circular seal members 44a and 45a seal against the further portion 38 of the trailing end of the first screen support 1. A gap 66 is formed between an end of the rear end portion 20 and first part circular seal member 45a, in which solids collect and, in themselves, form a seal. It appears that the second part circular seal member 44a is left to seal against the further portion 38 of the trailing end of the screen support 1 , without substantial hindrance or effect from the larger solids in the gap 66. [44] A further gap 67 is formed between the first part circular seal member 45a and a further portion 18a of panel 7a. The further gap may fill with solids, in use, which may push towards or at least retain the first part circular seal member 45a in contact with the further portion 38 of the trailing end of the first screen support 1, creating an improved seal.

Claims

[I] A screen support having an interface provided with a seal member, characterised in that said interface comprises at least a second seal member

[2] A screen support as claimed in Claim 1, further comprising a lap.

[3] A screen support as claimed in Claim 2, wherein said seal member is located on said lap.

[4] A screen support as claimed in Claim 2 or 3, wherein said second seal member is located on said lap. [5] A screen support as claimed in any preceding claim, wherein said interface comprises a substantially vertical member, below which the seal member is arranged. [6] A screen support as claimed in any preceding claim, wherein the screen support has a width, the seal member spanning said width. [7] A screen support as claimed in any preceding claim, wherein said seal member and said second seal member are part circular in cross section. [8] A screen support as claimed in any preceding claim, wherein said seal member is substantially circular in cross section. [9] A screen support as claimed in any preceding claim, wherein said seal member and said second seal member are in sealing contact with each other. [10] A screen support as claimed in any preceding claim, wherein said seal member and said second seal member comprise a rubber butyl or a synthetic rubber.

[II] A screen support as claimed in any preceding claim, wherein said seal member and said further seal member are fixed or integral with a base.

[12] A screen support as claimed in Claim 11 , wherein said base comprises a rubber butyl or a synthetic rubber. [13] A screen support as claimed in Claim 11 or 12, wherein a gap is arranged between said seal member and said base. [14] A screen support as claimed in any preceding claim, wherein said screen support comprises a reinforcing panel comprising at least one folded portion. [15] A screen support as claimed in Claim 14, wherein a folded portion of said reinforcing panel retains said seal member or said further seal member or both. [16] A screen support as claimed in any preceding claim, wherein said screen support comprises a panel having openings therein. [17] A screen support as claimed in Claim 16, wherein said panel has a least one folded portion. [18] A screen support as claimed in Claim 17, wherein a folded portion of said panel retains said seal member or said further seal member or both. [19] A screen support as claimed in any preceding claim, wherein said screen support has a forward end, wherein said interface is located on said forward end of said screen support. [20] A screen support as claimed in any preceding claim, further comprising a second interface comprising a Up. [21] A screen support as claimed in Claim 18, wherein said Up has an underside arranged at angle to receive a sealing member. [22] A screen support as claimed in Claim 18, wherein said angle is between 5° and 30° [23] A screen support as claimed in Claim 18, wherein said angle is 10°.

[24] A screen support having an interface provided with a seal member and a further seal member, the seal member arranged on a surface and, when in use, sealing contact with two further surfaces. [25] A screen support as claimed in Claim 24, wherein the two further surfaces are perpendicular to one another. [26] A screen support as claimed in Claim 25, wherein the further seal member is arranged on a surface and, when in use, sealing contact with two further surfaces. [27] A screen support as claimed in Claim 24, 25 or 26, wherein both the seal member and further seal member are arranged on the same surface. [28] A screen comprising the screen support as claimed in any preceding claim and at least one layer of screening material. [29] A screen as claimed in Claim 28, comprising a coarse layer of mesh for supporting said at least one layer of screening material. [30] A shale shaker comprising a screen as claimed in Claim 28 or 29.