Abstract:
A retrievable drill pipe screen is adapted for releasable connection within a drill pipe string. The screen has a planar support plate for connecting a perforated tubular screen body to a fish neck wherein the plane of the planar support plate is generally parallel to the axis of the screen body. The orientation of the planar support plate provides minimal resistance to fluid flowing into the screen body while also reducing vortex effects that cause wear of screen components. Preferably, a wear distributor sleeve is fit within the screen body for protecting against wear of the screen caused by fluid flow and a retaining rod can secure the bottom of the screen body to the fish neck in the event that a lower portion of the screen body becomes detached.

Description:
FIELD OF THE INVENTION  
       [0001]     The invention relates to screens and in particular to retrievable screens for fitting within the bore of a pipe, such as a drill pipe.  
       BACKGROUND OF THE INVENTION  
       [0002]     In the drilling of a subterranean rock formation, tubing such as a drill stem assembly or drill pipe string conducts drill mud or drilling fluids downhole to tools such as mud motors or a drill bit. Drilling fluids are circulated downhole through the tubing for a variety of purposes including carrying drill cuttings up an annulus about the tubing and to the surface for screening, reconditioning and recirculation. In drilling with coiled tubing, mud motors are powered by the flow of drilling fluids and are used to rotate the bit. In conventional rotary drilling, the drill pipe string is used to rotate the bit. In either case, there are one or more connections in which a screen can be installed to intercept debris and other oversize material carried by the drilling fluids which could interfere with the downhole tools. Ideally, a retrievable screen is used such that the screen may be occasionally removed, cleaned and reinstalled without having to extract the tubing from the hole.  
         [0003]     A variety of retrievable drill pipe screens have been disclosed in the prior art. Some prior art screens are supported on a mounting collar that is sandwiched between interconnecting uphole pipe and downhole pipe of a drill pipe string. Such screens comprise a screen support ring that is adapted to releasably engage the mounting collar and from which a screening member depends downhole into the bore of the downhole pipe. Conventional means for enabling retrieval of the screen from the drill pipe string include a fish neck connected to the screen support ring and which extends uphole therefrom. The fish neck is engageable by a conventional overshot fishing tool for pulling the fish neck and screen free from the mounting collar. Sometimes the fish neck is connected to the screen support ring by leg support members that are welded to the fish neck and the support ring in a so-called “pyramid” or “spider leg” configuration. Alternatively, as disclosed in U.S. Pat. No. 4,495,073, the fish neck may be connected to the screen by a bridging bar secured in transverse relationship to the screen support ring onto which the fish neck is centrally attached.  
         [0004]     Applicant has found that such prior art means for attaching a fish neck to a screen may restrict flow of fluid into the screen and thereby impede the rate of flow of fluid down the drill stem. Furthermore, such restrictions do little to alleviate wear due to fluid flow conditions including vortices in the fluid flowing through the screen and also that due to pressure difference thereacross which accentuates wear. Wear can result in various failure modes including: of the screening member, of the attachment between the screening member and the screen support ring, and of the attachment between the fish neck and the support ring.  
         [0005]     There is, therefore, a need in the art for an improved retrievable pipe screen.  
       SUMMARY OF THE INVENTION  
       [0006]     A retrievable drill pipe screen is provided for intercepting debris flowing through the pipe while minimizing disturbance of the flow of the drilling fluids and which is less susceptible to wear as compared with conventional retrievable drill pipe screens.  
         [0007]     In one embodiment of the invention, a planar support plate connects an uphole extending fish neck with a downhole extending tubular screen body whereby the plane of the support plate is aligned with the flow of the drilling fluids. The orientation of the support plate thereby minimizes the effect of the support plate on the flow of the drilling fluid from an uphole pipe, and through the screen body into a downhole pipe. At the same time, longitudinally extending planar surfaces of the planar support plate interfere with vortex motion of the drilling fluids as it enters the screen body, thereby lessening erosive wear on screen components.  
         [0008]     Accordingly, in a broad aspect of the invention, a retrievable drill pipe screen is provided comprising a perforated tubular screen body having an inner sidewall surface, a bottom and an open top, the screen body sized to fit within the bore of the pipe; a fish neck projecting outwardly from the open top and generally positioned along an axis of the screen body; at least one planar support plate extending between the fish neck and the screen body, the plane of which is generally parallel to the axis, each of the at least one planar support plate having a first edge attached thereby to the fish neck, and having an opposing second edge attached thereby to the inner sidewall surface of the screen body; and a releasable connection for interconnecting the retrievable screen with the pipe, wherein a retrieving force applied to the fish neck is transferred to the screen body and wherein the retrieving force effects disconnection of the releasable connection, thereby permitting retrieval of the retrievable screen from the bore of the pipe.  
         [0009]     Preferably, the screen body has a conical shape with a rounded, cup-shaped end to aid in cleaning of the screen body when removed from the pipe. To reinforce the integrity of the screen body, the retrievable screen may further comprise a retaining rod extending between the fish neck and the bottom of the screen body and attached thereto.  
         [0010]     The releasable connection may include any connection that provides sufficient strength to support the drill pipe screen while in operation, but which can be disconnected when required without causing detachment of the fish neck from the screen body. A suitable such releasable connection includes a screen support ring from which the screen body downwardly depends and which is adapted to be supported an annular mounting collar that is secured within an annular recess defined by the pipe, whereby an upwardly facing annular shoulder of the mounting collar abuts with a downwardly facing surface of the screen support ring. The screen support ring and mounting collar are releasably connected by at least one radially disposed shear pin connecting radially adjacent portions of the mounting collar and screen support ring.  
         [0011]     In another embodiment of the invention, a wear distributor sleeve is provided that is fit within the screen body and positioned at the uphole end thereof. The wear distributor sleeve protects the screen body against vortex motion of the drilling fluid as it enters the screen body. When a wear distributor sleeve is included in the screen, the planar support plate is attached directly to the inner sidewall surface of the wear distributor sleeve. To reduce blockage of the screen body by the wear distributor sleeve, extraneous material of the wear distributor sleeve, such as where the planar support plate is not attached and where the wear distributor sleeve does not protect against the vortex effects of the drilling fluid, may be removed. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is a cross-sectional view of one embodiment of a retrievable screen of the present invention installed in a drill pipe;  
         [0013]      FIG. 2A  is a sectional view taken along lines  2 - 2  of  FIG. 1 ;  
         [0014]      FIG. 2B  illustrates another embodiment of a planer support member herein the support member has a planar curve configuration;  
         [0015]      FIG. 3  is a cross-sectional view of another embodiment of the retrievable screen of the present invention;  
         [0016]      FIG. 4  is a top perspective view of the embodiment of  FIG. 3  with the downhole portion of the screen body partially removed; and  
         [0017]      FIG. 5  is an exploded view of the embodiment of  FIG. 3  illustrating the mounting collar and a shear pin, a partial view of the screen, and a combined view of fish neck, support plate, screen support ring, wear distributor sleeve, and retaining rod.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0018]     With reference to  FIGS. 1 and 2 , a drill pipe screen  2  is shown installed within the bore  3  of a drill pipe string  4 . Generally, the components of the screen are sized according to the inner diameter of the pipe being used and are preferably constructed of wear and corrosion resistant material such as 316 stainless steel. The components are securely attached to each other as indicated herein by any suitable means known in the art, such as, for example, by welding.  
         [0019]     With reference to  FIG. 1 , the screen  2  comprises an elongate and perforated tubular screen body  16  which is securely attached to a screen support ring  14  and extends downhole therefrom. An uphole open top end  18  of the screen body  16  abuts to a downwardly facing surface  12  of the screen support ring  14 .  
         [0020]     The drill pipe screen  2  is adapted for support upon an annular mounting collar  6  that is anchored within the bore of the pipe. Typically, the mounting collar is sandwiched within an annular recess defined between two interconnected pieces of uphole pipe  8   a  and downhole pipe  8   b . The mounting collar  6  defines an upwardly facing annular shoulder  10 .  
         [0021]     The downwardly facing surface  12  of the screen support ring  14  is abuttingly engageable and supported upon the upwardly facing annular shoulder  10 . At least one, and preferably several radially disposed shear pins  15  extend between the mounting collar  6  and the support ring  14  to provide a releasable connection for interconnecting the screen with the drill pipe string  4 .  
         [0022]     In operation, drilling fluids flowing downhole enters the open top end  18  of the screen body from the uphole pipe  8   a  and passes through the screen body  16  into the downhole pipe  8   b . Perforations  20  in the screen body  16  are sized to permit ready passage of drilling fluids therethrough but to trap, within the screen body, oversized particles which could potentially damage downhole tools. Preferably, the downhole bottom end of the screen body  16  is fit with a rounded, cup-shaped end piece  17  of screen material. As compared to a flat bottom end, the cup-shaped end piece  17  is less susceptible to failure when subjected to the fluid pressures of the drilling fluids and loading of trapped particles.  
         [0023]     To enable retrieval of the screen  2  when required, a fish neck  22  is provided that extends outwardly from the screen support ring  14  and into the uphole pipe  8   a . The fish neck  22  is generally positioned along an axis  24  of the screen body  16  and of the drill pipe string  4 , thereby centering the fish neck with the screen body  16  and the screen support ring  14 . The fish neck  22  is any conventional fish neck already known in the art, such as that generally having a cylindrical post member  26  with a mushroom shaped tip  28 .  
         [0024]     The fish neck  22  is connected to screen body  16  by a planar support plate  30  that extends generally radially between the fish neck  22  and screen body  16 . Broadly stated, the planar support plate has two opposing planar surfaces  32  and a cross-sectional thickness  33  when sectioned transverse through the support plate. The support plate  30  is oriented to minimize disruption of fluid flow from the uphole pipe  8   a  into the screen body  16 . Notably, the generally radially and longitudinally extending planar surfaces  32  interfere with any swirling or vortex motion of the drilling fluids flowing therethrough. Retardation of such vortex motion is useful in lessening erosive wear of the screen components.  
         [0025]     In particular, a plane  31  through or tangent to the planar support plate  30  is generally parallel to the axis  24  such that the planar support plate  30  is in longitudinal relationship along said axis  24 , thereby providing a longitudinal first edge  34  that is securely attached to the post member  26  and an opposing longitudinal second edge  36  that is securely attached to the inner sidewall  38  of the screen body  16  and to the inner sidewall  40  of the screen support ring  14 . The attachment of the planar support plate  30  to the screen body  16  may be achieved by, for example, plug welding through the perforations  20 . Some examples of the transverse cross-sections of planar support plates include “I” ( FIG. 2A ), “C” ( FIG. 2B ), and “V” (Not shown). The flat, planer “I” support plate provides the least resistance to fluid flow thereby.  
         [0026]     The planar support plate  30  may be of any suitable shape, providing that the longitudinal first and second edges  34 ,  36  generally conform to the surface to which they respectively attach. Preferably, the support plate  30  is a flat, wing-shaped parallelogram whereby a resultant, downwardly angled leading edge  41  increases the aerodynamic entry of drilling fluid past the support plate  30 . Furthermore, a corresponding angled trailing edge  43  results where the support plate is cut from flat bar stock with little waste of material. In any case, the cross-sectional thickness  33  of the support plate  30  should be as thin as possible to minimize flow restriction and pressure drop across the open top end  18  of the screen body  16  while providing sufficient structural support for retrieval of the drill pipe screen  2 . Typically, the cross-sectional thickness  33  would not exceed the cross-section of cylindrical post  26  of the fish neck as seen particularly in  FIG. 2 .  
         [0027]     To retrieve the drill pipe screen  2 , a conventional overshot tool engages the tip  28  of the fish neck and an upward force is exerted to effect shearing of the shearing pins  15  and detachment or disconnection of the screen support ring  14  from the mounting collar  6 . The portions of the screen  2  comprising the screen support ring  14 , screen body  16 , fish neck  14 , and support plate  30  are lifted out of the drill pipe string  4 . The screen can be inverted at the surface to remove trapped particles from the screen body  16 . While the screen body  16  may be of any suitable tubular shape, the truncated conical shape with the cup-shaped end piece  17  depicted in the Figures aids in the release of accumulated debris from the screen during cleaning.  
         [0028]     Although the invention has thus been described as having one planar support plate  30 , more than one planar support plate can be used. For example,  FIGS. 2-5  show a drill pipe screen  2  having two opposing planar support plates  30 . Additional support plates  30  are particularly useful for increasing the strength of the fish neck  22  attachment to the screen  2  relative to the strength of the interconnection between the screen support ring  14  and the mounting collar  6 , thereby reducing the likelihood of the fish neck detaching from the screen body  16  during retrieval. Additional support plates  30  are also useful when increased support of the fish neck  22  is required with larger screen bodies  16  and to provide additional support of the fish neck  22  during forceful cleaning efforts.  
         [0029]     Optionally, a retaining rod  42  is provided that extends along axis  24  between the post member  26  of the fish neck  22  and the cup-shaped end piece  17 . In the event that circumferential wear of the screen body  16  occurs below the support plate  30 , the retaining rod will minimize opportunity for detached pieces of the screen body  16  to enter the downhole pipe  8   b  and potentially interfering with downhole processes. The retaining rod  42  also provides additional support to the fish neck during cleaning procedures.  
         [0030]     With reference to  FIGS. 3-5 , in another embodiment, the drill pipe screen  2  can be fit with a tubular wear distributor sleeve  44  positioned adjacent to the inner sidewall  40  of the screen support ring  14  and extending downhole therefrom. The wear distributor sleeve  44  is securely attached to the screen support ring  14 , such as through welding along the circumferential interface therebetween. The second longitudinal edge  36  of the planar support plate  30  is securely attached to screen body  16  through an inner sidewall of  46  of the wear distributor sleeve  44 . An assembly of the fish neck  22 , planar support plate  30 , screen support ring  14 , and wear distributor sleeve  44  is thus provided. The wear distributor sleeve  44  is fit into the screen body  16  until the downwardly facing surface  12  of the screen support ring  14  abuts the top  18  of the screen body. The wear distributor sleeve  44  is then securely attached to the inner sidewall  38  of the screen body  16 , such as by plug welding through the perforations  20  in the screen body  16 . Preferably, the support plate  30  is attached to both the wear distributor sleeve  44  and the screen body  16 , for example, by plug welding through the screen body perforations  20  and one or more slots (not shown) formed in the wear distributor sleeve  44 . The surface area of the wear distributor sleeve  44  which blocks the perforations  20  can be minimized while still providing protection against wear. For example, as best shown in  FIGS. 3 and 4 , the sidewall of the lower portion  50  of the wear distributor sleeve  44  can be a scallop shape having notches  52  extending upwardly from the bottom  54  of the wear distributor sleeve  44  where the planar support plate  30  is not attached thereto.  
         [0031]     Although preferred embodiments of the invention have been described in some detail herein above, those skilled in the art will recognize that various substitutions and modifications of the invention may be made without departing from the scope of the invention as defined by the claims as defined herein.