A relatively thin walled sleeve having a premachined window is disposed at a casing window in a wellbore. The sleeve is set in place with the casing or on a separate run wherein the running tool also includes a dog to align the sleeve premachined window with the casing window both linearly and rotationally in the wellbore. The sleeve is swedged in place in part or completely and a subsequent run provides a lateral liner which extends through both the premachined window and the casing window and seals against the premachined window which will then prevent sand entering the wellbore.

CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of an earlier filing date from U.S. Provisional Application Serial No. 60/264,371 filed Jan. 26, 2001, the entire disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     A multilateral wellbore system by definition includes at least a primary wellbore and a lateral wellbore extending therefrom. The junction between the primary wellbore and the lateral wellbore in some cases is an avenue for sand and other particulate matter infiltration into the wellbore system which generally results in the entrainment of such particulate matter with the production fluid. Clearly, it is undesirable to entrain particulate matter in production fluid since those particulates would then need to be removed from the production fluid adding expense and delay to a final release of a product. The reasons for particulate infiltration through a junction in a multilateral wellbore are many, including the not entirely controllable window size and shape which is generated by running a milling tool into the primary wellbore and into contact with a whipstock whereafter the mill tool mills a window in the casing of the primary wellbore. The milling process itself is not precise and thus it is relatively unlikely that a precise window shape and size can be produced. Lateral liners run in to extend through a milled window and into a lateral borehole are constructed with regular patterns and sizes at the surface. When a regular pattern at the top of such a liner is seated against a milled window in the downhole environment, it is relatively unlikely that the liner flange will seat correctly in all regions of a milled window. This leaves gaps between the flange of the liner and the milled casing in the primary wellbore resulting in the aforesaid avenue for infiltration of particulate matter to the wellbore system. A device and method capable of reducing the amount of particulate matter infiltrating the wellbore system at a junction in a multilateral wellbore will be beneficial to downhole arts. 
     SUMMARY OF THE INVENTION 
     Sand and other particulate matter is significantly excluded from junctions in level 3 multilateral wellbore systems by employing a thin walled sleeve having a premachined window therein in conjunction with the conventional milling of a window in the primary wellbore casing. The premachined window exhibits a known and easily controlled shape and size which lends itself to assurance that a commercially available liner hanger will seal thereagainst since the liner hanger and the sleeve are machined in controlled conditions at the surface for the purpose of sealing with one another. The installation of the sleeve with the premachined window ensures that at the ID of the wellbore casing, the window surface “seen” by the liner hanger system is one against which the liner hanger system is sealable. The seal of the liner hanger may be by any number of methods, two preferred methods being by an elastomeric seal placed between the flange of the liner hanger and the sleeve, and a metal-to-metal interference fit resulting in deformation of the window sleeve outward during installation of the liner. In addition a hook liner hanger embodiment is disclosed. All of these alternate methods of providing a seal are effective and each have benefits which are attractive for certain applications. The sleeve is preferably swaged at an uphole end thereof, a downhole end thereof, both or in its entirety depending upon the application and desires of the operator. In one embodiment, the casing itself of the primary wellbore is provided with a cylindrical recess capable of receiving the sleeve such that the ID of the sleeve is substantially the same diameter as the ID of the casing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring now to the drawings wherein like elements are numbered alike in the several Figures: 
     FIG. 1 is a cross-section view of a thin walled sleeve with premachined window; 
     FIG. 2 is a cross-section view of the thin walled sleeve installed on a running tool which is illustrated schematically, the running tool including a locating dog; 
     FIG. 3 is a schematic illustration of the thin walled sleeve installed with the uphole and downhole sections of the sleeve swaged against the ID of the casing; 
     FIG. 4 is an illustration in cross-section of the thin walled sleeve installed in a fully swaged condition against the ID of the casing wherein an alternate casing segment is employed having a recess to accept the thin walled sleeve; 
     FIG. 5 is an illustration similar to FIG. 4 with the lateral liner installed; 
     FIG. 6 is a view of a section of a primary casing with a whipstock installed therein prior to milling the primary casing; 
     FIG. 7 is an illustration similar to FIG. 6 but illustrating the drill bit being run downhole; 
     FIG. 8 illustrates the primary casing after drilling creating a window in the primary casing and a lateral borehole; 
     FIG. 9 illustrates the view of FIG. 8 after the whipstock is removed; 
     FIG. 10 is an illustration of the sleeve being located at the junction interface with a running tool; 
     FIG. 11 illustrates the running tool swaging and uphole end of the thin walled sleeve against the casing ID; 
     FIG. 12 illustrates the sleeve in position within the wellbore; 
     FIG. 13 is a similar view to FIG. 12 with the lateral liner installed therein; 
     FIG. 14 is a schematic view of an alternate embodiment of the sleeve employing an orientation anchor; 
     FIG. 15 is a view of the FIG. 14 embodiment after swedging of the uphole end; and 
     FIG. 16 is a schematic section view of an embodiment employing a hook liner hanger. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, a thin walled sleeve  10  is illustrated having a premachined window  12 . Sleeve  10  is preferably constructed of steel with a thickness of from 0.125 inch to 0.250 inch. A preferred thickness of 0.197 inch is selected to facilitate relatively easy swaging yet provide sufficient resiliency in the sleeve to ensure a close proximity of a liner extending therethrough to said sleeve sufficient to facilitate bridging of a particular matter which would otherwise pass between said sleeve and said liner to contaminate produced fluids. In another preferred embodiment the liner is sealed against said sleeve. In a preferred embodiment, bands  13  are positioned around sleeve  10  to aid in sealing and anchoring sleeve  10  against casing  20 . Bands  13  are preferably elastomeric. It should be understood that one or more bands  13  may be employed as desired. The bands are visible in FIGS. 1,  2  and  10  but are not visible in other figures because they are compressed between sleeve  10  and the casing of the borehole. 
     FIG. 2 schematically illustrates a running tool  14  on which sleeve  10  is mounted for being run into the hole (not shown). Running tool  14  may be any one of several commercially available running tools capable of releasably retaining a sleeve to be run downhole. Running tool  14  does however include a schematically illustrated locating dog  16  unique to applications of the thin walled sleeve  10 . Locating dog  16  preferably is mounted on pin  18  which includes a torsional spring (not shown). Locating dog  16  follows an ID of a casing  20  until it reaches a milled window  22  whereat locating dog  16  automatically protrudes through window  22  while running tool  14  proceeds farther downhole. As locating dog  16  reaches a lower vee  24  of window  22 , it will orient itself both linearly and rotationally to window  22 . Because sleeve  10  is carefully oriented on running tool  14  at the surface to place locating dog  16  in a selected position relative to premachined window  12 , the action of locating dog  16  in vee  24  linearly and rotationally orients sleeve  10  to the milled window  22 . 
     Once sleeve  10  is oriented properly within the hole, running tool  14  is used to swage an uphole end  26 , a downhole end  28  or both  26  and  28  into contact with an ID  30  of casing  20 . One preferred method for swaging sleeve  10  is to employ an inflatable swaging device incorporated into the running tool. If both uphole end  26  and downhole end  28  are intended to be swaged then preferably two inflatable tools will be utilized simultaneously. FIG. 3 illustrates, schematically, sleeve  10  swaged at uphole end  26  and downhole end  28 . 
     Referring to FIG. 4, an alternate construction for new wells is disclosed wherein casing  32  is premachined with a window and includes recess  34  which is of sufficient dimension and configuration to receive a preinstalled sleeve  10  while providing an ID  36  of sleeve  10  which substantially equals ID  38  of casing  32 . By employing such casing  32  there is no restriction at the junction which might otherwise be problematic with respect to tools passing through the junction. As best illustrated in FIGS. 3 and 4, window  12  in sleeve  10  is preferably of smaller dimension than the window  22  (in FIG. 3) and  42  (in FIG. 4) so that a lateral liner being urged into a sealing engagement at the junction will seal against the ID  36  of sleeve  10  at window  12 . 
     Referring to FIG. 5, the depiction of FIG. 4 has been repeated but with a lateral liner installed. Thus, it is illustrated that flange  44  of lateral liner  46  is seated against the window  12  in sleeve  10  and is sealed thereto. It should be noted that at the interface (arrow  48 ) may be an elastomeric sealing material such as polyurethane or a metal sealing material such as bronze or steel. It should also be noted that it is possible to machine the premachined window  12  slightly smaller than liner  46  to provide an interference fit with the liner  10 . Because of the proximity of the sleeve to the liner in the area of the premachined window, sand and other particulate matter from the area of the junction  50  is substantially excluded from the wellbore system. This can be by one of bridging or sealing depending upon the tightness of the liner against the sleeve. 
     Referring to FIGS. 6-13, a sequential illustration of one embodiment for installing the sand device is illustrated. In FIG. 6, casing  20  is illustrated with a whipstock  52  therein oriented and maintained in place by anchor  54 . In FIG. 7, a drill string  56  is illustrated being introduced to the downhole environment just prior to contact with whipstock  52 . Referring to FIG. 8, a milled window  22  and lateral borehole  58  are illustrated. Referring to FIG. 9, the whipstock  52  has been removed from the wellbore leaving anchor  54  in place. It should be noted that anchor  54  is not required for installation of the sand exclusion device described herein but could be used if desired as a locating device. Referring to FIG. 10, a running tool  14  as described hereinabove, has been introduced to the downhole environment and into the vicinity of lateral borehole  58 . Dog  16  orients linearly and rotationally to milled window  22 . Once dog  16  has landed in vee  24 , as described above, the sleeve  10  is swaged with inflatable packer  60  which is illustrated in FIG.  11 . Referring to FIG. 12, the swaged sleeve  10  is left in position within the wellbore and anchored to casing  20  with window  12  oriented linearly and rotationally to borehole  58 . FIG. 13 illustrates a lateral liner  60  installed with flange  62  firmly seated against sleeve  10  and creating a seal thereagainst with either an elastomeric sealant such as polyurethane, metal-to-metal seal or other suitable seal. 
     The above discussed method for orienting rotationally and linearly using dog  16 , while a preferred embodiment, is but one embodiment. Another preferred embodiment referring to FIGS. 14 and 15 is to stab into anchor  54  with a running tool  80  having an orientation anchor  82  so that sleeve  10  is orientable to the milled window (not shown in subject figure) based upon the original whipstock anchor  54  and not the vee  24  of the window. The orientation anchor  82  further seals the downhole end and thus removes the need to swage the downhole end of sleeve  10 . The uphole end therefore is the only end needing swaging. FIG. 15 illustrates the uphole end swaged as has been previously described herein. 
     In another embodiment referring to FIG. 16, a schematic illustration carrying identical numerals for identical components is provided for understanding of another preferred arrangement where the sand exclusion sleeve  10  is employed in connection with a hook hanger liner  70  having hook  72  to engage with vee  24 . Although a flange  44  is not available in this embodiment, an interference fit between liner  70  and sleeve  10  is nevertheless crated which causes the bridging of particulates and thus their exclusion from the junction. 
     It should be noted that while the foregoing method for creating a sand excluding junction is effective, it is only necessary to place the sleeve  10  at a desired location, and run a liner through the premachined winds and into close enough proximity therewith to facilitate bridging of particulate matter. Swaging the sleeve in place is a preferred operation as well. Milling of a window in the primary casing and drilling a lateral borehole may have been accomplished as part of an earlier operation. 
     While preferred embodiments of the invention have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustration and not limitation.