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This is a continuation of Application Ser. No. 09/240,370, filed Jan. 29, 1999, abandoned such prior application being incorporated by reference herein in its entirety. 
     RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application Ser. No. 60/073,083, filed Jan. 30, 1998. 
     This application is related to copending U.S. patent application Ser. No. 09/240,290, filed Jan. 29, 1999, entitled “Method and Apparatus for One-Trip Insertion and Retrieval of a Tool and Auxiliary Device”, now U.S. Pat. No. 6,308,782. 
    
    
     TECHNICAL FIELD OF THE INVENTION 
     This invention relates in general to equipment for use with a well having a vertical bore and at least one lateral bore and, more particularly, to a method and apparatus for running into the well two tubing strings which respectively extend to the vertical bore and the lateral bore. 
     BACKGROUND OF THE INVENTION 
     A well for the production of hydrocarbons will have a vertical bore, and often has at least one lateral bore that communicates with the vertical bore through a window. It is possible to simultaneously produce hydrocarbons from both the vertical bore and lateral bore, by running a pair of tubing strings into the well, such that one tubing string is disposed in and effects production from the vertical bore, and the other tubing string is disposed in and effects production from the lateral bore. Although dual tubing string equipment has been developed for this purpose, and has been generally adequate in use, it has not been entirely satisfactory in all respects. 
     More specifically, each of the two tubing strings can typically have at the outer end thereof a seal assembly, which includes a tube with one or more annular seals therearound. The seals may be damaged as the tubing string is inserted into the well. For example, as the seal assembly is run into the well, it may initially be coupled by shear pins to a locator. The locator is rotationally oriented when it reaches the region of the window, after which the pins are sheared in order to permit the seal assembly to continue moving without the locator. However, the remnants of the shear pins may engage and damage the seals. As another example, the window in the vertical casing may have jagged edges, and the jagged edges may tear the seals if they engage the seal assembly as it is routed from the main bore into the lateral bore. 
     A further problem is that the tubing string for the vertical bore is normally routed past the window through a passageway having a centerline that is radially offset from the centerline of the vertical bore, but may then need to be moved back toward the centerline of the vertical bore. For efficiency, the diameters of the two tubing strings are usually made as large as possible relative to the inside diameter of the vertical casing. As a result, there has traditionally been no satisfactory way to provide additional structure which would fit within the limited transverse space available around the tubing strings, and which could satisfactorily guide the tubing string gradually back toward the centerline of the vertical bore. 
     SUMMARY OF THE INVENTION 
     From the foregoing, it may be appreciated that a need has arisen for a method and apparatus for facilitating the use of dual tubing strings in a well, so as to avoid damage to seals of a seal assembly during insertion of the seal assembly, and so as to guide a tubing string past or through a window opening. According to the present invention, a method and apparatus are provided to address this need. 
     One form of the present invention involves: supporting a protective sleeve for axial movement relative to a seal section between a first position in which an annular seal around the seal member is disposed within the protective sleeve, and a second position in which the annular seal is axially spaced from the protective sleeve; inserting a tubing string into the well with the seal section thereon and the protective sleeve in its first position; and thereafter effecting movement of the protective sleeve from the first position to the second position. 
     Another form of the present invention involves: an elongate tubing string which can be removably inserted into a well in a lengthwise direction; an auxiliary part supported for upward axial movement along the tubing string away from an initial position; and a releasable coupling arrangement having a coupling state in which the coupling arrangement prevents upward movement of the auxiliary part away from the initial position relative to the tubing string, and having a release state in which the coupling arrangement permits the auxiliary part to move upwardly away from the initial position relative to the tubing string. 
     Yet another form of the present invention involves: a window assembly having an arrangement for supporting the window assembly within a vertical well bore in the region of a window, the window assembly having first and second tubing passageways therein, and having below the second tubing passageway an upwardly facing deflection surface portion which is inclined to extend downwardly toward the window, the deflection surface portion having a cross-sectional shape which is concave. 
     Still another form of the present invention involves: a window assembly having an arrangement for supporting the window assembly within a vertical well bore in the region of a window, and having first and second tubing passageways therein, the first tubing passageway having a first portion which has a centerline radially offset from a vertical centerline of the vertical bore, the second tubing passageway having a portion which is axially aligned with the first portion of the first tubing passageway, and the first tubing passageway having an elongate second portion which is below the first portion thereof and which is inclined at a small angle with respect to the centerline of the vertical bore so that an upper end of the second portion is farther from the centerline of the vertical bore than a lower end thereof. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A better understanding of the present invention will be realized from the detailed description which follows, taken in conjunction with the accompanying drawings, in which: 
     FIG. 1 is a diagrammatic sectional side view of a well having therein equipment which embodies the present invention; 
     FIGS. 2A-2K are respective portions of a diagrammatic cutaway side view of a window assembly that is a component of the equipment shown in FIG. 1, and are collectively referred to herein as FIG. 2; 
     FIG. 3 is a diagrammatic sectional view taken along the line  3 — 3  in FIG. 2; 
     FIG. 4 is a diagrammatic sectional side view of a tube which is a component of the window assembly of FIG. 2, but before final machining has been performed on the tube; 
     FIG. 5 is a diagrammatic sectional side view of the tube of FIG. 4, after final machining has been performed thereon; 
     FIG. 6 is a diagrammatic sectional side taken along the line  6 — 6  in FIG. 5; 
     FIG. 7 is a diagrammatic perspective view of a deflector member which is a component of the window assembly of FIG. 2; 
     FIG. 8 is a diagrammatic sectional view taken along the line  8 — 8  in FIG. 2; 
     FIGS. 9A and 9B are respective portions of a diagrammatic cutaway side view of a locator, a protective sleeve and a seal assembly which are components of the equipment shown in FIG. 1, and are referred to collectively herein as FIG. 9; 
     FIG. 10 is a diagrammatic sectional view taken along the line  10 — 10  in FIG. 9; 
     FIG. 11 is a diagrammatic sectional view taken along the line  11 — 11  in FIG. 9; 
     FIG. 12 is a diagrammatic sectional view taken along the line  12 — 12  in FIG. 9; 
     FIG. 13 is a diagrammatic sectional view taken along the line  13 — 13  in FIG. 9; 
     FIG. 14 is an enlarged view of a portion of FIG. 9; 
     FIG. 15 is a diagrammatic cutaway view of a portion of the seal assembly and the locator of FIG. 9, and depicts a soft release coupling mechanism which is part of the locator or FIG. 9; 
     FIG. 16 is a diagrammatic cutaway view similar to FIG. 15, but showing the illustrated structure in a different operational position; 
     FIG. 17 is a diagrammatic cutaway view taken along the line  17 — 17  in FIG. 13; 
     FIGS. 18A-18C are respective portions of a diagrammatic cutaway side view of a protective sleeve, a seal assembly and a packer that are components of the equipment shown in FIG. 1, and are referred to collectively herein as FIG. 18; and 
     FIGS. 19A-19C are views similar to FIGS. 18A-18C but show the depicted structure in a different operational position, and are referred to collectively herein as FIG.  19 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The preferred embodiments of the present invention and its advantages are best understood by referring now in more detail to FIGS. 1-19 of the drawings, in which like numerals refer to like parts. 
     FIG. 1 is a diagrammatic cutaway side view of a well  10 . The disclosed well  10  is used for the production of hydrocarbons, but the present invention is also suitable for use with other types of wells. 
     The well  10  includes a vertical bore having a vertical casing  13  cemented therein. The casing  13  has a window  14  milled in one side thereof, at a location spaced above the lower end of the casing  13 . The well  10  also includes a lateral bore having a lateral casing  18  cemented therein, the lateral casing  18  communicating with the vertical casing  13  through the window  14 . 
     In the disclosed embodiment, the vertical casing  13  has an inside diameter of approximately eight to nine inches, and the lateral casing  18  has an inside diameter of approximately six to seven inches. However, it will be recognized that the present invention is not limited to casings of any particular size. Further, although the casing  13  in the primary bore is identified herein as a vertical casing, this is solely for purposes of convenience, and it will be recognized that the casing  13  could have an orientation other than vertical. 
     A retrievable seal bore packer  21  is releasably fixedly secured in the vertical casing  13 , at a location spaced below the window  14  and above the lower end of the casing  13 . Although a retrievable packer  21  is used in the disclosed embodiment, it will be recognized that a permanent packer could alternatively be used. A tailpipe  22  extends downwardly from the packer  21 , and has a perforated portion  23 . A further retrievable seal bore packer  26  is releasably fixedly secured in the lateral casing  18 , and has extending outwardly therefrom a tailpipe  27  with a perforated portion  28 . 
     The vertical casing  13  has therein a window assembly, which is designated generally with reference numeral  31 . The window assembly  31  is described in detail later, in association with FIG. 2, but is briefly described here for purposes of convenience. The window assembly  31  includes a latch mechanism  32 , which has a plurality of circumferentially distributed keys  33  that engage matching profiles provided in the walls of the casing  13 . The latch mechanism  32  serves to support the window assembly  31  at a desired vertical location within the vertical casing  13 , and also maintains the window assembly  31  in a predetermined rotational orientation with respect to the vertical casing  13  and the window  14  therein. 
     The window assembly  31  also includes a dual bore deflector  36 , which is secured to and extends upwardly from the latch mechanism  32 , and which has an upper end at  37 . The upper end  37  of the dual bore deflector  36  is a helical surface, only a portion of which is visible in FIG.  1 . 
     The window assembly  31  further includes a long string tube  41 , the upper end  42  of which is fixedly secured in the dual bore deflector  36  so that its centerline is radially offset from a vertical centerline of the vertical casing  13 . The long string tube  41  is coupled at its lower end to a further tube  121 . The tube  121  extends through a central opening in the latch mechanism  32 , and at its lower end is fixedly secured to and communicates with a seal assembly  43 . The seal assembly  43  sealingly engages a seal bore provided within the packer  21 . 
     Extending axially through the long string tube  41  is a passageway, which is not visible in FIG. 1, but which is discussed in more detail later. The passageway has a gradual incline or deviation with respect to a vertical reference, so that it extends downwardly and inwardly toward the vertical centerline of the vertical casing  13 . As will be discussed later, it is the passageway through the tube  41 , and not the tube  41  itself, which is inclined. However, since the passageway is not visible in FIG. 1, the tube  41  is shown with a gradual incline in FIG. 1 in order to diagrammatically indicate the inclination of the passageway through it. 
     The dual bore deflector  36  of the window assembly  31  has in one side thereof an opening or window  46 , which is vertically and rotationally aligned with the window  14  in the vertical casing  13 . The dual bore deflector  36  has an upwardly facing deflector surface  47 , which extends upwardly and inwardly from the lower edge of the window  46 , at a sharp incline with respect to a horizontal reference. This may alternatively be viewed as a gradual incline with respect to the centerline of the vertical casing  13 . 
     Two tubing strings  51  and  52  extend downwardly through the upper portion of the vertical casing  13 . A seal assembly  53  is fixedly secured to and communicates with the lower end of the tubing string  51 , and sealingly engages a seal bore  54  provided within the upper end of the dual bore deflector  36 . The seal bore  54  communicates with the upper end  42  of the long string tube  41 . The tubing string  52  extends past the deflector surface  47  and out into the lateral bore  18 . A seal assembly  56  is secured to and communicates with the outer end of the tubing string  52 . The seal assembly  56  sealingly engages a seal bore provided in the packer  26 . 
     A dual string hydraulic set retrievable packer  57  is releasably fixedly secured in the vertical casing  13 , at a location spaced above the window assembly  31 , and has the tubing strings  51  and  52  extending through it. The packer  57  resists both upward and downward movement of the tubing string  51 , and the tubing string  51  in turn resists upward movement of the window assembly  31 . 
     FIGS. 2A-2K, which are collectively referred to as FIG. 2, are respective portions of a diagrammatic cutaway side view of the window assembly  31  of FIG. 1, except that the seal assembly  43  at the lower end of the window assembly has been omitted. 
     With reference to FIG. 2, the dual bore deflector  36  of the window assembly  31  has at its upper end a cylindrical rotation sleeve  71 , the upper edge of which serves as the previously-mentioned helical surface  37 . The sleeve  71  has a short slot  72 , which extends axially downwardly from the lower end of the helical surface  37 . At the lower end of the sleeve  71  is a horizontal circular wall  76 , which has on the upper side thereof an upwardly facing flat surface which is normal to the centerline of the sleeve  71 . The wall  76  has two adjacent circular openings  77  and  78  extending through it. The openings  77  and  78  are offset in opposite directions from the centerline of the sleeve  71 , so that the centerline extends through a portion of the wall  76  which is disposed between the openings  77  and  78 . 
     The dual bore deflector  36  has, immediately below the wall  76 , two adjacent vertical cylindrical passageways  81  and  82 , which each open into the sleeve  71  through a respective one of the circular openings  77  and  78 . The passageways  81  and  82  are radially offset in opposite directions from the centerline of the sleeve  71 , and a thin wall  83  is provided between them. The dual bore deflector  36  also includes an elongate tube  86 , which has therethrough a cylindrical passageway  87  that is aligned with and communicates with the cylindrical passageway  81 . The lower end of the tube  86  is fixedly secured to a torque fitting  88 . FIG. 3 shows the cross-sectional shape of the torque fitting  88 . It will be noted in FIG. 3 that the torque fitting  88  has in one side thereof a vertically extending recess or groove  89  of rectangular cross-sectional shape, which is aligned with the passageway  82 . 
     Referring again to FIG. 2, it can be seen that the long string tube  41  has its upper end  42  fixedly secured to the torque fitting  88 , so that a cylindrical passageway  93  therethrough is aligned with and communicates with the cylindrical passageway  87  in the tube  86 . As evident from FIG. 2, the tube  41  extends generally vertically, but the cylindrical passageway  93  extends therethrough at a small angle with respect to a vertical reference, so that the centerline of the passageway  93  is slightly closer at its lower end than at its upper end to the vertical centerline of the window assembly. 
     FIGS. 4 through 6 provide additional information regarding the tube  41 . More specifically, FIG. 4 shows a tube  41 A, which is a part that will be subjected to additional machining in order to produce the final tube  41 . In FIG. 4, the tube  41 A is cylindrical, and has the cylindrical passageway  93  extending therethrough at an angle to the centerline of the cylindrical exterior surface of tube  41 A. FIG. 5 shows the final tube  41  which results after additional machining is performed on the tube  41 A. This additional machining includes machining an axially extending recess or groove  96  in one side of the upper end of the tube  41 , machining a further recess  97  in the other side of the lower end of the tube  41 , and machining a circumferential groove  98  around the lower portion the tube  41 . FIG. 6 shows the shape of the axial groove  96 , as well as the eccentricity of the passageway  93 . 
     With reference to FIGS. 2 and 7, a deflector member  106  is cylindrical, and has extending axially therethrough an eccentric cylindrical opening  107 , which receives the lower end of the long string tube  41 . The deflector member  106  has on one side thereof at its upper end the deflector surface  47  which, as shown in FIG. 7, is a concave groove that progressively tapers in width and depth in a downward direction. As shown in FIG. 7, the groove has respective portions which are of rectangular cross-sectional shape and trapezoidal cross-sectional shape. However, the groove could also have other concave cross-sectional shapes, such as a semicircular cross-sectional shape. 
     The cylindrical opening  107  in the deflector member  106  has at its lower end an enlarged portion  109 , which defines an axially downwardly facing shoulder  110 . a sleeve  111  is disposed within the enlarged portion  109 . A tube  112  has its upper end secured within the enlarged portion  109  by threads  113 , and has its lower end secured to the upper end of the latch  32  by threads  114 . The tube  112  has thereon an axially upwardly facing shoulder  117 , which engages the lower end of the sleeve  111  in order to hold the sleeve in place. The sleeve  111  has thereon an axially upwardly facing shoulder  118 . As shown in FIGS. 2 and 8, a split ring  119  is disposed within the groove  98  in the tube  41 , and also engages the shoulders  110  and  118 , in order to fixedly secure the deflector member  106 , the tube  112  and the latch  32  against vertical movement relative to the long string tube  41 . 
     With reference to FIG. 2, and as previously mentioned, the further tube  121  has its upper end fixedly secured to the lower end of the long string tube  41 , in particular by threads  122 . The tube  121  extends downwardly through tube  112  and the latch  32 , and projects outwardly beyond the lower end of the latch  32 . The tube  121  has threads  123  at its lower end, by means of which the seal assembly  43  (FIG. 1) is fixedly secured to the lower end of the tube  121 . 
     FIGS. 9A and 9B, which are collectively referred to as FIG. 9, are respective portions of a cutaway side view of a locator  126  and the seal assembly  56 , before they are run into the well. The locator  126  is also known as a soft release running tool, and is shown somewhat diagrammatically in FIG.  9 . The locator  126  has a cylindrical upper portion  127  and a cylindrical lower portion  128 , which are fixedly coupled to each other by a cylindrical tube  129  extending between them. 
     The upper portion  127  of the locator has two cylindrical openings  131  and  132  which extend vertically therethrough and which are radially offset in opposite directions from the centerline of the locator, the opening  132  being aligned with the tube  129 . The upper portion  127  has on the upper side thereof a scoop surface  133 , which is concave and inclined toward the cylindrical opening  131 . 
     The lower portion  128  of the locator has two cylindrical openings  136  and  137  which extend vertically therethrough and which are radially offset in opposite directions from the centerline of the locator, the opening  136  being aligned with the opening  131  in the upper portion  127 , and the opening  137  being aligned with the tube  129  and with the opening  132  in the upper portion. The lower portion  128  has on one side thereof a radially outwardly projecting lug  138 . 
     With reference to FIG. 9, the tubing string  52  is shown in broken lines, and the seal assembly  56  which is secured to the end of tubing string  52  is shown in a position where it extends through the opening  132 , the tube  129  and the opening  137 . FIG. 14 is an enlarged view of a portion of FIG. 9, showing some details of the seal assembly. 
     With reference to FIGS. 9 and 14, the seal assembly  56  includes an elongate cylindrical seal tube  141 , and includes a plurality of annular crimp seals  142 , which are disposed in respective circumferential grooves provided at axially spaced locations along the outer surface of the tube  141 . The tube  141  has near its lower end a circumferential groove  143 , and has near its upper end a further circumferential groove  144 . The seals  142  are all located between the grooves  143  and  144 . 
     In FIG. 9, a cylindrical protective sleeve  147  closely encircles the tube  141  and the seals  142 , with its upper end disposed above the groove  144 , and its lower end disposed above the groove  143  but lower than the lowermost seal  142 . The seals  142  are thus all disposed within the sleeve  147 . The purpose of the sleeve  147  is to protect all of the seals  142  as the seal assembly  56  is inserted into the well. The protective sleeve  147  has a relatively thin radial wall thickness. 
     As best seen in FIG. 14, a split ring  148  is provided in the groove  144  of the seal tube  141 , and is held against axial movement relative to the seal tube by the sidewalls of the groove  144 . The split ring  148  is shown in a relaxed position in FIG. 14, in which it projects partially outwardly beyond the surface of the seal tube. The split ring  148  can be compressed radially inwardly from the position shown in FIG. 14, to a compressed condition in which it is disposed entirely within the groove  144  and does not project radially outwardly beyond the surface of the seal tube. The split ring  148  has at its upper end an upwardly and outwardly facing bevel surface  149 . The protective sleeve  147  has an axially upwardly facing shoulder  152 . In the insertion configuration shown in FIG. 14, the split ring  148  can engage the shoulder  152  in order to prevent downward movement of the seal tube  141  relative to the protective sleeve  147 . This ensures that the seals  142  remain within and are protected by the protective sleeve  147  during insertion. 
     The seal tube  141  also has an upwardly facing annular bevel shoulder  153  which can engage a downwardly facing annular bevel shoulder  154  provided on the protective sleeve  147 , in order to prevent upward movement of the seal tube  141  relative to the protective sleeve  147  beyond the position shown in FIG.  14 . This ensures that the protective sleeve  147  does not slide downwardly and expose the seals  142  to damage. The protective sleeve  147  has at its upper end an upwardly and outwardly facing annular bevel shoulder  157  which can engage a downwardly and inwardly facing annular bevel shoulder  158  provided on the upper portion  127  of the locator  126 . Engagement of the shoulders  157  and  158  limits upward movement of the seal tube  141  and the protective sleeve  147  beyond the position shown in FIG. 14 with respect to the locator  126 . 
     Near its upper end, the protective sleeve  147  has a plurality of U-shaped slots which are circumferentially spaced and which each define a respective collet finger  161 . The collet fingers  161  are integrally secured at their upper ends to the protective sleeve  147 , and have lower ends  162  which are capable of limited radial movement through flexing of the collet fingers  161 . During insertion, the lower ends  162  of the collet fingers engage the outer side of the split ring  148 . The lower end of each collet finger has bevel surfaces  166 - 169  on both the inner and outer sides thereof, in order to allow the ends of the fingers to slide over other parts. A rib  172  may be provided on the protective sleeve  147 , so as to engage the bevel surfaces  166  and  169  on each collet finger in a manner which limits radially outward movement of the lower ends of the collet fingers. 
     The seal assembly  56 , as well as the protective sleeve  147 , are held against vertical movement with respect to the locator  126  by a soft release coupling mechanism, which is disposed within the lower portion  128  of the locator  126  but which, for clarity, has been omitted from FIG.  9 . One embodiment of this soft release coupling mechanism  176  is shown in FIGS. 15 and 16. FIGS. 15 and 16 show only selected portions of the lower portion  128 , which are pertinent to the locking mechanism. Further, the protective sleeve  147  has been omitted for clarity in FIGS. 15 and 16, and because the locking mechanism is suitable for use with the seal tube  141  even where the protective sleeve  147  is not present. 
     In FIGS. 15 and 16, two dogs  178  are supported within the lower portion  128  of the locator  126  for radial movement between a position engaging the groove  143  (FIG. 15) and a position spaced radially outwardly from the tube  141  (FIG.  16 ). The dogs  178  are urged radially outwardly by respective leaf springs  179 . Two control rods  181  are supported for axial movement relative to the lower portion  128  of the locator, between positions respectively shown in FIGS. 15 and 16. Each rod  181  has a lower end  182  which projects outwardly beyond the lower end of the locator in the position of FIG. 15, and which is flush with the lower side of the locator in the position of FIG.  16 . 
     Each control rod  181  is urged downwardly by a respective helical compression spring  183 . Each control rod  181  has thereon a cam surface  186 , which in the position of FIG. 15 holds a respective dog  178  in the radially inner position in which the dog engages the groove  143 , and which in the position of FIG. 16 permits the dog  178  to be moved radially outwardly by its spring  179  so that the dog is free of engagement with the tube  141 . Each control rod  181  is initially secured against axial movement relative to the lower portion  128  of the locator by a shear pin, one of which is shown diagrammatically at  187 . 
     In the embodiment of FIGS. 15 and 16, a catch or inner dog  191  is radially movably supported within each of the dogs  178 , and is urged radially inwardly with respect to the dog by a compression spring  192 . Thus, in the position of FIG. 16, the dogs  178  are spaced radially outwardly from the tube  141 , but the catches  191  are each urged radially inwardly into engagement with the tube. Each catch  191  has bevel surfaces  193  and  194  which permit the catches to ride over the seals  142  without damaging the seals. Further, each catch  191  has a downwardly facing surface  196  which can engage the upwardly facing side surface of groove  143 , in order to limit upward movement of the tube  141  relative to the locator  126 . 
     FIGS. 13 and 17 show a soft release coupling mechanism  197 , which is an alternative embodiment of the coupling mechanism  176 . The coupling mechanism  197  is similar to the coupling mechanism  176 , except as described below. In FIG. 17, the control rod  181  is shown with an opening  201 , which receives an end of the shear pin  187  (FIG.  15 ). The control rod  181  also includes an axial slot  202  which receives an end of a not-illustrated setscrew in the lower portion  128  of the locator, in order to prevent rotational movement of the control rod  181  and in order to limit axial movement thereof. The hole  201  and the slot  202  are present in the control rods  181  of FIGS. 15 and 16, but are not visible in FIGS. 15 and 16. 
     The coupling mechanism  197  of FIGS. 13 and 17 differs from the coupling mechanism  176  of FIGS. 15 and 16 primarily in that the dogs are configured differently. In particular, with reference to FIGS. 13 and 17, two dogs  206  each have a head engagable with the groove  143  in the seal tube  141 , and have a stem  207  which extends radially outwardly through an opening  205  provided in a wall of the lower portion  128  of the locator  126 . A snap ring  208  is provided near the outer end of each stem  207 , and a helical compression spring  211  extends between the snap ring  208  and the wall having the opening  205 , so as to urge the dog  206  radially outwardly. The outer end of the stem  207  engages the cam surface  186  on a respective one of the control rods  181 . 
     FIGS. 18A-18C, which are collectively referred to as FIG. 18, depict respective portions of a diagrammatic cutaway side view of the seal assembly  56  and the packer  26 . FIGS. 19A-19C, which are collectively referred to as FIG. 19, are views corresponding to FIGS. 18A-18C, but show a different operational position. 
     With reference to FIGS. 18 and 19, the packer  26  has therein a cylindrical seal bore  221 . A tubular cylindrical extension  222  is fixedly secured to an end of the packer  26  nearest the vertical casing  13 , and extends away from the packer  26  toward the vertical casing. A cylindrical release surface  223  of reduced diameter is provided on the extension  222 , near the end of the extension remote from the packer  26 . An annular bevel shoulder  226  is provided at the end of the release surface  223  remote from the packer  26 , the release surface  223  being engagable with a shoulder  227  provided on the protective sleeve  147 . 
     The operation of the disclosed embodiments will now be briefly described. With reference to FIG. 1, it is assumed that the vertical and lateral bores of the well  10  have been drilled, and that the casings  13  and  18  have been cemented in place. The seal bore packer  26  is then installed in the lateral casing  18 , and the seal bore packer  21  is installed in the vertical casing  13  below the window  14 . 
     The entire window assembly  31  is then run into the vertical casing  13 . The window assembly  31  is adjusted vertically and rotationally until the keys  33  engage the mating profiles provided in the walls of the vertical casing  13 . Each of the keys  33  of the latch  32  has a unique profile, so that the window assembly  31  can have only a single angular orientation, in which the window  46  therein is necessary aligned with the window  14  in the casing  13 . When the keys  33  are engaging the mating profiles in the casing  13 , the seal assembly  43  will be sealing engaging the seal bore and the packer  21 , as shown in FIG.  1 . 
     Then, the dual tubing strings  51  and  52  are simultaneously run into the vertical casing  13 . The seal assembly  53  on the tubing string  51  will be vertically higher than the seal assembly  56  on the tubing string  52 . For example, the distance separating them could be approximately 500 feet, in which case the packer  26  in the lateral casing  18  would be approximately 500 feet away from the vertical casing  13 . As the dual tubing strings  51  and  52  are run into the well with the seal assemblies  53  and  56  in this offset configuration, the dual string hydraulic set retrievable packer  57  is run in on the strings, at a location above the seal assembly  53 . The soft release coupling mechanism  197  (FIGS. 13 and 17) releasably secures the locator  126  with respect to the seal assembly  56  and the protective sleeve  147 , as shown in FIGS. 9 and 14. 
     When the locator  126  reaches the window assembly  31 , it will enter the rotation sleeve  71  provided at the upper end of the window assembly. If the lug  138  is rotationally aligned with the slot  72 , the locator  126  will move straight downwardly and the lug  138  will slide into the slot  72 . Typically, however, this rotational alignment will not initially exist, in which case the lug  138  will engage and slide along the helical surface  37  in response to further downward movement of the locator  126 , and will rotate the locator  126  until the lug  138  is aligned with and slides into the slot  72 . 
     As the lug  138  moves into the slot  72 , the lower end of the locator will approach the wall  76  at the lower end of the sleeve  71 . As this occurs, the wall  76  will engage the lower ends  182  of the two control rods  181  and push them upwardly with respect to the locator  126 , thereby shearing the shear pins  187  which were resisting such upward movement of the control rods  181 . As the control rods  181  move upwardly with respect to the locator  126  against the urging of the springs  183 , the cam surfaces  186  thereon shift so as to allow the springs  211  to move the dogs  206  radially outwardly, out of engagement with the groove  143  provided in the seal tube  141 . This permits the seal tube  141  to move downwardly relative to the locator  126 , away from the insertion position of the seal assembly  56  which is shown in FIG.  9 . Due to the engagement between the split ring  148  and the shoulder  152  on the protective sleeve  147 , the protective sleeve  147  continues downwardly with the seal assembly  56 . The springs  211  ensure that the dogs  206  do not engage the seal assembly  56  as it moves downwardly. This is particularly significant when the protective sleeve  147  is not being used, because it ensures that the dogs  206  do not engage and damage the seals  142  on the tube  141 . 
     When the lowermost end of the seal assembly  56  reaches the deflector surface  47  (FIGS.  1  and  2 ), the lower end is deflected laterally outwardly into the lateral casing  18 . The concave shape of the deflector surface  47  will help to keep the seal assembly centered as it is deflected toward the lateral casing  18 . This is particularly significant if the protective sleeve  147  is not being used, because it helps reduce the likelihood that the seal assembly will engage the edges of the window  14 , which can inflict damage to the seals  142 . Where the protective sleeve  147  is being used, it will protect the seals  142  from jagged edges of the window  14 , even if the seal assembly  56  does happen to engage the edges of the window  14 . Thereafter, as the tubing strings  51  and  52  continue to be run into the well, the seal assembly  56  and the protective sleeve  147  will move further outwardly into the lateral bore  18 . 
     With reference to FIGS. 18 and 19, the seal assembly  56  and protective sleeve  147  will eventually enter the tubular extension  222  on the packer  26  in the lateral casing  18 , until the shoulder  227  on the protective sleeve engages the shoulder  226  on the extension  222 . The engagement of the shoulders  226  and  227  will prevent further movement of the protective sleeve  147  into the extension  222 . At this point, as shown in FIG. 18, the ends  182  of the collet fingers  181  on the protective sleeve  147  are disposed within the cylindrical release surface  223  on the extension  222 . The diameter of the cylindrical release surface  223  is selected so that it presses the ends  182  of the collet fingers  181  radially inwardly, and they in turn compress the split ring  148  sufficiently to release the engagement between the split ring  148  and the shoulder  152  (FIG. 14) on the protective sleeve  147 . This permits the seal assembly  56  to continue to move ahead into the packer  26  while the protective sleeve remains in the extension  222 , as shown in FIG.  19 . The seals  142  on the seal assembly  56  sealingly engage the seal bore  221  provided in the packer  26 , as shown in FIG.  19 . 
     As the seal assembly  56  enters the packer  26 , the seal assembly  53  (FIG. 1) on the tubing string  51  approaches the upper end of the locater  126 . The scoop surface  133  (FIG. 9) on the upper end of the locator  126  guides the seal assembly  53  toward the opening  131 , so that the seal assembly  53  enters the opening  131 , passes through the opening  136 , and enters the seal bore  54  provided in the upper end of the window assembly  31 . Thus, the seal assembly  56  seals within the packer  26  substantially simultaneously with the seal assembly  53  sealing within the seal bore  54 , as shown in FIG.  1 . Then, while applying weight to the tubing strings  51  and  52 , the dual string hydraulic set retrievable packer  57  is actuated. Thereafter, through the tubing string  51 , the packer  57  helps prevent upward movement of the window assembly  31 . The window assembly  31 , in conjunction with the seals at  21 ,  26 ,  54  and  57 , provides a seal junction which has been rated at a pressure of at least 5,000 psi. 
     In order to remove the tubing strings  51  and  52 , the packer  57  is released, and the tubing strings  51  and  52  are run upwardly. This extracts the seal assembly  53  from the upper end of the window assembly  31 . Further, movement of the tubing string  52  pulls the seal assembly  56  out of the seal bore  221  (FIG. 19) of the packer  26 , and back into the protective sleeve  147  disposed within the extension  222 , as shown in FIG.  18 . At this point, the shoulder  153  on the seal assembly  56  engages the shoulder  154  on the protective sleeve  147 . As the tubing string  52  is further run upwardly, the protective sleeve  147  will be pulled along with the seal assembly  56 . 
     When the seal assembly  56  and the protective sleeve  147  reach and enter the window assembly  31 , they will move upwardly until they enter the locator  126  and reach the position shown in FIGS. 9 and 14. In this position, the shoulder  157  at the upper end of the protective sleeve  147  engages the shoulder  158  on the locator. This prevents further upward movement of the protective sleeve  147  relative to the locator  126 . Therefore, as the tubing string  52  continues to be run upwardly, it pulls the seal assembly  56  upwardly, which in turn pulls the protective sleeve  147  upwardly by virtue of the engagement between shoulders  153  and  154 , and the protective sleeve  147  in turn pulls the locator  126  upwardly, by virtue of the engagement between shoulders  157  and  158 . 
     The soft release coupling mechanism  197  which is disclosed in FIGS. 13 and 17 operates in substantially the same manner described above for the coupling mechanism  176 . Accordingly, the operation of the coupling mechanism  197  is not described here in detail. 
     An optional variation is that a not-illustrated coupling arrangement could be provided between the seal tube  141  and the protective sleeve  147 , in order to positively lock these parts together after they reach the relative position shown in FIG.  19 . Then, as the seal tube  141  was withdrawn from the well, the protective tube  147  would be prevented from moving back down over the seals  142 . Although this would expose the seals to potential damage during withdrawal, the seals would normally be replaced before the seal tube  141  was used again, and so any damage to them during withdrawal would not be significant. 
     Although multiple embodiments have been illustrated and described, it will be understood that various changes, substitutions and alterations can be made therein, including the rearrangement and reversal of parts, without departing from the scope of the present invention, as defined by the following claims.

Summary:
A well has a vertical casing with a window, and a lateral wellbore which communicates with the window, and which may have a casing or liner. A window assembly aligned with the window has respective passageways for first and second tubing strings, and has a concave surface for deflecting the first tubing string out into the lateral wellbore. The passageway for the second tubing string has a portion which is inclined at a very small angle with respect to a vertical centerline of the vertical casing. As the first tubing string is run into the vertical casing, a rotational locator is releasably coupled thereto by a soft release coupling mechanism. After the locator effects rotational orientation, the coupling mechanism is released and then permits the first tubing string to move therepast without damage. A seal assembly on the first tubing string is covered by a protective sleeve as it is inserted into the well, and exits the protective sleeve after entering the lateral wellbore.