Patent Publication Number: US-7219746-B2

Title: Apparatus and method for installing a branch junction from a main well

Description:
This application is a continuation of International Application PCT/IB98/01394, filed Sep. 8, 1998, which is a continuation of U.S. application Ser. No. 09/148,667, filed Sep. 4, 1998, now abandoned, which is a continuation-in-part of U.S. application No. 08/925,971, filed Sep. 9, 1997, now U.S. Pat. No. 5,979,560. 
    
    
     TECHNICAL FIELD 
     This invention relates in general to the construction of a lateral branch for a primary well and particularly to a junction member which sealingly connects the main borehole casing and the branch liner casing. 
     BACKGROUND ART 
     In recent years, well construction technology has yielded substantial increases in well productivity with the spread of horizontal drilling for the bottom end section of the well. Unfortunately horizontal drilled wells provide limited zonal isolation and do not always permit good completion practices regarding the independent production of different production zones. Research efforts are now concentrating on the possibility of drilling lateral branches either inclined or horizontal from a primary well to enhance further reservoir productivity. Also lateral branches open the potential of tapping several smaller size reservoirs spread around from one single well without the need to sidetrack and redrill the well when moving the production from one production zone to the next. The challenge with multilateral completion is to install a junction apparatus having adequate internal and external pressure capability without relying only on the strength of the local rock formations. 
     Prior art junction apparatus designs are based on a low angle side branch casing connected to a window on the main borehole casing. Prior proposals generally require in situ milling of a window or a section in the main borehole casing. Milling steel casing downhole is a difficult task. Also, while there are numerous proposals for sealing the branch liner casing to the window, improvements are needed. One design deforms a complete junction assembly to offer a diameter equal or less than the diameter of the main borehole casing and expanding it in situ to the full cylindrical shape. In that design, the junction assembly may be elastomeric or memory metal. WO 97/06345 illustrates such a design. The junction assembly is expanded within an enlarged section of the well. 
     Due to the side window based connecting link between the main borehole casing and the branch outlet, all these configurations offer poor internal pressure capacity and even more limited collapse capability when the junction is located in unconsolidated or weakly consolidated formations. The poor internal pressure capability and resistance to collapsing exists even when they are fully cemented since cement does not work well in traction. It is therefore highly desirable to have a junction apparatus offering good internal pressure and collapse capability to permit a wide freedom in the location of lateral junction independent from the strength of the cementing job and/or surrounding rock formation. 
     DISCLOSURE OF INVENTION 
     In this invention, a casing junction member or apparatus is provided with an upper end which connects into the main casing. A lower main end connects to the lower main casing extending into the well. The junction apparatus has a lateral branch section which is at an angle relative to the longitudinal axis of the main section. 
     The lateral and lower enlarged sections join each other at a junction which has a lower perimeter portion that is generally in the shape of parabola. In one embodiment, a stiffening plate or rib is located at this junction. The plate is located in a plane of the perimeter portion and is joined between the lateral and lower enlarged sections. 
     Preferably the junction apparatus has an upper enlarged section which is conical and joins the upper end section of the main section. The conical upper enlarged section diverges in a downward direction. A conical lower enlarged section joins the lower end of the upper enlarged section and extends downward to the lower end section of the main section. The conical lower enlarged section diverges in a downward direction. A generally conical lateral section joins the upper enlarged section also and extends downward to the lower end section of the lateral section. The conical lateral section also converges in a downward direction. The conical lower enlarged and lateral sections are truncated. Only their inner sides join each other at the junction. 
     In the preferred method of installation, the junction apparatus is of steel and is plastically deformable from a collapsed position to a set position. In the collapsed position, the junction apparatus has a diameter no greater than the main casing collar. The main bore is drilled and underreamed at an intersection depth. The junction apparatus is connected to the main casing and lowered into the well with the main casing. After reaching the underreamed section, fluid pressure is applied to the main casing to cause the junction apparatus to move to the set configuration. Then the main casing is cemented in place, with the cement also flowing around the junction apparatus in the underreamed section of the borehole. Subsequently, the lateral bore is drilled and a lateral casing liner installed and sealed to the lateral section of the junction member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side elevational view illustrating a junction apparatus connected into a main string of casing and shown in a collapsed position. 
         FIG. 2  is a side elevational view similar to  FIG. 1 , but showing the junction apparatus expanded to a set position. 
         FIG. 3  is a sectional view of the junction apparatus of  FIG. 1 , taken along the line  3 — 3  of  FIG. 1 . 
         FIG. 4  is a sectional view similar to  FIG. 3 , but taken along the line  4 — 4  of  FIG. 2  to show the apparatus in the set position. 
         FIG. 5  is a sectional view of the junction apparatus of  FIG. 1 , taken along the line  5 — 5  of  FIG. 1 . 
         FIG. 6  is a sectional view similar to  FIG. 5 , but taken along the line  6 — 6  of  FIG. 2  to show the apparatus in the set position. 
         FIG. 7  is a sectional view of the junction apparatus of  FIG. 1 , taken along the line  7 — 7  of  FIG. 1 . 
         FIG. 8  is a sectional view similar to  FIG. 7 , but taken along the line  8 — 8  of  FIG. 2  to show the apparatus in the set position. 
         FIG. 9  is a sectional view of the junction apparatus of  FIG. 1 , taken along the line  9 — 9  of  FIG. 1 . 
         FIG. 10  is a sectional view similar to  FIG. 9 , but taken along the line  10 — 10  of  FIG. 2  to show the junction apparatus in the set position. 
         FIG. 11  is a sectional view of the junction apparatus of  FIG. 1 , taken along the line  11 — 11  of  FIG. 1 . 
         FIG. 12  is a view similar to  FIG. 11 , but taken along the line  12 — 12  of  FIG. 2  to show the junction apparatus in the set position. 
         FIG. 13  is a sectional view of the junction apparatus of  FIG. 1 , taken along the line  13 — 13  of  FIG. 1 . 
         FIG. 14  is a sectional view similar to  FIG. 13 , but taken along the line  14 — 14  of  FIG. 2  to show the junction apparatus in the set position. 
         FIG. 15  is a sectional view of the junction apparatus of  FIG. 1 , taken along the line  15 — 15  of  FIG. 1 . 
         FIG. 16  is a sectional view similar to  FIG. 15 , but taken along the line  16 — 16  of  FIG. 2  to show the junction apparatus in the set position. 
         FIG. 17  is an enlarged vertical sectional view of the junction apparatus of  FIG. 1 , shown in the set position. 
         FIG. 18  is a perspective view of the junction apparatus of  FIG. 1 . 
         FIG. 19  is a sectional view of the junction apparatus of  FIG. 1 , taken along the line  19 — 19  of  FIG. 18 . 
         FIG. 20  is a sectional view similar to  FIG. 11 , but showing an alternate embodiment of the junction apparatus. 
         FIG. 21  is a side view of another embodiment of a junction apparatus constructed in accordance of this invention and shown in the collapsed position. 
         FIG. 22  is a side view of the junction apparatus of  FIG. 21 , shown in the set position. 
         FIG. 23  is an enlarged side view of a segmented rod employed with the junction apparatus of  FIG. 21 . 
         FIG. 24  is a sectional view of the junction apparatus of  FIG. 21 , taken along the line  24 — 24  of  FIG. 21 . 
         FIG. 25  is a sectional view of the junction apparatus of  FIG. 21 , taken along the line  25 — 25  of  FIG. 22 . 
         FIG. 26  is a sectional view of the junction apparatus of  FIG. 21 , taken along the line  26 — 26  of  FIG. 21 . 
         FIG. 27  is a sectional view of the junction apparatus of  FIG. 21 , taken along the line  27 — 27  of  FIG. 22 . 
         FIG. 28  is a sectional view of the junction apparatus of  FIG. 21 , taken along the line  28 — 28  of  FIG. 21 . 
         FIG. 29  is a sectional view of the junction apparatus of  FIG. 21 , taken along the line  29 — 29  of  FIG. 22 . 
         FIG. 30  is a sectional view of the junction apparatus of  FIG. 21 , taken along the line  30 — 30  of  FIG. 21 . 
         FIG. 31  is a sectional view of the junction apparatus of  FIG. 21 , taken along the line  31 — 31  of  FIG. 22 . 
         FIG. 32  is a sectional view of the junction apparatus of  FIG. 21 , taken along the line  32 — 32  of  FIG. 21 . 
         FIG. 33  is a sectional view of the junction apparatus of  FIG. 21 , taken along the line  33 — 33  of  FIG. 22 . 
         FIG. 34  is a sectional view of the junction apparatus of  FIG. 21 , taken along the line  34 — 34  of  FIG. 21 . 
         FIG. 35  is a sectional view of the junction apparatus of  FIG. 21 , taken along the line  35 — 35  of  FIG. 22 . 
         FIG. 36  is a sectional view of the junction apparatus of  FIG. 21 , taken along the line  36 — 36  of  FIG. 21 . 
         FIG. 37  is a sectional view of the junction apparatus of  FIG. 21 , taken along the line  37 — 37  of  FIG. 22 . 
         FIG. 38  is a sectional view of the junction apparatus of  FIG. 21  within a folding machine in preparation for being folded, and taken along the line  38 — 38  of  FIG. 40 . 
         FIG. 39  is a sectional view showing the junction apparatus and folding machine of  FIG. 38  after folding has occurred. 
         FIG. 40  is a side view of the folding machine of  FIG. 38 , shown prior to folding. 
         FIG. 41  is a sectional view showing the junction apparatus of  FIG. 21  positioned in a collapsing machine for collapsing from the folded position of  FIG. 21 , and taken along the line  41 — 41  of  FIG. 43 . 
         FIG. 42  is a sectional view illustrating the junction apparatus and the collapsing machine of  FIG. 40  moved to the collapsed position. 
         FIG. 43  is a side view of the collapsing machine of  FIG. 41 , shown prior to collapsing the junction apparatus. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Referring to  FIG. 1 , a main bore  11  has been drilled. At a desired intersection depth, an enlarged diameter section  13  is created by underreaming. A string of main casing  15  has been run into main bore  11  through enlarged section  13 . Enlarged section  13  is created at a desired intersection depth to start a lateral branch bore. 
     A first embodiment of a junction member  17  is connected into main casing  15  at the surface and lowered into enlarged section  13  while running casing  15 . Junction member  17  is in a collapsed position while running in, as shown in  FIG. 1 . Subsequently, it will be expanded by internal fluid pressure to the set position in  FIG. 2 . Junction member  17  is of steel of a high elongation grade which is capable of being plastically deformed into the collapsed position and expanded under fluid pressure to the set position. 
     Junction member  17  includes an upper end section  19  which is secured to a casing collar  20  of main casing  15 . Upper end section  19  is a cylindrical section which is coaxial with a main bore axis  23 . An upper enlarged section  21  is joined to upper end section  19 , preferably by welding. Upper enlarged section  21  is a conical member which diverges or increases in diameter in a downward direction, as can be seen by comparing  FIGS. 6 and 8  and viewing  FIGS. 18 and 19 . Upper enlarged section  21  is a right circular cone generated about an axis  22 . Cone axis  22  intersects and is inclined at a slight angle relative to main bore axis  23 . Similarly, a lateral branch axis  25  is inclined slightly and intersects main bore axis  23  at the same point of intersection as cone axis  22 . Cone axis  22  is one-half the angle of intersection of lateral axis  25 . The angles of intersections may differ from well to well, and in the embodiment shown, lateral axis  25  is at a 10 deg. angle relative to main axis  23 , while cone axis  22  is at a 5 deg. angle. The upper section of the lateral branch wellbore (not shown) will be drilled along lateral axis  25 . 
     A lower enlarged conical section  27  joins the lower end of upper enlarged section  21 , such as by welding. Lower enlarged conical section  27  is also a right circular cone that is slightly tilted relative to main axis  23 . When viewed in the elevational view of  FIG. 2 , the left sides of conical upper enlarged section  21  and lower enlarged section  27  appear flush with each other and in a straight line with a side of main casing  15 . Lower enlarged conical section  27  diverges in a downward direction, having a decreasing diameter as shown in  FIGS. 18 and 19 . 
     A lateral conical section  29 , identical to lower enlarged conical section  27 , also joins upper enlarged section  21 , such as by welding. Lateral conical section  29  is also a section of right circular cone which is tilted relative to main axis  23  and lateral axis  25 . When viewed in the elevational view of  FIG. 2 , a right side portion of lateral conical section  29  appears flush with a right side section of upper enlarged section  21  and parallel to lateral axis  25 . Lateral conical section  29  also diverges in a downward direction, having a decreasing diameter as shown in  FIG. 18 . 
     Referring to  FIGS. 17–19 , inner side portions of lower enlarged conical section  27  and lateral conical section  29  are cut or truncated to form a junction of the two sections. This junction has a lower perimeter portion  31  that is in a configuration of a parabola. Lower perimeter portion  31  comprises mating edges of lower enlarged and lateral conical section  27 ,  29 , the edges being abuttable with each other. Lower perimeter portion  31  is contained in a plane that contains cone axis  22 . 
     In the first embodiment, a stiffening plate or rib  33  is sandwiched between the conical lower enlarged and lateral sections  27 ,  29  at lower perimeter portion  31 . Stiffening plate  33  is also in the general configuration of a parabola. In the embodiment shown, it has an inner edge  35  that is in the configuration of a parabola. Outer edge  37  is also in the configuration of a parabola. However, the parabola of inner edge  35  is not as steep, with edges  35 ,  37  converging toward each other in an upward direction. This results in legs  38  for stiffening plate  33  that decrease in width in an upward direction until reaching a minimum width at upper ends  39 . Upper ends  39  of stiffening plate  33  are located at the lower end of upper enlarged section  21 . The width between inner edge  35  and outer edge  37  is the smallest at this point. The maximum width of plate  33  is at its lowest point. 
     Stiffening plate  33  is welded to lower enlarged and lateral conical members  27 ,  29  at junction  31 . In this position, inner edge  35  is located above lower perimeter portion  31 , while outer edge  27  is located below lower perimeter portion  31 . Stiffening plate  33  is located in a plane of lower perimeter portion  31 . Conical axis  22  passes through a plane containing stiffening plate  33 . 
     The purpose of stiffening plate  33  is to reinforce the junction between lower enlarged and lateral conical sections  27 ,  29 . Referring to  FIGS. 10 and 12 , internal pressure within junction member  17  will tend to cause junction member  17  to assume a circular configuration. The circular configuration is desired at the lower edge of upper enlarged section  21  as shown in  FIG. 10 . However, the junction of the lower enlarged and lateral conical sections  27 ,  29  with upper enlarged section  21  is not circular, as shown in  FIG. 12 . In  FIG. 12 , which is a section taken about halfway down the joined lower enlarged and lateral conical sections  27 ,  29 , the joined conical sections will have a cross-sectional configuration that is not circular. Rather, the distance  40  between outer sides of the lower enlarged and lateral conical sections  27 ,  29  perpendicular to a line extending between legs  38  is substantially greater than the distance between the two legs  38  of stiffening plate  33  at that point. The cross-section presents a general peanut shape, with the dotted lines in  FIG. 12  representing the full bore access to the lower ends of the main and lateral branches. Without stiffening plate  33 , internal pressure would tend to force the small dimension portion between legs  38  apart to the circular configuration as in  FIG. 10 . This would deform the junction and restrict the full bore access to both branches. Stiffening plate  33  prevents such occurrence at test pressure levels. 
     Referring again to  FIG. 2 , a cylindrical main section lower end  41  joins the lower end of lower enlarged conical section  27 , which is circular at that point. The main section lower end  41  is secured to the lower continuation of main casing  15  by a threaded collar. Lower end  41  is coaxial with main axis  23 . Similarly, cylindrical lateral end portion  43  joins the lower end of lateral conical section  29 , which is circular at that point. Lateral section  43  extends downward and provides a guide for drilling a lateral branch borehole (not shown) Lateral end section  43  is coaxial with lateral axis  25 . Stiffening plate  33  extends downward a short distance between main section lower end  41  and lateral section lower end  43 . 
     Junction member  17  if first constructed and tested in the set configuration, then will be formed in the collapsed configuration that is shown in  FIG. 1 . In the collapsed configuration, the overall diameter is substantially the same as the diameter of main casing  15  and no greater than the outer diameter of casing collar  20 . Referring to  FIG. 1  and  FIGS. 3 ,  5 ,  7 ,  9 ,  11 ,  13  and  15 , the collapsed configuration has a doubled back section  45  within upper enlarged section  21 . Doubled back section  45  increases in extent in a downward direction as shown by comparing  FIG. 5 ,  FIG. 7  and  FIG. 9 . 
     As shown in  FIG. 11 , lower enlarged conical section  27  remains generally undeflected. However, lateral conical section  29  is folded into the interior of lower enlarged conical section  27 . In the position shown, two loops  47  are employed to accommodate the full extent. Note that legs  38  will not be in a common plane in the collapsed position. In  FIG. 13 , an inner side  49  of main lower end  41  is doubled back into an outer side section of main lower end  41 , presenting a crescent shape. 
     A plurality of axially extending channels  51  are formed in the upper section of lateral section lower end  43 . Stiffening plate  33  is bent into a concave configuration at its lower section. Referring to  FIG. 15 , more vertical channels  51  will be present on lateral section lower end  43 , and they will be symmetrical to form a corrugated configuration for lateral section lower end  43 . The crescent configuration remains for main section lower end  41  for a short distance downward where it again returns to a cylindrical configuration as shown in  FIG. 1 . In the collapsed position, lateral end section  43  extends downward generally parallel with main axis  23 . 
     In operation, main bore  11  will be drilled, then one or several enlarged sections  13  are created. The operator inserts one or several junction members  17  into main casing  15  while in the collapsed position and runs main casing  15 . Main casing  15  will have a conventional cementing shoe (not shown) on its lower end. The cement shoe will be of a type which prevents downward flow until a dart or ball is dropped to shift a valve member. Lateral end  43  has a plug  52  which seals both while lateral end  43  is in the corrugated shape and in the set position. 
     When junction member  17  reaches enlarged bore section  13 , the operator will apply pressure to casing  15 . The internal pressure causes junction member  17  to plastically deform from the collapsed position shown in  FIG. 1  to the set position shown in  FIG. 2 . The operator then drops a ball or dart to shift cement shoe to a position wherein fluid may be pumped downward in main casing  15 . The operator then pumps cement down main casing  15 , which flows out the cement shoe and back up an annulus in main bore  11  surrounding main casing  15 . The cement will flow through the enlarged section  13  and up toward the surface. Drilling fluid will be pumped down behind the cement to flush main bore casing  15  of cement. A cement wiper plug (not shown) separates the cement from the drilling fluid, the plug moving downward through junction member  17  to the lower end of main bore casing  15 . 
     The operator may then perform further drilling through main casing  15 . When the operator wishes to drill the lateral branch, he will either install a whipstock in the main borehole or use a kick-out device to deflect the drill bit over into the lateral section. The operator drills out plug  52  and continues drilling at lateral angle  25  for a selected distance into the earth formation. Once a desired depth has been reached for the lateral branch, the operator will run a liner casing (not shown). The liner casing will have a conventional hanger and seal for hanging and sealing within lateral section lower end  43 . The lateral liner casing will be cemented in a conventional manner. 
       FIG. 20  illustrates an alternate embodiment in which the walls of the junction apparatus are formed with multiple plies, each being metal, to facilitate expansion from the collapsed position to the set position. For example,  FIG. 20  shows an inner wall or ply  53  located within an outer ply or wall of conical members  27 ′ and  29 ′. The stiffening plate is also formed of multiple plies as indicated by legs  38 ′. The total thickness of the two plies should be substantially no greater than that of a single wall which has the same pressure rating. The use of two walls for the various components of junction member  17  reduces the amount of strain that would otherwise occur during plastic deformation with a single wall having the same total thickness as the two plies. 
       FIGS. 21–40  illustrate another embodiment of a junction member, with the principal difference between junction member  55  does not use a stiffening plate such as stiffening plate  33  ( FIG. 2 ). Referring to  FIG. 22 , junction member  55  has an upper end section  57  that is cylindrical and of the same diameter as a main string of casing (not shown) for attachment to the main string of casing. A conical upper enlarged section  59  has an upper end welded to the lower end of upper end section  57 . Upper enlarged section  59  diverges in a downward direction, resulting in a greater diameter at its lower end at section line  31  than at its upper end above section line  25 . Upper enlarged section  59  has an axis  61  which is inclined relative to main casing axis  63 . 
     A conical lower enlarged section  65  has an upper end welded to part of the lower end of upper enlarged section  59 . Conical lower enlarged section  65  is much shorter in length than the length of upper enlarged section  59 . Conical section  65  converges in a downward direction, as can be seen by comparing  FIGS. 33 and 35 , and comprises one-half of a cone with a diameter at its lower end that is substantially the same as the diameter of the upper end section  57 . 
     A conical lateral section  67  also joins the lower end of upper enlarged section  59 . Conical lateral section  67  is the same length as conical lower enlarged section  65 , but of a lesser diameter. Referring to  FIG. 33 , conical lateral section  67  forms the right half of junction member  55  at section line  33 , with conical lower enlarged section  65  forming the left half at that point. Conical lower enlarged section  65  and lateral section  67  are truncated and abutted along their inner edges  68 , the inner edges  68  being in a plane which contains axis  61  of upper enlarged section. Inner edges  68  of the conical lower enlarged section  65  and conical lateral section  67  are welded together. 
     In the first embodiment, a stiffening plate  33  is located between the inner edges, while in this embodiment, it is not required due to the relatively short lengths of conical lower enlarged and lateral sections  65 ,  67 . As shown in  FIG. 33 , the shape of junction member  55  at that point is somewhat in the shape of a peanut, with a major dimension  69  that is greater than a minor dimension measured perpendicular to line  69  at the midpoint of line  69 . 
     Referring again to  FIG. 22 , a lower main section  71  of cylindrical configuration is welded to the lower end of conical lower enlarged section  65 . Lower main section  71  joins main casing (not shown) extending below and is coaxial with upper main section  57  and main axis  63 . A lower lateral section  73  of cylindrical configuration is welded to the lower end of conical lateral section  67 . Lower lateral section  73  will receive a string of lateral liner (not shown). Junction member  55  while in the expanded position resembles an inverted “Y”. A drillable plug  75  is secured in lower lateral section  73 . The diameter of lower lateral section  73  is smaller than the diameter of lower main section  71 . Lower lateral section  73  is located on a lateral branch axis  77  which is at an acute angle relative to main casing axis  63 . Upper enlarged section axis  61  bisects axes  63  and  77 , with all three axes  61 ,  63 ,  77  being in a single plane. 
     For manufacturing purposes, a segmented rod  79  is secured to junction apparatus  55 . Segmented rod  79  has two portions  79   a ,  79   b , each located on the exterior of junction member  55  180 deg. apart from the other. Segmented rod portions  79   a ,  79   b  are identical and are used when deforming junction member  55  from the set position of  FIG. 22  to the collapsed position of  FIG. 21 , as will be subsequently explained.  FIG. 23  shows segmented rod  79  prior to installation. Each segmented rod portion  79   a ,  79   b  has an upper end  81  which is tack welded to exterior portion of junction member  55  near the upper end of upper enlarged section  59 . The middle section  83  of segmented rod  79  loops under the lower end of the intersection of the conical lower enlarged section  65  and conical lateral section  67 . Each segmented rod portion  79   a ,  79   b  is located in a plane that contains upper enlarged section axis  61 . 
     Junction member  55  will first be formed and tested in the expanded configuration of  FIG. 22  or in the folded configuration of  FIG. 39  with some external support. Then it will be collapsed to the position shown in  FIG. 21  for passage into the well. Referring to  FIGS. 38 and 40 , in the first step, junction member  55  will be positioned on a folding machine  90  which extends from the lower end of lower lateral section  73  to upper end section  57  ( FIG. 22 ). Folding machine  90  has two opposed convex, blunt blades  91 ,  93 . Blades  91  are hinged together by a hinge  92  at the end near upper end section  57 . Folding machine  90  has two stationary retainers or supports  87 ,  89 .  FIGS. 38 and 39  are taken at a section similar to the section shown in  FIGS. 30 and 31 . 
     For reference, assume that blades  91 ,  93  are at the 0 deg. and 180 deg. position, while retainers  87 ,  89  are stationarily mounted at the 90 deg. and 270 deg. position. The lateral leg or lower lateral section  73  will be located at the 90 deg. position and held in place by stationary support  87 . Then, blades  91 ,  93  are moved toward each other by hydraulic force until a point on the inner diameter at the 0 deg. position contacts a point on the inner diameter at the 180 deg. position. This step folds junction member  55  into two halves, forming two concave bights  94 . Note by comparing  FIGS. 24 ,  26 ,  28  and  30 , that blades  91 ,  93  do not form bights  94  of constant depth. The distance between blades  91 ,  93  at hinge  92  and the conical configuration of junction member  55  creates shallower bights  94  at the upper end, with the inner sides of junction member  55  touching only in the proximity of section line  31  ( FIG. 22 ). 
     Then, as shown in  FIG. 41 , segmented rod  79  is secured in the bights  94 , with the middle portion  83  looped between lower lateral sections  73  and lower main section  71 . The upper ends  81  will be tack welded in the bights  94 . As shown in  FIGS. 26 ,  28  and  30 , the distance between segmented rod portions  79   a ,  79   b  gradually increases in the upward direction from the lower end of upper enlarged section  59  to the upper ends  81  generally at section line  26  ( FIG. 26 ). 
     Returning to  FIGS. 41 and 43 , junction member  55  is then placed in a collapsing machine  96 . Collapsing machine  96  has two concave dies  95 ,  97  which are semicylindrical, forming a cylinder when brought together as in  FIG. 42 . The inner diameter of dies  95 ,  97  is substantially the same as the outer diameter of upper end section  19  collar  20  ( FIG. 1 ). Concave dies  95 ,  97  are located at the 90 deg. and 270 deg. position and connected by a hinge  98  at the upper end as shown in  FIG. 43 .  FIGS. 41 ,  42  are also shown at a section line at the lower end of upper enlarged section  59 , this section line being shown in  FIG. 30 . 
     Die  95  is hydraulically moved toward die  97 , causing the two lobes opposite bights  94  to collapse into configuration shown in  FIG. 42 . In this configuration, junction member  55  has an outer diameter, or cylindrical surface of revolution, which is no greater than collar  20  of upper end section  57  or  19 . As can be seen in  FIGS. 32 and 34 , die  95  folds lower lateral section  73  inward into a concave depression formed in lower main section  71 . Lower main section  71  will be crescent-shaped, while lower lateral section  73  remains mostly cylindrical and substantially undeflected. As shown by dotted lines  99  in  FIG. 36 , the surface of revolution of junction member  55  is cylindrical and no greater at any point than the outer diameter of collar  20  ( FIG. 1 ). Segmented rod portions  79   a ,  79   b  limit strain during the bending of bights  94 , preventing them from forming curved portions which are too small in radius. 
     Junction apparatus  55  is run and installed in the same manner as described in connection with the first embodiment. It is run in while in the collapsed position of  FIG. 21 . Junction member  55  will locate within a reamed out section of the borehole. Hydraulic pressure is supplied to liquid contained in the main casing and junction apparatus  59 . A plug (not shown) at the cement shoe at the lower end of the main casing enables hydraulic pressure to be applied throughout the length of casing and junction apparatus  55 . The pressure causes junction member  55  to expand to the set position with lateral leg  73  moving outward. 
     After reaching this position, a valve will be shifted at the cement shoe to enable cement to be pumped downward, which flows through the main casing and back up at annulus surrounding the main casing. When it is desired to drill the lateral well bore, the operator uses a kick-off tool or whipstock to cause bit to enter lateral leg  73 , drill-out plug  75  and drill the lateral leg. Lateral casing of smaller diameter than the main casing will be run through lateral leg  73  and supported by a hanger mechanism in lateral leg  73 . Lateral casing will be cemented conventionally. 
     The invention has significant advantages. The junction apparatus provides a good seal between the main casing and the lateral branch casing. The junction member may be run in collapsed and expanded to a set position. The method of running the junction member in with the main casing avoids a need to mill out a window or section of the main casing. In the second embodiment, there is not need to plastically deflect greatly the cylindrical part of the lateral leg, facilitating a plug to be located therein. 
     While the invention has been shown in only one of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes without departing from the scope of the invention. For instance the conical sections can be replaced by an extended stiffening plate. Also the bottom of upper enlarged section  21  can be large enough to accommodate full access to both branches side by side, and the stiffening plate inner edge  35  can be straight without any legs  38 .