Patent Publication Number: US-8985203-B2

Title: Expandable bullnose assembly for use with a wellbore deflector

Description:
This application is a National Stage entry of and claims priority to International Application No. PCT/US2013/052087, filed on Jul. 25, 2013. 
     BACKGROUND 
     The present disclosure relates generally to multilateral wellbores and, more particularly, to an expandable bullnose assembly that works with a wellbore deflector to allow entry into more than one lateral wellbore of a multilateral wellbore. 
     Hydrocarbons can be produced through relatively complex wellbores traversing a subterranean formation. Some wellbores include one or more lateral wellbores that extend at an angle from a parent or main wellbore. Such wellbores are commonly called multilateral wellbores. Various devices and downhole tools can be installed in a multilateral wellbore in order to direct assemblies toward a particular lateral wellbore. A deflector, for example, is a device that can be positioned in the main wellbore at a junction and configured to direct a bullnose assembly conveyed downhole toward a lateral wellbore. Depending on various parameters of the bullnose assembly, some deflectors also allow the bullnose assembly to remain within the main wellbore and otherwise bypass the junction without being directed into the lateral wellbore. 
     Accurately directing the bullnose assembly into the main wellbore or the lateral wellbore can often be a difficult undertaking. For instance, accurate selection between wellbores commonly requires that both the deflector and the bullnose assembly be correctly oriented within the well and otherwise requires assistance from known gravitational forces. Moreover, conventional bullnose assemblies are typically only able to enter a lateral wellbore at a junction where the design parameters of the deflector correspond to the design parameters of the bullnose assembly. In order to enter another lateral wellbore at a junction having a differently designed deflector, the bullnose assembly must be returned to the surface and replaced with a bullnose assembly exhibiting design parameters corresponding to the differently designed deflector. This process can be time consuming and costly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following figures are included to illustrate certain aspects of the present disclosure, and should not be viewed as exclusive embodiments. The subject matter disclosed is capable of considerable modifications, alterations, combinations, and equivalents in form and function, without departing from the scope of this disclosure. 
         FIG. 1  illustrates an exemplary well system that may employ one or more principles of the present disclosure, according to one or more embodiments. 
         FIGS. 2A-2C  illustrate isometric, top, and end views, respectively, of the deflector of  FIG. 1 , according to one or more embodiments. 
         FIGS. 3A and 3B  illustrate isometric and cross-sectional side views, respectively, of an exemplary bullnose assembly, according to one or more embodiments. 
         FIG. 4  illustrates the bullnose assembly of  FIGS. 3A-3B  in its actuated configuration, according to one or more embodiments. 
         FIGS. 5A and 5B  illustrate end and cross-sectional side views, respectively, of the bullnose assembly of  FIGS. 3A-3B  in its default configuration as it interacts with the deflector of  FIGS. 1-2 , according to one or more embodiments. 
         FIGS. 6A and 6B  illustrate end and cross-sectional side views, respectively, of the bullnose assembly of  FIGS. 3A-3B  in its actuated configuration as it interacts with the deflector of  FIGS. 1-2 , according to one or more embodiments. 
         FIGS. 7A and 7B  illustrate cross-sectional side views of another exemplary bullnose assembly, according to one or more embodiments. 
         FIG. 8  illustrates an exemplary multilateral wellbore system that may implement the principles of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure relates generally to multilateral wellbores and, more particularly, to an expandable bullnose assembly that works with a wellbore deflector to allow entry into more than one lateral wellbore of a multilateral wellbore. 
     Disclosed is a bullnose assembly that is able to expand its diameter while downhole such that it is able to be accurately deflected into either a main wellbore or a lateral wellbore using a deflector. The deflector has a first channel that communicates to lower portions of the main wellbore, and a second channel that communicates with the lateral wellbore. If the diameter of the bullnose assembly is smaller than the diameter of the first channel, the bullnose assembly will be directed into the lower portions of the main wellbore. Alternatively, if the diameter of the bullnose assembly is larger than the diameter of the first channel, the bullnose assembly will be directed into the lateral wellbore. The variable nature of the disclosed bullnose assemblies allows for selective and repeat re-entry of any number of stacked multilateral wells having multiple junctions that are each equipped with the deflector. 
     Referring to  FIG. 1 , illustrated is an exemplary well system  100  that may employ one or more principles of the present disclosure, according to one or more embodiments. The well system  100  includes a main bore  102  and a lateral bore  104  that extends from the main bore  102  at a junction  106  in the well system  100 . The main bore  102  may be a wellbore drilled from a surface location (not shown), and the lateral bore  104  may be a lateral or deviated wellbore drilled at an angle from the main bore  102 . While the main bore  102  is shown as being oriented vertically, the main bore  102  may be oriented generally horizontal or at any angle between vertical and horizontal, without departing from the scope of the disclosure. 
     In some embodiments, the main bore  102  may be lined with a casing string  108  or the like, as illustrated. The lateral bore  104  may also be lined with casing string  108 . In other embodiments, however, the casing string  108  may be omitted from the lateral bore  104  such that the lateral bore  104  may be formed as an “open hole” section, without departing from the scope of the disclosure. 
     In some embodiments, a tubular string  110  may be extended within the main bore  102  and a deflector  112  may be arranged within or otherwise form an integral part of the tubular string  110  at or near the junction  106 . The tubular string  110  may be a work string extended downhole within the main bore  102  from the surface location and may define or otherwise provide a window  114  therein such that downhole tools or the like may exit the tubular string  110  into the lateral bore  104 . In other embodiments, the tubular string  110  may be omitted and the deflector  112  may instead be arranged within the casing string  108 , without departing from the scope of the disclosure. 
     As discussed in greater detail below, the deflector  112  may be used to direct or otherwise guide a bullnose assembly (not shown) either further downhole within the main bore  102 , or into the lateral bore  104 . To accomplish this, the deflector  112  may include a first channel  116   a  and a second channel  116   b . The first channel  116   a  may exhibit a predetermined width or diameter  118 . Any bullnose assemblies that are smaller than the predetermined diameter  118  may be directed into the first channel  116   a  and subsequently to lower portions of the main bore  102 . In contrast, bullnose assemblies that are greater than the predetermined diameter  118  may slidingly engage a ramped surface  120  that forms an integral part or extension of the second channel  116   b  and otherwise serves to guide or direct a bullnose assembly into the lateral bore  104 . 
     Referring now to  FIGS. 2A-2C , with continued reference to  FIG. 1 , illustrated are isometric, top, and end views, respectively of the deflector  112  of  FIG. 1 , according to one or more embodiments. The deflector  112  may have a body  202  that provides a first end  204   a  and a second end  204   b . The first end  204   a  may be arranged on the uphole end (i.e., closer to the surface of the wellbore) of the main bore  102  ( FIG. 1 ) and the second end  204   b  may be arranged on the downhole end (i.e., closer to the toe of the wellbore) of the main bore  102 .  FIG. 2C , for example, is a view of the deflector  112  looking at the first end  204   a.    
     As illustrated, the deflector  112  may provide the first channel  116   a  and the second channel  116   b , as generally described above. The deflector  112  may further provide or otherwise define the ramped surface  120  (not shown in  FIG. 2C ) that generally extends from the first end  204   a  to the second channel  116   b  and otherwise forms an integral part or portion thereof. As indicated, the first channel  116   a  extends through the ramped surface  120  and exhibits the predetermined diameter  118  discussed above. Accordingly, any bullnose assemblies (not shown) having a diameter that is smaller than the predetermined diameter  118  may be guided through the ramped surface  120  and otherwise into the first channel  116   a  and subsequently to lower portions of the main bore  102 . In contrast, bullnose assemblies having a diameter that is greater than the predetermined diameter  118  will ride up the ramped surface  120  and into the second channel  116   b  which feeds the lateral bore  104 . 
     Referring now to  FIGS. 3A and 3B , with continued reference to FIGS.  1  and  2 A- 2 C, illustrated are isometric and cross-sectional side views, respectively, of an exemplary bullnose assembly  300 , according to one or more embodiments. The bullnose assembly  300  may constitute the distal end of a tool string (not shown), such as a bottom hole assembly or the like, that is conveyed downhole within the main bore  102  ( FIG. 1 ). In some embodiments, the bullnose assembly  300  is conveyed downhole using coiled tubing (not shown). In other embodiments, however, the bullnose assembly  300  may be conveyed downhole using other types of conveyances such as, but not limited to, drill pipe, production tubing, or any other conveyance capable of being fluidly pressurized. In yet other embodiments, the conveyance may be wireline, slickline, or electrical line, without departing from the scope of the disclosure. The tool string may include various downhole tools and devices configured to perform or otherwise undertake various wellbore operations once accurately placed in the downhole environment. The bullnose assembly  300  may be configured to accurately guide the tool string downhole such that it reaches its target destination, e.g., the lateral bore  104  of  FIG. 1  or further downhole within the main bore  102 . 
     To accomplish this, the bullnose assembly  300  may include a body  302  and a bullnose tip  304  coupled or otherwise attached to the distal end of the body  302 . In some embodiments, the bullnose tip  304  may form an integral part of the body  302  as an integral extension thereof. As illustrated, the bullnose tip  304  may be rounded off at its end or otherwise angled or arcuate such that it does not present sharp corners or angled edges that might catch on portions of the main bore  102  or the deflector  112  ( FIG. 1 ) as it is extended downhole. 
     The bullnose assembly  300  is shown in  FIGS. 3A and 3B  in a default configuration where the bullnose tip  304  exhibits a first diameter  306   a . The first diameter  306   a  may be less than the predetermined diameter  118  (FIGS.  1  and  2 A- 2 C) of the first channel  116   a . Consequently, when the bullnose assembly  300  is in the default configuration, it may be sized such that it is able to extend into the first channel  116   a  and into lower portions of the main bore  102 . In contrast, as will be discussed in greater detail below, the bullnose assembly  300  is shown in  FIG. 4  in an actuated configuration where the bullnose tip  304  exhibits a second diameter  306   b . The second diameter  306   b  is greater than the first diameter  306   a  and also greater than the predetermined diameter  118  (FIGS.  1  and  2 A- 2 C) of the first channel  116   a . Consequently, when the bullnose assembly  300  is in its actuated configuration, it may be sized such that it will be directed into the second channel  116   b  via the ramped surface  120  ( FIGS. 2A-2C ) and subsequently into the lateral bore  104 . 
     In some embodiments, the bullnose assembly  300  may include a piston  308  movably arranged within a piston chamber  310  defined within the bullnose tip  304 . The piston  308  may be operatively coupled to a wedge member  312  disposed about the body  302  such that movement of the piston  308  correspondingly moves the wedge member  312 . In the illustrated embodiment, one or more coupling pins  314  (two shown) may operatively couple the piston  308  to the wedge member  312 . More particularly, the coupling pins  314  may extend between the piston  308  and the wedge member  312  through corresponding longitudinal grooves  316  defined in the body  302 . 
     In other embodiments, however, the piston  308  may be operatively coupled to the wedge member  312  using any other device or coupling method known to those skilled in the art. For example, in at least one embodiment, the piston  308  and the wedge member  312  may be operatively coupled together using magnets (not shown). In such embodiments, one magnet may be installed in one of the piston  308  and the wedge member  312 , and another corresponding magnet may be installed in the other of the piston  308  and the wedge member  312 . The magnetic attraction between the two magnets may be such that movement of one urges or otherwise causes corresponding movement of the other. 
     The bullnose tip  304  may include a sleeve  318  and an end ring  319 , where the sleeve  318  and the end ring  319  may form part of or otherwise may be characterized as an integral part of the bullnose tip  304 . Accordingly, the bullnose tip  304 , the sleeve  318 , and the end ring  319  may cooperatively define the “bullnose tip.” As illustrated, the sleeve  318  generally interposes the end rig  319  and the bullnose tip  304 . The wedge member  312  may be secured about the body  302  between the sleeve  318  and the bullnose tip  304 . More particularly, the wedge member  312  may be movably arranged within a wedge chamber  320  defined at least partially between the sleeve  318  and the bullnose tip  304  and the outer surface of the body  302 . In operation, the wedge member  312  may be configured to move axially within the wedge chamber  320 . 
     The bullnose assembly  300  may further include a coil  322  wrapped about the bullnose tip  304 . More particularly, the coil  322  may be arranged within a gap  324  defined between the sleeve  318  and the bullnose tip  304  and otherwise sitting on or engaging a portion of the wedge member  312 . The coil  322  may be, for example, a helical coil or a helical spring that is wrapped around the bullnose tip  304  one or more times. In other embodiments, however, the coil  322  may be a series of snap rings or the like. In the illustrated embodiment, two wraps or revolutions of the coil  322  are shown, but it will be appreciated that more than two wraps (or a single wrap) may be employed, without departing from the scope of the disclosure. In the default configuration ( FIGS. 3A and 3B ), the coil  322  sits generally flush with the outer surface of the bullnose tip  304  such that it also generally exhibits the first diameter  306   a.    
     In some embodiments, the outer radial surface  326   a  of each wrap of the coil  322  may be generally planar, as illustrated. The inner radial surface  326   b  and the axial sides  326   c  of each wrap of the coil  322  may also be generally planar, as also illustrated. As will be appreciated, the generally planar nature of the coil  322 , and the close axial alignment of the sleeve  318  and the bullnose tip  304  with respect to the coil  322 , may prove advantageous in preventing the influx of sand or debris into the interior of the bullnose tip  304 . 
     Referring now to  FIG. 4 , with continued reference to  FIGS. 3A-3B , illustrated is the bullnose assembly  300  in its actuated configuration, according to one or more embodiments. In order to move the bullnose assembly  300  from its default configuration ( FIGS. 3A-3B ) into its actuated configuration ( FIG. 4 ), the wedge member  312  may be actuated such that it moves the coil  322  radially outward to the second diameter  306   b . In some embodiments, this may be accomplished by applying a hydraulic fluid  328  from a surface location, through the conveyance (i.e., coiled tubing, drill pipe, production tubing, etc.) coupled to the bullnose assembly  300 , and from the conveyance to the interior of the bullnose assembly  300  (i.e., the interior of the body  302 ). At the bullnose assembly  300 , the hydraulic fluid  328  enters the body  302  and acts on the piston  308  such that the piston  308  axially translates within the piston chamber  310  towards the distal end of the bullnose tip  304  (i.e., to the right in  FIGS. 3B and 4 ). One or more sealing elements  330  (two shown), such as O-rings or the like, may be arranged between the piston  308  and the inner surface of the piston chamber  310  such that a sealed engagement at that location results. 
     As the piston  308  translates axially within the piston chamber  310 , it engages a biasing device  332  arranged within the piston chamber  310 . In some embodiments, the biasing device  332  may be a helical spring or the like. In other embodiments, the biasing device  332  may be a series of Belleville washers, an air shock, or the like, without departing from the scope of the disclosure. In some embodiments, the piston  308  may define a cavity  334  that receives at least a portion of the biasing device  332  therein. Moreover, the bullnose tip  304  may also define or otherwise provide a stem  336  that extends axially from the distal end of the bullnose tip  304  in the uphole direction (i.e., to the left in  FIGS. 3A and 3B ). The stem  336  may also extend at least partially into the cavity  334 . The stem  336  may also be extended at least partially into the biasing device  332  in order to maintain an axial alignment of the biasing device  332  with respect to the cavity  334  during operation. As the piston  308  translates axially within the piston chamber  310 , the biasing device  332  is compressed and generates spring force. 
     Moreover, as the piston  308  translates axially within the piston chamber  310 , the wedge member  312  correspondingly moves axially since it is operatively coupled thereto. In the illustrated embodiment, as the piston  308  moves, the coupling pins  314  translate axially within the corresponding longitudinal grooves  316  and thereby move the wedge member  312  in the same direction. As the wedge member  312  axially advances within the wedge chamber  320 , the wedge member  312  engages the coil  322  at a beveled surface  338  that forces the coil  322  radially outward to the second diameter  306   b.    
     Once it is desired to return the bullnose assembly  300  to its default configuration, the hydraulic pressure on the bullnose assembly  300  may be released. Upon releasing the hydraulic pressure, the spring force built up in the biasing device  332  may force the piston  308  back to its default position, thereby correspondingly moving the wedge member  312  and allowing the coil  322  to radially contract to the position shown in  FIGS. 3A-3B . As a result, the bullnose tip  304  may be effectively returned to the first diameter  306   a . As will be appreciated, such an embodiment allows a well operator to increase the overall diameter of the bullnose tip  304  on demand while downhole simply by applying pressure through the conveyance and to the bullnose assembly  300 . 
     Those skilled in the art, however, will readily recognize that several other methods may equally be used to actuate the wedge member  312 , and thereby move the bullnose assembly  300  between the default configuration ( FIGS. 3A-3B ) and the actuated configuration ( FIG. 4 ). For instance, although not depicted herein, the present disclosure also contemplates using one or more actuating devices to physically adjust the axial position of the wedge member  312  and thereby move the coil  322  to the second diameter  306   b . Such actuating devices may include, but are not limited to, mechanical actuators, electromechanical actuators, hydraulic actuators, pneumatic actuators, combinations thereof, and the like. Such actuators may be powered by a downhole power unit or the like, or otherwise powered from the surface via a control line or an electrical line. The actuating device (not shown) may be operatively coupled to the piston  308  or the wedge member  312  and otherwise configured to move the wedge member  312  axially within the wedge chamber  320  and thereby force the coil  322  radially outward. 
     In yet other embodiments, the present disclosure further contemplates actuating the wedge member  312  by using fluid flow around or flowing past the bullnose assembly  300 . In such embodiments, one or more ports (not shown) may be defined through the bullnose tip  304  such that the piston chamber  310  is placed in fluid communication with the fluids outside the bullnose assembly  300 . A fluid restricting nozzle may be arranged in one or more of the ports such that a pressure drop is created across the bullnose assembly  300 . Such a pressure drop may be configured to force the piston  308  toward the actuated configuration ( FIG. 4 ) and correspondingly move the wedge member  312  in the same direction. In yet other embodiments, hydrostatic pressure may be applied across the bullnose assembly  300  to achieve the same end. 
     While the bullnose assembly  300  described above depicts the bullnose tip  304  as moving between the first and second diameters  306   a,b , where the first diameter is less than the predetermined diameter  118  and the second diameter is greater than the predetermined diameter  118 , the present disclosure further contemplates embodiments where the dimensions of the first and second diameters  306   a,b  are reversed. More particularly, the present disclosure further contemplates embodiments where the bullnose tip  304  in the default configuration may exhibit a diameter greater than the predetermined diameter  118  and may exhibit a diameter less than the predetermined diameter  118  in the actuated configuration, without departing from the scope of the disclosure. Accordingly, actuating the bullnose assembly  300  may entail a reduction in the diameter of the bullnose tip  304 , without departing from the scope of the disclosure. 
     Referring now to  FIGS. 5A and 5B , with continued reference to  FIGS. 1-4 , illustrated are end and cross-sectional side views, respectively, of the bullnose assembly  300  in its default configuration as it interacts with the deflector  112  of  FIGS. 1 and 2 , according to one or more embodiments. In its default configuration, as discussed above, the bullnose tip  304  exhibits the first diameter  306   a . The first diameter  306   a  may be less than the predetermined diameter  118  (FIGS.  1  and  2 A- 2 C) of the first channel  116   a . Consequently, in its default configuration the bullnose assembly  300  may be able to extend through the ramped surface  120  and otherwise into the first channel  116   a  where it will be guided into the lower portions of the main bore  102 . 
     Referring now to  FIGS. 6A and 6B , with continued reference to  FIGS. 1-4 , illustrated are end and cross-sectional side views, respectively, of the bullnose assembly  300  in its actuated configuration as it interacts with the deflector  112  of  FIGS. 1 and 2 , according to one or more embodiments. In the actuated configuration, the coil  322  has been forced radially outward and thereby effectively increases the diameter of the bullnose tip  304  from the first diameter  306   a  (FIGS.  5 A- 5 B) to the second diameter  306   b . The second diameter  306   b  is greater than the predetermined diameter  118  (FIGS.  1  and  2 A- 2 C) of the first channel  116   a . Consequently, upon encountering the deflector  112  in the actuated configuration, the bullnose assembly  300  is prevented from entering the first channel  116   a , but instead slidingly engages the ramped surface  120  which serves to deflect the bullnose assembly  300  into the second channel  116   b  and subsequently into the lateral bore  104  ( FIG. 1 ). 
     Referring now to  FIGS. 7A and 7B , illustrated are cross-sectional side views of another exemplary bullnose assembly  700 , according to one or more embodiments. The bullnose assembly  700  may be similar in some respects to the bullnose assembly  300  of  FIGS. 3A and 3B  and therefore may be best understood with reference thereto, where like numeral will represent like elements not described again in detail. Similar to the bullnose assembly  300 , the bullnose assembly  700  may be configured to accurately guide a tool string or the like downhole such that it reaches its target destination, e.g., the lateral bore  104  of  FIG. 1  or further downhole within the main bore  102 . Moreover, similar to the bullnose assembly  300 , the bullnose assembly  700  may be able to alter its diameter such that it is able to interact with the deflector  112  and thereby selectively determine which path to follow (e.g., the main bore  102  or the lateral bore  104 ). 
     More particularly, the bullnose assembly  700  is shown in  FIG. 7A  in its default configuration where the bullnose tip  304  exhibits a first diameter  702   a . The first diameter  702   a  may be less than the predetermined diameter  118  (FIGS.  1  and  2 A- 2 C) of the first channel  116   a . Consequently, when the bullnose assembly  700  is in the default configuration, it may be sized such that it is able to extend through the ramped surface  120  ( FIGS. 2A-2C ) and otherwise into the first channel  116   a  where it will be guided into the lower portions of the main bore  102 . 
     In contrast, the bullnose assembly  700  is shown in  FIG. 7B  in its actuated configuration where the bullnose tip  304  exhibits a second diameter  702   b . The second diameter  702   b  is greater than the first diameter  702   a  and also greater than the predetermined diameter  118  (FIGS.  1  and  2 A- 2 C) of the first channel  116   a . Consequently, upon encountering the deflector  112  in the actuated configuration, the bullnose assembly  700  is prevented from entering the first channel  116   a , but instead slidingly engages the ramped surface  120  ( FIGS. 2A-2C ) which deflects the bullnose assembly  700  into the second channel  116   b  and subsequently into the lateral bore  104  ( FIG. 1 ). 
     In order to move between the default and actuated configurations, the bullnose assembly  700  may include a piston  704  arranged within a piston chamber  706 . The piston chamber  706  may be defined within a collet body  708  coupled to or otherwise forming an integral part of the bullnose tip  304 . The collet body  708  may define a plurality of axially extending fingers  710  (best seen in  FIG. 7B ) that are able to flex upon being forced radially outward. The collet body  708  further includes a radial protrusion  712  defined on the inner surface of the collet body  708  and otherwise extending radially inward from each of the axially extending fingers  710 . The radial protrusion  712  may be configured to interact with a wedge member  713  defined on the outer surface of the piston  704 . 
     The piston  704  may include a piston rod  714 . The piston rod  714  may be actuated axially in order to correspondingly move the piston  704  within the piston chamber  706  such that the wedge member  713  is able to interact with the radial protrusion  712 . In some embodiments, similar to the piston  308  of  FIG. 3B , the piston rod  714  may be actuated by hydraulic pressure acting on an end (not shown) of the piston rod  714 . In other embodiments, however, piston rod  714  may be actuated using one or more actuating devices to physically adjust the axial position of the piston  704 . The actuating device (not shown) may be operatively coupled to the piston rod  714  and configured to move the piston  704  back and forth within the piston chamber  706 . In yet other embodiments, the present disclosure further contemplates actuating the piston rod  714  using fluid flow around the bullnose assembly  700  or hydrostatic pressure, as generally described above. 
     As the piston  704  moves axially within the piston chamber  706 , it compresses a biasing device  716  arranged within the piston chamber  706 . Similar to the biasing device  332  of  FIGS. 3A and 4 , the biasing device  716  may be a helical spring, a series of Belleville washers, an air shock, or the like. In some embodiments, the piston  308  defines a cavity  718  that receives the biasing device  716  at least partially therein. The opposing end of the biasing device  716  may engage the inner end  720  of the bullnose tip  304 . Compressing the biasing device  716  with the piston  704  generates a spring force. 
     Moreover, as the piston  704  moves axially within the piston chamber  706 , the wedge member  713  engages the radial protrusion  712  and forces the axially extending fingers  710  radially outward. This is seen in  FIG. 7B . Once forced radially outward, the bullnose tip  304  effectively exhibits the second diameter  702   b , as described above. To return to the default configuration, the process is reversed and the bullnose tip  304  is returned to the first diameter  702   a.    
     Referring again to  FIGS. 5A-5B  and  6 A- 6 B, with continued reference to  FIGS. 7A and 7B , it will be appreciated that the bullnose assembly  300  may be replaced with the bullnose assembly  700  described in  FIGS. 7A and 7B , without departing from the scope of the disclosure. For instance, in its default configuration, the bullnose tip  304  of the bullnose assembly exhibits the first diameter  702   a  and therefore is able to extend through the ramped surface  120  and otherwise into the first channel  116   a  where it will be guided into the lower portions of the main bore  102 . Moreover, in the actuated configuration, the diameter of the bullnose assembly  700  is increased to the second diameter  702   b , and therefore, upon encountering the deflector  112  in the actuated configuration, the bullnose assembly  700  is prevented from entering the first channel  116   a . Rather, the bullnose tip  304  slidingly engages the ramped surface  120  which deflects the bullnose assembly  700  into the second channel  116   b  and subsequently into the lateral bore  104  ( FIG. 1 ). 
     Accordingly, which bore (e.g., the main bore  102  or the lateral bore  104 ) a bullnose assembly  300 ,  700  enters is primarily determined by the relationship between the diameter of the bullnose tip  304  and the predetermined diameter  118  of the first channel  116   a . As a result, it becomes possible to “stack” multiple junctions  106  ( FIG. 1 ) having the same deflector  112  design in a single multilateral well and entering respective lateral bores  104  at each junction  106  with a single, expandable bullnose assembly  300 ,  700 , all in a single trip into the well. 
     Referring to  FIG. 8 , with continued reference to the previous figures, illustrated is an exemplary multilateral wellbore system  800  that may implement the principles of the present disclosure. The wellbore system  800  may include a main bore  102  that extends from a surface location (not shown) and passes through at least two junctions  106  (shown as a first junction  106   a  and a second junction  106   b ). While two junctions  106   a,b  are shown in the wellbore system  800 , it will be appreciated that more than two junctions  106   a,b  may be utilized, without departing from the scope of the disclosure. 
     At each junction  106   a,b , a lateral bore  104  (shown as first and second lateral bores  104   a  and  104   b , respectively) extends from the main bore  102 . The deflector  112  of  FIGS. 2A-2C  may be arranged at each junction  106   a,b . Accordingly, each junction  106   a,b  includes a deflector  112  having a first channel  116   a  that exhibits a first diameter  118  and a second channel  116   b.    
     In exemplary operation, an expandable bullnose assembly, such as the bullnose assemblies  300 ,  700  described herein, may be introduced downhole and actuated in order to enter the first and second lateral bores  104   a,b  at each junction  106   a,b , respectively. For instance, if it is desired to enter the first lateral bore  104   a , the bullnose assembly  300 ,  700  may be actuated prior to reaching the deflector  112  at the first junction  106   a . As a result, the bullnose assembly  300 ,  700  will exhibit the second diameter  306   b ,  702   b  and thereby be directed into the second channel  116   b  since the second diameter  306   b ,  702   b  is greater than the predetermined diameter  118  of the first channel  116   a . Otherwise, the bullnose assembly  300 ,  700  may remain in its default configuration with the first diameter  306   a ,  702   a  and pass through the first channel  116   a  of the deflector  112  at the first junction  106   a.    
     Once past the first junction  106   a , the bullnose assembly  300 ,  700  may enter the second lateral bore  104   b  by being actuated prior to reaching the deflector  112  at the second junction  106   b . As a result, the bullnose assembly  300 ,  700  will again exhibit the second diameter  306   b ,  702   b  and thereby be directed into the second channel  116   b  at the deflector  112  of the second junction  106   b  since the second diameter  306   b ,  702   b  is greater than the predetermined diameter  118  of the first channel  116   a . If it is desired to pass through the deflector  112  of the second junction  106   b  and into the lower portions of the main bore  102 , the bullnose assembly  300 ,  700  may remain in its default configuration with the first diameter  306   a ,  702   a  and pass through the first channel  116   a  of the deflector  112  at the second junction  106   b.    
     Embodiments disclosed herein include: 
     A. A well system that includes a deflector arranged within a main bore of a wellbore and defining a first channel that exhibits a predetermined diameter and communicates with a lower portion of the main bore, and a second channel that communicates with a lateral bore, and a bullnose assembly including a body and a bullnose tip arranged at a distal end of the body, the bullnose tip being actuatable between a default configuration, where the bullnose tip exhibits a first diameter, and an actuated configuration, where the bullnose tip exhibits a second diameter different than the first diameter, wherein the deflector is configured to direct the bullnose assembly into one of the lateral bore and the lower portion of the main bore based on a diameter of the bullnose tip as compared to the predetermined diameter. 
     B. A bullnose assembly that includes a body, and a bullnose tip arranged at a distal end of the body, the bullnose tip being configured to move between a default configuration, where the bullnose tip exhibits a first diameter, and an actuated configuration, where the bullnose tip exhibits a second diameter that is different than the first diameter. 
     C. A multilateral wellbore system that includes a main bore having a first junction and a second junction spaced downhole from the first junction, a first deflector arranged at the first junction and defining a first channel that exhibits a predetermined diameter and communicates with a first lower portion of the main bore, and a second channel that communicates with a first lateral bore, a second deflector arranged at the second junction and defining a third channel that exhibits the predetermined diameter and communicates with a second lower portion of the main bore, and a fourth channel that communicates with a second lateral bore, and a bullnose assembly including a body and a bullnose tip arranged at a distal end of the body, the bullnose assembly being configured to move between a default configuration, where the bullnose tip exhibits a first diameter, and an actuated configuration, where the bullnose tip exhibits a second diameter that is different than the predetermined diameter, wherein the first and second deflectors are configured to direct the bullnose assembly into one of the first and second lateral bores and the first and second lower portions of the main bore based on a diameter of the bullnose tip as compared to the predetermined diameter. 
     Each of embodiments A, B, and C may have one or more of the following additional elements in any combination: Element 1: wherein the deflector further includes a ramped surface that guides the bullnose assembly to the second channel when the diameter of the bullnose tip is greater than the predetermined diameter. Element 2: wherein the first diameter is less than the predetermined diameter and the second diameter is greater than both the first diameter and the predetermined diameter, and wherein, when the bullnose tip exhibits the first diameter, the bullnose assembly is directed into the first channel and the lower portion of the main bore, and wherein, when the bullnose tip exhibits the second diameter, the bullnose assembly is directed into the second channel and the lateral bore. Element 3: wherein the bullnose assembly further includes a piston movably arranged within a piston chamber defined within the bullnose tip, a wedge member operatively coupled to the piston such that movement of the piston correspondingly moves the wedge member, and a coil arranged about the bullnose tip and in contact with the wedge member, the piston being actuatable such that the wedge member is moved to radially expand the coil, wherein, when the coil is radially expanded, the diameter of the bullnose tip exceeds the predetermined diameter. Element 4: wherein the piston is actuatable using at least one of hydraulic pressure acting on the piston, an actuating device operatively coupled to the piston, and a pressure drop created across the bullnose assembly that forces the piston to move within the piston chamber. Element 5: wherein the bullnose assembly further includes a collet body forming at least part of the bullnose tip and defining a plurality of axially extending fingers, a radial protrusion defined on an inner surface of the collet body and extending radially inward from each axially extending finger, and a piston movably arranged within a piston chamber defined within the collet body and having a wedge member defined on an outer surface thereof, the piston being actuatable such that the wedge member engages the radial protrusion and forces the plurality of axially extending fingers radially outward, wherein, when the plurality of axially extending fingers is forced radially outward, the diameter of the bullnose tip exceeds the predetermined diameter. Element 6: wherein the piston is actuatable using at least one of hydraulic pressure acting on the piston, an actuating device operatively coupled to the piston, and a pressure drop created across the bullnose assembly that forces the piston to move within the piston chamber. Element 7: wherein the first diameter is greater than the predetermined diameter and the second diameter is less than both the first diameter and the predetermined diameter, and wherein, when the bullnose tip exhibits the first diameter, the bullnose assembly is directed into the second channel and the lateral bore, and wherein, when the bullnose tip exhibits the second diameter, the bullnose assembly is directed into the first channel and the lower portion of the main bore. 
     Element 8: wherein the first diameter is less than the predetermined diameter and the second diameter is greater than both the first diameter and the predetermined diameter, and wherein when the bullnose assembly is in the default configuration it is able to be directed into the first and third channels and the first and second lower portions of the main bore, respectively, and wherein, when the bullnose assembly is in the actuated configuration it is able to be directed into the second and fourth channels and the first and second lateral bores, respectively. Element 9: wherein the first diameter is greater than the predetermined diameter and the second diameter is less than both the first diameter and the predetermined diameter, and wherein when the bullnose assembly is in the default configuration it is able to be directed into the second and fourth channels and the first and second lateral bores, respectively, and wherein, when the bullnose assembly is in the actuated configuration it is able to be directed into the first and third channels and the first and second lower portions of the main bore. Element 10: wherein the first and second deflectors each include a ramped surface that guides the bullnose assembly to the second and fourth channels, respectively, when the bullnose assembly is in the actuated configuration. 
     Therefore, the disclosed systems and methods are well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the teachings of the present disclosure may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered, combined, or modified and all such variations are considered within the scope of the present disclosure. The systems and methods illustratively disclosed herein may suitably be practiced in the absence of any element that is not specifically disclosed herein and/or any optional element disclosed herein. While compositions and methods are described in terms of “comprising,” “containing,” or “including” various components or steps, the compositions and methods can also “consist essentially of” or “consist of” the various components and steps. All numbers and ranges disclosed above may vary by some amount. Whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any included range falling within the range is specifically disclosed. In particular, every range of values (of the form, “from about a to about b,” or, equivalently, “from approximately a to b,” or, equivalently, “from approximately a-b”) disclosed herein is to be understood to set forth every number and range encompassed within the broader range of values. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. Moreover, the indefinite articles “a” or “an,” as used in the claims, are defined herein to mean one or more than one of the element that it introduces. If there is any conflict in the usages of a word or term in this specification and one or more patent or other documents that may be incorporated herein by reference, the definitions that are consistent with this specification should be adopted.