You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
BACKGROUND 
   The invention generally relates to a system and technique for orienting and positioning a lateral string in a multi-lateral system. 
   A multi-lateral well includes a parent wellbore and one or more lateral wellbores that extend from the parent wellbore. Quite often, a main parent casing string lines the parent wellbore; and liner string(s) hang from the parent casing string and extend from the parent wellbore into the lateral wellbore(s). 
   Conventionally, for purposes of creating a multi-lateral well, the parent wellbore is first drilled and then cased with a casing string. A particular lateral wellbore may then be established by first milling a window (called a “parent casing window”) out of the wall of the parent casing string. The parent casing window forms the entry point of the lateral wellbore from the parent wellbore. After the lateral wellbore is drilled, a lateral liner string is run downhole so that the liner string hangs from the parent casing string and extends into the lateral wellbore. Depending on the particular multi-lateral system, the liner string may be cemented in place inside the parent casing string and/or may be sealed to the parent casing string. 
   It is often desirable to position the depth and orient the azimuth of the liner string with respect to the parent wellbore. For example, the liner string may have a window (called a “liner window”) that needs to be positioned at the correct depth and properly oriented for purposes of, for example, permitting fluid communication between the central passageway of the liner string and the central passageway of the parent casing string. Furthermore, the liner window when properly positioned and oriented may be used to provide mechanical access to the parent wellbore beneath the liner string window. This access may be used for purposes of an intervention into this part of the parent wellbore. 
   Conventional systems to orient the liner string include features that are located on the parent casing window. However, many such systems have typically been somewhat unreliable. 
   Thus, there is a continuing need for better ways to orient a lateral string with respect to a parent wellbore. 
   SUMMARY 
   In an embodiment of the invention, a method that is usable with a subterranean well that has a first string that lines a borehole includes running a second string into the well and engaging a deflecting face on a deflector to deflect the second string through a window of the first string. The technique includes performing at least one of positioning the second string and orienting the second string using a profile on the deflector downhole of the deflecting face. 
   Advantages and other features of the invention will become apparent from the following description, drawing and claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic diagram of a subterranean well according to an embodiment of the invention. 
       FIG. 2  is a more detailed view of a portion of the well of  FIG. 1  according to an embodiment of the invention. 
       FIGS. 3 and 4  are flow diagrams depicting techniques to run a lateral liner string into a lateral wellbore according to different embodiments of the invention. 
       FIG. 5  is a top perspective view of the tubing deflector of  FIGS. 1 and 2  according to an embodiment of the invention. 
       FIG. 6  is a cross-sectional view taken along line  6 - 6  of  FIG. 5  according to an embodiment of the invention. 
       FIG. 7  is a cross-sectional view depicting initial engagement of the liner string with the tubing deflector according to an embodiment of the invention. 
   

   DETAILED DESCRIPTION 
   Referring to  FIG. 1 , an embodiment  10  of a multi-lateral subterranean well in accordance with the invention includes a tubular string  20  that extends into a parent wellbore that is lined by a parent casing string  15 . The string  20  includes a packer  24  (shown in the set position) from which hangs a tubular liner string  30 . The liner string  30  extends through a milled casing window  38  of the parent casing string  15  and into a lateral wellbore  17  of the well  10 . 
   It is noted that the well  10  that is depicted in  FIG. 1  is simplified for clarifying the following description. Thus, the well  10  may have other and different features in other embodiments of the invention. For example, in other embodiments of the invention, a well may include multiple lateral wellbores and liner strings. 
   For purposes of routing the liner string  30  into the lateral wellbore  17 , the well  10  includes a tubular, tubing string deflector (herein called the “deflector  40 ”), that is held in place generally concentric to the casing string  15  by means (an indexing casing coupler or a whipstock packer, as examples) known to those skilled in the art and is located beneath the casing window  38 . The deflector  40  includes a generally inclined deflecting face  42  that is sloped at an angle with respect to the longitudinal axis of the parent wellbore to deflect the liner string  30  (that generally follows the longitudinal axis of the parent wellbore before contacting the deflecting face  42 ) into the lateral wellbore  17 , as depicted in  FIG. 1 . 
   As also depicted in  FIG. 1 , in some embodiments of the invention, the liner string  30  includes a liner window  34 , a window that is formed in the wall of the liner string  30  (before the liner string  30  is run downhole, for example) so that when position at the appropriate depth and properly oriented, the liner window  34  provides access (via a longitudinal passageway  41  of the deflector  40 ) to the portion of the parent wellbore located beneath the window  34 . Thus, without the window  34 , access to and fluid communication with the parent wellbore below the window  34  is prevented. 
   As further described below, in some embodiments of the invention, a profile is formed on the deflector  40  to ensure proper positioning of the liner string  30  (to the appropriate depth) and proper orientation of the liner string  30  (at the appropriate azimuth) so that 1.) the liner window  34  aligns with the portion of the parent wellbore beneath the window  34  (and also faces the passageway  41  of the deflector  40 ); and 2.) the liner window  34  is located above the passageway  41 . This profile of the deflector  40  mates with a corresponding profile of the liner string  30  to, when the profiles engage, provide a positive indication (via a partial weight displacement of the string  20 ) at the surface of the proper depth and azimuth of the liner string  30  (and liner window  34 ). 
   Thus, as further described below, engagement of the two profiles is detectable at the surface of the well  10  to indicate that the liner string  30  is at the proper depth and azimuthal orientation. As a more specific example, in some embodiments of the invention, the deflector  40  includes a keyway profile that is constructed to receive a corresponding key profile of the liner string  30  when the liner string  30  has the appropriate depth and azimuthal orientation. 
   In some embodiments of the invention, the keyway profile of the deflector  40  is located below the deflecting face  42  so that when the deflector  40  is mounted to the inside of the casing string  15  (in a separate run into the well, for example), the casing window  38  exposes the keyway profile to the lateral wellbore  17 . The keyway profile is designed to provide a tracking range to, for a predefined range of potential azimuthal positions of the liner string  30 , rotate the liner string  30  into the proper final azimuthal position in which the liner window  34  is directed downhole and toward the opening of the passageway  41 . For purposes of coarsely adjusting the azimuth of the liner string  30  so that the key profile of the string  30  is within this tracking range, the string  20  may include a gyro  39 , in some embodiments of the invention. 
   For example, as depicted in  FIG. 1  the gyro  39  may be located near the liner window  34  (in some embodiments of the invention) for purposes of providing feedback (via a telemetry path (not shown)) to the surface of the well  10  regarding the azimuth of the liner string  30 . Therefore, by rotating the liner string  30  in accordance with the feedback that is provided by the gyro  39 , the liner string  30  may be rotated to a position near its final proper azimuthal position, as the deflector&#39;s keyway profile (via its engagement with the key profile of the liner string  30 ) performs the fine rotational adjustment of the liner string  30  to place the liner string  30  at the final proper azimuthal position. At the conclusion of this fine rotational adjustment, the key and keyway profiles mate to offset at least some weight on the string  20  so that an operator at the surface of the well can detect the engagement. The packer  24  may then be set to hang the liner string  30 , in some embodiments of the invention. 
   In other embodiments of the invention, the coarse azimuthal positioning of the liner string  30  is established by a trial and error tactic in that the liner string  30  may be incrementally rotated and then lowered to see if engagement between the key and keyway profiles occur (as indicated by the partial weight displacement of the string  20 ); and if not, the liner string  30  is pulled back uphole and rotated by another incremental adjustment. Therefore, this process is repeated until the partial weight displacement is detected at the surface of the well  10 . 
   In some embodiments of the invention, to facilitate azimuthal orientation of the liner string  30 , the liner string  30  includes a swivel clutch  33 , a device that decouples rotation of an upper portion  28  of the liner string  30  from a lower portion  32  portion of the string  30 . Thus, due to the clutch  33 , the upper portion  28  of the liner string  30  may be rotated without rotating the lower portion  32  to facilitate azimuthal orientation of the liner string  30 . 
     FIG. 2  depicts a more detailed section  50  (see  FIG. 1 ) of the well  10 . Referring to  FIG. 2 , as shown, in some embodiments of the invention, the deflector  40  includes a keyway profile  60  that is constructed to receive and mate with a corresponding key profile  70  of the liner string  30  when the liner string  30  is in its proper final azimuthal and depth positions. The keyway  60  and key  70  profiles may be switched, in other embodiments of the invention, so that the keyway profile  60  is located on the liner string  30 , and the key profile  70  is located on the deflector  40 . Thus, many variations are possible and are within the scope of the appended claims. 
   Although specific keyway  60  and key  70  profiles are depicted in  FIG. 2 , it is noted that these profiles are for purposes of example only to illustrate one out of many possible embodiments of the invention. For the embodiment that is depicted in  FIG. 2 , the keyway profile  60  includes a slot  61  that is constructed to receive a corresponding radial extension  74  of the key profile  70  when the profiles  60  and  70  mate. Furthermore, as depicted in  FIG. 2 , the keyway profile  60  may include a radial extension  62  that supports a corresponding radial extension  72  (of the key profile  70 ) that extends above the extension  62  when the profile  60  and  70  mate. The keyway profile  60  may include another radial extension  63  that extends below the radial extension  72  (of the key profile  70 ). The keyway  60  and key  70  profiles are also illustrated in a perspective view of the deflector  40  in  FIG. 5 . 
   Referring to  FIG. 3 , in some embodiments of the invention, a technique  100  may be used to run a liner string, such as the liner string  30 , downhole. Referring to  FIG. 3 , the technique  100  includes lowering (block  102 ) the liner string  30  downhole and determining (block  104 ) whether the liner string  30  is near the deflector  40 . If not, then the lowering continues, as depicted in block  102 . 
   When the liner string is near the deflector  40  (as indicated by the deployed length of the string  20 , for example), then the technique  100  includes using a downhole survey mechanism (i.e., an azimuth orientation device) (such as the gyro  39  of  FIG. 1 ) to rotate the liner string  30  to orient an upper section of the liner string  30  with respect to a milled casing window, as depicted in block  106 . Therefore, referring to  FIG. 1  in conjunction with  FIG. 3 , this rotation may include rotating the upper section  28  of the liner string  30  with respect to the lower section  32 . The bifurcated rotation is permitted due to the swivel clutch  33 . Referring to  FIG. 3 , after this rotation, the liner string  30  is lowered (block  108 ) and a determination is made (diamond  110 ) whether engagement between the mating profiles of the liner string  30  and deflector  40  have occurred. If so, then the technique  100  ends. Otherwise, the liner string continues to be lowered downhole pursuant to block  108 . 
   Alternatively, in some embodiments of the invention, the liner string  30  may not include an azimuth orientation device, such as a gyro. Instead, a trial and error technique may be used to orient the liner string  30  with respect to the parent borehole. More specifically,  FIG. 4  depicts another technique  130  for running a liner string downhole. Referring to  FIG. 4 , pursuant to the technique  130 , the liner string is lowered downhole (block  132 ) and a determination is made (diamond  134 ) whether engagement has occurred between the key and keyway profiles of the liner string and deflector. If so, then the technique  130  ends, as proper azimuthal orientation and depth positioning of the liner string has occurred. Otherwise, a determination is made (diamond  136 ) whether the key profile of the liner string is past the keyway profile of the deflector, as depicted in diamond  136 . This may be determined by, for example, monitoring the length of the string that is used to position the liner string. If the liner string has not been lowered past the profile, then the liner string is continued to be run downhole, pursuant to block  132 . 
   If the liner string has been run past the mating profile, then the liner string is picked up to a location above the deflector, as depicted in block  138 . After this pickup, the upper section of the liner string is incrementally rotated (block  140 ) and the trial and error technique continues by lowering the liner string downhole pursuant to block  132 . Eventually, the liner string has the proper azimuthal orientation and depth so that the key and keyway profiles engage, as indicated by partial weight displacement that is detectable at the surface of the well. 
     FIG. 5  depicts a top perspective view of the tubing deflector  40 , in accordance with some embodiments of the invention. Referring to  FIG. 5 , in some embodiments of the invention, the deflector  40  may be hollow (and thus, include the longitudinal passageway  41 ), and the deflecting face  42  may present an approximate U-shaped channel along about its longitudinal axis to guide the key profile of the liner string toward a narrowed region  160  that coincides with a longitudinal axis  150  (of the deflector  40 ). The longitudinal axis  150 , in turn, coincides with the keyway profile  60  of the deflector  40 . Referring also to  FIG. 6  (depicting a cross-section of the deflecting face  42  along line  6 - 6  of  FIG. 5 ), in some embodiments of the invention, the deflecting face  42  may include surfaces  162  and  164  that may be generally level, as depicted in  FIG. 6  at the uphole end of the deflecting force  42  and increasingly slanted toward the longitudinal axis  150  at the downhole end of the deflecting face  42 . It is noted that in some embodiments of the invention, the surfaces  162  and  164  may not be inclined towards the longitudinal axis  150 . The surfaces  162  and  164  follow the perimeter of the channel around the entry of the passageway  41  of the deflecting face  42  to meet at the longitudinal axis  150  (at narrowed region  160 ) to guide the key profile  70  (see  FIG. 2 ) of the liner string  30  toward the keyway profile  60 . 
   As a more specific example,  FIG. 7  depicts the cross section of the deflector  40  shown in  FIG. 6 , along with a cross-sectional view of the liner string  30  during the initial engagement between the key profile  70  of the liner string  30  and the deflecting face  42  of the deflector  40 . As depicted in  FIG. 7 , the radial extension  74  of the key profile  70  extends into the open groove of the face  42 . As also depicted in  FIG. 7 , separation between the inclined faces  162  and  164  provides a tracking range  180  that permits capture of the key profile  70  over a predetermined azimuthal range and guidance of the key profile  70  toward the longitudinal axis  150  and into the keyway profile  60 . 
   While the present invention has been described with respect to a limited number of embodiments, those skilled in the art, having the benefit of this disclosure, will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of this present invention.

Summary:
A technique that is usable with a subterranean well that has a first string that lines a borehole includes running a second string into the well and engaging a deflecting face of a deflector to deflect the second string into a window of the first string. The technique includes performing at least one of positioning the second string and orienting the second string using a profile on the deflector downhole of the deflecting face.