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BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention generally relates to the field of oil and/or gas exploration and production and more specifically relates to an apparatus and method for maintaining a wellbore. 
     2. Description of the Related Art 
     Wells drilled for producing oil and/or gas extend from the surface through a subterranean formation where they intersect a hydrocarbon bearing strata. The wells may include one or more lateral wells that intersect a primary wellbore and extend into the formation away from the primary wellbore. The lateral wellbores typically are formed to produce from a particular hydrocarbon laden zone identified away from the primary wellbore. Additionally, utilizing lateral wellbores enables production from a much larger area while limiting drilling costs to a single primary wellbore. 
     From time to time, however, lateral wellbores may require inspection and/or repair. Locating and entering these lateral wellbores can sometimes be difficult due at least in part to the uncertainties inherent in defining the direction of the lateral within the main wellbore. This is especially so when disposing a downhole tool on coiled tubing or wireline. Known devices available for locating a lateral wellbore include mechanical locators provided within the well that can be identified by various means. With reference now to  FIG. 1 , an example is shown in a side partial sectional view of a wellbore  2  formed through a subterranean formation  4 . In this example, the wellbore  2  comprises a primary wellbore  3  with lateral wellbores  5 ,  6 ,  7  intersecting the primary wellbore  3  at various locations along its length. 
     A wellbore operations system  10  is shown inserted into the wellbore  2 . The system includes a downhole tool  18  deployed in the primary wellbore  3  on a length of tubing  14 . The tubing  14  is provided from a reel  12  shown threaded through a wellbore tree  16  mounted on the upper end of the wellbore  2 . Further illustrated in  FIG. 1  is a whipstock  20 , which is a simple example of an entry device for directing the tool  18  into the lateral wellbore  7 . Also shown in the example of  FIG. 1  is water and/or gas  22  emanating from within the lateral wellbore  7  and into the primary wellbore  3 . Addressing unwanted water and/or gas production from a lateral well is one example of downhole operations that can be performed in a lateral well. 
     SUMMARY OF THE INVENTION 
     Disclosed herein is a method of maintaining a wellbore having a primary wellbore and at least one lateral wellbore intersecting the primary wellbore. The wellbore includes a wall along the inner surface of the primary and lateral wellbores. A downhole tool is put into the primary wellbore and forms an annulus between the tool and the wall in the primary wellbore. The tool may include an acoustic transducer used for generating an acoustic signal directed from the tool to the wellbore wall. When the signal reflects from the wellbore wall a reflection signal is formed and is identifiable when reflected from the lateral wellbore. This embodiment of the method may further include receiving the reflection signal, moving the transducer in an axial direction along the wellbore axis, and repeating the steps of generating, receiving, and moving to create a collection of received signals. From the collection of received signals, a reflection from the wall in the lateral wellbore can be identified to estimate where the lateral wellbore intersects with the primary wellbore. The method may further include analyzing fluid in the wellbore for the presence of water and/or gas. Using the sensed water and/or gas and lateral intersection information it can be determined whether the lateral wellbore produces water and/or gas. The tool may further include a bendable sub and the method further may further involve activating the bendable sub so that activating the bendable sub bends a lower portion of the tool into alignment for insertion into a lateral wellbore. The tool may also further include a wellbore seal and the method can further involve inserting the tool into the lateral wellbore and activating the wellbore seal thereby sealing the lateral wellbore from the primary wellbore. The portion of the tool having the wellbore seal can be separated from the remaining portion of the tool and the remaining portion of the tool can be removed from the lateral wellbore thus leaving the portion of the tool having the wellbore seal in the lateral wellbore. 
     Also disclosed herein is a downhole tool insertable into a wellbore, the wellbore having a primary wellbore and a lateral wellbore. Included with the tool is a water and/or gas sensor to sense the presence of any water and/or gas flowing from the lateral wellbore and to determine the intersection of the lateral wellbore to the primary. A bendable orienting sub is included with the tool, where the sub bends a lower portion of the tool relative to an upper portion to enter the lateral wellbore. Another feature includable with the tool is a wellbore seal in the lower portion of the tool, which when activated seals the lateral wellbore. The tool further includes a frangible section that releases the lower portion of the tool from the remaining portion to allow the tool to be retrievable while the wellbore seal remains in the lateral wellbore. The tool may optionally include an acoustic signal transmitting and receiving system that emits acoustical signals that are reflected from a wellbore wall to determine the location of a lateral wellbore. 
     The present disclosure also includes a wellbore system for investigating a wellbore, where the wellbore has a primary well, a lateral well intersecting the primary well, and a wall on the primary well inner periphery and lateral well inner periphery, the system for estimating where the lateral well intersects the primary well. In one embodiment the system has a sonde disposable into the wellbore, an acoustic array provided with the sonde, the array comprising an acoustic transmitter and a corresponding acoustic receiver, the acoustic transmitter positioned so that when it generates an acoustic signal the acoustic signal is directed away from the sonde in a plurality of lateral directions to an adjacent wellbore wall, wherein the acoustic signal contacts the wellbore wall on one of the primary well inner periphery or lateral well inner periphery and reflects from the wellbore wall to form a reflection signal receivable by the acoustic receiver; and a processor in data communication with the array, the processor configured to analyze data communicated from the array to determine if the reflection signal was by the acoustic signal reflecting from the primary wellbore or the lateral wellbore to thereby estimate the location where the lateral wellbore intersects with the primary wellbore. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the features, advantages and objects of the invention, as well as others which will become apparent, may be understood in more detail, more particular description of the invention briefly summarized above may be had by reference to the embodiment thereof which is illustrated in the appended drawings, which form a part of this specification. It is to be noted, however, that the drawings illustrate only a preferred embodiment of the invention and is therefore not to be considered limiting of the invention&#39;s scope as it may admit to other equally effective embodiments. 
         FIG. 1  is a side partial sectional view of a prior art method of deploying a downhole tool into a lateral wellbore. 
         FIG. 2  is a side partial sectional view of an embodiment of a downhole tool described herein disposed in a wellbore. 
         FIGS. 3-5  illustrate the downhole tool in  FIG. 2  entering and plugging a lateral wellbore. 
         FIG. 6  depicts a downhole tool in accordance with the present disclosure sensing within the wellbore. 
         FIG. 7  is an overhead view of the downhole tool of  FIG. 6  in a primary wellbore. 
         FIG. 8  illustrates in overhead view the downhole tool of  FIG. 6  adjacent a lateral wellbore. 
     
    
    
     DETAILED DESCRIPTION 
     Disclosed herein is a method and system for locating lateral well to primary well intersection. Also disclosed herein is a system and method for sensing water and/or gas in wellbore fluid and if the water and/or gas is introduced from a lateral wellbore to a primary wellbore, the system and method identifies the particular lateral wellbore introducing the water and/or gas into the primary wellbore. Further included is a bendable sub for a downhole tool, providing orienting for the tool to enter a lateral wellbore. Also, a seal is included for sealing and blocking a lateral wellbore. 
       FIG. 2  illustrates in side partial sectional view an example of a downhole system  30  for use in the wellbore  2 . The system  30  includes a downhole tool  38  shown deployed on tubing  34  within the primary wellbore  3 . The tubing  34  is supplied from a reel  32  and inserted into the wellbore  2  through a production tree  36  that is affixed on the upper end of the wellbore  2 . Optionally, the tool  38  can be lowered on wireline, slickline, or any other lowering and raising means. Downhole tool  38  includes an outer housing  40  having an outer surface defining a sonde. In the embodiment shown, included with the housing  40  are a sensor  42  for sensing water and/or gas, a lateral detector  44 , an orienting sub  42 , a plug or seal section  48 , and a guide shoe  50 . 
     The sensor  42  analyzes wellbore fluid adjacent the tool  38  for detecting the presence of water and/or gas  22  in the fluid. Sensor  42  results may be available real time to the surface via tubing  34  or other telemetry means. Water and/or gas downhole can be identified by neutron and/or gradiometer logging tools. Optionally, the results can be stored within the sensor  42  or other areas of the housing  40  and retrieved and analyzed at a later time. In the embodiment of  FIG. 2 , the lateral sensor  44  includes an array of acoustic transducers  45 . The acoustic transducers  45  include acoustic transmitters and receivers. Optionally, transducers capable of transmitting and receiving acoustic signals may be included. As will be discussed in more detail below, acoustic signals are generated within the primary wellbore  3  and reflected from the wellbore  2  wall, where receivers within the lateral detector  44  receive the reflected acoustic signal. Signals reflecting from the wellbore wall within the primary wellbore have signatures different from the signatures of signals reflecting from the wellbore wall within the lateral wellbores  5 ,  6 ,  7 . Identifying the position of the lateral detector  44  when receiving acoustic reflections from the wellbore wall in one of the lateral wellbores  5 ,  6 ,  7  provides one method of identifying an intersection I between the lateral wellbores  5 ,  6 ,  7  and the primary wellbore  3 . The wellbore wall can include casing cemented within the borehole. 
     The orienting sub  46  bends or deflects at an angle relative to the tool axis A T . Multiple ways of incorporating a bendable sub  46  are known. Examples include asymmetric sliding sleeves, lined coiled tubing, mechanically activated bendable portion, or hydraulically activated sections. The seal or plug section  48  provides a manner of sealing within a wellbore, such as a lateral wellbore; an example includes an outwardly expanding inflatable plug that seals against a wellbore along its inner circumference. 
     In one example of use, the tool  38  traverses the primary wellbore  3 , while the lateral detector  44  is activated and generating acoustic signals within the wellbore  2 . Analyzing the signal reflections can locate an intersection I between the primary wellbore  3  and one of the lateral wellbores  5 ,  6 ,  7 . Optionally, the sensor  42  may be simultaneously sampling the wellbore fluid and identifying water and/or gas  22  content. As noted above, analysis results for water and/or gas content or a lateral intersection, can be stored within the housing  40  or directed to the surface for real time analysis. A processor  41 , such as an information handling unit, can be employed to conduct the analysis, store the analysis results, provide control commands to communicate the analysis to surface, or any other step of control. 
     As shown in  FIG. 2 , the lateral wellbore  7  includes water and/or gas  22  flowing to the primary wellbore  3 . Correlating the intersection I location with the location where water and/or gas  22  is sensed can identify the lateral wellbore  7  producing the water and/or gas  22 . In one example of use, the tool  38  travels the primary wellbore  3  length to identify lateral to primary wellbore intersections I and water and/or gas presence. The tool  38  travel can be limited to a single in or out sensing/analysis trip, or include additional passes through the wellbore  3  for additional data collection. After identifying the water and/or gas  22  producing lateral wellbore  7 , corrective or remedial action can then be undertaken within the lateral wellbore  7 . Optionally, the sensor  42  can sense the water and/or gas percent in the wellbore fluid in addition to its presence in the wellbore fluid. Based on the mapping step, one or more lateral wellbores can be identified for corrective action. 
       FIG. 3  illustrates in side partial sectional view, the tool  38  of  FIG. 2  being oriented for insertion into the lateral wellbore  7 . Orienting the tool  38  includes bending the tool  38  so its free end may enter the lateral wellbore  7 . The tool  38  may be bent by activating the orienting sub  46   a  into a partial bending configuration, thereby orienting the lower or end of the tool  38  having the guide shoe  50 . The bending step should angle the tool  38  end so the portion below the orienting sub  46   a  can enter the lateral wellbore  7 . This requires a bending angle that considers the angle between the primary wellbore  3  and the lateral wellbore  7  and proper azimuthal direction matching the lateral wellbore  7  entrance. Alignment with the proper azimuthal direction can be from a gyroscope (not shown) or real time acoustic monitoring as described herein. It should be pointed out that tool  38  operation is not limited to insertion into a single lateral wellbore  7 , but instead can be operated in any lateral wellbore. 
       FIG. 4  illustrates the embodiment of  FIG. 3  shown with the tool  38  urged deeper into the lateral wellbore  7 . Also shown in  FIG. 4  is the optional plug section  48  activation; activating the plug section  48  deploys a seal  49  extending from the plug section  48 . The seal  49  radially circumscribes the plug section  48  and projects out to the wellbore wall W I  in the lateral wellbore  7 . The seal  49  is in sealing engagement with the wellbore wall W I  and prevents fluid flow across the plug section  48 . Installing and activating the plug section  48  in the lateral wellbore  7  eliminates water and/or gas  22  contribution from the lateral wellbore  7  into the primary wellbore  3 . 
     The plug section  48  is separatable from the tool  38  by a frangible link  51 , either within the plug section  48  or between the plug section  48  and the remaining portion of the tool  38 . Shown in  FIG. 5  the plug section  48  is separated from the remaining portion of the tool  38  leaving the plug section  48  and guide shoe  50  in the lateral wellbore  7 . The remaining portion of the tool  38  is retrievable from within the primary wellbore  3 . The frangible link  51  can be designed to fail under a pulling shear force. Optionally, an explosive or disintegrating device can be employed for separating the plug section  48  from the tool  38 . 
       FIG. 6  is a side schematic view of an embodiment of the tool  38  within the primary wellbore  3 . Signal paths  52 ,  54  are provided within the wellbore  2  illustrating an example of a seismic signal direction. Path  52  represents a signal from the acoustic transducers  45  directed to the wellbore wall W P  within the primary wellbore  3 . Similarly, path  54  illustrates acoustic signal propagation when directed to the wall W L  within the lateral wellbore. In the example of  FIG. 6 , the lateral wellbore is lateral wellbore  5 . 
       FIG. 7  represents an overhead cutaway view demonstrating an example of signal travel from the sensors  45  and their ensuing reflections from the wellbore wall W P . The sensors  45  are provided at multiple positions around the tool axis A T  within the lateral detector  44 . Although the tool  38  is oriented having its axis A T  set apart from the primary wellbore axis A W , embodiments exist wherein the axes are substantially aligned. In the embodiment of  FIG. 7 , acoustic signals generated within the primary wellbore  3  are represented by arrows  56  shown directed towards the primary wellbore  3  wall W P . The acoustic signals  56  reflect from the wall W P  and form a reflected signal  58 . In the embodiment shown, the acoustic signals  56  are oriented away from the tool  38  in a direction perpendicular to the axis A T . Consequently, the reflected signal  58  propagates in a direction substantially along the path of the acoustic signal  58  and towards the tool  38 . However, other embodiments are available, wherein the acoustic path  56  extends along a path generally oblique to one of the tool axis A T , the well axis A W , or both. 
     By estimating the fluid properties within the well  2 , the sound speed within the wellbore fluid can be estimated, thereby providing an estimated value of distance between each of the sensors  45  and the wellbore wall W P . These distances can be calculated within the processor  41  optionally provided within the tool  38 , stored within the tool  38 , or communicated to the surface for real time analysis. Subsequent cycles of acoustic signal generation and detection can be performed at different depths within the wellbore  2 . This can be an incremental or a continuous fashion. It is believed it is well within the capabilities skilled in the art to devise a suitable method of disposing the tool  38  within the wellbore while making acoustic estimations within the wellbore. Using the data collected the wellbore dimensions adjacent the tool  38  can be estimated. 
       FIG. 8  illustrates an overhead schematic view of the tool  38  in the wellbore, wherein the lateral detector  44  is disposed adjacent the intersection I to form the acoustic path  54 . As shown, generated signals  56  directed towards the wellbore wall W P  and the primary wellbore will generate reflected signals  58  similar to those of  FIG. 7 , both in direction and arrival time to the sensor  45 . However, generated signals  56   a,    56   b  directed towards the intersection, are shown extending past the line representing the primary wellbore wall W P  into the wellbore wall lining the lateral wellbore  5 . The reflected signals  58   a,    58   b  produced by reflecting signals  56   a,    56   b  on the wellbore wall W L  within the lateral wellbore  5  will, according to Snell&#39;s law, have a primary component directed at an angle with respect to the sensor  45  that generated the signals  56   a,    56   b.  Accordingly, magnitude and travel time detected for the reflected signals  58   a,    58   b  from the lateral wellbore wall W L  will differ from the travel time and signal magnitude a signal reflected from the primary wellbore wall W P . As such, the location of the intersection I between the primary wellbore  3  and any of the lateral wellbores may be identified through analyzing reflected acoustic signal data. 
     Optionally, a database of reflected signal data can be created empirically, through actual recording when disposing a tool downhole, as well as during the particular operation when attempting to identify a wellbore lateral. By correlating the response of acoustics within the intersection area with the measured depth of the tool  38  can provide an estimated location of the intersection I within the wellbore  2 . 
     Alternative embodiments include a single sensor  45  on the tool  38 , wherein the tool may be rotated during use. Optionally, in a pair of transducers, such as an acoustic transmitter and an acoustic receiver may be included on a tool at a single location. Although sensors  45  are shown in six locations around the tool  38 , multiple other embodiments exist having less or more than six locations for sensors on a tool  38 . 
     In an alternative embodiment, the downhole tool  38  may include a lateral detector  44 . In other embodiments one or more additional features described above, in any combination, can be included with the lateral detector  44 , such as the processor  41 , the sensor  42 , the orienting sub  46 , the plug section  48 , and the guide shoe  50 . Embodiments of the tool  38  may alternatively include wellbore exploration devices, perforating devices, and fracturing systems. 
     While the invention has been shown or described in only some 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.

Summary:
A tool used for treating and/or maintaining a wellbore that includes acoustic transducers for locating a lateral wellbore that intersects a primary wellbore. The tool includes a sensor to sense water and/or gas, and if the water and/or gas enters the primary wellbore from a lateral wellbore, the lateral to primary intersection can be identified by correlating information from the sensor and acoustic transducers. If needed, the tool can be used to plug the water and/or gas supplying lateral wellbore. The tool may include a bendable sub portion for orienting a portion of the tool for insertion into the lateral wellbore and a plug section for plugging the lateral wellbore after insertion therein.