Abstract:
Embodiments of a method and apparatus for locating lateral wellbores extending from a main wellbore includes a caliper sensing tool having spring actuated calipers extending radially therefrom. Each of the calipers is connected to a sensor, such as a linear variable displacement sensor, that is used to calculate the radial extension distance of the respective caliper. When the tool is inserted through a wellbore and moves past a lateral wellbore opening, the calipers extend into the lateral wellbore opening. The extension, as well as contact with the surfaces of the lateral wellbore, are used to determine the wellbore depth location and azimuthal direction of the lateral wellbore. A deflectable steering arm is operable to be selectively steered into the lateral opening to facilitate access to the lateral wellbore for logging or intervention purposes.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to and the benefit of U.S. Provisional Patent Application No. 61/727,215 titled “Caliper Steerable Tool for Lateral Sensing and Accessing,” filed on Nov. 16, 2012, the disclosure of which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates in general to wellbore operations and in particular to locating lateral wellbores. 
         [0004]    2. Description of the Related Art 
         [0005]    In the field known as well logging, wells are examined using mechanical, electrical and radioactive tools called logging tools. The logging tools are inserted into wellbores that penetrate into reservoirs. The logging tools inserted into wellbores record certain physical measurements that are interpreted to provide a description of petrophysical properties related to the wellbore or the reservoir it penetrates. Well drilling techniques now include multilateral horizontal wells wherein horizontal wells have many branches called laterals. Those laterals branch out from the main bore like tree roots. Generally those branches are drilled using special drilling steering devices. Those laterals are generally not easily accessible by logging tools. 
         [0006]    Existing sensing tools used to find laterals in multilateral wells use electronic sensors such as magnetic and ultrasonic sensors. There is a great deal of error associated with those sensors so multiple scanning runs are required, with the resulting signals being fed into an algorithm to provide a statistical interpretation of where the lateral window can be found. 
       SUMMARY OF THE INVENTION 
       [0007]    In embodiments of a lateral finding tool and method of operating the tool, the tool is used to find lateral wellbores that branch off of a main wellbore. Embodiments of lateral finding tools employ a set of spring-actuated calipers connected to linear variable displacement transducers (“LVDT”) which provide an electrical signal when the caliper extends radially such that a radial measurement of the wellbore diameter is determinable from the electrical signal. The tool can also be equipped with a steerable arm to steer the bottom hole assembly (“BHA”) into laterals to access them for logging and intervention purposes. 
         [0008]    In embodiments, calipers extend radially out of the tool providing a measurement of the internal diameter of the wellbore and thus provide a well profile measuring capability. The calipers are distributed radially about the circumference of the tool. In some embodiments, each of 16 calipers are spaced apart by a radial angle of 22.5 degrees such that 16*22.5=360 degrees for a full radial coverage. The LVDTs are calibrated such that they measure the distance the calipers radially extend out from the logging tool body. The radial distance spanned by the calipers is the diameter of the wellbore. As the tool moves past any lateral windows, the LVDTs will read an increase in the wellbore diameter and thus will find the lateral when its window is reached. 
         [0009]    Embodiments can also include a magnetic sensor. The magnetic sensor is based on magnetic flux sensing that can sense the presence of well casing. When the tool passes into a wellbore open hole section, this magnetic sensor will, for example, not give any signal so as to indicate the absence of well casing. In such embodiments, when the tool is in the open hole section of the well, there will no magnetic effect due to the absence of metal. Embodiments of the tool can be equipped with a deflection arm, acting like a steering device to help the logging assembly access the lateral. 
         [0010]    The tool provides a mechanism to find and access laterals in maximum reservoir contact wells (MRC). In an exemplary embodiment, the tool is equipped with 16 caliper fingers extending radially from the tool. The fingers (calipers) can be spring-actuated and are connected to electronic devices such as LVDT&#39;s to provide an indication of the radial extension of the 16 fingers. Each finger with its azimuthal location can provide a precise profile of the well. 
         [0011]    In a well completion report, lateral depths are normally provided. Comparing the lateral depths in this report with the measurement provided by embodiments of the tool can confirm the location depth of a lateral. The operator can then selectively activate the steerable arm into the azimuthal direction of the lateral to access it and direct the logging tools into the lateral. 
         [0012]    Embodiments of the caliper sensing tool can avoid error resulting from sensing devices such as ultrasonic sensors or pressure sensors because the sensing it employs is purely mechanical based on the fingers extending radially out of the tool. The caliper fingers can be readily calibrated during the function of the tool in the field and before it is inserted into the well under examination. 
         [0013]    Embodiments of the lateral finding and accessing tool employ mechanical arms called calipers to measure the internal diameter of a well and any physical changes to its cylindrical shape. In the case of a well having multilateral branches known as laterals, the tool can be used to locate a lateral branching from the main bore. In an embodiment, the tool employs 16 spring-actuated calipers radially extending out of the tool and distributed around the circumference of the tool such that each caliper occupies a radial angle of 22.5 deg. The 16 calipers thus cover the 360 degrees around the cylindrical well. The calipers can connect to LVDT transducers, which are electrical potentiometers that will change resistance when the caliper extends; such that they will provide data from which the extension of each caliper arm is ascertainable. The change in resistance sensed by the LVDT is converted into a radial measurement of the radius of the well. As the tool with those calipers passes by a lateral, an increase in the caliper radial extension will be detected by the LVDTs, thus providing a profile log of the well and its laterals. A plurality of calipers that is a subset of all of the calipers can extend into the opening of the lateral bore. The plurality of calipers that have extended into the lateral bore can indicate the direction the lateral is in. Furthermore, because each of the calipers that extend into the lateral bore may contact a portion of the lateral bore, the profile of that portion of the lateral bore can be determined. The operator then can steer the steerable arm into that direction to allow the BHA to further access the lateral. 
         [0014]    Embodiments of a method for detecting lateral bores from a main wellbore of a well include the steps of providing a caliper tool into the main wellbore, the caliper tool including a head having a first end, a second end, and a plurality of calipers extending radially therefrom; moving the caliper tool axially through the wellbore on a deployment member, the deployment member being connected to the first end of the head; detecting an inner diameter surface of the wellbore with the calipers by ascertaining the distance that each of the calipers extend from the head; detecting a lateral opening in the wellbore with at least one of the plurality calipers, the lateral opening being an opening of a lateral bore branching off of the wellbore; and determining the distance from the surface of the earth to the lateral opening. 
         [0015]    In embodiments, each of the calipers is operatively connected to a measurement device, and the method further includes the step of ascertaining the radial distance by which each of the calipers extends from the head of the caliper tool with the measurement devices. In embodiments, each one of the plurality of calipers comprises a pair of segments, and each segment of the pair of segments includes a radially-inner end pivotally coupled to the head of the caliper tool and radially-outer end coupled to a flexible joint defined between the pair of segments, and the step of ascertaining the radial distance by which each one of the plurality of calipers extends from the head of the caliper tool comprises detecting a configuration of at least one of the radially-inner ends of the pair of segments with respect to the head of the caliper tool. In embodiments, the plurality of measurement devices comprises a plurality of linear position sensors disposed axially along the head of the caliper tool such that each linear position sensor is operable to detect an axial position of at least one of the radially-inner ends of the pair of segments along the head of the caliper tool, and the step of ascertaining the radial distance by which each one of the plurality of calipers extends from the head of the caliper tool comprises calculating the radial distance with the axial position detected by the respective linear position sensor. In embodiments, the linear position sensors can comprise linear variable displacement transducers. 
         [0016]    In embodiments, each of the plurality of calipers can be biased to a radially outward position, and the step of detecting the lateral opening in the main wellbore includes detecting a movement of at least one of the plurality of calipers from a radially inward position toward the radially outward position as the at least one of the plurality of calipers extends into the lateral opening. In embodiments, the step of detecting the lateral opening in the main wellbore includes detecting an initial contact of the at least one of the plurality of calipers that extends into the lateral opening with a surface of the lateral bore and subsequently detecting at least one of the plurality of calipers that extends into the lateral opening is free of contact with the surface of the lateral bore. In embodiments, the method further includes the step of determining the direction of the lateral bore, relative to the main wellbore, based on the radial or circumferential position of at least one of the plurality calipers that extends into the lateral opening. 
         [0017]    In embodiments, the method includes the steps of advancing the caliper tool past the lateral opening and determining a profile of the lateral bore from movements of at least one of the plurality of calipers as the caliper tool advances past the lateral opening. In embodiments each of the plurality of calipers extends from the head a radial distance greater than a radius of the main wellbore when in an unconstrained state. In embodiments, the method includes the step of creating a profile log of the main wellbore and the lateral bore. In embodiments, the caliper tool further includes a centralizer operable to maintain the caliper tool centered in the main wellbore, and the step of detecting an inner diameter surface of the main wellbore includes employing the centralizer to maintain the caliper tool centered in the wellbore so that each of the plurality of calipers extends radially from the head substantially no more than the rest of the plurality of calipers. 
         [0018]    In embodiments, the caliper tool includes a steering arm connected to the second end of the head and selectively operable to be angled relative to head, and the method further includes the steps of positioning the caliper tool so that an end of the steering arm is located concentrically with the lateral opening and angling the steering arm in the direction of the lateral opening. In embodiments, the method includes the step of inserting the caliper tool into the lateral opening by axially advancing the deployment member through the main wellbore. 
         [0019]    In embodiments, the caliper tool further includes a magnetic sensor, and the method further includes the step of detecting, with the magnetic sensor, the presence of wellbore casing. In embodiments, the method includes the steps of advancing the deployment member through the main wellbore until the magnetic sensor is disposed axially beyond an end of the wellbore casing, detecting, with the magnetic sensor, the absence the wellbore casing, and determining the distance from the surface of the earth to the end of the wellbore casing. 
         [0020]    Embodiments of an apparatus for detecting lateral wellbores include a tool body having a first end and a second end; a plurality of calipers extending radially from an outer diameter of the tool body, each of the plurality of calipers including a first segment having a radially-inner end with a fixed radial position with respect to the outer diameter of the tool body and a radially-outer end operable to move in a radial direction with respect to the outer diameter of the tool body, a second segment having an axially-movable radially-inner end with a fixed radial position with respect to the outer diameter of the tool body and a radially-outer end operable to move in a radial direction with respect to the outer diameter of the tool body, and a flexible joint coupling the radially-outer end of the first segment to the radially-outer end of the second segment such that the flexible joint is movable from a radially outward position to a radially inward position with respect to the outer diameter of the tool body in response to axial movement of the of the axially-movable radially-inner end of the second segment. The flexible joint defines a radially outermost portion of the respective caliper. The apparatus also includes a biasing member operatively coupled to the flexible joint of each of the calipers to bias the flexible joint to the radially outward position; at least one sensor operatively coupled to the axially-movable radially-inner end of the second segment of each of the calipers that is operable to sense the axial position of the axially-movable radially-inner end of the second segment of each of the calipers relative to the tool body; a processor operably connected to the at least one sensor and operable to calculate a radial extension distance of each of the plurality of calipers in response to a data signal received from each of the sensors; a steering arm operably connected to the first end of the tool body and a connector operable to couple the second end of the tool body to an insertion member. 
         [0021]    In embodiments, the plurality of calipers comprises at least 16 calipers. In embodiments, the apparatus further includes a centralizer that is operable to radially center the tool body in a wellbore. In some embodiments, the steering arm includes a tip at one end and a positioner at another end, the positioner being operable to change the angle of the steering arm relative to the head along at least two axes. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    So that the manner in which the above-recited features, aspects and advantages of the invention, as well as others that will become apparent, are attained and can be understood in detail, more particular description of the invention briefly summarized above can be had by reference to the embodiments thereof that are illustrated in the drawings that form a part of this specification. It is to be noted, however, that the appended drawings illustrate some embodiments of the invention and are, therefore, not to be considered limiting of the invention&#39;s scope, for the invention can admit to other equally effective embodiments. 
           [0023]      FIG. 1  is a side sectional environmental view of a wellbore with an embodiment of a sensing tool in a wellbore. 
           [0024]      FIG. 2  is a sectional side view block diagram of the sensing tool of  FIG. 1 . 
           [0025]      FIG. 3  is a perspective view of the sensing tool of  FIG. 1 . 
           [0026]      FIG. 4  is an end view of the sensing tool of  FIG. 2  taken along the  4 - 4  line. 
           [0027]      FIG. 5  is a sectional end view of the intersection of the horizontal wellbore and the lateral wellbore with the sensing tool positioned therein, taken along the  5 - 5  line of  FIG. 1 . 
           [0028]      FIG. 6  is a sectional top view of the sensing tool of  FIG. 1 , showing a caliper in contact with the lateral wellbore. 
           [0029]      FIG. 7  is a sectional top view of the sensing tool of  FIG. 1 , showing the caliper after moving out of contact with the lateral wellbore. 
           [0030]      FIG. 8  is a sectional top view of the sensing tool of  FIG. 1 , showing the actuator arm positioned in the mouth of the lateral wellbore. 
           [0031]      FIGS. 9A ,  9 B, and  9 C are environmental views of an exemplary display of the data produced by the sensing tool of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0032]      FIG. 1  shows wellbore  100 , which includes a horizontal wellbore  102 . Sensing tool  104  is inserted or deployed into wellbore  102 , and can locate lateral branches of the wellbore such as lateral  106 . While horizontal wellbore  102  and lateral  106  are shown for descriptive purposes, sensing tool  104  can be used in other types of deviated wells and can be used to detect other types of branch wellbores that extend from a wellbore. Tool  104  can be inserted or deployed into wellbore  100  by a variety of techniques, including, for example, on tubing  108 . One or more other tools  110  can be connected to tubing  108  and tool  104 , the one or more tools  110  and tool  104  defining a bottom hole assembly (“BHA”). Tool  110  can include, for example, a packer deployment tool for sealing off a lateral wellbore. Tool  110  can include, for example, a deviation survey sub. Truck  112  is shown deploying tubing  108 , but, as one of skill in the art will appreciate, other techniques can be used to deploy tool  104 . 
         [0033]      FIGS. 2 and 3  show an embodiment of sensing tool  104 . Sensing tool  104  includes a tool body  116  having a front end  118  and a back end  120 . Steering arm  122  is connected to body  116  at front end  118 . A deployment member, such as tubing  108 , is connected to body  116  at back end  120 . The deployment member can be any device suitable for running sensing tool  104  into the wellbore. As one of ordinary skill will understand, the deployment member can be, for example, tubing, a drill string or running string, or a cable. A plurality of calipers  126  extend radially from tool body  116 . Calipers  126  include two or more segments  126   a  and  126   b  that are connected by flexible joint  128 . Flexible joint  128  can include hinge or a spring connected to a radially-outer end of each of segment  126   a  and  126   b . In embodiments, each caliper  126  is a single, monolithic member that can flex at flexible joint  128 . 
         [0034]    Radially-inner end  130  of segment  126   b  is connected to body  116  at pivot joint  132 . Pivot joint  132  is radially constrained such that radially-inner end  130  has a fixed radial position with respect to body  116 . Radially-inner end  134  of segment  126   a  is connected to slide connector  136 . Slide connector  136  radially constrains radially-inner end  134  of segment  126   a  with respect to body  116  and allows radially-inner end  134  of segment  126   a  to slide axially along a portion of body  116 . Slide connector  136  can include, for example, a sleeve that slides along a shaft, a bearing that slides in a track, or another connection that provides for linear movement of radially-inner end  134  relative to body  116 . In embodiments, slide connector  136  includes a pivot point that allows radially-inner end  134  of segment  126   a  to pivot relative to body  116 . Either or both of pivot joint  132  and slide connector  136  hold caliper  126  so that flexible joint  128  is movable between a radially outward position to a radially inward position with respect to an outer diameter of body  116  in response to axial movement of radially-inner end  134  of segment  126   a . Conversely, radially-inner end  134  of segment  126   a  is axially movable in response to radial movement flexible joint  128 . Flexible joint  128  can move in and out, radially, relative to body  116 , and defines a radially outermost portion of caliper  126  regardless of the axial position of radially-inner end  134  of segment  126   a . The pivot joint  132  and slide connector  136  prevent caliper  126  from rotating circumferentially relative to body  116 . Slide connector  136  can include a biasing member such as spring  138  to urge radially-inner end  134  axially toward radially-inner end  130 , and thereby urge flexible joint  128  to a radially outward position with respect to body  116 . Other biasing configurations can be employed such as, for example, a spring (not shown) at flexible joint  128  that draws segments  126   a  and  126   b  together, or a spring at radially-inner end  130  that urges segment  126   b  radially away from body  116 . Any of these configurations cause caliper  126  to be biased toward a configuration of maximum extension when in an unrestrained state. 
         [0035]    By sliding along body  116  with slide connector  136 , radially-inner end  134  of caliper  126  moves closer to radially-inner end  130 . As the two radially-inner ends  134 ,  130  move closer to each other, flexible joint  128  moves radially outward from body  116 . When the two radially-inner ends  134 ,  130  of caliper  126  move axially apart from each other, flexible joint  128  moves radially inward toward body  116 . The extension distance  140  of caliper  126 , from body  116  is thus variable and is defined as the radial distance from body  116  to the tip of flexible joint  128 . Extension distance  140  is ascertainable by the length of each segment  126   a ,  126   b  of caliper  126  and by the axial travel distance of slide connector  136  as described in greater detail below. 
         [0036]    As best shown in  FIGS. 3 and 4 , a plurality of calipers  126  are spaced apart around the circumference of sensing tool  104 . In embodiments, 16 calipers  126  are evenly spaced apart around the circumference of sensing tool  104 , such that each caliper  126  occupies a radial angle of 22.5 degrees. More or fewer calipers  126  can be used, although using fewer calipers can result in a degradation of the quality of the profile image determined by the sensing tool  104 . 
         [0037]    Referring back to  FIG. 2 , sensing tool  104  includes position sensors  142  for determining the axial location of radially-inner end  134  relative to body  116 . Position sensors  142  are linear position sensors disposed axially along body  116 . By determining the axial location of radially-inner end  134  of a particular caliper  126 , the extension distance  140  can be determined for that particular caliper  126 . For example, in embodiments wherein segments  126   a  and  126   b  are substantially rigid with a fixed length, extension distance  140  is readily ascertainable by calculation. Extension distance  140  represents a height of a triangle with a base formed by a portion of body  116  disposed axially between pivot joint  132  and shuttle  144 , and two sides of the triangle are formed by segments  126   a  and  126   b . With the position of the shuttle  144 , and thus the position of radially-inner end  134  coupled thereto, determinable by position sensor  142 , the length of the base of the triangle is known and can be employed together with the known lengths of the sides (lengths of segments  126   a  and  126   b ) to calculate the height or extension distance  140  as will be appreciated by those skilled in the art. 
         [0038]    Calculating extension distance  140  in this manner permits position sensors  142  to be housed within slots defined in body  116  rather than being disposed at flexible joint  128  or at another exposed location such as pivot joint  132 , for example. Sensors  142  and associated wiring, power sources (not shown), etc. are thus relatively protected from the wellbore environment. Position sensors  142  can include, for example, a linear variable displacement transducer (“LVDT”). An LVDT is an electrical potentiometer that will change resistance based on the position of a member that moves within, or adjacent to, the LVTD. In the embodiment shown, at least a portion of shuttle  144  moves within sensor  142 . As caliper  126  moves from the inward position to the extended position, shuttle  144  moves through sensor  142 , changing the resistance of sensor  142 . A signal from sensor  142 , which reflects the position of shuttle  144  within sensor  142 , is sent to computer  150 . As one of skill in the art will appreciate, data signals from each caliper  126  can be analog or can be converted to discrete digital signals. Computer  150  can include one or more of a computer, a processor or microprocessor, a memory storage unit, and a program product stored in a tangible medium. 
         [0039]    In other embodiments (not shown) alternate types of sensors may be employed to detect a configuration of radially-inner end  134  of segment  126   a  or radially-inner end  130  of segment  126   b  to ascertain extension distance  140 . For example, an angle that the radially-inner ends  130 ,  134  define with respect to body  116  may be sensed by appropriate sensors housed within body  116 . 
         [0040]    In the embodiment depicted in  FIG. 2 , computer  150  receives data from each of the plurality of calipers  126  on sensing tool  104 , and can determine the extension distance of each caliper  126  based on the data. By combining that position data, computer  150  can determine the shape of the wellbore, such as horizontal wellbore  102 , at a given axial position. As sensing tool  104  is moved through the wellbore, each caliper  126  sends data signals to computer  150 . The data signals, over time, is called a trace. Computer  150  can use the trace from each caliper  126  to determine the shape of wellbore  150  over the axial distance travelled by sensing tool  104 . Computer  150  can be in data communication with display  152  by, for example, cables, wireless data transfer, or a combination thereof. Display  152 , which can be a monitor having a screen, can be located on the surface of the earth for presenting data regarding the wellbore shape to an operator. 
         [0041]    Referring to  FIGS. 2 and 3 , steering arm  122  extends from front end  118  of body  116 . Steering arm  122  can be used to deflect sensing tool  104  into a lateral wellbore. Steering arm  122  can be selectively angled relative to the axis of body  116 . In embodiments, steering arm  122  can be selectively rotated about the axis of body  116 . By combining a selective angle with rotation, steering arm  122  can be rotated and angled to point in a particular direction offset from the axis of body  116 . Other techniques can be used to selectively point steering arm  122  in a particular direction relative to the axis of body  116 . 
         [0042]    The length of steering arm  122  can be greater than the radius of wellbore  100 , or at least the portion of wellbore  100  in which sensing tool  104  is expected to need to enter a lateral wellbore  106 . The length of steering arm  122  can be greater than the diameter of wellbore  100 , or at least the portion of wellbore  100  in which sensing tool  104  is expected to need to enter a lateral wellbore  106 . 
         [0043]    Embodiments can also include a magnetic sensor  158 . The magnetic sensor  158  can be a magnetic flux sensor that can sense the presence or absence of wellbore casing. When the tool  104  passes into a wellbore open hole section, wherein no casing is present, magnetic sensor  158  will, for example, not give any signal so as to indicate the absence of well casing. In such embodiments, when the tool  104  is in the open hole section of the well, there will no magnetic effect due to the absence of metal. The magnetic sensor  158  may be employed to determine a distance from the surface of the earth to an end of the wellbore casing. By detecting the wellbore casing with magnetic sensor  158 , and then advancing tubing  108  or other deployment member until magnetic sensor is disposed axially beyond an end of the wellbore casing, the point at which magnetic sensor  158  detects the absence the wellbore casing can be noted, and the distance from the surface of the earth to the end of the casing can be determined. 
         [0044]    In embodiments of the caliper sensor, the tool will provide an immediate and affirmative indication of the lateral depth location, length and angle relative to well azimuth.  FIG. 5  shows tool  104  at the intersection of horizontal wellbore  102  and lateral  106 . Calipers  126  extend radially from body  116 , and are restrained by the inner diameter surfaces of horizontal wellbore  102 . Some of the calipers  126 , identified as calipers  126 ′, extend through the opening through the sidewall of horizontal wellbore  102 , into lateral  106 . As shown in  FIG. 5 , calipers  126  have an extension distance  140  ( FIG. 2 ) that is greater than the distance from body  116 , when body  116  is generally centered in horizontal wellbore  102 , to an inner diameter surface of lateral  106 . Because there are multiple calipers  126 ′ in contact with the inner diameter surface of lateral  106 , a profile of that portion of lateral  106  can be determined. The trace of each caliper  126  can indicate the location and direction of a lateral  106 . Indeed, sensing tool  104  can determine the angle and radial location at which lateral  106  is drilled, relative to the main horizontal wellbore  102 , as well as the radial location of the lateral opening within the wellbore. 
         [0045]      FIGS. 6 and 7  show a top view of sensing tool  104  moving past an intersection between lateral  106  and horizontal wellbore  102 . As sensing tool  104  moves through horizontal wellbore  102 , calipers  126 ′ are in contact with the contacted portion  162  of the inner diameter surface of lateral  106 .  FIG. 7  shows sensing tool  104  in a position wherein the distance from body  116  to a portion  164  of lateral  106  is greater than the extension distance  140  of calipers  126 ′. Calipers  126 ′ no longer contact a surface of lateral  106 . The condition that calipers  126 ′ no longer contact a surface of lateral  106  is sensed by position sensors  142  ( FIG. 2 ) as the axial position of radially-inner end  134  corresponding to caliper  126 ′ in a relaxed state is sensed. Caliper  126  extends only until it contacts the inner diameter surface of horizontal wellbore  102 . In embodiments, tool  104  can include a centralizer  170  ( FIG. 6 ). Centralizer  170  can concentrically position tool  104  at or near the axis of the wellbore in which it is located. In embodiments, the spring bias on each caliper  126  can be great enough that the calipers  126  urge tool  104  toward the axial center of the wellbore and, thus, function as a centralizer. 
         [0046]      FIG. 8  shows how sensing tool  104  can be maneuvered into lateral  106 . After detecting the location of lateral  106  from horizontal wellbore  102 , sensing tool  104  is moved, by tubing  108 , until the tip of steering arm  122  is axially adjacent to the opening of lateral  106 . Tubing  108  can push or pull sensing tool  104 , depending on whether sensing tool  104  is positioned before or after lateral  106 , respectively. With the tip of steering arm  122  axially adjacent to the opening of lateral  106 , steering arm  122  is positioned such that at least the tip of steering arm  122  enters lateral  106 . In embodiments, steering arm  122  can be rotated toward lateral  106 , and then angled until it enters lateral  106 . Tubing  108  can then push sensing tool  104  further into the wellbore. As steering arm  122  contacts the inner diameter surface of lateral  106 , it causes front end  118  of sensing tool  104  to move toward lateral  106 . As sensing tool  104  is advanced further, sensing tool  104  enters lateral  106 , and proceeds to move through lateral  106 . Calipers  126  can then be used to sense the profile of lateral  106 . 
         [0047]    In embodiments wherein tool  110  includes a deviation survey sub, the deviation survey sub can be inserted into the lateral and provide the deviation angle of the lateral and the well with the vertical direction. The deviation angle and vertical direction can be used as a signature for the lateral. In embodiments, each lateral can have a deviation and vertical direction that is different from the deviation and vertical direction of any other lateral in the same well. Embodiments of a method for detecting lateral wellbores can include the steps of using tool  104  to determine the location of the lateral wellbore, using steering arm  122  to guide tool  104  into the lateral wellbore, and then using a survey sub to provide a deviation survey, the deviation survey then being used to confirm which lateral was entered by the BHA. 
         [0048]      FIGS. 9A ,  9 B, and  9 C show exemplary depictions of what an operator might see on display  152 , as determined from the data from tool  104 . The data indicates the relative position of the tip of each caliper  126 , as determined by sensors  142  and processed by computer  150  ( FIG. 2 ). The positions of the tip of each caliper  126  can be used to interpolate the wellbore profile at a given wellbore depth. Since tubing  108  extends from the tool  104  to the surface of the earth, by measuring or otherwise determining a length of tubing  108  that is inserted into wellbore  100 , the precise depth of tool  104  is determinable. When the tool  104  is at a location where a lateral opening is detected, a distance from the surface of the earth to the lateral opening is determinable from the precise depth of the tool  104 .  FIG. 9A  shows an exemplary wellbore profile determined from sensor  142  data, showing a generally cylindrical wellbore  160  at depth X, with no lateral wellbore intersection.  FIG. 9B  shows an exemplary wellbore profile determined from sensor  142  data, showing the intersection of horizontal wellbore  162  and lateral  164 , the intersection being located at depth Y.  FIG. 9C  shows an exemplary wellbore profile determined from sensor  142  data, showing the intersection of horizontal wellbore  162  and lateral  164 , after tool  104  is advanced further to depth Z, where Y&gt;X and Z&gt;Y. Note that the display shows the profile of the portion of lateral  106  in contact with calipers  126 . The data from tool  104  can be used to create a profile log of the main bore and, by steering tool  104  into lateral  106 , tool  104  can provide data to create a profile log of lateral  106 . The profile log may contain data related to extension distance  140  for each of the plurality of calipers at each one of a plurality of incremental depths, for example. Furthermore, the precise depth, location, and direction of lateral  106  can be determined and included in a profile log. 
         [0049]    Although the present invention has been described in detail, it should be understood that various changes, substitutions, and alterations can be made hereupon without departing from the principle and scope of the invention. Accordingly, the scope of the present invention should be determined by the following claims and their appropriate legal equivalents. 
         [0050]    The singular forms “a”, “an” and “the” include plural referents, unless the context clearly dictates otherwise. 
         [0051]    Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur. 
         [0052]    Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within the said range. 
         [0053]    Throughout this application, where patents or publications are referenced, the disclosures of these references in their entireties are intended to be incorporated by reference into this application, in order to more fully describe the state of the art to which the invention pertains, except when these reference contradict the statements made herein.