Abstract:
In some general aspects, methods for intersecting a first, cased well bore include drilling a second well bore that has a distal end proximal to the first, cased well bore to be intersected, disposing a mill guiding device in the second well bore near a casing of the first, cased well bore, the mill guiding device being configured to direct a mill of a milling assembly away from a central axis of the second well bore and towards the first, cased well bore, inserting the milling assembly into the second well bore, operating the mill of the mill assembly and guiding the milling assembly along the mill guide and into the casing of the first well bore, and removing material from the casing of the first well bore until the first, cased well bore and the second well bore are fluidly connected.

Description:
TECHNICAL FIELD 
       [0001]    This disclosure relates to a method of intersecting a first well bore by a second well bore and plugging methods for the first well bore. 
       BACKGROUND 
       [0002]    Well bores can be drilled into the earth to tap into underground reservoirs of oil or gas. Such well bores can be lined with a casing (e.g., a metal casing) to add structural stability to the well bores. Well bores are typically abandoned after use. In some cases, a well bore may be abandoned and closed after the volume of oil or gas produced by the well drops below suitably economical levels. Alternatively, in some cases, a well bore is abandoned and closed as a result of a loss of control (blowout) in a well bore. Different regulatory bodies have different requirements for such abandoning operations. Some regulatory bodies require that the abandoned well bore be plugged (e.g., with cement plugs). 
       SUMMARY 
       [0003]    The present disclosure relates methods and systems for intersecting well bores. In a general aspect, a method for intersecting a first, cased well bore includes drilling a second well bore that has a distal end proximal to the first, cased well bore to be intersected, disposing a mill guiding device in the second well bore near a casing of the first, cased well bore, the mill guiding device being configured to direct a mill of a milling assembly away from a central axis of the second well bore and towards the first, cased well bore, inserting the milling assembly into the second well bore, operating the mill of the mill assembly and guiding the milling assembly along the mill guide and into the casing of the first well bore, and removing material from the casing of the first well bore until the first, cased well bore and the second well bore are fluidly connected. 
         [0004]    In another general aspect, a method for intersecting a first, cased well bore includes forming a second well bore that extends to a region of the first, cased well bore to be intersected, arranging a mill guiding device in the second well bore near a casing coupling of a casing of the first, cased well bore, inserting a milling assembly into the second well bore, guiding the milling assembly along the mill guiding device and operating a mill of the mill assembly so that the mill first removes material from an upper surface of the casing coupling, and removing material from the casing coupling and the adjacent casing until the first, cased well bore and the second well bore are fluidly connected. 
         [0005]    In another general aspect, a method for intersecting a first, cased well bore includes forming a second well bore that extends to a region of the first, cased well bore to be intersected, inserting a milling assembly into the second well bore, where the milling assembly has a mill guide, a mill, and a mill alignment device to align the mill and the mill guide as the mill advances along the mill guide, operating the mill and guiding the mill along the mill guide and into a casing of the first, cased well bore, and removing material from the casing until the first, cased well bore and the second well bore are fluidly connected. 
         [0006]    In more specific aspects, the methods may further include removing the milling assembly from the second well bore. 
         [0007]    The methods may further include inserting a plugging material into the first, cased well bore from the second well bore to form an obstruction. In some cases, the plugging material may include cement. In some cases, the obstruction limits an amount of fluid that can pass through the first, cased well bore. In some cases, the fluid is a gas. 
         [0008]    The methods may further include running and setting an anchor packer assembly in the second well bore below the mill guiding device. 
         [0009]    Disposing the mill guiding device may include running and positioning the mill using a drill string. 
         [0010]    The mill guiding device may include a wedge-like member that is arranged in the second well bore to force the mill towards the casing of the first well bore as the mill is inserted into the second well bore. 
         [0011]    The milling assembly may include the mill guiding device and the mill guiding device may include a wedge-like mill guiding device that is arranged in the second well bore to force the mill towards the casing of the first well bore as the mill is inserted into the second well bore. 
         [0012]    The mill may include a rotating drill bit. In some cases, the rotating drill bit may be powered hydraulically. 
         [0013]    The methods may further include running and setting an anchor packer assembly in the second well bore below the mill guide. 
         [0014]    The mill alignment device may include one or more grooved rails disposed longitudinally along the mill guiding device that force the mill towards the casing as the mill is inserted into the second well bore. The mill may include one or more tabs that are sized to slide within the grooved rails. In some cases, as the mill moves along the mill guide device, the grooved guide rails limit the extent to which the mill may move transverse to the longitudinal direction of the mill guide. 
         [0015]    In another general aspect, a method for intersecting a first, cased well bore includes forming a second well bore that extends to a region of the first, cased well bore to be intersected, inserting a laser tool assembly into the second well bore and aligning the laser tool assembly with the region of the first, cased well bored to be obstructed, operating the laser tool assembly and forming an opening in a casing of the first, cased well bore, and removing material from the casing until the first, cased well bore and the second well bore are fluidly connected. 
         [0016]    In more specific aspects, the method may further include removing the laser tool assembly from the second well bore. 
         [0017]    The laser tool assembly may include a laser perforator having a laser beam generator that generates a laser beam, and a focusing array through which the laser beam passes. 
         [0018]    In another general aspect, a system for intersecting a first, cased well bore includes a drilling assembly that is configured to drill a second well bore having a distal end proximal to the first, cased well bore, a milling assembly, and a mill guiding device. The drilling assembly includes a drill string, and a drill bit disposed at an end of the drill string. The milling assembly includes a mill drill string and a mill disposed at an end of the mill drill string, the mill having a mill drill bit that is configured to cut and remove material from a casing wall of the first, cased well bore. The mill guiding device is configured to direct the mill drill bit towards the casing wall of the first, cased well bore. 
         [0019]    In more specific aspects, the system may further include a plugging material delivery device that is configured to deliver a plugging material into the first, cased well bore. In some cases, the plugging material may be cement. 
         [0020]    The system may further include an anchor packer assembly that is configured to be disposed at the distal end of the second well bore. 
         [0021]    The mill guiding device may include a wedge-like member. 
         [0022]    In another general aspect, a system for intersecting a first, cased well bore includes a drilling assembly that is configured to drill a second well bore having a distal end proximal to a casing coupling of the first, cased well bore, a milling assembly, and a mill guiding device. The drilling assembly includes a drill string and a drill bit disposed at an end of the drill string. The milling assembly includes a mill drill string and a mill disposed at an end of the mill drill string, the mill having a mill drill bit that is configured to rest along a surface of a casing coupling of the first, cased well bore and cut and remove material from a casing wall of the first, cased well bore and the casing coupling of the first, cased well bore. The mill guiding device is configured to direct the mill drill bit towards the casing wall of the first, cased well bore. 
         [0023]    In more specific aspects, the surface of the casing coupling is an upper, generally flat surface along which the mill drill bit can rest while beginning a cut into the casing wall. 
         [0024]    The mill guiding device may include a wedge-like member. 
         [0025]    The system may further include a plugging material delivery device that is configured to deliver a plugging material into the first, cased well bore. In some cases, the plugging material is cement. 
         [0026]    The system may further include an anchor packer assembly that is configured to be disposed at the distal end of the second well bore. 
         [0027]    In another general aspect, a system for intersecting a first, cased well bore includes a drilling assembly that is configured to drill a second well bore having a distal end proximal to the first, cased well bore, a milling assembly, and a mill guiding device. The drilling assembly includes a drill string and a drill bit disposed at an end of the drill string. The milling assembly includes a mill drill string and a mill disposed at an end of the mill drill string, the mill having a mill drill bit that is configured to cut and remove material from a casing wall of the first, cased well bore. The mill guiding device is configured to direct the mill drill bit towards the casing wall of the first, cased well bore, the mill guiding device comprising alignment features that are configured to limit the relative motion of the mill drill bit relative to the mill guiding device as the mill drill bit moves longitudinally along the mill guiding device. 
         [0028]    In more specific aspects, the alignment features may include one of more grooved guide rails disposed longitudinally along the mill guiding device. The mill drill bit may include one or more tabs that are sized to slide within the grooved rails. In some cases, as the mill drill bit moves along the mill guiding device, the grooved guide rails limit the extent to which the mill drill bit can move transverse to the longitudinal direction of the mill guiding device. 
         [0029]    The system may further include a plugging material delivery device that is configured to deliver a plugging material into the first, cased well bore. In some cases, the plugging material is cement. 
         [0030]    The system may further include an anchor packer assembly that is configured to be disposed at the distal end of the second well bore. 
         [0031]    The mill guiding device may be a wedge-like member. 
         [0032]    In another general aspect, a system for intersecting a first, cased well bore includes a drilling assembly that is configured to drill a second well bore having a distal end proximal to the first, cased well bore, and a laser tool assembly. The drilling assembly includes a drill string and a drill bit disposed at an end of the drill string. The laser tool assembly includes a laser perforator that is configured to emit a laser cutting beam that can penetrate a casing wall of the first, cased well bore and form an opening between the first, cased well bored and the second well bore. 
         [0033]    In more specific aspects, the system may further include a plugging material delivery device that is configured to deliver a plugging material into the first, cased well bore. In some cases, the plugging material is cement. 
         [0034]    The laser tool assembly may further include a first, cased well bore detector. The first, cased well bore detector may include an ultrasonic tool that is configured to detect noise from fluid flow within the first, cased well bore. 
         [0035]    The laser perforator may include a laser beam generator that generates the laser beam, and the laser tool assembly may include a focusing array through which the laser cutting beam passes. 
         [0036]    The laser tool assembly may further include a laser alignment device that is configured to detect the orientation of the laser perforator relative to the casing wall. The laser alignment device may include a metal detector. The metal detector may include a magnetic sensor. 
         [0037]    A portion of the second well bore, where the laser tool assembly will be positioned for emitting a laser cutting beam, is substantially parallel to the first, cased well bore. 
         [0038]    Embodiments may include one or more of the following advantages. 
         [0039]    Using the methods and systems described herein, a cased well bore can be intersected, and in some cases obstructed, more easily than some other intersection methods by reducing the likelihood that a mill cutting into a casing of the cased well bore will walk laterally along the casing during cutting. 
         [0040]    In some embodiments, a mill cutting into a casing of the cased well bore can begin removing material from the casing in a more controlled manner by seating along a generally flat surface of a casing coupling. 
         [0041]    In some embodiments, the cased well bore is more easily intersected by using a laser tool which can be used to cut material from the casing in a more controlled manner than some other intersection methods. 
         [0042]    The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other aspects, features, and advantages will be apparent from the description and drawings, and from the claims. 
     
    
     
       DESCRIPTION OF DRAWINGS 
         [0043]      FIG. 1  illustrates a cross-sectional schematic diagram of a first, cased well bore. 
           [0044]      FIG. 2  illustrates an enlarged cross-sectional schematic diagram of the first well bore of  FIG. 1  showing well bore casings connected by a casing coupling. 
           [0045]      FIG. 3A  illustrates a schematic diagram of an example milling assembly disposed in an second, intersecting well bore that is being drilled proximal to the first well bore of  FIG. 1 . 
           [0046]      FIG. 3B  illustrates a schematic diagram of the milling assembly of  FIG. 3A  anchoring a whipstock in the second well bore. 
           [0047]      FIG. 3C  illustrates a schematic diagram of a mill of the milling assembly of  FIG. 3A  released from the whipstock. 
           [0048]      FIG. 3D  illustrates a schematic diagram of the mill of  FIG. 3C  disposed in a second well bore wherein the mill is seated on a well bore casing coupling and is milling a hole in the casing wall above and through the casing collar of the first well bore. 
           [0049]      FIG. 3E  illustrates a schematic diagram of the mill of  FIG. 3C  penetrating the casing wall and coupling of the first well bore of  FIG. 3A  and intersecting the first well bore of  FIG. 3A . 
           [0050]      FIG. 3F  illustrates the milling assembly of  FIG. 3A  being removed from the second well bore. 
           [0051]      FIG. 3G  illustrates a cement plugging assembly inserted into the second well bore and pumping a plugging material into the first well bore of  FIG. 3A . 
           [0052]      FIG. 4A  is a side view of a milling assembly including a mill and whipstock. 
           [0053]      FIG. 4B  is a top view of the milling assembly of  FIG. 4A . 
           [0054]      FIG. 4C  is a cross-section view of the milling assembly of  FIG. 4A  taken at Section C-C. 
           [0055]      FIG. 4D  is an open hole anchor assembly. 
           [0056]      FIG. 4E  is an open hole packer assembly. 
           [0057]      FIGS. 4F and 4G  are cross-sectional side views, shown in segments, of an exemplary milling assembly. 
           [0058]      FIG. 4H  is a cross-sectional front view of a milling guide of the milling assembly of  FIG. 4A . 
           [0059]      FIG. 4I  is a cross-sectional front view of a mill of the milling assembly of  FIG. 4A . 
           [0060]      FIG. 5A  illustrates a schematic diagram of an example of forming a second, adjacent well bore adjacent to the first, cased well bore of  FIG. 1 . 
           [0061]      FIG. 5B  illustrates a schematic diagram of a laser tool being lowered in the second well bore of  FIG. 5A . 
           [0062]      FIG. 5C  illustrates the laser tool of  FIG. 5B  penetrating a casing of the first well bore of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0063]    Well bores, such as those used to deliver oil or gas from wells within the earth are periodically abandoned, for example, once a suitable amount of oil or gas has been withdrawn from the well or in the event of a well bore blowout. In some cases, a well bore is filled with a material (e.g., plugged with cement) to stop or prevent oil or gas from being inadvertently expelled from the well bore. 
         [0064]      FIG. 1  illustrates a cross-sectional schematic diagram of a cased well bore (e.g., a first well bore)  10  arranged in a formation  12 . For example, the first well bore  10  can be a well bore to be abandoned. The well bore  10  includes a casing  14  that adds structural integrity, as well acts as a conduit to deliver oil or gas from a well. As shown in  FIG. 2 , the casing  14  is typically made of multiple casing segments  16  that are connected by casing couplings  18 . In some cases, it is necessary to penetrate the well bore to be abandoned in order to pump a filling material, such as cement, to form an obstruction and plug the well bore. The obstruction formed in the well bore limits oil or gas from being inadvertently expelled from the well bore.  FIG. 2  illustrates an example region of the well bore  10  to be intersected near one of the casing couplings  18 . 
         [0065]      FIG. 3A  illustrates a schematic diagram of an example drilling assembly  50  (e.g., having a drill bit  52  and drill string  54 ) forming an intersecting second well bore  20  adjacent to the first well bore  10  of  FIG. 1 . The intersecting well bore  20  is typically arranged at an angle of about 0 degrees to about 90 degrees (e.g., about 0 degrees to about 6 degrees, e.g., about 3 degrees) relative to the cased well bore  10  to be intersected. 
         [0066]    The intersecting well bore  20  can be formed by any of various suitable conventional well bore drilling techniques. In some embodiments, a drill rig includes a series of drill string segments that have a drill bit attached to a distal end of the drill string. The drill bit drills (e.g., cuts) through subterranean geologic formations. Drilling fluid (e.g., drilling mud) is pumped down a bore inside of the drill pipe and exits through nozzles in the drill bit. Drilling mud can be a mixture of fluids, solids, and chemicals that are designed to have suitable physical and chemical characteristics to safely drill into the ground material and deliver removed material from the drilled well bore. For example, the drilling mud can be used to remove heat from the drill bit, to lift rock cuttings from the well bore to the surface, to reduce destabilization of the rock in the well bore walls, and to overcome the pressure of fluids inside the rock so that these fluids do not enter the well bore during drilling. 
         [0067]    The rock cuttings generated during drilling are removed by the drilling mud as it circulates to surface outside of the drill string. The drilling mud can then be circulated through filters (e.g., shakers) that strain the rock cuttings from the drilling mud. The filtered drilling mud can then be returned to the well bore being drilled. 
         [0068]    The drilling rig rotates the drill pipe at the surface and rotational torque is transmitted down the drill string to the bit. The bit is rotated and drills through the geologic formations. In other embodiments, the drill string is not rotated by the drilling rig but a down hole mud motor is installed at the distal end of the drill string and drilling mud is pumped down the drill string and passes through the down hole motor. The mud drives the motor as known in the art. The down hole motor provides rotational torque to the drill bit enabling the drill bit to drill through the formations. The drill bit is typically drilled through the formations and towards the first, cased well bore until it is within a desired distance away from the first well bore  10 . Any of various suitable distance, depth, and/or location measurement techniques and devices can be used to monitor and control the position of the drill bit (i.e., and the profile of the intersecting well bore) relative to the first, cased well bore. For example, in some embodiments, sensors (e.g., magnetic sensors) arranged on or near the drill bit can detect the drill bit&#39;s proximity to a location through which the first, cased well bore is to be penetrated. The sensors are connected (e.g., wirelessly or via a wired connection) to a control unit of the drilling rig so that the trajectory of the drill bit can be properly controlled. 
         [0069]    When the sensors determine that the drill bit is at a suitable position relative to the first well bore  10 , the drilling rig can stop rotating the drill bit and withdraw the drill bit  52  and the drill string  54  from the newly formed second, intersecting well bore. A milling assembly is then connected to the lower end of the drill string and inserted into the second well bore  20  for penetrating the first cased well bore  10 . 
         [0070]      FIG. 3B  illustrates a schematic diagram of a milling assembly  100  anchoring a mill guide (e.g., a whipstock)  102  and an anchor packer  104  into the intersecting well bore  20 . The intersecting well bore  20  is formed so that its end  22  is proximal to one of the casing couplings  18  along the casing  16  of the first well bore  10 . 
         [0071]    The milling assembly  100  includes a drill string  106  that is connected to a mill  108  having a mill that is configured to, when operated, cut away material surrounding the mill  108 . Like the drilling assembly  50 , the drill string  106  can include a down hole mud motor installed at the distal end of the drill string  106  and drilling fluid (e.g., drilling mud) can be pumped down the drill string  106  and pass through the down hole motor. The drilling mud drives the down hole motor, as known in the art. The down hole motor provides rotational torque to the mill drill bit enabling the drill bit to drill through the formations  12  or the casing  16 . 
         [0072]    The anchor packer  104  and whipstock  102  are set into the intersecting well bore  20 . For example, the anchor packer  104  and whipstock  102  are run into the intersecting well bore  20  on the distal end of the drill string  106  and may be connected to and positioned below the milling assembly  100 . 
         [0073]    The whipstock  102  is a wedge-like structure having an angled wedge-like surface  110  to create a taper within the intersecting well bore  20 . In some embodiments, the whipstock  102  has a concave surface formed along the angled wedge-like surface  110  that is shaped to accommodate the outer diameter of the milling  108 . The whipstock  102  is arranged within the intersecting well bore  20  so that the angled wedge-like surface  110  directs a mill  108  of the milling assembly  100  towards a portion of the cased well bore above a casing coupling  18 .  FIGS. 4A to 4C  illustrate a milling assembly  100  that includes a mill  108  on a hydraulic running tool log and a whipstock  102 . 
         [0074]    The anchor packer  104  and whipstock  102  are typically positioned into (e.g., run into) the intersecting well bore  20  as an assembly that is released from the drill string  106  once the anchor packer  104  contacts a surface, such as the end  22  of the intersecting well bore  20 . Once released, the anchor packer  104  is expanded and contacts the walls of the ground surrounding the intersecting well bore  20  to provide structural stability to the anchor packer  104  and the whipstock  102 . In some embodiments, the anchor packer  104  and the whipstock  102  are each run into the intersecting well bore  20  individually on separate trips of the drill string. In some embodiments, the anchor packer  104  is an anchor assembly  101  and a packer assembly  103 .  FIG. 4D  illustrates an open hole anchor  101  available from Halliburton under model no. 635.69.  FIG. 4E  illustrates an open hole packer  103  available from Halliburton as model no. 630.345. 
         [0075]      FIG. 3C  illustrates a schematic diagram of a mill  108  of the milling assembly  100  of  FIG. 3B  released from the whipstock  102 . Once the anchor packer  104  is set into the intersecting well bore  20 , the milling assembly  100  (e.g., the mill  108  of the milling assembly  100 ) is released from the whipstock  102 . 
         [0076]    Typically, the mill  108  is connected to the whipstock  102  by connecting bolts that can be sheared due to axial force applied to the drill string  106  or due to torque applied to rotate the mill  108  and shear the connecting bolts. Once disconnected from the whipstock  102 , the mill  108  can be rotated. For example, hydraulic drilling fluid (e.g., drilling mud) is pumped down the drill string  106  which drives a down hole motor that provides rotational torque to the mill  108  to begin cutting into the formation  12  between the intersecting well bore  20  and the cased well bore  10  and, due to the orientation of the whipstock  102 , the mill  108  is directed towards the cased well bore  10 . When the mill  108  is proximal to the casing  16  of the cased well bore  10 , the mill  108  may drill though a cement sheath surrounding the casing  16  in the first well bore  10  (i.e., if the casing  16  has been cemented into the cased well bore  10 ). After milling though the cement sheath the mill  108  will contact the casing  16  of the cased well bore  10 . 
         [0077]      FIG. 3D  illustrates a schematic diagram of the mill  108  of  FIG. 3C  milling a well bore casing  16  above the casing coupling  18 . Due to the arrangement of the intersecting well bore  20  and the set anchor packer  104  and whipstock  102 , the mill  108  rides on an upper end of the casing collar  18  and cuts away the casing  16  above the collar  18  and begins to also cut away the collar  18 . The relatively flat upper surface of the collar  18  provides an engaging surface that the mill  108  is able to begin cutting from. The mill  108  will preferentially cut into the casing wall  16  above the collar  18  and also cut collar. The whipstock  102 , and its curved angular surface, also helps to guide the mill  108  and reduce the likelihood that the mill  108  will walk laterally along the outer surface of the casing  16 . 
         [0078]      FIG. 3E  illustrates a schematic diagram of the mill  108  of  FIG. 3C  penetrating the well bore casing wall  16  and grinding off the upper portion of the coupling  18  of  FIG. 3D  and intersecting the cased well bore  10  of  FIG. 3B . The mill  108  continues to operate and cuts through the casing wall  16  and the coupling  18  until it penetrates them to hydraulically connect the cased well bore  10  and the intersecting well bore  20 . 
         [0079]    The cutting path of the mill  108  within intersecting well bore  20  can depend on various factors, such as, for example, the size of the intersecting well bore  20 , and the design and shape of the whipstock  102  and mill  108 . For example, in some embodiments, depending on the desired size (e.g., the width) of the hole to be formed in the casing  16  being intersected and the taper angle of the inclined whipstock  102 , the length of the cut can be estimated according to the following formula, Tan(x)=(w)/(2*L), where x is the taper angle of the whipstock (in degrees), w is the width of the mill  108  and L is the length of the cut. As shown, w is divided by 2 because the mill  108  would typically only need to travel a distance that is half of its diameter inward to fully penetrate the casing  16 . In some implementations, the whipstock has a taper angle of 3 degrees (x=3 degrees). When forming holes using such whipstocks, if a mill with an 8.5 inch outer diameter is used, and therefore a hole that is generally a maximum of 8.5 inches wide would be formed in the casing  16  when the mill travels halfway into the casing then the length that the cut can be estimated by, Tan(3 deg)=8.5/(2*L). The length, L, would be about 81 inches. Therefore, in order to fully penetrate the casing  16  and casing coupling  18 , the mill  108  travels about 81 inches longitudinally while being driven into the casing by the whipstock  102 . 
         [0080]    The width and length of the cut to be formed in the casing  16  is generally determined based on the processes to be performed following intersection of the cased well bore  10 . For example, in some cases, tubing or piping may be inserted into the cased well bore  10  to pump mud or cement into the cased well bore  10 . In such cases, the width of the opening would likely be large enough to insert the tubing or piping, including a margin of error. Alternatively, in some cases, a long and wide enough opening is preferred to pump cement or mud directly into the intersecting well bore  20  in order to obstruct the cased well bore  10  without needing to insert tubing or piping directly into the cased well bore  10 . 
         [0081]    Typically, an opening is cut that has a greater flow area that the flow area of the tubing or piping used to pump the mud or cement so that the opening would not restrict the flow of the mud or cement being pumped. However, an even larger opening can be cut if needed, for example, if there was a need to insert something directly into the cased well bore  10  being intersected or to avoid a significant pressure loss through the opening if a large volume and/or high velocity of fluid is to be pumped through the opening. 
         [0082]    While cutting, the mill  108  is rotates and cuts away the casing wall  16  and the casing coupling  18  until the cased well bore  10  is fully penetrated and a hole  24  is formed according to the desired hole parameters (as discussed above). Full penetration of the casing coupling  18  and the well bore casing wall  16  can be detected using any of various suitable techniques and devices. For example, the resisting torque at the mill  108  can be measured and monitored to predict (e.g., determine) the material through which the mill  108  is cutting. The resisting torque typically increases when the mill  108  begins cutting the metal casing wall  16  or casing coupling  18 . Monitoring the amount the milling string advances (i.e., the depth of the milling string) from this point would give an indication of how wide an opening is being created. 
         [0083]      FIG. 3F  illustrates the milling assembly  100  of  FIG. 3B  being removed from the intersecting well bore  20 . The milling assembly  100  is removed from the intersecting well bore  20  so that a plugging material (e.g., cement) can be delivered from the intersecting well bore  20  through the penetrated hole  24  and into the cased well bore  10 . 
         [0084]    Typically, the anchor packer  104  and whipstock  102  are left in the intersecting well bore  20  during cement delivery. In some embodiments, the whipstock  102  and anchor packer  104  are removed prior to pumping cement. 
         [0085]      FIG. 3G  illustrates a cement delivery assembly  150  inserted into the intersecting well  20  and pumping a plugging material (e.g., cement) into the cased well bore  10 . Once the penetrated hole  24  is formed and the cased well bore  10  and the intersecting well bore  20  are fluidly connected, the cement delivery assembly  150  pumps cement into the cased well bore  10 . For example, cement can be pumped from the intersecting well bore  20  through the penetrated hole  24  formed in the casing wall  16  and the coupling  18  and into the cased well bore  10 . 
         [0086]    Cement is pumped until an amount of cement that is sufficient for forming a structurally suitable barrier within the cased bore  10  is delivered. For example, in some cases, cement is pumped into the cased well bore  10  until a barrier is formed that can prevent a gas or oil from exiting the cased well bore  10 . The volume of cement that is pumped is typically dependent upon the conditions of the well bore and, in some cases, regulatory requirements. In some embodiments, the cement delivery assembly  150  includes a check valve that permits cements to flow into the well bores while reducing the likelihood that fluid in either of the well bores (e.g., gas or oil) can flow upward in the drill string located in the intersecting well bore  20  and out of the intersecting well bore  20 . For example, check valves can be used when intersecting and delivering cement to a well bore that has suffered a blowout. In some embodiments, cement is delivered using other systems. For example, cement can be pumped through the drill string  106  of the milling assembly  100 . 
         [0087]    In some embodiments, other types of equipment are used to deliver and guide a mill within the intersecting well bore  20 . For example, milling assemblies can include alignment features to constrain the path of a mill along a mill guide. For example, referring to  FIGS. 4F-4I , a milling assembly  200  can include a tapered mill guide  202  that engages with corresponding features of the mill  208  to help reduce the likelihood of the mill  208  from walking away from the mill guide  202 , for example moving laterally along the well bore casing  16  of the cased well bore  10  during milling. For example, as shown, the MillRite style milling assembly  200  from Halliburton includes a mill guide  202  having alignment grooves  212  that span longitudinally along the mill guide  202  and help to align the mill  208  with the mill guide  202  and reduce the likelihood that the mill  208  will walk along the casing  16 . The mill  208  includes tabs  214  that are sized and configured to be received within the grooves  212  of the mill guide  202 . 
         [0088]    The MillRite milling assembly  200  can be inserted into an intersecting well bore  20  until seated against the end  22  of the intersecting well bore  20  (e.g., using an anchor packer  104 ) (shown in  FIG. 3B ). Once in position near the cased well bore  20 , hydraulic fluid (e.g., drilling mud) can be pumped down the drill string of the milling assembly  200 , as discussed above with reference to  FIGS. 3B-3E . Hydraulic pressure applied can be used to release a hydraulic mill  208  running tool from the mill guide  202  and the mill  208  can begin rotating and advancing along the wedge-like mill guide  202 . Due the shape of the mill guide  202 , the mill  208  slowly advances into and against the casing  16  of the cased well bore  10  and a hole can be cut that fluidly connects the cased well bore  10  and the intersecting well bore  20 . Plugging material (e.g., cement) can then be inserted into the cased well bore  10  to obstruct the cased well bore  10 , as discussed above and illustrated in  FIG. 3G . 
         [0089]    Laser Perforation 
         [0090]    While mechanical machining devices have been described as forming the opening in the cased well bore  10 , other techniques are possible. 
         [0091]      FIG. 5A  illustrates a schematic diagram of an example drilling assembly  50  forming a second, adjacent well bore  20  proximal to the first, cased well bore  10  of  FIG. 1 . The drilling assembly  50  includes any of various suitable conventional drilling devices, such as the drilling rig discussed above. The adjacent well bore  20  is arranged so that a laser tool can be lowered downward generally vertically into the adjacent well bore  20 . For example, the adjacent well bore  20  can be arranged relative to the cased well bore  10  so that a laser tool (e.g., a wireline laser tool) can be deployed at an angle of about 0 degrees to about 65 degrees relative to a vertically oriented cased well bore  10 . The adjacent well bore  20  extends to a depth that at least reaches a desired location for penetrating the cased well bore  10 . Once the adjacent well bore  20  is formed to the desired depth, the drilling assembly  50  (e.g., a drill bit  52  and drill string  54 ) can be raised and removed from the adjacent well bore  20 . 
         [0092]      FIG. 5B  illustrates a schematic diagram of a laser tool  300  being lowered in the adjacent well bore  20  of  FIG. 4A . The laser tool  300  is lowered to the desired depth where a perforation in the casing of the cased well bore  10  is to be formed. Various techniques and devices can be used to determine the depth that the laser tool  300  has been lowered into the adjacent well bore  20 . For example, a wire line measurement could be monitored as a cable  302  supporting the laser tool  300  is spooled off at the surface. However, in some cases, these measurements may have errors associated with stretching of the cable  302 . In some embodiments, a magnetic ranging tool is used to detect the proximity of the laser tool  300  relative to the cased well bore  10 . Alternatively or additionally, in some embodiments, the laser tool  300  includes an ultrasonic tool is arranged above a laser perforator  304 , where the ultrasonic tool can detect the noise from the gas and/or fluid flow in the cased well bore  10  when the laser tool  300  reaches an area proximal to the cased well bore  10 . 
         [0093]    Once at the desired depth to form a perforation, the laser perforator  304  of the laser tool  300  is aligned with the casing  16  of the cased well bore  10 . For example, the laser tool  300  can include metal detectors (e.g., magnetic sensors) so that as the laser tool  300  is rotated, it can detect when the laser perforator  304  is aimed at the metal casing  16 . Alternatively or additionally, in some embodiments, ultrasonic tools are used to detect the orientation of the laser perforator  304  relative to the cased well bore  10  and for aiming the laser perforator  304  at the metal casing  16 . 
         [0094]      FIG. 4C  illustrates a laser perforator  304  of the laser tool  300  of  FIG. 4B  penetrating the casing  16  of the cased well bore  10 . Once aligned with the desired portion of the cased well bore  10 , the laser of the laser perforator  304  can be operated to laser cut (e.g., perforate) an opening in the casing wall  16  of cased well bore  10 . While the laser perforator  304  emits a laser cutting beam, the laser perforator  304  can be moved relative to the casing  16  to create an opening. Various devices can be used to move the laser perforator  304  and therefore also the emitted laser to form the opening. For example, hydraulic or electromechanical devices or system can be used to articulate the laser tool within the adjacent well bore to cut an opening. Prior art devices and systems that may be used to articulate a laser tool are disclosed in U.S. Pat. No. 7,938,175. 
         [0095]    Once the opening is formed in the casing wall  16  of the cased wellbore  10 , the laser tool  300  can be removed from the adjacent well bore  20 . As discussed above, a cement pumping assembly can then be lowered down into the adjacent well bore  20  to the region of the opening formed along the casing wall  16  of the cased well bore  10  by the laser tool  300 . Cement is then pumped from a cement pumping head of the cement pumping assembly into the opening. Cement is pumped until an amount of cement that is sufficient for forming a structurally suitable barrier within the cased well bore  10 . For example, in some cases, cement is pumped into the cased well bore  10  until a barrier is formed that can prevent a gas or oil from exiting the cased well bore  10 . 
         [0096]    A number of embodiments have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. Accordingly, other embodiments are within the scope of the following claims.