Abstract:
An apparatus for pulling objects from a well is described. The apparatus may comprise an elongated housing having an internal chamber. The housing will be connected to a work string such as wireline or coiled tubing. A skirt is attached to the housing, with the skirt having an inner portion. The skirt will contain a first window and a second window, with the first window having a first load shoulder and the second window having a second load shoulder. The apparatus further contains a mandrel disposed within the inner portion of the skirt, and two dog members disposed about the mandrel. The dog member have a first surface that cooperates with the first load shoulder and a second surface that cooperates with the second load shoulder. The dog members distributes a pull force which is exerted on the apparatus to the first and second load shoulder so that the effective tensional strength of the skirt is enhanced. The mandrel will have a second end containing an angled shoulder. The dog member will contain an angled leg that is configured to cooperate with the angled shoulder of the mandrel. The apparatus comprises a member for selectively disconnecting the skirt to the mandrel so that the mandrel is slidably received within the inner chamber of the housing which allows for the apparatus to be retrieved from the well. A method of releasing a device that is attached to an object within a well bore is also disclosed.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to an apparatus and method for retrieving objects from a well bore. More particularly, but not by way of limitation, the invention relates to a pulling tool and method for retrieving objects that are located within a well. 
     In the oil and gas industry, a well will intersect a subterranean hydrocarbon reservoir. The well will be completed to the reservoir, and the hydrocarbons will be produced to the surface. During the drilling, completion, and production of the well, operators will many times find it necessary to set various tools within the well. As those of ordinary skill in the art will appreciate, various devices are run into the well, set into the well, and later retrieved from the well. In order to run tools into the well, running tools that are commercially available from various manufacturers such as Camco and Halliburton are used. The devices set into the well may include valves, plugs, safety devices, and other tools. 
     In the event that the tool previously placed into the well requires removal, the operator will run into the well with a pulling tool. The pulling tool is used to retrieve the previously set device within the well and is commercially available from Camco, Halliburton and others. Nevertheless, when an operator attempts to retrieve a device from a well, the device may be difficult to pull. As those of ordinary skill in the art will appreciate, the operator may latch onto an object and experience a high degree of difficulty with retrieving the object/device. Even during normal retrieval operation, significant demands are placed on the integrity and strength of a pulling tool. 
     Sometimes, the amount of force required to dislodge the object overcomes the structural integrity of the pulling tool. In other cases, the object being pulled becomes in effect stuck in the well. Therefore, pulling tools have been designed so that the tool will shear off of the object at a predetermined force. 
     Prior art tools have been limited in the amount of pull force that can be applied to the pulling tool. The pull force will be limited by the structural design of the pulling tool. Therefore, there is a need for a tool that will allow for a greater pulling force to be exerted. There is also a need for a pulling tool that will allow for a greater force to be exerted in highly deviated and horizontal wells. 
     SUMMARY OF THE INVENTION 
     An apparatus for pulling objects from a well is described. The apparatus may comprise an elongated housing having an internal chamber. The housing will have means for connecting to the work string. The work string may include wireline, tubular, and/or coiled tubing. In the preferred embodiment, the work string will be wireline. A skirt is attached to the housing, with the skirt having an inner portion. The skirt will contain a first window and a second window therein, with the first window having a first shoulder thereon and the second window having a second shoulder thereon. 
     The apparatus further contains a mandrel disposed within the inner portion of the skirt, and a dog member disposed after the mandrel. The dog member has a first surface that cooperates with the first shoulder and a second surface that cooperates with the second shoulder. The apparatus also contains means, disposed about the mandrel, for biasing the dog member in a downward direction. The mandrel will have a first end and a second end, with the second end containing an angled shoulder. The dog member will contain an angled leg that is configured to cooperate with the angled shoulder of the mandrel. In the preferred embodiment, two dog members are used. When two dog members are used, the skirt contains a third and fourth window with a third shoulder and a fourth shoulder respectively. 
     In one embodiment, the apparatus will further comprise means for connecting the skirt with the mandrel. The first end of the mandrel contains a core nut attached thereto, with the core nut cooperating with the internal chamber of the housing to form a first spring chamber. The apparatus further comprises a first spring disposed within the first spring chamber, with the first spring acting to create a force against the core nut in an upward direction. The connecting means includes a shear pin that attaches the skirt to the mandrel such that as the shear pin is sheared, the mandrel is slidably received within the inner chamber of the housing. The biasing means may further comprise a spring, and a retaining ring disposed about the mandrel and cooperating with the spring to urge the dog member into engagement with the first shoulder and the second shoulder. Also, the mandrel may contain an inner bore, and the device may further include seal means, disposed about the mandrel, for sealing a fluid in the inner bore from the first spring chamber. 
     The device may be attached to a work string. The device comprises a tubular housing, a skirt attached to the tubular housing, the skirt containing a first and second window with shoulders thereon, a core being disposed within an inner bore of the skirt, with the core containing an end having an angled shoulder, a dog member disposed about the core, the dog member having a first end that cooperates with the first window and a second end that cooperates with the second window. 
     The method includes pulling upward on the wire line so that an upward force is created, and transferring the upward force to the tubular housing. Next, the upward force is transferred to the first window and the second window. The dogs are supported at the first shoulder of the first window and at the second shoulder of the second window. This allows distribution of the upward force to two points in the skirt. The operator may then provide a downward jarring force to the tubular housing. The core is contacted against the object, and a pin may be sheared so that the core is slidably disposed within the inner portion of the tubular housing. A core spring, located in a first spring chamber, is expanded which in turn lifts the core upward. 
     Next, the angled core end is engaged with an angled surface of the dog member which in turn lifts the dog member thereby expanding the dog member outward into the first window. The core is biased with the core spring located within the spring chamber. Thereafter, the core is moved upward within the inner portion. Next, the device is sheared and released from the object, and the device can be retrieved from the well bore. 
     An advantage of the present invention is the novel dog, support herein disclosed. Another advantage is the that the dogs are supported at two points in the skirt. Dogs in the prior art are supported at only one point in the skirt. Still yet another advantage is that the upward pull force is distributed to the skirt in two different locations. 
     A feature of the present invention is the use of a first and second dog member in the preferred embodiment that are extra wide so that approximately 50% of the fishing neck circumferential area is covered. Another feature is the ability to have a jar-up embodiment and a jar-down embodiment with essentially identical components. Also, in cases where it is not recommended to run a “jar down to shear” pulling tool, the operator has the ability to run the “jar-up to shear” pulling tool embodiment. 
     Another feature is that upon shearing of the pulling tool, the dogs are forced into the release mode by the angle on the top of the dogs being pushed up against the top shoulder in the windows and the mid section of the dog&#39;s inner surface being pushed out of the angled surface at the bottom of the core. There is a 1.5 degree difference between the longer surface of the mandrel and the upper inside surface of the two member dogs which facilitates member dog release from the object. The angle at the bottom of the mandrel is responsible for lifting the dogs and pushing the dog legs outward. Another feature is that the tool is designed so that after shearing, the two sheared ends of the pin can not be accidentally lost while pulling out of the well. Yet another feature is there are no externally visible springs that could hang up within the well bore and be torn off, leaving debris that can interfere with subsequent operations. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partial cross-sectional view of the first embodiment of the novel apparatus of the jar down shear configuration depicted in the pulling mode. 
     FIG. 2 is a partial cross-sectional view of the embodiment of FIG. 1 depicted in the sheared mode. 
     FIG. 3 is a partial cross-sectional view of the second embodiment of the novel of the jar up shear configuration apparatus depicted in the pulling mode. 
     FIG. 4 is a partial cross-sectional view of the embodiment of FIG. 3 depicted in the sheared mode. 
     FIG. 5 is the embodiment of FIG. 1 illustrating the novel apparatus approaching the fishing neck of the object to be pulled from the well. 
     FIG. 6 is the embodiment of FIG. 5 illustrating the sequential step of latching the novel apparatus onto the fishing neck of the object. 
     FIG. 7 illustrating the sequential step of latching onto the fishing neck of the object to be pulled from the well. 
     FIG. 8 illustrated the sequential step of shearing the shear pin in the novel apparatus. 
     FIG. 9 illustrates the next sequential step wherein the shear pin has sheared. 
     FIG. 10 illustrates the sequential step of retrieving the novel apparatus from the well. 
     FIG. 11 is a cross-sectional area taken along line A—A of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to FIG. 1, a partial cross-sectional view of the first embodiment of the novel apparatus  2  will not be described. In the embodiment of FIG. 1, the apparatus  2  is shown in the pulling mode. This embodiment is also referred to as the jar down shear configuration. The apparatus  2  will generally include a tubular housing  4  that has a means for connecting to a work string. In the embodiments shown, the connection means comprises an external thread means  6  that extends to a first shoulder  8  which in turn extends to a generally first cylindrical surface  10 . The first cylindrical surface extends to the chamfered surface  12  that in turn extends to the second cylindrical surface  14 , with the surface  14  terminating at the end  16  . Extending radially inward of the end  16  is the internal bore  18 , with the bore  18  having internal thread means  20  . 
     A skirt  22  is also provided. The skirt contains a first outer cylindrical surface  24  and thread means  2 that extends to a shoulder  26 , with the shoulder  26  stretching to the second outer cylindrical surface  28  and an end  29 . The skirt  22  will have a first window  30  (also referred to as an opening) and a second window  32  (also referred to as an opening). The window  30  contains the shoulders  34 ,  36  and the window  32  contains the shoulders  38 ,  40 . The shoulder  40  contains a generally angled surface  40  that extends to the inner bore surface  42  which in turn concludes at the radial shoulder  44 . The skirt  22  concludes at the end  46 . The skirt  22  contains a first inner bore  48  and a second inner bore  50 . 
     The apparatus  2  also contains the core member, seen generally at  52 . The core member  52  is generally cylindrical and contains an outer cylindrical surface  54  that contains an indention  56  that forms circumferential recess to receive set screw  8   1 . The outer cylindrical surface  54  also contains the external thread means  58 . The second end of the core member  52  contains an angled surface  60 , with the angled surface  60  conducting at the end  62 . Extending radially inward is the bore  64  that contains internal thread means  66 . 
     The core member  52  will be operatively associated with the core nut  68 . As depicted in FIG. 1, the core nut  68  will be threadedly connected to core member  52 . The core nut  68  will contain the conical surface  70  that extends to the cylindrical outer surface  72  that terminates at the end  74 . The end  74  continues radially inward to the inner bore  76  that contains the internal threads  78  that will cooperate with the thread means  58 . Thus, a chamber is formed between the cooperation between the core nut end  74  and the skirt  22 , with a spring means  80  being disposed therein. The spring means  80  will be a compression type of spring which in the embodiment seen in FIG. 1 is in compression. In the embodiment shown, the core nut  68  also contains an aperture for placement of a set screw  81 . The set screw  81  will be configured to cooperate with the indentation  56  which aids in the attachment of the core nut  68  to the core member  52 . 
     A means for connecting the core  52  to the skirt  22  is also provided. The connecting means is, in the preferred embodiment, a shear pin  82 . The shear pin  82  is fitted in an aperture located within the skirt  22  and an aperture located within the core  52 . The shear pin  82  is generally a {fraction (5/16)} inch diameter shear pin. This diameter shear pin allows for a significantly greater pull force to be exerted to the apparatus  2  before shearing, as will be explained in greater detail later in the application. 
     The dog member  88  will now be described. In the embodiment shown, a first dog member  88  and second dog member  89  is depicted, with the two dogs being similar in construction. As those of ordinary skill in the art will appreciate, pulling tools generally contain at least two dog members. The dog member  88  contains a first end  90  that is angled in the preferred embodiment at an angle of 66 degrees. The first end  90  extends to the chamfered surface  92  which in turn extends to the outer surface  94 . The outer surface  94  terminates at the radial shoulder  96 , with the radial shoulder  96  extending to the outer surface  98 . As seen in FIG. 1, the radial shoulder  96  cooperates with shoulder  36  as a load surface. 
     The outer surface  98  extends to an angled leg portion  100 , with the angled leg portion  100  terminating at the outer surface  102 . The outer surface  102  concludes at the angled surface  104 , with the angled surface  104  cooperating and abutting with the shoulder  40 . The angled surface  104  extends to the outer surface  106  which in turn extends to the end  108 , with the end cooperating and abutting the radial surface  44 . Extending radially inward is the inner surface  110  that stretches to the radial shoulder  112  which in turn concludes at the inner surface  114 . The inner surface extends to the angled inner surface  116  which in turn extends to the inner surface  118 . 
     The apparatus  2  also includes a retaining ring  120 , with the retaining ring  120  being disposed about the core member  52 . The retaining ring also cooperates and is disposed within the inner bore  48  of the skirt  22  such that a spring chamber  122  is formed. The spring chamber  122  will have the compression spring  124  disposed therein. The retaining ring  120  contains a first end  126  and a second angled end  128 , with the angled end  128  being complementary with the end  90  of the dog  88 . The compression spring  124  will bias the end  126  while the other end of the spring  124  acts against the end of the spring chamber  122 . 
     Referring now to FIG. 3, a partial cross-section of a second embodiment of the present invention will now be described. This embodiment is also referred to as the jar up shear configuration. It should be noted that like numbers appearing in the various figures refer to like components. In the embodiment of FIG. 3, the tubular housing  4  has contained therein the aperture  132  for placement of the set screw  81 . The internal bore  18  extends to a shoulder  134  that in turn stretches to internal thread means  136 . The internal thread means  136  cooperate with the external thread means  58  of the core  52 . 
     As depicted in FIG. 3, the skirt  22  is identical to the skirt  22  illustrated in FIGS. 1 and 2. Note that the external thread means  2 do not engage with any thread means of the tubular housing  4 , instead, the skirt  22  is slidably received within the internal bore  18  of the tubular housing  4 . The skirt similarly contains the first window  30  and the second window  32  that allows the cooperation of the dog members  88  for latching and unlatching from the fishing neck of the object to be retrieved from the well. 
     A spring chamber  138  is formed from the configuration of the shoulder  134 , the outer surface  54  and skirt end  29 . The compression spring  82  is therefore disposed within the spring chamber  138 . The core  52  is selectively connected to the skirt  22  via the shear pin  82  which is fitted into an aperture of the skirt  22  and an aperture of the core  52 . The retaining ring  120  is also provided, with the compression spring  124  acting to bias the retaining ring into engagement with the dog member  88 . FIG. 4 is included to show a partial cross-sectional view of the embodiment of FIG. 3 depicted in the sheared mode. 
     Reference is now made to FIGS. 5,  6 ,  7 ,  8 ,  9 ,  10  which is the sequence showing the novel apparatus  2  (of FIG. 1 ) approaching the fish, latching on to the fish, and then shearing off of the fish. With particular reference to FIG. 5, FIG. 5 depicts novel apparatus  2  approaching the fishing neck  144  of the fish  142  that will be pulled from the well. Thus, the inner bore  48  with skirt  22  will be lowered over the fish, and in particular the conical surface  146  and the first cylindrical surface  147 . As depicted in FIG. 5, the skirt, and in particular the inner bore  48 , will be allowed passage over the cylindrical surface  147 . Note that compression spring  124  acts against retaining ring  120  so that the dog member  88  acts against shoulder  38  as well as  44  of the skirt. 
     With reference to FIG. 6, the next sequential step depicting the novel apparatus  2  latching onto the fishing neck  144  will now be described. Thus, as the apparatus  2  is lowered via the work string, the conical surface  146  will act against the end  108  of the dog member  88  thereby pushing the dog member  88  upward. This in turn causes the dog member  88  to act against the retaining member  120  with the retaining member  120  thereby compressing spring  124  as shown in FIG.  6 . Further downward movement causes the dog member to become situated as shown in FIG.6 wherein end  108  abuts shoulder  40 . 
     Next, FIG. 7 shows the following sequential step wherein the apparatus  2  is latched onto the fishing neck  144  of fish  142 . In particular, once the skirt  22  has been lowered to the appropriate depth, the spring  124  will bias the dog member  88  downward, thereby allowing the radial shoulder  112  to engage the radial shoulder  148  of the fish  142  as depicted in FIG.  7 . Note that the dog member end  108  abuts radial surface  44  of the skirt  22 . In normal operation, the operator can begin to pull on the fish since the dog members, and in particular the shoulders  112 , are latched on to the fish. 
     Due to the novel design, the dogs  88  are supported at shoulder  36  and end  44 . The two point support distributes the pulling load to two places on the skirt  22 . In other words, by transferring the upward force from the first end and second end of the dog  88  to the first shoulder and the second shoulder of the skirt, this upward force is distributed to the first point (shoulder  36 ) and second point (shoulder  44 ). In experimental tests, it has been found in a pull test that the novel design allows a pull of over 60,000 pounds. More particularly, the first pull test resulted in a pull of approximately 62,250 pounds before the dogs were damaged (sheared), a second pull test resulted in a pull of approximately 60,500 pounds before the dog were damaged (sheared) and a third pull test resulted in a pull of approximately 64,650 pounds before the dogs were damaged (sheared). In these test, the skirt proved to be undamaged and capable of further use attesting to the novel distribution of the pull load about the skirt. 
     Thus, by allowing the force to be distributed to two places in the skirt, it is possible to pull a much greater force than ever before existed in prior art pulling tools. As well bores become more deviated and skewed, it is very important for operators to have the ability to pull this increased load in order to unseat any previously set device and/or fish. It should be noted that the embodiment of FIGS. 3 and 4 will distribute the forces about the skirt in the same manner. 
     In the event that the operator cannot pull the object from the well, it becomes necessary to shear the shear pin  82  and retrieve the novel apparatus  2  without the fish  142 , as will be appreciated by those of ordinary skill in the art. This is accomplished by the ensuing sequential step shown in FIG. 8 of shearing the shear pin  82 . Thus, the operator will lower the apparatus via the work string. This in turn will cause the end  62  of the core  52  to abut the top end  152  of the fish  142  as shown in FIG.  8 . Further downward movement allows the skirt end  46  to proceed downward relative to the cylindrical surface  150  of the fish. Once the appropriate amount of downward jarring force has been applied to the apparatus  2 , shear pin  82  will shear. The shear pin shears to segments  82   a  and  82   b . Please note that in the design of the preferred embodiment, the shear pins  82   a ,  82   b  do not drop off into the well bore, but rather are retained within the core and the skirt as shown. 
     As depicted in FIG. 9, which is the next sequential step after the shear pin  82  has been sheared, the spring  80  can now bias upwards the core nut  68 . By biasing the core nut  68  upwards along with the core  52 , the angle surface  60  of the core  52  will engage and cooperate the angled inner surface  116  of the dog members  88  as depicted in FIG.  9 . This engagement of surface  60  with surface  116  expands the dog member outward such that the surface  106  of the dog  88  no longer engages the inner bore surface  42  of the skirt. This expansion will allow the radial shoulder  112  to clear the radial shoulder  148  of the fish  142 . 
     The last sequence is shown in FIG.  10 . This is the sequence where in the novel apparatus  2  is being retrieved from the well. Note that spring means  80  has biased the core nut  68  and core  52  upwards. Angled surface  60  and angled surface  116  are cooperating thereby expanding the dog member  88 , and in particular the radial shoulder  112  past the radial shoulder  148 . It should be noted that once the shear pin  82  is sheared, the spring  80  will overcome spring  124  thereby allowing the disposition of the core  52  to dog  88  as shown in FIG.  9  and FIG.  10 . 
     In operation of the second embodiment illustrated in FIG. 3, an upward pull is exerted on the work string, such as wire line, coiled tubing or electric line. The upward pull is applied directly through the thread connection  6  and the thread connections  58 / 136  of the core  52  to the tubular housing  4 . As the pulling force is exerted, the force is transmitted to the shear pin  82 , to the skirt  22 , then to the dogs by the load surfaces  36 / 44  and to the hooked bottom  112  of the dogs  88 / 89 . It should be noted that the novel distribution of forces is as mentioned earlier with reference to the embodiment of FIGS. 1 and 2. 
     After latching onto a fishing neck (contained on the object being retrieved from the well), upward jarring is transmitted through the shear pin  82  to the dogs. After a period of jarring, the operator will find it necessary to shear the pin  82  in order to pull out of the well. Once the sufficient amount of upward jarring force is applied, the pin will shear into the  82   a  and  82   b , as seen in FIG. 4, between the core  52  and the skirt  22  allowing the core  52  to move upward which in turn pulls the dogs  88  up causing the hooked ends  112  to move up and out, thereby releasing from the fishing neck. Note that the pins  82   a ,  82   b  are blocked from falling out of the apparatus  2 . 
     Therefore, in the embodiments thus presented, the novel apparatus  2  will stand significantly more pull and strain than prior art pulling tools. One of the reasons for this increase in pull is the support provided by the dogs  88 / 89 . The dogs  88 / 89  are supported at points  36  and  44  whereas prior art devices are supported at only one point i.e. on only one shoulder. The two point support distributes the puling load to two places on the skirt  22 . Further, the dogs  88 / 89  are fabricated from carbon or alloy steel. The invention herein described is convertible from a jar up type of tool to ajar down type of tool by simply switching the upper tubular housing and providing the core nut. 
     It should also be noted that it is possible to bore a fluid passage through the center of the housing  4  and core  52  so that a fluid can be pumped therethrough. In this embodiment, the operator can pump a well fluid, drill fluid, completion fluid, etc. through the bore, The ability to pump through may be beneficial in certain circumstances such as a fishing job. 
     Changes and modifications in the specifically described embodiments can be carried out without departing from the scope of the invention which is intended to be limited only by the scope of the appended claims.