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BACKGROUND OF THE INVENTION  
         [0001]    This invention relates to an apparatus for filtering a well bore fluid. More particularly, but not by way of limitation, this invention relates to an apparatus positioned in a tubular member in order to filter a well bore fluid. The invention also describes the method of filtering the well bore fluid with the apparatus.  
           [0002]    The use of drilling fluids for the drilling of oil and gas wells is well known. The drilling fluid serves many purposes, including suppression of reservoir pressure, lubrication of the drill pipe, and cooling of the bottom hole assemblies, etc. The bottom hole assemblies may contain individual components such as bits, stabilizers, measurement while drilling tools, etc. Many times, the bottom hole assemblies contain electronic sections such as microprocessors that are used to collect and/or transmit data collected by sensors placed in the bottom hole assemblies.  
           [0003]    Drilling fluids may contain many different types of components such as mud, chemicals, drill cuttings, metal shavings, etc. The particle size of these various components vary from microns to inches. Additionally, rig crews may inadvertently drop tools, glooves, rags or other unwanted materials into the well bore. The unwanted and/or undesirable solids, hereinafter referred to as debris, is highly harmful. For instance, the debris can cause failures in the electrical components of the bottom hole assemblies. Therefore, operators find it desirable to filter the drilling fluid of the debris.  
           [0004]    Many methods of filtering well bore fluid exists. One present method includes placing a filter in the tubular members while the tubular members are being run into the well bore. The prior art devices presently available utilize a cylindrical screen that have an external fishing neck. However, these types of devices have many disadvantages. For instance, the openings contained in the top end have a limited flow through area. Additionally, the external fishing neck has an inherent weak point at the stem making it possible for the stem to break off while in the tubular members, which would be highly undesirable and/or dangerous, as those of ordinary skill in the art will recognize.  
           [0005]    Therefore, there is a need for an apparatus for filtering a drilling fluid. There is also a need for a filtering device that can be retrieved from a well bore safely and quickly. Further, there is a need for a filtering device that efficiently filters the drilling fluid while still allowing maximum flow through capabilities. These needs, as well as many others, will be met by the invention herein disclosed.  
         SUMMARY OF THE INVENTION  
         [0006]    A system for filtering a drilling fluid in a tubular string is disclosed. A first tubular member having a box end and a second tubular member having a pin end is provided. The box end is threadedly connected to the pin end, and wherein the connection forms a cavity. The connected tubular members have an internal bore therethrough.  
           [0007]    The system comprises a cylindrical flange member having a first passage and a second passage, and wherein the cylindrical flange member is fitted into the cavity. The system further comprises a cylindrical sleeve having an internal bore, and wherein the internal bore contains a fishing neck. The cylindrical sleeve contains a first opened end and a second opened end. An attachment member that attaches the cylindrical flange member to the first opened end of the cylindrical sleeve is included.  
           [0008]    The system further includes a screen member extending from the second opened end of the cylindrical sleeve, with the screen member having a plurality of openings. A pulling tool for engagement with the fishing neck is also included, with the pulling tool comprising: a mandrel with a first end and a second end; a plurality of dog members disposed about the mandrel; a spring urging the dog members into engagement with the mandrel&#39;s first end; and wherein the dog members have a shoulder that cooperates and engages with the fishing neck. The pulling tool may further comprise a shear pin attaching the dog members to the mandrel, and wherein the mandrel contains a slot, and wherein the shear pin is disposed within the slot so that the dog members can move axially relative to the mandrel.  
           [0009]    In one embodiment, the first passage and the second passage are disposed off-centered so that the first passage includes a first bore hole and a second bore hole, and the second passage includes a third bore hole and a fourth bore hole and wherein the attachment member comprises a first shear pin through said first and second bore hole and a second shear pin through said third and fourth bore hole. The cylindrical flange member may contain a first sealing surface that cooperates with the cavity in order to seal the cylindrical flange member relative to the internal bore.  
           [0010]    In one embodiment, the screen member is a cylindrical ribbed body. In another embodiment, the screen member is a cylindrical body having openings therein.  
           [0011]    A method of cleaning a drilling fluid of debris within a plurality of tubular members is also disclosed. The tubular members are threadedly connected, and the plurality of tubular members include a first tubular member having a box end and a second tubular member having a pin end. The box is threadedly connected to the pin, and wherein the box and pin cooperate to form a cavity. The method comprises placing a screen apparatus within the first tubular member. The screen apparatus comprises: a cylindrical flange member, with the cylindrical flange member having a first and second passage, and wherein the cylindrical flange member is fitted into the cavity; a cylindrical sleeve having an internal bore that contains a fishing neck; and a screen member attached to the cylindrical sleeve.  
           [0012]    The method further includes seating the cylindrical flange member within the cavity, and passing the drilling fluid through the internal bore. Next, the drilling fluid is flown through the screen member and debris is collected within the screen member. The method includes providing a pulling tool. The pulling tool contains: a mandrel with a first end and a second end; a plurality of dog members disposed about the mandrel; a spring urging the dog members into engagement with the mandrel&#39;s first end; and wherein the dog members have a shoulder that cooperates and engages with the fishing neck of the cylindrical sleeve.  
           [0013]    The method further includes lowering the pulling tool into the tubular member and contacting the dog members with the cylindrical sleeve. The dog members are allowed to contract about the mandrel. The protuberance is allowed to pass the fishing neck, and the pulling tool is lowered. The dog members then are allowed to engage the shoulder of the fishing neck. Thereafter, the pulling tool may be raised.  
           [0014]    The method further comprises shearing the first and second shear pin and releasing the cylindrical sleeve from the cylindrical flange. Next, the pulling tool is pulled with the attached screen member from the tubular member. The tubular members are pulled from the well bore, and the tubular members are threadedly disconnected. The cylindrical flange is retrieved.  
           [0015]    Also disclosed is an apparatus for filtering a drilling fluid. The apparatus comprises a flange member having a first and second passage. A cylindrical sleeve having an internal bore is included, with the internal bore containing a fishing neck. The apparatus further includes means for attaching the flange member to the sleeve and a screen member attached at a second opened end of the sleeve. In one embodiment, the first passage and the second passage are offset from center so that four bore holes are formed. In the preferred embodiment, the attaching means includes a first shear pin through the first and second bore holes and cooperating with a groove on outer diameter of the cylindrical sleeve and a second shear pin through the third and fourth bore holes and cooperating with the groove on the outer diameter of the cylindrical sleeve. In one embodiment, the flange member has a first seating surface that cooperates with a cavity that is formed from the pin and box connection.  
           [0016]    The apparatus may further include a pulling tool. The pulling tool includes a mandrel, a plurality of dog members disposed about the mandrel, and a spring urging the dog members into engagement with the mandrel&#39;s first end. The dog members will have a shoulder that cooperates and engages with the fishing neck of the sleeve.  
           [0017]    An advantage of the present invention includes the filtering of the drilling fluid so that down hole tools are protected from debris. Another advantage is that the apparatus has a completely open top end for full flow of the fluid into the screen. Yet another advantage is that the embodiments disclose different types of screens, namely a ribbed screen, perforated openings, and/or wire mesh. Still yet another advantage is in the event that the filter is inadvertently left in the tubular string, the design allows for retrieve from the tubular string, with retrieval possible to many thousand of feet below the surface of the earth.  
           [0018]    A feature of the present invention includes the screen has cylindrical walls. The screen has an open top end and a base with openings therein. Another feature is the flange that is connected via shear pins to the fishing neck. Yet another feature is use of a disclosed wire line pulling tool to retrieve the apparatus from the tubular string within a well bore. Still yet another feature includes the ability to pull significant forces via the wire line in order to retrieve the novel apparatus. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]    [0019]FIG. 1 is a cross-sectional plan view of the screen of the present invention.  
         [0020]    [0020]FIG. 2A is a plan view of the flange of the present invention.  
         [0021]    [0021]FIG. 2B is a top plan view of the flange of FIG. 2A disposed about the sleeve.  
         [0022]    [0022]FIG. 2C is a cross-sectional plan view of the flange pinned to the sleeve.  
         [0023]    [0023]FIG. 3 is a cross-sectional plan view of the screen seated within a tubular string.  
         [0024]    [0024]FIG. 4 is a partial cross-sectional plan view of the pulling tool of the present invention.  
         [0025]    [0025]FIG. 5 is a schematic view of the pulling tool approaching the apparatus within a tubular string.  
         [0026]    [0026]FIG. 6 is the schematic sequence view of FIG. 5 depicting the dogs of the pulling tool being pushed up mandrel.  
         [0027]    [0027]FIG. 7 is the schematic sequence view of FIG. 6 depicting the dogs engaged in fishing neck.  
         [0028]    [0028]FIG. 8 is the schematic sequence view of FIG. 7 depicting shear pins of the flange having been sheared.  
         [0029]    [0029]FIG. 9 is a schematic view of a derrick in place over a tubular string disposed within a well bore.  
         [0030]    [0030]FIG. 10 is the schematic sequence view of FIG. 9 depicting the tubular string being lowered into the well bore.  
         [0031]    [0031]FIG. 11 is the schematic sequence view of FIG. 10 depicting retrieval of the screen with the pulling tool of the present invention.  
         [0032]    [0032]FIG. 12 is a plan view of a second embodiment of the screen member. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0033]    Referring to FIG. 1, a cross-sectional plan view of the screen  2  of the present invention will now be described. The screen  2  includes an upper sleeve  3 , with the screen  2  having a generally cylindrical body  6  that extends to the base  8 . The upper sleeve  3  has an external outer diameter  10  that extends to the top radial surface  11 . Extending radially inward is the internal bore, seen generally at  12 . The internal bore  12  has a first internal bore surface  14 , having a beveled shoulder  15 , that extends to an increased internal bore surface  16 , with the internal bore surface  16  being also referred to as the fishing neck  16 . The fishing neck  16  extends to the smaller internal bore surface  18 .  
         [0034]    The upper sleeve  3  has extending therefrom a plurality of rods, with the rods seen generally at  20 . The rods  20  form the cylindrical body  6 . The rods  20  are spaced longitudinally in a general cylindrical fashion so that a screen is formed. The rods  20  act to sift out debris in the well bore fluid as will be more fully set out. The rods  20  are attached to the upper sleeve  3  via conventional means which in the preferred embodiment is welding. A plurality of cylindrical rings, namely ring  22 , ring  24 , ring  26 , ring  28  and ring  30 , are provided, with each individual ring having bored holes through which the rods are disposed there through. The rings  22 ,  24 ,  26 ,  28 , and  30  act to keep the rods  20  evenly spaced through deployment and use. The rings may be welded to the rods in order to keep the rings in place.  
         [0035]    As seen in FIG. 1, in the preferred embodiment, the screen  2 , and in particular the rods  20  have a taper from the connection point at  32  to the base  8 . The rods  20  may be welded to the sleeve  3  at  32 . The taper generally allows for easier insertion into the tubular members and withdrawal from the tubular members. The base  8  contains, in the preferred embodiment, perforations for passage of the fluid while at the same time providing for the capture of solids within the fluid.  
         [0036]    Referring now to FIG. 2A, a plan view of the flange  40  of the present invention will now be described. It should be noted that like numbers appearing in the various figures refer to like components. The flange  40  is pinned to the upper sleeve  3 , with the flange  40  being placed within a cavity formed in a pin and box connection as will be more fully described later. The flange  40  comprises a first outer diameter surface  42  that extends to the radially flat surface  44  which in turn extends to the first internal diameter surface  46  which in turn extends to the second internal diameter surface  48  of slightly smaller internal diameter so that a lip  50  is formed. The first outer diameter surface  42  also extends to the outer tapered surface  52  sometimes referred to as the seating surface  52  for seating within the cavity. FIG. 2A also depicts the passage  56  and passage  60  for placement of shear pin.  
         [0037]    [0037]FIG. 2B depicts a top view of the flange  40  disposed about the upper sleeve  3 : As seen in FIG. 2B, the shear pin  58  will cooperate with the passage  56  and the groove  57  within the outer sleeve  3  (also seen in FIG. 2C). The shear pin  62  will cooperate with the passage  60  and the groove  63  (also seen in FIG. 2C) within the outer sleeve  3 . Note that passage  56  effectively forms two passages  56   a ,  56   b  since the passage is disposed off-centered. Additionally, passage  60  effectively forms two passages  60   a ,  60   b  since this passage is also disposed off-centered. Hence, the shear pin  58  is disposed through passage  56   a ,  56   b . The shear pin  62  is disposed through passages  60   a ,  60   b.    
         [0038]    As seen in FIG. 2C, when the flange  40  is pinned into place with the upper sleeve  3 , the flow proceeds down the internal bore  12 . Note that with the pinned flange  40 , there is no internal exposed bore hole to flow. In prior art designs, the flange is pinned radially, thereby having boreholes open to the internal bore, and in turn, exposed to flow through the internal bore  12 . Due to turbulent flow of the fluid and debris contained therein, exposed bore holes in the internal bore  12  may lead to erosion and cutting away of metal, which in turn could lead to failure of the pins  58 ,  60  connecting the flange  40  to the upper sleeve  30 . The present invention solves that problem by not having any exposed bore holes in the internal bore, and instead has two passages ( 56 ,  60 ) bored off-centered.  
         [0039]    A cross-sectional plan view of the screen  2  seated within a tubular string will now be described with reference to FIG. 3. A first tubular member  70  is shown, with the tubular member  70  having external threads  72 , referred to as pin end  72 . A second tubular member  74  is shown, with the tubular member  74  having internal threads  76 , referred to as box end  76 . As is well understood by those of ordinary skill in the art, the first tubular member  70  is threadedly connected to the second tubular member  74 . Once the tubulars are connected, a cavity  78  is formed between the pin end  72  and box end  76 . As seen in FIG. 3, the flange  40  is seated within the cavity  78 . Thus, as fluid is flowed through the screen  2 , the rods  20  which form the walls of the screen  2  as well as the openings  8 A of the base  8 , will capture the particles to large to fit there through.  
         [0040]    Referring now to FIG. 4, the pulling tool  90  of the present invention will now be described. The pulling tool  90  comprises a mandrel having a first section  92  that has external threads  94  and internal threads  96 . The first section  92  has a radial shoulder  98 . A second section  100  of the mandrel has external threads  102  that threadedly connects with the internal threads  96 . The second section  98  has an outer cylindrical surface  104  that extends to the angled surface  106  which in turn extends to the generally cylindrical surface  108 . The generally cylindrical surface  108  then extends to the angled surface  110  and concludes at the generally radially flat surface  112 . The surfaces  106 ,  108  and  110  define a protuberance at the end of the mandrel. The second section  100  has a slot  114  milled there through.  
         [0041]    A spring  116  is disposed about the second section  100  of the mandrel. A first end  118  of the spring  116  is biased against the shoulder  98 , and a second end  120  of the spring  116  is biased against the dog member, with the dog member seen generally at  122 . The dog member  122  comprises a collar  124  that has a radially flat surface  126  that extends to the outer cylindrical surface  128  which in turn stretches to the plurality of dog legs, which in the preferred embodiments, there are contained four dog legs, three of which are seen in FIG. 4, namely  130 ,  132 ,  134 . The dogs are elongated having one end extending from the collar  124  and a second end having a protuberance thereon. More specifically, the second end of the dog  130  contains a first angled surface  136  that extends to the longitudinal surface  138  and then angled surface  140  which in turn extends to the radial surface  142 . The back side  144  of the dog is positioned next to the surface  108 . Each end of the other dogs are similar, and therefore, only the end of dog  130  will be described. A shear pin  146  is disposed through the collar  124 , with the shear pin  146  cooperating with the bottom surface  148  of the slot  114  for releasing from the fishing neck in those cases where it is not possible to retrieve the screen  2  with the pulling tool due to some problem, as will be appreciated by those skilled in the art.  
         [0042]    [0042]FIGS. 5, 6,  7  and  8  show a sequence of the pulling tool  90  being positioned within the tubular members to retrieve the screen  2 . FIG. 5 is a schematic view of the pulling tool  90  approaching the screen  2  within the tubular string. Thus, the upper sleeve  3  is pinned to the flange  40 , and the flange  40  is seated within the cavity  78 . The pulling tool  90  is lowered via wireline, as is well understood by those of ordinary skill in the art. As shown in FIG. 5, the spring  116  has fully extended the dog members.  
         [0043]    Next, the pulling tool  90  is lowered further, as seen in FIG. 6. The dogs of the pulling tool are pushed upward relative to mandrel  100 . As seen in FIG. 6, the radial surface  142  of the dog members will abut the top radial surface  11  of the sleeve  3  which causes the dogs to move upward which in turn compresses the spring  116 . By the dogs moving upward, the protuberance, and in particular, the surfaces  110 ,  108  can be lowered into the fishing neck portion/internal bore  16 .  
         [0044]    [0044]FIG. 7 is the next sequential view depicting the dogs engaged in fishing neck  16 , and more particularly, with the angled surface  136  engaging the shoulder  15  of the internal bore  16 . Thus, the operator would exert a pull on the wireline and that upward force is transmitted to the pulling tool  90  and in turn to the dogs. The continued exertion of force over a set amount will result in the shearing of the shear pins  58 ,  62  that held the flange  40  to the sleeve  3  (note the shear pins feature is seen in FIGS. 2A, 2B and  2 C). Once the shear pins shear off the flange  40 , the operator may pull out of the tubular members as seen in FIG. 8, which allows for retrieval of the screen  2 . The flange member  40  is left secured in place within the cavity  78 .  
         [0045]    If the shear pins  58 ,  62  of the flange  40  do not shear for some reason, the shear pin  146  disposed through the collar  124  will shear so that the pulling tool  90  can be retrieved from the tubular members. The shear pin  146  is sheared through application of an upward force of the bottom surface  148  of slot  114 . Once sheared, the spring  116  extends the dogs fully along past the protuberance, which allows the dogs to collapse so that the pulling tool can be pulled from the tubular as is well understood by those of ordinary skill in the art.  
         [0046]    The FIGS. 9, 10 and  11  show the sequence of placement of the screen  2 , and retrieval of the screen  2 . More particularly, FIG. 9 depicts a derrick  160  in place over a tubular string disposed within a well bore. The screen  2  with the pinned flange  40  may be placed within the box end of a tubular member by a worker located in the monkey bars  162  of the derrick  160 . The kelly or top drive, seen generally at  164 , will be operatively attached to the tubular members so that the drilling of a bore hole with the drilling bit  166  may proceed, as will be readily understood by those of ordinary skill in the art. Associated with the drilling bit  166  will be a bottom hole assembly  168 . The bottom hole assembly may contain electrical and microprocessor components embedded within tools such as measurement while drilling assemblies.  
         [0047]    As noted earlier, the screen  2  will filter out certain sized debris from the fluid. The worker will place the screen  2  within the seat of the box end of the tubing. The top drive  164  and tubing  74  is lowered by the draw works  170 , as is well understood by those of ordinary skill in the art.  
         [0048]    Referring now to FIG. 10, the schematic sequence view of FIG. 9 depicting the tubular string being lowered into the well bore will now be described. In the normal course of drilling, the operator will have the option of retrieving the screen  2  from the rig floor before coupling the tubular to another tubular joint. In other words, before the drilling tubular is threadedly mated to a second joint of drilling tubular, the operator on the rig floor can simply retrieve the screen  2 . If it is desired to keep the screen  2  within the drilling tubular, the second joint of drilling tubular is threadedly connected and therefore, the screen  2  with flange is held in place within the cavity  78  formed from the mating of the box end with the pin end, as previously described.  
         [0049]    Once the drilling tubulars are lowered into the well bore as seen in FIG. 11, the screen can no longer be removed by hand since the drilling tubulars are now threadedly coupled together. When it is desired to retrieve the screen  2 , a wire line unit  172 , as seen in FIG. 11, is rigged up by the operator in order to retrieve the screen  2  with the puffing tool  90  of the present invention. The pulling tool  90  would latch onto the fishing neck  16  of the screen  2  as previously described with reference to FIGS. 5, 6, and  7 . The screen  2  would then be pulled from the drilling tubulars as seen in FIG. 11. It should also be noted that FIG. 8 depicts the pulling tool  90  latched and pulling the screen  2  from the tubulars.  
         [0050]    [0050]FIG. 12 depicts a second embodiment of the screen member  2 A. More particularly, the screen member  2 A has perforated type of openings rather than the rod elements seen in FIG. 2. The upper sleeve  3  may be attached to the screen member via welding, with the fluid being directed through the internal bore  12  and into the generally cylindrical body  176 , wherein cylindrical body  176  contains the openings, and wherein an opening is denoted by the numeral  178 . Other types of screens are available such as wire mesh and radially oriented ribs encircling the cylindrical body.  
         [0051]    Although the present invention has been described in terms of specific embodiments, it is anticipated that alterations and modifications thereof will no doubt become apparent to those skilled in the art. It is therefore intended that the following claims be interpreted as covering all such alterations and modifications as fall within the true spirit and scope of this invention.

Summary:
An apparatus for filtering a drilling fluid. The apparatus comprises a cylindrical flange member having a first and second passage and a cylindrical sleeve having an internal fishing neck. An attachment pin attaches the flange member to the cylindrical sleeve. The apparatus further comprises a screen member attached to the cylindrical sleeve. In one embodiment, the first and second passage are disposed off-centered so that four bore holes are created. The attachment pin cooperates with a groove formed on the sleeve&#39;s outer diameter surface. The apparatus may further include a pulling tool. The pulling tool contains a plurality of dog members disposed about a mandrel, and a spring that urges the dog members into engagement with a protuberance on the mandrel. The apparatus further comprises a shear pin attaching the dog members to the mandrel and wherein the shear pin is disposed within a slot so that the dog members can move axially relative to the mandrel. In one embodiment, the screen member is a cylindrical ribbed body. A method of cleaning a drilling fluid is also disclosed.