Abstract:
An apparatus ( 100 ) and a method to prevent undesired objects (not shown) when communication conduit (not shown) is disposed therethrough. The apparatus ( 100 ) and method include a flapper assembly ( 150 ) to selectively open and close when objects (not shown) larger than the communications conduit (not shown) are desired to pass therethrough.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    Well drilling operations are typically performed using a long assembly of threadably connected pipe sections called a drillstring. Often, the drillstring is rotated at the surface by equipment on the rig thereby rotating a drill bit attached to a distal end of the drillstring downhole. Weight, usually by adding heavy collars behind the drill bit, is added to urge the drill bit deeper as the drillstring and bit are rotated. Because subterranean drilling generates a lot of heat and cuttings as the formation below is pulverized, drilling fluid, or mud, is pumped down to the bit from the surface. 
         [0002]    Typically, drill pipe sections are hollow and threadably engage each other so that the bores of adjacent pipe sections are hydraulically isolated from the “annulus” formed between the outer diameter of the drillstring and the inner diameter of the wellbore (either cased or as drilled). Drilling mud is then typically delivered to the drill bit through the bore of the drillstring where it is allowed to lubricate the drill bit through ports and return with any drilling cuttings through the annulus. 
         [0003]    Measurements of formation density, porosity, and permeability frequently need to be taken before a well is drilled deeper or before a change in drilling direction is made. Often, measurements relating to directional surveying are needed to ensure the wellbore is being drilled according to plan. Preferably, these measurements and operations can be performed with a measurement while drilling assembly (MWD), whereby the measurements are made in real-time at or proximate to the drill bit and subsequently transmitted to operators at the surface through mud-pulse or electromagnetic-wave telemetry. While MWD operations are possible much of the time, manual measurements are often desired either for verification purposes, or the measurements desired are not within the capabilities of the MWD system currently in the wellbore. Additionally, measurements may be required when a drillstring is not in the wellbore, for instance during workover or production. For this reason, measurements are often required by “wireline” or other devices absent the presence of the drillstring. Various tools, communications conduits, and method are used in the oilfield today to perform measurements or other operations. 
         [0004]    For the purposes of this disclosure, the term “tool” is generic and may be applied to any device sent downhole to perform any operation. Particularly, a downhole tool can be used to describe a variety of devices and implements to perform a measurement, service, or task, including, but not limited to, pipe recovery, formation evaluation, directional measurement, and workover. Furthermore, the term communications “conduit,” while frequently thought of by the lay person as a tubular member for housing electrical wires, in oilfield parlance, is used to describe anything capable of transmitting fluid, force, electrical, or light communications from one location (surface) to another (downhole). For this reason, the term conduit, as applied with respect to the present disclosure is to include wireline, slick line, coiled tubing, fiber optic cable, and any present or future equivalents thereof. 
         [0005]    Often, while wireline or other communications conduit operations are being performed, other work and operations continue on the rig floor. Invariably, accidents occur and objects are dropped down the wellbore where the wireline operations are occurring. This can be the result of human error (or, in some circumstances, intentional behavior on the part of rig personnel), or can be the result of the failure of other equipment. No matter how undesired objects get dropped down the wellbore, they must be retrieved, as such objects can often damage or render inoperable any drilling, production, or measurement equipment located downhole. To retrieve these objects, an expensive and time consuming “fishing” operation is undertaken. Fishing involves the deployment of specialty equipment and personnel to “fish” downhole and retrieve the dropped equipment. This process can be simplified if it is known precisely what has been dropped downhole, but this is not always the case. 
         [0006]    Also, objects can fall down the wellbore without personnel on the rig even becoming aware of the object downhole until after equipment has been disrupted or damaged. In this circumstance, the expensive and costly fishing expedition is usually followed with an equally expensive and time-consuming retrieval, repair, and replacement procedure to correct the damaged equipment. 
         [0007]    Wireline (or other communications conduit) operations present a special problem in “protecting” the wellbore from foreign objects. Typically a hole cover or other prophylactic device can be placed over the open hole, but when operations are proceeding, this is not an option. A device that prevents the inclusion of foreign objects into the wellbore while still allowing the reciprocating of communications conduit therein is needed. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    The deficiencies of the prior art are addressed by a device including a flapper assembly. The device would preferably be placed in a tubular string and would include a bore therethrough preferably large enough for tools disposed upon a communications conduit to pass therethrough. The flapper assembly would include at least two flapper devices, whereby each flapper would be able to raise and lower when actuated. When in the down position, the flappers would have sufficient gap therebetween to allow passage of the communications conduit therethrough but would prevent the passage of objects larger than the communications conduit. In the open position, the flappers would allow the passage of tools and other objects therethrough. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    For a more detailed description of the preferred embodiments of the present invention, reference will be made to the accompanying drawings, wherein: 
           [0010]      FIG. 1  is a sectioned view profile sketch of a tool trap assembly in accordance with a preferred embodiment of the present invention. 
           [0011]      FIG. 2  is a top view sketch of the tool trap assembly of  FIG. 1  showing a flapper assembly thereof in greater detail. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0012]    Referring initially to  FIG. 1 , a tool trap assembly  100  is shown. Tool trap assembly  100  preferably includes a top sub  102 , a bottom sub  104 , a connection nut  106 , and a quick union insert  108 . Tool trap assembly  100  is attached atop a tubular string (not shown) by a threaded profile  110  of connection nut  106 . Preferably, connection nut  106  is threaded atop the string to be protected and bottom sub  104  is engaged therein. Bottom sub  104  includes a seating flange  112  that is received within the threaded connection nut  106  and seats atop tubular string (not shown). With bottom sub  104  seated within nut  106 , quick union insert  108  is threaded down shank  114  of bottom sub  104  and engaged within a second threaded profile  116  of connection nut  106 . Quick union insert  108  is preferably tightened until flush with nut  106  and secured in place by engaging a set screw  118  therein. Thereafter, upper sub  102  (if not already made-up with lower sub  104 ) is threadably engaged atop lower sub  104  at threaded profile  120 . Preferably, an elastomeric (or any other type known to one skilled in the art) seal  122  maintains a hydraulic seal between top sub  102  and lower sub  104 . 
         [0013]    Top sub  102  is preferably configured to allow wireline tools (or tools disposed upon any other form of “conduit” known to one of ordinary skill in the art) to selectively pass therethrough. Top sub  102  also preferably includes a threaded outer profile  124  at its upper end for connection with other threaded devices. It is preferred (but not required) for inner threaded profile  110  of connection nut  106  to correspond with outer threaded profile  124  of top sub  102  so that a threaded joint in a tubular string (not shown) may be separated and tool trap assembly  100  inserted therebetween. Top sub  102  also preferably includes an inside radial seal  126  so that tool trap assembly  100  may sealingly engage a sealing profile from a device connected thereto. Top sub  102  includes an inner bore  128  that opens up to an inner cavity  130  within which lower sub  104  is received. Lower sub  104  preferably includes an inner bore  132  extending from upper sub  102 , through shank  114  and past seating flange  112  to a device mounted therebelow. 
         [0014]    Referring now to  FIGS. 1 and 2  collectively, housed within cavity  130  of upper sub  102  and atop an upper end  134  of lower sub  104  is a flapper assembly  150 . Flapper assembly  150  preferably includes a pair of flappers  152  that are held in a down, or closed, position by a plurality of retainer springs  154 . Flappers  152  of assembly  150  act to prevent anything larger than a communications conduit to pass therethrough, where the communications conduit can pass through flapper gap  140  with the flappers  152  in the down position. With flappers  152  in the down, or closed, position as shown, anything dropped down through bore  128  of upper sub  102  (or through any bore thereabove) will be halted by flappers  152  and will not be able to continue down through bore  132  of lower sub, or to any location therebelow. Flappers  152  act to protect downhole equipment and operations from the damage (or costly service interruptions) that can result from the accidental dropping of an object down the hole. 
         [0015]    When the opening of flappers  152  of assembly  150  is desired, a hydraulic cylinder  160  connected to a lifting T-bar  156  is actuated, thereby temporarily lifting flappers  152  and allowing items larger than the communications conduit therethrough. Activation of cylinder  160  drives T-bar  156  upward, thereby pushing and rotating actuator arms  158  connected to flappers  152 . When the object desired to pass flapper assembly  150  is clear of flappers  152 , cylinder  160  is deactivated and springs  154  close flappers  152  to again block access to bore  132  below. While a hydraulic cylinder  160  is shown opening and closing flapper assembly  150 , it should be understood by one of ordinary skill in the art that various other devices can be employed to perform this task, including, but not limited to, electrical motors and pneumatic cylinders. 
         [0016]    Hydraulic cylinder  160  is preferably constructed as an ordinary device, one that includes a hydraulic piston  162  connected to a shaft  164  that is lifted when pressure through a port  166  is increased. Preferably, a spring  168  biases against upward movement of piston  162  so that shaft  164  is lowered back to its original position when pressure within port  166  is lowered. When flappers  152  are desired to be opened, pressure is increased in port  166 , thus driving up shaft  164  and thereby raising T-Bar  156 . T-Bar  156  thereby pushes up and rotates actuator arms  158  which are connected to flappers  152  through shafts  170 . Shafts  170  are engaged through flappers  152  and include flat profiles that mate with corresponding profiles of flappers  152  at an interface  172 . Furthermore, shafts  170  are preferably held in place and hydraulically isolated with respect to tool trap assembly  100  by shaft fittings  174 . O-ring seals  176 ,  178  isolate shaft fittings  174  from tool trap assembly  100  and from shafts  170 . Finally, a removable, wear ring  190  is preferably engaged within a socket  192  of each flapper  152  to protect flapper  152  from abrasion and wear from continued rubbing contact with communications conduit run therethrough. 
         [0017]    Wear ring  190  can be of any material known to one of ordinary skill in the art but is preferably constructed as round stock for simplicity. In choosing round “bar” stock for wear ring  190 , the manufacturing of flappers  152  is simplified. To create sockets  192  for round bar wear rings  190  within flappers  152 , a standard circular hole is drilled therethrough and the “hole” is truncated by removing a section thereof, thereby leaving a C-shaped socket  192  behind to hold a bar-stock wear ring  190 . Wear ring  190  can be constructed from various materials of various hardness, depending on the philosophy of the operator. For instance, if the communications conduit is desired to be saved from wear with flappers  152 , a soft material can be selected for wear ring  190 , thereby making wear ring  190  the sacrificial device. Alternatively, if wear on the communications conduit is not a concern, wear ring  190  can be constructed as a hard material, like tungsten carbide, or hardened steel, to ensure that the wear ring  190  has longevity and requires infrequent replacement. 
         [0018]    While a preferred embodiment for the locking mechanism of tool trap assembly  100  is shown, it should be understood by one skilled in the art that departures from the specific embodiment disclosed can still be within the scope and meaning of the invention as claimed.