Abstract:
A retaining apparatus is provided for preventing the separation and loss of a down-hole drive motor and associated drill bit from the drill string due to gyroscopic precession of the motor housing resulting from counter torque produced by the drill bit. The retaining apparatus includes a collet, an expander with interchangeable nozzles and a fluid bypass flange.

Description:
FIELD OF THE INVENTION 
   This invention relates generally to apparatuses for capturing and thereby preventing the disassembly of a down-hole mud motor as a result of counter rotation of the power section relative to a portion of the motor housing. 
   GENERAL BACKGROUND 
   Down-hole tools such as mud motors that are hydrostatically driven and therefore rotatable relative to the drill string are used to drive the drill bit. Rather than having a larger surface motor rotate the entire drill string, a down-hole mud motor rotates the drill bit. This arrangement is especially useful in horizontal bores. 
   Generally, such motors utilize some type of bearing so that the down-hole mud motor is allowed to rotate relative to the drill string. These down-hole motors are subjected to a very hostile environment such as exposure to high heat, vibration, and high velocity solids. Accordingly, it is not uncommon for the motor bearings to fail. Bearing failure causes the motor to stall. However, since the operators of the drilling operation are ordinarily unaware of such failure and thus continue driving the down-hole motor, the continued rotational force applied to the drill bit by the down-hole mud motor power section has a tendency to rotate the portion of the motor housing located below the power section. Rotation of these sections of the down-hole motor housing eventually results in at least one of the sections and the drill bit becoming separated from the remainder of the down-hole mud motor housing and possibly being lost in the well bore. If the motor housing and bit are lost in the well bore, generally it is time consuming and expensive to perform fishing operations in an attempt to retrieve the lost components. When these relatively expensive components cannot be retrieved, they generally continue to impede further drilling operations. 
   Various methods have been employed within the art to overcome the above stated problem. For example Falgout and Beasley, in U.S. Pat. Nos. 6,540,020 and 5,165,492 respectively, disclose a valve having means for biasing the valve against rotation of the housing in a manner that allows the flow of fluid to the motor to be cut off if the fluid motor housings and bit separate. It is suggested that this restriction in fluid flow will alert the operators on the surface that a problem exists and thus initiate a removal of the mud motor procedure for inspection. A sudden disruption of flow in the form of a blockage at high pressure in excess of 6000 psi certainly tends to get someone&#39;s attention when the surface pump is destroyed as a result. In addition, once the fluid to the down-hole motor is shut off, it becomes very difficult to withdraw the drill string. In such cases, extraordinary measures must be taken to free the bit manually and retrieve the drill string. 
   The present invention is directed to overcoming or minimizing one or more of the problems discussed above. 
   SUMMARY OF THE INVENTION 
   A retaining apparatus is provided for preventing the separation and loss of a down-hole drive motor and associated drill bit from the drill string due to gyroscopic precession of the motor housing resulting from counter torque produced by the drill bit. The retaining apparatus includes; a collet, an expander pin with interchangeable nozzles, and a fluid bypass flange. 
   BRIEF DESCRIPTION OF THE DRAWINGS 
   For a further understanding of the nature and objects of the present invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings, in which, like parts are given like reference numerals, and wherein: 
     FIG. 1  is a partial view of a down-hole drill string; 
     FIG. 2  is a cross-section view of retainer assembly used to capture the drill bit and motor assembly shown in  FIG. 1  in the stand-by position; 
     FIG. 3A  is a cross-section view of the retainer assembly in the capture position; 
     FIG. 3B  is a longitudinal continuation of the cross-section view shown in  FIG. 3A  showing the drive motor stator separation; and 
     FIG. 4  is an isometric exploded view of the retainer assembly. 

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   As may be seen in the stylized view of a drill string  10 , shown in  FIG. 1 , the drill string  10  is composed of a series of tubular members  12 ,  13 ,  14 ,  15 ,  16  threaded together to form a hollow-core cylinder. Preferably, the tubular members  12 ,  13 ,  14 ,  15 ,  16  are joined together by threaded connections that employ right hand threads. A drill bit  20  is depicted rotatably connected at the bottom of the drill string  10  via a down-hole motor assembly  25  located within the lowermost tubular members  15 ,  16 . The down-hole motor  25  includes a housing  23 , a power section  24 , and a bearing section  22 . 
   To effect rotation of the drill bit  20  relative to the drill string  10 , the conventional down-hole motor  25  located within the core of the drill string  10  is operated by pumping drilling fluid through the core of the drill string  10  and the motor  25 , imparting a rotational movement to the drill bit  20 . Generally the drill bit  20  is rotated in a clockwise direction, as viewed from a vantage point above the drill string  10 , as indicated by an arrow  27  adjacent the bit  20 . 
   Since the drill bit  20  is rotatable relative to the drill string  10 , the bearing section  22  is provided to reduce frictional wear between the two members and generally includes at least two sets of bearings  26 ,  28  spaced longitudinally apart to reduce rotational wobble of the drill bit  20  relative to the drill string  10  as it rotates. 
   In some cases the bearings  26 ,  28  cease to operate properly so that the drill bit  20  does not freely rotate relative to the drill string  10 , in which case the clockwise rotational force applied to the drill bit  20  is also applied to the drill string  10  through the bearings  26 ,  28  and, in particular, to the lower tubular member  16  of the housing  23 . Since the lower tubular member  16  is attached to the upper tubular member  15  via right hand threads  40 , the clockwise rotation of the lower tubular member  16  tends to unscrew the lower tubular member  16  from the upper tubular member  15  until they separate as shown in  FIG. 3B . 
   Referring to  FIG. 2 , a longitudinal cross-sectional view of a portion of the drill string  10  that includes the joint formed by the coupling of tubular members  14 ,  15  is shown. It should be noted that the tubular member  14  is a typical sub-section of the tubular drill string  10  and requires no special machining and serves only to house the upper portion of the retainer assembly  30 . The retainer assembly  30  includes a tubular central pin member  32 , a nozzle member  33 , a collet member  34 , and a flange member  36  as shown in  FIG. 4 . 
   As seen in  FIG. 4 , the collet  34  may be defined as an elongated tubular with a shoulder or collar  44  at one end and an upset  35  at the other. The collet  34  also has a plurality of radially spaced slits  45  extending from the collar  44  to the upset end  35 , thereby allowing the collet  34  to be compressed for insertion into the motor rotor  42 . 
   As seen in  FIG. 2 , a shoulder  38  is formed at the base of the internal threads  40  located at the upper end of the sub-section  15  for seating the flange member  36 . The central pin  32  and collet member  34  pass through the flange member  36  and are connected to the motor rotor member  42 . Unlike conventional retaining members the instant retainer assembly  30  is not threadably connected to the rotor  42 . Instead the end of the motor rotor  42  is counter-bored  37  to accept one end of the pin  32  and the upset portion  35  of the expandable collet  34 . Compression of the collet member  34  is required for insertion into the counter-bore  37  in the rotor  42  where the upset portion  35  of the collet member  34  is allowed to expand into a cooperative cavity  39  in the rotor  42 , counter bore  37 . Insertion of the hollow pin  32  through the center of the collet  34  maintains the upset  35  in the rotor cavity  39 . The hollow or tubular pin  32  is threadably retained within the collet  34 , as indicated in  FIG. 4 , by engagement of the external threads  50  on the pin  32  with the internal threads  52  within the collet  34 . Rotation and vibration of the rotor  42  is therefore allowed without the possibility of retainer separation. 
   As seen in  FIG. 3A , if separation of the motor drive sub-section  15  occurs relative to the sub section  16  as seen in  FIG. 3B , the collar portion  44  of the collet  34  comes into contact with the flange member  36 , thus preventing loss of the drive motor assembly  22  and bit  20 . 
   It has been found that it is not only unnecessary to notify topside personnel of an uncoupling situation down-hole, it may also in fact be detrimental to the pumping operation. Therefore, fluid flowing through the drill string  10  is allowed to flow freely through a plurality of orifices  46  located in the flange member  36  without interruption should an uncoupling situation occur. Since a pressure loss occurs as a result of the decoupling, sufficient warning is given. 
   It should also be noted that the tool joint located between sub-sections  14  and  15  is not affected by counter rotation and therefore only serves to lock the flange  36  in position relative to the joint. 
   Because many varying and different embodiments may be made within the scope of the inventive concept herein taught, and because many modifications may be made in the embodiments herein detailed in accordance with the descriptive requirement of the law, it is to be understood that the details herein are to be interpreted as illustrative and not in any limiting sense.