Abstract:
A mud saver valve for retaining drilling fluid in the Kelly of a rotary drilling rig for insertion into a Kelly sub with an enlarged opening inside having a valve and hollow piston closing the flow in a first position and having flow through when the hollow piston is moved by flow against a spring to an open position compressing a spring to stack height, the spring being magnetized to provide magnetic latching to assist in holding the hollow piston in the open position at flow rates lower than it would otherwise be held open.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    N/A 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    N/A 
       INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISK 
       [0003]    N/A 
       BACKGROUND OF THE INVENTION 
       [0004]    The field of invention of this valve pertains to valves and more particularly to a valve assembly of the type known as a Kelly foot valve or a mud saver valve used in the rotary system for drilling oil wells. 
         [0005]    Conventional drilling of oil wells uses a drill string or sections of drill pipe to pump drilling mud down to a drilling bit at the bottom of the hole being drilled. The drill string also typically is rotated to provide rotary power to the drilling bit at the bottom of the hole. As the hole is progressively drilled deeper and deeper, sections of drill pipe are added to the drill string to allow continued drilling. These sections are typically 30 feet long. The wells are typically from 1000 to 20,000 feet deep. The drill string is supported in the rotary table of the rig and the upper drive section or Kelly is unscrewed. When it is unscrewed, the mud in the Kelly and the hose connecting the top of the Kelly to the other piping on the rig pours out onto the rig floor. 
         [0006]    The pouring of the drilling mud onto the rig floor is expensive because of the cost of the mud and is dangerous to the rig crew as it makes the floor slippery. 
         [0007]    Prior art valves have been inserted into the drill string at the foot or lower end of the Kelly with different characteristics and with different degrees of success. One solution has been to place a slim O.D. ball valve in the string which is operated manually by the crew. 
         [0008]    Other valves have been added which operate automatically based upon bore pressure or upon throttling of the fluid across the valves. These valves and the valve of the present invention are typically installed in a sub called a Kelly Saver. The term Kelly Saver comes from the fact that the section of square pipe at the top of the drill pipe which is engaged by the rotary table to turn the drill pipe is called the Kelly. Each time 30 feet more the well is drilled, the connection at the bottom of the Kelly is unscrewed and a joint of drill pipe is added to allow further drilling. This causes high wear and reduced life on the relatively expensive Kelly. A short inexpensive section of pipe is normally added to the bottom of the Kelly to take this wear and is typically called a Kelly Saver. 
         [0009]    Prior art valves characteristically do not allow the bore thru the valve to be opened for service access down into the string of drill pipe and then put back into service without having to disassemble the mud saver valve from the drill string to put it back together. Some of the alternatives, i.e. U.S. Pat. Nos. 3,698,411 and 3,965,980 require breaking a cap portion at the top of the valve to allow such service. U.S. Pat. No. 4,128,108 discloses a mud saver valve which requires that a pin be sheared to allow such service. U.S. Pat. No. 3,331,385 discloses a valve in which an extra part is added with special running tools to allow opening and then plugging the bore. This provides the limitations of making the hole available for servicing smaller, adding extra parts, and not allowing the critical wear surfaces to be retrieved easily for inspection and/or replacement. 
         [0010]    A second problem associated with prior art valves is that of allowing any pressure build-up below the mud saver valve to be sensed by pressure gages above the mud saver valve. This might occur when the mud is not being pumped. If unstable well conditions exist in which a blowout threatens, watching the pressure in the drill pipe above this valve is critical in the process of knowing how to control the well. Typical prior art valves such as those listed above included added components to act as check valves to allow flow in the direction going up the well. 
         [0011]    Prior art valve U.S. Pat. No. 4,899,837 provides a similar construction the present invention, however, when flow is reduced, it will prematurely start to close adding throttling wear to the internal components. 
       SUMMARY OF THE INVENTION 
       [0012]    The object of the present invention is to provide a mud valve assembly including a valve means which seals against a piston and prevents flow out of the Kelly portion of the drill pipe string above the rotary table or working level on a rotary drilling oil rig under the low head pressures associated with unscrewing the drill pipe at the rotary table or working lever, will cause the piston to move down and allow free flow under the higher pressures and flow rates which normally exist under drilling conditions, and will provide a magnetic latching of the valve in the open position to reduce the flow rate at which the valve tends to close. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a half section of the mud valve assembly of this invention in the first position which is closed and not allowing flow thru the valve. 
           [0014]      FIG. 2  is a section of the mud valve assembly taken thru the lines  2 - 2  on  FIG. 1 . 
           [0015]      FIG. 3  is a partial half section of the mud valve assembly as shown on  FIG. 1 . 
           [0016]      FIG. 4  is a partial half section of the mud valve assembly showing flow in the normal direction from above the valve to below the valve. 
           [0017]      FIG. 5  is a partial half section of the mud valve assembly showing flow in the reverse direction from below the valve to above the valve. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0018]    Referring now to  FIG. 1 , the mud valve assembly  10 , is contained within a section of drill pipe  11  which is normally called a Kelly Saver. The upper end of the Kelly Saver  12  has a female drill pipe thread  13  for connection to the Kelly and the lower end  14  has a male drill pipe thread  15  for connection to the top of the string of drill pipe extending down into the well being drilled. 
         [0019]    A tapered shoulder  16  is in the upper end of the Kelly Saver  11  for supporting the mud saver valve  10 . The bore  17  of the Kelly Saver  11  is the normal thru bore which would exist in a sub of this type, and the bore  18  is an enlarged bore in the Kelly Saver machined out to accommodate the mud saver valve assembly  10 . 
         [0020]    Mud saver valve  10  comprises tubular body  30 , spring  32 , piston  34 , valve  36  and stop body  38 . 
         [0021]    Referring now to  FIG. 2 , valve  36  comprises a central member  40 , an outer ring  42  and radial arms  44 . 
         [0022]    Referring now to  FIG. 3 , Tubular body  30  includes an outer tapered shoulder portion  50  which lands on the tapered shoulder  16 . Outer tapered shoulder  50  includes a seal groove  52  and a seal ring  54  which seal against the tapered shoulder  16 . Tubular body  30  also includes a top shoulder  56 , an internal female thread  58 , a seal bore  60 , an internal shoulder  62 , a reduced bore  64 , a seal groove  66 , and a lower end  68 . 
         [0023]    Piston  34  includes a long straight portion  70  and an enlarged portion  72 . The bore  74  of the piston  34  preferably matches the bore  17  of the Kelly Saver  11 . Piston  34  further provides a seal surface  76 , an upper shoulder  78 , a first tapered surface  80 , and a second tapered surface  82  which will also be called the first seal surface  82 . 
         [0024]    Spring  32  fits into the cavity  92  between the tubular body  30  and the piston  34  and pushes up against shoulder  94  on the piston  34  and reacts against the shoulder  62  on the tubular body  30 . The cavity  92  is a sealed cavity with the difference in the areas of the seal bore  60  and the reduced bore  64  acting as a piston area  77  subjected to the pressures within the drill pipe. Under sufficient pressure, this piston area  77  will cause the piston to move against the spring loading and move down until a stop is encountered. In the case of the preferred embodiment, the spring  32  is made of a square wire and stops the movement of the piston  34  when it reaches stack height. In the present closed position, the square wire spring  32  has the individual coils separated by a gap  98  as would be expected in any spring which has not been compressed to stack height. 
         [0025]    Stop body  38  provides a male thread  100  to engage the female thread  58  of the tubular body  30 , a lower tapered shoulder  102 , an upper tapered shoulder  104 , and internal profile  106  and an internal shoulder  108 . The lowered tapered shoulder  102  is engaged by the upper shoulder  78  ( FIG. 3 ) of the piston  34  to act as the upper stop in the movement of the piston  34 . The internal profile  106  with the internal shoulder  108  is intended for removal of the mud saver valve assembly from the Kelly Saver  11 . 
         [0026]    Valve  36  provides retrieval profile  110 , arms  44 , outer ring  42 , shoulder  112 , a first tapered surface  114 , and a second tapered surface  116  which will also be referred to as second sealing surface  116 . Second seal surface  116  is contacting and sealing against seal surface  82  in the position as shown. In this case sealing refers to preventing of substantial flow and is not intended to require “drop tight” sealing. It is relevant to notice that when the connection  15  ( FIG. 1 ) is unscrewed, all of the fluids inside the bottom of the valve are going to spill out. It is the additional gallons above the valve  36  in the Kelly which this valve is intended to keep from spilling on the rig floor. 
         [0027]    As pressure is increased from the top, the combination of the valve  36  and the piston  36  will move down until the gap between the shoulders  104  and  112  is closed. At that time the valve  36  is prevented from moving down further. Additional pressure will cause the piston  34  to move down against the spring force and therefore cause a separation in the seal surfaces  82  and  116 . As the combination of pressure and flow increase, the piston  34  will be moved fully down to its lower position and the valve will be fully open. 
         [0028]    Referring now to  FIG. 4 , arrows  120  thru  128  indicate the flow path thru the assembly when under flowing conditions. The piston  34  has moved fully down and the spring  32  is at its stack height. 
         [0029]    Arrow  120  is shown going thru the flow areas  46  and  48  between the arms  44  ( FIG. 2 ) of the valve  36 . The tapers  114  and  116  and the tapers  80  and  82  are shown to be instrumental in providing a relatively smooth flow path thru the valve to minimize turbulence and thereby promote longer service life without erosion. 
         [0030]    The force of the flow plus the pressure against the piston area at the top of the piston  34  keep the piston in the fully opened position. When these forces diminish below a minimum level, the piston will return to the position as shown in the  FIGS. 1 and 3 . The ability of the flow and pressure to keep the piston  34  in the lower position are directly proportionate to the values of the forces. It is desirable to have a force which will latch the piston  34  in the fully open position and fully release to allow quick closure of the piston  34  against the valve  36 . This can be done by magnetizing the square wire spring  32 . Magnetism works generally according to the square of the distance of the parts which are magnetized, so when the parts are very close a high attraction will exist. With small amounts of separation, the force will be reduced substantially, giving the snapping action you observe when you bring magnets close to one another. By magnetizing the spring (whether square wire or round wire), the mud saver valve assembly will stay open for lower flow rate and pressure combinations, and when it starts to close, it will close quicker. 
         [0031]    Referring now to  FIG. 5 , flow of fluids is shown to be coming up from the drill string into the Kelly by arrows  130  to  138 . This flow has lifted the valve  36  up so that the second sealing surface  116  has been separated from the first sealing surface  82  and caused a gap between. 
         [0032]    The valve  36  will stay in this slightly elevated position as long as flow exists from the drill string. This is essential so that the drilling personnel on the rig floor can monitor the pressures within the well when the pumps are not pumping as in normal drilling. 
         [0033]    In like manner the valve  36  can be simply retrieved from the bore by tools readily available on the drilling rigs which will engage the retrieval profile  110 . 
         [0034]    The foregoing disclosure and description of this invention are illustrative and explanatory thereof, and various changes in the size, shape, and materials, as well as the details of the illustrated construction may be made without departing from the spirit of the invention.