Abstract:
A three-part sub-assembly comprising a wire line retrievable spear. The spear having two fluid chambers. A diverter valve having a truncated, inverted cone valve seat is preferably threaded into the interior of the spear. A diverter valve stem, having back-to-back cones is located within the interior of the spear/diverter valve combination, with one of the cones having a linear extension which prevents the first cone from completely seating against the valve seat within the interior of the spear. The spear/diverter valve assembly and a spring-loaded piston is placed within the interior of the cylinder and utilizes an adjustable ring within the interior of the cylinder as an adjustment for varying mud weights.

Description:
BACKGROUND OF THE INVENTION 
   (A) Field of the Invention 
   This invention relates to apparatus for preventing the loss of drilling mud when the kelly is disconnected from the drill pipe. 
   (B) Description of the Prior Art 
   In the drilling of oil and gas wells, it is common practice to insert in the drilling string between the kelly and the drill pipe a valve to retain mud in the kelly when the drill string is broken. The advantages of using such a valve are well known and include saved mud cost, decreased chances of pollution, and increased safety to rig personnel. 
   Typical valves of the mud retaining type are illustrated in the following patents: 
   
     
       
             
             
             
           
         
             
                 
                 
             
             
                 
               Patentee 
               U.S. Pat. No. 
             
             
                 
                 
             
           
           
             
                 
               Taylor 
               3,331,385 
             
             
                 
               Garrett 
               3,698,411 
             
             
                 
               Litchfield, et al 
               3,738,436 
             
             
                 
               Williamson 
               3,965,980 
             
             
                 
               Liljestrand 
               3,967,679 
             
             
                 
                 
             
           
        
       
     
   
   All of the above listed patents include a downwardly opening spring loaded poppet type valve enclosed in a body having at least two parts. These two extra pieces in the drill string replace a single piece kelly saver sub, which functions to reduce wear on the kelly pin. The two-part body is generally longer than a standard kelly saver sub and consequently increases the length of the string which must be handled at the rig. In most offshore operating areas, it is mandatory that a lower manually operated kelly safety valve be included in the string at all times, which is another addition to the length of the string which must be handled. Thus, on offshore rigs, where the height of the derrick or mast is usually limited, it may be impossible to include mud retaining type valve with a two-part body. 
   An additional disadvantage inherent in mud retaining valves with two-part bodies is that the pin of the lower body member replaces the pin of the kelly saver sub and is therefore subject to tremendous wear. This wear limits the longevity of the pin and therefore the longevity of the valve. A solution to this problem has been to insert an additional short sub below the lower body member. However, this solution is not entirely satisfactory because it adds still more length to the string. 
   It sometimes becomes necessary to run wire line tools into the drill string to perform various downhole operations. It is therefore necessary that the mud retaining valve have means by which wire line tools may be run there through. In the device of certain of the prior art, these means take the form of a threaded plug screwed into the central portion of the movable poppet. To remove the plug of the apparatus, a tool is run into the string to engage a bolt headed portion of the plug and rotated to thereby unscrew the plug. In the valves of the other above cited patents, the central portion of the movable poppet includes a cap of a frangible material that may be broken out with a sinker bar. 
   Neither of these valves is entirely satisfactory. The “threaded plug” device requires a special tool for engaging and unscrewing the plug. The frangible cap of the other patents is not entirely satisfactory in that occasionally portions of the cap remain unbroken leaving jagged projections which may damage or sever the wire line. Also, the broken out portions of the cap form debris which impedes drilling. A further disadvantage of heretofore existing mud retaining valves is in the fact that none of them include means for adjusting the force with which their respective closure members are driven upwardly. The force may be insufficient to close the valve when heavy muds are used. When lighter muds are used, the force may be so excessive as to strain the mud pumps. 
   U.S. Pat. No. 4,128,108 to Bill Parker, et. al. is yet another example of a mud saver valve, and shows in its  FIGS. 2 and 3  a mud saver valve which, when the mud pumps are on, mud can flow through the interior of the valve, but which closes when the mud pumps are turned off based upon a spring-loaded closure mechanism which does not have the spring strength to close the valve until the mud pumps are turned off. As with this mud saver valve and with the other ones above referenced, once the mud pumps are turned off, the valve closes and the mud saver valve provides its desired purpose, that of preventing the mud from being spilled out onto the rig floor when the string of drill pipe is being broken down. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side view of a cylinder which is used in accordance with the present invention having three extensions at one end for holding a cylinder cap in place; 
       FIG. 2A  is a side view of a spear, partly in cross-section, which operates within the interior of the cylinder of  FIG. 1 ; 
       FIG. 2B  is another view of the cylinder of the spear of  FIG. 2  which has additional cross-sectional portions; 
       FIG. 3A  is a side view, in cross-section of a diverter valve which is threaded into one end of the spear illustrated in  FIGS. 2A and 2B ; 
       FIG. 3B  is across-sectional view through the diverter valve of  FIG. 3A  having wrench flats for tightening the diverter valve being threaded into one end of the spear of  FIGS. 2A and 2B ; 
       FIG. 4  is a side view of a diverter valve stem for use within the interior of the spear shown in  FIGS. 2A and 2B  and which moves between one end of the interior of the spear and the diverter valve depending upon whether the pressure is coming from the mud pumps being turned on at the earth&#39;s surface or whether the mud pumps are turned off; 
       FIG. 5  is a side view, in cross section, of a piston used in the cylinder of  FIG. 1 ; 
       FIG. 6  is a pictorial view of a spring used with the piston of  FIG. 5 ; 
       FIG. 7A  is a side view taken along the section line A—A of the adjustment ring of  FIG. 7B ; 
       FIG. 7B  is an end view of an adjustment ring having threads on its exterior which threads into a second end of the cylinder illustrated in  FIG. 1  for adjusting the tension of the spring illustrated in  FIG. 6 ; 
       FIG. 8A  is an end view of a cap designed to mate with one end of the cylinder illustrated in  FIG. 1 ; 
       FIG. 8B  is a cross-sectional view of the cap illustrated in  FIG. 8A ; and 
       FIG. 9  is a side elevation view of the device of the preferred embodiment of the present invention inserted in a radially enlarged portion of a kelly saver sub. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring now specifically to  FIG. 1  of the drawing, there is illustrated a cylinder  10  having a first end with three extensions  12 ,  14  and  16  which run parallel to the sidewall  18  of the cylinder  10 . The three extensions,  12 ,  14  and  16 , are equally spaced around the perimeter of the first end of the cylinder  10 . Each of the extensions has an end portion  15 ,  17  and  19 , respectively, which are pointed in towards the longitudinal axis  20  of the cylinder  10 . Each of the extensions  15 ,  17  and  19  also has a throughhole  21 ,  23  and  25 , respectively which will be used to house a set screw as will be explained hereinafter with respect to the cap illustrated in  FIGS. 8A and 8B . 
   Near the first end of the cylinder  10 , right before the beginning of the extensions  12 ,  14  and  16 , a groove  26  goes around the side wall  18  and is sized to receive an o-ring (not illustrated). At the second end of the cylinder  10 , there is an internally threaded portion  30  which is threaded to accept the external threads of the adjustment ring illustrated in  FIGS. 7A and 7B . 
   Referring now to  FIGS. 2A and 2B , there is illustrated a spear  40  having a first end  42  which is itself conventional and allows a wire line retrieval tool to be run into the wellbore and latch under its overhanging surface  44  to retrieve the spear  40  and the diverter valve  72  according to the present invention, should the need arise. As can best be seen in  FIG. 2B , the interior of the spear  40  has a chamber  46  of a given diameter which narrows down to a chamber  48  having a tapered end  50 , the purpose of which will be explained hereinafter with respect to the diverter valve stem illustrated in  FIG. 4 . In between the chambers  46  and  48 , there is a first truncated, inverted cone valve seat having a surface  174 , which although not critical, preferably has an angle of 45° from the longitudinal axis  54  of the spear  40 . The spear  40  also has an internally threaded surface  56  at the second end of the spear away from the end having the wire line retrievable end  42 . The diverter valve illustrated in  3 A and  3 B has an external thread which allows the diverter valve of  FIGS. 3A and 3B  to be threaded into the threads  56  of the spear  40 . 
   The spear  40  has three peripheral slots  51 ,  53  and  55 . Slot  51  is sized to receive three shear pins from the cap  130 ; slots  53  and  55  are each sized to accept a pair of o-rings, respectively. 
   The spear  40  also has an opening  60  which is connected into the chamber  48  illustrated in  FIG. 2B  and ultimately into the chamber  46  to allow fluids to pass from portions of the borehole below the mudsaver valve up through the chamber  46 , the chamber  48  and out through the hole  60  up to the earth&#39;s surface to allow such fluids to be checked for pressure, mud weight, etc. The chamber  46  has a threaded orifice  47  through the side wall around the chamber  46  for receiving a set screw to prevent the diverter valve  72  from backing out of the threads  56 . 
   Referring now to  FIG. 3A , there is illustrated in cross-section the diverter valve  72  according to the present invention having external threads along the portion  70  which allows the diverter valve  72  to be threaded into the internal threads  56  of the spear illustrated in  2 B. The diverter valve  72  also has a pair of peripheral grooves  71  and  73  on opposite sides of the threads  70  for receiving a pair of o-rings, respectively (not illustrated). The diverter valve  72  illustrated in  FIG. 3A  has an interior chamber  74  along its length but which opens up through a second truncated, inverted cone valve seat having a surface  78  to a larger volume bore  76  at one of its ends having an angled face, preferably having a 45° angle incline from the longitudinal axis  80  of the diverter valve  72  passing through the interior of the chamber  74 . The diverter valve  72  has a second enlarged diameter end  82 , illustrated with an end view in  FIG. 3B  which has two wrench flats  84  and  86  which enable the diverter valve  72  to be tightly threaded into the spear of  FIGS. 2A and 2B . 
   Referring now to  FIG. 4 , the diverter valve stem  150  is illustrated as having a front face  152  and a rear face  154  and a longitudinal axis  156 . It should be appreciated that the cone section  158  having the surface  152  and the cone section  160  having the surface  154  preferably are located back-to-back with only a small distance separating the two cones  158  and  160 . The surfaces  152  and  154  are each angled at approximately 45° to the longitudinal axis  156 . The valve  150  has an elongated stem  162 , sometimes referred to as a “rat tail” which is sized such that when the diverter stem valve  150  is located within the chamber  46  of  FIG. 2B , the tip of the stem  170  will reach the tip  178  of the cone shaped receptacle  50  and thus prevent the face  152  of the stem valve  150  from sealing with the surface  174  illustrated in  FIG. 2B , simply because the rat tail  162  can not travel any further. 
   Referring now to  FIG. 5 , there is illustrated a piston  90  having a first open end  92  and a second open end  94  and having a longitudinal axis  96  running along its length between the open ends  92  and  94 . The end  94  has an enlarged diameter portion  98  having a groove  100  around its perimeter for receiving a seal (not illustrated). The seal which preferably is used in the groove  100  is a so-called “loaded lip” seal. The larger diameter, raised portion  98  of the piston  90  has a surface  102  around its perimeter which serves as a base against which the spring  110  illustrated in  FIG. 6  can ride, wherein the spring  110  also surrounds the side wall  104  of the piston  90 . 
   Referring now to  FIG. 6 , the spring  110  is illustrated. It should be appreciated that the spring  110 , in use, is slipped over the side wall  104  of the piston  90  to rest against the surface  102 . 
   Referring now to  FIG. 7A , there is illustrated a side view taken along the section line A—A of  FIG. 7B  an adjustment ring  120  which has an external thread  122  around its outer perimeter. The adjustment ring  120  has a center flow passage  124  and a longitudinal axis  126  passing along through the interior of the flow passage  124 . 
   As illustrated in  FIG. 7B , an end view of the adjustment ring  120 , illustrates a pair of flats  127  and  129  into which two or more set screws can be used (not illustrated) to prevent the adjustment ring  120  from backing out of the cylinder  10 . The threaded surface  122  on the exterior of the ring  120  threadedly meshes with the internal threads  30  illustrated for the cylinder  10  in  FIG. 1 . The adjustment ring  120  also has a pair of holes  131  and  133  for receiving a tool for turning the ring  120  into the threads  30  of cylinder  10 . 
   Referring now to  FIGS. 8A and 8B , in which  FIG. 8A  is taken along the section lines A—A of  FIG. 8B , the end cap  130  has three outwardly extended arms  132 ,  134  and  136  which are equally spaced around the perimeter of the cap  130 . Each of the extensions  132 ,  134  and  136  has a groove for receiving one of the extensions  15 ,  17  and  19  illustrated in  FIG. 1 . As further illustrated in  FIG. 8A , each of the extensions  132 ,  134  and  136  also has a hole bored through, such as the hole  138  illustrated in the extension  132  illustrated in  FIG. 8A  for receiving a shear pin (not illustrated). 
   In assembling the devices which are illustrated in  FIGS. 1–8 , the diverter valve stem  150  is inserted within the chamber  46  of the spear  40  illustrated in  FIG. 2B , with the rat tail extension  162  pointed towards the cone shaped chamber  50  at the end of the chamber  48  in  FIG. 2B . As noted previously, the rat tail portion  162  is long enough to prevent the surface  152  of the diverter valve stem  50  from sealing against the surface  174  of the spear  40 . While the diverter valve stem  150  is so located within the spear  40 , the diverter valve  72  is threaded into the threaded end of the spear  40  having the threads  56 . With the spring  110  in place around the piston  90 , the piston  90  is inserted into the cylinder  10 , with the enlarged end  98  going in first, to a distance to expose at least a portion of the threads  30  of the cylinder  10  and then the adjustment ring  120  is threaded into the threaded end of the cylinder having the threads  30  of the cylinder, to thus threadedly engage the threads  122  of the adjustment ring  120 . At this point, the combined spear, diverter valve and diverter valve stem can be dropped into the unthreaded end of the cylinder  10 . Thereafter, the cap  130  has to be manipulated, as by a slight rotation, to have its extensions  132 ,  134  and  136 , pass by the extensions  12 ,  14  and  16  of the cylinder  10 . By manipulating the cap  130 , the three grooves in the extensions  132 ,  134  and  136  mesh with the three extensions  15 ,  17  and  19 , respectively. 
   Referring now to  FIG. 9 , the assembled valve of the preferred embodiment of the invention, designated generally by the numeral  210 , is illustrated in  FIG. 9  disposed within a radially enlarged portion  216  of a kelly saver sub  217 . Kelly saver sub  217  has a box  218  at the upper end thereof to accommodate the pin of the kelly (not shown) and a pin  220  at the lower end thereof for insertion into either the drill pipe or a lower kelly safety valve (neither shown). The kelly saver sub  217  also includes an optional rubber bumper  221  or a bronze wear pad which serves to space the kelly from the surface casing and thereby prevents wear to both. 
   In the operation of the mudsaver valve illustrated in  FIGS. 1–9 , the drilling fluid being pumped down from the earth&#39;s surface will enter the box end  218  illustrated in  FIG. 9  and come into contact with the top of the mudsaver valve in accordance with the invention and flow down through the mud saver valve by virtue of the fact that the piston has been pushed down by the pressure being pumped from the earth&#39;s surface, thus overcoming the spring illustrated in  FIG. 6 . The mud being pumped down goes first through the orifice  60  and then into the chambers  48  and  46 . However, because the diverter stem valve  150  is forced against the surface  78  of the diverter valve  72 , the mud is then pumped around the exterior of the spear  40  and against the surface  98  of the piston  90 , and will overcome the spring pressure of spring  110  to allow mud to be pumped through the interior of the piston  90 , and out through the pin end  220  illustrated in  FIG. 9 . 
   Whenever the mud pumps are cut off at the earth&#39;s surface, indicating that the pipe joints can be broken out, the spring pressure from the spring illustrated in  FIG. 6  then pushes the enlarged end  98  of the piston  90  up against the lower end of the cap  130 . Thus, when the pipe joints are broken out, the mud is prevented from passing out the lower end of the cylinder  10  because of a metal-to-metal seal between the cap lower surface and the upper surface on the piston. The lower surface of the cap and the upper surface of the piston use tungsten carbide inserts, and/or are coated with tungsten carbide to prevent excessive wear to either part. 
   Despite the mud saver valve according to the present invention being essentially shut in when the mud pumps are turned off, the downhole pressure of the fluids can be measured by the fact that the diverter valve stem  150  is moved off of its engagement with the face  78  of the diverter valve because of the spring  110  and hence mud can then flow through the diverter valve up to and through the chambers  46  and  48  and then out through the orifice  60  to travel back up to the earth&#39;s surface where the pressure and other parameters related to the downhole fluids can be measured.