Abstract:
A check valve assembly for the bottom of a casing string with increased open area is provided. Multiple check valves are provided for assurance of ultimate closure. Bypass flow paths are available during run in that increase the normal available open area from about 3 square inches to a range of about 10 square inches and even higher. Components freely float during run in to provide the greater open area and are subsequently repositioned with known techniques of dropping a ball and pressurization when the casing has reached the desired depth.

Description:
FIELD OF THE INVENTION 
     The field of the invention relates to float valves for use in running casing into wellbores or running other downhole tools into a wellbore with close clearances at higher speeds. 
     BACKGROUND OF THE INVENTION 
     Rig time is costly to well owners and operators. One way to cut down on rig time is to be able to increase the rate at which casing is run into a wellbore. Casing normally includes a check valve near its lower end. This valve can be locked open during running to allow fluid entry inside of the casing. This check valve contains a fairly small open area in the order of approximately 3 square inches when casing in the order of 9⅝ to 13⅜ inches in diameter is being run. The small opening size in this check valve limits the rate of advancement of the casing into the wellbore. An overly aggressive advancement rate results in undesirable fluid pressure buildup on the formation adversely affecting well control and future productivity of the formation. 
     Another typical choke point apart from the check valve at the bottom of a casing string is through the wiper plug near the top of the casing when it is being run in. Typically the cross sectional area in the flow bore through the wiper plug assembly is in the order of about 3 square inches. 
     Accordingly, it is an object of the present invention to optimize the available open area during run in to allow higher running rates for the casing. The apparatus of the present invention is useful not only in running casing but can also be useful in running downhole tools in wellbores with fairly low clearances. 
     SUMMARY OF THE INVENTION 
     A check valve assembly for the bottom of a casing string with increased open area is provided. Multiple check valves are provided are provided for assurance of ultimate closure. Bypass flow paths in the area of the check valve and the wiper plug are available during run in that increase the normal available open area from about 3 square inches to a range of about 10 square inches and even higher. Components freely float during run in to provide the greater open area and are subsequently repositioned with known techniques of dropping a ball and pressurization when the casing has reached the desired depth. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1 a-d  illustrate a section view of the apparatus of the present invention during run in; 
     FIGS. 2 a-d  illustrate a section view of the apparatus of the present invention when the desired depth is reached; and 
     FIGS. 3 a-d  illustrate a section view of the apparatus of the present invention in a condition ready for cementing. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The apparatus A of the present invention is shown in FIGS. 1 a-d . A valve  10  has a sliding sleeve  12  within bore  14 . In the run in position the ports  16  are in the open position to allow flow represented by arrow  18  to run through them as the apparatus A is advanced. A running tool  20  is connected to top sub  10  at thread  22 . The running tool  20  is a known design and it is connected to the casing  24  by a series of collets  26  locked into a groove  28 . The liner wiper plug is connected to a seal extension  30  from the setting tool by shear screws  5 . 
     The liner wiper plug  46  has an inner mandrel  40  with ports  32 . A floating sleeve or moveable component  34  is shown in its uppermost position such that ports  36  on floating sleeve  34  line up with ports  32  on the inner mandrel  40 . Flow represented by arrow  38  can go through these aligned ports. Floating sleeve  34  sits in a receptacle or stationary component  40  which has openings  42  to allow flow to go through them as represented by arrow  44 . 
     The wiper plug  46  is a known construction with the addition of a floating sleeve  34  and the receptacle  40 . 
     Referring now to FIG. 1 d , the casing  24  has a bottom opening  48  through which flow enters when the casing  24  is advanced downhole as shown by arrow  50 . A lower check valve  52  is biased upwardly by spring  54 . In the run in position of FIG. 1 d , spring  54  is compressed because the upper check valve  56  is bearing down on check valve  52  to allow flow around check valve  52  as depicted by arrow  58 . A rod  60  keeps spring  62  compressed allowing flow around check valve  56  as represented by arrows  64 . 
     A spider  66  is threaded to the casing  24  at thread  68  and has a series of flow ports  70  to allow flow therethrough as represented by arrows  72 . A series of collets  74  extending from spider  66  retain rod  60  and keep it from moving uphole in response to a bias force from spring  62 . A lock ring  76  retains the collets  74  in a run in position shown in FIG. 1 d.    
     Further uphole, a spider or fixed component  78  is secured by threads to the casing  24  and has a series of ports  80  to allow flow as represented by arrows  82 . In the middle of spider  78  is floating sleeve  84  to which is connected a cone  86  with a shear pin  88 . Floating sleeve or moveable component  84  has a series of slots  90  which permit flow therethrough as shown by arrows  92 . Floating sleeve  84  further permits flow through a central bore represented by arrow  93 . The flow represented by arrow  93  goes through an opening in the cone  86  as shown in FIG. 1 d . Cone  86  has a peripheral clearance inside casing  24  to allow flow to go around it on the outside as shown by arrows  94 . Floating sleeve  84  has a lower flange  96  which is sized to contact the lock ring  76  below it to ultimately release the collets  74  to allow the rod  60  to move uphole as will be described later. 
     Accordingly, in the run in position flow enters casing  24  as represented by arrow  50 . Flow continues around check valve  52  which is in the open position as represented by arrows  58 . Flow continues around check valve  56  as represented by arrow  64 . Thereafter flow goes through the spider  66  represented by arrow  72  and then through the spider  78  as represented by arrows  82  or alternatively through the floating sleeve  84  through its slots  90  as represented by arrows  92  or through a central passage in the floating sleeve  84  as represented by arrow  93 . Thereafter flow is through the wiper plug  46  (FIG. 1 c ) as represented by arrows  44  and back into the seal extension  30  as represented by arrows  38  upwardly through bore  98  (FIG. 1 b ) and out the port  16  (FIG. 1 a ) as represented by arrow  18  to the top of the hole. 
     The run in position having been described, the further operation of the tool as depicted in FIGS. 2 a-d  will now be explained. In the position shown in FIG. 2, downhole movement of the casing  24  has ceased as it has reached its appropriate depth. Comparing FIGS. 2 c  and  1   c , it can be seen that the float sleeve  34  has shifted downwardly to its lowermost position supported by receptacle  40  which has in effect closed off ports  32  in receptacle  40  because ports  36  are no longer in alignment with ports  32 . Looking further down and comparing FIGS. 2 d  and  1   d , it can be seen that the assembly of the cone  86  and float sleeve  84  have moved downwardly in tandem such that spider  78  now supports cone  86 . In this position, the rod  60  has retained its position from FIG. 1 d  and accordingly the check valve  56  and  52  are still in the open position and off their respective seats even though there is no flow through them because of cessation of downhole movement of the casing  24 . The path represented by arrow  94  is now blocked by the cone  86  resting on spider  78 . 
     Referring now to FIGS. 3 a-d , a ball  100  lands in the seat  102  to allow downward shifting of the sliding sleeve  12  so as to close the port  16 . Further pressure build up drives the ball  100  past the seat  102 . The downward movement of ball  100  can be followed by comparing FIGS. 3 a-d . Ultimately, the ball  100  lands in a seat  104  shown in FIG. 3 d  as part of the float sleeve  84 . At this time the casing  24  is essentially sealed internally. Application of pressure on ball  100  drives the float sleeve  84  downwardly until its flange  96  contacts lock ring  76  which drives lock ring  76  downwardly and unlocks rod  60  for uphole movement because the collets  74  can move outwardly with ring  76  displaced. When rod  60  is able to move upwardly, the springs  54  and  62  expand as check valves  52  and  56  move to their closed positions shown in FIG. 3 d . The assembly shown in FIGS. 3 a-d  is now ready for cementing. 
     It should be noted that with ball  100  on seat  104  as shown in FIG. 3 d , before pins  90  are sheared, additional equipment can be provided to the assembly shown in FIGS. 3 a-d  and actuated by pressure. For example, a pressure to set hydraulic hanger can be applied to the casing  24  to hang it. The shear pin  90 , which is shown in FIG. 3 d  in the broken position, can be sized appropriately to allow multiple levels of pressure build up to operate additional auxiliary pressure actuated equipment. One such item is a hydraulic hanger which can be mounted below the running tool  20 . Additionally, a higher level of pressure build up can be used to release the collets  26  from groove  28  for a release of running tool  20  as shown in FIG. 3 b.    
     Those skilled in the art will appreciate that a redundancy in check valves is provided in the preferred embodiment. However, more or fewer check valves can be provided without departing from the invention. It is important to be able to close off the casing  24  after it is run into position. The redundancy of check valves  52  and  56  ensures that such a closure will take place. 
     Those skilled in the art can now appreciate that the design of the present invention allows for greater cross sectional flow areas while running in the casing  24 . This allows for far greater running rates for the casing and saves rig time. By using the deformable ball seats of known design, the size of the ball  100  can be reduced down to as little as 1.5 inches to prevent problems of access through uphole equipment. Referring to FIG. 1 d , a greater cross sectional flow area is made available by virtue of a combination of ports  80 , slots  90  and a central passage represented by arrow  93  through the float sleeve  84 . Accordingly, for casing size in the order of 9⅝ to 13⅜ inches, an open area of 10 square inches and higher can be achieved through this zone. Similarly, up above where flow areas through sleeves such as  34  normally configured with wiper plug  46  can also present a flow restricting area. The floating design of float sleeve  34  in combination with passages  42  also allows an increase in flow area in this section of the down hole assembly of comparable open area to that shown below in FIG. 1 d . Thus, for example, for standard wall casing of approximately 9⅝ inch diameter, the relative open area of approximately 10 square inches or greater can be compared to the total available internal area in the casing  24  of approximately 59 square inches. Accordingly, open areas of about 10 square inches or 15 percent or greater open area as compared to the prior art bottlenecks which have been in the order of 3 to 4 square inches can be achieved with the design of the present invention. The accompanying increase in speed of running in the assembly can be readily appreciated. 
     Additional flow ports through the cone  86  can be provided, if desired. 
     The reconfiguration of receptacle  40  allows a greater open area in the region of wiper plug  46  by letting flow into the annulus  106  around inner mandrel  30 . 
     The above description of the preferred embodiment is merely illustrative and those skilled in the art will appreciate that modification of the preferred design with regard to number, size, physical placement and movement of the parts can be undertaken without departing from the invention whose scope is fully determined by the claims below.