Abstract:
The present invention generally provides a system and method for selectively sealing a drill string or other tubular member. In one aspect, a sealing member, such as a valve, allows a certain level of flow of drilling fluids and/or other fluids through one or more flow channels when the valve is open. To close the valve, the flow rate is increased so that a backpressure develops and urges the valve to a closed position. The valve can remain in position in the drill string and alternately open and close depending on the flow rate and/or the pressure drop through the valve. The valve also comprises a removable plug disposed in the valve to provide access with, for example, wireline tools to a region below the valve in a wellbore.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to oil field tools. More specifically, the invention relates to an apparatus for and a method of using a sealing member, such as a valve, disposed in a wellbore. 
     2. Background of the Related Art 
     Oil field wells are drilled typically using a tubular drill string attached to a drill bit to a subterranean producing zone to form a wellbore. Drilling fluid is flowed downhole through the interior of the drill string, through ports, for example, in a drill bit (not shown) to wash away debris at the cutting surfaces, and then upward through an annulus formed between the drill string and a tubular casing that lines the wellbore. The casing is perforated to allow production fluid to flow into the casing and up to the surface of the well, and the drill string is removed from the wellbore. 
     During drilling, regions of the wellbore are sometimes sealed from other regions. For example, various oilfield equipment, such as motion compensators, periodically need resetting or adjusting in the wellbore. The drill string is plugged and the drilling fluid is raised to a given pressure to actuate or reset the equipment. In other instances, control of the well can be lost due to excessive pressure through the wellbore from subterranean zones. The drill string can become damaged and require repair. The drill string may need temporary plugging below the damage. In other instances, the drill pipe can be temporarily plugged to restrain any flow of production fluid through the drill pipe while zones in the drill string above the plug are tested. 
     A typical apparatus used to seal between two regions of the drill string is known as a bridge plug and typically includes slip elements and packer elements. The slip elements are used to grip the inside surface of the drill string or other surfaces, thereby preventing the bridge plug from moving up or down in the drill string. The packer elements engage the inside surface of the drill string or the wellbore to provide the requisite seal. The drilling must be stopped to set the retrievable bridge plug, portions of the drilling operation are disassembled, and wireline tools and a bridge plug are inserted into the drill string to an appropriate depth to provide a seal between two zones in the drill string. One type of bridge plug is a permanent bridge plug that can be set in place against a surface, such as an inside surface of a drill string. However, the bridge plug typically is removed by drilling or milling through the plug, which can be costly and time consuming. Another type of plug is a retrievable bridge plug, which typically uses hydraulic fluid to selectively actuate the slip elements and packer elements. The retrievable bridge plug can be removed by releasing pressure on the elements and pulling the bridge plug from the wellbore. Either type of bridge plug needs subsequent removal to provide fluid flow to lower regions or for access with downhole tools. The removal can involve several steps and can be expensive and time consuming. It would be advantageous to be able to be repetitively seal the wellbore or other passageway with an apparatus without necessitating having to drill or mill through the apparatus or to pull the apparatus for removal. 
     There remains a need for an improved system and method for sealing a drill string that can remain in the wellbore for subsequent use. 
     SUMMARY OF THE INVENTION 
     The present invention generally provides a system and method for selectively sealing a drill string or other tubular member. In one aspect, a sealing member, such as a valve, allows a certain level of flow of drilling fluids and/or other fluids through one or more flow channels when the valve is open. To close the valve, the flow rate is increased so that a backpressure develops and urges the valve to a closed position. The valve can remain in position in the drill string and alternately open and close depending on the flow rate and/or the pressure drop through the valve. The valve also comprises a removable plug disposed in the valve to provide access with, for example, wireline tools to a region below the valve in a wellbore. 
     In one aspect, a system for sealing a wellbore comprises one or more such as tubular members, such as drill pipe, one or more flow actuated shut-off valves coupled to the one or more tubular members, at least one source of fluid coupled to the one or more tubular members, and at least one pressure source coupled to the source of fluid. In another aspect, a flow actuated shut off valve comprises a body, a piston disposed in the body, one or more channels disposed through the piston having an inlet to the piston and an outlet from the piston, and a bias member coupled to the piston. In another aspect, a method of closing an oilfield valve comprises flowing a first fluid through a valve at a first flow rate, flowing the first fluid through the valve at a higher second flow rate, at least partially closing the valve with a force exerted by the second flow rate. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     So that the manner in which the above recited features, advantages and objects of the present invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings. 
     It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
     FIG. 1 is a schematic cross sectional view of a valve according to the present invention interposed in a drill string in a wellbore. 
     FIG. 2 is a schematic longitudinal cross sectional view of one embodiment of a valve. 
     FIG. 3 is a schematic transverse cross sectional view of the valve shown in FIG.  2 . 
     FIG. 4 is a schematic transverse cross sectional view of the plug shown in FIG.  2 . 
     FIG. 5 is a schematic longitudinal cross sectional view of another embodiment of a valve. 
     FIG. 6 is a schematic transverse cross sectional view of the valve shown in FIG.  5 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 is a schematic cross sectional view of an exemplary sealing member, or a valve  16 . The valve  16  is disposed in a drill string  14  in a wellbore  10  that is shown in a vertical orientation. However, other orientations, such as a lateral orientation, are included within the scope of the invention. A casing  12  lines the wellbore  10  and the drill string  14  is disposed therein. The drill string  14  is used to provide rotational output to a tool, such as a drill or mill, and to provide translational movement of tools within the wellbore  10 . A valve  16  is threadably inserted between joints  20 ,  22  of the drill string  14 . 
     FIG. 2 is a schematic longitudinal cross sectional view of one embodiment of a valve  50  in an open (right half of the figure) position and a closed (left half of the figure) position. In general, the valve  50  includes an outer body  51  having an upper portion  52  of the body and a lower portion  56  of the body, a piston  62  slidably disposed in a cavity  53  formed between the upper portion and lower portion, and a replaceable plug  90  disposed in the piston. The upper portion  52  of the body includes one end with standard API female threads  54  and the lower portion  56  of the body includes one end with standard API male threads  58  to mate with the corresponding joints of the drill string on each end. The upper portion  52  of the body and lower portion  56  of the body are joined together at a threaded joint  60  and define an inner cavity  53 . The inner cavity includes an annular recess  64  defined between a shoulder  68  in the upper portion  52  of the body and an upper end  74  of the lower portion  56  of the body. The lower portion  56  of the body includes an annular seat  84  having a tapered surface  86 . The seat defines a channel  85  through which fluids pass through the valve to other portions of the drill string. The seat  84  is coupled to the lower portion  56  of the body by one or more connectors  88 , such as a pin or a bolt. Alternatively, the seat can be formed integral with the lower portion  56  of the body. 
     The piston  62  is preferably a cylindrical member having an annular flange  72  that is slidably disposed in the recess  64 . The piston also includes a plurality of longitudinal channels  76  that are disposed therethrough. The channels have a first end  78  that preferably is an inlet for fluid flowing through the drill string and a second end  80  that preferably is an outlet for the fluid. The size, quantity and shape of the channels  76  can be chosen to allow a certain amount of fluid flow while achieving a certain amount of pressure drop. The surface of the piston adjacent the second end  80  of the channels is preferably tapered between the outer perimeter and an annular protrusion  82  that forms a sealing surface on the piston that engages the seat  84  of the lower portion  56  of the body. The piston  62  also includes an inner channel  91  disposed through the piston and generally aligned with the longitudinal axis of the valve for receipt of the removable plug  90 . An inner annular recess  100  is formed in a lower end of the inner channel  91  of the piston  62  to assist in securing the removable plug in the piston. A seal  66 , such as an O-ring, is disposed between the outer perimeter of the piston  62  and the inner perimeter of the upper portion  52  of the body. 
     The removable plug  90  preferably includes a cylindrical body member having a first end  94  shaped to engage a typical wireline fishing tool (not shown) for retrieval and placement in the piston  62 . A second end  96  of the plug  90  has one or more flexible fingers  98  that can engage an annular recess  100  in the piston  62 . The fingers include one or more locking members  99  that may be integral to the fingers and have tapered surfaces, as shown, or may be separate members, such as a C-ring or O-ring, that is coupled to the fingers to engage the corresponding annular recess  100  in the piston and retain the plug with the piston until removal. A counterbore  102  is defined between the fingers to allow the fingers to flex inwardly as the plug is inserted or removed and reinserted into the piston  62 . Preferably, the locking members  99  are tapered at surfaces  104 ,  106  to correspond to the tapered surfaces of the recess  100  of the piston  62 . This configuration allows to allow easy removal and placement of the plug into the piston. 
     A bias member  70  is disposed in the recess  64  around the piston  62 . The bias member can be a spring, such as a coil spring, an elastomeric member, a solenoid operated piston, or other biasing member which could apply a longitudinal force to the piston. The bias member  70  engages the piston  62  at the annular flange  72  on one end and engages an end  74  of the lower portion  56  of the body on the other end. The bias member  70  biases the piston  72  in an open position toward the shoulder  68  of the recess  64 . 
     FIG. 3 is a transverse cross sectional view of the valve  50  along line  3 — 3  in FIG.  2 . The piston  62  is disposed in the cavity  53  within the upper portion  52  of the body and lower portion of the body (not shown) and the plug  90  is disposed in the piston. The annular flange  72  is disposed in the recess  64 . The bias member  70  circumferentially engages the annular flange  72 . The seal  66  is disposed between the piston  62  and the perimeter of the upper portion  52  of the body. Twelve channels  76  are disposed around the piston  62 , although the size, quantity and shape can vary, depending on the desired operating conditions of the valve. 
     FIG. 4 is a transverse cross sectional view of the plug  90  on the distal end illustrating the fingers  98 . Preferably, a plurality of fingers  98  are disposed circumferentially about the perimeter of the plug. The fingers are sized and adapted to flex as the plug is removed and reinserted into the piston  62  (shown in FIG.  2 ). The fingers  98  define a space  108  therebetween to enable independent flexing of the fingers. 
     In operation, the valve is open at selected flow rates. The drilling fluid passes through the channels  76 , past a seat  84 , and through an channel  85  down to, for example, a drilling bit to wash debris away from the bit and up an annulus  24  between the drill string  14  and the casing  12  (shown in FIG.  1 ). The fluid flow rate creates a pressure drop from the first end  78  of the channels  76  to the second end  80  of the channels and results in a force that attempts to urge the piston  62  downward toward the seat  84 . However, the bias member  70  exerts a counterforce that maintains the piston  62  in an upward position. To close the valve, the fluid flow rate is increased to a level that results in a greater force than the bias member  70  exerts on the piston  62  and the valve begins to close. As merely one example, for a 7.5 inch outside diameter valve, the channels  76  can be sized to create a closing pressure drop of about 140 pounds per square inch (“psi”) with a flow rate of 700 gallons per minute (“gpm”) with 16.0 pounds per gallon (lb./gal.) drilling fluid (“mud weight”). It is believed that the same channels would produce about a 140 psi pressure drop with a flow rate of about 925 gpm with 9.0 lb./gal. mud weight. The bias member  70  can be changed to another bias member, the distance between the flange  72  and the end  74  of the lower portion can be altered or other adjustments made to vary the force required to close the valve. The piston moves longitudinally down in the annular recess  64  with the increased force exerted by the fluid and the annular protrusion  82  seals against the seat  84  to stop the flow. Continued flow into the drill string  14  increases the pressure in the drill string above the valve  50  for testing or other purposes. Releasing or reducing the pressure allows the valve to reset to an open position when the bias member  70  pushes the piston  62  back up in the cavity  53  and fluid flow through the valve can be continued. The valve can be open and closed repetitively in like manner. 
     To gain access through the valve  50 , the plug  90  can be removed with conventional wireline tools by engaging the first end  94  of the plug  90 . The fingers  98  flex inward as the plug  90  is pulled away from the piston and disengage the recess  100  to slide out of the inner channel  91  of the piston  62 . The plug can be reinserted in like manner. 
     FIG. 5 is a schematic longitudinal cross sectional view of another embodiment of a valve in an open (right half of the figure) position and a closed (left half of the figure) position. Elements similar to the embodiment shown in FIGS.  2 — 4  are similarly numbered. A valve  50  has a body  51  with an upper portion  52  of the body and a lower portion  56  of the body that are coupled together and define a cavity  53  therebetween. In general, valve members disposed in the cavity  53  include a piston  62  having an annular flange  110 , a sealing block  116  adjacent the lower portion  56  of the body, a bias member  70  disposed between the flange  110  and the sealing block  116 , a floating piston  122  disposed on the opposite side of the flange  110  from the bias member  70 , and a replaceable plug disposed in the piston  62 . The cavity  53  includes a recess  64  defined between a shoulder  69  and an upper end of the lower portion  56  of the body. The recess  64  may include one or more shoulders along the length of the recess, such as shoulder  137 , that can limit the travel of various members slidably disposed in the cavity  53 . Ports  130 ,  132  are formed through the side wall of the upper portion  52  of the body and are plugged as described below. Port  128  is also formed through the side wall of the upper portion  52  of the body and can remain fluidly coupled between the cavity  53  and a region external to the upper portion  52  of the body. The lower portion  56  of the body includes an annular seat  84 . 
     The piston  62  includes one or more channels  76  formed therethrough. An annular protrusion  82  on the end of the piston  62  is disposed adjacent the seat  84  on the lower portion  56  of the body. The piston  62  includes an annular flange  110  that is slidably disposed in the annular recess  64 . A seal  112  is disposed between the outer perimeter of the flange  110  and the perimeter of the cavity  53  to slidably seal the flange  110  in the cavity  53 . The flange  110  defines at least one channel  114  and at least one channel  142 . A pressure relief valve  134  is mounted in the channel  114  and a check valve  144  is mounted in the channel  142 . The pressure relief valve is oriented to relieve pressure from below the flange  110  and the check valve is oriented to allow fluid flow from above the flange to below the flange. 
     An annular sealing block  116  is disposed below the annular flange  110  and above the lower portion  52  of the body. A seal  118  is disposed along an inner perimeter of the block  116  and seals the inner perimeter with the piston. A seal  120  is disposed along an outer perimeter of the block  116  and seals the outer perimeter with the recess  64 . The bias member  70  engages the flange  110  on one end of the bias member and the sealing block  116  on the other end. The floating piston  122  is disposed in an upper portion of the recess  66  above the annular flange  132 . A seal  124  is disposed between the inner perimeter of the floating piston  122  and the piston  62 . A seal  126  is disposed between the outer perimeter of the floating piston  122  and the recess  64 . The annular flange  110 , sealing block  116 , perimeter of the cavity  53  and outer perimeter of the piston  62  define a first region  136  of the recess  64 . The annular flange  110 , floating piston  122 , perimeter of the cavity  53  and outer perimeter of the piston  62  define an second region  138  of the recess  64 . The floating piston  122 , shoulder  69 , perimeter of the cavity  53  and outer perimeter of the piston  62  define a third region  140  of the recess  64 . The port  130 , formed through the side wall of the upper portion  52  of the body below the flange  110 , is fluidly coupled to the first region  136 . The port  132 , formed through the side wall of the upper portion  52  of the body above the flange  110 , is fluidly coupled to the second region  138 . The third port  128 , formed through the side wall of the upper portion  52  of the body above the floating piston  122 , is fluidly coupled to the third region  140 . Preferably, the first region  136  and second region  138  are filled with fluid, such as hydraulic fluid and the ports  132 ,  134  are sealed. 
     A plug  90  is sealably disposed at least partially within the piston  62 . The plug  90  has a first end  94  preferably shaped to engage a conventional wireline tool to effect removal and placement of the plug. A second end  96  of the plug  90  has one or more fingers  98  with one or more locking members that engage an annular recess  100  in the piston  62 . 
     FIG. 6 is a transverse cross sectional view of the valve  50  along line  6 — 6  in FIG.  5 . The piston  62  is disposed between the walls of the upper portion  52  and the plug  90  is disposed in the piston. The plug  90  is coupled to the piston  62  with fingers  98  disposed against an inner perimeter of the piston. A plurality of channels  76  are formed through the length of the piston  62  and allow fluid to flow through the valve  50 . An annular flange  110  of the piston  62  is sealably and slidably engaged with an inner perimeter of the upper portion  52  of the body. A bias member (not shown), such as a coil spring, engages the flange  110  to bias the piston. One or more pressure relief valves  134  are disposed in the channels  114  in the piston  62 , such as in the flange  110 . One or more check valves  144  are disposed in the channels  142  in the piston  62 . 
     In operation, drilling fluid is flowed through the channels  76  downhole to a drilling bit, mill, or other tool to wash the debris out and up through an annulus  24  between the drill string  14  and the casing  12 , shown in FIG. 1 when the valve is open. The fluid flow rate through the valve creates a pressure drop from the first end  78  of the channels  76  to the second end  80  of the channels and results in a force that attempts to press the piston  62  downward toward the seat  84 . However, fluid sealably disposed in the first region  136  prevents the piston  62  from moving downward. Also, the bias member  70  exerts a counterforce that assists in maintaining the piston  62  in an upward position. 
     To close the valve  50 , the fluid flow rate through the channels  76  is increased to exert a greater force on the piston  62 , which attempts to compress the fluid in the first region  136 . The relief valve opens when a set relief pressure on the pressure relief valve  134  is exceeded, and the fluid in the first region  136  flows through the pressure relief valve  134  and into the second region  138 . The bias member  70  is compressed by the greater force from the increased flow rate of the fluid flowing through the channels  114  and the valve closes. The annular protrusion  82  on the piston  62  engages and seals against the seat  84 . 
     To open the valve  50  again, the fluid flow rate through the channels  76  is reduced and thus, the force created by the fluid on the piston  62  is reduced. The bias member  70  exerts a greater force on the flange  110  than the counterforce produced by pressure of the reduced fluid flow rate and moves the piston  62  in an upward direction in the recess  64 . The pressure relief valve  134  can again close if the pressure is sufficiently low. Fluid in the second region  138  flows one way through the check valve  144  back into the first region  136 . 
     The pressure in the second region  138  is balanced with pressure in the wellbore by drilling fluid or other fluid passing through the port  128  into and out of the third region  140 . The floating piston  122  moves longitudinally in the recess  64  until the wellbore pressure exerted through the port  128  and into the third region  140  is balanced with the fluid pressure in the second region  138 . By balancing the pressure, a more uniform flow rate through the channels  76  before the valve closes can be obtained under varying wellbore pressures and temperatures. The floating piston  122  also allows thermal expansion of the fluid in the second region  138  and/or the first region  136 . 
     The force required to close the valve, and therefore the fluid flow through the channels  76 , can be varied by adjusting several aspects of the valve  50 . For example, the pressure at which the relief valve  134  opens can be adjusted by either substitution of the relief valve or by changing the pressure of an adjustable relief valve. The bias member  70  can be substituted for a different bias member. The bias member can be extended or compressed by, for example, elongating or shortening the recess  64 . Another example of varying the force is elongating or shortening the annular flange on the piston. Each of the described alterations and others can change the force at which the valve closes. Furthermore, the force can be linear or non-linear. For example, a linear force could include a bias member that compresses at a fixed rate of force per unit length. A non-linear force could include a bias member having a variable rate of force per unit length. Different rates could, for instance, allow the valve to throttle the flow in a partially closed position at certain rates of flow. 
     Aspects of the invention have been described in reference to a drill string. The invention is not limited to a drill string, but can be used in various applications related to sealing members with flow-through fluids and piping, particularly in oil field technology. Additionally, references to direction, such as “up”, “down”, “above” and “below”, are for reference to the flow direction and position of elements in the description and claims and are intended to be only exemplary and not limiting, and may be varied depending on the desired direction of flow and the relative locations of the elements. 
     While the foregoing is directed to the preferred embodiment of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.