Patent Publication Number: US-7584801-B2

Title: Drill string flow control valves and methods

Description:
RELATED APPLICATION 
   This application claims priority to provisional application Ser. No. 60/793,883, entitled “Drill String Flow Control Valve” filed on Apr. 21, 2006, the full disclosure of which is hereby incorporated by reference in full. 

   BACKGROUND 
   The present invention generally relates to drill string flow control valves and more particularly, drill string flow control valves for prevention of u-tubing of fluid flow in drill strings and well drilling systems. 
   Managed Pressure Drilling (MPD) and Dual Gradient Drilling are oilfield drilling techniques which are becoming more common and creating a need for equipment and technology to make them practical. These drilling techniques often utilize a higher density of drilling mud inside the drill string and a lower density return mud path on the outside of the drill string. Examples of such dual gradient drilling techniques are disclosed in U.S. Pat. No. 7,093,662. 
   In dual gradient drilling, an undesirable condition called “u-tubing” can result when the mud pumps for a drilling system are stopped. Mud pumps are commonly used to deliver drilling mud into the drill string and to extract return mud from the well bore and a return riser (or risers). In a typical u-tubing scenario, fluid flow inside a drill string may continue to flow, even after the mud pumps have been powered down, until the pressure inside the drill string is balanced with the pressure outside the drill string, e.g. in the well bore and/or a return riser (or risers). This problem is exacerbated in those situations where a heavier density fluid precedes a lighter density fluid in a drill string. In such a scenario, the heavier density fluid, by its own weight, can cause continued flow in the drill string even after the mud pumps have shut off. This u-tubing phenomenon, can result in undesirable well kicks, which can cause damage to a drilling system. For this reason, it is desirable that when mud pumps in a drilling system are turned off, the forward fluid flow be discontinued quickly. 
   SUMMARY 
   The present invention generally relates to drill string flow control valves and more particularly, drill string flow control valves for prevention of u-tubing of fluid flow in drill strings and well drilling systems. 
   Drill string flow control valves of the present invention utilizes the pressure differential between certain pressure ports positioned to apply pressure to a valve sleeve within a valve housing to cause actuation of the valve sleeve, so as to control the operation of the drill string flow control valve. More specifically, drill string flow control valves may comprise a valve housing, a valve sleeve axially movable within a valve housing from a closed position to an open position, a biasing mechanism for biasing the valve sleeve into the closed position, and a plurality of pressure ports for allowing a differential pressure to be exerted on the valve sleeve. A differential pressure exerted on the valve sleeve may be the result of an upstream pressure and a downstream pressure. By allowing a differential pressure resulting from a fluid flow to act on the valve sleeve, u-tubing in a drill string can be prevented or substantially reduced. 
   One example of a drill string flow control valve comprises a valve housing wherein the valve housing has a housing flow path from a housing flow inlet to a housing outlet flow port; a valve sleeve disposed at least partially in the valve housing, the valve sleeve having a sleeve flow port wherein the valve sleeve is axially movable within the valve housing from a closed position to an open position, such that the sleeve flow port substantially impedes fluid flow from the housing outlet flow port to the sleeve flow port when the valve sleeve is in the closed position and wherein the sleeve flow port allows fluid flow from the housing outlet flow port to the sleeve flow port when in the open position; wherein the valve sleeve has an upper pressure surface defined thereon so as to provide a partial cross-sectional surface area upon which a first fluid pressure may act to provide a downward force on the valve sleeve and wherein the valve sleeve has a lower pressure surface defined thereon so as to provide a partial cross-sectional surface area upon which a second fluid pressure may act to provide an upward force on the valve sleeve; a spring wherein the spring biases the valve sleeve to the closed position by exertion of a biasing force on the valve sleeve; an upper pressure port that allows the first fluid pressure to act upon the upper pressure surface from the housing flow path; and a lower pressure port that allows the second fluid pressure to act upon the lower pressure surface from external the valve housing. 
   Another example of a drill string flow control valve comprises a valve housing wherein the valve housing has a housing flow path from a housing flow inlet to a housing outlet flow port; a valve sleeve disposed at least partially in the valve housing, the valve sleeve having a sleeve flow port wherein the valve sleeve is axially movable within the valve housing from a closed position to an open position, such that the sleeve flow port substantially impedes fluid flow from the housing outlet flow port to the sleeve flow port when the valve sleeve is in the closed position and wherein the sleeve flow port allows fluid flow from the housing outlet flow port to the sleeve flow port when in the open position; wherein the valve sleeve has an upper pressure surface defined thereon so as to provide a partial cross-sectional surface area upon which a first fluid pressure may act to provide a downward force on the valve sleeve and wherein the valve sleeve has a lower pressure surface defined thereon so as to provide a partial cross-sectional surface area upon which a second fluid pressure may act to provide an upward force on the valve sleeve; a biasing mechanism wherein the biasing mechanism biases the valve sleeve to the closed position; an upper pressure port that allows the first fluid pressure to act upon the upper pressure surface from the housing flow path; and a lower pressure port that allows the second fluid pressure to act upon the lower pressure surface from external the valve housing. 
   An example of a method for preventing u-tubing in a drill string comprises providing a valve housing wherein the valve housing has a housing flow path from a housing flow inlet to a housing outlet flow port; providing a valve sleeve disposed at least partially in the valve housing, the valve sleeve having a sleeve flow port wherein the valve sleeve is axially movable within the valve housing from a closed position to an open position, such that the sleeve flow port substantially impedes fluid flow from the housing outlet flow port to the sleeve flow port when the valve sleeve is in the closed position and wherein the sleeve flow port allows fluid flow from the housing outlet flow port to the sleeve flow port when in the open position wherein the valve sleeve has an upper pressure surface defined thereon so as to provide a partial cross-sectional surface area upon which a first fluid pressure may act to provide a downward force on the valve sleeve and wherein the valve sleeve has a lower pressure surface defined thereon so as to provide a partial cross-sectional surface area upon which a second fluid pressure may act to provide an upward force on the valve sleeve; providing a biasing mechanism wherein the biasing mechanism biases the valve sleeve to the closed position by exerting a biasing spring force on the valve sleeve; providing an upper pressure port that allows the first fluid pressure to act upon the upper pressure surface from the housing flow path with an upper force; providing a lower pressure port that allows the second fluid pressure to act upon the lower pressure surface from external the valve housing with a lower force; increasing a fluid pressure upon the valve sleeve so as to cause the valve sleeve to shift from the closed position to the open position; maintaining a fluid flow through the valve sleeve so that the upper force is greater than the biasing spring force plus the lower force; and decreasing the fluid flow through the valve sleeve so as to allow the biasing mechanism to shift the valve sleeve from the open position to the closed position. 
   An example of a drill string flow control valve system comprises a valve housing wherein the valve housing has a housing flow path from a housing flow inlet to a housing outlet flow port; a valve sleeve disposed at least partially in the valve housing, the valve sleeve having a sleeve flow port wherein the valve sleeve is axially movable within the valve housing from a closed position to an open position, such that the sleeve flow port substantially impedes fluid flow from the housing outlet flow port to the sleeve flow port when the valve sleeve is in the closed position and wherein the sleeve flow port allows fluid flow from the housing outlet flow port to the sleeve flow port when in the open position; wherein the valve sleeve has an upper pressure surface defined thereon so as to provide a partial cross-sectional surface area upon which a first fluid pressure may act to provide a downward force on the valve sleeve and wherein the valve sleeve has a lower pressure surface defined thereon so as to provide a partial cross-sectional surface area upon which a second fluid pressure may act to provide an upward force on the valve sleeve; a biasing mechanism wherein the spring biases the valve sleeve to the closed position by exertion of a biasing force on the valve sleeve; a flow restriction in fluid communication with the valve sleeve; an upper pressure port that allows the first fluid pressure to act upon the upper pressure surface from the housing flow path wherein the first fluid pressure is measured upstream of the flow restriction; and a lower pressure port that allows the second fluid pressure to act upon the lower pressure surface from external the valve housing wherein the second fluid pressure is measured downstream of the flow restriction. 
   Yet another example of a drill string flow control valve system comprises a valve housing having an external surface and a first flow path therein; a valve sleeve slidingly mounted in the valve housing; a biasing mechanism for biasing the valve sleeve in a closed position; a first pressure port acting on a first portion of the sleeve and in fluid communication with the first flow path; and a second pressure port acting on a second portion of the sleeve and in fluid communication with a second flow path. 
   The features and advantages of the present invention will be apparent to those skilled in the art. While numerous changes may be made by those skilled in the art, such changes are within the spirit of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete understanding of the present disclosure and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying figures, wherein: 
       FIG. 1  illustrates a cross-sectional view of a drill string flow control valve. 
       FIG. 2  illustrates a cross-sectional view of a drill string flow control valve shown in a closed position and an open position. 
       FIG. 3  illustrates a cross-sectional view of a drill string flow control valve shown in a closed position and an open position with flow arrows showing a fluid flow path. 
       FIG. 4  illustrates a cross-sectional view of a drill string flow control valve having an internal jet. 
       FIG. 5  illustrates several components of one embodiment of a drill string flow control valve shown apart in a disassembled manner. 
   

   While the present invention is susceptible to various modifications and alternative forms, specific exemplary embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
   DESCRIPTION OF PREFERRED EMBODIMENTS 
   The present invention generally relates to drill string flow control valves and more particularly, drill string flow control valves for prevention of u-tubing of fluid flow in drill strings and well drilling systems. 
   Drill string flow control valves are provided herein that, among other functions, can be used to reduce and/or prevent u-tubing effects in drill strings. 
   To facilitate a better understanding of the present invention, the following examples of certain embodiments are given. In no way should the following examples be read to limit, or define, the scope of the invention. 
   For ease of reference, the terms “upper,” “lower,” “upward,” and “downward” are used herein to refer to the spatial relationship of certain components. The terms “upper” and “upward” refer to components towards the surface (distal to the drill bit), whereas the terms “lower” and “downward” refer to components towards the drill bit (or proximal to the drill bit), regardless of the actual orientation or deviation of the wellbore or wellbores being drilled. The term “axial” refers to a direction substantially parallel to the drill string in proximity to a drill string flow control valve. 
     FIG. 1  illustrates a cross-sectional view of a drill string flow control valve in accordance with one embodiment of the present invention. Drill string flow control valve  100  is shown inline in a drill string, connected at drill pipe threads  4  to upper sub  1  and lower sub  3 . Drill string flow control valve  100  may be installed in the drill string at any point in the drill string above the drill bit. One or more components such as drill pipe joints/sections, MWD components, heavy-walled drill pipe, or any number BHA components may be installed between drill string flow control valve  100  and the drill bit. Drill string flow control valve  100  is generally comprised of a valve housing  2  and a valve sleeve  2  slidingly mounted therein. Drill string control  100  may also include ported plug  5  to direct fluid flow within valve housing  2 . Although valve housing  2  and ported plug  5  are shown here as two or more components, in certain embodiments, these two components may be formed as one integral piece. Valve sleeve  12  is disposed in valve housing  2  and is axially slidable or movable within valve housing  2 , and more particularly, in this embodiment, partially disposed within a portion of ported plug  5 . 
   Valve sleeve  12  is biased upwards by spring  15 . Housing inlet flow port  7 , flow path  8 , and housing outlet flow port  10  together compose housing flow path  7 ,  8 , and  10 , through which fluid may flow by entering valve housing  2  from upper sub  1 , entering inlet flow port  7 , flowing through flow path  8 , and then flowing through housing outlet flow port  10 . In  FIG. 1 , sleeve flow port  9  of valve sleeve  12  is not aligned with housing outlet flow port  10 . Therefore, in the configuration shown here, fluid cannot flow from housing outlet flow port  10  through sleeve flow port  9 , because valve sleeve  12  is blocking the fluid flow path (i.e. the closed position of drill string flow control valve  100 ). As will be explained herein, valve sleeve  12  is capable of sliding downward so that housing outlet flow port  10  may align with sleeve flow port  9  to allow fluid to flow through drill string flow control valve  100  (i.e. the open position). 
   Upper pressure port  11  allows fluid pressure PI to be communicated from housing flow path  7 ,  8 , and  10  to upper pressure surface  18 . In certain embodiments, upper pressure surface  18  may be a protrusion, extension, and/or cross-sectional surface area of valve sleeve  12  upon which a fluid pressure may act so as to provide a downward acting axial force on valve sleeve  12 . In another embodiment, upper pressure surface  18  may be defined as the top of valve sleeve  12 . In any event, as fluid pressure PI increases on upper pressure surface  18 , valve sleeve is motivated downward by fluid pressure PI acting against the upward bias force of spring  15 . Thus, a sufficient fluid pressure acting upon upper pressure surface  18  induces valve sleeve  12  to slide downward. Given sufficient downward force on valve sleeve  12 , sleeve flow port  9  will be aligned with housing outlet flow port  10  so as to allow fluid flow to pass through drill string flow control valve  100 . 
   Consequently, fluid flow is thus permitted to pass through drill string flow control valve  100 . The fluid flow eventually passes through a drill bit (not shown) and out and upward into the annulus of the well bore to return the drilling mud to the surface. During normal or high flow conditions, a typical drilling mud flow rate will result in a marked pressure drop across the drill bit as the fluid passes through the drill jets of the drill bit. Thus, at any given level of the drill string, the fluid pressure P 4  measured in the annulus will be lower than the fluid pressure P 2  inside drill string flow control valve  100  on account of the pressure drop that results from the fluid flowing from inside the drill string to the outer annulus. This pressure drop characterized by P 2 -P 4  is usually attributable in large part to the pressure drop experienced across the drill jets of the drill bit. 
   Lower pressure port  14  allows the fluid pressure P 4  in the annulus to be communicated to lower pressure surface  19 . Lower pressure surface  19  may be a protrusion, extension, and/or cross-sectional surface area of valve sleeve  12  upon which a fluid pressure may act so as to provide an upward acting axial force on valve sleeve  12 . Likewise, lower pressure surface  19  may also be defined as the bottom of valve sleeve  12 . In the illustrated embodiment, upper pressure surface  18  and lower pressure surface  19  are defined on the same protrusion. In any event, the fluid pressure P 4  in the annulus is allowed to provide an upward force on valve sleeve  12  by acting upon lower pressure surface  19 . In this way, both the biasing force of spring  15  and the fluid pressure P 4  of the annulus counteract the downward force provided by fluid pressure P 1  on upper pressure surface  18 . During normal flow conditions, drill string flow control valve  100  is designed so that the fluid flow through drill string flow control valve  100  and the drill bit will result in a pressure drop P 1 -P 4  such that the pressure drop P 1 -P 4  will provide a differential pressure acting upon valve sleeve  12  (via upper pressure surface  18  and lower pressure surface  19 ) sufficient to keep valve sleeve  12  in the open or substantially open position. 
   Once the fluid pumps delivering drilling mud to the drill string are shut down and fluid flow decreases, the pressure differential P 1 -P 4  will quickly drop significantly. Pressure differential P 1 -P 4  will no longer be a sufficient to overcome the biasing force of spring  15  and accordingly, valve sleeve will be motivated upwards to its closed position thus impeding or substantially impeding fluid flow through drill string flow control valve  100 . 
   Adjustment shims  17  are provided to adjust the compression of spring  15 . By altering the compression of spring  15 , the biasing force of spring  15  may be adjusted for different operating conditions of drill string flow control valve  100 . Operating conditions to which drill string flow control valve  100  is subjected include, but are not limited to, desired flow rates, fluid densities, depth of drill string flow control valve  100 , and expected pressure differentials through the drill bit. Design variables of drill string flow control valve  100  that may be adjusted include, but are not limited to, inner and outer diameters of drill string flow control valve  100 , the spring constant (e.g. by changing the wire length, wire diameter, wire material, wire angle, wire pitch, etc.), the size of the flow ports, and the pressure drop through drill string flow control valve  100 . 
   Optional seals S 1 , S 2 , S 3 , and S 4  are provided at the indicated locations to prevent leakage of fluid and to prevent communication of fluid pressures to undesired sites around valve sleeve  12 . 
   Although upper pressure surface  18  and lower pressure surface  19  are depicted here as one integral piece, it is explicitly recognized that both surfaces may be composed of separate extensions protruding from valve sleeve  12 . 
     FIG. 2  illustrates a cross-sectional view of a drill string flow control valve shown in both a closed position and an open position. More specifically, drill string flow control valve  200 A is shown in the closed position, and drill string flow control valve  200 B is shown in the open position. 
   Drill string flow control valve  200 A is shown inline a drill string as attached to upper sub  1  and lower sub  3 . Here, valve sleeve  12  is biased in an upward or closed position by spring  15  and consequently, housing outlet flow port  10  and sleeve flow port  9  are out of alignment. Drill string flow control valve  200 B, however, is shown in the open position as valve sleeve  12  is biased downward against compressed spring  12  and consequently, housing outlet flow port  10  and sleeve flow port  9  are in substantially alignment. 
     FIG. 3  illustrates a cross-sectional view of a drill string flow control valve shown in a closed position and an open position. The flow arrows indicated in drill string flow control valve  300 B indicate the normal fluid flow path when drill string flow control valve  300 B is in the open position. 
     FIG. 4  illustrates a cross-sectional view of a drill string flow control valve having internal jet  20 . The embodiment depicted in  FIG. 4  is similar to the embodiment of  FIG. 1  with the exception of the addition of jet  20  and a modification of the placement of lower pressure port  14 . In this embodiment of  FIG. 4 , fluid flow through valve sleeve  12  is guided through jet  20 . Jet  20  may be any device suitable for producing a measurable pressure drop. Thus, fluid flow passing through jet  20  will experience a pressure drop as the fluid passes through jet  20  such that pressure P 2  will be lower than pressure P 1 . Indeed, under most circumstances, the pressure drop P 1 -P 2  will vary proportional to the fluid flow except under certain choked flow conditions. Lower pressure port  14  allows pressure P 2  to be communicated to lower pressure surface  19  to provide an upward force on valve sleeve  12 . As before in  FIG. 1 , upper pressure port  11  allows pressure P 1  to be communicated to upper pressure surface  18  to provide a downward force on valve sleeve  12 . In this way, pressure differential P 1 -P 2  acts on valve sleeve  12  to provide a net biasing force on valve sleeve  12  to counteract the biasing force of spring  15 . 
   As before in  FIG. 1 , as fluid flow rate through valve sleeve  12  increases, the net biasing force acting on valve sleeve  12  motivates the sleeve towards the open position. A decrease in fluid flow, on the other hand, motivates valve sleeve  12  towards the closed position. One of the advantages of the embodiment of  FIG. 4  is the benefit that only clean fluid enters the region of spring  15  between valve sleeve  12  and outer valve housing  2 . In the embodiment of  FIG. 1 , however, drilling mud from the annulus enters the region of spring  15  between valve sleeve  12  and outer valve housing  2 . The drilling mud from the annulus may contain additional drill bit cuttings and debris from the formation, which may cause fouling problems in the region of spring  15 . 
   Here, upper pressure surface  18  and lower pressure surface  19  are depicted as one extension from valve sleeve  12  such that both surfaces or cross-sectional surface areas are formed integrally from one piece or extension of valve sleeve  12 . In certain embodiments, however, an upper pressure surface and a lower pressure surface may be formed by separate extensions apart from one another as desired. In such a scenario, it is recognized that an upper pressure surface and lower pressure surface may provide surface areas of different cross-sectional areas. Thus, in this alternative embodiment, pressure PI would act upon a surface area of an upper pressure surface of a first cross-sectional area whereas pressure P 3  would act upon a surface area of a lower pressure surface of a second cross-sectional area. 
   Additionally, although spring  15  is depicted here as acting upon lower pressure surface  19 , it is explicitly recognized that spring  15  may act upon any extension of valve sleeve  15  or alternatively, may attach to valve sleeve  15  by any means known in the art, including any known attachment or bonding method known in the art. Thus, in certain embodiments of drill string flow control valve  400 , pressure P 1  could act upon an upper pressure surface that is distinct and apart from a lower pressure surface upon which pressure P 3  acts. Spring  15  may act upon either the upper pressure surface or the lower pressure surface or upon an entirely different pressure surface of valve sleeve  12 , or by any attachment of spring  15  to valve sleeve  12  that would allow communication of the potential energy of spring  15  to valve sleeve  12 , or any combination thereof. In other embodiments, spring  15  may be disposed to act on another portion of sleeve  12  so long as spring  15  biases valve sleeve  12  into a “closed” position. 
   The net downward biasing force on valve sleeve  12  may be described by an equation that accounts for the various pressures in the system acting upon the relevant surface areas while taking into account the force exerted by the spring. Additionally, it is clear that the characteristics of the system will also be influenced by the hydrostatic pressure resulting from the depth of the drill string flow control valve and the relevant fluid densities used. 
   Additionally, in certain embodiments, upper pressure port  11  may communicate any upstream pressure to upper pressure surface  18  while lower pressure port  14  communicates any downstream pressure to lower pressure surface  19 . The term “downstream pressure,” as used herein, refers to any pressure measured downstream a flow restriction that produces a measurable fluid flow pressure drop after the flow restriction. The term “upstream pressure,” as used herein, refers to any pressure measured upstream of the same flow restriction. Examples of suitable flow restrictions include, but are not limited to jets, venturi nozzles, a flow orifices, drill bit jets, any length of piping sufficient to create a measurable pressure drop, or any combination thereof. Further, it is recognized that the communication of pressures from one location to another in the systems described herein may be accomplished with a plurality of ports even though only one port may be described in certain embodiments. 
     FIG. 5  illustrates several components of one embodiment of a drill string flow control valve shown apart in a disassembled manner. For clarity, several of the components of one embodiment of a drill string flow control valve are shown apart in a disassembled view in  FIG. 5 . The components, shown apart here, include valve housing  2 , ported plug  5 , lower sub  3 , valve sleeve  12 , spring  15 , and shim sleeve  16 . 
   Although drill pipe threads have been depicted herein in several embodiments, it is explicitly recognized that the drill string flow control valves, the joints of drill pipe, and other drill string components herein may be attached to one another by any suitable means known in the art including, but not limited to, drill pipe threads, ACME threads, high-torque shoulder-to-shoulder threads, o-ring seals, welding, or any combination thereof. 
   While the foregoing has been described in relation to a drill string and is particularly desirable for addressing u-tubing concerns, those skilled in the art with the benefit of this disclosure will appreciate that the drill string flow control valves of the present invention can be used in other fluid flow applications without limiting the foregoing invention. 
   Therefore, the present invention is well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the present invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the present invention. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee.