Patent Publication Number: US-2012031624-A1

Title: Flow tube for use in subsurface valves

Description:
BACKGROUND 
     This section provides background information to facilitate a better understanding of the various aspects of the present invention. It should be understood that the statements in this section of this document are to be read in this light, and not as admissions of prior art. 
     The present disclosure relates generally to wellbore operations and equipment and more specifically to subsurface valves and engaging members (e.g., flow tubes, sleeves) that can be utilized to open and/or close the valve. 
     Equipment is utilized in wells (e.g., wellbore, bore hole) to facilitate the flow of fluids in the well relative to the subterranean formation surrounding the well. Valves are utilized in the well (e.g., subsurface) to inhibit or otherwise control the fluid flow through the well equipment. For example, subsurface safety valves are often disposed in the well to prevent or limit the flow of fluids in an undesired direction. For example, flapper valves are often utilized to enable flow of fluid in a first direction while blocking fluid flow in the opposite second direction. 
     For example, many subsurface safety valves utilize a flapper as a closure mechanism fitted within a body or housing to enable control over fluid flow through a primary longitudinal bore upon an appropriate applied signal (e.g., pressure, flow, electrical or other means) from a control system. The applied signal is commonly a rapid reduction of the hydraulic operating pressure that holds the valve open, thereby facilitating shut-in of the production or injection fluid flow by closure of the valve. The closure mechanism typically is movable between the open and closed position by movement of a tubular device, often called a flow tube. The flow tube can be moved to the open position or operated by the valve actuator which is motivated by hydraulics, pressure, electronic, or other applied signals and power sources. The shifting of the flow tube to a closed position can be performed for example by a mechanical power spring and/or a pressurized accumulator that applies a required load to move the flow tube to the closed position upon interruption of the “opening” signal. As a result, the valve can be required to close against a moving flow stream. Fluid forces acting on the closure member can result in damage to the flow tube and thus to the valve. Further, impacts from the closure member against the end of the flow tube can deform or gall the flow tube leading to failure to operate the valve when needed. 
     SUMMARY 
     According to one or more aspects of the present disclosure, an engaging member for operating a subsurface valve between an open position and a closed position includes a bottom portion comprising a terminal end adapted for contacting a valve closure member, the bottom portion having a first material characteristic; and an upper portion having a second material characteristic that is quantitatively different from the first material characteristic. In some embodiments the material characteristic includes strength and the first material characteristic is greater than the second material characteristic. 
     According to one or more aspects of the present disclosure a subsurface valve configured to move between an open position and a closed position in response to an applied signal includes a housing having a bore; a closure member disposed with the housing; a flow tube movably disposed in the housing, the flow tube comprising a terminal end positioned to contact the closure member, wherein the closure member is actuated to the open position in response to a certain force applied to the flow tube and actuated to the closed position upon relief of the certain applied force; and a bottom portion of the flow tube proximate the terminal end comprising a first material characteristic that is and the second characteristic differ different than a second material characteristic of an upper portion of the flow tube. 
     A method, according to one or more aspects of the present disclosure, for operating a subsurface valve includes disposing a valve in a wellbore, the valve including a housing having a bore, a closure member disposed with the housing, a flow tube movably disposed in the housing, the flow tube comprising a terminal end positioned to contact the closure member and a bottom portion of the flow tube proximate the terminal end having a first material characteristic that is quantitatively different than a second strength characteristic of an upper portion of the flow tube; moving the closure member to an open position in response to a certain force being applied to the flow tube; and moving the closure member to an open position in response to releasing at least a portion of the certain force applied to the flow tube. 
     The foregoing has outlined some of the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of various features may be arbitrarily increased or reduced for clarity of discussion. 
         FIG. 1  is a schematic view of an embodiment of a wellbore completion incorporation a valve and flow tube according to one or more aspects of the present disclosure. 
         FIG. 2  is a partial cross-sectional view of an embodiment of a subsurface valve  12  and flow tube  36  according to one or more aspects of the present disclosure illustrated in the open position. 
         FIG. 3A  is a partial cross-sectional view of another embodiment of a subsurface valve, depicted in the open position, utilizing a flow tube according to one or more aspects of the present disclosure. 
         FIG. 3B  is a partial cross-sectional view of the subsurface valve of  FIG. 3A  depicted in the closed position. 
         FIG. 4  is a cross-sectional view of a section of a flow tube according to one or more aspects of the present disclosure. 
         FIG. 5  is a cross-sectional view of a section of another embodiment of a flow tube according to one or more aspects of the present disclosure. 
         FIG. 6  is a cross-sectional view of a section of another embodiment of a flow tube according to one or more aspects of the present disclosure. 
         FIG. 7  is a cross-sectional view of a section of another embodiment of a flow tube according to one or more aspects of the present disclosure. 
         FIG. 8  is a cross-sectional view of a section of another embodiment of a flow tube according to one or more aspects of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of various embodiments. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. Moreover, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the first and second features, such that the first and second features may not be in direct contact. 
     As used herein, the terms “up” and “down”; “upper” and “lower”; “top” and “bottom”; and other like terms indicating relative positions to a given point or element are utilized to more clearly describe some elements. Commonly, these terms relate to a reference point as the surface from which drilling operations are initiated as being the top point and the total depth of the well being the lowest point, wherein the well (e.g., wellbore, borehole) is vertical, horizontal or slanted relative to the surface. The terms “pipe,” “tubular,” “tubular member,” “casing,” “liner,” “tubing,” “drill pipe,” “drill string” and other like terms can be used interchangeably. The terms may be used in combination with “joint” to mean a single unitary length; a “stand” to mean one or more, and typically two or three, interconnected joints; or a “string” meaning two or more interconnected joints. 
     In this disclosure, “hydraulically coupled” or “hydraulically connected” and similar terms (e.g., fluidic, pneumatic), may be used to describe bodies that are connected in such a way that fluid pressure may be transmitted between and among the connected items. The term “in fluid communication” is used to describe bodies that are connected in such a way that fluid can flow between and among the connected items. It is noted that hydraulically coupled may include certain arrangements where fluid may not flow between the items, but the fluid pressure may nonetheless be transmitted. Thus, fluid communication is a subset of hydraulically coupled. 
     It is common to use subsurface valves in wells to control fluid flow through the wellbore. The subsurface valves are commonly actuated to a first position (e.g., open) by the application of hydraulic pressure, for example from the surface, and biased to the second position (e.g., closed) by a biasing mechanism (e.g., stored energy assembly), such as an enclosed pressurized fluid chamber or a mechanical spring. The fluidic pressure may be applied to a piston and cylinder assembly, for example, that acts against the biasing force of the biasing mechanism to open and hold the safety valve opened. The biasing force acts on the piston to move a flow tube to a position allowing the closure member of the valve close to move to the closed position when the fluid pressure is reduced below a certain value. Examples of some subsurface safety valves are disclosed in U.S. Pat. Nos. 4,161,219 and 4,660,646 and U.S. Patent Application Publications 2009/0266555, 2010/0006295 and 2010/0139923, which are all incorporated herein by reference. 
       FIG. 1  is a schematic of a well  10  incorporating an embodiment of a subsurface safety valve  12  comprising a flow tube according to one or more aspects of the present disclosure. Depicted well  10  includes a wellbore  16  extending from a surface  18  and lined with casing  20 . A tubular string  22  is disposed in wellbore  16 . A valve  12 , described as a subsurface safety valve for purposes of description, is connected within tubular string  22 . In this example, subsurface safety valve  12  is operated by a fluidic pressure, for example hydraulic pressure. Hydraulic system  24  can provide hydraulic pressure to subsurface safety valve  12  through a manifold  26  and control line  28 . 
     Hydraulic pressure is provided through control line  28  to subsurface safety valve  12  actuating valve closure member  30  to the open position allowing fluid to flow across subsurface safety valve  12  within tubular string  22 . Hydraulic pressure is maintained above a certain level to hold valve closure member  30  in the open position. To actuate subsurface safety valve  12  to the closed position, as shown in  FIG. 1 , the hydraulic pressure via control line  28  is reduced below a certain level. As is known in the art, the hydraulic pressure is reduced below the level of the force that biases valve closure member  30  to the closed position. 
       FIG. 2  is a partial cross-section view of an embodiment of a subsurface valve  12  and flow tube  36  according to one or more aspects of the present disclosure illustrated in the open position. Depicted valve  12  is a subsurface safety valve comprising a housing  32  having a longitudinal bore  34 . Valve closure member  30  is a flapper in this embodiment. An engaging member  36  (e.g., flow tube, sleeve, tubular member) having a central longitudinal bore co-axially aligned with bore  34  of housing  32  is movably disposed within housing  32 . An engaging member  36  is generally referred to as a flow tube. In this embodiment, the valve actuation assembly comprises a piston  38  disposed with flow tube  36 . Piston  38  is positioned within cylinder  14  and is in fluidic connection with fluidic chamber  42 . Biasing mechanism  40  biases flow tube  36  upward in the embodiment depicted in  FIGS. 1 and 2  toward the closed position. Biasing mechanism  40  is illustrated as a spring but may include alternatively or in combination other biasing mechanism such as and without limitation a pressurized fluid. 
     To open subsurface safety valve  12 , as illustrated in  FIG. 2 , fluid pressure is applied through control line  28  to piston  38  positioned in cylinder  14  providing a downward force on flow tube  36  that is greater than the counteracting force applied to flow tube  36  by biasing mechanism  40 . The terminal end  44 , referred to herein as contact end, of flow tube  36  physically contacts closure member  30 , or a lever or other closure member device, moving flapper  30  about pivot connection  46  to the open position permitting fluid flow through bore  34  opened through valve  12  and flow tube  36  toward the surface. Subsurface valve  12  is maintained in the open position by the maintenance of hydraulic pressure against piston  38 . 
     To close subsurface safety valve  12 , for example due to a pressure kick in the well, the hydraulic pressure can be relieved from control line  28  to a level such that biasing mechanism  40  moves flow tube  36  permitting valve closure member  30  to close. It is often desired for valve  12  to respond quickly to a close signal. As a result, closure member  30  can slam against flow tube  36 , in particular contact end  44 . 
     As further described below, flow tube  36  comprises a bottom portion  48  that includes contact end  44  and that has a material characteristic that quantitatively differs from the same material characteristic of upper portion  50  of flow tube  36 . The material characteristics may include, without limitation, one or more of strength, elasticity (e.g., modulus of elasticity), flexibility, coefficient of friction (e.g., resistance to fluid flow), anti-galling, and the like. For example, the bottom portion  48  can be constructed to be more resistant to deformation and/or galling relative to upper portion  50 . Bottom portion  48  may have a first material characteristics that has a lower coefficient of friction and reduces the resistance to the flow of fluid and debris relative to top portion  50 . In some embodiments, bottom portion  48  may be more flexible and/or have a greater yield strength than upper portion  50 . In some embodiments bottom portion  48  can have a strength greater than the upper portion  50  and in other embodiment bottom portion  48  can have a strength less than or the same as upper portion  50 . 
     In some embodiments, bottom portion  48  is a separate piece of material connected with the upper portion  50  for example by welding, bonding and threading. In other embodiments, bottom portion  48  may be continuous portion of flow tuber  36  with upper portion  50 . The material of construction of bottom portion  48  may be the same or different than that material of construction of upper portion  50 . The different material characteristic of bottom portion  48  from upper portion  50  may be achieved by the material of construction, the manner of construction, and/or inclusion a material characteristic changing element (e.g., substance). For example, a layer of material may be disposed with on a surface of bottom portion  48 . The characteristic changing element or material may be disposed with bottom portion  48 , by coating, deposition, or attachment (e.g., bonding, welding, etc.) as a layer of material. For example, bottom portion  48  can be a section of flow tube  36  that comprises a layer of material or the like that has a material characteristic such as higher strength than that of the upper portion  50 . For example, bottom portion  48  may comprise a layer or strip of material on the inner surface  52  and/or exterior surface  54  ( FIGS. 3B and 4 ) that creates provides a different material characteristic between bottom portion  48  and upper portion  50 . For example, a material disposed (e.g., by deposition) on the exterior surface  54  of bottom portion  48  can limit galling and abrasion and/or reduce friction along the interior wall  56  of housing  32  ( FIG. 3B ). 
       FIG. 3A  is a partial cross-sectional view of another embodiment of a subsurface valve  12 , depicted in the open position, utilizing a flow tube  36  according to one or more aspects of the present disclosure. In this embodiment, contact end  44  of flow tube  36  comprises is profiled, for example as disclosed in U.S. Patent Appl. Publ. 2010/0139923 which is incorporated herein by reference. In the open position, fluid is flowing through the longitudinal bore  34  of valve  12  toward the surface. 
       FIG. 3B  is a partial cross-sectional view of subsurface valve  12  of  FIG. 3A , depicted in the closed position, utilizing a flow tube  36  according to one or more aspects of the present disclosure. 
       FIG. 4  is a cross-sectional view of section a flow tube  36  according to one or more aspects of the present disclosure. Flow tube  36  comprises bottom portion  48  terminating at contact end  44  and an upper portion  50 . Upper portion  50  and bottom portion  48  have different material characteristics (e.g., yield strength, elastic flex, reduced friction). For example, bottom portion  48  is harder and/or has a higher yield strength than upper portion  50  in the depicted embodiment, to withstand the higher flow induced flow forces and/or impact forces associated with closure of the valve. Upper portion  50  may be constructed of less expensive material, for example carbon steel, than the bottom portion  48 . Examples of materials of construction of bottom portion  48  include, without limitation, nickel based alloys, cobalt-based alloys, and composite materials. 
     In the depicted embodiment, bottom portion  48  is a unitary piece that is connected to upper portion  50  via a connection  58 . Connection  58  may be by any manner suitable for connecting the opposing pieces, for example threading, bonding and welding. Connection  58  is depicted in  FIG. 4  as welding or bonding. Connection  58  is depicted in  FIG. 5  as a threaded connection. 
       FIG. 6  is a cross-sectional view of another embodiment of a flow tube  36  according to one or more aspects of the present disclosure. In this embodiment, bottom portion  48  is constructed of a two or more layers of material, the layers indentified as  48   a ,  48   b ,  48   c , etc. The layers may be constructed of the same material or of different materials. For example, layers  48   a ,  48   b ,  48   c  are constructed of the same material in the depicted embodiment. For example, layers  48   a ,  48   b  and  48   c  are flat metal plates (e.g., steel) that are welded together and formed into the tubular (e.g., cylindrical) bottom portion  48 . Bottom portion  48  is then connected to upper portion  50  via connection  58 . Connection  58  is depicted as a weld in this embodiment by way of an example. The manner of construction of bottom portion  48 , for example by layering material, can provide a the desired material characteristic. For example, utilizing a layered construction can provide increased strength, flexibility, and/or elasticity. 
       FIGS. 7 and 8  are cross-sectional views of a portion of a flow tube  36  according to one or more aspects of the present disclosure. In  FIG. 7  a material characteristic element (e.g., material, substance)  60  which is referred to as a strip for purposes of description herein is disposed at the inner surface  52  of flow tube  36 . Strip  60  is depicted disposed along the outer surface  54  of flow tube  36  in  FIG. 8 . Strip  60  comprises a material having a desired material characteristic and/or which provides a desired material characteristics when disposed with bottom portion  48 . Strip  60  may be a material that has a high strength such that a surface layer of high strength is formed on bottom portion  48 . For example, strip  60  may comprise, without limitation, a nickel-based alloy or a cobalt-based alloy. Strip  60  may comprise one or more materials to achieve the desired material characteristics. For example, strip  60  may be formed of layers of material such as described generally with reference to  FIG. 6 . As described above, material  60  may provide and/or achieve a material characteristic other than strength, for example strip  60  may be a material that reduces the friction of a surface of bottom portion  48 . Strip  60  may be disposed on bottom portion  48  by coating, deposition, or welding for example. 
     Bottom portion  48  and upper portion  50  are depicted in  FIG. 7  as a sections of a unitary tubular flow tube  36  in which strengthened strip  60  is set along the inner surface  52 . In  FIG. 8 , bottom portion  48  is depicted as an individual member that is connected to upper portion  50  via connection  58 . 
     The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions and alterations herein without departing from the spirit and scope of the present disclosure. The scope of the invention should be determined only by the language of the claims that follow. The term “comprising” within the claims is intended to mean “including at least” such that the recited listing of elements in a claim are an open group. The terms “a,” “an” and other singular terms are intended to include the plural forms thereof unless specifically excluded.