Patent Publication Number: US-8118098-B2

Title: Flow control system and method for use in a wellbore

Description:
BACKGROUND 
     In well procedures related to perforating, valves are sometimes combined with the perforating string moved downhole. The valves can be used to control flow in the downhole environment during, for example, production of fluids or isolation of wellbore regions for specific procedures. 
     The valves are actuated by a variety of mechanisms and procedures. In some designs, valve actuation is initiated by the shearing of shear pins. Other valves are explosively triggered or mechanically actuated by dropping a bar from a surface location. Each of these valve designs requires intervention for actuation. 
     SUMMARY 
     In general, the present invention provides a well related system that utilizes an interventionless valve system to control flow of fluid in a downhole environment. The valve system comprises at least one intelligent valve selectively actuated by a device responsive to a unique pressure and time signal. Actuation of the valve controls fluid flow between the interior of a well equipment string, e.g. a perforating gun string, and exterior regions within the wellbore. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Certain embodiments of the invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and: 
         FIG. 1  is an elevation view of a wellbore with a well equipment string therein, according to an embodiment of the present invention; 
         FIG. 2  is a schematic illustration of a valve system that may be combined with the well equipment string, illustrated in  FIG. 1 , according to an embodiment of the present invention; 
         FIG. 3  is a schematic illustration similar to that of  FIG. 2  but showing the valve system from a different angle, according to an embodiment of the present invention; 
         FIG. 4  is an expanded view of a valve retention system, according to an embodiment of the present invention; 
         FIG. 5  is a schematic illustration of an alternate embodiment of the valve system illustrated in  FIG. 2 , according to an embodiment of the present invention; 
         FIG. 6  is a schematic illustration similar to that of  FIG. 5  but showing the valve system from a different angle, according to an embodiment of the present invention; 
         FIG. 7  is a schematic illustration of an embodiment of a trigger system for actuating the valve system, according to an embodiment of the present invention; and 
         FIG. 8  is a graphical illustration of one embodiment of a pressure and time signal used to activate the trigger system illustrated in  FIG. 7 , according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood by those of ordinary skill in the art that the present invention may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible. 
     The present invention relates to a system and methodology for controlling flow of fluid in a downhole environment. In various well related operations, a valve system can be used to, for example, equalize or isolate pressure between an interior of tubing or other equipment and the exterior region. The valve system is useful in downhole perforating operations to equalize pressure or to isolate pressure from the inside of the tubing of the perforating gun string to the outside of the perforating gun string. Furthermore, the valve system is designed as an interventionless system. 
     Referring generally to  FIG. 1 , a well  20  comprises a wellbore  22  that extends downwardly through one or more subterranean formations  24 . The formations  24  often hold desired production fluids, such as hydrocarbon based fluids. In the example illustrated, wellbore  22  extends downwardly from a wellhead  26  located at a surface  28  above wellbore  22 . Surface  28  may comprise a surface of the earth or a seabed floor. 
     A well equipment string  30  is deployed in wellbore  22  and a may have a variety of configurations depending on the specific well operation to be performed. In many applications, well equipment string  30  is a perforating gun string having one or more perforating guns  32  and a firing head  34 . A wellbore isolation mechanism  36 , such as a packer, can be used to isolate regions of wellbore  22 , such as a rat hole region  38  located below packer  36 . A valve system  40  is combined with the well equipment string  30 , e.g. a perforating gun string, to control flow and to equalize or isolate pressures between an interior  42  of the string, typically the tubing interior, and an exterior  44  that surrounds the string within wellbore  22   
     Depending on the specific application, string  30  can be deployed into wellbore  22  by a variety of deployment mechanisms  46 , such as tubing. Also, wellbore  22  may be lined with a casing  48  that is perforated upon detonation of perforating gun  32  to form perforations  50 . Perforations  50  enable, for example, the flow of hydrocarbon fluids from formation  24  into wellbore  22  and/or the flow of well treatment fluids from wellbore  22  into the surrounding formations. 
     An embodiment of valve system  40  is illustrated in  FIGS. 2 and 3 . In this embodiment, valve system  40  is a modular system having an outer housing  52  that may be coupled into the well equipment string  30  by, for example, a first connector end  54  and a second connector end  56  opposed from connector end  54 . In the embodiment illustrated, connector ends  54  and  56  are internally threaded and externally threaded ends, respectively. Housing  52  generally comprises a main body section  58  and a valve section  60  that may be formed as an integral unit or as separable modular sections held together by fasteners, such as threaded ends or bolts. 
     Main body section  58  is designed to accommodate one or more activation devices  62  used to activate one or more corresponding valves  64  located in valve section  60 . In the embodiment illustrated in  FIG. 2 , a single activation device  62  is used to activate a single valve  64 . The activation device  62  is responsive to a pressure and time signal transmitted downhole through wellbore  22  instead of through hydraulic control lines extending to the surface. When the unique pressure and time signal is received, activation device  62  activates valve  64  from a first state to a second state, e.g. from an open position to a closed position or from a closed position to an open position. The unique pressure and time signal may comprise low pressure signals sent downhole according to a specific time sequence. In other words, the pressures, e.g. pressure pulses, can be applied at a pressure lower than pressures typically used with devices actuated by pressure applied downhole. 
     The pressure and time signal may be transmitted to activation device  62  via a sensing port  66  located in housing  52 . The sensing port  66  can be exposed to an interior  68  of housing  52  if the pressure and time single is transmitted downhole within tubing string  46 . Housing interior  68  forms a portion of the overall interior  42  of the tubing string. Alternatively, sensing port  66  can be directed to the exterior of the outer housing  52  to receive a pressure and time signal transmitted through the wellbore annulus surrounding string  30 . In the embodiment illustrated, receipt of the appropriate pressure and time signal, causes activation device  62  to open an activation port  70  to hydrostatic pressure in the wellbore. This pressure is used to actuate valve  64 , as explained in greater detail below. 
     Main body section  58  can be a side pocket mandrel type design with room for one or more activation devices  62 . In this design, the activation devices  62  are mounted externally along housing  52 . The interior  68  through the main body section  58  is offset from the true tool centerline to provide sufficient wall thickness for mounting activation devices  62  while maintaining a large internal flow path. Also, the activation devices  62  may be mounted in corresponding slots  72  formed in housing  52  (see also  FIG. 3 ) and connected to the corresponding sensing port  66  and activation port  70  via sealable blocks  74 . In the specific embodiment illustrated, housing  52  comprises two slots  72 , as illustrated best in  FIG. 3 . One of the slots  72  contains the activation device  62  cooperating with valve  64 , and the other slot  72  remains blank. Any ports  66 ,  70  in the unused slot can be sealed shut with appropriate blanking blocks  76 . By way of example, blocks  74  and blanking blocks  76  can be sealed to outer housing  52  via o-ring type face seals. Additionally, blocks  74  and blanking blocks  76  can be attached to housing  52  via a variety of suitable mechanisms, such as capscrews. 
     Referring again to  FIG. 2 , valve  64  comprises a valve sleeve  78  that slides within a cylindrical region  80  of valve section  60  formed along an interior of housing  52 . Valve sleeve  78  comprises at least one and often a plurality of sleeve ports  82  that extend between an interior and exterior of the sleeve. For example, sleeve ports  82  may be in the form of radial ports extending through valve sleeve  78 . Housing  52  comprises corresponding ports  84  that complete a pathway between interior  42  and exterior  44  when valve  64  is in an open position such that sleeve ports  82  and corresponding ports  84  are generally aligned. 
     In the embodiment illustrated, valve  64  is designed for deployment downhole in an open state. An atmospheric chamber  86 , such as an air chamber, may be positioned to allow the sleeve to shift when pressure is allowed through activation port  70 . Once the pressure and time signal is transmitted downhole to activation device  62 , activation port  70  is opened to hydrostatic pressure of the wellbore. The hydrostatic pressure drives valve sleeve  78  toward chamber  86  and moves sleeve ports  82  out of alignment with corresponding ports  84 , thereby closing valve  64  and blocking communication between interior  42  and exterior  44 . Additionally, a plurality of seals  88 , e.g. o-ring seals, can be positioned between valve sleeve  78  and the interior of housing  52 , as illustrated. Seals  88  can be used to isolate, for example, chamber  86 , sleeve ports  82 , and the outlet of activation port  70  through which pressure is introduced against valve sleeve  78 . A retention mechanism  90  also can be used to maintain valve sleeve  78  and valve  64  in a desired state during deployment and/or to maintain valve sleeve  78  and valve  64  in the actuated state once valve sleeve  78  is shifted, e.g. shifted from an open position to a closed position. 
     Referring generally to  FIG. 4 , an example of a retention mechanism  90  is illustrated in greater detail. In the embodiment illustrated, valve  64  is in a closed state during deployment into wellbore  22 . In other words, sleeve ports  82  and corresponding ports  84  of housing  52  are out of alignment and isolated by seals  88 . During this initial phase, valve sleeve  78  is retained in its original state via retention mechanism  90 . In this embodiment, retention mechanism  90  comprises a shear mechanism  92  having a shear ring  94  held by housing  52  and at least one shear pin  96  which extends radially from shear ring  94  into at least one corresponding mating hole  98  within valve sleeve  78 . The shear ring  94  and the at least one shear pin  96  are used to hold valve sleeve  78  in position so sleeve  78  is not inadvertently shifted while running valve system  40  and perforating gun string  30  downhole. 
     Retention mechanism  90  also may comprise a mechanism  100  for holding valve sleeve  78  in its shifted state, e.g. an open state once sleeve  78  is shifted from the illustrated closed position to an open position. In the embodiment illustrated, mechanism  100  comprises a ratchet ring  102  secured along housing  52  and having a plurality of ratchet teeth  104 . Ratchet teeth  104  are positioned to slide along a gripping region  106  of valve sleeve  78  and are designed to enable gripping region  106  and thus valve sleeve  78  to move in one direction but not the other. Accordingly, valve sleeve  78  can be actuated from a first state to a second state, but mechanism  100  prevents return movement of the valve sleeve  78  once positioned in the second state. 
     Another embodiment of valve system  40  is illustrated in  FIGS. 5 and 6 . In this embodiment, valve system  40  also is a modular system in which outer housing  52  generally comprises main body section  58 , valve section  60  and an additional valve section  108  having a valve  110  similar to valve  64 . As illustrated, the additional valve section  108  may be located on an opposite side of main body section  58  from valve section  60 . Valve section  108  also may be formed as an integral part of housing  52  or as a detachable modular section. 
     Main body section  58  is designed to accommodate activation device  62  and at least one additional activation device  112  used to activate valves  64  and  110 , respectively. Activation device  112  also is responsive to a unique pressure and time signal transmitted downhole through wellbore  22 . When the unique pressure and time signal is received, activation device  112  activates valve  110  from a first state to a second state, e.g. from a closed position to an open position. The pressure and time signal used to activate valve  110  may comprise low pressure signals sent downhole according to a specific time sequence and can be unique relative to the pressure and time signal used to activate valve  64 . 
     The pressure and time signal may be transmitted to activation device  112  via sensing port  66  or through an additional sensing port located in housing  52 . As with the embodiment illustrated in  FIGS. 2 and 3 , the sensing port can be exposed to an interior  68  of housing  52  if the pressure and time single is transmitted downhole within the tubing string  46 . Or, the sensing port can be directed to the exterior of the outer housing  52  to receive a pressure and time signal transmitted through the wellbore annulus surrounding well equipment string  30 . Receipt of the appropriate pressure and time signal causes activation device  112  to open an activation port  114  to hydrostatic pressure in the wellbore. 
     As illustrated best in  FIG. 6 , the activation devices  62  and  112  are mounted in the slots  72  formed in housing  52 . The activation devices  62  and  112  may be connected to their corresponding sensing ports and activation ports via sealable blocks  74 . 
     Valve  110  is similar to valve  64  and common reference numerals have been used to label common components in valves  110  and  64 . By way of example, valve  110  may comprise valve sleeve  78  slidably mounted within cylindrical region  80  of valve section  108  formed along an interior of housing  52 . The valve sleeve  78  of valve  110  similarly comprises at least one and often a plurality of sleeve ports  82  that extend between an interior and exterior of the sleeve. Housing  52  comprises corresponding ports  84  located in valve section  108  that complete a pathway between the interior  42  and the exterior  44  when valve  110  is in an open position such that sleeve ports  82  and corresponding ports  84  are generally aligned, as described above with reference to valve  64 . Valve  110  also comprises its own atmospheric pressure, e.g. air, chamber  86  and seals  88  to isolate the desired regions along valve sleeve  78 . Valve  110  also may incorporate retention mechanism  90  to limit inadvertent movement of sleeve  78 . In some embodiments, each section  108  and  60  also can incorporate a shock absorber in line with sleeve  78  to reduce any shock and deformation to sleeve  78  as it is shifted to its final position. In other embodiments, the valve sleeves  78  can be designed to incorporate internal shifting profiles as a backup to enable the valves to be opened or closed with standard shifting tools. 
     In the embodiment illustrated, valve  64  is initially placed in an open position, and valve  110  is initially placed in a closed position. However, valves  64  and  110  can be placed in different initial states depending on the wellbore application in which valve system  40  is utilized. Additionally, the actual operation of valve system  40  and the sequence of valve openings and/or closings can vary from one wellbore application to another. Furthermore, housing  52  can be designed as a modular housing so that valve system  40  can be converted from a dual valve system to a single valve system by removing valve section  108  and substituting a different modular top sub  116  (see  FIG. 2 ) in conjunction with replacing the second activation device  112  with blanking blocks  76 . 
     In one example of the operation of well equipment string  30 , valve system  40  comprises a single valve embodiment, such as the embodiment described with reference to  FIGS. 2 and 3 . In this embodiment, valve system  40  is combined with a perforating gun string in which an automatic gun drop can be performed. Initially, the perforating gun string and the valve system  40 , with single valve  64 , is moved downhole into the wellbore  22  with valve  64  in the open position. Valve  64  is maintained in the open position to automatically fill the tubing string. Once the perforating gun string and valve system  40  arrives at the proper depth, a cushion fluid, such as a lighter cushion fluid, is pumped down the tubing  46  to displace the heavier well fluid. Packer  36  is then set, and the appropriate pressure and time signal is transmitted downhole. Upon receiving the specific pressure and time signal, activation device  62  opens activation port  70  and valve  64  is exposed to hydrostatic well pressure which moves sleeve  78  to a closed position. The closed valve traps the appropriate pressure in rat hole  38  below automatic gun release (not shown) drops the gun string into the wellbore and opens up the tubing  46  which was used to deploy the gun string downhole. At this point, well fluid, such as hydrocarbon based fluid, can flow upwardly through the tubing to the surface. 
     In another example of the operation of well equipment string  30 , valve system  40  comprises a dual valve embodiment, such as the embodiment described with reference to  FIGS. 5 and 6 . In this embodiment, valve system  40  is combined with a perforating gun string in which an automatic gun drop is not required or in which the gun string is moved into a highly deviated or horizontal well where drop-off is not possible. Initially, the perforating gun string and the valve system  40 , with dual valves  64  and  110 , is moved downhole into the wellbore  22  with valve  64  in the open position and valve  110  in the closed position. Valve  64  is maintained in the open position to automatically fill the tubing string. Once the perforating gun string and valve system  40  is located at the proper depth, a cushion fluid is pumped down the tubing  46  to displace the heavier well fluid. Packer  36  is then set, and the appropriate pressure and time signal is transmitted downhole to close valve  64 . Following closure of valve  64 , firing head  34  is initiated and perforating guns  32  are detonated. Subsequently, a second unique pressure and time signal is transmitted downhole and received by activation device  112 . Activation device  112  opens activation port  114  to expose valve  110  to hydrostatic well pressure which causes sleeve  78  to shift and transition valve  110  from a closed position to an open position. The open valve  110  enables fluid, such as hydrocarbon fluid, to flow from the wellbore  22  and into tubing  46  for transfer to the surface. 
     It also should be noted that the above described operations employing either a single valve or a dual valve system can be used to reperforate previously perforated wells by using the procedures described. In other applications, the closure of valve  64  can be used to enable the application of increased pressure within tubing  46  to set a tubing set type packer. Valve system  40 , in fact, can be used in a variety of other environments and applications by simply transmitting low pressure and time signals downhole without the intervention of other valve shifting mechanisms. 
     As described above, the activation devices  62  and  112  are designed to respond to unique pressure and time signals, such as pressure and time signals in the form of low pressure inputs transmitted downhole in a timed sequence. Each activation device is designed to recognize its own corresponding pressure and time signal to enable dependable and selective actuation of the desired valves. The activation devices can be designed with a variety of electrical and mechanical components, however one example is described in the commonly assigned patent application Ser. No. 11/307,843, filed Feb. 24, 2006. 
     In this particular example, as illustrated in  FIGS. 7 and 8 , each actuation device  62 ,  112  comprises a pressure sensor  118 , a power supply  120 , such as a battery, an electronics module  122 , a motor  124 , an actuation component  126  and a coupler  128  to connect the motor  124  to the actuation component  126 . In this embodiment, power supply  120  provides electrical power to electronics module  122  and to motor  124 . The pressure sensor  118  detects pressure inputs, such as pressure pulses, transmitted downhole and outputs a corresponding signal to electronics module  122 . The electronics module  122  may comprise a microprocessor or other suitable electronics package to detect both the pressure inputs and the timing of the pressure inputs for comparison to a preprogrammed pressure and time signature. Upon receipt of a pressure and time signal matching the preprogrammed signature, the electronics module  122  outputs an appropriate signal to initiate operation of motor  124 . Motor  124  moves actuation component  126 , via coupler  128 , to open the appropriate activation port  70 ,  114  to initiate movement of the desired valve sleeve  78  and actuation of the valve. 
     One example of a pressure and time signature is illustrated in  FIG. 8 , although many unique pressure and time signatures and signals can be utilized for the control of individual valves. For example, the number of pressure pulses may vary, the length of each pressure pulse may vary, and the time between pressure pulses may vary. In the illustrated example, the pressure and time signature comprises three pressure pulses  130 ,  132  and  134 , respectively, located in a unique time sequence. When the pressure and time signal transmitted downhole matches the illustrated signature, the appropriate actuation device  62 ,  112  is activated to transition the corresponding valve from one state to another. 
     The specific components used to recognize the pressure and time signal and to activate the corresponding valve can be changed to accommodate differing applications and/or changes in technology. Additionally, the number of valves used in a given valve system and the design of each valve can be adjusted according to the specific well application and/or well environment. Additionally, the valve systems can be used in perforating operations and other well related operations. 
     Accordingly, although only a few embodiments of the present invention have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this invention. Such modifications are intended to be included within the scope of this invention as defined in the claims.