Patent Publication Number: US-10309194-B2

Title: Downhole fluid valve

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is the National Stage of, and therefore claims the benefit of, International Application No. PCT/US2014/038129 filed on May 15, 2014, entitled “DOWNHOLE FLUID VALVE,” which was published in English under International Publication Number WO 2015/174980 on Nov. 19, 2015. The above application is commonly assigned with this National Stage application and is incorporated herein by reference in its entirety. 
     TECHNICAL BACKGROUND 
     This disclosure relates to a downhole fluid valve, for example, a distributor valve. 
     BACKGROUND 
     Prior to performing a drill stem test, packers can be used to isolate sections of the annulus between the wellbore and the testing string. When a packer is used, a pressure differential can exist between the uphole and downhole sides of the packer. A high pressure differential can stress the surrounding formation to the point of damaging the formation. A high pressure differential can also cause a wellbore fluid (e.g., drilling fluid or “mud” or otherwise) to flow around the packer though fractures. The pressure differential can be mitigated by distributing the pressure across multiple packers. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  illustrates an example well system that includes a downhole fluid valve, such as a distributor valve; 
         FIG. 2A  illustrates an example implementation of a distributor valve; 
         FIG. 2B  illustrates a cross-sectional view of an example implementation of the distributor valve in a closed position; 
         FIG. 2C  illustrates a cross-sectional view of an example implementation of the distributor valve in an open position; and 
         FIG. 3  illustrates a cross-sectional view of a portion of an example implementation of the distributor valve. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure relates to a downhole fluid valve in a wellbore. The fluid valve is able to regulate the pressure in an isolated section of an annulus, e.g., fluidly isolated between two or more seals (e.g., packers). The fluid valve uses a fluid chamber as a reference to maintain the annulus pressure at a desired pressure. The pressure of the fluid in the fluid chamber can be determined prior to insertion of the valve into the wellbore, and as such the desired annulus pressure can be determined prior to insertion. When wellbore hydrostatic pressure at the fluid valve&#39;s location is greater than the pressure of a pressurized fluid (e.g., a gas such as nitrogen) in the fluid chamber, the fluid valve opens a conduit between the tubing and the annulus. When fluid flows through the wellbore (e.g., production) by, for instance, opening another flow device (e.g., tester valve) uphole of the fluid valve is established, the tubing pressure decreases. The open fluid valve allows annulus fluid to escape into the tubing, reducing the pressure in the annulus. When the tubing pressure at the fluid valve is less than the pressure in the fluid chamber, the fluid valve closes, isolates the annulus from the tubing, and establishes a desired pressure in the annulus. 
     In one general implementation, a downhole distributor valve includes a housing that includes a housing fluid port therethrough, a mandrel that defines a bore and is positioned radially within the housing, the mandrel including a mandrel fluid port therethrough, and a fluid chamber radially defined between the housing and the mandrel and configured to contain a fluid at a particular pressure, the mandrel moveable from a first position with the bore fluidly decoupled from the housing fluid port to a second position with the bore fluidly coupled with the housing fluid port through the mandrel fluid port based on a hydrostatic pressure in the bore greater than the particular pressure of the pressurized fluid. 
     In a first aspect combinable with the general implementation, the fluid chamber includes a gas chamber, and the fluid at the particular pressure includes a gas at the particular pressure. 
     In a second aspect combinable with any of the previous aspects, the gas includes nitrogen. 
     A third aspect combinable with any of the previous aspects further includes a fluid fill port at the exterior surface of the housing that is fluidly coupled to the fluid chamber. 
     In a fourth aspect combinable with any of the previous aspects, the mandrel is moveable from the second position with the bore fluidly coupled with the housing fluid port through the mandrel fluid port to the first position with the bore fluidly decoupled from the housing fluid port based on the hydrostatic pressure in the bore less than the particular pressure of the fluid in the fluid chamber. 
     In a fifth aspect combinable with any of the previous aspects, the particular pressure is based, at least in part, on a difference in an estimated downhole temperature and an estimated surface temperature. 
     In a sixth aspect combinable with any of the previous aspects, the mandrel includes a radial outer surface between an upper seal positioned between the mandrel and the housing and a lower seal positioned between the mandrel and the housing, the radial surface including an effective force area between the pressurized fluid and the hydrostatic pressure. 
     In another general implementation, a method includes moving a distributor valve at a closed position into a wellbore, the distributor valve including a housing that comprises a housing fluid port, a mandrel that defines a bore and is positioned radially within the housing, and a fluid chamber radially defined between the housing and the mandrel, moving the distributor valve toward a downhole location in the wellbore at the closed position, the bore fluidly decoupled from the housing fluid port at the closed position, and based on a hydrostatic pressure in the bore that is greater than a particular pressure of a fluid contained in the fluid chamber, adjusting the distributor valve to an open position by urging the mandrel, with the hydrostatic pressure, to fluidly couple the bore to the annulus through a mandrel fluid port and the housing fluid port. 
     A first aspect combinable with the general implementation further includes including charging the fluid chamber with an amount of the fluid to the particular pressure prior to moving the distributor valve into the wellbore. 
     A second aspect combinable with any of the previous aspects further includes determining the particular pressure based at least in part on a difference in an estimated temperature in the wellbore at the downhole location and an estimated surface temperature. 
     In a third aspect combinable with any of the previous aspects, the gas includes nitrogen. 
     In a fourth aspect combinable with any of the previous aspects, the downhole location in the wellbore is uphole of a first seal that fluidly decouples a portion of the annulus downhole of the first seal from a portion of the annulus uphole of the first seal, the method further including locating a second seal uphole of the downhole location and setting the second seal to fluidly decouple a portion of the annulus uphole of the second seal from a portion of the annulus between the first and second seals. 
     A fifth aspect combinable with any of the previous aspects further includes adjusting the distributor valve to the open position based on setting the second seal. 
     A sixth aspect combinable with any of the previous aspects further includes opening a tester valve in fluid communication with the distributor valve in a downhole work string, the tester valve positioned uphole of the distributor valve in the downhole work string and flowing a wellbore fluid through the bore and toward a terranean surface based on opening the tester valve. 
     A seventh aspect combinable with any of the previous aspects further includes based on opening the tester valve, adjusting the distributor valve to the closed position by urging the mandrel, with the pressurized fluid contained in the fluid chamber, to fluidly decouple the bore from the annulus. 
     An eighth aspect combinable with any of the previous aspects further includes misaligning the mandrel fluid port and the housing fluid port to fluidly decouple the bore from the annulus. 
     In another general implementation, a downhole valve includes an outer case that includes a flow path port therethrough, a mandrel that defines a bore and is positioned radially within the case, the mandrel including a fluid port therethrough, and a pressurized gas chamber that encloses an amount of gas at a predetermined pressure, the pressurized gas chamber defined between the outer case and the mandrel, the mandrel moveable from a closed position with the bore fluidly decoupled from the flow path to an open position with the bore fluidly coupled with the flow path through the fluid port based on a hydrostatic pressure in the bore greater than the predetermined pressure of the gas. 
     In a first aspect combinable with the general implementation, the mandrel is moveable from the open position with the bore fluidly coupled with the flow path through the fluid port to the closed position with the bore fluidly decoupled from the flow path based on the hydrostatic pressure in the bore less than the predetermined pressure of the gas. 
     In a second aspect combinable with any of the previous aspects, the pressurized gas chamber includes a self-contained chamber that is fluidly decoupled from the exterior during operation of the valve. 
     In a third aspect combinable with any of the previous aspects, the predetermined pressure is determined based, at least in part, on at least one of a downhole temperature or a characteristic of a subterranean zone. 
     Various implementations of a downhole fluid valve according to the present disclosure may include none, one or some of the following features. The fluid valve is a self-contained system that is comparatively easy to adjust and maintain. For example, the pressure of the fluid in the fluid chamber can be set accurately through a port on the housing of the fluid valve. Furthermore, a fluid chamber may have a greater precision than a mechanical mechanism (e.g., a spring) for opening and closing the fluid valve at a desired pressure. A fluid chamber can have a wider operating range than a spring-based system due to geometric constraints imposed by use of springs. During disassembly, a fluid chamber can be bled fully of its pressure to neutralize any residual force. 
       FIG. 1  illustrates an example well system  100  that includes a downhole fluid valve, such as a distributor valve  145 . The well system  100  is provided for convenience of reference only, and it should be appreciated that the concepts herein are applicable to a number of different configurations of well systems. As shown, the well system  100  includes a downhole tool string  130  within a substantially cylindrical wellbore  115  that extends from a terranean surface  105  through one or more subterranean zones  110 . The wellbore  115  can be an openhole wellbore, a cased wellbore, or a partially cased wellbore.  FIG. 1 , however, illustrates an implementation in an open hole (e.g., uncased) wellbore. Moreover, although illustrated as extending from the terranean surface  105 , the wellbore  115  (and well system  100 ) can be constructed in an ocean-based environment or other environment that includes a body of water. 
     In  FIG. 1 , the wellbore  115  extends substantially vertically from the terranean surface  105 . However, in other instances, the wellbore  115  can be of another position, for example, the wellbore  115  deviates horizontally in the subterranean zone, or entirely substantially vertical or slanted. The wellbore  115  may deviate in another manner than horizontal, such as multi-lateral, radiussed, slanted, directional, and/or may be of another position. 
     The illustrated example well system  100  includes an upper seal  120  and a lower seal  125 . The upper seal  120  and lower seal  125  are coupled to the tool string  130  and are located in the annulus  140  between the tool string  130  and the sidewall of the wellbore  115 . The seals  120 ,  125  isolate sections of the annulus  140 . The seals  120 ,  125  can be any suitable sealing apparatus such as a packer. The tool string  130  includes the distributor valve  145  that is located between the seals  120 ,  125  and thus adjacent to a section of annulus  140  that is isolated (e.g., fluidly) from sections of the annulus  140  that are uphole and downhole of the seals  120  and  125 , respectively. 
     Generally, the distributor valve  145  may regulate pressure between openhole (or even possibly cased) seals  120  and  125  (e.g., packers). Distributing the differential pressure load across two or more seals may be advantageous when testing weak or vertically fractured subterranean zones or geologic formations. For example, a high differential across any single seal (e.g., packer) may cause an annulus fluid to communicate around the seal through a vertical fracture. In addition, distribution of the pressure may also help keep the formation from crushing under excessively high hydrostatic loadings of a single seal (e.g., packer). Regulating the pressure between two seals may help prevent buildup of excessive pressure when the seals (e.g., packers) are set. Regulating the pressures can also be helpful if the performance of one or more packers has been compromised or is suspected to have been compromised. 
     In some implementations, the distributor valve  145  may operate to regulate pressure (e.g., annulus pressure) between the seals  120 ,  125  by opening and closing a conduit between the annulus  140  and the tool string  130 . The distributor valve  145  includes a fluid chamber that contains a pressurized fluid. When the pressure at the location of the distributor valve  145  is greater than the pressure of the fluid in the fluid chamber, the distributor valve  145  opens. When the pressure at the location of the distributor valve  145  is less than the pressure of the fluid in the fluid chamber, the distributor valve  145  closes. 
       FIG. 2A-2C  illustrate an example well system  200 , including an example implementation of a distributor valve  202 . The well system  200  is substantially similar to the well system  100  shown in  FIG. 1 , and the distributor valve  202  may be substantially similar to the distributor valve  145  shown in  FIG. 1 . The distributor valve  202  is included as part of tool string  130  that is located within the wellbore  115 . 
     The illustrated distributor valve  202  includes a housing  208  coupled to a top adapter subassembly  204  and a bottom adapter subassembly  210 . The housing  208  extends all or a portion of the length of the distributor valve  202 . The top adapter subassembly  204  is attached (e.g., threadingly) to an uphole end of the housing  208 . The top adapter subassembly  204  allows other tools, tubing, or other components (such as a packer tool) to be coupled to the uphole end of distributor valve  202 . Likewise, the bottom adapter subassembly  210  is attached (e.g., threadingly) to a downhole end of the housing  208  to allow tools, tubing, or other components to couple to the downhole end of distributor valve  202 . 
     In the illustrated implementation, the top subassembly  204  includes housing ports  214  that provide flow paths from an exterior of the distributor valve  202  (e.g., the annulus  140 ) through the top subassembly  204 . In some implementations, the housing ports  214  are located on the housing  208  and provide flow paths from the exterior through the housing  208 . 
       FIG. 2B  illustrates a cross-sectional view of an example implementation of the distributor valve  202  in a closed position.  FIG. 2C  illustrates a cross-sectional view of an example implementation of the distributor valve  202  in an open position. The distributor valve  202  includes a through bore  208  that extends axially through the distributor valve  202 . The through bore  208  allows fluid to be communicated through the tool string  130 . 
     The distributor valve  202  includes a mandrel  218  surrounding and defining a portion of the through bore  228 . The mandrel  218  is positioned radially within the housing  208 . The mandrel  218  includes a set of upper mandrel ports  224  formed through the mandrel  218  that are positioned circumferentially around an upper portion of the mandrel  218 . The mandrel  218  also includes a set of lower mandrel ports  226  formed through the mandrel  218  that are positioned circumferentially around a lower portion of the mandrel  218 . The mandrel  218  is moveable between a first position (shown in  FIG. 2B ) with the through bore  228  fluidly decoupled from housing ports  214  and a second position (shown in  FIG. 2C ) with the through bore  228  fluidly coupled to housing ports  214  through upper mandrel ports  224 . 
     A radial outer surface of the mandrel  218  and a radial inner surface of the housing  208  define a fluid chamber  222 . As such, the fluid chamber  222  is radially located between the mandrel  218  and the housing  208 . The fluid chamber  222  is configured to contain fluid at a particular pressure, and is fluidly isolated by an upper seal  216  positioned between the mandrel  218  and the housing  208  and a lower seal  216  positioned between the mandrel  218  and the housing  208 . The fluid chamber  222  is fluidly connected to fill port  206  by fill conduit  220 . Fill port  206  is a sealable port located at the exterior surface of the top subassembly  204 . Through fill port  206 , the fluid chamber  222  can be filled with a fluid or gas at a particular pressure. In some implementations, the fluid is nitrogen gas, but other pressurized fluids, such as compressible, non-flammable, gases are also contemplated by the present disclosure. 
     A lower chamber  234  is defined by the mandrel  218 , the housing  208 , and the bottom subassembly  210 . The lower chamber  234  is fluidly connected to the through bore  228  by lower mandrel ports  226 . The lower chamber  234  is fluidly isolated from the fluid chamber  222  and the annulus  140  by multiple seals  216 . 
     As illustrated in  FIG. 2B , a particular seal  216  is positioned between the mandrel  218  and the top subassembly  204  adjacent an uphole end of the pressure chamber  222 , while another particular seal  216  is positioned between the mandrel  218  and the housing  208  adjacent a downhole end of the pressure chamber  222 . In the illustrated implementation, these two seals  216  may be of different diameters so that, for example, the mandrel  218  may move to open the valve  202  (as shown in  FIG. 2C ) when a pressure in the bore  228  exceeds a pressure in the chamber  222 . 
     In an example operation, the distributor valve  202  is lowered into the well  115  with the distributor valve  202  in the closed position as shown in  FIG. 2B . The annulus  140  may not yet be isolated by seals  120 ,  125 , so the hydrostatic pressure in the annulus  140  is approximately equal to the pressure in the through bore  228 . The lower chamber  234  has a pressure approximately equal to the pressure in the through bore  228 . The fluid chamber  222  has been pre-filled to a particular pressure prior to the distributor valve  202  being lowered into the well  115 . Initially, the pressure in the fluid chamber  222  is greater than the pressure in the lower chamber  234  and the bore  228 , and the differential area between fluid chamber  222  and lower chamber  234  impart a net force to maintain the mandrel  218  in the closed position (e.g., shouldered out against the lower sub-assembly  210 ). 
     As the distributor valve  202  is lowered into the well  115 , the hydrostatic pressure in the well  115  at the location of the distributor valve  202  increases. Thus, the pressure in the annulus  140 , the through bore  228 , and the lower chamber  234  will increase. If the pressure in the lower chamber  234  increases beyond the particular pressure of the fluid in the fluid chamber  222 , the net force on the mandrel  218  will shift the mandrel  218  upward into the open position ( FIG. 2C ), opening the distributor valve  202 . The shoulder  212  limits the upward movement of the mandrel  218 . 
     When in the open position, the upper mandrel ports  224  are aligned with the housing ports  214  so that the through bore  228  is fluidly coupled to the annulus  140 . Once the lower seal  125  downhole of the distributor valve  202  is set, the only fluid communication between the annulus  140  and the through bore  228  happens through the distributor valve  202 . The lower seal  125  and upper seal  120  are set (e.g., by compression), and the fluid between the seals  120 ,  125  will be squeezed as the upper seal  120  is setting. Thus, setting an upper seal  120  will further increase the fluid pressure in the annulus  140  and through bore  228 . 
     The increase in fluid pressure due to seal setting can cause detrimental effects to both the reservoir and the seals  120 ,  125  themselves. The presence of an open distributor valve  202  in between the two seals  120 ,  125  gives the fluid an escape path so as to reduce or eliminate this pressure spike. In some implementations, the distributor valve  202  is closed prior to setting the upper seal  120 , and the increase in fluid pressure from setting the upper seal  120  raises the pressure in the through bore  228  sufficiently to overcome the fluid chamber  222  pressure and open the distributor valve  202 . 
     After the upper seal  120  and lower seal  125  are set, the tester valve  135  may be opened. Opening the tester valve  135  flows well fluid in the through bore  228 . Once fluid flows in the through bore  228 , the fluid pressure within the through bore  228  decreases. The annulus  140  also decreases, because the through bore  228  and the annulus  140  are fluidly coupled through the open distributor valve  202 . Once the pressure in the through bore  228  has decreased sufficiently below the pressure within the fluid chamber  222 , the higher pressure in the fluid chamber  222  moves the mandrel  218  down, misaligning the upper mandrel ports  224  and the housing ports  214 . The distributor valve  202  is thus closed by fluidly decoupling the through bore  228  from the housing ports  214 . 
     Before closing, the distributor valve  202  allows enough fluid to escape from the annulus  140  into the through bore  228  to reduce the between-the-seals annulus  140  pressure to the predetermined pressure of the fluid chamber  222 . The pressure in the isolated section of the annulus  140  between the seals  120 ,  125  will thus have a lower pressure than the pressure in the section of the annulus  140  above the upper seal  120  and a higher pressure than the pressure in the section of the annulus  140  below the lower seal  125 . Since the isolated section of the annulus  140  has an intermediate pressure, the differential pressure each seal  120 ,  125  has to seal against is reduced. 
       FIG. 3  illustrates a cross-sectional view (as indicated in  FIG. 2B ) of a portion of an example implementation of the distributor valve  202 .  FIG. 3  shows the fill port  206  on the outside surface of the top subassembly  204 . The fill port  206  is fluidly coupled to the fluid chamber  222  via fluid conduit  220 . The fill cap  230  seals the fill port  206  to isolate the fluid chamber  222  from the exterior of the distributor valve  202 . The fill cap  230  is secured by set screw  232 . In some implementations, the fill port  206  is located on the outside surface of the housing  208  or the bottom subassembly  210 . The fluid chamber  222  can be filled with a fluid or a gas through fill port  206 . For example, the fluid chamber  222  can be filled with nitrogen, air, carbon dioxide, or another gas or fluid. The fluid chamber  222  is filled with fluid prior to moving the distributor valve  202  into the wellbore  115 . The fluid chamber  222  can be filled with fluid at a particular pressure to set the hydrostatic pressure at which the distributor valve  202  opens. The particular pressure within the fluid chamber  222  can be determined based on estimated or calculated downhole conditions. For example, the particular pressure can be based, at least in part, on the difference between the estimated downhole temperature, pressure, or chamber volume and the estimated surface temperature, pressure, or chamber volume. This particular pressure can also be based on the difference between the volume of the fluid chamber when the tool is fully closed and when it is beginning to open. 
     A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made. For example, example operations, methods, and/or processes described herein may include more steps or fewer steps than those described. Further, the steps in such example operations, methods, and/or processes may be performed in different successions than that described or illustrated in the figures. Accordingly, other implementations are within the scope of the following claims.