Abstract:
An apparatus for controlling a fluid flow in a borehole may include a tool body that retrieves a fluid sample from a subsurface formation. The tool body has a fluid conduit having an inlet for receiving the fluid sample and an outlet for conveying the fluid sample to a selected location. A mandrel selectively blocks flow across the fluid conduit; and a seal disposed on the mandrel includes at least one chevron seal element that cooperates with the mandrel to selectively block flow across the fluid conduit.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    None. 
       FIELD OF THE DISCLOSURE 
       [0002]    This disclosure pertains generally to flow control devices such as valves. 
       BACKGROUND OF THE DISCLOSURE 
       [0003]    During the drilling and completion of oil and gas wells, the downhole environment can impose substantial operational stresses on downhole equipment. These harsh conditions exposure to drilling mud, contaminants entrained in well fluids, and hydraulic forces of the circulating drilling mud. Extreme pressures and temperatures may also be present. Such harsh conditions can damage and degrade downhole equipment. Valves used in sampling, drilling, and completion operations may be susceptible to the harsh downhole conditions because they require the use of seals and moving parts. For example, valves used in a downhole environment may interact with deleterious debris carried by formation fluids and encounter significant pressure drops. 
         [0004]    The present disclosure addresses the need for sealing high differential pressure in a downhole environment, as well as in surface applications. 
       SUMMARY OF THE DISCLOSURE 
       [0005]    In aspects, the present disclosure provides an apparatus for controlling a fluid flow in a borehole. The apparatus may include a tool body configured to retrieve a fluid sample from a subsurface formation, the tool body having a fluid conduit having an inlet for receiving the fluid sample and an outlet for conveying the fluid sample to a selected location; a mandrel selectively blocking flow across the fluid conduit; and a seal disposed on the mandrel, the seal including at least one chevron seal element configured to cooperate with the mandrel to selectively block flow across the fluid conduit. 
         [0006]    In another embodiment, the apparatus may include a carrier configured to be conveyed along a borehole; a tool body positioned along the carrier, the tool body having at least one packer configured to form an isolated zone, the tool body having a fluid conduit having an inlet for receiving a fluid sample from the isolated zone and an outlet for conveying the fluid sample to a selected location; and a valve disposed in the tool body. The valve may include a mandrel configured to translate between a first and a second position to selectively block flow across the fluid conduit; and a seal disposed on the mandrel, the seal including at least one chevron seal element configured to cooperate with the mandrel to selectively block flow across the fluid conduit. 
         [0007]    In another aspect, the present disclosure provides a method for controlling a fluid flow. The method may include retrieving a fluid sample from a subsurface formation using a tool body, the tool body having a fluid conduit having an inlet for receiving the fluid sample and an outlet for conveying the fluid sample to a selected location; selectively blocking flow across the fluid conduit using a mandrel; and isolating the inlet from the outlet using a seal positioned in a passage between the mandrel and the tool body, the seal including at least one chevron seal element. 
         [0008]    Thus, the present disclosure provides seals that enhance control, operation, service life, reliability, and/or performance for valves and other flow control devices. The teachings may be applied to a variety of systems both in the oil and gas industry and elsewhere. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    For a detailed understanding of the present disclosure, reference should be made to the following detailed description of the embodiments, taken in conjunction with the accompanying drawings, in which like elements have been given like numerals, wherein: 
           [0010]      FIGS. 1A and 1B  shows sectional views of a valve according to one embodiment of the present disclosure in the open and closed positions, respectively; 
           [0011]      FIG. 2  shows a seal in accordance with one embodiment of the present disclosure; and 
           [0012]      FIG. 3  schematically shows a well system that uses a valve according to one embodiment of the present disclosure in a borehole formed in an earthen formation. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    In aspects, the present disclosure provides a “dirty” fluid valve with a bi-directional Chevron type metal seal assembly for use in tool used to sample wellbore fluids and to store such fluids in a sample bottle. The valve may be pressure balanced and may be operated in varying pressures. The seals described herein provide gas tight seal for repeated operations. 
         [0014]    Referring initially to  FIGS. 1A and 1B , there is shown a valve assembly  10  that may be used to retrieve fluid samples from a formation. The valve assembly  10  may include a body or housing  20  in which a mandrel  30  and a seal  40  are disposed. The housing  20  may include a fluid inlet  22 , a fluid outlet  24 , pressure chambers  26   a, b , and pilot holes  28   a, b . The pressure chamber  26   a  is positioned next to a first end  32  of the mandrel  30  and the pressure chamber  26   b  is positioned next to a second end  34  of the mandrel  30 . The housing  20  may be unitary or composed of several components. Therefore, it should be understood that the depicted configuration is merely illustrative and does not limit the present disclosure. 
         [0015]    In one embodiment, fluid communication between the fluid inlet  22  and the fluid outlet  24  may be controlled by shifting or translating the mandrel  30  in a cavity  42  of the housing  20 . The mandrel  30  may be a cylindrical member that includes a reduced diameter or “necked” portion  31 . When the mandrel  30  is set in the open position, the necked portion  31  forms an annular passage  48  in the housing that  20  that connects the fluid inlet  22  with the fluid outlet  24 . Thus, the inlet  22 , the passage  42 , and the outlet  24  may be considered as forming a fluid conduit in the housing  20 . Seals  62 ,  64  between the mandrel  30  and the housing  20  isolate the passage  48  from the rest of the valve  10 . To shift the mandrel  30  to the open position, the pressure chamber  26   b  is pressurized using the pilot inlet  28   b  to urge the mandrel  30  in an axial direction marked with arrow  44 . To shift the mandrel  30  to the closed position, the pressure chamber  26   a  is pressurized using the pilot inlet  28   a  with a hydraulic fluid to urge the mandrel  30  in an axial direction marked with arrow  46 , which is directionally opposite to arrow  44 . 
         [0016]    Referring now to  FIG. 1A , the valve assembly  10  is shown in an open position wherein the fluid inlet  22  and the fluid outlet  24  are in fluid communication via a passage  48  in the housing  20 . Applying pressurized hydraulic fluid to the pressure chamber  26   a  slides the mandrel  30  in the axial direction  44  until the mandrel  30  reaches the closed position shown in  FIG. 1B . In  FIG. 1B , the seal  40  and the mandrel  30  form a fluid seal (e.g., liquid-tight seal or gas-tight seal) that prevents fluid communication between the fluid inlet  22  and the fluid outlet  24 . 
         [0017]    Referring to  FIG. 1B , the seal  40  may be a bidirectional sealing device that includes one or more sealing elements that form a flow-blocking barrier between an outer surface  44  of the mandrel  30  and an inner surface  46  of the housing  20 . The seal  40  may be bidirectional in that the seal prevents flow therethrough in either axial direction. The seal  40  surrounds the mandrel  30  and is stationary relative to the housing  20 . For example, the seal  40  may seat on a support  47  of the housing  20 . The support  47  may be a shoulder or ledge that limits axial movement of the seal  40 . The support  47  may be integral with the housing  20  or tubular component of the housing  20 . 
         [0018]    Referring now to  FIG. 2 , there is shown a cross-sectional view of a section of one embodiment of a seal  40  in accordance with the present disclosure. In one arrangement, the seal  40  may include an upper end adapter  48   a,  a first unidirectional seal stack  50   a,  a center adapter  52 , a second unidirectional seal stack  50   b,  and a second end adapter  48   b.  The end adapters  48   a,b  and the center adapter  52  may be formed of a material harder or more rigid than the material of the seal rings  54  so that pressure applied to the end adapters  48   a, b  can be distributed relatively evenly through the seal stacks  50   a,b.    
         [0019]    The unidirectional seal ring stacks  50   a, b  may include one or more cylindrical seal rings  54 . The seal rings  54  may be formed as chevron-type seal rings. As used herein, a chevron seal ring is a pressure responsive sealing element that flexes to form a seal against adjacent surfaces. The chevron shape may defined by two wings  56  that are hinged at an apex  58 . The wings  56  may form an angle less than one-hundred eighty degrees. The seal ring  54  is responsive to the pressure applied on the apex  58  side (i.e., unidirectional). In one embodiment, the seal rings  54  may be “U” or “V” shaped annular elements formed of a material that allows a predetermined amount of flexure when the ring  54  is compressed. Thus, pressure applied to the upper end adapter  48   a  causes the ring(s)  54  to be compressed against the center adapter  52 . This compression causes the ring(s)  54  to expand and compress the tips  60  of the wings  56  to engage and seal against the adjacent surfaces  44 ,  46 . 
         [0020]    It should be appreciated that seal  40  is pressure responsive in that the magnitude of the sealing force (or contact force) at the tips  60  varies directly with the differential pressure across the seal  40 . Thus, as this pressure differential increases, the sealing force at the tips  60  also increases. In the embodiment shown, the seal  40  includes multiple oppositely-oriented rings  54 . The use of multiple rings  54  allows the formation of multiple serially aligned sealing surfaces along the surfaces  44 ,  46 . The opposite orientation of the seal rings  54 , i.e., having the apexes  58  point in opposite directions, enables the seal  40  to be bidirectional. 
         [0021]    The rings  54  may be formed of a material that has a modulus that allows flexure at a prescribed pressure range. In some embodiments, a metal such as spring steel may be used. In other embodiments, non-metals such as elastomeric material may used. In still other embodiments, the seal stacks  50   a, b  may use a combination of two or more materials. For example, seal stacks  50   a, b  may include one or more rings  54  made of metal and one or more rings made of a non-metal. Also, while several rings  54  are shown for each of seal stack  50   a, b , one or more rings may be used. 
         [0022]    Referring to  FIG. 3 , in one non-limiting embodiment, the valve  10  may be used to create or diffuse a differential pressure between a fluid source in a subsurface environment and an environment in a well tool  100 . The fluid source may be fluid in a borehole  102  or a fluid reservoir residing in a formation  108 . The well tool  100  may be a bottomhole drilling assembly, a fluid sampling tool, a coring tool, or any other tool that is configured or performs one or more tasks (e.g., forming the borehole, sampling/testing formation solids or fluids, etc.) in the borehole  102 . A sample from the formation  108  may be retrieved using a packer-type probe  12  that engages a wall of the borehole  102  to isolates the fluid in the formation  108  from the borehole fluid  104 . In other embodiments not shown, one or more annular packers may be used to isolate a zone in the borehole  102 . The isolated borehole zone may fill with a formation fluid. In either case, the valve  10  may be used to convey a fluid sample retrieved from the isolated zone to a sample bottle  110  or other similar receptacle. The well tool  100  may be conveyed via a work string  106 , which may include a rigid carrier (e.g., drill string, casing, liner, etc.) or non-rigid carrier (e.g., wireline, slickline, e-line, etc.). 
         [0023]    Referring now to  FIGS. 1A and 3 , in one mode of use, the well tool  100  may be conveyed into a borehole  102  to retrieve one or more fluid samples. After being appropriately positioned, a hydraulic source (not shown) pressurizes the pressure chamber  26   a  via the pilot inlet  28   a  with a hydraulic fluid to urge the mandrel  30  in an axial direction marked with arrow  44 . This action sets the valve  10  in an open position and allows a retrieved fluid, which may be a liquid, a gas, or a mixture thereof, to flow to the fluid outlet  24  via the fluid inlet  22  and the passage  48 . The retrieved fluid, or fluid “sample,” may be collected in a sample receptacle  110 . It should be appreciated that during the sampling activity, the valve  10  may be considered pressure balanced. That is, the fluid pressure at the fluid inlet  22  is applied to the seal  62  above and the seal  64  below the fluid inlet  22 . This balanced pressure reduces the likelihood that the mandrel  30  will move due to pressure fluctuations. 
         [0024]    To terminate the sampling operation, the hydraulic source (not shown) pressurizes the pressure chamber  26   b  via the pilot inlet  28   b  to urge the mandrel  30  in an axial direction marked with arrow  46 , which sets the valve  10  in the closed position. 
         [0025]    Referring now to  FIGS. 1B and 2 , in the closed position, fluid pressure at the fluid inlet  22  generates a pressure differential across the seal  40 . The differential between the pressure at the fluid source and the interior of the well tool  100  may approach twenty-five thousand PSI. This pressure compresses the seal  40  against the support  47 . Specifically, the upper end adapter  48   a  compresses the spring stack  50   a  against the center adapter  52 . The center adapter  52  communicates this pressure to the seal stack  50   b.  This compression causes the ring(s)  54  to expand and compress the tips  60  of the wings  56  to engage and seal against an adjacent surfaces  44 ,  46 . It should be appreciated that an increase in pressure causes a corresponding increase in the sealing force at the contact between the wings  56  and the adjacent surfaces  44 ,  46 . The resulting seal may be a gas-tight seal. Moreover, in instances where multiple seal rings  54  are used, multiple independent sealing contacts are formed. It should also be appreciated that this gas-tight seal is obtained without applying a sealing agent at the contacting surfaces (e.g., grease). 
         [0026]    It should be appreciated that when the seal  40  isolates an inflowing fluid sample from surrounding fluid during retrieval, the seal  40  prevents the inflowing fluid from leaking out of the passage  48 . When preserving a retrieved fluid sample as the tool is being returned to the surface, the seal  40  prevents the fluid sample from leaking into the passage  48 . Thus, the seal  40  has bidirectional sealing capability. However, it should be understood that if a separate seal is used to prevent either fluid leaking into or out of the passage  48 , then the seal  40  does not need to be bidirectional and only one seal stack may be used. 
         [0027]    Also, in certain embodiments, an actuator  75  may be used to allow pressurized fluid to escape or bleed from the pressure chamber  26   b.  The actuator  75  may be used to manually close the valve  10 . For instance, if the valve  10  is in the open position shown in  FIG. 1A , the actuator  75  may be partially or completely removed to allow hydraulic fluid to escape, which would allow the valve  10  to shift to the closed position in  FIG. 1B . In some embodiments, the actuator  75  may be a threaded body that is screwed into the housing  20 . 
         [0028]    While the foregoing disclosure is directed to the one mode embodiments of the disclosure, various modifications will be apparent to those skilled in the art. For example, while a hydraulic source is shown for moving the mandrel, an electric motor may also be used to translate the mandrel. Also, in certain embodiments, a unidirectional seal may be used to form an adequate seal. It is intended that all variations be embraced by the foregoing disclosure.