Abstract:
A downhole circulating valve includes a generally tubular outer housing having an axially extending internal passageway including an internal seat and at least one generally radially extending opening formed through the housing intersecting the internal seat. A valve element is rotatably disposed within the internal passageway. The valve element has an axially extending internal bore and a head portion disposed at least partially within the internal seat. The head portion includes at least one generally radially extending seal element. The valve element has a first position relative to the housing, wherein the seal element is not aligned with the opening, thereby allowing fluid communication between the opening and the internal passageway. The valve element has a second position relative to the housing, wherein the seal element is aligned with the opening and wherein the seal element forms a metal-to-metal seal with the internal seat, thereby preventing fluid communication between the opening and the internal passageway.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit under 35 U.S.C. §119 of the filing date of International Application No. PCT/US2012/031956, filed Apr. 3, 2012. The entire disclosure of this prior application is incorporated herein by this reference. 
     TECHNICAL FIELD OF THE INVENTION 
     This invention relates, in general, to equipment utilized in conjunction with operations performed in subterranean wells and, in particular, to a downhole circulating valve having a metal-to-metal seal in its non-circulating configuration and method for operating the downhole circulating valve between circulating and non-circulating configurations. 
     BACKGROUND OF THE INVENTION 
     Without limiting the scope of the present invention, its background will be described with reference to operations performed in a subterranean well that traverses a fluid-bearing subterranean formation, as an example. Subterranean wellbores are generally filled with fluids that extend from the lower end of the wellbore to the earth&#39;s surface. During drilling and completions operations, a weighted column of fluid is usually present adjacent to each of the fluid-bearing formations intersected by the wellbore, so that the column of fluid may exert hydrostatic pressure on the formations sufficient to prevent uncontrolled flow of fluid from the formations into the wellbore, which uncontrolled flow of fluid could result in a blowout. 
     In order to transport fluid, tools, instruments and the like within the wellbore, it is common practice to utilize a tubular string, such as drill pipe or production tubing, to which tools and instruments may be attached and within which fluid may be flowed and tools and instruments may be conveyed. When such a tubular string is disposed within the wellbore, the fluid column within the wellbore may be effectively divided into multiple portions. For example, a first fluid column may be contained in an annulus defined by the area separating the outside surface of the tubular string from the inside surface of the wellbore or casing string. At the same time, a second fluid column may be contained within the interior of the tubular string. In such a configuration, tools, instruments and the like may be transported within the wellbore attached to or within the tubular string without disturbing the relationship between the fluid column in the annulus and the fluid-bearing formations intersected by the wellbore. 
     After completing the well, it is typically desirable to remove the weighted column of fluid from both the interior of the tubular string, if present, and the annulus above the uppermost packer. This may be achieved through the use of a circulating valve disposed within in the tubular string, which has a primary purpose of selectively permitting fluid flow between the interior of the tubular string and the annulus. For example, when it is desired to remove the weighted column of fluid from the annulus, a lighter fluid may be pumped from the earth&#39;s surface down through the tubular string and radially outwardly from the tubular string through the circulating valve into the annulus and then back to the earth&#39;s surface up through the annulus. Typically, such tubing conveyed circulating valves have a sliding sleeve that may be longitudinally shifted between circulating and non-circulating positions using wireline or slickline techniques. In the non-circulating position, conventional circulating valves typically utilize resilient materials such as elastomers for sealing between movable metal parts to prevent fluid communication between the interior of the tubular string and the annulus. 
     It has been found, however, that resilient sealing materials may deteriorate due to the harsh chemical, physical and thermal environment downhole. When such deterioration occurs, the seals may fail to prevent fluid communication between the interior of the tubular string and the annulus when a conventional circulating valve is in its non-circulating configuration. Accordingly, a need has arisen for an improved circulating valve that is operable to selectively permit fluid flow between the interior of the tubular string and the annulus. In addition, a need has arisen for such an improved circulating valve that does not rely on resilient sealing materials to prevent fluid communication between the interior of the tubular string and the annulus when the circulating valve is in its non-circulating configuration. 
     SUMMARY OF THE INVENTION 
     The present invention disclosed herein comprises an improved circulating valve that is operable to selectively permit fluid flow between the interior of a tubular string and the annulus between the tubular string and the wellbore. In addition, the improved circulating valve of the present invention does not rely on resilient sealing materials to prevent fluid communication between the interior of the tubular string and the annulus when the circulating valve is in its non-circulating configuration but instead utilizes a metal-to-metal seal to provide a long lasting, high pressure seal. 
     In one aspect, the present invention is directed to a downhole circulating valve. The downhole circulating valve has a generally tubular outer housing having an axially extending internal passageway including an internal seat and at least one generally radially extending opening formed through the housing intersecting the internal seat. A valve element is rotatably disposed within the internal passageway. The valve element has an axially extending internal bore and a head portion disposed at least partially within the internal seat. The head portion includes at least one generally radially extending seal element. The valve element has a first position relative to the housing wherein the seal element is not aligned with the opening, thereby allowing fluid communication between the opening and the internal passageway. The valve element has a second position relative to the housing wherein the seal element is aligned with the opening and wherein the seal element forms a metal-to-metal seal with the internal seat, thereby preventing fluid communication between the opening and the internal passageway. 
     In one embodiment, the internal seat may have a spherical segment having a first radius. In this embodiment, the at least one generally radially extending opening may extend in the direction of the first radius. In some embodiments, an outer surface of the head portion may have a spherical segment having a second radius. In addition, the head portion may include at least one generally radially extending port that may extend in the direction of the second radius. The at least one generally radially extending seal element may also extend in the direction of the second radius. In certain embodiments, the first radius and the second radius may be sized to enable spherical mating of the at least one generally radially extending seal element and the internal seat. In such embodiments, the head portion may translate toward the internal seat when the valve element is operated from the first position to the second position to form the metal-to-metal seal. In one embodiment, the at least one generally radially extending seal element may include one or more seal rings each having a circular cross section. 
     In one embodiment, the housing may include a plurality of circumferentially distributed generally radially extending openings formed through the housing intersecting the internal seat. In this embodiment, the head portion may include a plurality of circumferentially distributed generally radially extending ports and a plurality of circumferentially distributed generally radially extending seal elements that are circumferentially offset from the ports such that in the first position, the ports are in fluid communication with the openings and, in the second position, each of the seal elements is aligned with one of the openings and forms a metal-to-metal seal with the internal seat. 
     In another aspect, the present invention is directed to a downhole circulating valve. The downhole circulating valve includes a generally tubular outer housing having an axially extending internal passageway including a spherical segment internal seat having a first radius and at least one generally radially extending opening formed through the housing intersecting the internal seat. A valve element is rotatably disposed within the internal passageway. The valve element has an axially extending internal bore and a head portion having an outer surface including a spherical segment with a second radius. The head portion is translatable relative to and disposed at least partially within the internal seat. The head portion includes at least one generally radially extending port and at least one generally radially extending seal element that is circumferentially offset from the port. The valve element has a first position relative to the housing wherein the port is in fluid communication with the opening and a second position relative to the housing wherein the seal element is aligned with the opening, wherein the seal element forms a metal-to-metal seal with the internal seat, wherein the first radius and the second radius are sized to enable spherical mating of the at least one generally radially extending seal element and the internal seat and wherein the head portion translates toward the internal seat when the valve element is operated from the first position to the second position. 
     In a further aspect, the present invention is directed to a downhole circulating system. The system includes a downhole power unit having an engagement assembly and a rotatable shaft. The system also includes a circulating valve having a generally tubular outer housing with an axially extending internal passageway including a profile, an internal seat and at least one generally radially extending opening formed through the housing intersecting the internal seat. A valve element is rotatably disposed within the internal passageway. The valve element has an axially extending internal bore with a profile and a head portion disposed at least partially within the internal seat. The head portion includes at least one generally radially extending seal element. A first portion of the engagement assembly is operably associated with the profile of the housing and a second portion of the engagement assembly is operably associated with the profile of the valve element such that when the downhole power unit is activated and the rotatable shaft is rotated, the valve element is rotatable between a first position relative to the housing wherein the seal element is not aligned with the opening and a second position relative to the housing wherein the seal element is aligned with the opening and wherein the seal element forms a metal-to-metal seal with the internal seat. 
     In an additional aspect, the present invention is directed to a method for operating a downhole circulating valve. The method includes providing a circulating valve having a generally tubular outer housing with an axially extending internal passageway including an internal seat and at least one generally radially extending opening formed through the housing intersecting the internal seat and a valve element rotatably disposed within the internal passageway, the valve element having an axially extending internal bore and a head portion disposed at least partially within the internal seat, the head portion including at least one seal element; running the circulating valve into a wellbore on a tubular string; running a rotating tool into the tubular string and engaging the circulating valve; and activating the rotating tool to rotate the valve element between a first position relative to the housing wherein the at least one seal element is not aligned with the at least one opening and a second position relative to the housing wherein the at least one seal element is aligned with the at least one opening and wherein the at least one seal element forms a metal-to-metal seal with the internal seat. 
     The method may also include running a downhole power unit having a rotatable shaft into the tubular string and engaging a profile of the housing and a profile of the valve element with the downhole power unit; activating an electric motor of the downhole power unit to impart rotary motion to the rotatable shaft; spherical mating the seal element and the internal seat by translating the head portion toward the internal seat and/or creating a metal-to-metal seal between at least one seal ring of the seal element and the internal seat. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the features and advantages of the present invention, reference is now made to the detailed description of the invention along with the accompanying figures in which corresponding numerals in the different figures refer to corresponding parts and in which: 
         FIG. 1  is a schematic illustration of a well system operating a downhole circulating system according to an embodiment of the present invention; 
         FIGS. 2A-2E  are cross sectional views of successive axial sections of a downhole circulating system according to an embodiment of the present invention; 
         FIG. 2F  is a cross sectional view of the downhole circulating system of  FIGS. 2A-2E  taken along line  2 F- 2 F; 
         FIG. 3  is a cross sectional view of a downhole circulating valve according to an embodiment of the present invention in its circulating configuration; 
         FIG. 4  is a cross sectional view of a downhole circulating valve according to an embodiment of the present invention in its non-circulating configuration; 
         FIG. 5  is a side view of a head portion of a valve element of a downhole circulating valve according to an embodiment of the present invention; 
         FIG. 6  is a perspective view of a head portion of a valve element of a downhole circulating valve according to an embodiment of the present invention; and 
         FIG. 7  is an enlarged view of a metal-to-metal seal formed within a downhole circulating valve in its non-circulating configuration according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     While the making and using of various embodiments of the present invention are discussed in detail below, it should be appreciated that the present invention provides many applicable inventive concepts, which can be embodied in a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative of specific ways to make and use the invention, and do not delimit the scope of the present invention. 
     Referring initially to  FIG. 1 , therein is depicted a well system including a downhole circulating system embodying principles of the present invention that is schematically illustrated and generally designated  10 . In the illustrated embodiment, a wellbore  12  extends through the various earth strata. Wellbore  12  has a substantially vertical section  14 , the upper portion of which has cemented therein a casing string  16 . Wellbore  12  also has a substantially horizontal section  18  that extends through a hydrocarbon bearing subterranean formation  20 . As illustrated, substantially horizontal section  18  of wellbore  12  is open hole. 
     Positioned within wellbore  12  and extending from the surface is a tubing string  22 . Tubing string  22  provides a conduit for formation fluids to travel from formation  20  to the surface and for injection fluids to travel from the surface to formation  20 . At its lower end, tubing string  22  is coupled to a completions string that has been installed in wellbore  12  and divides the completion interval into various production intervals adjacent to formation  20 . The completion string includes a plurality of sand control screens  24 , each of which is positioned between a pair of annular barriers depicted as packers  26  that provides a fluid seal between the completion string and wellbore  12 , thereby defining the production intervals. Tubing string  22  may include a variety of tools such as packer  28  that provides a seal between tubing string  22  and casing string  16 . An annulus  30  is defined between tubing string  22  and casing string  16  above packer  28 . As discussed above, during drilling and completions operations, a weighted column of fluid is usually present in the wellbore  12  to exert hydrostatic pressure on formation  20  sufficient to prevent uncontrolled flow of fluid from formation  20  into wellbore  12 . To enable production, however, the weighted column of fluid must be removed from wellbore  12 . In the illustrated embodiment, a circulating valve  32  is positioned within tubing string  22  above packer  28  and may be operated via a slickline or wireline deployed rotating tool depicted as downhole power unit  34 . Circulating valve  32  serves the primary purpose of selectively permitting fluid flow between the interior of tubing string  22  and annulus  30 . 
     For example, when it is desired to remove the weighted column of fluid from wellbore  12 , downhole power unit  34  may be deployed via wireline  36  to engage with circulating valve  32 . Typically, circulating valve  32  is initially run downhole in its non-circulating configuration to prevent fluid flow between the interior of tubing string  22  and annulus  30 . Once engaged, downhole power unit  34  may be activated to operate circulating valve  32  from its non-circulating configuration to its circulating configuration. Thereafter, a lighter fluid may be pumped from the earth&#39;s surface down through tubing string  22  and radially outwardly from tubing string  22  through circulating valve  32  into annulus  30  and then back to the earth&#39;s surface up through annulus  30 . After the weighted column of fluid is removed, downhole power unit  34  may be activated to operate circulating valve  32  from its circulating configuration to its non-circulating configuration. In the present invention, when circulating valve  32  is in its non-circulating configuration, one or more metal-to-metal seals prevent fluid communication between the interior of tubing string  22  and annulus  30 . 
     Even though  FIG. 1  depicts the circulating valve of the present invention in a cased hole environment, it should be understood by those skilled in the art that the present invention is equally well suited for use in an open hole well. In addition, even though  FIG. 1  depicts the circulating valve of the present invention in a vertical section of the wellbore, it should be understood by those skilled in the art that the present invention is equally well suited for use in wells having other directional configurations including horizontal wells, deviated wells, slanted wells, multilateral wells and the like. Accordingly, it should be understood by those skilled in the art that the use of directional terms such as above, below, upper, lower, upward, downward, left, right, uphole, downhole and the like are used in relation to the illustrative embodiments as they are depicted in the figures, the upward direction being toward the top of the corresponding figure and the downward direction being toward the bottom of the corresponding figure, the uphole direction being toward the surface of the well and the downhole direction being toward the toe of the well. 
     Referring next to  FIGS. 2A-2E , therein is depicted successive axial sections of a downhole circulating system embodying principles of the present invention that is representatively illustrated and generally designated  100 . System  100  includes a rotating tool depicted as downhole power unit  102  and a circulating valve  104  that may be deployed in a well system as part of the tubing string as described above. Downhole power unit  102  includes a housing assembly  106  that comprises suitably shaped and connected generally tubular housing members. An upper portion of housing assembly  106  includes an appropriate mechanism to facilitate coupling of housing  106  to a conveyance such as a wireline, slickline, electric line, coiled tubing, jointed tubing or the like. 
     In the illustrated embodiment, downhole power unit  102  includes a self-contained power source, eliminating the need for power to be supplied from an exterior source, such as a source at the surface, however, in other embodiments, power may be provided to downhole power unit  102  from the surface via a wired connection. A preferred power source comprises a battery assembly  108  which may include a plurality of batteries such as alkaline batteries, lithium batteries or the like. Downhole power unit  102  also has a force generating and transmitting assembly  110  that preferably includes a direct current electric motor and a gearbox. The electric motor may be of any suitable type. One example is a motor operating at 7500 revolutions per minute in unloaded condition, and operating at approximately 5000 rpm in a loaded condition, and having a horsepower rating of approximately 1/30th of a horsepower. In this implementation, the electric motor may be coupled through a gearbox, which provides approximately 5000:1 gear reduction to a sleeve assembly  112 , which is in turn coupled to a rotatable shaft  114 . Downhole power unit  102  may include a variety of sensors and controllers that are operable to activate and deactivate downhole power unit  102  including, but not limited to, a microcontroller, a pressure-sensitive switch, an accelerometer, a geophone or the like. Alternatively or additionally, downhole power unit  102  may be controlled from the surface via wired or wireless communications. 
     At its lower end, housing assembly  106  includes an engagement assembly  116 . In the illustrated embodiment, engagement assembly  116  includes a set of locating keys  118 , a set of anti-rotation keys  120  and a set of torque keys  122 . Preferably, anti-rotation keys  120  and torque keys  122  are rotatable relative to locating keys  118 . In addition, torque keys  122  are rotatable relative to anti-rotation keys  120 . Torque keys  122  are operably associated with rotatable shaft  114  such that when rotatable shaft  114  is rotated, torque keys  122  are rotated therewith. 
     Referring additionally now to  FIGS. 3 and 4 , circulating valve  104  will now be described. Circulating valve  104  has a generally tubular outer housing  130  including, in the illustrated embodiment, an upper housing section  132  and a lower housing section  134  that are threadably coupled together. Housing  130  defines an axially extending internal passageway  136 . Upper housing section  132  includes a locating profile  138 . Upper housing section  132  also includes an internal seat depicted as a spherical segment internal seat  140  having a radius R 1 , as best seen in  FIG. 3 . Upper housing section  132  further includes four generally radially extending openings  142  (only two such openings being visible in the figures) formed through upper housing section  132  intersecting internal seat  140 . Preferably, openings  142  radially extend through upper housing section  132  in the direction of radius R 1 . Even though upper housing section  132  has been described as having a particular number of openings  142 , other numbers of openings both greater than four and less than four including one opening could alternatively be formed through upper housing section  132  without departing from the principles of the present invention. Lower housing section  134  includes an anti-rotation profile depicted as plurality of circumferentially distributed slots  144  and a locating profile  146 . 
     Circulating valve  104  includes a valve element  148 . In the illustrated embodiment, valve element  148  includes a lower valve section  150 , an upper valve section  152  and a head portion  154 . Lower valve section  150  is threadably coupled to upper housing section  132  and is secured against rotation relative to upper housing section  132  by one or more set screws  156 . Upper valve section  152  is also threadably coupled to upper housing section  132  but is free to rotate relative to upper housing section  132  between two stopping points as described below. Upper valve section  152  includes a rotation profile depicted as plurality of circumferentially distributed slots  158 . Head portion  154  is threadably coupled to upper valve section  152  and is secured against rotation relative to upper valve section  152  by one or more set screws  160 . As such, upper valve section  152  and head portion  154  are operable to rotate together relative to upper housing section  132 . In addition, due to the threaded engagement between upper valve section  152  and upper housing section  132 , rotation of upper valve section  152  and head portion  154  relative to upper housing section  132  causes upper valve section  152  and head portion  154  to translate longitudinally relative to upper housing section  132 . The extent of downward longitudinally travels of upper valve section  152  and head portion  154  is limited by contact between an upper valve section  152  and lower valve section  150 . The extent of upward longitudinally travel of upper valve section  152  and head portion  154  is limited by contact between head portion  154  and internal seat  140 , as more fully described below. 
     Valve element  148  has an axially extending internal bore  162 . Head portion  154  has an outer surface including a spherical segment  164  with a radius R 2 , as best seen in  FIG. 3 . Head portion  154  includes four generally radially extending ports  166  (only some of the ports being visible in the figures). Preferably, ports  166  radially extend through head portion  154  in the direction of radius R 2 . Even though head portion  154  has been described as having a particular number of ports  166 , other numbers of ports both greater than four and less than four including one port could alternatively be formed through head portion  154  without departing from the principles of the present invention. Also, even though head portion  154  has been described as having the same number of ports  166  as upper housing section  132  has openings  142 , this is not required by the present invention. 
     As best seen in  FIGS. 5-7 , head portion  154  also includes four generally radially extending seal elements  168  (only some of the seal elements being visible in the figures). Preferably, seal elements  168  radially extend from head portion  154  in the direction of radius R 2 . Even though head portion  154  has been described as having a particular number of seal elements  168 , other numbers of seal elements both greater than four and less than four including one seal element could alternatively be formed on head portion  154  without departing from the principles of the present invention, however, the number of seal elements  168  should equal or exceed the number of openings  142  through upper housing section  132 . As illustrated, ports  166  and seal elements  168  are circumferentially distributed about head portion  154  at a uniform interval of 45 degrees with a port  166  positioned between each pair of seal elements  168  and a seal element  168  positioned between each pair of ports  166 . 
     In the illustrated embodiment, seal elements  168  include a pair of concentric seal rings  170 ,  172 , each having a circular cross section. Preferably, seal rings  170 ,  172  radially extend from head portion  154  in the direction of radius R 2 . As such, the outer surfaces of seal rings  170 ,  172  lie in a spherical segment that has a radius that enables spherical mating between the outer surfaces of seal rings  170 ,  172  and internal seat  140  when circulating valve  104  is in its non-circulating configuration. 
     In operation, downhole power unit  102  is adapted to cooperate with circulating valve  104  to enable and disable fluid circulation therethrough. Specifically, after circulating valve  104  has been run downhole as part of a tubing string and it is desired to circulate fluid between the interior of the tubing string and the annulus surrounding the tubing string, downhole power unit  102  is run downhole on a suitable conveyance such as a wireline. Upon reaching the desired depth downhole, downhole power unit  102  engages circulating valve  104 . Specifically, engagement assembly  116  interacts with circulating valve  104 . First, locating keys  118  engage locating profiles  146  of lower housing section  134 . At this point, anti-rotation keys  120  should be axially aligned with anti-rotation profile  144  and torque keys  122  should be axially aligned with rotation profile  158 . Slight rotation of rotatable shaft  114  may now be required to engage anti-rotation keys  120  with anti-rotation profile  144  and torque keys  122  with rotation profile  158 , as best seen in  FIG. 2F . Thereafter, activation of downhole power unit  102  to rotate rotatable shaft  114  will cause upper valve section  152  and head portion  154  to rotate together relative to upper housing section  132 . 
     For example, to operate circulating valve  104  from the non-circulating configuration ( FIG. 4 ) to the circulating configuration ( FIG. 3 ), downhole power unit  102  is activated to rotate in a first direction which rotates upper valve section  152  and head portion  154  relative to upper housing section  132  such that seal elements  168  are rotationally and translationally shifted away from openings  142  and such that ports  166  are substantially aligned with openings  142  enabling fluid communication through circulating valve  104 . To operate circulating valve  104  from the circulating configuration ( FIG. 3 ) to the non-circulating configuration ( FIG. 4 ), downhole power unit  102  is activated to rotate in a second direction which rotates upper valve section  152  and head portion  154  relative to upper housing section  132  such that seal elements  168  are rotationally and translationally shifted toward openings  142  until the outer surfaces of seal rings  170 ,  172  are spherically mated with internal seat  140  to create a metal-to-metal seal around each opening  142  that prevents fluid communication through circulating valve  104 . This process can be repeated as desired to operate circulating valve  104  between its circulating and non-circulating configurations. When desired, upward jarring will release downhole power unit  102  from circulating valve  104  and downhole power unit  102  can be retrieved to the surface. 
     While this invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the illustrative embodiments as well as other embodiments of the invention will be apparent to persons skilled in the art upon reference to the description. It is, therefore, intended that the appended claims encompass any such modifications or embodiments.