Patent Publication Number: US-7594542-B2

Title: Alternate path indexing device

Description:
FIELD OF THE INVENTION 
   The present invention relates to the field of downhole well tools and more specifically to a mechanical indexer that facilitates movement of a valve from a current position to a preceding position in a predetermined sequence of valve positions, without requiring that all of the intervening valve positions in the predetermined sequence be actuated. 
   BACKGROUND 
   The economic climate of the petroleum industry demands that oil companies continually improve their recovery systems to produce oil and gas more efficiently and economically from sources that are continually more difficult to exploit and without increasing the cost to the consumer. One successful technique currently employed is the drilling of horizontal, deviated, and multilateral wells, in which a number of deviated wells are drilled from a main borehole. In such wells, as well as in standard vertical or near-vertical wells, the wellbore may pass through various hydrocarbon bearing zones or may extend through a single zone for a long distance. 
   One manner of increasing the production of such wells is to perforate the well production casing or tubing in a number of different locations, either in the same hydrocarbon bearing zone or in different hydrocarbon bearing ones, and thereby increase the flow of hydrocarbons into the well. However, this manner of production enhancement also raises reservoir management concerns and the need to control the production flow rate at each of the production zones. For example, in a well producing from a number of separate zones, or lateral branches in a multilateral well, in which one zone has a higher pressure than another zone, the higher pressure zone may produce into the lower pressure zone rather than to the surface. Similarly, in a horizontal well that extends through a single zone, perforations near the “heel” of the well (nearer the surface) may begin to produce water before those perforations near the “toe” of the well. The production of water near the heel reduces the overall production from the well. Likewise, gas coning may reduce the overall production from the well. 
   A manner of alleviating such problems may be to insert a production tubing into the well, isolate each of the perforations or lateral branches with packers, and control the flow of fluids into or through the tubing. Typical flow control systems provide for either on or off flow control with no provision for throttling of the flow. To fully control the reservoir and flow as needed to alleviate the above-described problems, the flow must be throttled. 
   A number of devices have been developed or suggested to provide this throttling although each has certain drawbacks. Note that throttling may also be desired in wells having a single perforated production zone. Specifically, such prior devices are typically either wireline retrievable valves, such as those that are set within the side pocket of a mandrel or tubing retrievable valves that are affixed to the tubing. 
   A prior method of operating these downhole flow control devices is with a mechanical indexer (some times referred to as a J-slot device). Convention mechanical indexers include an indexer pattern that defines a predetermined sequence of incremental positions of the valve at and between the open and closed position. Thus, to operate the valve to a position that precedes the current valve position in the predetermined sequence, the valve must be cycled through the predetermined sequence to reach the preceding position. The requirement of having to actuate through the predetermined sequence to reach a desired valve position can result in well or formation damage. 
   Therefore, it is a desire to provide a mechanical indexer and system that facilitates actuating a valve from a current position in a predetermined sequence of valve positions, to a previous cycle position without having to actuate through all of the intervening subsequent valve positions in the predetermined sequence. It is a further desire to provide an indexing device that that has a primary path for actuating a valve through a predetermined sequence of incremental positions at and between open and closed positions and one or more alternative paths to actuate the valve from a current position to a preceding position in the predetermined sequence of incremental positions. 
   SUMMARY OF THE INVENTION 
   In view of the foregoing and other considerations, the present invention relates to shifting valves through incremental positions at and between open and closed. More specifically the present invention relates to a mechanical indexing device and method for shifting a valve to a preceding position in a valve shifting sequence. 
   Accordingly, an embodiment of a method of shifting a valve between a plurality of flow condition positions, includes the steps of providing a mechanical indexer device in operational connection with a valve, the indexer device including a primary path defining a sequence through a plurality of valve positions at and between open and closed and a detent moveable along the primary path; providing at least one alternate path from a point along the primary path to a preceding position on the primary path along the sequence; shifting the valve to a subsequent position in the sequence; and shifting the valve to the preceding position in the sequence. 
   An embodiment of a choke assembly including a mechanical indexer device in operational connection with a valve, the indexer device including an indexing pattern and a detent moveable along the indexing pattern, the indexing pattern having a primary path defining a sequence through a plurality of valve positions at and between open and closed and at least one alternate path from a point along the primary path to a preceding position on the primary path along the sequence. 
   The choke assembly may further include an actuator cooperable with the indexing device, the actuator transmitting a primary hydraulic signal to shift the valve to the subsequent position and transmitting an alternate hydraulic signal to shift the valve to the preceding position. In one embodiment the primary hydraulic signal has a longer duration than the alternate hydraulic signal. In another embodiment the primary hydraulic signal is a pressure greater than the alternate hydraulic signal. 
   The foregoing has outlined the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other features and aspects of the present invention will be best understood with reference to the following detailed description of a specific embodiment of the invention, when read in conjunction with the accompanying drawings, wherein: 
       FIG. 1  is a schematic of an embodiment of an alternate path indexing device of the present invention; 
       FIG. 2A-2C  are cross-sectional views of an embodiment of an choke assembly and alternate path indexing device of the present invention; 
       FIG. 3  is a graphical, planar view of a prior conventional indexer slot pattern; and 
       FIG. 4  is a graphical, planar view of an embodiment of alternate path indexer slot pattern of the present invention 
   

   DETAILED DESCRIPTION 
   Refer now to the drawings wherein depicted elements are not necessarily shown to scale and wherein like or similar elements are designated by the same reference numeral through the several views. 
   As used herein, the terms “up” and “down”; “upper” and “lower”; and other like terms indicating relative positions to a given point or element are utilized to more clearly describe some elements of the embodiments of the invention. Commonly, these terms relate to a reference point as the surface from which drlling operations are initiated as being the top point and the total depth of the well being the lowest point. 
   Generally, some embodiments of the invention provide a choke system or valve assembly that includes a valve adapted to choke the flow through one or more orifices of the valve. A valve actuator operably attached to the valve is able to position the valve at one or more incremental positions between an open position and a closed position. The valve actuator defines a predefined shifting sequence to provide the incremental positions of the valve and one or more alternate paths to shift the valve from its current position to a preceding position in the predefined sequence. The change in flow area as the valve is actuated through the incremental positions varies so that predetermined changes in flow condition can be provided. As used here, flow condition may refer to pressure drop across the valve and/or flow rate through an orifice in the valve. 
   An indexing mechanism is connected to the actuator to restrict motion of the valve actuator to provide the incremental positions between the open and closed positions. The indexing mechanism includes a first indexer member defining a plurality of elongated, spaced, interconnected slots, grooves or elevations and a second indexer member having an indexer detent attached thereto. The indexer detent is adapted to mate with and move within the plurality of slots. The first and second indexer members are adapted for movement relative to one another, with the plurality of slots and the indexer detent adapted to cooperatively restrict the relative movement of the first and second indexer members. 
   The interconnected slots on the first indexer member form an indexing pattern. The indexing pattern includes a primary path that extends from an initial position through a predetermined sequence of intermediate positions back to the initial position. Each of the positions corresponds to a choke position of the valve. In one example, the initial position corresponds to the valve being closed and each subsequent intermediate position corresponding to the valve being opened more than the preceding positions. The indexing mechanism and pattern of the present invention further includes one or more alternate paths for the indexer detent. In one embodiment, alternate paths extend between the initial position and points between adjacent intermediate positions. These alternative paths address the long felt needs of operators to: (i) reduce the number of actuation steps and time of actuation to cycle through the pattern to the initial position; (ii) close the valve from any intermediate position as quickly as possible, for example to control the well; and (iii) to avoid opening the valve further if it is necessary to reduce the choke, for example wherein additional opening of the valve may potentially damage the formation or allow excess cross-flow between zones. 
   The indexer device includes an indexer sleeve defining an alternate indexing pattern about its circumference. The indexer sleeve is rotatable about a first mandrel segment of an operator mandrel in the valve actuator. The first mandrel segment is actuatable by fluid pressure to move up and down, which causes incremental rotation of the indexer sleeve about the first mandrel segment to shift the valve to the incremental positions. 
   Because there may be two different outcomes when starting from an intermediate indexer position, moving to the subsequent position or following the alternate path back to the initial position, various indexer control options and systems may be utilized. In some embodiments duration of the actuation signal may be varied such that reversal of the direction of movement of the detent relative to the groove determines movement to the subsequent position in the predetermined sequence or into an alternate path and to a preceding position in the sequence. In some embodiments, different actuation signal levels may be utilized to actuate to a subsequent pattern position or along an alternate path to a preceding pattern position. For example, two different pressure levels may be utilized. In some embodiments, sensor may be utilized to indicate the travel of the indexer relative to a slot. 
   Referring to  FIG. 1 , in one embodiment, a tubing section  14  extends inside a wellbore to a zone  16  (which may be production zone or an injection zone, for example) in a formation. The wellbore  10  is lined with casing  12 , perforated to allow fluids to flow from, or be injected into, zone  16 . A choke system or valve assembly  18  according to one embodiment is attached to the lower end of tubing section  14 . The choke system  18  at its lower end may also be attached to another tubing section  20 . Fluid to be produced from, or injected into, zone  16  passes through the bore  28  of the choke system and a bore (not shown) in tubing  14 . 
   The choke system  18  includes a valve  22  that may be incrementally set at and between open and closed positions to control fluid flow between bore  28  of the choke system and the outside of valve  22 . Between the open and closed positions, valve  22  may be set at one or more intermediate, incremental positions by a valve actuator  26  and indexing mechanism  24 . Further indexing mechanism  24  permits valve  22  to be returned to the initial incremental position or to a preceding incremental position without having to actuate through all of the intervening positions of the predetermined sequence. 
   Indexing mechanism  24  provides substantially precise control of the order of the incremental steps made by valve actuator  26  in opening valve  22 . This prevents surges from occurring through valve  22  due to having to open it more to move to the closed incremental step or to a preceding choked position. Such surges of flow from the surrounding formation into valve  22  may cause damage to the formation. Further, surges in fluid flow may cause sand or other contaminants to be produced from the surrounding formation, which is undesirable. This alternative incremental position pattern further facilitates quicker actuation of valve  22  in response to well conditions. 
   Referring to  FIGS. 2A-2C , an embodiment of valve actuator  26  of choke system  18  includes an operator mandrel  101  having a first mandrel segment  114  ( FIG. 2A ) and a second mandrel segment  152  ( FIG. 2B ). First mandrel segment  114  is actuatable up and down by fluid pressure applied down a control conduit  122 , which may extend from the surface or a region in the well (e.g., casing-tubing annulus). The fluid pressure applied down conduit  122  flows into an activation chamber  124 . Fluid pressure in activation chamber  124  is applied against an upper surface  125  of a protruding portion  126  of first mandrel segment  114 . A lower surface  127  of protruding portion  126  is exposed to a balance line chamber  128 . Activation chamber  124  is isolated from balance line chamber  128  by a seal  130 . Fluid pressure in balance line chamber  128  is provided down a conduit  132 . In one embodiment, balance chamber  128  may be filled with oil. Differential pressure created across protruding portion  126  of first mandrel segment  114  causes first mandrel segment  114  to move. 
   In accordance with some embodiments, as illustrated in  FIG. 2B , indexing mechanism  24  is separated into two portions: an indexer device  100  and a positioner device  102 . It should be recognized that indexer mechanism  24  does not include positioner device  102  in embodiments of the invention. Indexer device  100  includes an indexer finger  106  that is fixably mounted with respect to housing  104  of choke system  18 . At its upper end, indexer finger  106  includes an indexer detent  108  that is adapted to run along a pattern of elongated, spaced, and interconnected slots  120  (shown in greater detail in  FIG. 4 ) formed on the outer surface about the circumference of a rotatable indexer sleeve  110  that is part of indexer device  100 . Indexer sleeve  110  is rotatably mounted about first mandrel segment  114  of operator mandrel  101  by ball bearings  112  connected at the upper and lower ends of indexer sleeve  110 . In one embodiment, oil or some other suitable fluid is contained in a chamber  129  to maintain lubrication of ball bearings  112 . 
   Indexer sleeve  110  is made to rotate by movement of first mandrel segment  114  in response to application of fluid pressure. Since indexer finger  106  is fixably mounted with respect to housing  104 , movement of first mandrel segment  114  causes indexer sleeve  110  to rotate to allow indexer detent  108  to run along indexing slots  120 . The arrangement of slots  120  allows first mandrel segment  114  to incrementally actuate or shift in response to applied fluid pressure cycles in fluid conduit  122 . By actuating first mandrel segment  114  along the pattern of slots  120  an operator may actuate valve  22  through subsequent valve positions in the predetermined sequence or actuate valve  22  to a preceding valve position in the sequence without having to shift valve  22  through all of the intervening positions in the predetermined sequence of positions. 
   The lower end of first mandrel segment  114  is threadably connected to an actuator member  142  having an outwardly formed flange portion  144 . Flange portion  144  extends radially by a sufficient amount so that an outer portion of its upper surface is able to contact a shoulder  146  formed in the inner wall of a connector sleeve  148 . Connector sleeve  148  at its lower end is threadably connected to second mandrel segment  152 . Downward movement of first mandrel segment  114  causes actuator member  142  to move downwardly so that flange portion  144  traverses a gap  150 . The bottom end of actuator member  142  traverses a distance D 1  to abut an upper surface of second mandrel segment  152  so that first mandrel segment  114  can push against second mandrel segment  152  to cause downward movement of second mandrel segment  152 . Second mandrel segment  152  is moved downwardly by predetermined distances to position second mandrel segment  152  with respect to increments defined by positioner device  102  and slot pattern  120 . Removal of the applied pressure in activation chamber  124  allows first mandrel segment  114  to move upwardly. Gap  150  provides a lost motion separation of the first and second mandrel segments so that upward movement of first mandrel segment  114  does not cause movement of second mandrel segment  152  until flange portion  144  has traveled upwardly across gap  150 . This effectively allows first mandrel segment  114  to reset after each actuation without causing movement of second mandrel segment  152 . As a result, positioner device  102  is able to maintain the position of second mandrel segment  152  to provide substantially precise control of positioning of valve  22 . 
   Positioner device  102  includes a positioner sleeve  154  having a sawtooth arrangement of a plurality of generally triangular juts or protrusions  158 A- 158 F formed in the outer surface of positioner device  102 . Positioner device  102  is mounted about second mandrel segment  152  by ball bearings  156  connected to the upper and lower ends of positioner sleeve  154 . Ball bearings  156  allow positioner sleeve  154  to rotate by a predetermined amount with respect to second mandrel segment  152 . 
   Positioner device  102  includes a positioner finger  160  that is fixably mounted with respect to housing  104  of choke system  18 . At its upper end, positioner finger  160  has a positioner detent  162  that is in contact with, or in close proximity to, the outer wall of positioner sleeve  154 . When second mandrel segment  152  is moved downwardly, positioner sleeve  154  moves downwardly with it. Initial downward movement of positioner device  154  by a distance indicated as D 2  causes positioner detent  162  to cross over first jut  158 A so that lower surface  164  of positioner detent  162  is in abutment with upper surface  166 A of first jut  158 A. Movement of second mandrel segment  152  causes positioner detent  162  to cross over juts ( 158 B- 158 F). Each jut  158  may correspond to a position of valve  22  or entry into an alternative path leading to a position of valve  22 . 
   As shown in  FIG. 2C , the lower end of second mandrel segment  152  is threadably attached to a valve mandrel  168  in which an orifice  170  is formed. Below orifice  170  is a seat  174  attached to, or integrally formed in, the outer surface of valve mandrel  168 . Seat  174  is preferably formed of a material having a low coefficient of friction, a high hardness, and that is erosion resistant, such as tungsten carbide or other material having these characteristics. Another seat  172  for engagement with seat  174  is formed on the inner wall of a housing section  176  in choke system  18 . Seat  172  is similarly formed of a material having a low coefficient of friction, high hardness, and that is erosion resistant. In its illustrated position in  FIG. 2C , corresponding angled surfaces of seats  172  and  174  are sealably engaged with each other to provide a closed position of valve  22 . As a result, fluid flowing into valve  22  through openings  178  (formed in the housing of valve  22 ) is blocked from inner bore  28  of choke system  18 . However, downward movement of valve mandrel  168  (caused by actuation of operator mandrel  101  including first and second mandrel segments  114  and  152 ) causes seats  172  and  174  to separate so that fluid can start flowing through orifice  170  between choke system bore  28  and zone  16 . The flow area of orifice  170  is changed as operator mandrel  101  is shifted or stepped through the plurality of positions defined by slot pattern  120  of indexing mechanism  24  to provide a change in flow condition (including pressure drop and/or flow rate). 
     FIG. 3  is a is a graphical, planar view of a prior conventional indexer slot pattern described with reference to  FIGS. 1-2C . The y-axis indicates indexer  100  position and the x-axis is the circumferential slot pattern of indexer  100 . The illustrated indexer slot pattern formed on indexer sleeve  110  is for a four-position valve  22 . The indexer slot pattern includes four positions  200 A,  200 B,  200 C, and  200 D that correspond to the position of valve  22 . Indexer  100  completes a full revolution about its longitudinal axis by going from position  200 A to  200 B,  200 B to  200 C,  200 C to  200 D, and  200 D to  200 A. Indexer or valve positions  200 , are connected in a predetermined shifting sequence along primary path  201 . For example, when indexer detent  108  is in initial position  200 A, valve  22  (orifice  170 ) is closed. At second position  200 B, orifice  170  is partially opened. At second position  200 C, orifice  170  is opened an increment greater than at preceding position  200 B. At subsequent position  200 D, orifice  170  is fully opened. 
   In operation a hydraulic signal is applied such that indexer  100  is actuated moving detent  108  from initial position  200 A through first slot leg  202 A of primary path  201 , upon release of the hydraulic signal, a spring or an opposing hydraulic signal will move the indexer detent  108  in second slot leg  204 A of primary path  201  to position  200 B. To further open valve  22 , the hydraulic signal is repeated moving detent  108  relative to first and second groove legs  202 B and  204 B to position  200 C. In the prior art mechanical indexer systems, valve  22  may only be moved from position  200 C to a subsequent position. Thus, if valve  22  is in position  200 C and well conditions dictate that valve  22  be closed or choked, the indexer must be cycled through the subsequent positions to the closed position or a preceding position. 
     FIG. 4  is graphical, planar view of an embodiment of indexer slot pattern  120  for four-position valve  22 . Operation of indexer slot pattern  120  is described with reference to  FIGS. 1 through 3 . Slot pattern  120  includes a primary path  201  and one or more alternate slot paths  206 . 
   Primary path  201  defines a predetermined shifting sequence of valve positions  200  at and between open and closed. Alternate slot paths  206  provide a mechanism for operating valve  22  to a preceding position in the predetermined sequence without cycling or shifting through all of the intervening positions  200  of the primary path sequence. For example, detent  108  is in intermediate position  200 B and valve  22  is partially open. Well conditions dictate that valve  22  be closed immediately and that further flow or increased flow through valve  22  may result in damage to the well or formation. A fluid pressure is applied in activation chamber  124  moving indexer sleeve  110  until detent  108  is positioned at alternate path  206 A. Upon release of fluid pressure, movement reverses and indexer detent is positioned at preceding position  200 A via alternate path  206 A. The hydraulic control signal may be varied in duration and/or in amplitude to shift valve  22  to a subsequent position along primary path  201  or to a preceding position  200  in the primary path sequence vie an alternate path  206 . 
   Valve  22  may be shifted to a subsequent position by sending two consecutive opposing primary actuation signals to indexer  100 . Valve  100  may be shifted to a preceding position by sending a set of two consecutive opposing alternate actuation signals to indexer  100 . In one embodiment, the initial signal of the set of two primary actuation signals is of a longer duration than the initial signal of the set of two alternative actuation signals. In another embodiment, the initial signal of the set of two primary actuation signals is a pressure signal greater than then the initial pressure signal of the initial signal of the set of two alternative actuation signals. 
   From the foregoing detailed description of specific embodiments of the invention, it should be apparent that a mechanic indexer system for moving an indexer and choke assembly to a preceding position that is novel has been disclosed. Although specific embodiments of the invention have been disclosed herein in some detail, this has been done solely for the purposes of describing various features and aspects of the invention, and is not intended to be limiting with respect to the scope of the invention. It is contemplated that various substitutions, alterations, and/or modifications, including but not limited to those implementation variations which may have been suggested herein, may be made to the disclosed embodiments without departing from the spirit and scope of the invention as defined by the appended claims which follow.