Patent Publication Number: US-7584800-B2

Title: System and method for indexing a tool in a well

Description:
BACKGROUND 
   Well completion equipment is used in a variety of well related applications involving, for example, the production of fluids. The completion equipment is deployed in a wellbore and often comprises one or more downhole tools that have a plurality of operating positions or settings. For example, downhole chokes may have a plurality of different flow positions. 
   One way of actuating the downhole tools between positions is to connect the tool to an indexer. Many types of indexers are available to actuate downhole tools from one sequential position to another and to hold the tool at a desired position. The indexer typically has a sleeve with a plurality of slots having different lengths that correspond with different indexer settings and thus different downhole tool positions. The indexer is adjusted from one setting to another by an appropriate force input, such as a hydraulic input, to shift the sleeve from one slot setting to another, as known in the art. 
   In fluid, e.g. hydraulic, actuated indexers, the quantity of hydraulic control fluid displaced with each move to a different setting is the same. Accordingly, although it may be possible to determine that a move from one setting to another has been achieved, it is difficult for the operator to accurately determine the specific indexer setting and thus the specific downhole tool position. 
   SUMMARY 
   In general, the present invention provides a system and method for indexing in a downhole environment. An indexer is provided with a plurality of operating settings that correspond to downhole tool positions when the indexer is coupled to a downhole tool for actuation within a wellbore. The amount of control fluid required to actuate the indexer for each of the plurality of operating settings is unique. In other words, the fluid used to achieve each setting is different from the quantity of fluid required for adjustment to any of the other settings. This enables measurement of the actuating fluid used and accurate determination of the specific setting of the indexer and any connected downhole tool. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Certain embodiments of the invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and: 
       FIG. 1  is a front elevation view of a completion deployed in wellbore, according to an embodiment of the present invention; 
       FIG. 2  is an isometric view of a sleeve of the indexer illustrated in  FIG. 1 , according to an embodiment of the present invention; 
       FIG. 3  is a graphical representation of a plurality of indexer settings, according to an embodiment of the present invention; 
       FIG. 4  is a schematic illustration of an actuation system of the indexer illustrated in  FIG. 1 , according to an embodiment of the present invention; 
       FIG. 5  is a schematic illustration of another embodiment of the actuation system illustrated in  FIG. 4 ; and 
       FIG. 6  is a flow chart representing a methodology of utilizing the system illustrated in  FIG. 1 , according to an embodiment of the present invention. 
   

   DETAILED DESCRIPTION 
   In the following description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood by those of ordinary skill in the art that the present invention may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible. 
   The present invention relates to indexers and to well systems having multi-position tools that may be selectively adjusted by an indexer. The system and methodology provide a way of determining when the indexer actuates from one setting to another to move a multi-position tool from one operational position to another. Additionally, feedback is provided to an operator such that the operator is readily able to determine the actual indexer setting and tool position after adjustment of the indexer from one setting to another. 
   Referring generally to  FIG. 1 , one embodiment of a well system  20  is illustrated as comprising a well completion  22  deployed for use in a well  24  having a wellbore  26 . The wellbore may be lined with a wellbore casing  28  having perforations through which fluid is able to flow between a surrounding formation  30  and wellbore  26 . Completion  22  is deployed in wellbore  26  below a wellhead  32  disposed at a surface location  34 , such as the surface of the Earth or a seabed floor. In many applications, wellbore  26  is formed, e.g. drilled, in formation  30  for access to desirable fluids held by the formation, such as oil or gas. 
   Completion  22  is located within the interior of casing  28  and comprises a tubing  36  supporting a plurality of completion components  38 . In this embodiment, well completion  22  comprises a downhole tool  40  having a plurality of operating positions. Downhole tool  40  is moved from one operating position to another by an indexer  42  operatively coupled to the downhole tool  40 , as known to those of ordinary skill in the art. By way of specific example, downhole tool  40  may comprise a choke having a plurality of positions that are selected to control the amount of fluid flow through ports, such as radial ports  44 . Indexer  42  is actuated selectively from one indexer setting to another by fluid inputs supplied to indexer  42  via one or more fluid control lines  46 . The fluid inputs are initiated by a fluid supply and control system  48  coupled to control line  46  and located at, for example, surface  34 . Well system  20  also comprises a volume-recording control system  50  for measuring the amount of fluid supplied to and/or returned from indexer  42 . System  50  may comprise a manual system or a computerized control system like the Surface Hydraulic Control System available from Schlumberger Corporation. 
   Referring generally to  FIG. 2 , an indexer sleeve  52  of indexer  42  is illustrated. The indexer sleeve  52  comprises a track  54  having a plurality of elongated portions that define a plurality of sequential indexer settings. With additional reference to  FIG. 3 , this particular embodiment has elongated track portions  56 ,  58 ,  60 ,  62 ,  64  and  66  that each define a unique indexer setting. An indexer positioning mechanism  68 , e.g. a tubular indexer housing, undergoes relative movement with respect to indexer sleeve  52  while being constrained to track  54  via a guide member  70  that follows track  54  from one indexer setting to another as sleeve  52  and mechanism  68  undergo relative movement. For example, elongated track portion  56  may represent a closed setting with indexer positioning mechanism  68  and indexer sleeve  52  at a state of greatest relative contraction. Upon appropriate input via fluid control line  46 , movement of guide member  70  and indexer positioning mechanism  68  relative to indexer sleeve  52  is forced along a path  72 , as represented by arrows in  FIG. 3 . The guide member  70  is forced to a lateral transfer region  74  of track  54 , and guide member  70  is then shifted laterally to elongated track portion  58 . The guide member  70  is then returned along a path  76  of elongated track portion  58  to the next sequential indexer setting  78 . This process can be repeated to adjust the indexer to each sequential setting  80 ,  82 ,  84 ,  86  and  88 . When the indexer  42  is coupled to downhole tool  40 , the relative expansion and/or contraction of indexer sleeve  52  relative to indexer positioning mechanism  68  adjusts downhole tool  40  to its corresponding tool positions. For example, if downhole tool  40  comprises a choke having radial ports  44 , each indexer setting corresponds to a specific flow position of the choke. In the example illustrated, indexer  42  and downhole tool  40  have six settings/positions, however the indexer and tool may be designed with a greater or lesser number of setting/positions. 
   As with conventional indexers, actuation of the indexer from one setting to another can be accomplished with fluid input via fluid control line  46 . However, the present indexer  42  makes the amount of control fluid displaced in adjusting the indexer to each setting a unique quantity of fluid relative to the quantity of fluid required for actuation to the other indexer settings. The amount of fluid displaced for each indexer setting, and thus for each tool position, can be monitored by, for example, volume-recording control system  50 . In this example, the control fluid may comprise a hydraulic fluid. 
   During actuation of indexer  42  from one setting to the next sequential setting, the amount of fluid supplied during relative indexer component movement along path  72  is greater than the amount of fluid returned during relative indexer component movement along path  76 . Accordingly, an operator can determine that the indexer has changed settings, and thus the downhole tool  40  also has successfully changed tool positions. However, the net difference in volume of fluid between the amount of fluid supplied and the amount of fluid returned is unique for each sequential setting. Accordingly, the measured net difference in volume corresponds to a specific sequential change in setting, e.g. a move from the indexer setting  78  to indexer setting  80 , a move from indexer setting  80  to indexer setting  82 , etc. Based on the unique volume of displaced fluid, e.g. net fluid volume, the well operator is able to determine the exact indexer setting and downhole tool position following transition to each new indexer setting/tool position. Providing a unique amount of fluid displacement that corresponds with each specific indexer setting can be achieved by, for example, forming track  54  such that each pair of adjacent elongated tracks has a difference in length that is unique relative to the difference in length of any of the other pairs of adjacent elongated tracks. For example, the difference in length between elongated tracks  56  and  58  is unique relative to the difference in length between elongated tracks  58  and  60 . Accordingly, the net fluid displaced is unique to each new sequential setting, thereby enabling the operator to determine the exact indexer setting and thus the exact position of downhole tool  40 . Furthermore, the different track lengths also can be used to provide the operator with positioning information based on the unique volume of displaced fluid for movement along each individual track. This unique volume of displaced fluid can be measured by volume-recording control system  50 , enabling the operator to determine the exact indexer and tool setting at each indexer half position that occurs when guide member  70  is forced to lateral transfer region  74 . 
   As with conventional indexers, the actuation of indexer  42  can be achieved by fluid input to a fluid cylinder that forms a part of the indexer. As illustrated schematically in  FIG. 4 , a double-acting cylinder system  90  may be used to actuate indexer  42 . In this embodiment, a movable hydraulic actuation member, such as a piston  92 , is slideably mounted within a cylinder  94 , and piston  92  is selectively moved along cylinder  94  via hydraulic input through one of the control lines  46 . For example, hydraulic fluid input through the lower control line  46  into a cylinder chamber  96  drives piston  92  along the cylinder in a first direction and forces actuation of the indexer  42  along path  72 . Subsequently, hydraulic fluid may be input to an upper cylindrical chamber  98  via the upper control line  46  to drive piston  92  in an opposite direction, forcing actuation of indexer  42  along path  76 . This provides double-acting control over movement of piston  92 . The difference in fluid volume input and returned through the lower control line  46  corresponds with a specific indexer setting. As explained above, however, the unique volume of displaced fluid corresponding with movement along each path also can be used to determine the specific indexer setting. By way of example, the fluid supplied to move up path  72  tells the operator from which position the indexer/tool is moving. Likewise, fluid returned from travel down path  76  tells the operator to which position the indexer/tool is moving. 
   Of course, the configuration of double-acting cylinder system  90  can vary depending on the size and design of indexer  42 . In general, cylinder  94  may be connected to or integrally formed with either indexer sleeve  52  or indexer positioning mechanism  68 . Piston  92  is coupled to the other of the indexer sleeve  52  or indexer positioning mechanism  68  via an appropriate connection  100 . Accordingly, fluid input into either cylindrical chamber  96  or cylindrical chamber  98  forces controlled relative movement between indexer sleeve  52  and indexer positioning mechanism  68 , enabling controlled sequential movement of indexer  42  from one indexer setting to another. This, in turn, controls the adjustment of the downhole choke or other downhole tool  40  from one tool position to another. 
   As illustrated in  FIG. 5 , an alternate embodiment of indexer  42  incorporates a single-acting cylinder system  102 . In this embodiment, chamber  96  of cylinder  94  receives hydraulic input from a single fluid control line  46  to selectively force piston  92  along cylinder  94 . This motion, however, is resisted by a spring member  104  which also serves to force piston  92  in an opposite direction once pressure is released from the single control line  46 . In either embodiment, the unique volumes of displaced hydraulic fluid used in moving piston  92  and indexer  42  from one indexer setting to another correspond with specific indexer settings, thereby providing feedback to the well operator as to the actual indexer setting and tool position. 
   One embodiment of the methodology for achieving controlled indexing downhole with feedback as to actual tool position is illustrated by the flowchart of  FIG. 6 . As illustrated, indexer  42  initially is coupled to downhole tool  40 , as shown by block  106 . In many applications, indexer  42  is coupled to a multiposition choke for controlling fluid flow in the wellbore. The indexer  42  and downhole tool  40  are then moved downhole to a desired wellbore location, as illustrated by block  108 . As illustrated in  FIG. 1 , the indexer and downhole tool may be deployed as part of a completion on tubing  36  for use in the production of hydrocarbon based fluids from formation  30 . 
   Once at the desired wellbore location, the indexer  42  may be actuated to a sequential setting via fluid input provided through fluid control line  46 , as illustrated by block  110 . The actuation of indexer  42  consequently adjusts downhole tool  40  to a new position, as illustrated by block  112 . Upon adjustment of downhole tool  40 , the fluid displaced can be measured, as illustrated by block  114 . The fluid displaced is then compared to values corresponding with specific indexer settings/tool positions, e.g. indexer settings  78 ,  80 ,  82 ,  84 ,  86  and  88 , to determine the actual indexer setting and downhole tool position, as illustrated by block  116 . This fluid measurement can be performed, for example, by volume-recording control system  50 . 
   In this embodiment, the combination of indexer  42 , downhole tool  40  and volume-recording control system  50  enable an operator to use fluid pumped down through control line  46  effectively as feedback to distinguish the actual new position of tool  40 . Furthermore, the difference in amount of fluid supplied relative to the amount returned verifies to the operator that an adjustment or shift in position has occurred. 
   Accordingly, although only a few embodiments of the present invention have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this invention. Such modifications are intended to be included within the scope of this invention as defined in the claims.