Abstract:
A flow control device for use in a wellbore to allow flow of formation fluid into the wellbore comprises a valve member adapted to move when disposed in the wellbore. A fluid line supplies a working fluid under pressure to move the valve member to allow the fluid to flow into the wellbore. A sensor in the wellbore, and associated with the fluid line, provides an indication of a position of the valve member. A method of determining a state of a flow control tool within a wellbore comprises supplying fluid under pressure to the flow control tool to move a flow control member of the tool into the state. Pressure of the supplied fluid is detected downhole. The state of the flow control device is determined from the detected pressure of the supplied fluid.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/576,202, filed Jun. 1, 2004, which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates generally to the hydraulic control of downhole tools and, particularly to methods and devices for determining the state of such hydraulically-actuated tools. 
     2. Description of the Related Art 
     Production of hydrocarbons from a downhole well requires subsurface production equipment to control the flow of hydrocarbon fluid into the production tubing. Typical flow control equipment might include a sliding sleeve valve assembly or other valve assembly wherein a sleeve is moved between open and closed positions in order to selectively admit production fluid into the production tubing. The valve assembly is controlled from the surface using hydraulic control lines or other methods. 
     In a simple system, a sleeve valve would be moveable between just two positions or states: fully opened and fully closed. More complex systems are provided where a well penetrates multiple hydrocarbon zones, and it is desired to produce from some or all of the zones. In such a case, it is desirable to be able to measure and control the amount of flow from each of the zones. In this instance, it is often desirable to use flow control devices that may be opened in discrete increments, or states, in order to admit varying amounts of flow from a particular zone. Several “intelligent” hydraulic devices are known that retain information about the state of the device. Examples of such devices include those marketed under the brand names HCM-A In-Force™ Variable Choking Valve and the In-Force™ Single Line Switch, both of which are available commercially from Baker Oil Tools of Houston, Tex. These devices incorporate a sliding sleeve that is actuated by a pair of hydraulic lines that move the sleeve within a balanced hydraulic chamber. A “J-slot” ratchet arrangement is used to locate the sleeve at several discrete positions that permit varying degrees of fluid flow through the device. 
     Because these devices are capable of being controlled between multiple states, or positions, determination and monitoring of the positions of the devices is important. To date, position determination has been accomplished by measurement of the amount of hydraulic fluid that is displaced within the control lines as the device is moved between one position and the next. Measuring displacement of hydraulic fluid will provide an indication of the particular state that the tool has moved to because differing volumes of fluid are displaced during each movement. In some instances, however, such as with a subsea pod, it may not be possible to measure fluid volume. Also, the fluid volume measurement technique may be inaccurate at times for a variety of reasons, including leaks within the hydraulic control lines and connections or at seals that lead to fluid loss, which leads to an incorrect determination of position. In addition, the hydraulic control lines may expand under pressure (storage effects) or become distorted due to high temperatures within the wellbore. In long lines, the additional storage volume in such expansion/distortion may be larger than the normally small differences in fluid volume between different movements and lead to inaccurate determinations of position. 
     The present invention addresses some of the problems of the prior art noted above. 
     SUMMARY OF THE INVENTION 
     In one aspect of the present invention, a flow control device for use in a wellbore to allow flow of formation fluid into the wellbore comprises a valve member adapted to move when disposed in the wellbore. A fluid line supplies a working fluid under pressure to move the valve member to allow the fluid to flow into the wellbore. A sensor in the wellbore, and associated with the fluid line, provides an indication of a position of the valve member. 
     In another aspect, a downhole flow control device comprises a hydraulically-actuated sleeve valve that is operable between a first position wherein the valve is in a first fluid flow state and a second position wherein the valve is in a second fluid flow state. A hydraulic control line is operably associated with the sleeve valve for supplying hydraulic fluid to operate the valve between states. A downhole pressure sensor operably associated with the hydraulic control line detects fluid pressure therein to provide an indication of the state of the sleeve valve. 
     In another aspect, a method of determining a state of a flow control tool within a wellbore comprises supplying fluid under pressure to the flow control tool to move a flow control member of the tool into the state. Pressure of the supplied fluid is detected downhole. The state of the flow control device is determined from the detected pressure of the supplied fluid. 
     In yet another aspect of the present invention, a method of determining the state of a flow control tool within a wellbore comprises detecting a fluid flow downhole within a hydraulic supply conduit in fluid communication with the flow control tool. The state of the flow control tool is determined from the detected fluid flow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For detailed understanding of the present invention, references should be made to the following detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings, in which like elements have been given like numerals, wherein: 
         FIG. 1  is a schematic depiction of an exemplary wellbore system wherein multiple hydrocarbon zones and fluid entry points; 
         FIG. 2  is a schematic depiction, in side cross-section, of an exemplary sliding sleeve valve assembly incorporating a fluid pressure sensor system in accordance with the present invention; 
         FIG. 3A  is an illustration of a J-slot ratchet and lug arrangement according to one embodiment of the present invention; 
         FIG. 3B  is an illustration of an alternative J-slot ratchet and lug arrangement according to one embodiment of the present invention; 
         FIG. 4  is a graph of fluid pressure versus time; and 
         FIG. 5  is a block diagram of the surface monitoring and control system according to one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       FIG. 1  illustrates an exemplary production well  10  that penetrates the earth  12  into multiple hydrocarbon zones, such as zones  14 ,  16 . The well  10  is cased with casing  18 , and perforations  20  are disposed through the casing  18  proximate each of the zones  14 ,  16  to provide a flow point for hydrocarbon fluids within the zones  14 ,  16  to enter the well  10 . It is noted that, although a single wellbore is shown, there may, in practice, be a plurality of multilateral wellbores, each penetrating one or more zones such as zones  14 ,  16 . Additionally, although only two zones are shown, those skilled in the art will recognize that there may be more such zones. 
     A production tubing string  22  is disposed within the well  10  from a wellhead  24  and includes flow control devices  26 ,  28  located proximate the zones  14 ,  16 , respectively. Packers  30  isolate the flow control devices  26 ,  28  within the well  10 . In one embodiment, each of the flow control devices  26 ,  28  is a sliding sleeve flow control device that is capable of more than two operable positions, also called open/closed states. Examples of suitable flow control devices for this application include those marketed under the brand names HCM-A In-Force™ Variable Choking Valve and the In-Force™ Single Line Switch, both of which are available commercially from Baker Oil Tools of Houston, Tex. 
     A monitoring and control station  32  is located at the wellhead  24  for operational control of the flow control devices  26 ,  28 . Hydraulic control lines, generally shown at  34  extend from monitoring and control station  32  down to the flow control devices  26 ,  28 . The monitoring and control station  32  is of a type known in the art for control of hydraulic downhole flow control devices, and is described in more detail below in reference to  FIG. 5 . 
       FIG. 2  illustrates an exemplary individual flow control device  26  and illustrates its interconnection with an exemplary pressure sensor position detection system. The flow control device  26  is illustrated in simplified schematic form for ease of description. In practice, the flow control device  26  may be an HCM-A In-Force™ Variable Choking Valve brand flow control device marketed by Baker Oil Tools of Houston, Tex. The device  26  includes a sliding sleeve assembly sub  36  having a tubular outer housing  38  that defines a fluid chamber  40  therewithin. Fluid openings  42  are disposed through the housing  38  below the fluid chamber  40 . A sliding sleeve  44  is retained within the housing  38  and includes a number of fluid ports  46  disposed radially therethrough. Seals  43   a  and  43   b  are disposed in outer housing  38  above and below fluid openings  42 . When the sliding sleeve  44  is axially displaced such that piston  50  is near the bottom of chamber  40 , the ports  46  are below lower seal  43   b  and there is no flow into bore  48  of housing  38 . Depending upon the axial position of the sliding sleeve  44  within the housing  38  and within the seals  43   a,b , the ports  46  of the sleeve  44  can be selectively aligned with the fluid openings  42  in the housing  38  to permit varying degrees of fluid flow into the bore  48  of the housing  38  as the ports  46  overlap the openings  42  in varying amounts. The sliding sleeve  44  also includes an enlarged outer piston portion  50  that resides within the chamber  40  and separates chamber  40  into an upper chamber  52  and a lower chamber  54 . A seal (not shown) on the outer diameter of piston  50  hydraulically isolates upper chamber  52  and lower chamber  54 . Piston  50  exposes substantially equal piston area to each of chambers  52  and  54  such that equal pressures in chambers  52  and  54  result in substantially equal and opposite forces on piston  50  such that piston  50  is considered “balanced”. To move piston  50 , a higher pressure is introduced in one chamber and fluid is allowed to exit from the other chamber at a lower pressure, resulting in an unbalanced force on piston  50 , and thereby moving piston  50  in a desired direction. 
     Hydraulic control lines  34   a  and  34   b  are operably secured to the housing  38  to provide fluid communication into and out of each of the fluid receiving chambers  52 , 54 . As those skilled in the art will recognize, the sliding sleeve  44  may be axially moved within the housing  38  by transmission of hydraulic fluid into and out of the fluid receiving chambers  52 , 54 . For example, if it is desired to move the sleeve  44  downwardly with respect to the housing  38 , hydraulic fluid is pumped through the control line  34   a  and into only the upper fluid receiving chamber  52 . This fluid exerts pressure upon the upper face of the piston  50 , urging the sleeve  44  downwardly. As the sleeve  44  moves downwardly, hydraulic fluid is expelled from the lower fluid receiving chamber  54  through control line  34   b  toward the surface of the well  10 . Conversely, if it is desired to move the sleeve  44  upwardly with respect to the housing  38 , hydraulic fluid is pumped through control line  34   b  into the lower fluid receiving chamber  54  to exert pressure upon the lower side of the piston portion  50 . As the sleeve  44  moves upwardly, hydraulic fluid is expelled from the upper fluid receiving chamber  52  through the control line  34   a.    
     In one embodiment, see  FIG. 3A , a J-slot ratchet assembly sub  56  is secured to the upper end of the sliding sleeve valve housing  38 . The ratchet assembly sub  56  serves to provide a number of preselected axial positions, or states, for the sliding sleeve  44  within the sleeve assembly sub  36 , thereby providing a preselected amount of flow control due to the amount of axial overlap of fluid ports  46  with fluid openings  42 . The ratchet assembly sub  56  includes a pair of outer housing members  58 ,  60  that abut one another and are rotationally moveable with respect to one another. A lug sleeve  62  is retained within the sub  56  and presents upper and lower outwardly extending lugs  64 , 66 . The lugs  64 ,  66  engage lug pathways inscribed on the inner surfaces of the housing members  58 ,  60 . These pathways are illustrated in  FIG. 3A  which depicts the inner surfaces of the outer housing members  58 ,  60  in an “unrolled” manner. The upper outer housing member  58  has an inscribed tortuous pathway  68  within which upper lug  64  resides. The lower housing member  60  features an inscribed lug movement area  70  having a series of lower lug stop shoulders  72   a - 72   e  that are arranged in a stair-step fashion. The stair step shoulders  72   a - 72   e  are related to the amount of axial overlap of fluid ports  46  with fluid openings  42 . Lower lug passage  74  is located adjacent the stop shoulder  72   e . Additionally, the lower housing member  60  presents an upper lug stop shoulder  76 . An upper lug passage  78  is defined within the upper housing member  58  and, when the upper and lower housing members  58 ,  60  are rotationally aligned properly, the upper lug passage  78  is lined up with lug entry passage  80  so that upper lug  64  may move between the two housing members  58 ,  60 . 
     Axial movement of the sliding sleeve  44  by movement of piston  50  as described above moves the abutting lug sleeve  62  axially within the ratchet assembly sub  56 . As this occurs, the upper lug  64  is moved consecutively among lug positions  64   a ,  64   b ,  64   c ,  64   d ,  64   e ,  64   f ,  64   g ,  64   h ,  64   i , and  64   j . Finally, the upper lug  64  moves to its final lug position  64   k , which corresponds to a fully closed position, or state, for the sliding sleeve assembly sub  36 . Additionally, the lower lug  66  is moved consecutively through lug positions  66   a - 66   k . When lug  66  is located adjacent upper shoulder  76 , the fluid ports  46  are aligned with fluid openings  42  to provide a fully open flow condition. It can be seen that abutment of the lower lug  66  upon each of the lower shoulders  72   a , 72   e  results in a progressively lower axial position for the lug sleeve  62  with respect to the housing members  58 ,  60 . These different axial positions result in different flow control positions or states for the sliding sleeve  44 , by varying the amount of axial overlap of fluid opening  42  with flow ports  46  (see  FIG. 2 ). As illustrated in  FIG. 3A , the flow opening becomes progressively smaller as lower lug  66  moves from position  66   a  to  66   i  and is eventually closed at position  66   k . When the lugs  64  and  66  are in the positions  64   k  and  66   k , respectively, the sleeve  44  is moved downward such that ports  46  are below seal  43   b  and there is no flow. By proper selection of the step change between successive states, a predetermined amount of fluid can be required to move the sliding sleeve between successive states. In one embodiment, the amount of movement, and hence the amount of fluid required, is selected such that the difference in movement between each successive state is uniquely different. By such selection, the amount of fluid required for each movement is unique and the location of the sleeve can then be identified by the amount of fluid required to move the sleeve to a position. 
       FIG. 3B  shows another embodiment in which the J-slot arrangement is oriented such that the flow opening progressively increases as the system is operated. The J-slot arrangement on the inside of housings  160  and  158  are shown in an “unrolled” view. As shown in  FIG. 3B , upper lug  164  moves through positions  164   a - 164   m  while lower lug  166  moves through positions  166   a - 166   m , respectively. Lower shoulder  176  acts as a stop for lower lug  166 . Upper shoulders  172   a - g  show a stair-step progression that is related to the amount of flow opening caused by the alignment of ports  46  and flow openings  42  in sleeve  44 , however, as contrasted with  FIG. 3A , when lug  166  is located against shoulder  176 , there is no direct flow path through opening  42  and ports  46 , but the ports are not below seal  43   b . Therefore, there is some leakage into the bore  48  caused by clearances between sleeve  44  and housing  38 , and is nominally referred to as the diffused position. As indicated with respect to  FIG. 3A , the positions of shoulders  172   a - g  may be selected to provide unique indications of sleeve  44  position from the amount of fluid required to move sleeve  44  between consecutive positions. To close sleeve  44  using the arrangement of  FIG. 3B , lugs  164  and  166  are moved downward through passages  178  and  179  until ports  46  are below seal  43   b  (see  FIG. 2 ). It is noted that other lug and ratchet arrangements may be used within the scope of the invention. 
       FIG. 4  depicts a graph showing fluid pressure, as detected by the pressure sensor  82 , versus time. The curve of the graph is illustrative of the fluid pressure within control line  34   a  during the process of moving the sliding sleeve  44 . As hydraulic pressure is applied to the upper fluid receiving chamber  52 , the fluid pressure within the control line  34   a  will begin to rise, as illustrated by the first section  90  of the graph. Fluid pressure will continue to rise until forces resisting piston motion, such as internal tool friction, are overcome. Once the friction is overcome piston  50  begins to move and, as a result, expels fluid from that lower chamber  54 . At this point, the sleeve  44  is moving downwardly and the pressure increase in control line  34   a  stops and levels off at a substantially constant pressure during sleeve movement. After the sleeve  44  has been moved to its next position or state, as limited by the ratchet sub assembly  56 , the fluid pressure within the line  34   a  will again begin to rise, as the sleeve  44  will move no further. The inclined portion  94  of the graph in  FIG. 4  illustrates this. Ultimately, the fluid pressure within the line  34   a  will level off as the pump pressure reaches a stall pressure of the pump, or alternatively, the pressure reaches a relief value in the supply line. 
     By the proper selection of the stair-step shoulders of FIGS.  3 A,B, the length of time (x) for the level pressure associated with sleeve movement (portion  92  of  FIG. 4 ) correlates to particular movements between tool states for the flow control device  26 . For example, movement of the device  26  from a position wherein the lower lug  66  is at  66   b  to a position wherein the lower lug  66  is at  66   c  will take less time than if the device is moved from a position wherein lug  66  is at  66   h  and then moved to  66   i . Therefore, measurement of “x” will reveal the state that the tool  26  has been moved to. In one embodiment, the length of “x” is different for each particular movement of the tool  26 . 
     Referring to  FIGS. 2 and 5 , it is noted that a sensor  82  is operably associated with the fluid control line  34   a  to detect the amount of fluid pressure within the line  34   a . In one embodiment, sensor  82  is a pressure sensor that is physically positioned at or near the housing  38  of the flow control device  26  to minimize the fluid storage effects of the control line  34   a . Alternatively, sensor  82  may be a flow sensor that directly measures the amount of fluid passing through control line  34   a  and into, or out of, the appropriate chamber in flow control device  26 . A data line  84  extends from the sensor  82  upwardly to the monitoring and control station  32 . In one embodiment, data line  84  comprises an electrical and/or optical conductor. Readings detected by the sensor  82  are transmitted to the station  32  over dataline  84 . Alternatively, readings of sensor  82  might be transmitted wirelessly to the surface, such as for example by acoustic techniques and/or electromagnetic techniques known in the art. Although a sensor is only shown affixed to control line  34   a , it will be understood that sensors may be attached to either, or to both, control lines  34   a ,  34   b.    
     Monitoring and control station  32  functionally comprises a hydraulic system for powering the flow control system and suitable electronics and computing equipment for powering downhole sensor  82  and detecting, processing, and displaying signals therefrom. In one embodiment, monitoring and control station  32  provides feedback control using signals from sensor  82  to control the hydraulic supply system. Monitoring and control station  32  comprises pump controller  201  controlling the output of pump  202  having fluid supply  203 . Fluid from pump  202  powers downhole tool  26 . In addition, processor  204 , having memory  205  is associated with circuits  206  to provide power and an interface with sensor  82 . Signals from sensor  82  are received by circuits  206  and then transmitted to processor  204 . Processor  204 , acting according to programmed instructions, provides a record and/or storage of the pressure vs. time of from sensor  82  using hard copy  207 , display  208 , and mass storage  209 . In one embodiment, the length of time (x) associated with each sleeve movement, as described previously, may be stored in memory  205 . The measured length of time (x) is compared to the stored signatures and the sleeve position determined based on the comparison. In another embodiment, the pressure profile for each movement is stored in memory  205  and a measured profile is compared to those in memory to determine the sleeve position. Alternatively, manual controls  200  may be operator controlled to operate the hydraulic system. 
     While described herein as a system having dual hydraulic control lines and a balanced piston, it will be appreciated by one skilled in the art that the present system is intended to encompass a single hydraulic line system utilizing a piston having a spring return capability. 
     Those of skill in the art will recognize that numerous modifications and changes may be made to the exemplary designs and embodiments described herein and that the invention is limited only by the claims that follow and any equivalents thereof.