Pressure monitoring of control lines for tool position feedback

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.

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.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1illustrates an exemplary production well10that penetrates the earth12into multiple hydrocarbon zones, such as zones14,16. The well10is cased with casing18, and perforations20are disposed through the casing18proximate each of the zones14,16to provide a flow point for hydrocarbon fluids within the zones14,16to enter the well10. 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 zones14,16. Additionally, although only two zones are shown, those skilled in the art will recognize that there may be more such zones.

A production tubing string22is disposed within the well10from a wellhead24and includes flow control devices26,28located proximate the zones14,16, respectively. Packers30isolate the flow control devices26,28within the well10. In one embodiment, each of the flow control devices26,28is 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 station32is located at the wellhead24for operational control of the flow control devices26,28. Hydraulic control lines, generally shown at34extend from monitoring and control station32down to the flow control devices26,28. The monitoring and control station32is of a type known in the art for control of hydraulic downhole flow control devices, and is described in more detail below in reference toFIG. 5.

FIG. 2illustrates an exemplary individual flow control device26and illustrates its interconnection with an exemplary pressure sensor position detection system. The flow control device26is illustrated in simplified schematic form for ease of description. In practice, the flow control device26may be an HCM-A In-Force™ Variable Choking Valve brand flow control device marketed by Baker Oil Tools of Houston, Tex. The device26includes a sliding sleeve assembly sub36having a tubular outer housing38that defines a fluid chamber40therewithin. Fluid openings42are disposed through the housing38below the fluid chamber40. A sliding sleeve44is retained within the housing38and includes a number of fluid ports46disposed radially therethrough. Seals43aand43bare disposed in outer housing38above and below fluid openings42. When the sliding sleeve44is axially displaced such that piston50is near the bottom of chamber40, the ports46are below lower seal43band there is no flow into bore48of housing38. Depending upon the axial position of the sliding sleeve44within the housing38and within the seals43a,b, the ports46of the sleeve44can be selectively aligned with the fluid openings42in the housing38to permit varying degrees of fluid flow into the bore48of the housing38as the ports46overlap the openings42in varying amounts. The sliding sleeve44also includes an enlarged outer piston portion50that resides within the chamber40and separates chamber40into an upper chamber52and a lower chamber54. A seal (not shown) on the outer diameter of piston50hydraulically isolates upper chamber52and lower chamber54. Piston50exposes substantially equal piston area to each of chambers52and54such that equal pressures in chambers52and54result in substantially equal and opposite forces on piston50such that piston50is considered “balanced”. To move piston50, 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 piston50, and thereby moving piston50in a desired direction.

Hydraulic control lines34aand34bare operably secured to the housing38to provide fluid communication into and out of each of the fluid receiving chambers52,54. As those skilled in the art will recognize, the sliding sleeve44may be axially moved within the housing38by transmission of hydraulic fluid into and out of the fluid receiving chambers52,54. For example, if it is desired to move the sleeve44downwardly with respect to the housing38, hydraulic fluid is pumped through the control line34aand into only the upper fluid receiving chamber52. This fluid exerts pressure upon the upper face of the piston50, urging the sleeve44downwardly. As the sleeve44moves downwardly, hydraulic fluid is expelled from the lower fluid receiving chamber54through control line34btoward the surface of the well10. Conversely, if it is desired to move the sleeve44upwardly with respect to the housing38, hydraulic fluid is pumped through control line34binto the lower fluid receiving chamber54to exert pressure upon the lower side of the piston portion50. As the sleeve44moves upwardly, hydraulic fluid is expelled from the upper fluid receiving chamber52through the control line34a.

In one embodiment, seeFIG. 3A, a J-slot ratchet assembly sub56is secured to the upper end of the sliding sleeve valve housing38. The ratchet assembly sub56serves to provide a number of preselected axial positions, or states, for the sliding sleeve44within the sleeve assembly sub36, thereby providing a preselected amount of flow control due to the amount of axial overlap of fluid ports46with fluid openings42. The ratchet assembly sub56includes a pair of outer housing members58,60that abut one another and are rotationally moveable with respect to one another. A lug sleeve62is retained within the sub56and presents upper and lower outwardly extending lugs64,66. The lugs64,66engage lug pathways inscribed on the inner surfaces of the housing members58,60. These pathways are illustrated inFIG. 3Awhich depicts the inner surfaces of the outer housing members58,60in an “unrolled” manner. The upper outer housing member58has an inscribed tortuous pathway68within which upper lug64resides. The lower housing member60features an inscribed lug movement area70having a series of lower lug stop shoulders72a-72ethat are arranged in a stair-step fashion. The stair step shoulders72a-72eare related to the amount of axial overlap of fluid ports46with fluid openings42. Lower lug passage74is located adjacent the stop shoulder72e. Additionally, the lower housing member60presents an upper lug stop shoulder76. An upper lug passage78is defined within the upper housing member58and, when the upper and lower housing members58,60are rotationally aligned properly, the upper lug passage78is lined up with lug entry passage80so that upper lug64may move between the two housing members58,60.

Axial movement of the sliding sleeve44by movement of piston50as described above moves the abutting lug sleeve62axially within the ratchet assembly sub56. As this occurs, the upper lug64is moved consecutively among lug positions64a,64b,64c,64d,64e,64f,64g,64h,64i, and64j. Finally, the upper lug64moves to its final lug position64k, which corresponds to a fully closed position, or state, for the sliding sleeve assembly sub36. Additionally, the lower lug66is moved consecutively through lug positions66a-66k. When lug66is located adjacent upper shoulder76, the fluid ports46are aligned with fluid openings42to provide a fully open flow condition. It can be seen that abutment of the lower lug66upon each of the lower shoulders72a,72eresults in a progressively lower axial position for the lug sleeve62with respect to the housing members58,60. These different axial positions result in different flow control positions or states for the sliding sleeve44, by varying the amount of axial overlap of fluid opening42with flow ports46(seeFIG. 2). As illustrated inFIG. 3A, the flow opening becomes progressively smaller as lower lug66moves from position66ato66iand is eventually closed at position66k. When the lugs64and66are in the positions64kand66k, respectively, the sleeve44is moved downward such that ports46are below seal43band 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. 3Bshows 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 housings160and158are shown in an “unrolled” view. As shown inFIG. 3B, upper lug164moves through positions164a-164mwhile lower lug166moves through positions166a-166m, respectively. Lower shoulder176acts as a stop for lower lug166. Upper shoulders172a-gshow a stair-step progression that is related to the amount of flow opening caused by the alignment of ports46and flow openings42in sleeve44, however, as contrasted withFIG. 3A, when lug166is located against shoulder176, there is no direct flow path through opening42and ports46, but the ports are not below seal43b. Therefore, there is some leakage into the bore48caused by clearances between sleeve44and housing38, and is nominally referred to as the diffused position. As indicated with respect toFIG. 3A, the positions of shoulders172a-gmay be selected to provide unique indications of sleeve44position from the amount of fluid required to move sleeve44between consecutive positions. To close sleeve44using the arrangement ofFIG. 3B, lugs164and166are moved downward through passages178and179until ports46are below seal43b(seeFIG. 2). It is noted that other lug and ratchet arrangements may be used within the scope of the invention.

FIG. 4depicts a graph showing fluid pressure, as detected by the pressure sensor82, versus time. The curve of the graph is illustrative of the fluid pressure within control line34aduring the process of moving the sliding sleeve44. As hydraulic pressure is applied to the upper fluid receiving chamber52, the fluid pressure within the control line34awill begin to rise, as illustrated by the first section90of 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 piston50begins to move and, as a result, expels fluid from that lower chamber54. At this point, the sleeve44is moving downwardly and the pressure increase in control line34astops and levels off at a substantially constant pressure during sleeve movement. After the sleeve44has been moved to its next position or state, as limited by the ratchet sub assembly56, the fluid pressure within the line34awill again begin to rise, as the sleeve44will move no further. The inclined portion94of the graph inFIG. 4illustrates this. Ultimately, the fluid pressure within the line34awill 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.3A,B, the length of time (x) for the level pressure associated with sleeve movement (portion92ofFIG. 4) correlates to particular movements between tool states for the flow control device26. For example, movement of the device26from a position wherein the lower lug66is at66bto a position wherein the lower lug66is at66cwill take less time than if the device is moved from a position wherein lug66is at66hand then moved to66i. Therefore, measurement of “x” will reveal the state that the tool26has been moved to. In one embodiment, the length of “x” is different for each particular movement of the tool26.

Referring toFIGS. 2 and 5, it is noted that a sensor82is operably associated with the fluid control line34ato detect the amount of fluid pressure within the line34a. In one embodiment, sensor82is a pressure sensor that is physically positioned at or near the housing38of the flow control device26to minimize the fluid storage effects of the control line34a. Alternatively, sensor82may be a flow sensor that directly measures the amount of fluid passing through control line34aand into, or out of, the appropriate chamber in flow control device26. A data line84extends from the sensor82upwardly to the monitoring and control station32. In one embodiment, data line84comprises an electrical and/or optical conductor. Readings detected by the sensor82are transmitted to the station32over dataline84. Alternatively, readings of sensor82might 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 line34a, it will be understood that sensors may be attached to either, or to both, control lines34a,34b.

Monitoring and control station32functionally comprises a hydraulic system for powering the flow control system and suitable electronics and computing equipment for powering downhole sensor82and detecting, processing, and displaying signals therefrom. In one embodiment, monitoring and control station32provides feedback control using signals from sensor82to control the hydraulic supply system. Monitoring and control station32comprises pump controller201controlling the output of pump202having fluid supply203. Fluid from pump202powers downhole tool26. In addition, processor204, having memory205is associated with circuits206to provide power and an interface with sensor82. Signals from sensor82are received by circuits206and then transmitted to processor204. Processor204, acting according to programmed instructions, provides a record and/or storage of the pressure vs. time of from sensor82using hard copy207, display208, and mass storage209. In one embodiment, the length of time (x) associated with each sleeve movement, as described previously, may be stored in memory205. 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 memory205and a measured profile is compared to those in memory to determine the sleeve position. Alternatively, manual controls200may 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.