System and method for formation isolation

A technique employs a formation isolation valve that utilizes a ball rotatably mounted within a valve housing. The valve is designed to enable rotation of the ball about a fixed axis without translation of the ball. Rotation of the ball is achieved by connecting an arm to the ball at a position offset from the axis of rotation. A movable mandrel also is connected to the arm to enable selective actuation of the ball.

BACKGROUND

The following descriptions and examples are not admitted to be prior art by virtue of their inclusion in this section.

In a variety of downhole applications, flow isolation valves are used to isolate formations for reasons related to prevention of fluid loss, underbalanced well control, lubricator valve applications, and other reasons that benefit from the ability to isolate regions along a wellbore. The flow isolation valve may be a ball valve designed to provide a bidirectional pressure seal. The ball valve is moved from an open flow position to a closed position by passing a shifting tool through its center. Typically, a shifting tool is attached below perforating guns on a gun string such that when the perforating guns are pulled out of hole, the shifting tool shifts the ball of the formation isolation valve to a closed position. Once closed, the well head pressure may be safely bled off while the subject formation remains isolated. This allows the well to be suspended for days or even months.

However, the ball of the formation isolation valve also creates a barrier onto which debris is often deposited. The debris can clog the mechanism and ultimately prevent the shifting tool from dislodging the debris during efforts to open the ball. Additionally, existing ball designs employ parts that are difficult to manufacture due to dimensional instability and tight tolerance requirements. The tight tolerances and the complex designs are employed to achieve both rotation and translation of the ball within the ball valve structure. Because of the difficult design requirements, many of the parts manufactured for construction of the ball valves are scrapped, and that leads to additional expense and inefficiency.

SUMMARY

In general, embodiments of the present disclosure comprise a system and methodology for providing a formation isolation valve that utilizes a ball rotatably mounted within a valve housing. The valve is designed to enable rotation of the ball about a fixed axis without translation of the ball. Rotation of the ball is achieved by connecting an arm to the ball at a position offset from the axis of rotation. A movable mandrel also is connected to the arm to enable selective actuation of the ball.

DETAILED DESCRIPTION

In the following description, numerous details are set forth to provide an understanding of the present disclosure. However, it will be understood by those of ordinary skill in the art that embodiments of the present disclosure may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible. In the specification and appended claims: the terms “connect”, “connection”, “connected”, “in connection with”, “connecting”, “couple”, “coupled”, “coupled with”, and “coupling” are used to mean “in direct connection with” or “in connection with via another element”; and the term “set” is used to mean “one element” or “more than one element”. As used herein, the terms “up” and “down”, “upper” and “lower”, “upwardly” and downwardly”, “upstream” and “downstream”; “above” and “below”; and other like terms indicating relative positions above or below a given point or element are used in this description to more clearly describe some embodiments of the disclosure.

Embodiments of the present disclosure generally relate to a flow isolation valve system having a design that is simpler to manufacture and more dependable to use in a well application. The design utilizes simple, strong features that enable dependable actuation of a ball type flow isolation valve. Additionally, the component design enables manufacture with minimal material removal and less dimensional movement. The design also enables ample manufacturing tolerances because of the placement of various functional features on easy to machine pieces, such as inserts used to hold ball trunnions on which the ball of the valve is rotatably mounted. As a result, the tolerances for larger, more difficult parts within the overall assembly may be relaxed.

In one illustrative embodiment, the design of the formation isolation valve employs relatively large yolk arms that are configured to provide great strength. The yoke arms enable employment of large forces to open the ball in the event the ball becomes jammed or stuck with debris. In another embodiment, the yoke arms are replaced by rods that can be used to manipulate the ball between closed and open flow positions. In any of the embodiments, the design of the formation isolation valve also enables use of a full ball instead of a half ball and that allows for the addition of other functional features. For example, a full ball allows the use of a wiper on one side of the ball (e.g., typically at the top of the ball, nearest to the surface) to reduce debris otherwise interfering with the ball. The use of a wiper reduces the potential for jamming the ball or for incurring other interference with ball operation.

Referring generally toFIG. 1, one example of a generic well system20is illustrated as employing a formation isolation valve system22comprising at least one formation isolation valve24. Well system20may comprise a completion26or other downhole equipment that is deployed downhole in a wellbore28. The flow isolation valve24may be one of a wide variety of components included as downhole equipment26. Generally, the wellbore28is drilled down into or through a formation30that may contain desirable fluids, such as hydrocarbon based fluids. The wellbore28extends down from a surface location32beneath a wellhead34or other surface equipment suitable for the given application.

Depending on the specific well application, e.g. such as a well perforation application, the completion/well equipment26is delivered downhole via a suitable conveyance36. However, the conveyance36and the components of completion26often vary substantially. In many applications, one or more packers38is used to isolate the annulus between downhole equipment26and the surrounding wellbore wall, which may be in the form of a liner or casing40. The formation isolation valve24may be selectively actuated to open or isolate formation30with respect to flow of fluid through completion26.

Referring generally toFIG. 2, one exemplary embodiment of formation isolation valve24is illustrated. In this embodiment, the formation isolation valve24comprises a ball42that is held in place by inserts44, with an insert provided on each side of the ball42(only one is visible in this view). As illustrated, ball42may be a full ball rotatably mounted in inserts44via ball trunnions46that are rotatably received in corresponding openings48formed in the inserts. The ball42is thus able to rotate about a fixed axis50and no translation of ball42is required. The inserts44are simple to manufacture and may be formed from a plate material, such as plate steel. Each insert44is positioned in a pocket52formed in an upper cage54and captured between the upper cage54and a lower cage56. The upper cage54and lower cage56are contained within a valve housing58that may be generally tubular in form. The inserts44hold the ball42in a manner that enables selective rotation of the ball via at least one arm60.

A full ball42may generally be configured as a spherically shaped valve component intersected by a cylindrically shaped flow passage. This configuration results in two essentially symmetrical and semi-spherical portions of the ball42being respectively exposed to the upstream and downstream environments across the fixed axis50when the ball42is in a closed position. However, some embodiments may use a half ball (not shown), such as the half ball applications described in U.S. Pat. No. 6,401,826, to Patel, the contents of which are hereby incorporated by referenced in their entirety. A half ball is not necessarily symmetrical across fixed axis50in a closed position. Instead, a half ball may respectively expose only the upper and lower surfaces of a single semi-spherical portion to the upstream and downstream environments in a closed position.

In the embodiment illustrated inFIG. 2, the arm60comprises a pair of yoke arms each having an engagement end62and an actuation end64on generally opposite portions of the arm60(only one arm60is visible in this view). The arm60may be moved linearly to transition ball42between a closed position and an open flow position that enables fluid flow through an interior of formation isolation valve24. A window66may be formed in upper cage54to receive actuation end64and to limit movement of actuation end64so as to control movement of the ball42to between the closed and open positions. The engagement end62is coupled with ball42at a position offset from rotation axis50and may move along a slot68, formed in ball42, when arm60is moved linearly. The slot68is formed in a desired pattern to achieve rotational movement of ball42between the closed and open flow positions when engagement end62is moved along slot68. In some applications, the arm60may be guided during movement by a cage slot69formed in upper cage54.

In the example illustrated, the yoke arm60is attached to a movable mandrel70at its actuation end64. The construction enables adjustments to be made with respect to movement of arm60and/or the attachment of arm60to mandrel70for compensation of manufacturing tolerances. The movable mandrel70is simply moved in a linear direction through valve housing58to cause arm60to rotate ball42between open and closed positions. Accordingly, the ball42is actuated by pivoting the ball on its trunnions46without significant or, in some cases, any translation of the ball. In one specific example, the pivoting motion is caused by linear motion of arm60/engagement end62which passes through slot68in ball42and contacts a face72to cause rotation of the ball. This type of actuation renders ball42and the cooperating components less sensitive to debris because the ball itself does not have to translate but rather simply rotates in place.

Movable mandrel70may be constructed in a variety of configurations for imparting linear movement to arm60. In some applications, mandrel70may comprise a tubular member located within valve housing58for lineal movement along an interior of upper cage54(see, for example,FIG. 3). However, mandrel70may be constructed in a variety of configurations utilizing rods, sleeves, sliding members, pivoting members, and other mechanisms designed to impart the desired motion to arm60. Additionally, movement of mandrel70may be motivated by a variety of actuation systems. For example, the mandrel70may be motivated hydraulically via hydraulic fluid supplied via one or more suitable control lines. In other applications, the mandrel70may be motivated mechanically by shifting the tubing string or running a shifting tool downhole through conveyance36. However, motor driven systems, electric systems, and other types of systems may also be employed to enable controlled movement of mandrel70.

InFIG. 3, a cross-sectional view is provided in which a cross-section has been taken generally through the rotational axis50. In this embodiment, ball42is illustrated as contacted by a seal74disposed along one end of ball42. The seal74is contained in a seal retainer76that maintains seal74in contact with ball42through the assistance of a seal follower78. Seal retainer76may be biased against one end of ball42due to resilient member53provided within a cavity defined by seal retainer76, seal follower78, and intermediate housing55. The resilient member53may be one or more wave springs for example. Placement of the resilient member53between the seal retainer76, seal follower78, and intermediate housing55allows for a more uniform continuous internal diameter through the formation isolation valve24. Additionally, this configuration may make formation isolation valve24more debris tolerant due to the separation of resilient member53from the general flow stream of an open ball42within the formation isolation valve24.

Additionally, a wiper80may be deployed against ball42to wipe the ball of debris as it is rotated and to thereby reduce the chance of debris preventing rotation of the ball. In the example illustrated, wiper80is a ring disposed on a side of ball42generally opposite seal retainer76. The seal74and wiper80cooperate to facilitate dependable and repeatable motion of ball42as an interior flow passage82is transitioned between an open flow configuration (as illustrated inFIG. 3) and a closed configuration in which the ball is rotated to block flow through an interior84of formation isolation valve24.

The wiper80may be formed from a variety of materials. For example, the wiper may be formed from polyetheretherketone (PEEK), brass, aluminum bronze, or other suitable materials. Additionally, the wiper80may be spring-loaded via an elastomeric material, a mechanical spring, or another suitable biasing member. The wiper80also may be formed as another seal to aid in preventing debris from entering the area surrounding ball42. Prevention of debris accumulation also may be facilitated with a ball section filler86deployed in otherwise empty space located between ball42and the surrounding valve housing58. By way of example, filler86may be formed from PEEK or another suitable material. The containment provided by seal74and wiper80enable arm or arms60to translate in an area generally sealed off from wellbore debris. It also should be noted that the locations of seal74and wiper80may be interchanged or otherwise altered to facilitate prevention of debris accumulation.

Referring generally toFIG. 4, another embodiment of formation isolation valve24is illustrated. In this embodiment, a seal system and wiper system may be employed in a manner similar to or the same as that illustrated and described with reference toFIG. 3. However, the technique for transmitting load from mandrel70to ball42has been altered. Instead of using yoke arms, one or more, e.g. two, rods88are coupled between mandrel70and ball42(only one rod88is shown in this simplified view). The rods88are simple structures that are easy to manufacture and easy to utilize in manipulating ball42. Each rod88is engaged with mandrel70via a connection mechanism90. In some embodiments, more than one rod88may use a single connection mechanism90. At an opposite end of each rod88, a slider mechanism92may be used to couple the rods to ball42.

By way of example, slider mechanism92connects the corresponding rod88to ball42at a position offset from the rotational axis50. The slider mechanism92may be designed to provide pivotable engagement between rod88and ball42to enable rotational movement of ball42when mandrel70moves in a linear direction to drive connection mechanism90. In this example, the rod88is able to pivot at both slider mechanism92and at connection mechanism90in order to accommodate rotation of ball42. As illustrated inFIG. 4, window66may be used in cooperation with connection mechanism90to limit the linear translation of connection mechanism90in a manner that ensures movement of ball42to between a closed position and an open flow position.

Well system20(FIG. 1) may be constructed to facilitate perforating operations, but the well system also may be designed for use in a variety of other well applications. For example, flow isolation valve system22(FIG. 1) may be employed in many types of well servicing and production applications. Accordingly, the components deployed downhole and the conveyance systems used to deploy and/or retrieve components may vary according to the specific well applications. Additionally, the shape, size, and orientation of the well may be different depending on the environment, the types of formations, and the types of fluids held in the formation.

Also, the formation isolation valve24may be designed from a variety of materials and in a variety of sizes and configurations. The isolation valve22(FIG. 1) may be attached to or constructed as part of other downhole equipment. Additionally, one or more formation isolation valves may be utilized in the overall well system. The arrangements of seals and/or wipers may vary according to the specific applications and environment in which the formation isolation valve is utilized. Similarly, the materials and structure of the ball and other valve components may be adjusted according to the specific application.

Elements of the embodiments have been introduced with either the articles “a” or “an.” The articles are intended to mean that there are one or more of the elements. The terms “including” and “having” are intended to be inclusive such that there may be additional elements other than the elements listed. The term “or” when used with a list of at least two elements is intended to mean any element or combination of elements.

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. Accordingly, such modifications are intended to be included within the scope of this invention as defined in the claims.