Patent Description:
In general, a system and methodology are provided to facilitate pressure application downhole by locking a ball, e.g. a non-deformable ball, in place to prevent it from unseating even if the pressure is bled off. A ball seat is constructed with a locking feature for effectively capturing and retaining the ball once the ball is seated in the ball seat under sufficient pressure. According to an embodiment, the ball seat may be mounted at a desired position along an internal flow passage of a well string component. The ball seat comprises a throat section with an interior throat surface which tapers to a smaller diameter in a downhole direction, and which is formed of a ductile material arranged in a suitable structure to enable a desired deformation upon receiving the ball under sufficient pressure. As the ball is pressed into the throat section, the material of the throat section deforms but also partially springs back to resist movement of the ball in the uphole direction, thus capturing the ball in both the uphole direction and the downhole direction.

However, many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims.

Certain embodiments of the disclosure will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements. It should be understood, however, that the accompanying figures illustrate the various implementations described herein and are not meant to limit the scope of various technologies described herein, and:.

In the following description, numerous details are set forth to provide an understanding of some embodiments of the present disclosure. However, it will be understood by those of ordinary skill in the art that the system and/or methodology may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.

The disclosure herein generally involves a system and methodology for facilitating pressure application downhole. In well applications, well strings may be deployed downhole into a borehole, e.g. a wellbore, with completion equipment and/or other downhole equipment. The downhole equipment may comprise various types of tools which are selectively actuated hydraulically via pressure applied downhole through the well string. Examples of such hydraulically actuated tools include sliding sleeve devices which may be in the form of stage cementing collar sleeves, circulation port sleeves, fracturing sleeves, and/or other hydraulically actuated devices.

The increased pressure applied to actuate the desired downhole device or devices may be enabled by locking a ball in sealed engagement with a ball seat to prevent it from unseating even if the pressure is bled off. According to an embodiment, the ball seat may be constructed with a locking feature for effectively capturing and retaining the ball once the ball is seated in the ball seat under sufficient pressure. The ball seat may be mounted at a desired position along an internal flow passage of a well string/well string component. Additionally, the ball seat may comprise a throat section which is formed of a ductile material arranged in a suitable structure to enable a desired deformation upon receiving the ball under sufficient pressure. The arrangement of structure and material enables use of a non-deformable ball without detrimentally affecting the locking capability of the ball seat. As the ball is pressed into the throat section, the material of the throat section deforms but also partially springs back to resist movement of the ball in the uphole direction. Consequently, the ball is captured via the ball seat and locked against movement in both the uphole direction and the downhole direction.

As described in greater detail below, the throat section of the ball seat may be mounted between a ball entrance portion and a base portion in some embodiments. The ball entrance portion may have a variety of configurations to help guide the ball into the throat section which is deformed as the ball is moved through the ball entrance portion and forced into the throat section. The throat section has a diameter less than the diameter of the ball. Due to the structure and deformability of the throat section, the ball may be formed of a non-deformable material, such as aluminum alloy, aluminum bronze, phenolic, or other suitable material.

A non-deformable ball may be considered a ball which compresses less than <NUM>% in diameter (and in some embodiments less than <NUM>%) as it is forced into the throat section under pressure applied down through the well string. It also should be noted that the terms "ball" or "non-deformable ball" are used broadly to refer to items able to block flow along an internal passage. References made herein to "ball" or "non-deformable ball" are meant to include many types of devices having a variety of shapes and configurations, e.g. partial balls, darts, and various other plugs which may seal against a ball seat.

Depending on the parameters of a given application, the throat section may be formed of a ductile material which plastically deforms as the ball is forced into the throat section. In other words, the throat section is forced into a radially outward, expanded configuration by the ball to an extent which plastically deforms the material of the throat section. However, the ductile material is selected with sufficient spring back so that a portion of the throat section on an uphole side of the ball effectively springs back after passage of the ball. The spring back allows this portion of the throat section to transition back to a smaller diameter and thus trap the ball between a reduced radius (relative to the ball radius) on both an uphole side and downhole side of the ball. Accordingly, pressure may be released uphole of the ball without concern that the ball will become unseated with respect to the ball seat even in highly deviated, e.g. horizontal, boreholes.

Examples of ductile material which may be used to construct the throat section include aluminum alloys or steel alloys selected to have appropriate plastic deformability and sufficient spring back to capture the ball. In some embodiments, the throat section may be made out of the same material as the ball entrance portion and the base portion. However, the overall ball seat may be formed with multiple materials, e.g. composite materials. Use of certain materials e.g. aluminum alloys, helps ensure that the ball seat is drillable so that it may be drilled out after its use is completed.

Referring generally to <FIG>, an example of a well system <NUM> is illustrated for use in a downhole well application. For example, the well system <NUM> may be used in producing a well fluid, e.g. oil, from a subterranean formation <NUM>. According to an embodiment, the well system <NUM> comprises a well string <NUM> sized for deployment along a borehole <NUM>, e.g. a wellbore. In various applications, the borehole <NUM> may comprise a highly deviated, e.g. horizontal, borehole section <NUM> into which the well string <NUM> is deployed. In the illustrated example, the well string <NUM> may comprise a tubular section <NUM>, e.g. a tubular well component, having an interior surface <NUM> defining an internal flow passage <NUM>.

Additionally, a ball seat <NUM> may be mounted in the well string <NUM> along the internal flow passage <NUM> within tubular section <NUM>. By way of example, the ball seat <NUM> may be generally circular in cross-section extending about the interior of tubular section <NUM>. In some embodiments, the ball seat <NUM> may comprise a ball entrance portion <NUM> having a sloped surface <NUM> which slopes radially inwardly from interior surface <NUM> and in a generally downhole direction. As illustrated, the ball seat <NUM> also may comprise a base portion <NUM>. In the example illustrated, the base portion <NUM> securely mounts and seals the ball seat <NUM> to the tubular section <NUM>. However, the ball entrance portion <NUM> and/or other portions of ball seat <NUM> may be used to secure the ball seat <NUM> to the tubular section <NUM>.

Furthermore, the ball seat <NUM> may comprise a throat section <NUM> extending between the ball entrance portion <NUM> and the base portion <NUM>. An interior surface <NUM> of the throat section <NUM> defines an internal throat passage <NUM> which has a diameter smaller than the diameter of interior surface <NUM> and smaller than the diameter of a ball used to block flow along internal flow passage <NUM>, as explained in greater detail below. In some embodiments, the throat section <NUM> is constructed with a wall <NUM> which extends from ball entrance portion <NUM> to base portion <NUM> at a radially inward position from interior surface <NUM> so as to form a space <NUM> between the interior surface <NUM> and the throat section <NUM>.

According to some examples, the throat section <NUM> may be constructed such that interior surface <NUM> is cylindrical. In other applications, however, the throat section <NUM> may be constructed such that interior surface <NUM> has other profiles. For example, the interior surface <NUM> may be constructed with a sloped profile which tapers to a smaller diameter in a downhole direction as indicated by angle <NUM>. By way of example, the angle <NUM> may be less than <NUM>°, e.g. in the range of <NUM>-<NUM>°. It should be noted that throat section <NUM> may be constructed in a variety of configurations and may be utilized with various types of support structures, e.g. various types of base portions <NUM>, and with various types of entrance portions <NUM>. As explained in greater detail below, the throat section <NUM> is constructed to effectively serve as a locking feature which locks a ball in sealing engagement with the ball seat <NUM>.

Referring generally to <FIG>, an illustration is provided in which a ball <NUM> is dropped, e.g. pumped, down through an interior of the well string <NUM> and along internal flow passage <NUM> toward ball seat <NUM>. In this example, ball <NUM> is a non-deformable ball having a diameter larger than the diameter of internal throat passage <NUM>. When the ball <NUM> reaches ball seat <NUM>, it is guided to internal throat passage <NUM> via the sloped surface <NUM> of ball entrance portion <NUM> as illustrated in <FIG>.

As the ball <NUM> enters internal throat passage <NUM>, flow along internal flow passage <NUM> is blocked so that the pressure uphole of ball <NUM> may be increased. The increased pressure is used to force ball <NUM> along internal throat passage <NUM> and into throat section <NUM> as illustrated in <FIG>. The material and structure of throat section <NUM> may be selected to enable movement of ball <NUM> into throat section <NUM> under a desired pressure application along internal flow passage <NUM>.

By way of example, the pressure applied to shift ball <NUM> into throat section <NUM>, as illustrated in <FIG>, may be in the range of <NUM> MPa (<NUM> psi (pounds per square inch)) to <NUM> MPa (<NUM>,<NUM> psi). In some applications, the pressure applied to shift ball <NUM> into throat section <NUM> is selected from within the range of <NUM> MPa to <NUM> MPa (<NUM> psi to <NUM> psi). However, other suitable pressures or pressure ranges may be selected for shifting ball <NUM> to a locked position in throat section <NUM> depending on the materials and configuration of ball seat <NUM>.

In the illustrated example, ball <NUM> is constructed from a non-deformable material and throat section <NUM> is constructed from a ductile material, e.g. an aluminum alloy, which deforms as ball <NUM> moves into throat section <NUM> to create a region of deformation <NUM> (see also <FIG>). For example, wall <NUM> of throat section <NUM> may deform in a radially outward direction. However, the ductile material has sufficient spring back such that an uphole portion <NUM> of throat section <NUM> springs back to a relatively smaller diameter (compared to a diameter <NUM> of ball <NUM>) to prevent the ball <NUM> from shifting back in an uphole direction. Simultaneously, movement of the ball <NUM> into throat section <NUM> and the resultant deformation of throat section <NUM> creates a downhole portion <NUM> which remains at a relatively smaller diameter compared to diameter <NUM> of ball <NUM>. The downhole portion <NUM> may be buttressed by base <NUM>. As a result, the ball <NUM> is trapped and restricted from further movement in either an uphole direction or a downhole direction even after pressure has been released in internal flow passage <NUM>. The portions <NUM>, <NUM> effectively serve as a locking feature to lock ball <NUM> in seated engagement with throat section <NUM>.

In various embodiments, the material of throat section <NUM> is selected to undergo plastic deformation as ball <NUM> is forced along internal throat passage <NUM> into throat section <NUM>. The plastic deformation in, for example, deformation region <NUM> is useful in ensuring retention of the ball <NUM>. However, the material of throat section <NUM> retains sufficient spring back to enable creation of uphole portion <NUM> after passage of ball <NUM>, thus trapping the ball <NUM>.

In a specific example, movement of a non-deformable ball <NUM> into throat section <NUM> causes radial expansion of the throat section wall <NUM> into space <NUM> to a sufficient degree that the material of throat section <NUM> undergoes plastic deformation. At the same time, however, the downhole portion <NUM> remains and the uphole portion <NUM> is created via the spring back of the throat material. Consequently, the ball <NUM> becomes trapped and effectively locked against movement downhole via portion <NUM> or uphole via portion <NUM> even when pressure in well string <NUM> is released. In some embodiments, the base portion <NUM> of ball seat <NUM> is formed as a non-expandable section having a smaller inside diameter than the diameter <NUM> of ball <NUM> so as to ensure downhole portion <NUM> remains to resist movement of ball <NUM> past the ball seat <NUM>.

Referring generally to <FIG>, another embodiment of ball seat <NUM> is illustrated. In this example, the throat section <NUM> is constructed to facilitate the capture and retention of a plurality of balls <NUM>, e.g. two balls <NUM>, along the interior surface <NUM>. As illustrated, the throat section <NUM> is constructed with a plurality of different diameters which are each slightly smaller than the diameter of the corresponding ball <NUM> to be captured and locked in place.

With this type of throat section <NUM>, the interior surface <NUM> may be constructed with a stepped profile <NUM> which has a plurality of steps <NUM> to establish appropriate diameters for capturing balls of different diameters. According to the example illustrated, the steps <NUM> are constructed to capture two differently sized balls <NUM>, but additional steps <NUM> may be added for capturing additional balls <NUM>. The plurality of differently sized balls <NUM> which may be seated enables a plurality of sequential pressure applications separated by flow through capability.

Accordingly, the throat section <NUM> may be constructed to enable application of sufficient pressure to force at least the initial ball through the ball seat <NUM> to enable flow along internal flow passage <NUM>. Subsequently, the flow along passage <NUM> may again be blocked by dropping another ball <NUM> (a larger diameter ball) for engagement with a larger diameter step <NUM>. Each step <NUM> is able to deform, e.g. plastically deform, and form its own deformation region <NUM> for locking in place the corresponding ball <NUM>.

Referring generally to <FIG>, another embodiment is illustrated in which the ball seat <NUM> is used in conjunction with a specific downhole tool <NUM>. By way of example, the downhole tool <NUM> may comprise a sliding sleeve <NUM> which may be shifted to different operational positions via application of pressure in internal flow passage <NUM>. In some embodiments, the ball seat <NUM> may be used in cooperation with ball <NUM>, as described above, to enable application of pressure along the interior of well string <NUM> so as to actuate a suitable hydraulic piston for shifting the sliding sleeve <NUM> (or other type of actuatable downhole tool <NUM>).

In the illustrated example, however, the ball seat <NUM> is mounted to the sliding sleeve <NUM> along the interior of sliding sleeve <NUM>. When ball <NUM> is seated and locked in throat section <NUM>, pressure may be increased along the interior of the well string <NUM> to enable shifting of the sliding sleeve <NUM> in a downhole direction. The ball seat <NUM> and ball <NUM> are simply shifted along with the sliding sleeve <NUM>. For example, the sliding sleeve <NUM> may be shifted from a closed position (see <FIG>) to an open position (see <FIG>) allowing flow through one or more side ports <NUM> in tubular section <NUM>. In this example, the side ports <NUM> extend through a wall forming tubular section <NUM> to enable fluid communication between an exterior and an interior of the tubular section <NUM>.

Referring generally to <FIG>, another embodiment of ball seat <NUM> is illustrated. In this example, the ball seat <NUM> comprises wall <NUM> of throat section <NUM> formed as a corrugated pipe <NUM>. The corrugated pipe <NUM> provides interior surface <NUM> with corrugations/undulations <NUM> oriented to help grip the ball <NUM>. In a similar embodiment, the wall <NUM> is not formed as a corrugated pipe with corrugations on both an interior and an exterior but instead simply provides the corrugations/undulations <NUM> along interior surface <NUM>, as illustrated in <FIG>.

Referring generally to <FIG>, another embodiment of ball seat <NUM> is illustrated as having interior surface <NUM> of throat section <NUM> formed with teeth <NUM>. The teeth <NUM> may be arranged along the interior of throat section <NUM> to facilitate gripping of ball <NUM>. Teeth <NUM> may be constructed in various patterns, sizes and configurations depending on the parameters of a given application. By way of example, teeth <NUM> may have an asymmetrical profile <NUM>, e.g. an asymmetrical triangular profile, as illustrated in <FIG>. According to another example, the teeth <NUM> may have a symmetrical profile <NUM>, e.g. a symmetrical triangular profile, as illustrated in <FIG>. However, teeth <NUM> may be formed in various other symmetrical and asymmetrical shapes and configurations.

Depending on the parameters of a given application, environment, and equipment utilized, the ball seat <NUM> may be used as part of various types of completion equipment or other downhole equipment. In a variety of applications, the ball seat <NUM> is constructed to plastically deform as a non-deformable ball <NUM> is forced into the ball seat throat section <NUM> while allowing sufficient spring back to capture the ball. This allows the use of a conventional, non-deformable ball <NUM>. However, various other types of balls, including deformable balls, can be used with the ball seat <NUM> for at least some applications.

The ball seat <NUM> may be a fixed element in a tubular section, e.g. a liner, or it may be mounted as part of a sliding sleeve or other shiftable component. Additionally, the ball seat <NUM> may be constructed from various aluminum alloys, composite materials, and/or other materials which provide the capability for plastic deformation and sufficient spring back. The specific alloys/materials selected may vary depending on the environment in which the ball seat <NUM> is used, the type of corresponding equipment, and the pressures to be applied for a given operation.

Claim 1:
A system for use in a well, comprising:
a well string (<NUM>) sized for deployment along a borehole (<NUM>), the well string (<NUM>) having a tubular section (<NUM>) with an interior surface (<NUM>) defining an internal flow passage (<NUM>); and
a ball seat (<NUM>) mounted in the well string (<NUM>) along the internal flow passage (<NUM>), the ball seat (<NUM>) comprising:
a ball entrance (<NUM>, <NUM>) sloping radially inwardly from the interior surface (<NUM>);
a base (<NUM>); and
a throat section (<NUM>)
characterised in that the throat section has an interior throat surface (<NUM>) which tapers to a smaller diameter in a downhole direction, the throat section extending between the ball entrance (<NUM>, <NUM>) and the base (<NUM>) to form a space (<NUM>) between the interior surface (<NUM>) and the throat section (<NUM>), the throat section (<NUM>) being formed of a ductile material which is plastically deformable such that the throat section (<NUM>) expands radially outwardly when receiving a ball (<NUM>) with a larger diameter than the throat section (<NUM>), the ductile material having sufficient spring back to capture the ball (<NUM>) on both an uphole (<NUM>) and a downhole (<NUM>) side.