Slip assembly for a downhole tool

A slip assembly includes a first segment, a second segment that is circumferentially offset from the first segment, and a connector positioned circumferentially between the first and second segments. The connector couples the first and second segments together, and wherein a length of the connector is from about 50% to about 100% of a length of the first segment.

BACKGROUND

Packers, bridge plugs, frac plugs, and other downhole tools may be deployed into a wellbore and set in place to isolate two zones from one another in the wellbore. Generally, such setting is accomplished using a system of slip assemblies and cones. A setting tool is used to axially compress the slip assemblies and cones along a mandrel. The slip assemblies may include a plurality of circumferentially offset segments that are coupled together. As the slip assemblies ride up the tapered surfaces of the cones during axial compression, the radial outward force on the slip assemblies may cause the segments to break apart from one another. The segments may then move farther in the radial outward direction and into engagement with a surrounding tubular (e.g., a casing or the wellbore wall itself). This causes the segments to bite into the surrounding tubular, thereby holding the downhole tool in place. However, oftentimes, a pressure of a fluid between the cones and the slip assemblies may exert a force on the slip assemblies in a radially outward direction, which may cause the segments of the segments to break apart prematurely.

SUMMARY

Embodiments of the disclosure may provide a slip assembly that includes a first segment, a second segment that is circumferentially offset from the first segment, and a connector positioned circumferentially between the first and second segments. The connector couples the first and second segments together, and wherein a length of the connector is from about 50% to about 100% of a length of the first segment.

Embodiments of the disclosure may also provide a slip assembly including a plurality of segments that are circumferentially offset from one another. Each segment includes a first axial end and a second axial end. A thickness of the first axial end of each segment is greater than a thickness of the second axial end of each segment. The slip assembly also includes a connector positioned between a first of the segments and a second of the segments. A length of the connector is from about 50% to about 100% of a length of the first segment, and the connector is configured to break in response to a predetermined axial compression force.

Embodiments of the disclosure may further provide a slip assembly including a plurality of segments that are circumferentially offset from one another. Each segment includes a first axial end and a second axial end, a thickness of the first axial end of each segment is greater than a thickness of the second axial end of each segment, and an outer surface of a first of the segments defines a plurality of openings that are configured to at least partially receive inserts. The slip assembly also includes a connector positioned between the first segment and a second of the segments. The first segment, the second segment, and the connector are a monolithic component made at least partially of a phenolic material or magnesium, a length of the connector is from about 90% to about 100% of a length of the first segment, an outer surface of the connector is substantially flat and recessed from outer surfaces of the first and second segments by a first distance, an inner surface of the connector is curved and recessed from inner surfaces of the first and segments by a second distance, the first distance is less than the second distance, and a thickness of the connector is substantially constant proceeding in an axial direction.

DETAILED DESCRIPTION

The following disclosure describes several embodiments for implementing different features, structures, or functions of the invention. Embodiments of components, arrangements, and configurations are described below to simplify the present disclosure; however, these embodiments are provided merely as examples and are not intended to limit the scope of the invention. Additionally, the present disclosure may repeat reference characters (e.g., numerals) and/or letters in the various embodiments and across the Figures provided herein. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed in the Figures. Moreover, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the first and second features, such that the first and second features may not be in direct contact. Finally, the embodiments presented below may be combined in any combination of ways, e.g., any element from one exemplary embodiment may be used in any other exemplary embodiment, without departing from the scope of the disclosure.

Additionally, certain terms are used throughout the following description and claims to refer to particular components. As one skilled in the art will appreciate, various entities may refer to the same component by different names, and as such, the naming convention for the elements described herein is not intended to limit the scope of the invention, unless otherwise specifically defined herein. Further, the naming convention used herein is not intended to distinguish between components that differ in name but not function. Additionally, in the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to.” All numerical values in this disclosure may be exact or approximate values unless otherwise specifically stated. Accordingly, various embodiments of the disclosure may deviate from the numbers, values, and ranges disclosed herein without departing from the intended scope. In addition, unless otherwise provided herein, “or” statements are intended to be non-exclusive; for example, the statement “A or B” should be considered to mean “A, B, or both A and B.”

In general, embodiments of the present disclosure may provide a slip assembly for a downhole tool. The downhole tool may be or include a packer, a bridge plug, a frac plug, or the like. The slip assembly may include a plurality of segments that are circumferentially offset from one another. Each circumferentially adjacent pair of segments may be coupled together by a connector or “web.” The connector may extend axially along a length that is from about 50% to about 100% of the axial length of the segments. As described in greater detail below, the design of the connector may allow the connector to break apart by axial compression of the slip assembly against a cone when the downhole tool is in a desired location (e.g., in a wellbore). However, the design of the connector may prevent the connector from breaking apart prematurely (e.g., before the axial compression).

FIG. 1illustrates a perspective view of a slip assembly100, according to an embodiment. The slip assembly100may be used in, or otherwise a part of, a downhole tool such as a packer, a bridge plug, a frac plug, or the like, without limitation. The slip assembly100may be made of a composite material. For example, the composite material may be or include a fiber-reinforced material such as a phenolic material. In another embodiment, the slip assembly100may be made of a metallic material. For example, the slip assembly100may be made of magnesium which may be configured to degrade of dissolve in a predictable manner in a wellbore environment.

The slip assembly100may be annular and include a first axial end110and a second axial end112. A length130of the slip assembly100may be defined between the first and second ends110,112(e.g., excluding castellations of the slip assembly100, if present, as shown). The length130of the slip assembly100is shown more clearly inFIG. 4. The slip assembly100may also include a plurality of segments (six are shown:120) that are circumferentially offset from one another. It will be appreciated that any number of segments120may be included in various embodiments of the slip assembly100.

Each pair of circumferentially adjacent segments120may be coupled/held together by a connector or “web” (six are shown:140). The connectors140may extend a majority of the length130of the slip assembly100. For example, a length of the connectors140may be from about 50% to about 100% of the length130of the slip assembly100, about 60% to about 100% of the length130of the slip assembly100, about 70% to about 100% of the length130of the slip assembly100, about 80% to about 100% of the length130of the slip assembly100, about 90% to about 100% of the length130of the slip assembly100, or about 100% of the length130of the slip assembly100.

Although a single connector140is shown coupling each pair of circumferentially adjacent segments120, in other embodiments, a plurality of connectors140may be used to couple each pair of circumferentially adjacent segments120, such that two or more connectors140may be axially offset from one another. In this embodiment, the aggregate length of the connectors140used to couple each pair of circumferentially adjacent segments120may fall within the range(s) provided above, and/or one of the connectors140may be in the disclosed range of axial length, and the other may be smaller.

Having the connectors140extend a majority of the length of the slip assembly100may reduce the likelihood that the connectors140will break prematurely. This may help to prevent the segments120from separating from one another (e.g., in a wellbore) before the downhole tool is in the desired location and ready to be set. In particular, the connectors140may prevent the axial end of the slip assembly100from bending outward or “flowering” during the run-in process. By comparison, some conventional slip assemblies that include a bridge between adjacent slips only at an axial end may allow for such flowering, which is considered to cause premature setting of downhole tools in the well. Furthermore, the present slip assembly100design may have a design that is more efficient to mill from a cast blank.

The slip assembly100may also define a plurality of holes122. For example, each segment120may have a plurality of holes122extending radially therethrough (i.e., from an outer radial surface124to an inner radial surface126). In another embodiment, the holes122may extend only partially radially therethrough (i.e., from the outer radial surface124toward, but not all the way to, the inner radial surface126). In at least one embodiment, the depth of the holes122may vary. For example, the holes122proximate to the first axial end110may be deeper than the holes122proximate to the second axial end112, or vice versa.

Although not shown, the holes122may be configured to receive inserts, which are sometimes referred to as “buttons.” Such inserts may be formed from material (e.g., carbide) that is harder than the material of the slip assembly100. The inserts may thus bite (e.g., partially embed) into the surrounding tubular when the slip assembly100is set. The holes122and the inserts may be oriented at angles to resist the slip assembly100losing gripping force and being displaced from engagement with the surrounding tubular when the pressure differential across the downhole tool reverses.

FIG. 2illustrates an axial end view of the slip assembly100, andFIG. 3illustrates an enlarged view of a portion ofFIG. 2, according to an embodiment. As mentioned above, the slip assembly100may be annular and thus define an axial bore102. In at least one embodiment, the slip assembly100may be a single (e.g., integral, unitary, monolithic, etc.) component made/cast from the same material (e.g., magnesium or another metal, or a phenolic composite material, etc.). Thus, as noted above, the connectors140may be made of the same material as the segments120.

In at least one embodiment, the connectors140may be formed by removing material from the slip assembly100between two circumferentially adjacent segments120. The material may be removed by machining, milling, grinding, scraping, etc. At least a portion of the material may be removed proceeding radially-inwardly (e.g., using a first tool) such that outer surfaces144of the connectors140are recessed with respect to outer surfaces124of the adjacent segments120. The end of the first tool may be flat such that the outer surfaces144of the connectors140may be substantially flat. The depth of the radially-inwardly extending recesses148may be from about 0.08 inches to about 0.12 inches or from about 0.094 inches to about 0.099 inches.

At least a portion of the material may also or instead be removed proceeding radially-outwardly (e.g., using a second tool) such that inner surfaces146of the connectors140are recessed with respect to inner surfaces126of the adjacent segments120. The end of the second tool may be curved such that the inner surfaces146of the connectors140may also be curved. The depth of the radially-outwardly extending recesses150may be from about 0.3 inches to about 0.8 inches or about 0.4 inches to about 0.7 inches.

Due to the curved inner surfaces146of the connectors140, a thickness152of each connector140may vary proceeding in a circumferential direction. For example, the thickness152of the connectors140may be at a minimum value at a circumferential midpoint of each connector140, and the thickness152may increase proceeding circumferentially away from the midpoint in one or both circumferential directions. A width154of the connectors140may be substantially equal to a width of the recesses148and/or the recesses150. The width154may be from about 0.15 inches to about 0.25 inches or about 0.17 inches to about 0.21 inches.

FIG. 4illustrates a cross-sectional view of the slip assembly100taken through line4-4inFIG. 2, according to an embodiment. As mentioned above, the length130of the slip assembly100may be defined between the first and second ends110,112. The length130may be from about 1.75 inches to about 2.75 inches or from about 2.0 inches to about 2.3 inches.

A thickness132of the segments120(i.e., between the outer surface124and the inner surface126) may vary proceeding from the first end110to the second end112. As shown, the thickness132may remain substantially constant from the first end110proceeding axially to an intermediate point111. Thus, a (e.g., radial) distance between a central longitudinal axis of the slip assembly100and the inner surface126may remain substantially constant from the first end110proceeding axially to the intermediate point111. The thickness132may then decrease from the intermediate point111proceeding axially to the second end112. Thus, the distance between the central longitudinal axis of the slip assembly100and the inner surface126may increase from the intermediate point111proceeding axially to the second end112.

FIG. 5illustrates a cross-sectional view of the slip assembly100taken through line5-5inFIG. 2, according to an embodiment. As shown, the thickness152of the connector140may be substantially constant proceeding in an axial direction (i.e., between the first and second ends110,112of the slip assembly100), even though the thickness132of the segments120may vary. For example, the (e.g., minimum value of the) thickness152of the connectors140may be from about 0.01 inches to about 0.1 inches, about 0.01 inches to about 0.075 inches, or 0.01 inches to about 0.06 inches.

In at least one embodiment, the thickness152of the connectors140may depend at least partially on the material from which the slip assembly100is made. For example, if the slip assembly100is made of metal (e.g., magnesium), the thickness152of the connectors140may be toward the lower end of the ranges provided above (e.g., from about 0.01 inches to about 0.03 inches). If the slip assembly100is made from a composite material (e.g., phenol), the thickness152of the connectors140may be toward the upper end of the ranges provided above (e.g., from about 0.05 inches to about 0.08 inches).

FIG. 6illustrates a perspective view of a downhole tool (e.g., a plug)600including two slip assemblies100A,100B, according to an embodiment. The downhole tool600may include a mandrel610. One or more components may be positioned at least partially around the mandrel610and/or coupled to the mandrel610. In the example shown, the components may include a load ring620, the first and second slip assemblies100A,100B, first and second cones630A,630B, one or more sealing elements640, and a shoulder or shoe650.

The downhole tool600may be actuated from a run-in state to a set state by a setting tool (e.g., a wireline adapter kit). When the downhole tool600is actuated, the mandrel610is held stationary and/or pulled in a first (e.g., uphole) direction, while the load ring620is pushed in a second (e.g., downhole) direction. This causes the load ring620to move with respect to the mandrel610. As a result, the first and second slip assemblies100A,100B, the first and second cones630A,630B, and/or the sealing element640may be axially-compressed between the load ring620and the shoulder or shoe650. The axial compression may cause the slip assemblies100A,100B to slide up the tapered outer surfaces of the cones630A,630B, which may exert a radially outward force on the slip assemblies100A,100B. When this force exceeds a predetermined amount, the connectors140break, causing the segments120to separate from one another, as discussed above.

As used herein, the terms “inner” and “outer”; “up” and “down”; “upper” and “lower”; “upward” and “downward”; “above” and “below”; “inward” and “outward”; “uphole” and “downhole”; and other like terms as used herein refer to relative positions to one another and are not intended to denote a particular direction or spatial orientation. The terms “couple,” “coupled,” “connect,” “connection,” “connected,” “in connection with,” and “connecting” refer to “in direct connection with” or “in connection with via one or more intermediate elements or members.”