Not applicable.
1. Field of the Invention
The described embodiments and claimed invention relate to a tool for sequentially engaging and releasing a restrictor element onto and from its corresponding valve seat, as well as systems and methods incorporating such a tool for producing hydrocarbons from multiple stages in a hydrocarbon production well.
2. Background of the Art
In hydrocarbon wells, tools incorporating valve assemblies having a restrictor element such as a ball or dart and a seat element such as a ball seat or dart seat have been used for a number of different operations. Such valve assemblies prevent the flow of fluid past the assembly and, with the application of a desired pressure, can actuate one or more tools associated with the assembly.
One use for such remotely operated valve assemblies is in fracturing (or “fracing”), a technique used by well operators to create and/or extend one or more cracks, called “fractures” from the wellbore deeper into the surrounding formation in order to improve the flow of formation fluids into the wellbore. Fracing is typically accomplished by injecting fluids from the surface, through the wellbore, and into the formation at high pressure to create the fractures and to force them to both open wider and to extend further. In many case, the injected fluids contain a granular material, such as sand, which functions to hold the fracture open after the fluid pressure is reduced.
Fracing multiple-stage production wells requires selective actuation of valve assemblies, such as fracing sleeves, to control fluid flow from the tubing string to the formation. For example, U.S. Published Application No. 2008/0302538, entitled Cemented Open Hole Selective Fracing System and which is incorporated by reference herein, describes one system for selectively actuating a fracing sleeve that incorporates a shifting tool. The tool is run into the tubing string and engages with a profile within the interior of the valve. An inner sleeve may then be moved to an open position to allow fracing or to a closed position to prevent fluid flow to or from the formation.
That same application describes a system using multiple valve assemblies which incorporate ball-and-seat seals, each having a differently-sized ball seat and corresponding ball. Frac valves connected to ball and seat seals do not require the running of a shifting tool thousands of feet into the tubing string and are simpler to actuate than frac valves requiring such shifting tools. Such ball and seat seals are operated by placing an appropriately sized ball into the well bore and bringing the ball into contact with a corresponding ball seat. The ball engages on a sealing section of the ball seat to block the flow of fluids past the valve assembly. Application of pressure to the valve assembly causes the valve assembly to “shift”, opening the frac sleeve.
Some valve assemblies are selected for tool actuation by the size of ball or other restrictor element introduced into the well. If the well or tubing string contains multiple ball seats, the ball must be small enough that it will not seal against any of the ball seats it encounters prior to reaching the desired ball seat. For this reason, the smallest ball to be used for the planned operation is the first ball placed into the well or tubing and the smallest ball seat is positioned in the well or tubing the furthest from the wellhead. Thus, these traditional valve assemblies limit the number of valves that can be used in a given tubing string because each ball size is only able to actuate a single valve. Further, systems using these valve assemblies require each ball to be at least 0.125 inches larger than the immediately preceding ball. Therefore, the size of the liner restricts the number of valve assemblies with differently-sized ball seats. In other words, because a ball must be larger than its corresponding ball seat and smaller than the ball seats of all upwell valves, each ball can only seal against a single ball seat and, if desired, actuate one tool.
The valve assembly provides a method for sequentially sealing multiple valve seats with a single restrictor element and, where desired, actuating tools associated with the valve assembly. One embodiment allows multiple balls of the same size to actuate tools in sequential stages.
The valve assembly described herein comprises a C-ring (also called a split ring) having a body with a seating surface, opposing terminal ends, and an external diameter extending radially from the body. The C-ring may be compressed such that terminal ends of the C-ring are in contact. In addition, the C-ring may be in an uncompressed state wherein the terminal ends are not in contact. The valve assembly further comprises one or more mounting elements to engage the outer diameter of the split ring. Engagement of mounting elements with the outer diameter causes the split ring to expand or contract.
Valve assemblies as described herein may further comprise a sleeve contained within a tubular housing, the sleeve having an inner surface, an outer surface, and a plurality of openings extending between said inner and outer surfaces. The openings are aligned to engage with the external diameter of the split ring. The tubular housing may have one or more mounting elements aligned within the openings in the sleeve, such that the mounting elements may engage the external diameter of the split ring when the sleeve is located at a desired position in the housing.
When used with reference to the figures, unless otherwise specified, the terms “upwell,” “above,” “top,” “upper,” “downwell,” “below,” “bottom,” “lower,” and like terms are used relative to the direction of normal production and/or flow of fluids and or gas through the tool and wellbore. Thus, normal production results in migration through the wellbore and production string from the downwell to upwell direction without regard to whether the tubing string is disposed in a vertical wellbore, a horizontal wellbore, or some combination of both. Similarly, during treatment of a well, which may include a fracturing, or “fracing,” process, fluids move from the surface in the downwell direction to the portion of the tubing string within the formation to be treated.
The housing 22 has a first cylindrical inner surface 30 having a first inner diameter, a second cylindrical inner surface 32 located downwell of the first inner surface 30 and having a second inner diameter that is greater than the first inner diameter, and a third cylindrical inner surface 34 having a third inner diameter that is greater than the second cylindrical inner surface 32. The first inner surface 30 is longitudinally adjacent to the second inner surface 32, forming a downwell-facing shoulder having an annular shoulder surface 38. The second and third inner surfaces 32, 34 are separated by a partially-conical surface 40.
The bottom connection 24 includes a first cylindrical inner surface 42 having a first inner diameter and a second cylindrical inner surface 44 having a second inner diameter. The first and second inner cylindrical surfaces 42, 44 are separated by an inner partially-conical inner surface 46. An annular upper end surface 47 is adjacent to the first inner surface 42.
The tool 20 comprises an annular sleeve 48 nested radially within the housing 22 and positioned downwell of the shoulder 38. The sleeve 48 has an upper outer surface 50 with a first outer diameter and a second outer surface 52 with a second outer diameter less than the first inner diameter. The first outer surface 50 and second outer surface 52 are separated by an annular shoulder surface 54. The sleeve 48 further comprises a cylindrical inner surface 56 that extends between annular upper and lower end surfaces 58, 60 of the sleeve 48.
In
The valve assembly may further comprise a guide element to position the split ring in the desired location. The guide element in the embodiment of
In the embodiment illustrated by the figures, the C-ring 70 is positioned within the annular sleeve 48 between the upper end surface 58 and the shoulder surface 54. The C-ring 70 fits into a groove formed in the inner surface 56 of the shifting sleeve 48. The groove is sufficiently deep to allow the C-ring seating surface to expand to the desired maximum diameter. In some embodiments, the desired maximum diameter may be as large as or larger than the inner diameter of the shifting sleeve. Those of skill in the art will appreciate that, in embodiments in which the C-ring activates a sleeve or other valve assembly, the C-ring 70 may be positioned at any point along the sleeve or tool, or above or below the sleeve, provided that the C-ring and the sleeve or other tool are connected such that sufficient pressure applied to the C-ring will slide the sleeve in relation to the inner housing or otherwise activate the tool.
The C-ring 70 has an inner surface 74 an outer surface 76 defining the outer perimeter of the C-ring, and a seating surface 72 engagable with a restrictor element having a corresponding size. In the illustrated embodiment, the C-ring 70 is held in a radially compressed state by the first inner surface 50 of the housing 22.
Referring to the embodiment in
Referring to
When the sleeve 48 is in the second position shown in
Each tool of the sets of the tools 202, 206, 210 has the features described with reference to
To actuate the lower set of tools 210, the lower-stage ball is caused to move through the tubing string and upper and intermediate sets of tools 202, 206. The lower-stage ball is sized to pass through the upper and intermediate sets of tools 202, 206 without being inhibited from further downwell flow by the corresponding ball seat inserts.
Upon reaching the upwell tool 210a of the lower set of tools 210, the lower-stage ball seats against the closed C-ring of the tool. The well operator can then increase the pressure within the tubing string to overcome the expansive force of the associated coil spring and shift the sleeve to the intermediate third position described with reference to
While the lower set of tools is shown comprising only three stages of tools, the process could be repeated for any number of tools within this stage. In addition, the same process described above with respect to the lower set of tools is repeatable in similar fashion for the intermediate and upper sets of tools 202, 206.
In an additional embodiment, the inwardly directed force exerted on the outer surface of the C-ring is caused by a plurality of dogs. In a preferred embodiment, the dogs are positioned in the openings 84 of the sleeve, and each dog has a surface corresponding to the curvature of the second inner surface 50 of the housing 22. The surface profile of the dogs may have other shapes provided the dogs can engage the protrusions 78 defining the outer surface of the C-ring 70 as desired. The dogs are aligned with and adapted to contact and exert a radially inward force on the protrusions 78 of the C-ring 70 to force the C-ring 70 into the compressed state. In this embodiment, the openings 84 have a length along the longitudinal axis of the sleeve to allow the C-ring and sleeve to move in relation to the dogs.
The dogs extend past first outer surface 50 of the sleeve 48, effectively reducing the diameter available to the protrusions. When the C-ring 70 is positioned such that that protrusions 78 engage the dogs, the terminal ends 82 are in contact and the diameter of the seating surface 72 and inner surface 74 of the C-ring 70 are such that a properly-sized ball flowing through the shifting sleeve will engage with the seat of the C-ring 70 as described with reference to
Still referring to
One advantage to the system illustrated in
This arrangement can be continued with any number of valve assemblies in series per stage, with no limit on the number of sleeves. Moreover, this system allows for an increase in the number of stages. For example, a trio of tools using single valve seats configured for a 2.0 inch, 1.875 inch, and 1.75 inch ball respectively, can be placed in a well. A second trio of tools using double valve seats with upper valves configured for use with 2.0 inch, 1.875 inches, and 1.75 inches are then placed upwell of the first trio. The upper valve seats of this second trio of stages are C-rings in the uncompressed state (as described with referenced with respect to
In operation, a first 1.75 inch ball is placed in the well and allowed to engage and activate the 1.75 inch stage of the first trio of stages. A first 1.875 ball is placed in the well and allowed to engage and activate the 1.875 inch stage of the first trio of stages. Following the 1.875 inch ball, a first 2.0 inch ball is placed in the well. This ball first engages the lower seat of the 2.0 inch stage of the second trio of stages causing the seat to shift and moving the upper ring from an uncompressed state to a compressed state. The first 2.0 ball then engages the lower seat of the 1.875 inch stage of the second trio of stages, causing the seat to shift and moving the upper ring from an uncompressed to a compressed state. The first 2.0 inch ball then engages the lower seat of the 1.75 inch stage of second trio of stages, causing the seat to shift and moving the upper ring from an uncompressed state to a compressed state. Finally, the first 2.0 inch ball engages the 2.0 inch stage of the first trio of stages and activates the tools associated with the valve assemblies of this stage.
At this point, three stages, associated with a 1.75 inch, a 1.875 inch, and a 2.0 inch valve assembly have been activated. Further, the well now contains three additional stages that can be activated by sequentially placing a 1.75 inch ball, a 1.875 inch ball, and 2.0 inch ball into the well and allowing the balls to engage their respective seats. This means that 6 stages, each stage having the potential for multiple sleeves, can be activated through use of 3 ball sizes. Further, the embodiments are not limited to the nesting of three sizes. Further nesting is possible with the valve assemblies and method of use contemplated herein, such nesting limited only by the ability of the uncompressed ring to allow larger sized balls to pass without shifting the seat.
It is possible that the lower seat is not a C-ring but rather a solid seat for the ball or other restrictor means. Such a solid seat can be paired with the applicants' resilient deformable ball, described in applicant's U.S. patent application Ser. No. 13/423,154, entitled “Downhole System and Apparatus Incorporating Valve Assembly With Resilient Deformable Engaging Element,” filed Mar. 16, 2012 and incorporated by reference herein, to allow for engagement and subsequent release of the lower seat. In fact, any method or device for engaging the lower seat to initially shift the sleeve is permissible provided that it does not prevent the treatment of any previously untreated stage.
The ball or other restrictor devices of the present valve assemblies can either seat on the C-ring itself or the inside diameter of the sleeve above the C-ring, where the sleeve is sized sufficiently small such that the ball creates an interference seal between the ball and sleeve, in which case the C-ring provides only the mechanical restriction required to impart a load on the sleeve for shifting.
This specification contains description of preferred embodiments in which a specific system and apparatus are described. Those skilled in the art will recognize that alternative embodiments of such system and apparatus can be used. Other aspects and advantages of the embodiments the invention as claimed may be obtained from a study of this disclosure and the drawings, along with the appended claims. Moreover, the recited order of the steps of any method described herein is not meant to limit the order in which those steps may be performed.
This original nonprovisional application claims the benefit of U.S. Provisional Application Ser. No. 61/453,288, filed Mar. 16, 2011 entitled “Multistage Production System Incorporating Valve assembly With Collapsible or Expandable Split Ring,” and U.S. Provisional Application 61/475,333 filed Apr. 14, 2011 entitled “Valve Assembly and System for Producing Hydrocarbons”, each of which is incorporated by reference herein.
Number | Date | Country | |
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61453288 | Mar 2011 | US | |
61475333 | Apr 2011 | US | |
61453281 | Mar 2011 | US |