1. Field of Invention
The present invention is directed to apparatuses for restricting fluid flow through a conduit in oil and gas wells and, in particular, to apparatuses having one or more seal interface materials disposed between the sealing interface of a plug element with a seat so as to resist or retard corrosion of the sealing interface by a corroding fluid.
2. Description of Art
Ball seats are generally known in the art. For example, typical ball seats have a bore or passageway that is restricted by a seat. The ball or plug element is disposed on the seat, preventing or restricting fluid from flowing through the bore of the ball seat and, thus, isolating the tubing or conduit section in which the ball seat is disposed. As force is applied to the ball or plug element, the conduit can be pressurized for tubing testing or tool actuation or manipulation, such as in setting a packer. Alternatively, the isolated zone of the wellbore can be treated with a corroding fluid such as an acid. Ball seats are also used in cased hole completions, liner hangers, flow diverters, frac systems, and flow control equipment and systems.
Although the terms “ball seat” and “ball” are used herein, it is to be understood that a drop plug or other shaped plugging device or element may be used with the “ball seats” disclosed and discussed herein. For simplicity it is to be understood that the terms “ball” and “plug element” include and encompass all shapes and sizes of plugs, balls, darts, or drop plugs unless the specific shape or design of the “ball” is expressly discussed.
Broadly, the apparatuses for restricting fluid flow through a conduit or tubular member that are disclosed herein comprise a housing and a seat disposed therein. A seal interface material is disposed on or adjacent the seat and/or a plug element that is designed to land on the seat to restrict fluid flow through the tubular member. The seal interface material may be disposed on the plug element, the sealing surface of the seat, and/or above the sealing surface of the seat. As used herein, the term “sealing surface” refers to the contact area of the plug element with the seat. Thus, the seal interface materials is not required to be disposed directly between the seat and the plug element.
In certain embodiments, the seal interface material is resistant to corrosion by a corroding fluid such as acid or hydrogen sulfide. As used herein, the phrase “resistant to corrosion” refers to the ability of seal interface material to resist corrosion by the corroding fluid for a time period that is greater than the period of time necessary to corrode a seat or plug element that lacks the seal interface material.
While the invention will be described in connection with the preferred embodiments, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the invention as defined by the appended claims.
Referring now to
Seat member 40 comprises seat 42. In the embodiment of
In the embodiment of
In the embodiment of
Seal interface element 50 comprises a seal interface material that is resistant to corrosion by one or more fluids that may be present in bore 34, and in particular, in upper bore 35, when plug element 60 is disposed on seat 42. Suitable seal interface materials include nitrile rubber (“NBR”), hydrogenated nitrile rubber (“HNBR”), perfluoroelastomer (“FFKM”), and fluoroelastomers (“FKM,” “FEPM”) such as those sold under the trademark AFLAS® available from Asahi Glass Co., Ltd. of Tokyo, Japan, and under the trademark VITON® available from E. I. du Pont de Nemours and Company. NBR and ALFAS® branded fluoroelastomers are suitable for high acid environments, and HNBR and VITON® branded fluoroelastomers are suitable for high hydrogen sulfide environments.
In operation, ball seat 30 is secured to a work or tubing string (not shown) and lowered into the wellbore (not shown). A downhole tool (not shown) is disposed in the work string above ball seat 30. After being disposed within the wellbore at the desired depth or location, a plug element shown as plug element 60 is dropped down the tubing string until it enters upper bore 35 and lands on seat 42 of seat member 40 (
In one embodiment of operation, fluid, such as hydraulic fluid, is pumped down the tubing string causing downward force or pressure to act on plug element 60 to force plug element 60 into seat 42. The fluid pressure is then increased above plug element 60 until it reaches the actuation pressure of the downhole tool causing the downhole tool to perform its intended function, e.g., open a valve, set a packer, set a bridge plug, and the like.
Either after the downhole tool has performed its intended function, or during actuation of the downhole tool, a corroding fluid may be present in upper bore 35, either because it is included in the fluid being pumped down the tubing string, or because it entered into the tubing string from the formation. Generally, the corroding fluid corrodes or degrades plug element 60 until plug element 60 disintegrates, breaks apart, or is otherwise compromised such that a seal can no longer be maintained between plug element 60 and seat 42. To delay the amount of time for plug element 60 to be compromised by the corroding fluid, seal interface element 50 is disposed between plug element 60 and sealing surface 43 to restrict contact between the corroding fluid and sealing surface 43. Thus, sealing surface 43 maintains its integrity for a longer period of time as compared to no seal interface element 50 being present.
In another embodiment of operation, the fluid being pumped down the tubing string is an acid for acid treatment of the wellbore. In this embodiment, an acidic fluid is in constant contact with plug element 60 and seat member 40 causing corrosion of one or both of plug element 60 and seat member 40. Similar to the embodiment discussed in the preceding paragraph, seal interface element 50 is disposed between plug element 60 and sealing surface 43 to restrict contact between the acid and sealing surface 43 so that sealing surface 43 can maintain its integrity for a longer period of time as compared to no seal interface element 50 being present.
In another embodiment, the corroding fluid comprises hydrogen sulfide that corrodes one or both of plug element 60 or seat member 40. Thus, in this embodiment, seal interface element 50 is disposed between plug element 60 and sealing surface 43 to restrict contact between the hydrogen sulfide fluid and sealing surface 43 so that sealing surface 43 can maintain its integrity for a longer period of time as compared to no seal interface element 50 being present
It is to be understood that the invention is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. For example, the corroding fluid is not limited to acid or hydrogen sulfide, but can be any fluid present in a wellbore that undermines the integrity of the plug element or the seat member. Similarly, the material forming seal interface element 50 is not required to be an acid-retarding material, or a hydrogen sulfide-retarding material, but can be any other material suitable for retarding corrosion or degradation by the particular corroding fluid.
Additionally, although the apparatuses described in greater detail with respect to