Patent Application
20090308614
1. Field of Invention
The present invention is directed to ball seats for use in oil and gas wells and, in particular, to extrudable ball seats having a coating to facilitate sealing the ball to the seat.
2. Description of Art
Ball seats are known in the art. Broadly, ball seats are devices placed within a conduit string or a wellbore through which a fluid is permitted to flow. In some instances it is desired to restrict or prevent flow through the conduit or wellbore so that pressure can build-up within the conduit or wellbore to actuate a downhole tool such as a setting tool to set an anchor or a packer within the conduit or wellbore. Ball seats are used to restrict or prevent such fluid flow by landing or seating a plug or ball on the seat to block flow. Typically, the seat and the ball are formed out of metallic materials such that a rounded portion of the ball lands on a flat surface of the seat. In other embodiments, the seat may have a shape that is reciprocal to the ball, e.g., arcuate to be reciprocally-shaped to the ball.
One particular type of ball seat is known as an “extrudable ball seat” because the seat deforms or “extrudes” due to pressure forcing the ball into the seat until the ball is ultimately allowed to pass through the seat after increased pressure above the ball is not longer needed.
Although the term ball is used herein to refer to the seats disclosed herein, it is to be understood that the seats may be used in connection with another type of plug or plug member, such as a plug dart. Therefore, except where expressly identified as requiring the plug member or plug to be a ball, it is to be understood that “ball” and “plug” are used herein interchangeably.
Broadly, ball seats for receiving a plug element for use in downhole operations in a wellbore comprise a tubular having an inner wall surface defining a bore. The bore is divided into an upper portion and a lower portion, the upper portion having an upper diameter and the lower portion having a smaller lower diameter. A seat is disposed along the inner wall surface between the upper portion and the lower portion so that the seat transitions the inner wall surface from the upper portion to the lower portion. A sealing element is disposed on the seat for receiving a plug element, such as a ball. The sealing element comprises a sealing material that is deformable to a shape reciprocal to a plug shape of a plug element disposed on the seat. The sealing material may comprise a polymer or an elastomer. Additionally, the sealing element may be disposed along the inner wall surface above the seat to facilitate receiving the plug element and sealing the flow path through the ball seat.
In one specific operation of the ball seat, the ball seat restricts fluid flow through a conduit disposed within a wellbore when disposed within the conduit. After the plug element is landed on the seat and, therefore, the sealing element, pressure builds above the plug and forces the plug into the sealing element. In so doing, the sealing element is at least partially deformed to a shape substantially reciprocal to a plug shape of the plug to restrict flow through the conduit.
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 to
The term “sealing material” as used herein for sealing element 50 means that the material is capable of being deformed, e.g., being forced or extruded around or along the outer wall surface of the plug (for example, ball 60 shown in
In one particular embodiment, sealing element 50 is formed from the sealing materials using Adiprene LF963A from Chemtura and cured with Dimethylthiotoluenediamine (DMTDA) commercially available under trade name as Ethacure 300 from Albemarle in Baton Rouge, La. In another embodiment, sealing element 50 is formed from the sealing materials using Adiprene LFP3940A from Chemtura and cured with 1,4-Butanediol (BDO) commercially available under trade name as Vibracure A250 from Chemtura.
In one particular embodiment sealing element 50 is formed completely out of one, sealing material and sealing element 50 comprises a torroidal-shaped single member. In other embodiments, sealing element 50 is disposed along inner wall surface 44 above landing surface 46, such as along portion 49 (shown best in
It is to be understood that the apparatuses and methods disclosed herein are considered successful if the sealing material is sufficiently moved such that the surface area of the plug, e.g., ball 60 in
In operation of one specific embodiment, ball seat 40 is disposed within wellbore or a conduit, e.g., work, string that is placed into the wellbore. Connection of ball seat 40 to the conduit can be accomplished through any method or device known in the art, such as threads disposed at the upper and lower ends of ball seat 40. A plug, such as ball 60 is disposed on landing surface 46 to restrict fluid flow through ball seat 40. Fluid pressure acting downward increases downward force onto ball 60 which drives ball 60 into sealing element 50 disposed on seat 48. The fluid pressure above seat 48 is increased to actuate a downhole tool or perform some other downhole operation. As the downward force increases, sealing element 50 is deformed toward a shape reciprocal to the shape of the plug, i.e., conforms to the shape of ball 60, thereby increasing the seal between ball 60 and seat 48 and, thus, decreasing the likelihood of fluid leaks being formed between ball 60 and seat 48. After the downhole operation is completed, and increased pressure above seat 48 is no longer needed or required, the fluid pressure is continued to be increased until seat 48 is moved axially downward so that seat 48 can radially expand allowing ball 60 to pass through seat 48 resulting in the view shown in
In one specific embodiment of manufacturing the ball seats having the sealing elements discussed herein, the seat is formed within a tubular member made of steel. The ball seat is then lightly sandblasted and placed in a mold. A sealing material is heated and then poured into the mold and onto the seat of ball seat. A vacuum is then placed on the mold to remove bubbles or excess air within the sealing material. The mold is then placed in an oven and heated to cure the sealing material, thereby forming the sealing element on the seat of the ball seat. After the mold is removed from the oven, it is allowed to cool and the mold is removed leaving the sealing element disposed on the seat. In one particular embodiment, the sealing element has a thickness of approximately 0.030 inches, although the thickness can easily be increased or decreased depending on the overall size of the ball seat and the size and shape of the plug or ball. The sealing element is then trimmed of any excess material and the ball seat is ready to be placed into a conduit or wellbore for use.
Although the apparatus described in greater detail with respect to
In other embodiments, in addition to the seat comprising a sealing material, the plug also comprises a sealing material disposed along an outer wall surface of the plug. In still other embodiments, the plug, and not the seat, comprises the sealing material.
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 seat may be used in connection with a ball, dart, or any other type of plug or plug member that is used to restrict or prevent fluid flow through the seat. Additionally, the sealing element may be formed partially or completely out of one or more sealing materials. Further, the ball seat is not required to be an “extrudable” ball seat, i.e., one in which the seat is deformed such as the embodiment of
