Patent Application
20140062025
1. Field of Invention
The present disclosure relates in general to a seal assembly for use with a casing hanger having rings with an axial bore to receive fasteners therein and protrusions on a side of the ring to seal between the ring and an adjacent elastomeric compression seal.
2. Description of Prior Art
Wellbores for producing hydrocarbons typically include a wellhead housing mounted on surface over the wellbore. A length of casing usually lines the walls of the wellbore and is supported by a hanger mounted to the wellhead housing. Casing hangers on land based wells generally include wedge shaped slips for coupling with the casing. Seal assemblies for preventing pressure communication are often inserted between the casing and wellhead housing. Generally, such seal assemblies include coaxial rings coupled together with threaded studs. The studs are typically torqued an amount that causes at least one of the rings to axially compress and radially expand into sealing engagement with both the casing and wellhead housing. However, the stresses introduced into the ring distorts the bore in which the stud is inserted thereby introducing leak paths between the walls of the bore and the stud.
Disclosed herein is an example of a seal assembly for use with a casing hanger. In one example the seal assembly includes an upper ring, a lower compressible ring coaxially disposed with the upper ring, a bore axially extending through the upper ring and compressible ring, an elongated fastener inserted in the bore, and an annular support grommet on a surface of the compressible ring. The support grommet has an aperture that registers with the bore, and also has a protrusion projecting into the compressible ring. The protrusion extends into the compressible ring when the fastener is torqued to axially compress the lower compressible ring. A sealing interface is formed between the support grommet and the lower compressible ring along the protrusion. Optionally, the upper ring is made of metal and the lower compressible ring includes an elastomer. In an alternate embodiment, the upper ring and lower ring each are made up of semi-circular portions that join along a diagonal interface. The annular support grommet can change from a substantially circular shape to an oval shape when the fastener is torqued. Further optionally included is an O-ring in sealing contact between the fastener and inner surface of the support grommet. In this example, the annular support grommet is a first support grommet and a second support grommet is included on a side of the lower compressible ring opposite the first grommet; also, an O-ring is between an inner surface of the second support grommet and the fastener. The fastener may optionally include threads on a lower end, and wherein each of the O-rings has an inner diameter that is greater than an outer diameter of the threads on the lower end of the fastener. In an example, the lower end of the fastener attaches to a hanger body disposed on a lower end of the lower compressible ring. A nut may be threadingly engaged on an upper end of the fastener. In an optional embodiment, an annular expansion ring is compressed between the nut and the upper ring, wherein axially spaced apart slots are provided along a portion of a circumference of the annular expansion ring that extend radially through the annular expansion ring.
Also provided herein is a method of sealing between a wellhead housing and a casing. In one example the method includes positioning an upper seal ring having axial bores onto a lower seal ring having axial bores, registering the axial bores on the upper seal ring with the axial bores on the lower seal ring, providing annular grommets each having an axial aperture and a ridge circumscribing the aperture, positioning the annular grommets substantially coaxial with the axial bores on the lower seal ring and so that the ridges contact the lower seal ring, and using a threaded fastener to couple together the upper and lower seal rings to define a seal assembly and so that the ridges protrude into the lower seal ring and form a sealing interface between each of the annular grommets and the lower seal ring. The threaded fastener can include an elongate member having threads on an upper and a lower end. In an example the method further includes threadingly engaging a nut with an upper end of the threaded fastener and threading the lower end of the threaded fastener into a hanger body, wherein tightening the nut compresses the lower seal ring. Belleville washers can optionally be provided on the fasteners between the nuts and upper ring. O-rings may also be used to seal between the threaded fasteners and the grommets.
Some of the features and benefits of the present invention having been stated, others will become apparent as the description proceeds when taken in conjunction with the accompanying drawings, in which:
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.
The method and system of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments are shown. The method and system of the present disclosure may be in many different forms and should not be construed as limited to the illustrated embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey its scope to those skilled in the art. Like numbers refer to like elements throughout.
It is to be further understood that the scope of the present disclosure 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. In the drawings and specification, there have been disclosed illustrative embodiments and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation.
A side perspective view of the seal assembly 22 is provided in
A pair of grommet-like support rings 50 are shown set in respective cylindrical spaces formed around the bore 46 at the upper and lower ends of the compression seal 32. In the example of
An optional expansion ring 60 is shown in a side perspective view in
The present invention described herein, therefore, is well adapted to carry out the objects and attain the ends and advantages mentioned, as well as others inherent therein. While a presently preferred embodiment of the invention has been given for purposes of disclosure, numerous changes exist in the details of procedures for accomplishing the desired results. These and other similar modifications will readily suggest themselves to those skilled in the art, and are intended to be encompassed within the spirit of the present invention disclosed herein and the scope of the appended claims.
