CA2645515C - Split casing wellhead seal - Google Patents
Split casing wellhead seal Download PDFInfo
- Publication number
- CA2645515C CA2645515C CA2645515A CA2645515A CA2645515C CA 2645515 C CA2645515 C CA 2645515C CA 2645515 A CA2645515 A CA 2645515A CA 2645515 A CA2645515 A CA 2645515A CA 2645515 C CA2645515 C CA 2645515C
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- seal
- portions
- sealing
- casing
- vent
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- 238000007789 sealing Methods 0.000 claims abstract description 61
- 239000007789 gas Substances 0.000 claims description 27
- 239000012530 fluid Substances 0.000 claims description 8
- 238000004891 communication Methods 0.000 claims description 4
- 238000013022 venting Methods 0.000 claims description 4
- 238000000034 method Methods 0.000 description 3
- 125000006850 spacer group Chemical group 0.000 description 3
- 229910000975 Carbon steel Inorganic materials 0.000 description 2
- 239000010962 carbon steel Substances 0.000 description 2
- 229920000459 Nitrile rubber Polymers 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 238000005553 drilling Methods 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B33/00—Sealing or packing boreholes or wells
- E21B33/02—Surface sealing or packing
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- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Geology (AREA)
- Mining & Mineral Resources (AREA)
- Physics & Mathematics (AREA)
- Environmental & Geological Engineering (AREA)
- Fluid Mechanics (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Excavating Of Shafts Or Tunnels (AREA)
- Gasket Seals (AREA)
Abstract
Disclosed herein is an apparatus for sealing a cavity between production casing and surface casing. The apparatus includes a seal, which is composed of a plurality of sealing portions. Each of the sealing portions is dimensioned to fit around a portion of the perimeter of the production casing and to seal a portion of the cavity. The sealing portions circumscribe the production casing and sealing the entire cavity when secured in place around the production casing. The apparatus also includes a retainer, which is composed of a plurality of retaining portions. The retaining portions are configured to be clamped together around the surface casing into a secured position and to securely retain the seal around the production casing when in the secured position. Beneficially, this apparatus can be used to retrofit existing, completed wellheads.
Description
SPLIT CASING WELLHEAD SEAL
FIELD OF THE INVENTION
The present invention relates to a seal for use in oil and gas applications.
BACKGROUND OF THE INVENTION
Wellbores are holes drilled into the ground through which oil and gas ("production fluids") can be extracted. The process of extracting production fluids using a wellbore is termed "production". Following drilling of a wellbore and prior to using the wellbore for production, the wellbore must go through a process called "well completion" by which the wellbore is prepared for production. Well completion involves many steps. Two such steps are installing a "surface casing" in the wellbore, which is a pipe string that lines the wellbore and that protects water sources around the wellbore from contamination by fluids within the wellbore;
and installing "production casing", within the surface casing, which surrounds production tubing through which the production fluids are extracted.
An annular area exists between the production casing and the surface casing.
This annular area is typically filled to a certain degree with concrete. The concrete aids in structurally stabilizing the well and prevents gases from escaping up through the annular area and into the atmosphere. Problematically, however, the concrete can sometimes develop fissures through which gases can escape. Consequently, many wells utilize some type of "well cap" to seal the top of the well to prevent such gases from escaping. A problem common in such well caps, however, is that they have to be installed during the well completion process. A completed well cannot easily be retrofit to include a well cap following well completion.
Accordingly, there exists a need for a seal that improves upon known seals in the art.
SUMMARY OF THE INVENTION
According to an aspect of the invention, there is provided an apparatus for sealing a cavity between production casing and surface casing. The apparatus includes a seal having a plurality of sealing portions, each of the sealing portions dimensioned to fit around a portion of the perimeter of the production casing and to seal a portion of the cavity, the sealing portions circumscribing the production casing and sealing the entire cavity when secured in place around the production casing; and a retainer having a plurality of retaining portions, the retaining portions configured to be clamped together around the surface casing into a secured position and to securely retain the seal around the production casing when in the secured position.
Each sealing portion may have a seal flange portion attached thereto, which is configured to support the sealing portion on a surfacing collar enveloping the surface casing.
The plurality of sealing portions may include first and second sealing portions, each having semi-circular inner and outer perimeters. Analogously, the plurality of retaining portions may include first and second retaining portions, each having substantially semi-cylindrical inner and outer surfaces.
The production casing may be eccentrically offset relative to the surface casing and each of the sealing portions may have an inner perimeter. The seal may also include an aperture, for receiving the production casing, defined by the inner perimeters of the sealing portions, the aperture being eccentrically offset relative to the surface casing to correspond to the eccentrically offset production casing.
Each sealing portion may include a top plate portion; a bottom plate portion;
and a gasket portion, secured between the top and bottom plate portions.
FIELD OF THE INVENTION
The present invention relates to a seal for use in oil and gas applications.
BACKGROUND OF THE INVENTION
Wellbores are holes drilled into the ground through which oil and gas ("production fluids") can be extracted. The process of extracting production fluids using a wellbore is termed "production". Following drilling of a wellbore and prior to using the wellbore for production, the wellbore must go through a process called "well completion" by which the wellbore is prepared for production. Well completion involves many steps. Two such steps are installing a "surface casing" in the wellbore, which is a pipe string that lines the wellbore and that protects water sources around the wellbore from contamination by fluids within the wellbore;
and installing "production casing", within the surface casing, which surrounds production tubing through which the production fluids are extracted.
An annular area exists between the production casing and the surface casing.
This annular area is typically filled to a certain degree with concrete. The concrete aids in structurally stabilizing the well and prevents gases from escaping up through the annular area and into the atmosphere. Problematically, however, the concrete can sometimes develop fissures through which gases can escape. Consequently, many wells utilize some type of "well cap" to seal the top of the well to prevent such gases from escaping. A problem common in such well caps, however, is that they have to be installed during the well completion process. A completed well cannot easily be retrofit to include a well cap following well completion.
Accordingly, there exists a need for a seal that improves upon known seals in the art.
SUMMARY OF THE INVENTION
According to an aspect of the invention, there is provided an apparatus for sealing a cavity between production casing and surface casing. The apparatus includes a seal having a plurality of sealing portions, each of the sealing portions dimensioned to fit around a portion of the perimeter of the production casing and to seal a portion of the cavity, the sealing portions circumscribing the production casing and sealing the entire cavity when secured in place around the production casing; and a retainer having a plurality of retaining portions, the retaining portions configured to be clamped together around the surface casing into a secured position and to securely retain the seal around the production casing when in the secured position.
Each sealing portion may have a seal flange portion attached thereto, which is configured to support the sealing portion on a surfacing collar enveloping the surface casing.
The plurality of sealing portions may include first and second sealing portions, each having semi-circular inner and outer perimeters. Analogously, the plurality of retaining portions may include first and second retaining portions, each having substantially semi-cylindrical inner and outer surfaces.
The production casing may be eccentrically offset relative to the surface casing and each of the sealing portions may have an inner perimeter. The seal may also include an aperture, for receiving the production casing, defined by the inner perimeters of the sealing portions, the aperture being eccentrically offset relative to the surface casing to correspond to the eccentrically offset production casing.
Each sealing portion may include a top plate portion; a bottom plate portion;
and a gasket portion, secured between the top and bottom plate portions.
The apparatus may also include a vent in the walls of one of the retainer portions for venting gases contained within the cavity and for fluidly communicating with apertures in the surfacing collar and the surface casing; and a vent seal fluidly sealing the vent to the surface casing, the vent seal for preventing gases from leaking as they exit the surface casing through the apertures. A vent assembly may be fluidly coupled to the vent. The vent assembly may include a conduit having supply and exit ends, the supply end in fluid communication with the vent;
and a valve disposed between the supply and exit ends and movable between open and closed positions, the valve allowing gases to travel from the supply end to the exit end when in the open position and otherwise preventing gas from traveling from the supply end to the exit end.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective view of a completed wellhead;
Figure 2 is a perspective, partially exploded view of a first embodiment of an apparatus for sealing a cavity between production casing and surface casing;
Figure 3 is a side elevation view of a seal, which forms part of the first embodiment, being positioned around production casing;
Figure 4 is a perspective view of the seal in place around the production casing;
Figure 5 is a perspective, partially exploded view of a retainer, which forms part of the first embodiment, being positioned around the seal;
Figure 6 is a side elevation view of the retainer, in place around the seal in a secured position;
Figure 7 is a perspective view of the retainer and the seal in the secured position and of a vent assembly; and Figure 8 is a perspective view of the vent assembly in fluid communication with the retainer.
and a valve disposed between the supply and exit ends and movable between open and closed positions, the valve allowing gases to travel from the supply end to the exit end when in the open position and otherwise preventing gas from traveling from the supply end to the exit end.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective view of a completed wellhead;
Figure 2 is a perspective, partially exploded view of a first embodiment of an apparatus for sealing a cavity between production casing and surface casing;
Figure 3 is a side elevation view of a seal, which forms part of the first embodiment, being positioned around production casing;
Figure 4 is a perspective view of the seal in place around the production casing;
Figure 5 is a perspective, partially exploded view of a retainer, which forms part of the first embodiment, being positioned around the seal;
Figure 6 is a side elevation view of the retainer, in place around the seal in a secured position;
Figure 7 is a perspective view of the retainer and the seal in the secured position and of a vent assembly; and Figure 8 is a perspective view of the vent assembly in fluid communication with the retainer.
DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT
The production casing and the surface casing that are installed into a welibore during well completion extend uphole to and can protrude from the surface of the earth. In Figure 1, there is depicted a completed wellhead. A "wellhead"
refers generally to the top of the casings and to the equipment in connection therewith.
In Figure 1, the wellhead includes surface casing S and production casing P
that protrudes from the surface of the earth in this fashion, a surfacing collar C
that partially envelops the surface casing S, and a valve assembly V. An annular cavity A exists between the outer diameter of the production casing P and the inner diameter of the surface casing S. A typical diameter for the production casing P is about 4.5 inches and a typical diameter for the surface casing S
is about 7 inches; consequently, a typical thickness for the cavity A is about 1.25 inches. Although the production casing P and the surface casing S are shown as being concentric relative to each other in Figure 1, this is not the case for all arrangements of production casing P and surface casing S. The production casing P may, for example, be eccentrically offset within the surface casing S.
During well completion, the cavity A is filled, to a certain degree, with concrete (not shown). Over time, this concrete can develop fissures through which gases contained downhole and within the cavity A can escape to the surface and into the atmosphere. Such uncontrolled release of gas into the atmosphere is undesirable.
A seal cannot easily be installed to seal the cavity A from the atmosphere because of the presence of the valve assembly V. The valve assembly is necessary during production and, once installed, cannot easily be removed. The valve assembly V is bulky, and prevents a seal from easily being securely slid on top of the surface casing S and surfacing collar C.
Referring now to Figure 2, there is depicted a first embodiment of an apparatus 10 for sealing the cavity A from the atmosphere. The apparatus 10 generally includes a seal 22, a retainer 12, and a vent assembly 34. As illustrated in more detail in Figures 3 and 4, below, the seal 22 is for sealing the cavity A
between the production casing P and surface casing S. As illustrated in more detail in Figures 5 and 6, the retainer 12 can be clamped over the seal 22, thus securely retaining the seal 22 in position over the casings P, S. As discussed in more detail with respect to Figures 7 and 8, the vent assembly 34 is fluidly couplable to a vent 32 in the retainer 12, and can be used to sample gases contained within the cavity A.
The seal 22 in the depicted embodiment is a "sandwich seal" that has three layers: a top seal plate 40, a bottom seal plate 44, and a gasket 42 sandwiched therebetween. The top and bottom seal plates 40, 44 may be manufactured from a 0.25 inch thick A36 carbon steel plate. The gasket 42 may be manufactured from a 0.50 inch thick piece of nitrile rubber having a hardness of about 70 durometer. When the outer diameter of the production casing P is about 4.5 inches and the inner diameter of the surface casing S is 7 inches, the inner and outer diameters of the top seal plate 40 may be about 4.63 inches and about 7.66 inches, respectively; the inner and outer diameters of the bottom seal plate 44 may be about 4.63 inches and about 6.75 inches, respectively; and the inner diameter and outer diameters of the gasket 42 may be about 4.63 inches and about 7.00 inches, respectively. This is sufficient to seal the entire cavity A from the atmosphere.
Notably, the seal 22 is divided two portions: a first sealing portion 24 and a second sealing portion 26. Each of the sealing portions 24, 26 has a top plate portion, a gasket portion, and a bottom plate portion that corresponds to the top seal plate 40, gasket 42, and bottom seal plate 44, respectively. The first and second sealing portions 24, 26 are separable from each other. Consequently, when installing the seal 22 on to a completed wellhead, the first and second sealing portions 24, 26 may be clamped around the wellhead, thus avoiding the bulky valve assembly V entirely. Similarly, the retainer 12 is composed of two separable portions: a first retaining portion 24 and a second retaining portion 26.
The production casing and the surface casing that are installed into a welibore during well completion extend uphole to and can protrude from the surface of the earth. In Figure 1, there is depicted a completed wellhead. A "wellhead"
refers generally to the top of the casings and to the equipment in connection therewith.
In Figure 1, the wellhead includes surface casing S and production casing P
that protrudes from the surface of the earth in this fashion, a surfacing collar C
that partially envelops the surface casing S, and a valve assembly V. An annular cavity A exists between the outer diameter of the production casing P and the inner diameter of the surface casing S. A typical diameter for the production casing P is about 4.5 inches and a typical diameter for the surface casing S
is about 7 inches; consequently, a typical thickness for the cavity A is about 1.25 inches. Although the production casing P and the surface casing S are shown as being concentric relative to each other in Figure 1, this is not the case for all arrangements of production casing P and surface casing S. The production casing P may, for example, be eccentrically offset within the surface casing S.
During well completion, the cavity A is filled, to a certain degree, with concrete (not shown). Over time, this concrete can develop fissures through which gases contained downhole and within the cavity A can escape to the surface and into the atmosphere. Such uncontrolled release of gas into the atmosphere is undesirable.
A seal cannot easily be installed to seal the cavity A from the atmosphere because of the presence of the valve assembly V. The valve assembly is necessary during production and, once installed, cannot easily be removed. The valve assembly V is bulky, and prevents a seal from easily being securely slid on top of the surface casing S and surfacing collar C.
Referring now to Figure 2, there is depicted a first embodiment of an apparatus 10 for sealing the cavity A from the atmosphere. The apparatus 10 generally includes a seal 22, a retainer 12, and a vent assembly 34. As illustrated in more detail in Figures 3 and 4, below, the seal 22 is for sealing the cavity A
between the production casing P and surface casing S. As illustrated in more detail in Figures 5 and 6, the retainer 12 can be clamped over the seal 22, thus securely retaining the seal 22 in position over the casings P, S. As discussed in more detail with respect to Figures 7 and 8, the vent assembly 34 is fluidly couplable to a vent 32 in the retainer 12, and can be used to sample gases contained within the cavity A.
The seal 22 in the depicted embodiment is a "sandwich seal" that has three layers: a top seal plate 40, a bottom seal plate 44, and a gasket 42 sandwiched therebetween. The top and bottom seal plates 40, 44 may be manufactured from a 0.25 inch thick A36 carbon steel plate. The gasket 42 may be manufactured from a 0.50 inch thick piece of nitrile rubber having a hardness of about 70 durometer. When the outer diameter of the production casing P is about 4.5 inches and the inner diameter of the surface casing S is 7 inches, the inner and outer diameters of the top seal plate 40 may be about 4.63 inches and about 7.66 inches, respectively; the inner and outer diameters of the bottom seal plate 44 may be about 4.63 inches and about 6.75 inches, respectively; and the inner diameter and outer diameters of the gasket 42 may be about 4.63 inches and about 7.00 inches, respectively. This is sufficient to seal the entire cavity A from the atmosphere.
Notably, the seal 22 is divided two portions: a first sealing portion 24 and a second sealing portion 26. Each of the sealing portions 24, 26 has a top plate portion, a gasket portion, and a bottom plate portion that corresponds to the top seal plate 40, gasket 42, and bottom seal plate 44, respectively. The first and second sealing portions 24, 26 are separable from each other. Consequently, when installing the seal 22 on to a completed wellhead, the first and second sealing portions 24, 26 may be clamped around the wellhead, thus avoiding the bulky valve assembly V entirely. Similarly, the retainer 12 is composed of two separable portions: a first retaining portion 24 and a second retaining portion 26.
Thus, when the retainer 12 is being positioned to clamp in place over the seal 22, the retainer 12 can also avoid the valve assembly V.
Referring now to Figures 3 and 4, there are depicted views of the seal 22 being installed such that the cavity A is sealed. The first and second sealing portions 24, 26 each have semi-circular inner (which interfaces with the production casing P) and outer perimeters. Each sealing portion 24, 26 can be brought together around the production casing P to clamp around it (Figure 3). Each sealing portion 24, 26 also has a seal flange portion, which together form a seal flange 28 when the sealing portions 24, 26 are brought together. The seal flange 28 results from the difference between the outer diameters of the top and bottom seal plates 40, 44, that circumscribes the seal 22. The seal flange 28 allows the seal 22 to rest on and be supported by the surfacing collar C (Figure 4).
Although only two sealing portions 24, 26 are depicted in the figures, any number of sealing portions can be used to seal the cavity A from the atmosphere.
Additionally, as mentioned above, the surface casing S and production casing P
may be eccentric relative to each other. In such embodiments, the shape of the seal 22 and retainer 12 can be accordingly modified to be able to fit around and clamp to such surface casing S and production casing P. The apertures defined by the inner perimeters of the seal 22 and the inner surfaces of the retainer may, for example, be eccentrically offset just as the production casing P is eccentrically offset relative to the surface casing S.
Referring now to Figures 5 and 6, there are depicted views of the retainer 12 being positioned over the seal 22 and being used to securely clamp the seal 22 in place. The first and second retaining portions 14, 16 are substantially semi-cylindrical in shape. By "substantially semi-cylindrical", it is meant that the retaining portions 14, 16 are semi-cylindrical in shape except for the presence of bushings 31, 33 and fastening tabs 20 that are used to securely clamp the two retaining portions 14, 16 together. Each retaining portion 14, 16 can be brought together around the surfacing collar C and the seal 22 to clamp down on the seal 22. Fasteners 18 extend through the fastening tabs 20 to clamp the two retaining portions 14, 16 together. In order to exert pressure on the seal 22, the retainer 12 has a retainer flange 30 that fits over the seal 22 and compressively secures the seal 22 to the surfacing collar C. When the seal 22 is so secured to the surfacing collar C, the apparatus 10 is in a secured position. In this exemplary embodiment, the retainer 12 is made from 8 5/8 inch J-55 casing weight 24.00 lbs/ft. The retainer 12 is about 9.38 inches in height, has an inner diameter of about 8.10 inches, and an outer diameter of about 8.63 inches. The retainer flange 30 is made from a 0.25 inch thick A36 carbon steel plate and has an inner diameter of about 6.50 inches and an outer diameter of 8.63 inches. The flange 30 can be welded to an end of the retainer 12. Both ends of the retainer 12 can have a flange. The fasteners 18 can be any suitable nut and bolt.
Each retaining portion 14, 16 is manufactured with a hole through which a spacer bushing 31 and a thread-o-let 33 are inserted. The spacer bushing 31 contacts the surfacing collar C and helps to stabilize the retainer 12 about the surfacing collar C. The bushings and thread-o-let 31, 33 can be welded to the retaining portions 14, 16. Prior to clamping the retainer 12 over the surfacing collar C, an aperture through to the cavity A can be drilled through the surfacing collar C
and the surface casing S. By aligning the thread-o-let 33 with the apertures through the surfacing collar C and surface casing S when the retainer 12 is in the secured position, gases from within the cavity A can escape through the thread-o-let 33.
Disposed between the thread-o-let 33 and the surface of the surfacing collar C
is a vent seal 36 that fluidly seals the connection between the thread-o-let 33 and the surfacing collar C. The thread-o-let 33 and drilled apertures can thus be used as a vent 32 between the cavity A and a vent assembly 34. In this exemplary embodiment, the vent seal 36 is an o-ring. The thread-o-let 33 has about a 2 inch inner diameter and about a 3 inch outer diameter, and has a length of about 1.50 inches. The spacer bushing 31 has about a 3 inch outer diameter and a length of about 1.50 inches.
Referring now to Figures 3 and 4, there are depicted views of the seal 22 being installed such that the cavity A is sealed. The first and second sealing portions 24, 26 each have semi-circular inner (which interfaces with the production casing P) and outer perimeters. Each sealing portion 24, 26 can be brought together around the production casing P to clamp around it (Figure 3). Each sealing portion 24, 26 also has a seal flange portion, which together form a seal flange 28 when the sealing portions 24, 26 are brought together. The seal flange 28 results from the difference between the outer diameters of the top and bottom seal plates 40, 44, that circumscribes the seal 22. The seal flange 28 allows the seal 22 to rest on and be supported by the surfacing collar C (Figure 4).
Although only two sealing portions 24, 26 are depicted in the figures, any number of sealing portions can be used to seal the cavity A from the atmosphere.
Additionally, as mentioned above, the surface casing S and production casing P
may be eccentric relative to each other. In such embodiments, the shape of the seal 22 and retainer 12 can be accordingly modified to be able to fit around and clamp to such surface casing S and production casing P. The apertures defined by the inner perimeters of the seal 22 and the inner surfaces of the retainer may, for example, be eccentrically offset just as the production casing P is eccentrically offset relative to the surface casing S.
Referring now to Figures 5 and 6, there are depicted views of the retainer 12 being positioned over the seal 22 and being used to securely clamp the seal 22 in place. The first and second retaining portions 14, 16 are substantially semi-cylindrical in shape. By "substantially semi-cylindrical", it is meant that the retaining portions 14, 16 are semi-cylindrical in shape except for the presence of bushings 31, 33 and fastening tabs 20 that are used to securely clamp the two retaining portions 14, 16 together. Each retaining portion 14, 16 can be brought together around the surfacing collar C and the seal 22 to clamp down on the seal 22. Fasteners 18 extend through the fastening tabs 20 to clamp the two retaining portions 14, 16 together. In order to exert pressure on the seal 22, the retainer 12 has a retainer flange 30 that fits over the seal 22 and compressively secures the seal 22 to the surfacing collar C. When the seal 22 is so secured to the surfacing collar C, the apparatus 10 is in a secured position. In this exemplary embodiment, the retainer 12 is made from 8 5/8 inch J-55 casing weight 24.00 lbs/ft. The retainer 12 is about 9.38 inches in height, has an inner diameter of about 8.10 inches, and an outer diameter of about 8.63 inches. The retainer flange 30 is made from a 0.25 inch thick A36 carbon steel plate and has an inner diameter of about 6.50 inches and an outer diameter of 8.63 inches. The flange 30 can be welded to an end of the retainer 12. Both ends of the retainer 12 can have a flange. The fasteners 18 can be any suitable nut and bolt.
Each retaining portion 14, 16 is manufactured with a hole through which a spacer bushing 31 and a thread-o-let 33 are inserted. The spacer bushing 31 contacts the surfacing collar C and helps to stabilize the retainer 12 about the surfacing collar C. The bushings and thread-o-let 31, 33 can be welded to the retaining portions 14, 16. Prior to clamping the retainer 12 over the surfacing collar C, an aperture through to the cavity A can be drilled through the surfacing collar C
and the surface casing S. By aligning the thread-o-let 33 with the apertures through the surfacing collar C and surface casing S when the retainer 12 is in the secured position, gases from within the cavity A can escape through the thread-o-let 33.
Disposed between the thread-o-let 33 and the surface of the surfacing collar C
is a vent seal 36 that fluidly seals the connection between the thread-o-let 33 and the surfacing collar C. The thread-o-let 33 and drilled apertures can thus be used as a vent 32 between the cavity A and a vent assembly 34. In this exemplary embodiment, the vent seal 36 is an o-ring. The thread-o-let 33 has about a 2 inch inner diameter and about a 3 inch outer diameter, and has a length of about 1.50 inches. The spacer bushing 31 has about a 3 inch outer diameter and a length of about 1.50 inches.
Referring now to Figures 7 and 8, there is depicted a vent assembly 34 that can be fluidly coupled to the vent 32. The vent assembly 34 is composed of tubing that has supply and exit ends. The supply end of the vent assembly 34 couples to the thread-o-let 33. The vent assembly 34 also includes a valve 38 that is movable between open and closed positions. In the open position, gas from the cavity A can travel through the vent assembly 34 and exit the assembly 34 at the exit end of the tubing. Otherwise, gas cannot exit through the vent assembly 34.
During typical usage, the valve 38 is in the open position and a technician can determine whether any gas is leaking out of the cavity A by performing, for example, a bubble test at the exit end of the tubing of the vent assembly 34.
Consequently, the technician can easily determine whether gas is leaking from the wellhead and, if so, corrective measures can be taken.
While illustrative embodiments of the invention have been described, it will be appreciated that various changes can be made therein without departing from the scope and spirit of the invention. The invention is therefore to be considered limited solely by the scope of the appended claims
During typical usage, the valve 38 is in the open position and a technician can determine whether any gas is leaking out of the cavity A by performing, for example, a bubble test at the exit end of the tubing of the vent assembly 34.
Consequently, the technician can easily determine whether gas is leaking from the wellhead and, if so, corrective measures can be taken.
While illustrative embodiments of the invention have been described, it will be appreciated that various changes can be made therein without departing from the scope and spirit of the invention. The invention is therefore to be considered limited solely by the scope of the appended claims
Claims (16)
1. An apparatus for sealing a cavity between production casing and surface casing, the apparatus comprising:
(a) a seal comprising a plurality of sealing portions, each of the sealing portions dimensioned to fit around a portion of the perimeter of the production casing and to seal a portion of the cavity, the sealing portions circumscribing the production casing and sealing the entire cavity when secured in place around the production casing; and (b) a retainer comprising a plurality of retaining portions, the retaining portions configured to be clamped together around the surface casing into a secured position and to securely retain the seal around the production casing when in the secured position.
(a) a seal comprising a plurality of sealing portions, each of the sealing portions dimensioned to fit around a portion of the perimeter of the production casing and to seal a portion of the cavity, the sealing portions circumscribing the production casing and sealing the entire cavity when secured in place around the production casing; and (b) a retainer comprising a plurality of retaining portions, the retaining portions configured to be clamped together around the surface casing into a secured position and to securely retain the seal around the production casing when in the secured position.
2. An apparatus as claimed in claim 1 wherein each sealing portion comprises a seal flange portion attached thereto, each seal flange portion configured to support the sealing portion on a surfacing collar enveloping the surface casing.
3. An apparatus as claimed in claim 2 wherein the retainer further comprises a retainer flange configured to contact the seal flange and to compressively secure the seal to the surfacing collar when in the secured position.
4. An apparatus as claimed in claim 3 wherein:
(a) the production casing is eccentrically offset relative to the surface casing and each of the sealing portions has an inner perimeter; and (b) the seal further comprises an aperture, for receiving the production casing, defined by the inner perimeters of the sealing portions, the aperture eccentrically offset relative to the surface casing to correspond to the eccentrically offset production casing.
(a) the production casing is eccentrically offset relative to the surface casing and each of the sealing portions has an inner perimeter; and (b) the seal further comprises an aperture, for receiving the production casing, defined by the inner perimeters of the sealing portions, the aperture eccentrically offset relative to the surface casing to correspond to the eccentrically offset production casing.
5. An apparatus as claimed in claim 3 wherein the plurality of sealing portions comprises first and second sealing portions, each having semi-circular inner and outer perimeters.
6. An apparatus as claimed in claim 5 wherein the plurality of retaining portions comprises first and second retaining portions, each having substantially semi-cylindrical inner and outer surfaces.
7. An apparatus as claimed in claim 6 wherein each sealing portion comprises:
(a) a top plate portion;
(b) a bottom plate portion; and (c) a gasket portion, secured between the top and bottom plate portions.
(a) a top plate portion;
(b) a bottom plate portion; and (c) a gasket portion, secured between the top and bottom plate portions.
8. An apparatus as claimed in claim 1 wherein the retainer further comprises:
(a) a vent in the walls of one of the retainer portions for venting gases contained within the cavity and for fluidly communicating with apertures in the surfacing collar and the surface casing; and (b) a vent seal fluidly sealing the vent to the surface casing, the vent seal for preventing gases from leaking as they exit the surface casing through the apertures.
(a) a vent in the walls of one of the retainer portions for venting gases contained within the cavity and for fluidly communicating with apertures in the surfacing collar and the surface casing; and (b) a vent seal fluidly sealing the vent to the surface casing, the vent seal for preventing gases from leaking as they exit the surface casing through the apertures.
9. An apparatus as claimed in claim 8 further comprising a vent assembly comprising:
(a) a conduit having supply and exit ends, the supply end in fluid communication with the vent; and (b) a valve disposed between the supply and exit ends and movable between open and closed positions, the valve allowing gases to travel from the supply end to the exit end when in the open position and otherwise preventing gas from traveling from the supply end to the exit end.
(a) a conduit having supply and exit ends, the supply end in fluid communication with the vent; and (b) a valve disposed between the supply and exit ends and movable between open and closed positions, the valve allowing gases to travel from the supply end to the exit end when in the open position and otherwise preventing gas from traveling from the supply end to the exit end.
10. A wellhead seal for preventing escapage of gas from an interface existing between a production casing and a surface casing on a wellhead, the wellhead seal comprising:
(a) a plurality of sealing portions, each of the sealing portions dimensioned to cover a portion of the interface and to seal the interface when secured in place on the wellhead; and (b) a plurality of retaining portions, the retaining portions shaped to be clamped together on the plurality of sealing portions, thereby clamping the plurality of sealing portions on the wellhead such that the plurality of sealing portions is secured in place on the wellhead.
(a) a plurality of sealing portions, each of the sealing portions dimensioned to cover a portion of the interface and to seal the interface when secured in place on the wellhead; and (b) a plurality of retaining portions, the retaining portions shaped to be clamped together on the plurality of sealing portions, thereby clamping the plurality of sealing portions on the wellhead such that the plurality of sealing portions is secured in place on the wellhead.
11. A wellhead seal as claimed in claim 10 wherein there are two sealing portions and two retaining portions, and wherein each of the sealing portions has semi-circular inner and outer perimeters, and each of the retaining portions has substantially semi-cylindrical inner and outer walls.
12. A wellhead seal as claimed in claim 10 wherein each of the sealing portions comprises:
(a) a top plate portion;
(b) a bottom plate portion; and (c) a gasket portion, secured between the top and bottom plate portions.
(a) a top plate portion;
(b) a bottom plate portion; and (c) a gasket portion, secured between the top and bottom plate portions.
13. A wellhead seal as claimed in claim 11 wherein the walls of at least one of the retaining portions has a vent therethrough for venting gases from the cavity.
14. A wellhead seal for sealing a cavity between production casing and surface casing, the wellhead seal comprising:
(a) a pair of sealing portions, each of the sealing portions dimensioned to fit around a portion of the perimeter of the production casing and to seal a portion of the cavity, the sealing portions circumscribing the production casing and sealing the entire cavity when secured in place around the production casing, each of the sealing portions comprising:
(i) a bottom plate portion;
(ii) a top plate portion, the top plate portion shaped to operate as a seal flange portion operable to support the sealing portion on a surfacing collar around the surface casing; and (iii) a gasket portion, secured between the top and bottom plate portions;
(b) a pair of retaining portions, the retaining portions configured to be clamped together around the surface casing into a secured position and to securely retain the seal portions around the production casing when in the secured position, each of the retaining portions having substantially semi-cylindrical inner and outer walls.
(a) a pair of sealing portions, each of the sealing portions dimensioned to fit around a portion of the perimeter of the production casing and to seal a portion of the cavity, the sealing portions circumscribing the production casing and sealing the entire cavity when secured in place around the production casing, each of the sealing portions comprising:
(i) a bottom plate portion;
(ii) a top plate portion, the top plate portion shaped to operate as a seal flange portion operable to support the sealing portion on a surfacing collar around the surface casing; and (iii) a gasket portion, secured between the top and bottom plate portions;
(b) a pair of retaining portions, the retaining portions configured to be clamped together around the surface casing into a secured position and to securely retain the seal portions around the production casing when in the secured position, each of the retaining portions having substantially semi-cylindrical inner and outer walls.
15. A wellhead seal as claimed in claim 14 wherein at least one of the retaining portions comprises:
(a) a vent through the walls of the at least one of the retaining portions for venting gases contained within the cavity and for fluidly communicating with apertures in the surfacing collar and the surface casing; and (b) a vent seal fluidly sealing the vent to the surfacing casing, the vent seal preventing gases from leaking as they exit the surface casing through the apertures.
(a) a vent through the walls of the at least one of the retaining portions for venting gases contained within the cavity and for fluidly communicating with apertures in the surfacing collar and the surface casing; and (b) a vent seal fluidly sealing the vent to the surfacing casing, the vent seal preventing gases from leaking as they exit the surface casing through the apertures.
16. A wellhead seal as claimed in claim 15 further comprising a vent assembly, the vent assembly comprising:
(a) a conduit having supply and exit ends, the supply end in fluid communication with the vent; and (b) a valve disposed between the supply and exit ends and movable between open and closed positions, the valve allowing gases to travel from the supply end to the exit end when in the open position and otherwise preventing gas from traveling from the supply end to the exit end.
(a) a conduit having supply and exit ends, the supply end in fluid communication with the vent; and (b) a valve disposed between the supply and exit ends and movable between open and closed positions, the valve allowing gases to travel from the supply end to the exit end when in the open position and otherwise preventing gas from traveling from the supply end to the exit end.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA2645515A CA2645515C (en) | 2008-12-01 | 2008-12-01 | Split casing wellhead seal |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA2645515A CA2645515C (en) | 2008-12-01 | 2008-12-01 | Split casing wellhead seal |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2645515A1 CA2645515A1 (en) | 2010-06-01 |
| CA2645515C true CA2645515C (en) | 2010-10-26 |
Family
ID=42229309
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA2645515A Active CA2645515C (en) | 2008-12-01 | 2008-12-01 | Split casing wellhead seal |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2645515C (en) |
-
2008
- 2008-12-01 CA CA2645515A patent/CA2645515C/en active Active
Also Published As
| Publication number | Publication date |
|---|---|
| CA2645515A1 (en) | 2010-06-01 |
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