Wells – Submerged well – Connection or disconnection of submerged members remotely...
Reexamination Certificate
2001-01-26
2003-02-11
Pezzuto, Robert E. (Department: 3671)
Wells
Submerged well
Connection or disconnection of submerged members remotely...
C166S382000, C166S378000, C166S208000
Reexamination Certificate
active
06516887
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an apparatus for applying tension to a tubular member and to a method of using the same. In particular, the present invention relates to an apparatus for tensioning tubular members used in offshore oil and gas drilling and production operations, for example the legs of tensions leg platforms, casing strings and risers, and a method for carrying out the same.
BACKGROUND OF THE INVENTION
Many situations require a tubular member to be placed under tension. Such situations arise in many different aspects of the operations for exploration, drilling and production of oil and gas, in particular in offshore locations. Examples of situations requiring tubular members to be tensioned include the setting of tension leg platforms for offshore drilling and production operations. Further examples arise in the drilling and production of oil and gas from wells accessed through wellheads located on the sea floor, and include the tensioning of risers and casing strings extending between a hanger located in a wellhead on the seabed and a wellhead mounted on a platform or vessel at the surface.
U.S. Pat. No. 4,794,988 discloses a surface wellhead apparatus for use in tying back casings extending to a subsea structure. The casing is held under tension by a lock member which engages on a shoulder within the surface wellhead. A similar arrangement is described in U.S. Pat. No. 4,938,289. Both arrangements require the casing string to be first placed under tension, after which the casing may be held in tension using the arrangements disclosed.
U.S. Pat. No. 4,995,464 describes an offshore well installation in which an adjustable assembly is employed to tension a casing string or other tubular member. The installation comprises a first tubular member and a second tubular member arranged concentrically with a sleeve disposed therebetween. The sleeve is formed with an inner and outer thread thereon, engaging with corresponding outer and inner threads on the first and second tubular members. A lug is disposed between the first and second tubular members to prevent relative rotation of one against the other. Rotation of the sleeve moves the first and second sleeves longitudinally with respect to one another, thus allowing a tension to be placed on the casing string. While the arrangement can be operated to apply tension to the casing string without requiring the string to be tensioned by other means, this is only possible by rotation of the sleeve.
U.S. Pat. No. 5,638,903 discloses an adjustable mandrel hanger system for maintaining tension in a string of casing extending between a subsea wellhead assembly and a surface wellhead housing. A mandrel is secured to the end of the casing string, to which is mounted a locking member. The locking member lands against a shoulder in the wellhead housing. Upon installation, the operator applies tension to the casing string. The mandrel moves upwards relative to the locking member as the tension is applied. Upon release of the tension applied by the operator, the locking member will retain the mandrel and the string under tension against the shoulder. It is to be noted that the hanger system of U.S. Pat. No. 5,638,903 simply holds a casing string under tension, once the tension has been applied by the operator. The hanger system cannot itself be used to apply tension to the casing string.
U.S. Pat. No. 5,653,289 discloses a casing tensioning system for applying tension to a string of casing between a subsea wellhead and a surface wellhead. A casing hanger is secured to the casing: string. The casing hanger has a first position, allowing downward movement of the casing string with respect to the hanger, and a second position, in which upward movement of the casing string is allowed, but in which downward movement of the string relative to the hanger is prevented. The hanger is landed on a shoulder within the surface wellhead. The operator applies tension to the casing string, after which the casing hanger acts to retain the casing string under tension. Again, while the apparatus disclosed is sufficient to hold the tensioned casing string, it cannot be operated to apply the required tension to the string or another tubular member.
A similar arrangement is described in U.S. Pat. No. 5,671,812, in which a casing hanger is secured to a mandrel, the mandrel in turn being attached to a casing string to be tensioned. Again, the casing hanger allows upwards movement of the mandrel with respect to the hanger, but prevents relative downward movement of the mandrel. Hydraulic pressure is used to force the casing hanger to seat against a shoulder within the surface wellhead, after which the mandrel is raised, thereby placing the casing string under tension. As with the earlier designs discussed above, the casing hanger, while retaining the casing string under tension once sufficient tension has been applied, does not act itself to apply tension to the casing string.
An arrangement similar to that of U.S. Pat. No. 5,671,812 is disclosed in U.S. Pat. No. 5,944,111, with the difference that a launch adaptor is used to force the casing hanger against the shoulder in the surface wellhead, after which tension is applied to the casing. The casing hanger acts to retain the string of casing under tension in a similar manner to that described in U.S. Pat. No. 5,671,812.
It can be seen that a variety of assemblies have been proposed to retain a tubular member, such as a casing string, under tension between two fixed assemblies. However, in such arrangements, it is necessary to provide additional means to place the tubular member under the required tension. U.S. Pat. No. 4,995,464 discloses an arrangement in which a single assembly is employed to both apply tension to a tubular member, in this instance a casing string, and retain the tubular member under tension, once applied. However, this arrangement only operates by the interaction of a plurality of separate threads formed on various of the tubular components. The machining of threads is time consuming and undesirable.
Accordingly, it can be seen that there is a need for an assembly which can be attached to a tubular member, such as a string of casing in an offshore well, and operated to both apply tension to the tubular member and retain the member under tension, once applied, by linear movement of the components of the assembly and without the need for components to be rotated or formed with threads.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, there is provided an apparatus for securing a tubular member under tension, the member secured to and extending between a first and second, fixed assembly, the apparatus comprising:
a first tubular assembly connectable at a first engageable portion to the tubular member to be tensioned;
a second tubular assembly having a first and a second engageable portion, the second tubular assembly being arranged concentrically with respect to the first tubular assembly and movable longitudinally with respect to the first tubular assembly;
a first engagement assembly for engaging the first engageable portion of the second tubular assembly with the first fixed assembly, such that movement of the second tubular assembly toward the tubular member to be tensioned is prevented;
a second engagement assembly for engaging the second engageable portion of the second tubular assembly with the first tubular assembly upon longitudinal movement of the second engageable portion of the second tubular assembly with respect to the first tubular assembly toward the first engageable portion of the first tubular assembly;
wherein the second tubular assembly can be placed under tension by moving its second engageable portion longitudinally relative to its first engageable portion, when the first engageable portion is engaged with the first fixed assembly.
When the first tubular assembly is attached to a tubular member, such as a casing string or riser, longitudinal movement of the second engageable portion of the second tubular
Nguyen Dennis P.
Vanderford Delbert E.
Beach Thomas A.
Bielinski Peter A.
Cooper Cameron Corporation
Hartmann Michael P.
Pezzuto Robert E.
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