ACTIVATION MECHANISM FOR THE RELEASE OF A GUIDEPOST

Abstract

An activation mechanism to release a guidepost from a seabed structure is described. The guidepost includes a tubular main body, an operating mechanism at the upper end of the main body, a locking mechanism at the lower end of the main body to enable attachment to the seabed structure, and an interconnecting device arranged inside the tubular main body, and connecting the operating mechanism to the locking mechanism in order to be able to activate the locking mechanism from the top of the guidepost. The operating mechanism includes a rotatable outer sleeve configured to transform a rotary motion to a lifting or lowering motion of the interconnecting device, which in turn elevates or lowers an activation mechanism that influences on at least one locking pawl to be pulled inwards beyond the diametrical dimension of the guidepost to release an engagement with a groove or ledge on the seabed structure.

Description

The present invention relates to an activation mechanism for the release of a guidepost from a seabed structure, which guidepost includes a tubular main body, an operating means at the upper end of the main body, a locking mechanism at the lower end of the main body to enable attachment to the seabed structure, and an interconnecting device, arranged inside the tubular main body, connecting the operating means to the locking mechanism in order to be able to activate the locking mechanism from the top of the guidepost, as required.

During a lowering operation of subsea equipment towards a structure or construction on the seabed, such as a manifold, x-mas trees, control modules or a wellhead, guidelines are frequently used, normally steel ropes or steel wires. Each guideline ends in a guidepost that is secured to and projects from the seabed structure. The guideposts are used to locate and orient components on subsea bases during oil drilling operations or oil production, or to locate modules on top of each other.

For example during drilling of a subsea well, a guide base is normally arranged around the conductor housing of a well that is drilled. The guide base has guideposts and these are used to position a blowout preventer BOP on top of the wellhead. Guideposts can also be used to install and position other modules, for example to guide and position a lower riser package on a blowout preventer, or an emergency disconnect package on a workover blowout preventer.

Such guideposts establish a coarse alignment between the equipment and the wellhead and create vertical stability within the system in order to be able to make connection with the wellhead. Final alignment is performed by a connector making up the connection. On smaller components or modules, only two guideposts are normally used. Recently, only two guideposts are more often used even on larger modules, such as manifolds for example.

Traditionally, often four guidelines and four guideposts have been used during a lowering and landing operation.

When it comes to the length of the guideposts, they can never project above a protecting structure when not in use. The guideposts are either divided in two with a permanent part that ends below the top of the protecting structure and a contemporary post is put on top of that and extends above the structure, or the post can be lowered down until it has arrived below the structure when not in use, or that they are completely removed.

Recently, guideposts have been developed and introduced that are contemporary landed for then to be removed again after that the equipment is arranged on the subsea structure. These are such designed that the lower end facing the seabed has a locking mechanism that can be locked to the subsea structure by mechanical locking means.

The guideposts would then be used as kind of a tool, i.e. one could move them around between respective seabed structures that are stationary deployed on predetermined places, as desired, until the job is done and then have the guideposts retrieved. Such new generation guideposts can in some situations be as long as 17 meters. Thus the guideposts will project above the bottom structure and will be a hazard for fish nets etc if they remain on the seabed structure, and consequently need to be removed.

This prior art solution is normally based on locking means that are operated or maneuvered at same high as the locking mechanism is located, i.e. in the lower end of the of the guidepost. However, at this level a lot of other equipment and components are present, which also make this difficult accessible with an ROV and associated tool for the maneuvering of the locking mechanism itself when the guidepost is to be fixed to the seabed structure.

In order to facilitate the access with an ROV and associated operating tool, an activation mechanism for the release of a guidepost from a seabed structure of the introductory said kind is provided, which operating means includes a rotatable outer sleeve arranged to transform a rotary motion to either a lifting or lowering motion of the interconnecting device, which in turn either lifts or lowers an activation means that actuates at least one locking pawl to be pulled inwards or pushed outwards beyond the diametrical dimension of the guidepost in order to release or make engagement with a groove or ledge on the seabed structure.

In a preferred embodiment, the rotatable outer sleeve of the operating means includes a substantially vertically extending slit that receives a pin in direct connection with an inner sleeve part that is connected to the interconnecting device, and that the upper end part of the guidepost is located partly between the inner and outer sleeve, which end part is provided with a slanting groove therein through which the pin extends between the two sleeves and is thus able to transform said rotary motion to said lifting or lowering motion of said interconnecting device.

The interconnecting device can be in the form of a rod extending between the inner sleeve and the locking mechanism, said rod being supported at one or more locations against the inner wall of the guidepost.

Further, the rod of the interconnecting device can be loosely connected to the inner sleeve such that a limited freedom of motion is present between the sleeve and the rod, such freedom of motion being determined by means of a nut and a back-off nut, and in addition, the inner sleeve is rotatable about the rod.

Preferably, the lower end of the rod of the interconnecting device includes one or more actuating arms that are fixedly connected to the rod, which at least one actuating arm extends in a substantially radial direction relative to the tubular main body.

In one embodiment each individual locking pawl of the locking mechanism can be directly actuatable by the respective actuating arm.

Further, each individual locking pawl can include a slotted track that cooperates with corresponding pin on an activating arm, where each locking pawl being pivotable supported on an axle pin which is such located that when the rod, including the activating arms, are lowered down, the locking pawls pivot outwards and beyond the diametric dimension of the guidepost for the mentioned engagement or abutment with a groove or ledge on the seabed structure.

Preferably, the lower end of the guidepost includes a stop pin that each individual locking pawl rests against in its completely deployed position, where each stop pin being a pin having rupture nicks in case an emergency situation should occur, in order to be able to retract the locking pawls such that the guidepost can be retrieved to the surface.

In one embodiment, the lower end of the guidepost includes a stainless steel contact tip for safe transfer of electric charges to offer anodes.

In a preferable embodiment, the locking mechanism is an automatic acting locking mechanism which is able to lock the lower end of the guidepost to the seabed structure, where each pawl, when it is in deployed position, is forced inwards when the pawl hits a ledge, and the pawl thereafter falls out again when passing the ledge, which freedom of motion between the rod and the inner sleeve part enables this.

In a suitable embodiment, the freedom of motion between the rod and the inner sleeve part is limited by a ledge on the rod and a nut threaded onto a pin end in the extension of the rod, which pin end fits through an aperture in the bottom of the inner sleeve part.

Other and further objects, features and advantages will appear from the following description of preferred embodiments of the invention, which is given for the purpose of description, and given in context with the appended drawings where:

FIG. 1 shows in perspective view a guidepost which has an activating mechanism installed thereon,

FIG. 2 shows an elevation view of an upper end of the guidepost including an operating means,

FIG. 3 shows a longitudinal sectional view through the upper end shown in FIG. 2, but viewed from opposite side,

FIG. 4 shows a section corresponding to that shown in FIG. 3, but having the inner sleeve removed,

FIG. 5 shows a longitudinal section through the lower part of the guidepost shown in FIG. 1, in a situation where the locking mechanism is inoperative,

FIG. 6 shows a longitudinal sectional view through the lower part of the guidepost shown in FIG. 1, in a situation where the locking mechanism is in active locking position,

FIG. 7 shows a situation where the lower end is complete and the locking mechanism in active position.

Reference is firstly made to FIG. 1 that in general shows a complete guidepost 1 that houses an activation mechanism which is specially designed to enable locking of the guidepost 1 to a structure located on the seabed, such as a seabed construction. The guidepost 1 is in the form of a tubular main body 1a forming a housing 1a that partly surrounds the activation mechanism itself. The activation mechanism is not entirely shown in any figures, but parts thereof are shown on each figure and consequently is a compound mechanism consisting of many parts or components.

In the following description reference is made to FIGS. 1, 2 and 3. The activation mechanism includes an operating means 2 which is arranged in the upper end of the main body 1a, and a locking mechanism 3 that is arranged in the lower end of the main body 1a. The locking mechanism 3 is adapted for fixed, or releasable, attachment to the seabed structure. Moreover, the locking mechanism 3 includes an interconnecting device 4 provided internally of the tubular main body 1a connecting the operating means 2 with the locking mechanism 3 in order to be able to activate the locking mechanism 3 from the top of the guidepost 1, as desired.

The operating means 2 includes a rotatable sleeve 2a which is able to translate a rotary motion to either an elevating or lowering motion of the interconnecting device 4. The interconnecting device 4 in turn elevates or lowers an activation means 4a that influence on at least one locking pawl 3a, and the influence takes place in such way that the tip 3a′ of the locking pawl 3a is run outwards beyond the diametric dimension D of the guidepost 1 in order to be able to make engagement with, or abutment with, a groove or a ledge on the seabed structure.

The rotatable outer sleeve 2a of the operating means 2 is provided with a substantially vertically extending recess or slit 2b in the wall thereof. The slit 2b is in turn adapted to receive a pin 2c that is in direct connection with an inner sleeve part 2d. The inner sleeve part 2d is in turn loosely connected to the elevating and lowering interconnecting device 4. It is to be understood that the upper end part 1b of the guidepost 1 is partly located between the inner and outer sleeve 2a, 2d and is securely screwed to the tubular main body 1a by means of threaded connections 5. This means that the upper end part 1b of the guidepost 1 is rotationally stiff in respect of the housing itself or the tubular main body 1a. In the material of this end part 1b, an inclined slit or coulisse groove 1b′ has been formed, through which slit the pin 2c extends between the two sleeves 2a, 2d. Thus it can be understood that by means of interaction between the pin 2c and the slit 1b′, a translation of a rotary motion in the outer sleeve 2a to an elevating or lowering motion of the interconnecting device 4 is made possible.

The slit 1b′ ends in the “upper” end in a small recess 1b″, in which the pin 2c may rest when the pin is in its upper position. This results in that a little additional force is necessary to bring the pin 2c out of the recess 1b″, i.e. out of its own “resting position” or stand by position. This is to prevent unintended activation of the entire activation mechanism and thereby the locking mechanism 3.

The outer sleeve 2a can be engaged by a tool (not shown) that embraces the sleeve 2a and grips hold on the sleeve at the same time as the tool is able to make revolution of the sleeve 2a.

In the following description, reference is also made to FIGS. 4, 5, 6 and 7. The interconnecting device 4 is made up by the activation means 4a and a rod 4b extending between the locking mechanism 3 and the inner sleeve 2d. The rod 4b is supported on several locations by means of journal blocks 8 resting against the inner wall of the guidepost 1. It is to be understood, however, that the journal blocks 8 only have their functions during the assembly of the guideposts 1 and otherwise do not have any function. This is due to the long lengths of the guideposts 1, up to 17 meters, or more, combined with the slenderness of the rod 4b that the blocks 8 support. The rod 4b terminates upwardly in a narrower pin end 4c having a threaded portion 4c′.

The rod 4b of the interconnecting device 4 is in axial direction loosely connected to the bottom 2e of the inner sleeve 2d, such that a limited freedom of motion is present between the sleeve 2d and the rod 4b. The freedom of motion is defined by means of a ledge 4d on the rod 4b in combination with a nut 6a and a lock nut 6b which is tightened such that the pin end 4c receives a certain stroke length relative to the bottom 2e of the inner sleeve 2d. In addition the sleeve 2d is rotatable about the pin end 4c of the rod 4b. A washer 6c is located between the nut 6a and the bottom 2e.

The rod 4b of the interconnecting device 4 has one or more activation arms 4e in its lower end, which arms are fixedly connected to the rod 4b. Each activation arm 4e extends in a substantially radial direction relative to the tubular main body 1a.

As evident from FIGS. 5 and 6, each individual locking pawl 3a on the locking mechanism 3 are directly actuatable by an activation arm 4e. This takes place in such a way that each individual locking pawl 3a includes a slit groove 3a″ that interact with corresponding pin 4e′ on an activation arm 4e. Each locking pawl 3a is in turn rotatable supported on an axle journal 3b, which is such located that when the rod 4b, including the activation arms 4e, is lowered, the locking pawls 3a are pivoted outwards. The tip 3a′ of the locking pawl 3a passes beyond the diametric dimension D of the guidepost 1 such that the tips 3a′ of the locking pawls 3a can make the engagement with a groove, or abutment against a ledge on the subsea structure.

Moreover, the lower end portion 1c of the guidepost 1 can include locking pins 1c′, against which the individual locking pawls 3a, in their fully deployed position, can rest. Each locking pin 1c′ is a pin with one or more fracture marks 1c″ in case an emergency situation should occur, in order to be able to retract the locking pawls 3a, such that the guidepost 1 can be released and retrieved to the surface.

As an option, the lower end portion 1c of the guidepost 1 can include a stainless steel contact tip 7 for safe transfer of electric charges to offer anodes that can be deployed on suitable locations to prevent substantial corrosion.

With reference to FIGS. 3, 6 and 7, the combination of the activation mechanism and the locking mechanism will now be described in closer detail. The locking mechanism 3 is such arranged that the mechanism acts as an automatic locking mechanism that is able to lock the lower part 1c of the guidepost 1 to the subsea structure, i.e. to a groove or a ledge or similar. This takes place when the guidepost 1 is landed in a prepared and matching opening in the seabed structure. When the lower end part 1c enters the opening, each pawl 3a, if in a deployed position, will be forced inwards when the pawl 3a hits the ledge. Thereafter the pawl 3a is deployed again when the pawl has passed the ledge. It is exactly the freedom of motion between the top 4c of the rod 4b and the inner sleeve part 2d that makes this possible.

In particular, the freedom of motion between the rod 4b and the inner sleeve part 2d is restricted and defined by the ledge 4d on the rod 4b and the nut 6a screwed onto the pin end 4c in the extension of the rod 4b, where the pin end 4c passes through a hole in the bottom 2e of the inner sleeve part 2d.

Claims

1. An activation mechanism to release a guidepost from a seabed structure, which guidepost includes a tubular main body, an operating mechanism at an upper end of the main body, a locking mechanism at a lower end of the main body to enable attachment to the seabed structure, and an interconnecting device, arranged inside the tubular main body, connecting the operating mechanism to the locking mechanism in order to be able to activate the locking mechanism from a top of the guidepost as required, wherein the operating mechanism includes a rotatable outer sleeve arranged to transform a rotary motion to either a lifting or lowering motion of the interconnecting device, which in turn either lifts or lowers an activation mechanism that actuates at least one locking pawl to be pulled inwards or pushed outwards beyond a diametrical dimension of the guidepost in order to release or make engagement with a groove or ledge on the seabed structure.

2. The activation mechanism according to claim 1, wherein the rotatable outer sleeve of the operating mechanism includes a substantially vertically extending slit that receives a pin in direct connection with an inner sleeve part that is connected to the interconnecting device, and the upper end part of the guidepost is located partly between the inner and outer sleeve, which end part is provided with a slanting groove therein through which the pin extends between the two sleeves and is thus able to transform said rotary motion to said lifting or lowering motion of said interconnecting device.

3. The activation mechanism according to claim 1, wherein the interconnecting device includes a rod extending between the inner sleeve and the locking mechanism, said rod being supported at one or more locations against the inner wall of the guidepost.

4. The activation mechanism according to claim 1, wherein the rod of the interconnecting device is loosely connected to the inner sleeve such that a limited freedom of motion is present between the sleeve and the rod, said freedom of motion being determined by means of a nut and a back-off nut, and, the inner sleeve is rotatable about the rod.

5. The activation mechanism according to claim 1, wherein the rod of the interconnecting device in its lower end includes one or more actuating arms that are fixedly connected to the rod, which at least one actuating arm extends in a substantially radial direction relative to the tubular main body.

6. The activation mechanism according to claim 1, wherein each individual locking pawl of the locking mechanism is directly actuatable by said respective actuating arm.

7. The activation mechanism according to claim 1, wherein each individual locking pawl includes a slotted track that cooperates with corresponding pin on an activating arm, each locking pawl being pivotable supported on an axle pin which is such located that when the rod including the activating arms are lowered down, the locking pawls pivot outwards and beyond the diametric dimension of the guidepost for said engagement or abutment with a groove or ledge on the seabed structure.

8. The activation mechanism according to claim 1, wherein the lower end of the guidepost includes a stop pin that each individual locking pawl rests against in its completely deployed position, each stop pin being a pin having rupture nicks in case an emergency situation should occur, in order to be able to retract the locking pawls.

9. The activation mechanism according to claim 1, wherein the lower end of the guidepost includes a stainless steel contact tip for safe transfer of electric charges to offer anodes.

10. The activation mechanism according to claim 1, wherein the locking mechanism is an automatic acting locking mechanism which is able to lock the lower end of the guidepost to the seabed structure, each pawl, when it is in deployed position, is forced inwards when the pawl hits a ledge, and the pawl then falls out again when passing the ledge, said freedom of motion between the rod and the inner sleeve part enables this.

11. The activation mechanism according to claim 10, wherein the freedom of motion between the rod and the inner sleeve part is limited by a ledge on the rod and a nut threaded onto a pin end in the extension of the rod, which pin end fits through an aperture in the bottom of the inner sleeve part.

12. The activation mechanism according to claim 2, wherein the interconnecting device includes a rod extending between the inner sleeve and the locking mechanism, said rod being supported at one or more locations against the inner wall of the guidepost.

13. The activation mechanism according to claim 2, wherein the rod of the interconnecting device is loosely connected to the inner sleeve such that a limited freedom of motion is present between the sleeve and the rod, said freedom of motion being determined by means of a nut and a back-off nut, and in addition, the inner sleeve is rotatable about the rod.

14. The activation mechanism according to claim 3, wherein the rod of the interconnecting device is loosely connected to the inner sleeve such that a limited freedom of motion is present between the sleeve and the rod, said freedom of motion being determined by means of a nut and a back-off nut, and in addition, the inner sleeve is rotatable about the rod.

15. The activation mechanism according to claim 2, wherein the rod of the interconnecting device in its lower end includes one or more actuating arms that are fixedly connected to the rod, which at least one actuating arm extends in a substantially radial direction relative to the tubular main body.

16. The activation mechanism according to claim 3, wherein the rod of the interconnecting device in its lower end includes one or more actuating arms that are fixedly connected to the rod, which at least one actuating arm extends in a substantially radial direction relative to the tubular main body.

17. The activation mechanism according to claim 4, wherein the rod of the interconnecting device in its lower end includes one or more actuating arms that are fixedly connected to the rod, which at least one actuating arm extends in a substantially radial direction relative to the tubular main body.

18. The activation mechanism according to claim 2, wherein each individual locking pawl of the locking mechanism is directly actuatable by said respective actuating arm.

19. The activation mechanism according to claim 3, wherein each individual locking pawl of the locking mechanism is directly actuatable by said respective actuating arm.

20. The activation mechanism according to claim 4, wherein each individual locking pawl of the locking mechanism is directly actuatable by said respective actuating arm.