SYSTEM AND METHOD FOR CONTROLLING A BLOWOUT LOCATION AT AN OFFSHORE OILFIELD

Abstract

A system for controlling a blowout location at an offshore oilfield comprises: a support construction that is movable next to a blowout location in an offshore oilfield and that can be set to rest in seabed, the support construction comprising: a) a first foundation part and a second foundation part that are located at a distance from each other; b) support members that are located at a distance from each other; and a funnel structure that is movable along the support members, the funnel structure comprising connecting members that are form-locking with the support members. The first foundation part, the second foundation part and the support members are so configured that the blowout location can be restricted a) between the first foundation part and the second foundation part and b) between the support members. The funnel structure a) is movable along the support members from a side position to above the blowout location and b) is dimensioned to restrict the blowout by redirecting flow from the blowout into an exit pipe. The funnel structure and the support construction are so dimensioned that when the funnel structure is located on top of the blowout location, the system remains substantially stable to enable restricting the blowout. Includes an independent patent claim for a method for controlling a blowout location at an offshore oilfield.

Description

FIELD OF THE INVENTION

The invention relates to systems and methods for controlling a blowout location at an offshore oilfield.

BACKGROUND ART

Drillings in seabed oil wells have been carried out since some time. When seabed oil is drilled, in order to avoid causing excessive damage to sea life, it is necessary to utilize reliable pressure control systems that have developed since 1920s and thereafter. Now we know that oil or gas gushers which may appear in offshore drilling—despite of known pressure control systems—are difficult to control.

The Deepwater Horizon oil spill, also known as Gulf of Mexico oil spill, is a massive and—at the time of writing still ongoing—oil spill in the Gulf of Mexico. The spill originates from a blowout, i.e. uncontrolled release of crude oil and/or natural gas from an offshore oil well after pressure control systems have failed.

In the Deepwater Horizon case, the oil rig's blowout prevention mechanism which was designed as a fail-safe device fitted at the source of the well did not automatically cut off the oil after the explosion at the oil rig. The operator of the oil rig attempted to use remotely operated underwater vehicles to close the blowout preventer valves on the well head but did not have a remarkable success.

Next, the operator tried to control the oil spill by placing a 125-tonne container dome over the largest of the leaks and then to pipe the oil to a storage vessel on the surface. It could be that this arrangement failed when gas leaking from the pipe combined with cold water to form methane hydrate crystals which may have blocked up the steel canopy at the top of the dome. It could be that the excess buoyancy of the crystals clogged the opening at the top of the dome which is the location where the riser should have been connected.

SUMMARY OF THE INVENTION

It is an object of the invention to enable controlling a blowout location at an offshore oilfield such as what might be necessary after, say, a fail-safe device has failed, or when a pipe between an offshore oilfield and a collection tank has broken.

This object can be achieved with a system according to claim 1, and with a method according to claim 9.

The system for controlling a blowout location at an offshore oilfield comprises a support construction that is movable next to a blowout location in an offshore oilfield and that can be set to rest in seabed, the support construction comprising a) a first foundation part and a second foundation part that are located at a distance from each other, and b) support members that are located at a distance from each other, and the system further comprises a funnel structure that is movable along the support members, the funnel structure comprising connecting members that are form-locking with the support members.

In the system, the first foundation part, the second foundation part and the support members are so configured that the blowout location can be restricted a) between the first foundation part and the second foundation part and b) between the support members. Furthermore, the funnel structure a) is movable along the support members from a side position to above the blowout location and b) is dimensioned to restrict the blowout by redirecting flow from the blowout into an exit pipe. The funnel structure and the support construction are so dimensioned that when the funnel structure is located on top of the blowout location, the system remains substantially stable to enable restricting the blowout.

The method for controlling a blowout location at an offshore oilfield comprises the steps of a) bringing a system for controlling a blowout location at an offshore oilfield to an offshore oilfield, b) positioning the first foundation part and the second foundation part of the system to rest in seabed at opposite positions around the blowout location, c) attaching a funnel structure in a form-locked manner to the system at an away position from the blowout location, d) moving the funnel structure along support members of the system until the funnel structure is on top of the blowout location, and e) controlling the blowout location by redirecting flow from the blowout with the funnel structure into an exit pipe.

The dependent claims describe advantageous aspects of the system and of the method.

ADVANTAGES OF THE INVENTION

The inventor believes that a system of the above kind is easier positionable in place than the 125-tonne container dome since the mass flow from the blowout must have exerted a gigantic momentum on the dome, which thus must have been extremely difficult to bring in place. In addition, the inventor believes that by using this kind of system the adverse effect observed in the 125-tonne container dome experiment, where gas leaking from the pipe combined with cold water to form methane hydrate crystals, can be better avoided.

Since in the method, the first foundation part and the second foundation part are first brought to rest on seabed before the funnel structure and because the funnel structure is form-locked to the support members before the funnel structure is positioned to restrict the flow, the flow from the outblow causes inertia on the funnel structure only when the funnel is positioned very stable in system and kept in place by the first foundation part and the second foundation part. If now the first foundation part and the second foundation part are stable enough as they must, the funnel structure can be positioned on top of the outblow much closer to the outblow location and, even more importantly, much more precisely than a 125-tonne container dome that was floating in the water.

Any of the first foundation part and second foundation part, or both, may comprise at least one compartment that is fillable with ballast. As “ballast” is here meant a material or a composition of several materials that over a predetermined period of time remains substantially stable in sea water and that has a density much larger than water. Examples of such materials or components of the composition include but are not limited to metals—especially iron or lead, stone—especially granite, concrete, and sand. With the at least one compartment, the dead mass of the respective foundation part can be increased when the foundation part is in place. In this manner, the first and the second foundation part can be set rest in seabed stable enough while the foundation parts being still lightweight enough for easier carriage to the offshore oilfield.

The support members may be rod-like members around which the funnel structure form-locks. Thanks to this solution, the distance between the first and second foundation part does not need to be known precisely in advance. Sometimes the seabed may cause the foundation parts slightly move when they set to rest in place which makes a precise positioning difficult and to depend on exact seabed characteristics.

The support members may be adapted to run between holders at the first foundation part and the second foundation part. This is a particularly elegant solution since it enables the support members to be transported independently of the first foundation part and the second foundation part.

The support members may be elongated guide members which form-lock with the funnel structure.

Each of the support members may be arranged to run along the respective foundation part.

If the funnel structure comprises a vertically movable funnel, it is possible to lower the funnel to cover the outblow location only after the funnel structure is supported by the system. In this manner, the system does not need to be installed very close to the outblow location which is believed to make the installation work easier.

If the system further comprises adjusting members to adjust the height of the support members from the seabed, the system can be used for blowouts at different heights from seabed.

LIST OF DRAWINGS

In the following, the preferred embodiments of the system and method are described in more detail with reference to the examples shown in the accompanying drawings, of which:

FIG. 1 shows the support structure of a system for controlling a blowout location at an offshore oilfield, without the funnel structure and support members;

FIG. 2 shows the system of FIG. 1 with support members and funnel structure installed;

FIG. 3 shows the system of FIG. 2 when the funnel structure is placed on top of the blowout location;

FIG. 4 illustrates the system of FIG. 2 as seen from the left side;

FIG. 5 illustrates the moving of the funnel structure from the position shown in FIG. 2 to the position shown in FIG. 3, as seen from the left side;

FIG. 6 illustrates the step of lowering the funnel structure, as seen from the left side;

FIG. 7 a further embodiment of the system as seen from an end;

FIG. 8 the system of FIG. 7 as seen from top;

FIG. 9 a further embodiment of the system as seen from an end; and

FIG. 10 a further embodiment of the system as seen from top.

Same reference numerals refer to similar technical features in all drawings.

DETAILED DESCRIPTION

FIG. 1 shows a system for controlling a blowout location 102 at an offshore oilfield. The blowout location 102 is under water in a sea 100. From the blowout location 102, a stream 110 consisting of a mixture of oil, gas, water and sand gushes upwards. In FIG. 1, the blowout location 102 is shown as the end 103 of a cut pipe. In reality, the blowout location 102 could be instead of or in addition to a cut pipe also a torn or otherwise damaged pipe, or some other structure. In deep sea installations suffering from a blowout, no pipe nor pipe end may be visible; the blowout location may be buried in mud or sand in the sea bed 101.

The system for controlling a blowout location 102 comprises a support construction. The support construction comprises a first foundation part 150 and a second foundation part 150. The first and second foundation parts 150 are brought to an offshore oilfield.

Then the first foundation part 150 and the second foundation part 150 are positioned to rest in seabed 101 at opposite positions around the blowout location 102, which then in a sense is so restricted between them. The distances between the blowout location 102 and the first foundation part 150 and the second foundation part 150 have been denoted with F and G, respectively. The first foundation part 150 and the second foundation part 150 are thus located at a distance F+G from each other. Distances F and G are preferably chosen so large that the stream 110 does not disturb the installation of the support construction.

Each of the first foundation part 150 and the second foundation part 150 comprises holders 151 for support members. The holders 151 are located at a distance A from each other. The holders 151 are in FIG. 1 shown as eyes having a receiving opening 152 for a support member. The holders 151 are preferably form-locked to the first or the second foundation part 150, respectively. The distance between the holders 151 of the first foundation part 150 and the second foundation part 150 has been denoted with B in FIG. 1.

The height and direction of the holders 151 with respect to a central portion 154 of the first and second foundation part 150 may be adjustable. The adjusting can be achieved, for example, by adapting the length and attaching angle of a connecting pile 153 between the center part and the holder 151. This enables the adjusting of the position of the holders 151 to compensate for the topology of the seabed.

The first foundation part 150 and the second foundation part 150 may comprise at least one compartment 155 for receiving ballast. The compartments 155 of the foundation part 150 on the left hand side are shown empty while the compartments of the foundation part 150 on the right hand side are shown filled. Filling the compartments increases the dead mass of the first and second foundation parts 150 and thus makes the system more stable.

If need be, the first foundation part 150 and the second foundation part 150 may be extended by adding one or more extension modules 190 as illustrated by the dashed line in FIG. 1.

If need be, for further stability, the system can be anchored to the seabed 101 using anchors 180 or other suitable means.

FIG. 2 shows the system of FIG. 1 with support members 201, such as suitably selected beams, and funnel structure 250 installed. The distance between the elongated support members 201 has been denoted by a (a<A). The two distances a and A are preferably chosen so that, while the stream 110 from the blowout location 102 gets broader with increasing height, the installation of the support members 201 is not disturbed by the stream 110. Since the stream 110 preferably passes between the support members 201, the stream 110 in a sense gets restricted between the support members 201.

The funnel structure 250 is installed so that it form-locks with the support members 201. The pedestal 254 of the funnel structure 250 may therefore comprise eyes through which the support members 201 can pass. When the support members 201 are at both ends supported by the holders 151 that are firmly in place at the first foundation part 150 and the second foundation part 150 (through receiving openings 152), the funnel construction 250 is very stable but can nevertheless be moved along the support members 201.

The width of the funnel structure 250 has been denoted by b in FIG. 2. The distance G between the blowout location 102 and the second foundation part 150 is preferably chosen so that the remaining clearance c between the stream 110 from the blowout location 102 and the funnel structure 250 enables assembling the funnel structure in place without the stream 110 disturbing the assembling procedure.

The funnel structure 250 comprises a sleeve 253 and a funnel 251. Preferably at the top end of the funnel 251 there is an opening 252 for an exit pipe. The skilled person understands that to fix the exit pipe in place at funnel 251 or sleeve 253 there may be fittings required; they have been omitted from FIG. 2 for the sake of clarity.

FIG. 4 illustrates the system of FIG. 2 as seen from the left side. The exit pipe 301 is mounted on the funnel 251 and preferably fixed at the sleeve 253 as illustrated by the dashdotted line in FIG. 3. Then the funnel structure 250 is moved from the position shown in FIG. 2 to the position shown in FIG. 3, as illustrated by arrow X in FIG. 5.

The funnel 251 in the funnel structure 250 is vertically movable. This means, the funnel 251 is, as soon as it is on top of the blowout location 102, lowered from its initial position as illustrated in FIGS. 3 and 6 by arrow H so that it redirects the stream 110 comprising the flow from the blowout location 102 into the exit pipe 301. Alternatively, it is possible to lower the funnel 251 before it is moved on top of the blowout location 102. In this manner, the lowering of the funnel 251 may be performed with using less force.

After the funnel 251 has been lowered, it is preferably restrained by form-locking means at the sleeve 253. For increased protection, it may be possible to weld the funnel 251 to the sleeve 253 by using a suitable under-water welding technology.

The purpose of the support construction is to arrange a substantially stable position for the funnel structure 250. The funnel structure 250 must bear the forces and resist the mass flow from the restricted stream 110 from the blowout location 102. In addition, there may be marine currents and the like on the seabed 101. The support construction is therefore preferably so dimensioned that it remains firmly in place.

FIGS. 7 and 8 show a second embodiment of the system. The support structure comprises now a first foundation part 750 and a second foundation part 750 which may comprise compartments 155 for ballast. But instead of implementing the holders for the funnel structure 760 as beams fitted in holders, they are now implemented as support members 751 that run along the first foundation part 750 and the second foundation part 750. This means that the funnel structure 760 can form-lock thanks to its integrated guiding members 754 with the support members 751.

The advantage of the construction as shown in FIGS. 7 and 8 is that the potentially difficult installation of the beams 201 can be avoided. However, this construction requires some more accuracy in the relative positioning between the first foundation part 750 and the second foundation part 750 in order for the funnel structure 760 to really form-lock to the support construction. The positioning can be made easier if the height or width of the support members 751 are adjustable, such as if they can be pulled in or out from the first and second foundation part 750.

FIG. 9 shows a further embodiment of the system. The exit pipe 301 may be in the funnel structure 950 on one side. This means that the sleeve 953 may be adapted to redirect the stream 110. This embodiment would work with the embodiment shown in FIG. 2 too.

FIG. 10 shows a further embodiment of the system. The funnel 963, 964 and the sleeve 961, 962 in the funnel structure comprise now two separate parts. The two separate parts can be brought together from different sides of the blowout location 102. In this manner, the parts of the funnel 963, 964 can be conveniently lowered first and the lowered funnel can be pushed in place (cf. arrows in FIG. 10) to restrict the spillout location 102. The inventor believes that this kind of arrangement can substantially reduce the forces required for restricting the blowout location 102 since the funnel does not need to be pushed throughout the stream 110 but the stream 110 is a sort of captured by the funnel from around, like a manacle.

The funnel structure 250, 950, 961, 962, 963, 964 may also comprise means for disjoining an oil pipe. Suitable means include but are not limited to a mechanical saw, and drilling or cutting tools. The upper end of the pipe may be removed from above the sleeve or from the side of the sleeve, depending on the location of the exit pipe 301. The removal is preferably carried out at a free location i.e. where the exit pipe 301 is not located.

The assembling of the system in great depths, as well as the filling of the compartments with ballast, can be carried out by using submarine vessels. The heavier structures can be let fall down from a suitably equipped marine vessel ship in a controlled manner.

Modifications and substitutions by one of ordinary skill in the art are considered to be within the scope of the present invention, which is not to be limited except by the allowed claims and their legal equivalents.

Claims

1. A system for controlling a blowout location at an offshore oilfield, comprising:

a support construction that is movable next to a blowout location in an offshore oilfield and that can be set to rest in seabed, the support construction comprising: a) a first foundation part and a second foundation part that are located at a distance from each other; b) support members that are located at a distance from each other; and

a funnel structure that is movable along the support members, the funnel structure comprising connecting members that are form-locking with the support members;

and wherein:

the first foundation part, the second foundation part and the support members are so configured that the blowout location can be restricted a) between the first foundation part and the second foundation part and b) between the support members;

the funnel structure a) is movable along the support members from a side position to above the blowout location and b) is dimensioned to restrict the blowout by redirecting flow from the blowout into an exit pipe; and

the funnel structure and the support construction are so dimensioned that when the funnel structure is located on top of the blowout location, the system remains substantially stable to enable restricting the blowout.

2. A system according to claim 1, wherein: at least one of the first foundation part and second foundation part comprises at least one compartment that is fillable with ballast.

3. A system according to claim 1, wherein: the support members are rod-like members around which the funnel structure are form-locked.

4. A system according to claim 1, wherein: the support members run between holders at the first foundation part and the second foundation part.

5. A system according to claim 1, wherein: the support members are elongated guide members which form-lock with the funnel structure.

6. A system according to claim 1, wherein: each of the support members are arranged to run along the first foundation part or the second foundation part.

7. A system according to claim 1, wherein: the funnel structure comprises a vertically movable funnel.

8. A system according to claim 1, wherein: the system further comprises adjusting members to adjust the height of the support members from the seabed.

9. A method for controlling a blowout location at an offshore oilfield, comprising the steps of:

bringing a system according to preceding claim 1 to an offshore oilfield;

positioning the first foundation part and the second foundation part of the system to rest in seabed at opposite positions around the blowout location;

attaching a funnel structure in a form-locked manner to the system at an away position from the blowout location;

moving the funnel structure along support members of the system until the funnel structure is on top of the blowout location; and

controlling the blowout location by redirecting flow from the blowout with the funnel structure into an exit pipe.

10. A method according to claim 9, further comprising the step of: adjusting the height of the funnel structure.

11. A method according to claim 9, further comprising the step of: lowering the funnel structure to the blowout location.

12. A method according to claim 9, further comprising the step of: increasing inertia of the system by adding ballast to the system.

13. A method according to claim 9, further comprising the step of: anchoring the system to seabed.

14. A method according to claim 9, further comprising the step of: adding at least one extension to the first foundation part or to the second foundation part.

15. A method according to claim 9, further comprising the step of bringing the funnel structure together from different sides of the blowout location.