There is described a device for a collection system for leak fluid from a petroleum well, wherein a cap arranged to accommodate a wellhead installation is connected to a fluid line, and a wellhead is provided with a suction substructure, more particularly in that the cap is fluid sealingly and releas- ably joined to the suction substructure. The invention further comprises a method for connection of a collection system for leak fluid from a petroleum well to a wellhead, and also use of a suction substructure as a fluid-sealing interface between a petroleum well and a collection system for leak fluid.

On damage to a Blow Out Preventer (BOP) arranged on a wellhead on a subsea oil or gas well, or on a marine riser extending from the wellhead and up to a surface installation, there may be a need to be able to connect a collection equipment to the wellhead for collection of oil and/or gas flowing uncontrolled out of the well. The wellhead exhibits according to prior art a partly very disorderly interface toward the surroundings, and forming a pressure tight joint between the wellhead and an element able to connect a collection equipment to the wellhead of the wrecked well, presents great technical challenges. The object of the invention is to remedy or reduce at least one of the disadvantages of the prior art, or at least to provide a useful alternative to the prior art .

The object is achieved by the features disclosed in the below description and in the subsequent claims .

There is provided a device for a collection equipment for oil and/or gas leaks from a subsea well, as a cap provided with fluid lines connected to a surface installation is arranged to be able to be connected fluid tight to a wellhead.

From NO patent no. 313340, in its entirety included as a reference here, is known a suction substructure (Conductor Anchor Node = CAN) . The task of this suction substructure is to provide a larger contact surface between the upper part of the conductor casing and the surrounding seabed mass, thereby increasing the stability of the wellhead. The suction substructure is typically cylinder shaped having a diameter of around 8 metres, while a conductor casing diameter is in the range of 0.75-0.90 m (30-36 inches). The suction substructure exhibits a regular, well-defined interface toward the surroundings. The suction substructure footprint is typically circular, but may per se also be polygonal, and the dimensions are known for the operator of the well. The suction substructure extent is larger than the horizontal projection of the other elements constituting the wellhead and which cannot be removed before the collection equipment is connected to the wellhead.

The suction substructure forms a seat for said cap, as the cap being disposed over the blowout preventer subsequent to connected riser being disconnected from the blowout preventer and removed. The cap is provided with a contact portion ar- ranged to be able to connect sealingly against the suction substructure .

The cap and the suction substructure are provided with means arranged to enter into releasable, locking engagement with each other to thereby prevent the cap from being accidentally lifted from the seat.

In a first aspect the invention relates more specifically to a device for a collection system for leak fluid from a petroleum well, wherein a cap arranged to accommodate a wellhead installation, is connected to a fluid line, and a wellhead is provided with a suction substructure, characterised in that the cap is fluid sealingly and releasably joined to the suction substructure.

The suction substructure may be provided with a seat arranged for receipt of an abutment arranged on the cap. Thereby the cap may be able to be guided to the correct position during joining.

The cap may be provided with a plurality of first locking elements arranged to be able to enter into releasable engagement with respective second locking elements arranged on the suction substructure. Thereby an overpressure may be built up inside the cap without the fluid seal ending.

The abutment may be formed as an in an operational position lower edge portion on the cap. This makes for a simple design of the cap .

The seat may be formed as an edge portion on an end cover on the suction substructure. The edge portion may simply be formed as a guiding seat, for example by a rounded or conical shape . In a second aspect the invention relates more particularly to a method for connection to a wellhead a collection system for leak fluid from a petroleum well, wherein a cap arranged to accommodate a wellhead installation is connected to a fluid line and a wellhead is provided with a suction substructure, characterised in that the method comprises the following steps :

a) releasing and removing a riser from the wellhead installation; and

b) lowering the cap over the wellhead installation to a fluid sealing contact against the suction substructure.

The method may further comprise the step of :

c) releasably fastening the cap to the suction substructure by means of a plurality of locking elements. Thereby the system can stand an internal pressure build-up without leakage occurring between the cap and the suction substructure.

In a third aspect the invention relates more particularly to the use of a suction substructure as a fluid-sealing interface between a petroleum well and a collection system for leak fluid.

In the following is described ah example of a preferred embodiment illustrated in the accompanying drawings, wherein:

Fig. 1 shows in a side view a principle sketch of a petroleum well provided with a suction substructure at the wellhead, and wherein a damaged riser is removed from a blowout preventer; and

Fig. 2 shows in a side view a principle sketch of the petroleum well where a collection system according to the invention is arranged on the wellhead. In the Figures the reference numeral 1 indicates a subsea wellhead arranged above a seabed 4 and provided with a wellhead installation 2, typically a blowout preventer (BOP) . A riser 3 extends in a per se known manner from the wellhead installation 2 and up to a surface installation (not shown) . The wellhead 1 is provided with a suction substructure 5. A collection system 6 is by connection to the wellhead 1 arranged for collection of leak fluid WF forcing its way uncontrolled up from a petroleum well W.

The wellhead 1 is in a per se known manner provided with a conductor casing 11 having an upper casing portion 111 extending up over the seabed 4. A wellhead pipe 12 extends in a per se known manner internally in the conductor casing 11 downward in an underground structure 41 and forms the pressure barrier of the well W against the surrounding structure 41. The wellhead installation 2 is by means of a wellhead connector 21 in a per se known manner fastened to an upper end portion 121 of the wellhead pipe 12 as this extends up above the end of the conductor casing 11.

The wellhead 1 is supported by a suction substructure 5. This is in its entirety described in NO 313340 and in its entirety included here by reference. In its simplest form the suction substructure 5 is formed by a cylindrical body 51 provided with an end cover 52 closing an upper end of the cylindrical body 51. The conductor casing 11 is led through the end cover 52 in a conductor casing passage 53. An edge portion of the end cover 52 forms a seat 54 for a cap 61 being comprised by the collection system 6.

In an operational position lower end of the cap 61 is provided with an abutment 611 being complementary to the seat 54, the abutment 611 sealing tightly against the seat 54 when the cap 61 is resting on the suction substructure 5. It is obvious for a person versed in the art to provide the seat 54 and/or the abutment 611 with appropriate sealing elements (not shown) .

In an operational position upper end of the cap 61 is provided with connection elements for a fluid line 62 arranged to be able to be connected to a remote installation (not shown) , such as a ship, being provided with means for receipt of the leak fluid WF flowing up into the cap 61 and on through the fluid line 62.

To ensure that the cap 61 is held in a fluid sealing position on the suction substructure 5, the cap 61 is locked to the suction substructure 5 by means of locking elements 612, respectively 55, arranged on the cap 61, respectively on the suction substructure 5. The locking elements 55, 612 are operated in an appropriate manner, typically by means of a remote controlled vehicle (ROV) .

When a leak situation arises in a well W, and leak fluid WF flows uncontrolled from the well W, the riser 3 from the wellhead 1 is disconnected such that the wellhead installation 2, typically the blowout preventer, does not exhibit upwards or outwards extending elements able to hinder the installation of the collection system 6 according to the invention. The cap 61 is thereafter guided down over the wellhead 1 to abutment against the seat 54 of the suction substructure 5, and the cap 61 is fastened to the suction substructure 5 by means of the locking elements 55, 612. The leak fluid WF flowing uncontrolled out through the wellhead 1 is thereby captured by the cap 61 and led away through the fluid line 62.