Mooring Assembly

This application is a continuation of U.S. application Ser. No. 17/600,741, which is herein incorporated by reference in its entirety, and which is a 371 National Phase entry of PCT/AU2020/050355 filed Apr. 9, 2020, which claims priority to AU 2019901242 filed Apr. 10, 2019.

The present invention relates to mooring assembly for attaching a vessel to a subsea well. The present invention also relates to a method for fitting a mooring assembly for a vessel to a subsea well as well as a method for mooring a vessel to a subsea well, wherein, when moored, the vessel is capable of rotational movement around the subsea well. The mooring assembly allows for control of and production from the well to the vessel.

The cost of current solutions for exploiting natural resources in the oil and gas sector means that many smaller scale oil and gas fields cannot be developed economically.

The present invention seeks to provide a solution that will safely enable the commercialisation of smaller scale oil and gas fields by allowing for a well to be produced without many of the components that are traditionally required.

According to a first aspect of the present invention, there is provided a mooring assembly for attaching a vessel to a subsea well including a well conductor, the mooring assembly comprising:

In accordance with a second aspect of the present invention, there is provided a method for fitting a mooring assembly for a vessel to a subsea well including a well conductor, the method comprising the steps of:

In accordance with a third aspect of the present invention, there is provided a method of for mooring a vessel to a subsea well, the method comprising the step of attaching the vessel to the subsea well via a mooring assembly as described herein and wherein, when moored, the vessel is capable of rotational movement around the subsea well.

It is to be recognised that other aspects, preferred forms and advantages of the present invention will be apparent from the specification including the detailed description, examples, drawings and claims provided below.

According to a first aspect of the present invention, there is provided a mooring assembly for attaching a vessel to a subsea well including a well conductor, the mooring assembly comprising:

For the purposes of the present invention the term “well conductor” may comprise any well conduit, housing, pipe or any other similar component adapted to provide the primary support structure of a subsea well and includes a conductor pipe or conductor casing located at or near the wellbore. The well conductor may include a portion that is located above the wellbore at the subsea surface hole. The well conductor may also include a portion that is located below the wellbore.

Preferably, the mooring assembly defines a single mooring point on the seabed.

The mooring assembly may be adapted to allow a vessel moored thereto to weather vane through 360 degrees. Preferably, the mooring assembly is adapted to allow for a vessel moored thereto to weather vane in either direction.

Preferably, the mooring assembly comprises a guide base such as permanent guide base.

Preferably, the housing defines a conduit for the well conductor.

Preferably, the conduit is centrally located in the housing.

Preferably, the conduit comprises a circular cross section.

Preferably, the conduit defines an upper end and a lower end and an inner surface therebetween with a profile that is sized and shaped to allow the housing to form a sleeve or sheath around the well conductor.

Preferably, the housing comprises fixing means to enable it to be fixed in position relative to the well conductor.

Preferably, the fixing means is adapted to allow the housing and the well conductor to form a frictional engagement. Even more preferably, the fixing means comprises a first mating surface provided on the housing and is compatible with a second mating surface on the well conductor. In one particular form of the invention a first mating surface is provided on the inner surface of the housing and is compatible with a second mating surface provided on the outside surface of the well conductor. The first mating surface can comprise a pin, a ball, a bore, a projection, a blade or a channel.

Preferably, the first mating surface is compatible with the second mating surface comprising a pin, a ball, a bore, a projection, a blade or a channel.

Preferably, the housing further comprises a locating means for locating a well casing therein. In this regard, when installing a well casing from above, the locating means makes it easier to land and install the well casing or at least assists with guiding the well casing into the wellbore.

Preferably, the well casing is a well surface casing.

Preferably, the locating means is adapted to centre the well casing in the housing, or, when the housing comprises a conduit, in the conduit.

Preferably, the locating means is provided integrally with the conduit.

Preferably, the locating means is located at or towards the upper end of the conduit.

Preferably, the locating means comprises a contact surface for the leading end of the well casing and extends outwardly from the inner surface of the conduit.

The contact surface may extend around the entirety of the upper end of the conduit or extend around a part of the upper end of the conduit.

Preferably, the locating means comprises a projection such as a lip or shoulder.

Preferably, the locating means comprises a circumferential projection.

Preferably, the housing further comprises a guide means to further assist with landing a casing in the housing.

Preferably, the guide means comprises a body defining a bore with a wider opening than the opening at the upper end of the conduit.

Preferably, the guide means comprises a tube, funnel, drum funnel or bucket member.

Preferably, the guide means is located immediately adjacent to and above the locating means. Even more preferably, the guide means and the locating means are provided integrally.

Preferably, the housing defines a mounting point for the rotatably mounted vessel attachment point. Preferably, the mounting point is located on the outer surface of the conduit. Preferably, the mounting point is a suitably sized and shaped surface that is compatible with the rotatably mounted vessel attachment point.

Preferably, the base comprises at least one engaging means for the subsea ground surface. Even more preferably, the base comprises a plurality of said engaging means.

The engaging means for the subsea ground surface at least limits the movement, such as lateral and/or rotational movement, of the base relative to the subsea ground surface. Preferably, the engaging means fixes the mooring assembly in position relative to the subsea ground surface. In this regard, it is preferred that the engaging means locks the mooring assembly to the subsea ground surface e.g. seabed such that it cannot rotate, move axially (pull-out) or laterally (tilt).

Preferably, the engaging means for the subsea ground surface are arranged around the base. Even more preferably, said engaging means are arranged equidistantly apart around the base.

Preferably, the engaging means for the subsea ground surface comprises a projection such as a foot, leg, stab or blade.

The engaging means for the subsea ground surface may comprise at least one arm or strut that extends laterally from the base to allow the interface to extend over a larger area of subsea ground surface. When said engaging means comprises an arm or strut, the projection maybe provided at or near the distal end of the arm or strut.

Preferably, the engaging means for the subsea ground surface is adapted to penetrate the subsea ground surface, when in use. Alternatively, the engaging means for the subsea ground surface may be adapted to receive additional anchoring elements, such as a stake, pile, screw or a spike to increase the strength of the engagement with the subsea ground surface.

The base may comprise a spacing means to allow the formation of void between the base and the subsea ground surface, when in use.

The spacing means may be the projection or an additional feature of the base.

Preferably, the spacing means extends from the lowermost surface of the base.

The void allows for the cement returning to the surface, when cementing a well conductor therein, to be visually confirmed.

When no void is formed or the returning cement cannot otherwise be visually confirmed, the housing may further comprise at least one inspection port or observation window to allow for the cement return to be confirmed.

Preferably, the void or inspection port is adapted to allow for the passage of a fixing material, such as mortar, glue or concrete to an area adjacent to a lower portion of the base. Preferably, said area is one or more of the areas between the base and the subsea ground surface, the base and another feature of the mooring assembly and/or the base and the subsea well, such as the well conductor.

Preferably, the base comprises a skirt that extends out radially from the main longitudinal axis of the housing. Preferably, the skirt is located at the lower end of the conduit and is provided integrally with one or more of the conduit, the engaging means and/or the spacing means.

Preferably, the base acts to reinforce the mooring assembly and/or performs a supporting role for at least one other component of the mooring assembly, such as the rotatably mounted vessel attachment point and more particularly the bearing member, described in more detail hereunder.

Preferably, the rotatably mounted vessel attachment point is mounted to the housing. Even more preferably, the rotatably mounted vessel attachment point is mounted to the housing at a point below the locating means.

Preferably, the rotatably mounted vessel attachment point comprises at least one bearing member. Even more preferably, the rotatably mounted vessel attachment point comprises a plurality of bearing members.