Wells – Submerged well – Connection or disconnection of submerged members remotely...
Reexamination Certificate
2000-05-25
2001-11-27
Bagnell, David (Department: 3673)
Wells
Submerged well
Connection or disconnection of submerged members remotely...
C166S359000, C166S367000, C405S224000, C405S224200, C137S236100
Reexamination Certificate
active
06321844
ABSTRACT:
BACKGROUND OF THE INVENTION
The subject of this invention is a device with a hybrid riser for the sub-sea transportation of petroleum products.
The technical sector of the invention is the field of the construction of installations for the extraction of petroleum products from the sub-sea sub-soil.
The present invention relates more particularly to a pipeline system or device for transporting petroleum products extracted from one (or more) well(s) drilled in the sub-sea sub-soil to a floating or semi-submersible (surface) structure, particularly to a floating production, storage and off-loading (F.P.S.O.) vessel.
The invention is particularly applicable to that part of the pipeline which extends from the surface of the sea bed up to the floating or semi-submersible structure.
BRIEF SUMMARY OF THE INVENTIONS
One objective of the present invention is to provide such a device which is well suited to great depths, particularly depths of 750 meters or more, and to its method of installation.
In order to raise to the surface petroleum products which have been extracted in deep waters, it is known practice to make use of rigid pipelines, particularly made of steel, whereas for raising products which have been extracted from shallower waters, it is known practice to make use of flexible or deformable pipes.
In particular, the use in deep waters of risers which extend more or less vertically and are more or less rigid is known.
Such risers, sometimes known as hybrid risers, may consist—as depicted diagrammatically in cross-section in FIG.
9
—of a vertical bundle of steel pipes which are, at least in part, supported by buoyancy means; such risers; comprise a straight tubular central structure made of steel which extends vertically and may be filled with air in order to play a part in buoyancy, and which is surrounded bit syntactic buyoancy composite material over at least part of its height, for example in the form of hollow cylindrical modules stacked (and/or strung) around the central tubular structure; this syntactic material contributes to the buoyancy; production pipelines transporting the extracted products to the surface and service pipelines transporting fluids and sometimes power towards the sea bed extend around and along the length of the central structure, through the syntactic material; these lengths of peripheral pipeline for vertical transport are connected at their lower end to essentially rigid and metal pipelines running along the sea bed, down to the extraction well, and are connected at their upper end to lengths of flexible pipeline extending up to the floating structure, generally via gooseneck connections.
Such structures of risers in which the transport pipelines are surrounded by syntactic material are particularly beneficial for raising petroleum products from the sea bed because the syntactic material acts as thermal insulation, thus limiting the cooling of the “crude” by the cold sea water, and thus limits the formation of undesirable products (paraffin, hydrates) in the pipes.
Because these risers, which extend up to within a few tens of meters from the surface, are very long (tall), that is to say several hundreds of meters long, it. is important that their deformation (curvature) resulting in particular from the hydrodynamic action of the currents and their positioning under the water be controlled, so as to keep the displacement of the upper end of the risers to within acceptable limits; failing this, excessive loadings on the flexible pipelines connecting these risers to the floating structure may result; impacts between two risers located close together, and/or undesirable overlapping (or intertwining) of the riser and other string-like structures (umbilical cables, other risers for example) located close to it may also result.
The problem posed consists, in particular, in proposing a highly effective system for anchoring the base of the riser to the sub-sea sub-soil.
One objective the invention consists in proposing a system for attaching the base of the riser to the sub-sea sub-soil which is easy and inexpensive to implement at great depth.
A further objective the invention consists in proposing a system for attaching the base of the riser to the sub-sea sub-soil which is easy and inexpensive to implement at great depth.
Another objective of the invention consists in proposing a system for anchoring the base of the riser to the sub-sea sub-soil which allows connection between anchoring means and the base of the riser which may be either articulated or fixed.
Another objective of the invention consists in proposing a system for anchoring the base of the riser to the sub-sea sub-soil which is of low cost (in terms of hardware and operation), so that it can be abandoned after use.
According to a first aspect of the invention, the riser is fixed to the sub-soil by a friction anchor; for this, the anchor has a large (and preferably ribbed) contact area with the sub-soil.
According to another aspect, the riser is fixed to the sub-soil by a gravity anchor; for this, the anchor has a great mass (several tonnes or tens of tonnes at least).
Preferably, in both cases, the anchor has a more or less cylindrical shape, one base of which is open.
In the case of the friction anchor, the anchor may essentially consist of an elongate shell with a ribbed cylindrical wall, of polygonal cross-section, which is closed (hermetically) at one end, by a wall, for example a planar wall, in the shape of a disc of polygonal contour which, in the position of use (of anchorage) forms the upper part; the anchor is installed as follows: the anchor is placed on the sea bed via the open face provided at the bottom end of the anchor; the internal space delimited by the walls of the anchor is partially evacuated (by pumping or sucking out water using a pump) and the anchor then sinks (more or less vertically) into the soil under the effect of the hydrostatic pressure applied to it, until its cylindrical lateral walls have fully (or at least substantially) entered the soil; in general, the bottom end of the anchor will be sunk at least 5 meters into the soil, and usually will be sunk of the order of 10 to 25 meters.
Bearing in mind the large area (of the order of 100 to 1000 m
2
) of the internal face and of the external face of the walls of the anchor which are sunk into the soil, significant resistance to pulling out (of the order of several tens or hundreds of tonnes) is obtained, because of the friction forces exerted by the sub-sea sub-soil on these walls; furthermore, because the (sea-water-filled) residual cavity, delimited by the lateral or peripheral walls of the (bell-shaped) anchor and by the upper wall, is isolated more or less hermetically from the sea water surrounding the anchor, an additional resistance to pulling out is obtained as a result of a suction or suction-cup effect.
According to another aspect of the invention the riser for transporting petroleum products is attached by an anchor which is installed by a method in which the anchor is sunk into the sub-sea sea-bed by creating an under pressure when partially evacuating the cavity delimited by the soil and by the upper part of the bell-shaped anchor.
In the case of the use of a gravity anchor, this anchor may essentially consist of a cylindrical shell of polygonal cross-section, the upper base of which is open and the lower base of which is at least partially closed.
Such an anchor forms a container capable of holding a sizeable amount (several hundreds of tonnes) of a heavy bulk material such as a metal ore or residue from the processing of such an ore.
According to another aspect of the invention the riser for transporting petroleum products is attached by an anchor which is installed by a method in which a heavy material is deposited under gravity in the shell of the anchor by conveying this material through the hollow central tubular structure of the riser.
REFERENCES:
patent: 2895301 (1959-07-01), Casagrande et al.
patent: 3263641 (1966-08-01), Stimson
patent: 3372409 (1968-03-01), Manning
patent: 3535883
Alliot Vincent
Thiebaud François
Bagnell David
Ladas & Parry
Lee Jong-Suk
Stolt Comex Seaway
LandOfFree
Hybrid riser and method for sub-sea transportation of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Hybrid riser and method for sub-sea transportation of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hybrid riser and method for sub-sea transportation of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2615628