WO1998035875A1

WO1998035875A1 - Device by production vessel for oil and/or gas

Info

Publication number: WO1998035875A1
Application number: PCT/NO1998/000046
Authority: WO
Inventors: Knut Erik BØRSETH; Arne Smedal
Original assignee: Hitec AS; PGS Offshore Technology AS
Current assignee: Hitec AS; PGS Offshore Technology AS
Priority date: 1997-02-13
Filing date: 1998-02-09
Publication date: 1998-08-20
Anticipated expiration: 1999-08-13
Also published as: NO970658D0; AU5887298A; NO970658L

Abstract

A production/drilling ship (30) has an opening (26, 22') extending vertically therethrough, which is partially formed by the bore (22') of a sleeve-shaped adapter (22) with several through bores (20a, 20b), whose lower ends are formed for connection to one first end each, of a corresponding number of through channels (16a, 16b) of a submerged buoy (10), whose channels (16a, 16b) are connected by their other ends to one each, of a corresponding number of pipelines (12a, 12b) leading to one wellhead each, of a corresponding number of wellheads on the seabed. The adapter (22) is rotatably supported about its longitudinal axis (A) in a portion (30) of the ship's hull, and is connected by the upper ends of its bores (20a, 20b) to the lower ends of bore-forming elements (40) (hoses), whose upper ends are connected to a pipe system (42) fixed to the ship. To be able to absorb the torsional forces caused by the bore-forming elements (40) being stationarily positioned by their lower ends, while their upper ends follow the rotational movements of the ship (30) caused by wind and surface current forces, each of the bore-forming elements (40) are formed with resilient flexibility and over-sized lengths.

Description

DEVICE BY PRODUCTION VESSEL FOR OIL AND/OR GAS

The present invention relates to a device by a production ship for oil and/or gas. Some production ships of this kind are formed with a downward open recess for a buoy which constitutes a connection device for pipe systems and mooring lines, and in which the connection device is formed as a collecting and distributing body for the connection of two or more pipelines, each leading to a wellhead on the seabed for the delivery of oil/gas to the collecting and distributing body, and from there on, to a pipe system aboard the production ship. The pipe system comprises a number of tubular transport lines, the number of which corresponding to the number of active wellheads on the seabed, and the collecting and distributing body has a number of through channels, which may correspond, in number, to the number of active wellheads.

The collecting and distributing body which exhibits sufficient buoyancy is preferably formed with an upward tapering conical shape as a buoy, and the downward open receptional recess in the bottom portion of the ship's hull has a complementary shape, so that an advantageous

CORRECTE guiding effect is achieved when the buoy is to be brought into engagement with the receptional recess of the ship.

The engagement of the upward tapering conical buoy in the underlying, complementarily conical receptional recess of the ship is accomplished by the buoy being pulled, in a manner known in itself, into the bottom portion of the ship, in which is established, in the position of use, a non-pivotal, non-displaceable con- nection between the buoy and a therewith coaxial, ship- born, sleeve-shaped adapter, which is pivotally supported about its upright longitudinal axis in the bottom portion of the ship's hull, and which is provided, in a thick-walled outer circumferential portion, with bores, channels, pipes or similar for the transfer of oil/gas to an abovelying pipe system on the ship.

The complementary engagement of the buoy in the receptional recess of the ship and the swivel arrangement provided thereto, provide an efficient mooring of the ship, which may pivot for example 360° about the upright axis of the buoy/recess.

Known swivel arrangements between the overlying pipe system of the ship and the underlying buoy are very expensive. Therefore, according to the present invention, it has been aimed at absorbing, by considerably cheaper means, the torsional forces, which the bore-forming elements of the pipe system of the ship are subjected to by rotations of the ship, depending on wind and currents, about the axis of the buoy/adapter.

This object is realised, according to the invention, by means of a ship-born pipe system which distinguishes itself by the features stated in the characterizing part of claim 1.

Between the upper connecting nozzles of the adapter and an overlying pipe connection device for individual con- nection of through bore-forming tubular elements, a substantial longitudinal section of each bore-forming element of a flexible hose length is formed, and each bore-forming element has a longitudinal extent which substantially exceeds the distance between the upper connecting nozzles of the adapter and the abovelying connection device. The longitudinally over-sized hoses may be able to absorb variations in positional deviations between parts fixed to the ship and parts fixed to the buoy, corresponding to for example a 360° rota- tion of the ship about the buoy.

In order not to let the hoses buckle excessively into the central area of the manifold, thus blocking the lowering of for example a drill string, the central area of the manifold may be provided with one or two sleeve elements which has/have a vertical bore extending therethrough. The outer cylindrical side wall of the sleeve elements will prevent the hoses from moving into this central area when the ship turns.

The invention will be explained in the following in connection with non-limiting examples of preferred embodiments which are illustrated in the accompanying drawings, in which:

Fig. 1 shows, in side-view, a production ship which is pivotally moored to a submerged buoy to which pipelines are connected, leading to wellheads on the seabed, the connecting area for the buoy via a complementarily formed bottom recess in the ship's hull and an overlying adapter, manifold etc. , being shown in vertical sectional view;

Fig. 2 shows an enlarged partial side-view in vertical section through the buoy, adapter, surrounding portion of the ship's hull and an abovelying connection ring with parallel ports for the connection of underlying through bores, channels or similar of the adapter and to abovelying torsion absorbing hoses.

Fig. 3 corresponds to Fig. 2, but here the buoy has been omitted, there being shown, according to this figure, a guiding and supporting sleeve on the upper surface of said connecting ring;

Fig. 4 corresponds to Fig. 3, but here, in the upper area of the manifold and hanging down from the fixed pipe system of the ship, is provided a sleeve which blocks this upper area to the hoses when the ship turns.

A submerged connection device for pipe systems and mooring lines, in the following referred to as a buoy 10, Figs. 1 and 2, is formed as a collecting and forwarding body for oil/gas which is supplied to the submerged buoy 10 from a number of not shown wellheads on the seabed, via pipelines 12a and 12b which are indi- vidually connected to the buoy 10 by connections 14a and 14b which are connected to through channels 16a and 16b of the buoy 10, which have, for the forwarding of said oil/gas, upward connections 18a, 18b for the tightening connection to vertical through bores 20a and 20b of a sleeve-shaped adapter 22 with a wide central, through bore 22', the bores 20a and 20b being formed in the sleeve wall and extending parallel to the upright axis of symmetry A of the sleeve. Normally, there will be a greater number of pipelines 12a, 12b, channels 16a, 16b and bores 20a, 20b, which channels and bores may be distributed equidistantly.

The buoy 10 is moored positionally fixed to the seabed by means of anchors 24 in the form of stays. The buoy 10 has an upper main portion 10 ' which extends coni- cally tapering in an upward direction and is arranged to be placed from below into a complementarily shaped recess 26. The buoy 10 has a lower cylindrical portion 10".

The sleeve-shaped adapter 22 is supported, pivotal about its axis of symmetry A, in a portion 30 of the ship's hull, by means of three annular bearings 28a, 28b and 28c placed at separate levels. The buoy 10 is rigidly connected to the sleeve-shaped adapter 22 through the connections 18a, 18b.

The support of the sleeve-shaped adapter 22 in the hull 30 of the ship, and its non-pivotal connection to the buoy 10 result in an efficient mooring of the ship, which may perform a rotational movement about the axis A.

Immediately above the sleeve-shaped adapter 22, and screwed thereto by bolts 32, 32', is a pipe connection ring 34 with ports 36a, 36b positioned corresponding with the bores 20a, 20b of the adapter 22.

The pipe connection ring 34 forms a first transverse end element of a manifold, whose other transverse end element is composed of an upper connecting element 38 fixed to the ship. The torsional force absorbing, hose- shaped, oil carrying elements 40 (the hoses) are connected by the connecting element 38 to the pipelines 42.

To be able to absorb the torsional forces produced by the rotations of the ship about the axis A to the stationary end portions of the bore-forming elements 40, each of the bore-forming elements 40 are formed with at least one longitudinal flexible hose length. In addi- tion each hose is considerably over-sized in length compared to the distance between the two transverse end elements of the manifold, the pipe connecting ring 34 and the connecting element 38.

In the not stressed position the resilient bore-forming elements 40 may individually adopt, because of their over-sized length, a course in the form of a rounded Z, as shown in Figs. 2 - 4.

The resilient flexibility in their not stressed condition and the too great longitudinal extent of the bore- forming elements 40, compared to the distance between their individual connection points 34 and 38 are capable of absorbing the additional stresses caused by the one ends of the hoses being stationary, while the other ends, connected to the ship's hull, are moveable in re- lation to the first ends. However, nothing prevents some of the pipes from being provided with connecting organs, for example 44, with small, cheap individual swivel organs.

To avoid tendencies of tangling and of blocking a cen- tral area above the sleeve-shaped adapter 22, whereby the lowering of for example a drill string - when the ship maybe is used as a drill ship and the buoy 10 is removed - is blocked by tangled hose portions, there is provided, according to Figs. 3 and 4, in the central area immediately above the connecting ring 34 and con- nected thereto, a guiding and suspension sleeve 46 which guides the lower hose portions and whose upper edge forms a suspension edge for the hoses 40 at the first bent portion. This prevents tangling in the area of the sleeve 46, at the same time as provision being made for regulated and controlled course changes by each hose individually and in relation to adjacent hoses.

According to Fig. 4 there is, at the top, a further sleeve 48 hanging down vertically, which is to keep an upper, central portion free of hose bends during the constantly varying courses of the hoses, so that for example a drill string (not shown) does not encounter any obstacles on being placed into the wide bore 22* of the sleeve-shaped adapter 22.

The reference numeral 50, according to Figs. 3 and 4, defines coupling organs between a rigid pipe section 50' and the hose 40. Each such coupling organ 50 may be comprised by a swivel organ. Also the coupling organs 44 may be comprised by a swivel organ.

Claims

C L A I M S

1. A device by production ship for oil/gas and formed with a vertical through recess (26, 22') which preferably allows connection to a connection device for pipe systems and mooring lines, in the form of a buoy (10) which is formed for the collection of oil etc. via pipelines (12a, 12b) and forwarding of the oil etc. via internal channels (16a, 16b) , which channels (16a, 16b) are arranged at their opposite ends to allow connection to one bore (20a, 20b) each, of a sleeve-shaped adapter (22) which is pivotally supported in a surrounding portion (30) of the ship's hull, and which forms, by the individual connecting of its bores (20a, 20b) to the internal channels (16a, 16b) of the submerged buoy (10) , and its pivotal support, an upright mooring axis (A) for the ship, and in which the vertical through recess (26, 22') may be utilized for passing a drill string if the ship, for example temporarily, is to be used as a drill ship, and in which there is mounted, between the sleeve-shaped adapter (22) and overlying, fixedly mounted pipelines (42) incorporated in the pipe system of the ship, flexible, bore-forming, pipe-like, oil carrying elements (40) , for example in the form of flexible, resilient hoses, ch a r a c t e r i z e d i n that each flexible, bore-forming element (40) is considerably over-sized longitudinally and follows a winding/undulating, orderly course in the space between the sleeve-shaped adapter (22) and said fixedly mounted pipelines (42) with the aim of being able to absorb substantial torsional stresses originating from the fact that the one ends of the flexible, bore-forming elements are connected to the sleeve-shaped adapter (22) which in turn is connected to the buoy (10) , while the opposite ends of the flexible, bore-forming ele- ments (40) are connected to a pipe-element (38) fixed to the ship.

2. A device according to claim 1, ch a r a c t e r i z e d i n that each bore-forming element (40) comprises at least two longitudinal joined portions extending in their extensions, in which each point of connection has a swivel device (50) arranged thereto.

3. A device according to claim 2, ch a r a c - t e r i z e d i n that each bore-forming element portion comprises a straight portion and a 180° bend, and that each joined, bore-forming element (40) preferably lies in one (vertical) plane.

4. A device according to any one of the preceding claims, ch a r a ct e r i z e d i n that the bore- forming elements (40) are connected to a connecting ring (34) formed with ports (36a, 36b) corresponding in number and positions to the bores (20a, 20b) of the sleeve-shaped adapter (22) , to which said connecting ring (34) is connected.

5. A device according to any one of the preceding claims, ch a r a c t e r i z e d i n that as an upright coaxial extension of the sleeve-shaped adapter (22) is arranged a guiding and suspension sleeve (46) .

6. A device according to any one of the preceding claims, ch a r a c t e r i z e d i n that from the connection element (38) downward is preferably projecting a central sleeve (48) .