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Patent Searching and Data


Title:
A RISER HANGER AND METHOD
Document Type and Number:
WIPO Patent Application WO/2017/204649
Kind Code:
A1
Abstract:
A riser hanger (1) for connecting a riser (2) to a host facility (8), the riser hanger (1) comprising a pivot joint (3), and a fluid conduit (5, 6) connected to the pivot joint (3) for pivotable movement and connectable to a riser end for transporting fluid from the riser (2) to a host facility (8), the fluid conduit (5, 6) comprising a flexible hose (6).

Inventors:
HOVLAND, Erlend (Bergåsveien 14, 4016 Stavanger, 4016, NO)
BAARHOLM, Rolf (Breisynveien 23, 7021 Trondheim, 7021, NO)
Application Number:
NO2016/050106
Publication Date:
November 30, 2017
Filing Date:
May 26, 2016
Export Citation:
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Assignee:
STATOIL PETROLEUM AS (Forusbeen 50, Stavanger, N-4035, NO)
International Classes:
E21B19/00; B63B27/34; E21B17/01
Domestic Patent References:
WO2001030646A12001-05-03
WO1998049050A11998-11-05
WO2013189496A12013-12-27
Foreign References:
US20100006300A12010-01-14
Attorney, Agent or Firm:
WHITE, Duncan (Marks & Clerk LLP, Fletcher House Heatley Road, The Oxford Science Park, Oxford Oxfordshire OX4 4GE, OX4 4GE, GB)
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Claims:
CLAIMS:

1 . A riser hanger for connecting a riser to a host facility, the riser hanger comprising:

a pivot joint; and

a fluid conduit connected to the pivot joint for pivotable movement and connectable to a riser end for transporting fluid from the riser to a host facility, the fluid conduit comprising a flexible hose. 2. The riser hanger according to claim 1 , wherein the pivot comprises a ball joint.

3. The riser hanger according to claim 1 or 2, wherein the flexible hose is an unbonded flexible hose. 4. The riser hanger according to claim 1 , 2 or 3, wherein the flexible hose is an armoured flexible hose.

5. The riser hanger according to any one preceding claim, comprising a connector affixed to the pivot joint and providing a connection for the riser end and for an end of the flexible hose to complete the fluid path.

6. The riser hanger according to any one preceding claim and adapted for use with a disconnectable buoy for Floating Production Storage and Offloading (FPSO) purposes, in particular turret/buoy systems for FPSOs.

7. The riser hanger according to any one preceding claim and further comprising an arm pivotally connecting the fluid conduit to the pivot joint.

8. A method of connecting a riser end to a host facility, comprising connecting the riser to a pivot joint connected to the host end facility and providing a fluid path from the riser end to the host facility via a fluid conduit comprising a flexible hose.

Description:
A RISER HANGER AND METHOD

Field of the Invention The invention relates to offshore hydrocarbon production systems, in particular to rigid risers and means to connect such risers to a host facility.

Background For deep water applications there is a cost reduction potential by utilizing rigid risers (e.g. steel catenary risers or Steel lazy wave risers) instead of flexible risers. Flexible risers are also prone to a number of failure modes, so in deep water the rigid risers have a robustness advantage. However, there are also many design issues with rigid risers, and one of these challenges is related to riser hang off which is used to connect the riser to the host facility. The hang-off system must be able to perform the following three basic functions:

1 . Support the riser weight

2. Accommodate the rotation between the riser and the host facility

3. Transfer fluid between the riser and the host facility

There are basically two riser hang off methods commonly used today, flexible joint and stress joint. The flexible joint has some issues related to leak potential and the stress joint is challenging to engineering and is relatively heavy and large. The maximum allowable rotation angle is also an issue for both alternatives. For some applications weight and space is limited in the riser hang off area.

A semi-flexible system is described for example in US 2010/0006300 which provides a hang-off arrangement for catenary risers suspended from an offshore or inshore platform by using a rigid spool with limited flexibility. In particular, the prior art tailored for connection to Tension Leg Platforms (TLP) or semi-submersible platforms.

A common problem for areas with surface ice, ice bergs, typhoons or hurricanes (e. g. Bay du Nord) is that the Floater needs to be disconnectable. The risers and mooring system are hung off at a flotation device (Riser Mooring Buoy) and the space and weight margins of the buoy are particularly limited. Hence, increased flexibility is required for these areas.

SUMMARY

The invention provides a riser hanger for connecting a riser to a host facility, the riser hanger comprising, a pivot joint, and a fluid conduit connected to the pivot joint for pivotable movement and connectable to a riser end for transporting fluid from the riser to a host facility, the fluid conduit comprising a flexible hose.

In accordance with an embodiment of the invention an armoured and/ or unbonded flexible "hose" is provided at the top of the riser. Armoured or unbonded flexible hose, allows reduced length of the flexible member, reducing the amount of flexible member that requires inspection. In particular, the required length can be determined in advance by calculating the likely maximum deflection of the riser to the platform to which it is connected.

The invention can be tailored to fit on a disconnectable buoy for Floating Production Storage and Offloading (FPSO) purposes, in particular turret/buoy systems for FPSOs.

The pivot may comprise a ball joint.

The flexible hose may be an unbonded flexible hose. The flexible hose may be an armoured flexible hose.

The riser hanger may comprise a connector affixed to the ball joint and providing a connection for the riser end and for an end of the flexible hose to complete the fluid path. The riser hanger may comprise an arm pivotally connecting the fluid conduit to the pivot joint.

The riser hanger may be adapted for use with a disconnectable buoy for Floating Production Storage and Offloading (FPSO) purposes, in particular turret/buoy systems for FPSOs. The invention also provides a method of connecting a riser end to a host facility, comprising connecting the riser to a pivot joint connected to the host end facility and providing a fluid path from the riser end to the host facility via a fluid conduit comprising a flexible hose.

DRAWINGS

Figure 1 shows a perspective view of a riser connected to a platform in accordance with an embodiment of the invention.

Detailed description

A hang-off device for a riser is illustrated in Figure 1 , where the hang off device is identified by reference numeral 1 , and the riser is identified by reference numeral 2. As will be clear from the following discussion, the hang-off device is able to provide increased flexibility, which may reduce risk, weight, space needed and ultimately cost.

Referring to Figure 1 , there is provided an exemplary hang-off device 1 , which preferably comprises a ball joint 3. Any other type of long lasting bearing type joint with the ability to take up large offset angles can however be used.

A connector 5 hangs from the ball joint 3 by an arm 9 allowing pivotable movement either freely constrained only by the ball joint, or the movement of the arm might be constrained by constructional features of the joint assembly or an assembly of which the joint is a part. For example, movement might be constrained in a single plain as shown notionally in the figure; movement outside of the plain would allow the hanger to deal with more complex movements of the riser relative to the host facility such as a floater.

Hydrocarbons or fluids/gases are not transferred through the joint. Instead the riser content is transferred through a fluid conduit which is connected to the riser end 4 via a connector 5 hanging from the joint 3. The fluid conduit includes a flexible jumper 6 from the connector 5 and over to a floater stationary connection point 7. The flexible jumper 6 comprises an unbonded and/ or armoured flexible hose. In the case of a disconnectable system the jumper 6 will be from the connector 5 and over to the riser mooring buoy 8. This will allow enough flexibility in the system to take relatively large rotations of the riser without having to have hydrocarbons passing a gasket / bearing assembly and without having to take any stress in the connection / riser hang-off.

The invention has been described with reference to a specific embodiment. Variations will suggest themselves to those skilled in the art without departing from the scope of the inventions as defined by the appended claims.