Field of the Invention This invention relates generally to floating offloading and storage facilities for subsea hydrocarbon products, and more particularly to such offloading and storage facilities utilizing an offloading mooring buoy.

Descrintion of the Prior Art Offloading mooring buoys for shuttle tankers or other vessels have been used with floating production storage and offloading facilities, such as permanently moored storage tankers. Normally, the storage and offloading facility is connected directly to subsea product lines and receives product from subsea wells. In some locations, dependent on the various water depths and distances, an offloading mooring buoy may be located one thousand (1,000) to fifteen hundred (1,500) meters from a permanent floating storage facility. Shuttle tankers connect to the offloading mooring buoy to receive product therefrom for transport Product flowlines or risers normally extend from the subsea wells to the permanent floating storage facility, and from the storage facility to the mooring buoy for connection to the shuttle tanker for transport. In the past, such product flowlines from the storage facility to the offloading mooring buoy, particularly where the offloading mooring buoy has been spaced a substantial distance from the storage facility, have comprised metal pipes with intermediate floatation devices located along the lengths of the product flowlines to provide a suitable contour or configuration to the flowlines to avoid excessive loads resulting from the weight of the flowlines and the relative motions of the offloading mooring buoy and the floating storage facility. The installation of such metal pipe on the offloading mooring buoy requires the lifting of large loads because of the weight of the pipe. Furthermore, it has been difficult to tow the pipe to the mooring buoy from the permanent storage facility because of the weight of the pipe and the substantial distances required for towing, such as fifteen hundred (1,500) meters.

Identification of Obiects of the Invention It is an object of the present invention to provide an improved installation system for the attachment of product flowlines between two floating facilities separated by a substantial distance over about five hundred (500) meters, for example.

A further object of the invention is to provide such an installation system for a floating storage facility utilizing a pipeline manifold connected to the flowlines from the storage facility and transported to an offloading mooring buoy for connection to the offloading mooring buoy.

SUMMARY OF THE INVENTION A pipeline manifold with empty water tight compartments is connected to the free ends of flowlines at the permanent storage facility and is then towed to a catenary anchor leg mooring (CALM) buoy for product offloading. The pipeline manifold is connected while at sea level to the bottom of the CALM by suitable flexible members, such as anchor chains.

The manifold compartments are then flooded to sink the manifold and associated flowlines to a desired predetermined water depth beneath the mooring buoy. In this position, flexible connecting product flowlines are mounted between the pipeline manifold and the CALM buoy for product flow to the CALM buoy from the permanent storage facility. The flexible connecting flowlines permit pitching or rolling motions of the mooring buoy while obviating excessive stress in the metal pipes or flowlines between the permanent storage facility and the CALM buoy.

Other features, objects, and advantages of the invention will be more apparent after reference to the following drawings and specification.

BRIEF DESCRIPTION OF THE DRAWINGS The objects, advantages and features of the invention will become more apparent by reference to the drawings which are appended hereto and wherein an illustrative embodiment of the invention is shown, of which: Figure 1 is a side elevational, partly schematic, view of a submerged pipeline and manifold (SPLEM) connected to the bottom of an offloading mooring buoy, such as a CALM buoy, with a plurality of connecting flowlines extending from the pipeline manifold to the mooring buoy; Figure 2 is an end elevational view of the arrangement shown in Figure 1 which shows a plurality of connected flexible hose sections forming the flexible connecting product flowlines between the pipeline manifold and the offloading mooring buoy; Figure 3 is a top plan schematic view of the arrangement shown in Figures 1 and 2 illustrating the pipeline manifold connected to the offloading mooring buoy; and Figures 4-6 are views similar to respective Figures 1-3 but showing modified flexible risers or pipes forming the connecting product flowlines between the pipeline manifold and the offloading mooring buoy.

DESCRIPTION OF THE INVENTION Embodiment of Figures 1-3 Referring to the embodiment of Figures 1-3, a catenary anchor leg mooring (CALM) buoy is shown generally at 10 floating on the sea surface 12 and having a plurality of anchor legs 14 extending in a catenary to the sea floor and anchored thereto. Suitable product lines 16 extend from the top of buoy 10 and are adapted for connection to a product transport vessel (not shown), such as a shuttle tanker, to supply product thereto.

A submerged pipeline end manifold (SPLEM) is shown generally at 20 and has a plurality of steel product flowlines 22 connected thereto which extend from a permanent production storage facility, such as a permanently anchored storage vessel or tanker shown schematically at 23 in Figure 3. Such storage facility may be a bottom supported facility rather than a vessel. Suitable valves and manifolds 25 for product flowlines 22 are provided to control the product flow to mooring buoy 10 and to permit recirculation back to the permanent storage facility 23 for purging flowlines 22, as may be required. Manifold 20 has a plurality of water tight compartments 24 therein which may be flooded with or emptied of water as desired for positioning manifold 20 at a predetermined water depth. A plurality of support chains 26 are coupled between support manifold 20 and the bottom of mooring buoy 10.

To connect product flowlines 22 to mooring buoy 10 from a manifold 20 for the supply of product to supply product lines 16, flexible connecting product flowlines generally indicated at 30 are provided. Each connecting flowline 30 is formed of a plurality of flexible hose sections 32 of a predetermined length and selectively coupled to each other. While only one manifold 20 is shown in Figure 3, two or more similar additional manifolds 20 may be provided as desired.

Installation of Product Flowlines For installing product flowlines from permanent storage facility 23 to offloading mooring buoy 10 which may be separated from each other a distance one thousand (1,000) to fifteen hundred (1,500) meters, product flowlines 22 which are normally formed of steel pipe are connected to pipeline manifold 20 at permanent storage facility 23 and are then towed to catenary anchor leg mooring buoy 10. Manifold support chains 26 are then connected from manifold 20 to the bottom of buoy 10 at sea level. Next, water tight compartments 24 in manifold 20 are flooded with a predetermined amount of water to sink manifold 20 to a desired water depth beneath buoy 10. In this position, connecting flowlines 30 are mounted between manifold 20 and CALM buoy 10 to provide a product flow path to buoy 10 from permanent storage facility 23.

Flexible connecting flowlines 30 using flexible hose sections 32 may be connected to each other by flexible connecting joints, if desired, to provide substantial flexibility between pipeline manifold (SPLEM) 20 and offloading mooring buoy 10, thereby minimizing any undesired stresses transmitted to pipeline manifold 20 which result from differential motions of offloading mooring buoy 10 or permanent storage facility 23 with respect to the SPLEM 20.

Embodiment Shown in Figures 4-6 The embodiment of the invention shown in Figures 4-6 is substantially identical to the embodiment shown in Figures 1-3 except for the connecting flowlines 30A shown in Figures 4-6 extending between pipeline manifold 20 and mooring buoy 10. Connecting product flowlines 30A comprise flexible metal risers which provide sufficient flexibility between buoy 10 and manifold 20 to minimize undesired stresses between buoy 10 and product manifold 20. The reference numbers embodiment of Figures 4-6 for similar parts are identical to the reference numbers shown in the embodiment of Figures 1-3.

While the present invention has been illustrated for installing product flowlines between a permanent product storage facility and an offloading mooring buoy, the installation method can be used for the attachment of product flowlines between two floating facilities or vessels separated by a substantial distance of about five hundred (500) meters, for example, such as monohulls, tension leg platforms, or semi-submersibles.