Infrastructure Production Cost – around US$ 5 per barrel! *
Sea Nova is flexible and effective over the full range of water depths in which a typical drilling jack-up might operate.
It typically incorporates a cellular concrete gravity base providing an integral and rigid foundation for four tubular steel un-braced column legs.
The columns in turn support a conventional trussed rectangular topside structure, which supports process equipment, wellheads, control room, helideck, accommodation etc.
The base, columns and topside form an extremely rigid portal frame arrangement eliminating the need for a complex bracing arrangement.
Specifically Sea Nova has the following attributes essential in the current (and future) commercial climate:
For very poor seabed conditions, Sea Nova's foundation system and installation procedure can be adapted to use conventional piles or suction piles depending upon ground conditions. Our geotechnics team can help you assess what foundation will work best on your seabed based on your soils data.
Ocean’s Sea Nova Platform System is a self-installing jack-up structure. It differs from conventional drilling jack-ups in that moment support is provided at both the upper and lower ends of the un-braced column legs, hence the legs are subject to lower stresses. Furthermore, the jacking system is attached during installation only. There are no high fatigue areas such as exist in a conventional jack-up and the locking system is both simple and low-stressed.
Sea Nova can be fully commissioned onshore with only minimal tie-in and pressure testing on location.
As the Sea Nova structure is a simple un-braced 4-legged structure, it has no complicated K-joints or nodes to inspect. The exposed area of steel in the splash zone or beneath Mean Sea Level (MSL) is less than for a similar performance conventional platform hence corrosion and marine growth are less problematic. The column legs are dry to the seabed and thickness checks can be conducted from the inside by platform personnel (i.e. no diving or ROV inspection required). Cleaning marine growth is a relatively easy operation and because of this and the simpler inspection regime, maintenance costs are considerably reduced.
Note the platform stiffness is comparable with a conventional braced structure.
A significant advantage of the design is Sea Nova’s ability to be easily removed and re-used. This obviates high decommissioning provision and is particularly attractive to the sequential development of multiple fields or areas.
The design fully conforms with all relevant codes and standards normally applicable to offshore structures worldwide and Sea Nova will withstand the severe wave regime existing in the North Sea and can, therefore, be located anywhere.
The design features discussed below give Sea Nova the lowest infrastructure cost per barrel of any structure (fixed or floating) of comparable performance!
Ocean’s Sea Nova Platform System is flexible providing a large deck area.
As the Sea Nova Platform design is driven by lateral (environmental) loading, it can carry a very significant payload without increase in the steel member sizes or weight. The topside structure comprises a flat-trussed structure with two or more large pancake decks facilitating maintenance-friendly equipment layouts.
The Sea Nova topside structure is supported by four tubular columns extending from one of the foundation options specified above.
It can accommodate:
■ dry trees,
■ process equipment,
■ power generation,
■ control systems,
■ all associated facilities.
Sea Nova typically incorporates an integrated helideck that can accommodate a large service (S76 or equivalent) helicopter. The design allows helicopter operations to continue during all offshore activities including wireline, coil tubing and workover operations during which a lubricator mast can be erected at any well position.
The helideck can be integral or separate and Sea Nova will support a crane, cantilevered vent or flare or other associated facilities.
A boat landing option is also available and this can be retractable with remote controlled lowering and raising. This was used on our MOD platforms so is a proven alternative.
In its normal (and most economical) configuration Sea Nova is fitted with a concrete gravity base structure (GBS). The GBS typically comprises a rectangular hollow reinforced concrete structure of proven design. It is self-floating and when deballasted its inherent buoyancy is used to aid towage and installation. No specialised vessels or heavy-lift facilities are required during installation hence reducing costs whilst increasing project flexibility.
The base can be fitted with detachable footpads that are tailored to meet a specific site’s characteristics in relation to level, need for skirts etc. The use of these footpads simplifies later removal of the platform at the end of its field life. New footpads can subsequently be fitted to suit a later deployment at a new field with different seabed conditions.
The steel tubular legs are cast into the GBS enclosed inside a circular reinforced concrete sleeve that spans between the upper and lower horizontal slabs of the base itself. In addition to this a large steel collar located above the upper reinforced concrete slab is used to transfer applied loads into the gravity base at relatively low stress levels. A system of ballast pipework is fitted to allow differential ballasting or de-ballasting of the base structure.
We've been there, We've done It!
InfraStructure Production Cost – below US$ 5 per barrel! *
Marginal Oil or Gas Fields need to be developed at the lowest possible cost/barrel consistent with a safe and sustainable operation. Oil and Gas will remain part of our energy future for most if not all of this century but its profitability, certainly in the short term, will be subject to an uncertain selling price and will require the most cost-efficient production system in both Capex and Opex terms.
Sea Nova with Associated Storage will achieve a typical infrastructure production cost of less than around US$ 5 per barrel for fields with:
Sea Nova with Associated Storage competes directly with an FPSO solution at a fraction of its through-life costs. Even basic FPSO solutions have an operating cost in the region of US$ 13 per barrel and may be more expensive due to complex subsea maintenance operations.
* Drilling Costs excluded.
** Larger or smaller production rates can be accommodated. 30,000 bbls/day is used to calculate typical pricing.
The system comprises a subsea pre-stressed, self-installing and re-locatable reinforced concrete Storage Tank positioned directly over the well positions with a Minimum Facilities Platform, Sea Nova, located on top.
The wells may be pre-drilled or post-drilled either by jack-up or by on-platform drilling. In the former case the system can mate with a pre-drilled template.
The Storage Tank comprises a conventionally-shaped structure approximately 48 metres in diameter and 28 metres high. It is installed in advance of the platform unit. It is designed to ensure low seabed loading and provides an “artificial seabed” which can accept the installation of the Sea Nova platform unit on top.
In most cases no seabed preparation is required. In shallow water the storage unit can be deployed alongside the well position and platform deployment location.
The advantages of a concrete storage tank as compare with steel include:
Produced fluid is imported via dry trees located on the platform lower deck. Production conductors run from the drilling slots to pre-installed sleeves in both the platform gravity base and the subsea storage unit.
The produced fluid is processed for export by conventional production equipment located as required on the platform topside. Once stabilised for tanker export it is transferred by the production riser to the subsea storage tank where it displaces seawater ballast to a settling cell within the structure. The settling cell has a long residence time and oily water settles at the top of the cell from where it is drawn off and returned to the platform for further clean-up prior to discharge. Ballast water could be expected to be discharged with contamination levels less than 20 ppm.
The stored produced fluid displaces the ballast water until the cell is fully loaded. At this point it must either be exported by shuttle tanker or production must halt. If the stored fluid is heavy (viscous) it can be heated to maintain temperature with a heating medium being pumped and re-circulated through the storage volume from the platform. Export to shuttle tanker can be achieved through a conventional CALM Buoy or, in certain circumstances, via a reel system on the platform itself.
The FPSO Tanker is eliminated thus removing the most expensive system component in terms of both Capex and Opex costs. No mooring, no manning, no excessive HSE costs, no fuel costs, no expensive maintenance! Relocation costs are similar for both systems though platform and storage reinstatement will be considerably lower than for the FPSO.
Contact us to see how Sea Nova with Associated Storage can provide you with a robust and cost-effective development plan using Ocean's proven technology!
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