Targeting operator requirements for standardized platform components

SSCI structures deployed in the US Gulf of Mexico.

• Typical and SSCI Development Schedule [73,671 bytes]
• Fig. 1 [33,594 bytes]

Collapsing deliveries, fabrication schedules

As a Gulf Coast fabricator, State Service Co. Inc. of Ingleside, Texas has often answered queries from operators regarding the availability of boatlandings, decks, helidecks and appurtenances related to the development of shallow-water leases, where caissons (braced and unbraced) are typically utilized for field development.

In answering such queries, three issues have become apparent:

• The operator is interested in compressing the time required for delivery.
• Standardization of the components seems lost in the variety of designs issued by a multitude of engineering consultants.
• Except for very small decks and boatlandings, transportation of the components along the Gulf Coast requires the use of expensive boats or barges.

In November of 1996, State Service Co.'s Houston engineering group began to study development of "standardized" caisson deck and helideck components to better serve clientele. Gulf of Mexico operators required immediate response to requirements for offshore wellhead decks, helidecks, and boatlandings in an effort to minimize completion-to-startup lag time. International operators required wellhead decks and related components which may be easily transported via conventional shipping methods. The challenges were many:

• Immediate response must be accomplished without operators incurring the additional dryhole cost exposure of engineering and fabrication expenditures prior to drilling. This necessitates prefabrication and stocking of components by the fabricator.
• Components must be standardized to a point of being interchangeable between structures, and must not require on-site technical assistance for assembly overseas.
• The distribution of components must resemble commodity items essential to lease development such as wellheads, valves, chokes, control panels, etc.
• Components must be standardized for ease of fabrication, maintaining sufficient versatility in design to be readily adapted to accommodate individual installation and operational parameters.

Design parameters

The required components include the following:

• Deck: Large enough to accommodate 1-3 wells, along with navigational aid equipment, PLC equipment, wellhead control panels, methanol storage, and operational tools.
• Helideck: With loading capacity and size as required to accommodate operations of a Bell 206L or Bocal BO-105CBS aircraft.
• Wellhead access deck: To aid in personnel access to high-pressure wellheads.
• Davit crane: Capable of lifting tools and chemicals from the water level.
• Aids to navigation: As required by MMS guidelines.
• Caged ladder: For access from the boatlanding level.
• Boatlanding: 180 degrees or 360 degrees, integrating a riser guard as required.

The physical design limitations of the components include:

• All components must be fully truckable.
• Component sizes must be suitable for "packaging" for overseas shipment.
• Assembly must be possible utilizing minimal crane capacity.
• Installation must be possible utilizing minimal crane capacities of standard liftboats.
• Decks must be suitable for installation on caissons from 36-in. diameter to 60-in. diameter.

Other considerations include:

• Design and fabrication must meet industry standards such as API RP2A, AISC, and AWS D1.1 guidelines.
• Fabrication specifications, including material and coating requirements, must meet or exceed common industry specifications.

Design evolution

Since original designs were completed and structures fabricated in the spring of 1997, the components' designs have evolved to incorporate various requirements of operator preference, installation parameters, and fabrication considerations, which have been discovered through fabrication and application of the structures in multiple operating scenarios.

Phase I

SSCI's original design included a deck with dimensions of 20 ft by 20 ft (SSCI's Model 2020), and a 24 ft by 24 ft helideck. A subsequent project requirement for additional deck space dictated by the addition of a future well slot, and a requirement for a larger helideck landing area necessitated expansion of the Model 2020 to 20 ft by 27 ft, SSCI's Model 2027, and expansion of the Model 2424 Helideck to 27 ft by 27 ft.

Operator preference dictated the evolution of a 360 degree boatlanding from the original 180 degree model, and installation of the deck/helideck structure on several high-pressure wellheads necessitated the incorporation of an optional wellhead access deck.

Installed between the helideck legs or on its own supports in the absence of a helideck, the wellhead access deck has proven to be a very cost-effective method of increasing operator access while adding nearly 30% to the usable deck space.

The deck support substructure of the Model 2020 and Model 2027 is identical, allowing the Model 2020 deck to be outfitted for future offshore expansion to 20 ft by 27 ft for a small incremental cost.

Phase II

The natural progression of the design increased available deck space to accommodate requirements (present or future) for production equipment and/or additional wells. This design progression resulted in several additional deck designs: (1) SSCI's Model 3035A, a 30 ft by 35 ft deck with grating covering, (2) SSCI's Model 3035T, a 30 ft by 35 ft deck which incorporates a plated, curbed, and drained equipment module on one outboard side of the otherwise grated deck area, typically housing a test separator, fuel/instrument gas system, and sump, and (3) SSCI's Model 3035P, a 30 ft by 35 ft deck which incorporates plated, curbed, and drained equipment modules on each side of the otherwise grated deck area.

These equipment modules may be utilized for installation of separators, fuel/instrument gas equipment, vertical sump tanks, water skimmers, vent scrubbers, or line heaters as the project dictates.

The design of the Model 3035 Deck Series allows for initial installation of a Model 3035A deck (no production equipment), while offering simple offshore modification to the production mode through the exchange of "bare" deck modules for those equipped with production equipment.

SSCI has continued its standardization process by generating detailed vessel trim and interconnecting piping drawings for common flowrate scenarios. This advanced degree of deck and equipment design allow delivery of the larger, outfitted decks to be placed on a fast-track delivery schedule.

Before, after drilling

Prior to drilling, the operator anticipates a future structure requirement based on a drilling schedule and development options. At this point, State Service provides cost and delivery options based upon anticipated project-specific requirements. Upon receipt of operator's commitment to utilize a company structure after successful completion of a well, SSCI completes and issues drawings for use in the operator's structural permit application, and directs fabrication personnel regarding any modifications required and anticipated delivery schedule.

If the drilling is unsuccessful, the operator has no financial obligation to State Service. Upon receipt of a purchase order, State Service prepares the structure(s) for shipment and issues the AFC detailed drawing package in accordance with project requirements. Upon receipt of shipping instructions, State Service coordinates the trucks and construction crew to provide transportation and personnel required to assemble structures dockside, at the operator's shorebase of choice.

For structures ordered from inventory, mobilization, shipment, and assembly of the structure requires three days notice. Nav-aids are installed after assembly at the shipping point. Shipping on short notice required allows the operator to finalize arrangements for installation prior to shipment, thereby minimizing overall mobilization costs.

To date, State Service has fabricated 14 Model 2020 deck packages, three Model 2027 deck packages, and three Model 3035 deck packages. In addition, boatlandings, davit cranes, and helidecks have been incorporated on other projects as stand-alone components, and helidecks have been leased for use during construction periods.

With an emphasis on deliverability, the decks have become known in some industry circles as the "FedExDeck", for "the order of today - deliver tomorrow" capability.

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