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The MODEC CP Semi (Central Pontoon Semi-submersible) is a cost-efficient new generation design for deep and ultra deepwater oil and gas production. This low-cost platform is designed to operate in hurricane, cyclonic or mild environments.

The CP Semi is easily scalable for the desired payload and can be used for a stand-alone or a hub facility. It can be used with wet and/or dry trees.

The CP Semi consists of a continuous octagonal central pontoon structure and four radially oriented columns outboard of the pontoon. The radial orientation of the columns enhances the stability of the platform during quayside integration of the topsides while minimizing the displacement needed. Because the pontoon structure is inboard of the columns, the compartmentation requirement is less onerous, which allows the hull steel weight to be substantially reduced.

A box girder system at the top connects the four columns, which in turn support a conventional truss deck. The box girders enhance the fatigue strength at the connections between the column and the deck as well as columns and pontoon.

The MODEC CP Semi design is a result of a continued working relationship between MODEC and WorleyParsons Sea.

Hull Advantages

Optimal displacement/payload ratio:
For the same payload, the CP Semi requires less displacement than conventional production semis.
Optimal mooring design:
For the same payload and environment, the CP Semi requires smaller-sized moorings.
Cost savings:
The CP Semi is less expensive than comparable conventional designs due to efficient displacement/steel weight ratio and optimal mooring. The pontoon structure is inboard of the columns, which makes the compartmentation requirement less onerous, thereby resulting in a substantial reduction of lower hull steel weight.
Optimal stability:
The radial orientation of the columns enhances the stability of the platform during quayside integration of the topsides while minimizing the displacement needed.
High SCR fatigue lives:
The deep draft during operation provides for Steel Catenary Risers (SCR) friendly motions.

Topsides Advantages

Efficient deck structure:
Optimal deck supports minimize deck steel weight.
Efficient design process:
The deck and hull designs can be performed independently of each other resulting in a more efficient design process. This is due to a box girder system employed at the top of the columns which sustains the pry and squeeze loads.
Deck design:
Can be modular or integrated.

Schedule/Construction Advantages

Construction-friendly design:
Maximizes schedule efficiencies.
Payload changes can occur during the project without impacting hull design/topsides design and ultimately, the construction schedule. Talk to us about the unique advantages that the CP Semi design has in this area.
Flat panel fabrication:
Ideal for the shipyard panel line and results in better quality/faster construction schedule.
Conventional truss deck

Installation/Operation Advantages

Topsides can be mated to column tops by lifting or float-over methods.
Inboard or outboard:
SCR's or flexible risers can be supported inboard or outboard of the pontoon structure.
Central moonpool:
Allows for SCR pull-in and CT interface.
Wet trees and/or dry trees:
The CP Semi can be used with either or both.
No seachests:
This eliminates the possibility of inadvertent and uncontrolled flooding.
Constant draft:
The CP Semi constant draft provides sufficient air gap and eliminates the need for de-ballasting to a storm draft.