Tension Leg Platform With Improved Hydrodynamic Performance

Abstract

A tension leg platform that is stable with a quayside-integrated deck without the use of temporary stability modules or specialized installation techniques. The hull preferably consists of four radially-oriented vertical corner columns connected with four central ring pontoon segments. The vertical columns are fixed to the outer periphery of the central pontoon. The columns are characterized by a major radial axis and a minor transverse axis. The mooring system includes tendons supported at tendon porches directly at the four column outboard lower corners, without additional radially-extending tendon support structures.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]This invention relates generally to tension leg platforms, such as for offshore oil and gas drilling and production, and more particularly to a tension leg platform that has ample inherent stability so as to allow for quayside integration of the superstructure, towing of the integrated hull and topsides to the installation site, and installation, all without the use of temporary stability modules or other specialized equipment.[0003]2. Background Art[0004]In the offshore oil and gas industry, floating vessels such as tension leg platforms (TLPs) for drilling and / or production are common. A TLP is a type of floating platform that is used for drilling and production in relatively deep water. A typical TLP hull configuration consists of one, three, or four vertical columns, and three or four pontoons, which connect the columns below the water surface. The columns and pontoons are typically rectangular or cylindrical in cro...

AI Technical Summary

Benefits of technology

[0020]A primary object of the invention is to provide a tension leg platform for use in offshore applications, such as for offshore oil and gas drilling and production, having a hull with a plurality of columns and a central pontoon structure that is disposed inboard of the columns, which simplifies construction, reduces support spans and cantilevers, and provides improved hydrodynamic performance of the platform.

[0021]It is another object of the invention to provide a tension leg platform having a hull with radially oriented rectangular columns and a central pontoon structure disposed inboard of the columns which are formed substantially of flat plate construction, thus simplifying the construction of the structure.

[0022]Another object of the invention is to provide a tension leg platform having vertical columns of rectangular cross section that have major axis oriented radially outward from the center of the hull, which provide support for the deck and reduces the support spans and cantilevers of the deck structure required for deck support in conventional TLPs.

[0023]Another object of the invention is to provide a tension leg platform having a unitized central pontoon structure located inboard of the vertical columns that may have a central moonpool opening or may be completely enclosed, which improves the hydrodynamic performance of the platform as compared to conventional ring pontoon, is simpler construction, lighter in weight, and facilitates the support of steel catenary and flexible risers.

[0027]Risers can be supported on the inboard or outboard side of the pontoon and extended to the deck. The central pontoon and outboard column structure simplifies construction, reduces support spans and cantilevers, and provides improved hydrodynamic performance of the platform.

Problems solved by technology

As a result, dynamic amplification of vertical motion is nearly non-existent and the platform has limited heave, roll and pitch motions.

Depending on its configuration, the stability of a TLP (conventional or extended) may be inadequate during installation.

When a TLP is ballasted between the initial free floating draft (e.g. the wet-tow draft or float-off draft) and the lock-off draft (the draft at which securing the TLP to the tendons is initiated), there is a range of drafts at which the TLP stability is critical—the TLP may be unstable or only marginally stable prior to being locked-off to the tendons and de-ballasted.

Most prior art installation techniques rely on using costly specialized installation equipment.

Offshore installation of the deck is an expensive and high risk operation, because it typically requires the use of heavy-lift vessels or float-over deck installation techniques.

Moreover, it requires a relatively long window of good weather.

However, only a very limited number of vessels exist worldwide which are capable of providing the required hook load for a TLP of ordinary size.

Images