Installation method of an offshore upended float-over platform

Abstract

 The invention relates to a method for transporting and installing a floating offshore base (1) consisting of a multi-columned floater (2) supporting a platform (3) above water. The floater (2) is transported horizontally to the site and upended. The platform (3) is transported to the site on a barge or any other vessel and installed onto the floater (2) by means of a float-over operation in between the columns (4) of the floater.

Description

Background of the invention

[0001] There is an increasing demand for oil and gas production from offshore deep water sites. These sites encounter high winds and waves, which can result in unacceptable heaving, pitching and rolling of the offshore structure, for the production of oil in deep waters. Besides this, with the installation of an offshore platform difficulty arises with the installation of the deck. Float-over (floating the deck over a support structure) has not been possible offshore in wave heights of 1m and higher due to the large forces created by the relative motions between deck and support structure. Present spar designs with one or multi-column are difficult to transport and float-over is based on floating around the support structure.

[0002] The purpose of this invention is to create an offshore base with good motion response in high waves and strong winds. Which can be installed at an offshore location in 2 to 3 meters significant wave height by float over in between the legs. This way the down time risk for the installation will be acceptable for all offshore oil fields.

Description of the invention

[0003] The invention relates to an offshore base with a floating support structure, consisting of multiple slender legs, on which a platform can be placed. The vertical legs, called columns, carry the platform by buoyancy. The long columns produce very acceptable motions of the platform even in strong winds and high waves.

[0004] The support structure, or floater, can be divided into two or more parts, which can be transported horizontally, so that mobilization is easy. It can be placed in vertical position at the offshore site by consecutive flooding of ballast tanks. This is called upending.

[0005] The deck, preferably with fully completed facilities, is floated over between the columns that are so wide apart that a barge or deck fits in between the vertical columns, limiting the work offshore to an absolute minimum.

[0006] Dedicated tanks are available in the columns that can be emptied in a matter of seconds by compressed air to prevent hammering during the initial contact phase and the lift off phase.

Description of the drawings

[0007] 

Figure 1 shows a perspective view of an offshore base (1), which consist of a floater (2) and topside (3). The floater (2) consists of two or more columns (4). The columns (4) are positioned such that a vessel or barge can be floated in between the columns (4) to install the topside (3). The columns (4) are connected by horizontal members (5), called bracings.

Figure 2 shows a four -columned configuration.

Figure 3 shows a float-over operation by means of a vessel (6). Once the floater (2) is upended, the topside (3) is floated in between the columns (4) on a vessel (6).

Claims

1. A floating offshore structure that consist of multiple columns whereby the floater is upended offshore and the topside is installed with a float-over operation in between the columns.

2. A platform according to claim 1 whereby the floater is transported in a horizontal manner and upended by ballasting.

3. A platform according to claim 1 whereby the topside is positioned and lowered onto the floater by means of any type of vessel.

Drawing