Abstract

A general four-cylinder semi-submersible platform is considered for optimizing the steady heave motion and mean drift force. The commercial software, HydroStar, is adopted for analyzing the hydrodynamic behavior of the semi-submersible. The optimizations of different types of proposed semi-submersibles are carried out, including the column shape, center column and pontoon shape. According to the optimization mentioned above, the influence of them on heave motion and mean drift force are investigated.

Introduction

Important business strategies on deepwater technology are directed towards the design of floaters to increase the operability window in challenging and harsh environments, including ultra-deep waters. To meet the challenges and increase product line, it is interested to offer a suite of drilling and production semi-submersible designs with enhanced performance by reducing motions, thereby allowing operations with larger uptime window. In this aspect, the heave RAO is quite important parameters. In addition, environmental loads, especially wave drift load, need to be minimized to reduce the cost of riser and mooring systems.

In order to reduce the heave RAO and mean drift force of a semisubmersible hull, a lot of work are carried out recent years. Goncalves et al. (2010) investigated a new concept for a monocolumn floating unit, aimed at exploring and producing oil in ultradeep waters. Hong et al. (2013) analyzed the steady roll motion of a semi-submersible with shallow draft in regular waves. Voogt et al. (2002) demonstrates how the findings of a series of model tests and diffraction calculations, performed to determine the motion behavior of a new semi-submersible design were used to influence the final design. Spahaier et al. (2007) performed a series of tests with a model of a monocolumn platform with a moonpool, with the objective of determining the entrance area at the bottom of the moonpool that minimizes vertical motion in waves. Matsumoto et al. (2008) investigated the influence at vertical first order motions using appendages in a monocolumn platform. Generally, the optimization can be performed in two steps:

  1. critical assessment of existing concepts and technologies used in various complex hull designs, and

  2. development and adaptation of these design concepts and technologies to optimize existing semi-submersible designs for harsh environment.

The latter one is the major target of this paper.

The aim of this paper is the reason of heave RAO and mean drift force according to optimizing the semi-submersible hull. Various types of proposed semi-submersibles are carried out, including the column shape, center column and pontoon shape. According to the optimization mentioned above, the influence of them on heave motion and mean drift force are investigated.

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