Session: 11-07-01 Petroleum Production: Offshore Systems and Subsea Operations

Submission Number: 155240

Study of the Reduction of Vertical Oscillations of a Floating Structure 

Offshore operations for petroleum exploitation are continuously increasing in deep and ultra-deep waters, such as in the pre-salt layers, over two thousand meters of water depths. On the other hand, a strong trend is noted for deep water fields to generate wind energy using floating platforms, in order to respond to the current social demand for sustainable energy. At the same time, there is also a demand for subsea mining of the seabed in deep and ultra-deep oceans due to the scarcity of mineral land sources.

Viable solutions for those deep water operations are needed addressing economic and safety issues, mitigating potential damages to the environment. For this purpose, floating structures that present low motion behavior in the ocean environment is a key element, among others. Efficient and effective solutions for floating systems offering low cost and low downtime in operations are being pursued.

The main objective of this work is a start off investigation to exam the reduction of vertical oscillations (“heave”) of a floating structure, as an initial study of floating platforms with improved motion behavior in waves, by introducing the action of an air chamber confined to the floater´s hull.

A mathematical modeling for the air chamber influence on the floating structure motion is presented and the fundamentals of the dynamic of the motion of the floating structure is studied with the aid of a simplified model geometry. A small physical model was used for experiments conducted in a calm water tank. In order to conduct the analysis of the dynamics, a numerical routine was developed to solve the vertical equation of motion of the structure based on simplified formulations employing Morison equation for wave forces.

As a preliminary result in the study, it is observed that the presence of the air chamber reduces the platform vertical motions. The effect of the air chamber on the natural frequency and amplitude of the vertical platform oscillations could be verified experimentally and theoretically. The results of the numerical simulations were compared with the laboratory experiments, showing that this simple numerical model is a useful computational tool to support practical development of the low heave
floating platform concept.

This study constitutes the first step towards mastering the design and operation of a real platform, with potential to be applied to floating platforms bearing wind turbine towers for power generation installations on high seas, and also to other deep waters operations such as oil and gas production or subsea mining.

Presenting Author: Caio Cesar De Oliveira Trigo University of Campinas

Presenting Author Biography: Graduated in Mechanical Engineering Technology - Design at the Faculty of Technology of São Paulo (FATEC-SP / 2010) and is a Master's Degree Student in Sciences and Petroleum Engineering from the University of Campinas (UNICAMP). Has experience in Naval and Oceanic Engineering and Mechanical Design.