The purpose of this paper is the study of fuzzy control applied to a Dynamic Positioning System (DPS) of semi-submersible platforms. A numerical simulator program in time domain was coded using mathematical models of the floating platform dynamics and the external forces (wind, current, wave and thruster) that act on the platform. Subsequently, a fuzzy controller applied to DPS was developed. The Fuzzy controller and the Proportional-Integral-Derivative (PID) controller were then subjected to the same environmental conditions in order to compare their performance

In 2012, Brasil had a proved reserve of 15.3 billions of BOE (barrel of oil equivalent). The offshore reserve corresponds to more 94% of this amount. Petrobras, the Brasilian E&P company, leads the offshore production in ultra-deep water (deeper than 1500 m of water depth) worldwide. The current offshore production in ultra-deep waters deploys a Floating Production Unit (FPU), and some subsea equipments, such as, wet Christmas trees, manifolds, separation & booster systems, risers and pipelines. However, on board of the FPU, there are several other systems, namely, power generators, separators, gas treatment system, water treatment system, artificial lift system, injection system, etc. A future paradigm shift in the offshore petroleum production shall be the installation of all necessary systems on the sea floor. This article addresses to two challenges that raise with this new integrated operations with subsea oilfield production: the “remote operation and monitoring”, and the “power generation and distribution”. Remote operation and monitoring come from the need to transfer the process operators to shore and optimize the number of operators, to improve the processes availability by reducing the operator response time to a specific task, to provide continuous and predictive monitoring of vital processes, among other factors. Within the context of integrated operations, a remote operating center provides a broad and integrated overview of several processes in the asset, by using modern supervisory software (3D and 4D), database, remote sensoring, among others technologies. Part of this article also provides a comparative discussion between some technologies used in the implementation of remote operation and monitoring. Due to the substantial amount of electrical power required by subsea process units and their relatively long life cycle, typical aspects related to power generation and distribution have been changing. Alternatives, which were not cost effective before, are considered as new trends in the development of new process units due to political aspects and advances in the technology involved. Subsea high-voltage power distribution systems have become an alternative to supply the total load of subsea process units. According to this approach, electrical power distribution is located near the load center, as on shore installations. Normally, such installations are supplied from shore through long power umbilicals, as the supply of individual loads is not economically interesting. The advances in the use of renewable sources have also promoted new alternatives in power generation. These approaches become more interesting due to the possibility of installing large power generation plants using renewable sources on shallow water and transmitting the power to a set of subsea process units. Thus, new alternatives arise, such as the possibility of power transmission in high voltage direct current systems (HVDC), avoiding common problems faced in power transfer capacity using high voltage alternate current systems (HVAC), as large amount of reactive power needed to compensate cable's capacitance. This paper discusses these issues aroused due to power supply of subsea process units.

An experiment using a 1/70 reduced scale model of a Free Standing Riser (FSR) was carried in the Deep-Sea Basin of the National Maritime Research Institute in Japan. For instance, the model’s vertical pipe was about 32m long and the jumper was about 8m long. The FSR model had several measurement stations attached along the vertical pipe, subsurface buoy and jumper; and the motion of each station was measured in 3D by the Visual Measurement System. During the experiment, the effects of the jumper’s top end oscillation on the whole system were investigated. In this case, the top oscillation had propagated along the jumper; however the top oscillation had a reduced effect on the dynamics of the subsurface buoy and vertical pipe. In another experimental case, a current was generated in order to investigate the Vortex Induced Motion (VIM) on the FSR’s Subsurface Buoy. The VIM experiment was repeated for two different buoy models (a smooth cylinder and a cylinder with 3-start heli-coidally strakes) and the results were compared. In this article, some of the experimental results are presented and discussed.

The present study deals with the dynamics of a semi-submersible platform coupled with a free-hanging vertical rigid riser during the re-entry operation in ultra-deep water. The reentry operation occurs after the drilling phases are accomplished which only use the bare drillstring. The re-entry operation entails positioning the subsurface Blow-Out-Preventer (BOP) above the wellhead and installing it to the wellhead. During this operation, the BOP is suspended by the drilling riser. The placement and installation is time consuming and requires a great amount of accuracy. One challenge is the effects of platform motions on the installation procedure. The present work was carried out with the aim to understand the influence of platform motions during the re-entry operation in ultra-deep waters. Another benefit of this study is the knowledge of the effect of platform motions on the drilling riser and BOP which leads to the possibility of drilling more than one well without the need to raise the BOP to the surface. This could greatly reduce the amount of time needed to drill subsurface wells which in turn, reduces overall operational costs. A numerical simulation in time domain has been carried out using a non-linear model for the platform dynamics. The dynamics of a free hanging drilling riser and a dynamic positioning system (DPS) of the semi-submersible platform are included in the numerical model. Simulation results in time domain of the platform displacements with DPS and riser displacement are shown. A discussion of riser displacement and DPS control is also included.