Integrated subsea production system: An overview on energy distribution and remote control

Abstract

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.