First Full-Electric Shared-Actuation Control for Subsea Manifolds in Brazilian Ultra-Deep Waters: A Discussion of the Technological Development up to Field Commissioning

In projects to develop offshore production in Brazilian pre-salt fields, an innovative model of subsea manifolds is being used, based on shared-actuation control (SAC) for the remote operation of valves. The control solution, which comprises the first full-electric robotic tool designed to operate in ultra-deep waters, has achieved an important mark in 2020, with the commissioning and start-of-operation of the first fabricated unit. In this article, we present lessons learned and discuss relevant specifications and programs of the technological development that contributed for the results obtained so far. Considering aspects on conception, technology, and environment of application, the pre-salt SAC required the adoption of new solutions on several disciplines of subsea engineering. As a typical case of technological development, the design process comprised decisions on engineering requirements and the establishment of a comprehensive qualification program. Now, after the first robot completing critical stages at field, such as subsea deployment, functional testing, and integration with the subsea system, we obtain a set of performance results that serve us to evaluate e.g. how effective were the selected technical specifications and testing routines, used throughout the engineering program. This discussion also provides possible adjustments in the overall development plan, considering its application as new generations of SAC arise. The commissioning in 2020 of the first robot resulted in its full integration with the subsea manifold and the correspondent production system, contributing to water-alternating-gas injection in the pre-salt field Tupi Extremo Sul. A second subsea system featuring the same model of robotic tool, for manifold control, is in advanced schedule in 2021 for integration in Búzios II, another pre-salt field in Brazil. Confirming the advantages that we could expect with the adoption of SAC in subsea equipment, the pre-salt SAC allowed a series of optimizations on design of the robot-controlled manifold. The robot tool replaced all the hydraulic actuators that traditional control systems, based on electric-hydraulic multiplexing, would require to implement remote controlling of the manifold valves. This led to a significant reduction on sizes and weight of the manifold structure.