On the Shared-Actuation Control for the Operation of Manifolds in Subsea Production Systems

This article presents a set of analysis and results on Shared-Actuation Control (SAC) techniques, intended for the remote control of valves in subsea manifolds. The discussion covers historical aspects, including presentation of real cases of SAC in Brazilian fields of Petrobras, as well as covers a conceptualization for the technique. The formulated concepts are used indeed to derive a methodology, intended to guide the development of SAC schemes, during engineering projects of subsea manifolds. The discussion is based in part on the unique experience accumulated by Petrobras in the last 20 years, with the development and introduction of a SAC-based subsea manifold in Campos Basin, Brazil, and the latest development efforts ongoing by 2019 for a new generation of SAC, for the application in subsea manifolds to be installed in ultra-deep waters of Pre-Salt fields, in Santos Basin, Brazil. The methodology proposed in this article is based on a comparative approach which aims to incorporate, on design of SAC, the best engineering practices and lessons learned from traditional Electric-Hydraulic Multiplexed Control Systems (EHMCSs). We refer to such approach as the Inheritance & Counterbalance (I&C) Methodology, since it is based on the application of two specific principles, namely, the Inheritance and Counterbalance Principles. The principles are proposed in this article as well. Taking as starting point a set of technical characteristics of EHMCSs, such as employment of redundant subsea electronics and methods of subsea installation, a subsea engineer can apply the I&C Principles to determine if SAC should inherit a given EHMCS characteristic or, if inheritance is not feasible for some reason, adopt alternative requisites on SAC, in order to counterbalance the effects of such no inheritance. The conceptualization of the I&C Methodology allow us effectively applying it, to obtain as result a table of engineering requisites, suitable for SAC schemes destined to subsea manifolds. The proposed table is presented in this article and incorporates several engineering aspects, which are arbitrated from the knowledge on previous applications of Petrobras in subsea control systems. Such applications include both SAC schemes and EHMCSs, featured on fields of Campos and Santos Basins.