Subsea Compact Separation: Control System Design

摘要

This paper summarizes key results of the development and verification for a subsea compact separationcontrol system based upon a literature review, control system design, dynamic simulations, and anintegrated system test. The compact separation system being considered is designed for applications inwater depths up to 3,000m. The control system is a key technology element of the compact separationsystem, and its satisfactory performance is critical to ensure stable operation of the overall system. Athorough literature review was conducted to evaluate the control system designs for comparable subseaseparation systems in industry, to understand the technical challenges, and to incorporate the key learningsinto the development of this control system design.From this work, best practices were identified and were used as guidelines. A preliminary controlsystem was developed, and the robustness of its design was assessed through dynamic simulations. Later,an integrated system test was performed with real crude and methane at realistic operating conditions toevaluate the performance of the compact separation equipment and to validate the model of the controlsystem. The dynamic simulations and integrated system test results demonstrated the control systemresponse following transient events, such as slugging, and provided insight into the system dynamics thatthen led to further modifications of the control system design and enhanced the overall system performance.This paper also delineates challenges associated with the design of a control system for a subseacompact separation system consisting of multiple, closely integrated gas-liquid and oil-water separationunits. For example, the relatively small control volumes in compact separation equipment and theinteraction between the different components can both add complexity to the control system design.Lessons learned from the modeling and implementation of such a sophisticated control system arediscussed with the intent to serve as a reference for future subsea separation projects in the oil and gasindustry.