Subsea Tree Safety Control System Using Surface Extraction
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Solution Overview
Problem
Traditional subsea safety shut-in systems fail to provide a desired probability of failure on demand and lack reliability due to complex subsea electronics and microprocessors, which are prone to failure and difficult to maintain.
Innovation Solution
A subsea test tree system with a surface control station and a subsea control system that uses DC actuation and a diode steering circuit to actuate safety valves, eliminating the need for subsea microprocessors and reducing electronics below the water surface, while providing diagnostic testing and backup power to maintain safety valve functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If traditional subsea safety shut-in systems use microprocessors and complex subsea electronics, then automation and control capability are improved, but reliability deteriorates due to higher probability of failure and difficulty of maintenance
Solution Approach 1:
The patent extracts the microprocessor and complex electronic control system from the subsea environment and relocates it to the surface control station. The subsea control system retains only simple DC actuation circuits and diode steering components, eliminating the reliability issues associated with microprocessors in harsh subsea conditions while preserving automation capability through surface-based control.
Solution Approach 2:
The patent replaces the traditional complex electronic/microprocessor-based control system with a simpler DC electrical actuation system using diode steering circuits. This substitution eliminates vulnerable electronic components from the subsea environment while maintaining the ability to control safety valves through basic electrical circuits that are more reliable in harsh conditions.
2Adaptability or versatility
If subsea control systems include microprocessors and complex electronics, then control functionality is improved, but ease of repair deteriorates due to difficulty of maintaining subsea electronics
Solution Approach 1:
The microprocessor and complex electronic components are extracted from the subsea control system and placed in the surface control station. This allows all complex electronics to be accessed, maintained, and repaired at the surface where standard maintenance procedures apply, while the subsea system retains only ruggedized DC actuation components that require minimal maintenance.
Solution Approach 2:
The control system is segmented into two distinct parts: a surface-based control station containing all complex electronics and microprocessors, and a subsea control system containing only simple DC actuation circuits. This segmentation allows independent maintenance of each component, with the subsea portion requiring minimal intervention.
3Difficulty of detecting and measuring
If subsea control systems use complex electronics and microprocessors, then diagnostic capability is improved, but probability of failure on demand increases
Solution Approach 1:
The diagnostic and control electronics are extracted from the subsea environment and placed in the surface control station. This eliminates the probability of failure associated with subsea microprocessors and complex electronics, while diagnostic capability is maintained through the surface-based system that can monitor and test the subsea safety valve actuation system without being subject to harsh environmental conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration reduces the probability of failure on demand by simplifying the system, allowing for quick maintenance of surface electronics and reducing the likelihood of system failure, thereby ensuring reliable operation and safety.
Implementation Method 1
The subsea control system may include a diode steering circuit to demultiplex an electric current received from the surface control station
Implementation Method 2
The surface control system may utilize DC actuation to actuate the safety valve. The control station may provide an electric current through a conductor in the umbilical to actuate the safety valve via the subsea control system
Data Source
AI summary
An embodiment of a method for limiting the probability of failure on demand of a subsea test tree (“SSTT”) includes the steps of providing a safety shut-in system for actuating a safety valve of the SSTT, the safety shut-in system including a surface control station positioned above a water surface connected via an umbilical to a subsea control system positioned below the water surface to actuate the safety valve; and diagnostically testing the safety shut-in system without actuating the safety valve.