Subsea Multiphase Separator Interface Control
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Solution Overview
Problem
Existing control systems for subsea separation systems face challenges such as data communication delays, limited response times, and performance issues due to the use of subsea sensors and actuators, which complicates stable operation under transient conditions like flow rate fluctuations and slugging.
Innovation Solution
A multiphase separation system with adjustable speed oil and water pumps and control valves is implemented to regulate the interface level between oil and water phases in a liquid-liquid separator, using a control loop that can be tuned to critically damped or overdamped conditions to improve response times and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If subsea sensors and actuators are used in the control system, then the system can operate in deep water environments, but data communication delays and limited response times occur
Solution Approach 1:
The control system is segmented into multiple independent controllers distributed across different separation devices. Each controller operates locally with its own sensors and actuators, eliminating the need for continuous data communication with a central topside control system. This segmentation resolves the time delay issue while maintaining deep water operation capability.
Solution Approach 2:
Controllers are pre-configured with control algorithms and parameters before deployment. The system performs preliminary tuning of control loops during commissioning, storing optimized control strategies that enable rapid response without requiring real-time communication delays. This preliminary action prepares the system to operate autonomously in deep water environments.
2Productivity
If multiple separation devices are used in series for subsea separation, then separation performance is improved, but control complexity increases due to interactions between devices
Solution Approach 1:
The control system is divided into independent control modules for each separation device. Each module manages its own separation process without requiring complex coordination with other devices. This segmentation maintains high separation performance while significantly reducing control system complexity.
Solution Approach 2:
Each separation device is equipped with its own controller that autonomously manages its operation based on local sensor feedback. The controllers self-regulate flow rates, pressure, and separation parameters without external intervention. This self-service approach eliminates the need for complex inter-device control coordination while maintaining optimal separation performance.
3Ease of operation
If fixed speed pumps are used in the liquid-liquid separator, then the system is simpler to operate, but the interface level between oil and water phases cannot be effectively regulated
Solution Approach 1:
The system transitions from fixed speed pumps to variable speed drives that can dynamically adjust pump speeds based on real-time interface level measurements. This dynamic control enables effective regulation of the oil-water interface while maintaining relatively simple operation through automated control algorithms.
Solution Approach 2:
Interface level sensors provide continuous feedback to the variable speed pump controllers. The controllers automatically adjust pump speeds based on this feedback to maintain the desired interface level. This feedback mechanism ensures reliable interface regulation while keeping the system easy to operate through automation.
Data Source
AI summary
The present techniques are directed to a multiphase separation system. The system includes a liquid-liquid separator configured to receive a separated liquid that is further separated into a separated oil and a separated water within the liquid-liquid separator. An oil pump and a water pump, both with adjustable speeds, are configured to pump the separated oil and the separated water, respectively, from the liquid-liquid separator. An interface level in the liquid-liquid separator is regulated by adjusting the speed of the oil pump and the speed of the water pump.