Pipeline-Riser Pressure Pre-Alarm for Severe Slugging Control
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Solution Overview
Problem
Existing methods for controlling severe slugging in offshore oil and gas pipelines are ineffective in preventing the formation of harmful flow patterns, relying on valve regulation and PID control, which are sensitive to valve openings and fail to anticipate upstream pressure fluctuations, leading to unstable flow rates and equipment damage.
Innovation Solution
A pre-alarming method using support vector machines trained with seabed and riser pressure difference signals to identify unstable flow patterns, allowing for timely intervention by adjusting valve configurations and gas injection to prevent severe slugging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If valve regulation and PID control are used to control severe slugging, then flow rate stability is improved, but the system is sensitive to valve opening changes and fails to anticipate upstream pressure fluctuations
Solution Approach 1:
The patent applies preliminary action by using upstream pressure fluctuation signals as early indicators to predict severe slugging formation before it occurs. The system monitors pressure fluctuations at the upstream end of the pipeline and uses these signals to trigger preventive control actions, allowing the system to act in advance rather than reacting after the problem develops. This resolves the contradiction by gaining time without sacrificing flow rate stability.
2Reliability
If conventional control methods are applied after severe slugging forms, then flow pattern can be adjusted, but several periods are needed to eliminate the severe slugging
Solution Approach 1:
The patent implements preliminary action by detecting upstream pressure fluctuations that precede severe slugging formation and triggering control actions before the harmful flow pattern fully develops. This early intervention significantly reduces the time required to eliminate severe slugging compared to conventional methods that only react after the flow pattern has already formed and caused problems.
3Measurement precision
If identification methods use valve opening degree as a parameter, then flow pattern identification can be performed, but the identification result becomes sensitive to valve opening changes
Solution Approach 1:
The patent applies the extraction principle by removing the valve opening degree parameter from the flow pattern identification system. Instead of using valve position as an identification parameter, the system extracts and uses upstream pressure fluctuation signals as the primary indicator. This eliminates the sensitivity to valve opening changes while maintaining accurate flow pattern identification, resolving the contradiction between measurement precision and reliability under valve regulation.
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
The method provides accurate and reliable pre-alarming with a low false alarm rate, enabling effective prevention of severe slugging and reducing pipeline and equipment damage by utilizing upstream signals and adjusting valve configurations.
Implementation Method 1
through the coupling relationship of gas-liquid phase distribution (can be represented by the pressure difference of vertical section)
Implementation Method 2
When the opening degree of the valve changes, the throttling coefficient also changes, causing the pressure difference change of the corresponding pipeline section
Implementation Method 3
opening a gas injection valve at the bottom of the riser
Data Source
AI summary
A pre-alarming method, a control method, and a control system for a harmful flow pattern in an oil and gas pipeline-riser system are provided. Support vector machines are trained. Through at least three pressure difference signals on the pipeline-riser system, an overall flow pattern in the pipeline-riser system is continuously and rapidly identified. Depending on monitoring on formation of a long liquid slug in a seabed pipeline and a quick response of the mean value of each pressure difference signal on a flow rate change, pre-alarming for a liquid slug caused by different mechanisms is realized, and liquid slug formation positions respectively of seabed pipeline and riser bottom are correspondingly pre-alarmed; after a pre-alarm is issued, there is enough time for a control device to respond, so as to avoid formation of the harmful flow pattern or damages caused by the harmful flow pattern.