Hybrid Fuzzy-PID Choke Control for Offshore Slug Suppression
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Solution Overview
Problem
Existing anti-slugging controllers for petroleum production systems require subsea measurements, which are difficult and costly to obtain, limiting their applicability and often result in increased wellhead pressure and reduced production efficiency.
Innovation Solution
A hybrid fuzzy-PID control algorithm that uses surface measurements, such as pressure upstream of the choke valve, to stabilize production flow by incorporating heuristic interventions through a fuzzy inference system, effectively suppressing slugging without the need for subsea installations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing anti-slugging controllers are used, then slugging can be suppressed, but subsea measurements are required which are difficult and costly to obtain
Solution Approach 1:
The patent uses surface-measured variables (pressure, temperature, flow rate at the platform) as intermediary parameters to indirectly monitor and control slugging conditions in the subsea flowline, eliminating the need for direct subsea measurements while maintaining control effectiveness
Solution Approach 2:
The patent replaces the need for physical subsea measurement devices with a control system that uses readily available surface measurements and mathematical models to detect and respond to slugging conditions, substituting mechanical measurement infrastructure with computational analysis
2Reliability
If existing anti-slugging controllers are used, then slugging can be suppressed, but wellhead pressure increases and production efficiency decreases
Solution Approach 1:
The patent implements dynamic control of the choke valve opening based on real-time analysis of surface measurements and detected slugging conditions, allowing the system to optimize valve position continuously rather than using fixed static settings, thereby maintaining slugging suppression while maximizing production efficiency
Solution Approach 2:
The patent establishes a closed-loop feedback system where surface measurements are continuously monitored, slugging conditions are detected in real-time, and choke valve positioning is adjusted accordingly, allowing the system to respond dynamically to changing flow conditions and maintain optimal production efficiency while suppressing slugging
Data Source
AI summary
The invention solves the problem of the difficulty of acquiring subsea variables by using a widely available surface variable, namely the pressure upstream of the choke valve. As surface variables have an unfavorable dynamic for use in conventional anti-slug controllers, which are based on the linear PID algorithm, the proposed controller uses a hybrid fuzzy-PID architecture, which compensates for the unfavorable dynamic of the controlled variable by means of heuristic interventions in the control action generated by the PID part of the controller. The heuristic action of the proposed controller allows it to be more robust than a conventional controller, even with a relatively slow control action, which makes it possible to apply the proposed algorithm in systems whose choke valve activation is slow. Thus, the two largest impediments for installation of conventional controllers, lack of subsea measurement and choke valve slowness, do not pose a problem for application of the proposed algorithm. This allows the proposed anti-slug controller to be used in offshore production systems without the need for physical intervention in the subsea or surface facilities.