Separator Train Demulsifier Control for Dehydrator Inlet Water
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Solution Overview
Problem
Accurately determining demulsifier dosage in Gas-Oil-Separation Plants (GOSP) is challenging due to variations in production, temperature, and oil properties, leading to either demulsifier waste or off-spec production if not optimized.
Innovation Solution
Implementing a real-time, field-based control method that analyzes the response of separator trains to incremental demulsifier dosage changes, using a water separation profile (WSP) modeled with a 4-parameter logistic function to adjust demulsifier flow rates based on current process conditions, thereby optimizing water separation without historical data reliance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If demulsifier dosage is increased to ensure water separation, then water separation efficiency is improved, but demulsifier waste increases
Solution Approach 1:
The system implements real-time feedback control by continuously monitoring water concentration at dehydrator inlets and adjusting demulsifier injection rates accordingly. The water separation profile (WSP) model uses current process data to determine optimal dosage, creating a closed-loop control system that prevents both over-dosing and under-dosing, thereby eliminating demulsifier waste while maintaining reliable water separation.
Solution Approach 2:
The demulsifier injection rate is made dynamic rather than static. The system automatically adjusts the injection rate based on real-time process conditions and the WSP model, allowing the dosage to adapt to changing production rates, temperatures, and oil properties. This dynamic adjustment ensures optimal water separation efficiency while minimizing demulsifier consumption under varying operating conditions.
2Loss of substance
If demulsifier dosage is decreased to reduce waste, then demulsifier utilization is improved, but off-spec production occurs
Solution Approach 1:
Real-time feedback from water concentration measurements ensures that demulsifier dosage never falls below the level required for specification compliance. The control system continuously compares actual water separation performance against target values and adjusts dosage accordingly, preventing off-spec production while optimizing demulsifier utilization by avoiding excessive dosing.
Solution Approach 2:
The system changes the operating parameter (demulsifier dosage) based on actual process conditions and WSP model predictions. By dynamically adjusting the dosage parameter to match the minimum required for specification compliance under current conditions, the system optimizes demulsifier utilization while ensuring production always meets specifications.
3Loss of substance
If real-time control is implemented to optimize demulsifier dosage, then demulsifier utilization is improved, but system complexity increases
Solution Approach 1:
The system performs self-adjustment using the WSP model and real-time water concentration data without requiring complex external control infrastructure. The WSP model contains pre-determined relationships between water separation performance and demulsifier dosage, allowing the system to self-optimize demulsifier utilization based on current conditions, reducing the need for complex control algorithms and external intervention.
Solution Approach 2:
The water separation profile (WSP) model is developed in advance through incremental concentration tests and fitted with a 4-parameter logistic function. This preliminary modeling work captures the demulsifier's chemical behavior and inertia characteristics, allowing the real-time control system to simply query pre-computed optimal dosages rather than performing complex real-time calculations, thereby reducing control system complexity.
4Measurement precision
If incremental concentration tests are conducted to develop WSP, then measurement precision is improved, but production time is lost
Solution Approach 1:
The incremental concentration tests and WSP development are performed as preliminary actions during plant commissioning or demulsifier changeover events. Once the WSP model is established with high measurement precision from these initial tests, it can be used for years of optimized operation without repeating the time-consuming tests, amortizing the initial time investment over long-term benefits.
Solution Approach 2:
The incremental concentration tests are conducted periodically rather than continuously - typically when demulsifier batches are changed or significant process modifications occur. This periodic recalibration maintains measurement precision without requiring continuous production interruptions, balancing the need for accurate WSP data with the need to maintain production.
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 approach stabilizes water concentration at dehydrator inlets, minimizes dehydrator load, and optimizes demulsifier utilization by automatically adjusting demulsifier injection rates according to real-time process data, reducing waste and production upsets.
Implementation Method 1
Demulsifier chemicals enhance the separation of the tight emulsion of salty water and oil according to specifications related to basic sediment and water content
Data Source
AI summary
A computer-implemented method includes controlling water separation in a hydrocarbon stream flowing through a separator train including one or more separator vessels located upstream of a dehydrator by manipulating a demulsifier flowrate added to the separator train by: receiving data from a real-time process test of the separation train, estimating model fit parameters to the data to generate a water separation profile (WSP) correlating water draw-off and demulsifier flowrate for the separation train, determining a maximum and a minimum demulsifier flowrate from the WSP, receiving, from an operator, a separation performance for a target water separation value entering the dehydrator downstream from the separator train, and adjusting the demulsifier flowrate according to the WSP to achieve the target water separation entering the dehydrator.