Subsea Chemical Injection With Coriolis Mass Flow Feedback
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Solution Overview
Problem
Existing subsea chemical injection systems face challenges in accurately and consistently delivering low chemical dosages relative to high seawater flow rates, particularly in subsea hydrocarbon production facilities, due to the significant volume disparity and remote operation complexity, making it difficult to coordinate chemical pumps with seawater pumps and maintain desired chemical-to-seawater proportions.
Innovation Solution
A subsea chemical injection assembly that includes a seawater pump with a volume flowmeter and a chemical injection pump equipped with a Coriolis tube mass flowmeter, housed in a pressure vessel, allowing for closed-loop control of chemical flow rates to maintain a desired proportion over a wide range of seawater flow rates, using a system controller to adjust chemical pumps or valves automatically.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If chemical pumps and seawater pumps are coordinated remotely through ROV or umbilical, then subsea chemical injection can be performed, but accurate monitoring and control of chemical dosage becomes difficult due to the significantly different volumes and remote operation complexity
Solution Approach 1:
A flow meter is introduced as an intermediary device between the chemical pump and the control system. This flow meter directly measures the chemical flow rate at the injection point, providing accurate real-time data about actual chemical dosage. The control system uses this feedback to automatically adjust the chemical pump, eliminating the complexity of remote coordination while maintaining precise dosage control.
Solution Approach 2:
The system implements a closed-loop feedback control mechanism where the flow meter continuously monitors chemical flow rate and feeds this information back to the control system. The control system compares the measured flow rate with the desired dosage rate and automatically adjusts the chemical pump accordingly, ensuring accurate chemical dosage despite variations in seawater flow rate or pump performance.
2Manufacturing precision
If chemical dosage rate is kept very low (e.g., 0.0004 litres/minute) relative to seawater flow rate (e.g., 2200 litres/minute), then accurate chemical injection is achieved, but the significant volume disparity makes coordination between chemical pumps and seawater pumps increasingly difficult
Solution Approach 1:
The chemical pump system is equipped with its own dedicated flow meter and control mechanism, making it self-regulating. The flow meter directly measures the chemical flow rate, and the control system automatically adjusts the chemical pump based on this measurement, independent of seawater pump operations. This self-service approach eliminates the need for complex coordination between chemically and seawater pumps, allowing accurate low dosage injection even with large volume disparities.
3Adaptability or versatility
If chemical injection system is operated remotely at or near the seabed, then subsea chemical injection is enabled, but accurate monitoring and control of chemical dosage becomes difficult
Solution Approach 1:
The system replaces complex mechanical remote control mechanisms with electronic sensing and control. A flow meter with electronic sensors directly measures chemical flow rate at the injection point, and an electronic control system processes this data to automatically adjust the chemical pump. This substitution of electronic systems for mechanical remote control enables accurate dosage monitoring and control while maintaining subsea operation capability.
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 system ensures precise and consistent chemical dosing, achieving a desired chemical-to-seawater ratio regardless of seawater flow fluctuations, enhancing production efficiency and accuracy in subsea hydrocarbon operations.
Implementation Method 1
at least one chemical subsea mass flowmeter, wherein the chemical subsea mass flowmeter comprises a Coriolis tube
Data Source
Figure 1
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Figure 2B
AI summary
A subsea chemical injection system and method for injecting chemicals into a hydrocarbon production assembly adjacent the seabed wherein a seawater volume flowmeter is utilized to measure seawater pumped through the system and a chemical subsea mass flowmeter is used to measure a chemical injected into the seawater, where the chemical subsea mass flowmeter measures the chemical at a pressure less than the seawater pumped through the system. Based on the chemical subsea mass flowmeter measurement, the flowrate of a chemical injected into the seawater can be adjusted to a predetermined setpoint corresponding to the flowrate of seawater pumped through the system. The chemical subsea mass flowmeter includes a Coriolis tube and chemical injection process pump housed within a pressure vessel. The subsea chemical injection system may be carried on a skid.