Dual Impedance Sensing for Multiphase Flow Composition Accuracy
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Solution Overview
Problem
Existing methods for measuring the composition of multiphase fluid flow in hydrocarbon production, such as gas, water, and oil, are limited by distortions from electric field distributions outside the sensing volume and axial flow variations, making it difficult to distinguish between homogeneous and inhomogeneous flow conditions.
Innovation Solution
Utilizing two sets of electrical impedance sensors at different locations along the pipe, configured to respond similarly to homogeneous flows and differently to inhomogeneous distributions, allowing for the calculation of fluid composition by comparing their measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single sensor arrangement is used to measure electrical characteristics of the flow, then the device complexity is reduced, but the measurement precision deteriorates due to distortions from electric field distributions outside the sensing volume and axial flow variations
Solution Approach 1:
The measurement system is divided into multiple sensor arrangements (at least two) positioned at different axial locations along the pipe. Each sensor arrangement measures electrical characteristics independently, and the measurements are combined through signal processing to eliminate distortions from electric field distributions outside the sensing volume and axial flow variations, thereby improving measurement precision without requiring a single complex sensor design
2Ease of operation
If local field electrodes are used to measure along the periphery of the pipe, then the ease of operation is improved, but the measurement precision deteriorates because measurements are distorted by flow conditions in the center of the pipe
Solution Approach 1:
Multiple sensor arrangements act as intermediaries that sample the flow at different axial positions. By combining measurements from these multiple locations, the system indirectly accounts for the full cross-sectional flow distribution, including the center region, thereby improving measurement precision while maintaining the operational simplicity of peripheral electrode placement
3Ease of operation
If threshold-based measurement methods are used to detect flow changes, then the ease of operation is improved, but the measurement precision deteriorates because it is difficult to distinguish between homogeneous and inhomogeneous flow conditions
Solution Approach 1:
The system uses feedback from multiple sensor arrangements to continuously monitor and compare electrical characteristics at different axial positions. This feedback mechanism enables the system to distinguish between homogeneous and inhomogeneous flow conditions by detecting correlations or lack thereof in the measurements, thereby improving measurement precision while maintaining operational simplicity through automated signal processing
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
Enables accurate determination of fluid composition, particularly water-cut ratio, by identifying stable homogeneous periods in multiphase flows, reducing measurement errors and improving accuracy in slug periods.
Implementation Method 1
two sets of sensor arrangements, wherein each sensor arrangement is adapted to measuring electrical characteristics of the flow
Implementation Method 2
measuring low frequency electrical impedance between predetermined sets of surface plate electrodes in the periphery of the pipe. The sensors thus configured for measuring capacitance when the flow is predominantly non-conducting
Implementation Method 3
measuring conductance when the flow is conducting (typically water-continuous liquid phase)
Implementation Method 4
The measured capacitance or conductance are respectively converted to permittivity or conductivity through per se known methods
Data Source
Figure 1a~2b
Figure 3a~3b
AI summary
System for measuring the composition of a multiphase fluid flow in a pipe, the multiphase flow containing a mixture of gas and liquid. The system comprising a first and a second sensor arrangement, wherein each sensor arrangement is adapted to measuring electrical characteristics (i.e. impedance) of the flow at a predetermined rate. The system also including an analysis unit being adapted to monitor the measured electrical characteristics from said first and second sensor arrangement and to detect occurrences of time periods involving a predetermined relationship between the measured characteristics, and during these periods assuming a liquid rich phase and calculating the composition based on the electrical characteristics.