Partial Separation Multiphase Flow Meter for Subsea Slug Handling
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Solution Overview
Problem
Conventional separation type multiphase flow meters are not suitable for subsea applications due to the need for active regulation and are unable to handle slug flows and high salinity water, which affects signal transmission and accuracy in measuring hydrocarbon liquid, water, and gas flow rates.
Innovation Solution
A separation type multiphase flow meter apparatus with a partial separation module that uses a dual-phase meter for the gas fraction and a multiphase meter for the liquid fraction, allowing for accurate measurement of water-in-liquid ratio and flow rates without active control, using standard subsea piping elements and maintaining signal quality through scalable design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional multi-phase and wet gas meters are used in measurement loops, then accurate measurement of phase flow rates can be achieved, but the GVF operational range requirements cannot be guaranteed under subsea conditions with slugs and high salinity water
Solution Approach 1:
The patent divides the measurement system into two separate measurement loops: a main liquid measurement loop and a secondary gas measurement loop. Each loop uses metering devices optimized for its specific phase composition, allowing accurate measurements without requiring the entire system to maintain a specific GVF range. The separation module splits the multiphase flow into these two loops, enabling each meter to operate in its optimal measurement range regardless of overall flow conditions.
2Measurement precision
If a large, actively regulated separation module is used to guarantee GVF operational range, then measurement accuracy can be maintained, but device complexity and active control requirements increase
Solution Approach 1:
The separation module performs only partial separation of the multiphase flow, directing a portion of the gas phase to the secondary measurement loop while allowing the majority of gas to remain in the main loop. This partial separation is sufficient to enable accurate water-in-liquid ratio measurement in the liquid loop without requiring complete phase separation or active regulation mechanisms.
Solution Approach 2:
The system uses the naturally occurring phase distribution in the multiphase flow to automatically populate the two measurement loops. The separation module passively allows gas and liquid phases to distribute themselves based on flow dynamics, eliminating the need for active control systems, regulators, or complex adjustment mechanisms while still achieving the required measurement capabilities.
3Productivity
If the cross-sectional flow area of the first metering device is larger than the second metering device, then gas fraction measurement capacity is improved, but liquid fraction measurement precision may be compromised
Solution Approach 1:
Each metering device is sized and designed with specific qualities optimized for its measurement task. The first metering device in the gas-dominated loop has a larger cross-sectional area suitable for measuring gas flow rates, while the second metering device in the liquid-dominated loop has appropriate dimensions for accurate liquid measurement. This local optimization allows each device to perform its specific function at peak efficiency.
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 apparatus provides a robust, scalable, and accurate measurement of hydrocarbon flow rates in subsea environments, handling high salinity water and slug flows without active regulation, ensuring reliable operation across a wide GVF range and improving liquid property measurement accuracy.
Implementation Method 1
a separation module arranged to at least partially separate a multiphase stream comprising water, hydrocarbon liquid and hydrocarbon gas into a first sub-stream comprising a gas fraction and a second sub-stream comprising a liquid fraction
Data Source
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AI summary
A separation type multiphase flow meter apparatus (10) comprising a separation module (18) arranged to at least partially separate a multiphase stream comprising water, hydrocarbon liquid and hydrocarbon gas into a first sub-stream comprising a gas fraction and a second sub-stream comprising a liquid fraction. The apparatus comprises a first metering dev ice (16) for measuring the flow rate of the first sub-stream, and a second metering device (17) for measuring the phase fraction and the flow rate of the second sub-stream, wherein the second metering device is arranged to measure the water-in-liquid ratio (WLR ) of the second sub-stream, wherein the apparatus is arranged to use the WLR measured by the second metering device as a measure also for the WLR of the first sub-stream, and wherein the cross-sectional flow area of the first metering device is larger than the cross-sectional flow area of the second metering device.