Multiphase Flow Composition via Dual-State Molar Balance
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Solution Overview
Problem
Existing methods for determining the total hydrocarbon composition of multiphase flows rely on flow metering and single-phase sampling, which introduce uncertainties and are costly or impractical, leading to errors in composition measurement that affect processing and transport efficiency.
Innovation Solution
A method that samples gas and liquid at two different thermodynamic states, using molar balance to calculate gas and liquid molar fractions and derive overall composition independently of flow measurement, without requiring flow instrumentation, by altering pressure and temperature conditions across a device in the flow path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If flow metering and single-phase sampling are used to determine total hydrocarbon composition, then composition data can be obtained for processing and transport decisions, but measurement uncertainties and errors are introduced that affect accuracy
Solution Approach 1:
The patent applies parameter changes by measuring phase compositions at two different thermodynamic states (pressure and/or temperature conditions) rather than a single state. This allows the system to capture composition variations and calculate the true total hydrocarbon composition through molar balance calculations, eliminating uncertainties associated with flow metering and single-state sampling.
Solution Approach 2:
The patent introduces molar balance calculations as an intermediary method to determine total composition. Instead of directly measuring total composition through problematic flow metering, the system measures individual phase compositions at two states and uses molar conservation principles to compute the total hydrocarbon composition, thereby eliminating direct dependence on unreliable flow measurements.
2Measurement precision
If bottom-hole single-phase samples are obtained to determine total composition, then accurate composition data can be achieved, but sampling becomes difficult and costly or even impossible
Solution Approach 1:
The patent creates a practical alternative to difficult bottom-hole sampling by taking easily obtainable surface or wellhead samples at two different thermodynamic states. These accessible samples serve as copies that, when analyzed through the dual-state method, provide the same compositional information that would require difficult bottom-hole sampling to obtain traditionally.
Solution Approach 2:
Instead of changing the sampling location to difficult-to-access bottom-hole points, the patent changes the thermodynamic parameters (pressure and/or temperature) of the easily obtainable samples. By analyzing compositions at two different P-T states, the method achieves accurate total composition determination without the sampling difficulties of bottom-hole acquisition.
3Productivity
If flow metering is used to recombine gas and oil compositions into total hydrocarbon composition, then composition can be calculated, but flow measurement errors lead to poor composition results that create a feedback loop of decreasing accuracy
Solution Approach 1:
The patent extracts the composition determination process from its dependence on flow metering measurements. By using molar balance calculations based on phase compositions at two thermodynamic states, the method removes the problematic flow rate measurements from the composition calculation chain, breaking the feedback loop where flow errors propagate to composition errors.
Solution Approach 2:
The patent introduces molar balance calculations as an intermediary that eliminates the need for flow metering in composition determination. Instead of using flow rates to recombine phase compositions, the system uses conservation of moles across two thermodynamic states to compute total composition, thereby removing the source of measurement errors.
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 provides accurate hydrocarbon composition measurement independent of flow metering uncertainties, reducing errors and costs, and enabling more efficient processing and transport by using molar conservation principles to maintain composition accuracy across different thermodynamic states.
Implementation Method 1
using the molar balance of the samples at the two different thermodynamic states to calculate the gas and liquid molar fraction
Implementation Method 2
by altering pressure and temperature conditions across a device in the flow path
Implementation Method 3
by altering pressure and temperature conditions across a device in the flow path
Data Source
AI summary
In a method for determining a total hydrocarbon composition of a multiphase flow including gas and liquid, the method includes taking different samples of the gas and liquid at at least two different thermodynamic states of the multiphase flow. The method further includes analyzing the different samples, and using a molar balance of the different samples at the at least two different thermodynamic states to calculate a gas molar fraction and a liquid molar fraction. The gas molar fraction and liquid molar fraction may be used for deriving an overall composition of the multiphase flow and for deriving the gas and liquid volume fractions.