Dry Gas Flow Measurement Using Orifice and Iterative Correction
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Solution Overview
Problem
The challenge in accurately measuring dry gas flow from hydrocarbon wells is exacerbated by the presence of liquids, which requires costly separation equipment and leads to measurement errors, increased operational costs, and safety risks due to pressure vessels at well sites.
Innovation Solution
A method involving an orifice device with an elliptical throat at the well site to measure gas composition, flowing temperature, and pressure differential, computing liquid-to-gas ratios, and using empirical models to derive dry gas flow rates, eliminating the need for onsite separation equipment by iteratively correcting wet flow rates to obtain accurate dry gas flow rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If gas-liquid separator is installed upstream of gas measurement device, then measurement accuracy is maintained within prescribed limits, but capital expenditures and operational costs increase significantly
Solution Approach 1:
The invention extracts the liquid separation function from the measurement system by using computational methods to separate liquid and gas flow rates mathematically rather than physically. The system measures total wet gas flow and uses empirical relationships to calculate the liquid portion, then subtracts it to obtain dry gas flow rate, eliminating the need for physical separators upstream of the meter.
Solution Approach 2:
The invention replaces the mechanical separation system (gas-liquid separator) with a computational system that uses empirical equations and measured parameters (pressure, temperature, differential pressure) to calculate and separate the gas and liquid flow rates mathematically, substituting mechanical complexity with computational processing.
2Measurement precision
If gas-liquid separator and pressure vessels are installed at well site, then accurate measurement is achieved, but safety risks and operational costs increase
Solution Approach 1:
The invention removes pressure vessels and separation equipment from the well site by performing all measurements and calculations using the existing wet gas flow stream. The system uses an orifice plate, pressure transducers, and temperature sensors to measure parameters, then computationally separates gas and liquid rates without requiring physical separation or pressure containment at the measurement location.
Solution Approach 2:
The invention substitutes mechanical pressure containment and separation systems with a computational approach that processes measurements of the wet gas stream directly, eliminating safety hazards associated with pressure vessels while maintaining measurement accuracy through mathematical separation of gas and liquid phases.
3Device complexity
If wet measurement method is used without separation equipment, then capital and operational costs are reduced, but measurement accuracy may be compromised
Solution Approach 1:
The invention implements feedback through iterative calculation where the system measures total wet gas flow rate and differential pressure, estimates liquid content using empirical relationships, calculates dry gas flow rate, then uses this information to refine subsequent measurements and calculations, continuously improving accuracy without requiring physical separation.
Solution Approach 2:
The invention changes the measurement approach by using empirical relationships between measurable parameters (differential pressure, temperature, pressure) and liquid-gas ratio to dynamically calculate the liquid content and separate the flows mathematically, adapting the measurement strategy to account for varying liquid percentages in the wet gas stream.
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 method reduces capital and operational costs, increases production, and enhances safety by eliminating separation equipment and pressure vessels, while enabling real-time onsite processing and accurate royalty payments and production allocation.
Implementation Method 1
measuring a pressure differential (dP) in the orifice device
Data Source
AI summary
A method of measuring a dry gas flow from hydrocarbon wells. The hydrocarbon wells produce a stream which contains liquids and natural gas. The method comprises providing a differential flow measurement device (orifice) located at a well site containing the hydrocarbon wells. The method further includes testing the stream for gas composition and physical characteristics. Additionally, the method comprises measuring a static temperature (T) of the stream, measuring a static pressure (Ps), and measuring a pressure differential (dP) in the differential flow measurement device (orifice). The method includes computing the liquid-gas ratio (LGR) of the stream, computing the wet gas flow rate (Qw) of the stream, computing a first dry gas flow rate (Qd1) and a second dry gas flow rate and utilizing a iterative process to correct and obtain the dry gas flow rate. The data may be transmitted to another location.