Oil and gas metering techniques encompass the methods and instruments used to measure the flow rate and total volume of hydrocarbons at production, processing, and transfer points. Accurate metering is required for custody transfer (fiscal metering), production allocation, process control, and regulatory compliance. The choice of metering technique depends on the fluid type, flow range, required accuracy, and operating conditions.
Metering stations are among the most critical installations in the oil and gas value chain, as measurement errors translate directly into financial losses or gains between trading parties.
Common Metering Techniques
Metering Technique Measurement Principle Typical Accuracy Application Turbine meter Rotor speed proportional to flow ±0.15-0.25% Custody transfer (liquids) Coriolis meter Mass flow via tube vibration ±0.1-0.5% Custody transfer (liquids, LNG) Ultrasonic meter Transit time of ultrasonic pulses ±0.15-0.5% Custody transfer (gas, liquids) Orifice plate Differential pressure across restriction ±0.5-2% Process/allocation metering Venturi meter Differential pressure in converging tube ±0.5-1.5% High-flow gas/liquid metering Vortex meter Vortex shedding frequency ±0.75-1% Steam, gas, process metering PD (positive displacement) Discrete volume chambers ±0.1-0.25% Custody transfer (liquids) V-cone meter Differential pressure (cone element) ±0.5-1% Wet gas, multiphase Multiphase meter Combined techniques ±2-5% per phase Subsea, wellhead, unprocessed flow
Custody Transfer vs Process Metering
Parameter Custody Transfer (Fiscal) Process Metering Purpose Commercial transaction measurement Process control and monitoring Accuracy ±0.15-0.25% (liquid), ±0.5-1% (gas) ±1-5% Calibration Prover-calibrated (traceable) Factory calibration Redundancy Multiple meter runs + check meter Single meter typical Standards API MPMS, ISO 5167, AGA reports Company standards Proving Regular proving runs required Not required Audit trail Mandatory (flow computer logs) Optional Cost High (meter + prover + computer) Moderate
Meter Selection by Fluid
Fluid Preferred Meter Types Notes Crude oil Turbine, Coriolis, PD Custody transfer requires proving Natural gas Ultrasonic, orifice plate, turbine AGA Report No. 9 (ultrasonic) LNG Coriolis Mass-based measurement preferred Refined products Turbine, Coriolis, PD API MPMS Chapter 5 Wet gas V-cone, Venturi, multiphase Liquid fraction correction needed Multiphase (unprocessed) Multiphase meter Subsea and wellhead applications Steam Vortex, orifice plate Compensate for pressure/temperature Water (produced/injection) Electromagnetic, ultrasonic Non-invasive preferred
Key Standards
Metering in oil and gas is governed by comprehensive standards:
Standard Scope API MPMS (Manual of Petroleum Measurement Standards)Complete petroleum measurement reference AGA Report No. 3 Orifice metering of natural gas AGA Report No. 7 Turbine metering of natural gas AGA Report No. 9 Ultrasonic metering of natural gas ISO 5167 Differential pressure devices (orifice, Venturi, nozzle) API MPMS Ch. 5 Liquid metering OIML R117 Dynamic measurement of liquids
Ultrasonic meters have become the preferred technology for new custody transfer gas metering stations, replacing orifice plates. They offer no pressure drop, no moving parts, a wider turndown ratio (up to 50:1), and diagnostic capabilities that detect installation and flow profile issues. However, they require a well-conditioned flow profile (typically 20D upstream straight pipe) unless a flow conditioner is installed with the meter run .
Read the full guide to flow meters
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