ISO 23978:2020

Overview

ISO 23978:2020 - "Natural gas - Upstream area - Determination of composition by Laser Raman spectroscopy" defines a standardized method for quantitative determination of natural gas composition in the upstream sector using laser Raman spectroscopy. The standard describes the measurement principle, required instrument components, calibration procedures, data handling, repeatability and uncertainty evaluation to support reliable on‑site and laboratory analysis of upstream natural gas samples.

Key topics and technical requirements

• Measurement principle: Raman scattering from a monochromatic laser; spectral detection of Raman‑shifted photons and conversion to component concentrations using linear relationships between photon counts and concentration.
• Instrument components: Laser source, optical path, gas sampling chamber, detection module (external spectrograph with multichannel detectors such as CCD/CMOS, or intracavity discrete detectors like APDs), signal processing and user interface, sample filtration/probe, pressure regulator and sulfur compound absorber.
• Laser specifications: Wavelength range 500–800 nm (commonly 785 nm suggested); requirements for narrow linewidth and high stability (initial stability better than ±0.005 nm noted).
• Detection details: External cavity (spectrograph + multichannel detector) or intracavity (optical filter + APD/PMT). Note: current analysers often provide 8 APD detector positions per module; multiple modules can be operated in parallel for more species.
• Calibration and measurement procedures: Defined zero calibration, base span calibration (to remove cross‑interference and drift) and working span calibration (for concentration calculation); guidance on calibration frequency, sample preparation and data recording.
• Performance parameters: Specification of analytical ranges and precision for common components (see table below). Procedures for repeatability and uncertainty evaluation are included.
• Component ranges covered (indicative precision ranges):
  • Methane CH4: 50–100 mol%
  • Ethane C2H6: 0.02–20 mol%
  • Propane C3H8: 0.02–10 mol%
  • Nitrogen N2: 0.02–10 mol%
  • Carbon dioxide CO2: 0.02–30 mol%
  • Hydrogen sulfide H2S: 0.02–30 mol%

Applications

• Rapid, simultaneous multi‑species analysis for upstream natural gas exploration, well testing and production monitoring.
• Real‑time on‑site composition monitoring for well operations, early processing decisions, and optimization of dehydration/processing units.
• Field QA/QC, continuous monitoring during flowback or gas lift operations where fast response and no moving parts are advantageous.
• Complementary or alternative method to gas chromatography for applications needing faster, optical‑based measurement.

Who should use this standard

• Oil & gas operators and upstream engineers
• Field analytical teams and on‑site laboratories
• Instrument manufacturers and system integrators of Raman gas analysers
• Metrology and QA/QC personnel responsible for gas composition reporting and uncertainty assessment

Related standards

• ISO 6974‑1 to ISO 6974‑6, ISO/TR 14749 (gas chromatography methods)
• ISO 6142‑1, ISO 6144, ISO 6145 (calibration gas preparation)
• ISO 10715 (sampling guidelines)
• ISO 11095 (linear calibration using reference materials)

This standard is essential for implementing reliable, rapid laser Raman spectroscopy for upstream natural gas composition analysis and for ensuring consistent calibration, uncertainty estimation and reporting.