Overview
ISO 4657:2022 - Assessment specification of coalbed methane resources - defines a standardized framework for evaluating coalbed methane (CBM) resource potential. Published in 2022, this international standard specifies objectives, tasks, work processes, classification rules, and report preparation and acceptance criteria for CBM resource evaluation. ISO 4657:2022 establishes consistent methods and documentation practices to support reliable resource estimates and to underpin subsequent reserves reporting and development planning.
Key topics and technical requirements
- Evaluation workflow: a structured sequence covering data collection and collation, geological condition analysis, evaluation method selection, input-parameter assignment, resource calculation, classification and conclusions.
- Data requirements:
- Geophysical data (gravity, magnetic, seismic, electrical) to map faults, structure and coal seam depth.
- Regional geological and hydrogeological datasets, coalfield reports and adjacent-area production data.
- Drilling data: mud logging (cuttings, coring, gas logging), conventional and unconventional wireline logs (density, neutron, acoustic, NMR, imaging), and well testing.
- Laboratory tests: core description, bulk density, macerals, proximate/elemental analyses, vitrinite reflectance, gas composition, gas content (per ISO 18871), and isothermal adsorption.
- Calculation method: the volumetric method is the prescribed approach when geological data are adequate; principles for parameter assignment (thickness, density, gas content, area) must be documented and justified.
- Parameter rules and cut-offs:
- Effective (net) thickness determination and area-weighted averaging; seam cut-off for effective thickness set at 0.5 m (individual seams below this threshold are ignored after gangue deduction).
- Coal density: use arithmetic average of laboratory-measured samples.
- Gas content: laboratory measurement per ISO 18871 and conversion rules for reporting bases (dry ash-free, ash-free, air-dried).
- Resource boundaries: define gas-bearing area using geological and anthropogenic controls (faults, pinch-outs, erosion, gas-content cut-offs, weathering, spontaneous combustion, goaf) and mineral-right or geographic limits.
- Reporting: standardized content, figures and tables; Annex provides an example evaluation report outline.
Applications
- Preparing CBM resource assessments to inform exploration planning and feasibility studies.
- Supporting conversion of resource estimates into CBM reserves and economic appraisal.
- Guiding data acquisition programs (drilling, logging, lab tests) and quality requirements.
- Standardizing documentation for regulators, investors and project partners.
Who should use this standard
- Petroleum and coal geologists, reservoir and production engineers
- Energy companies and CBM developers
- Exploration and environmental consultants
- Regulators and resource auditors involved in CBM permitting and reporting
Related standards
- ISO 18871 - Method of determining coalbed methane content (normative reference cited by ISO 4657:2022)
Keywords: ISO 4657:2022, coalbed methane, CBM resource evaluation, volumetric method, gas content, wireline logging, laboratory test, resource classification, CBM reserves.