ISO 24832-1:2026

• Abstract:

  This document describes the principles, equipment, materials, testing procedures, quality control and test reports for determining shale pore structure and mineral content using scanning electron microscopy (SEM) with energy dispersive spectrometer (EDS). This document is applicable to the analysis of pore structure by field emission SEM and mineral content of shale samples by SEM with EDS in shale gas exploration and development.

• Status: Published
• Publication Date: 12-Oct-2026
• ICS: 75.020 - Extraction and processing of petroleum and natural gas
• Technical Committee: ISO/TC 193/SC 3 - Upstream area
• Drafting Committee: ISO/TC 193/SC 3 - Upstream area
• Current Stage: 6060 - International Standard published
• Start Date: 13-Oct-2026
• Completion Date: 13-Oct-2026

ISO 24832-1:2026 is an ISO standard for the natural gas upstream area. It specifies how to determine shale pore structure and mineral content using scanning electron microscopy (SEM) with energy dispersive spectrometer (EDS) for shale gas exploration and development.

What does ISO 24832-1:2026 specify?

ISO 24832-1:2026 specifies the principles, apparatus, materials, sample preparation, test procedures, quality control, and test report content for measuring shale pore structure and mineral content by SEM with EDS. It is written for shale samples used in shale gas work, including pore structure analysis by field emission SEM and mineral content analysis by SEM with EDS.

The document is organized into clauses 1 to 10, followed by an informative annex and a bibliography.

Annex	What it covers
Annex A	Example of a test report, with example results for pore structure evaluation and mineral content evaluation

What are the key requirements of ISO 24832-1:2026?

ISO 24832-1:2026 sets out a workflow that starts with prepared shale samples, moves through SEM imaging and EDS analysis, and ends with calculated pore and mineral data plus a test report. In practice, the document tells the laboratory what to prepare, what instrument performance to use, how to process images, and how to judge repeatability and reproducibility.

Principle and analysis workflow

Clause 4 states that the sample is scanned by SEM to obtain images, then threshold segmentation is used to separate organic matter, inorganic minerals, and pores. The document then uses the segmented images to calculate organic matter ratio, surface porosity, and pore size distribution. For minerals, EDS X-ray spectra are compared with a mineral standard database to produce mineral distribution and composition data.

This matters because the standard is not only about taking micrographs - it also defines how to turn those images into reported pore and mineral metrics. Figure 1 shows the overall flow from shale sampling through sample preparation, SEM imaging, and data analysis.

Apparatus performance

Clause 5 gives the minimum equipment capabilities used for the analysis. For SEM, the accelerating voltage is between 1 kV and 20 kV, image pixel size is less than 10 nm, and magnification ranges from 500 times to 100 000 times. Pore structure analysis should use a large-area image automatic acquisition system.

For EDS, the resolution requirement is tied to Mn Kα full width at half maximum being less than 135 eV, and the detection range shall include B to U. The document also calls for an argon ion beam, a coater device, drying ovens, mechanical cutting equipment, a grinding polishing machine, and a cold inlay machine.

In practice, these limits matter because the image and spectrum quality has to be good enough to identify fine pores and distinguish mineral phases reliably.

Materials and sample preparation

Clause 6 lists materials such as adhesive tape, gold, platinum or carbon target material, nitrogen, and argon. The coating and gas materials are specified because sample conductivity and vacuum handling affect image quality and charging.

Clause 7 gives the sample preparation sequence. Basic sample information is recorded first, including location or well name, lithology, size, stratigraphic information, receipt time, and recorder. The sample is then cut, ground, dried, and, for pore structure work, polished by argon ion beam until the surface shows no visible scratches or undulations under SEM observation.

For poor-conductivity samples, coating is required to avoid charging effect. For mineral content work, the document allows the sample to be left unpolished. In practice, that distinction helps laboratories choose the right preparation route for the analysis they need.

Pore structure determination

Clause 8.1 covers pore structure analysis. The document requires SEM images with suitable focus, brightness, contrast, aperture alignment, and magnification. It also describes stitched, large-area imaging with a scanning range not less than 200 μm × 200 μm and a pixel size of 10 nm for high-resolution mapping.

The image analysis then separates organic matter, inorganic minerals, and pores, and calculates the organic matter ratio T, surface porosity, equivalent circle diameter, and pore size distribution. Organic and inorganic pores are treated separately and then combined into total values.

In practice, this means the laboratory must measure both the size and abundance of pores, not just report a single pore count.

Mineral content determination

Clause 8.2 covers mineral content analysis. The observation area is selected, backscattered electron images are acquired, and the EDS settings are adjusted for quantitative analysis. The document says the X-ray signal acquisition time should be long enough to achieve at least 2 000 counts per point.

Automatic mineral identification then matches the collected mineral X-ray information and backscattered electron signals with standard X-ray information, and the unknown mineral content is kept below 5 %. The final calculation uses the area of each mineral phase to determine percentage content.

This matters because the standard links image-based mineral identification to quantitative reporting, so the result is not only a visual interpretation.

Quality control and reporting

Clause 9 sets repeatability and reproducibility checks for both surface porosity and mineral content, using ISO 5725-2 and ISO 5725-6. The document gives numerical limits for repeatability and reproducibility, so the laboratory can judge whether its measurements are stable enough for routine use.

Clause 10 defines the test report content. The report includes sample details, the standards used, the method, image resolution, results and corresponding images, deviations from the procedure, unusual features, tester and checker names, and the measurement date.

What terms does ISO 24832-1:2026 define?

ISO 24832-1:2026 defines the main analysis terms used in SEM-based shale work so that laboratories report the same quantities in the same way.

• Scanning electron microscopy (SEM) - A method that forms two-dimensional images of a specimen surface using an electron beam.
• Energy dispersive spectrometer (EDS) - The detector system used to collect X-ray information for mineral identification and composition analysis.
• Charging effect - Charge accumulation on the sample surface when the electron beam hits a sample with insufficient conductive pathways.
• Working distance - The distance between the specimen surface and the bottom plane of the objective lens.
• Organic matter - Material derived from organisms and their conversion products, seen as a black porous or non-porous medium under SEM observation.
• Surface porosity - The ratio of pore area to total scanned area, expressed as a percentage.
• Pore size distribution - The incremental surface porosity within each defined pore-size range.
• Sample - Shale taken from drilling cores, drilling cuttings, or field outcrop for SEM-EDS determination.

Who uses ISO 24832-1:2026?

ISO 24832-1:2026 is used by researchers, laboratories, exploration and production companies (E&P companies), and other stakeholders in the natural gas industry. It is aimed at shale gas exploration and development work where teams need comparable data on pore structure and mineral content.

In practice, it supports laboratory analysts who prepare and image shale samples, geoscientists who interpret reservoir quality, and technical managers who need consistent reporting for comparison across sites or projects.

Which standards are used with ISO 24832-1:2026?

ISO 24832-1:2026 cites two normative references that support its measurement quality checks:

• ISO 5725-2 - Provides the basic method for determining repeatability and reproducibility of a standard measurement method.
• ISO 5725-6 - Provides practical guidance for using accuracy values.

The document also cites ISO 16700:2016 for the definition of image and working distance, and ISO 14055-1:2017 for the definition of organic matter.

What does the ISO 24832-1:2026 document contain?

ISO 24832-1:2026 contains the test workflow, equipment requirements, sample preparation steps, image-analysis formulas, and quality-control limits used for shale pore and mineral analysis. It includes formulas for organic matter ratio, surface porosity, equivalent circle diameter, and incremental and accumulative porosity for organic, inorganic, and total pores.

Annex A gives an informative example of a test report. Its tables show how pore structure results and mineral content results are organized, and its figures show example pore size distribution and accumulative surface porosity plots.

The document also includes a flowchart in the principle clause and a detailed test-report template that laboratories can adapt for routine reporting.

International
Standard
ISO 24832-1
First edition
Natural gas upstream area —
2026-10
Determination of pore structure
and mineral content for shale —
Part 1:
Scanning electron microscopy with
energy dispersive spectrometer
Gaz naturel zone amont - Détermination de la structure poreuse
et de la teneur en minéraux du schiste —
Partie 1: Microscopie électronique à balayage avec spectromètre
à dispersion d'énergie
Reference number
© ISO 2026
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus . 3
6 Materials . 4
7 Sample preparation . 4
8 Test procedure . 5
8.1 Determination of pore structure .5
8.1.1 Scanning image .5
8.1.2 Pore structure analysis .5
8.2 Determination of mineral content .7
8.2.1 Backscattered electron imaging .7
8.2.2 Quantitative analysis of minerals .7
9 Quality control . 8
9.1 Repeatability .8
9.1.1 Surface porosity .8
9.1.2 Mineral content .8
9.2 Reproducibility .9
9.2.1 Surface porosity .9
9.2.2 Mineral content .9
10 Test report . 9
Annex A (informative) Example of test report . 10
Bibliography .13

iii
Foreword
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This document was prepared by Technical Committee ISO/TC 193, Natural gas, Subcommittee SC 3, Upstream
area.
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iv
Introduction
Shale gas, as an unconventional oil and gas resource, is an important component of the world's energy
transformation process. According to the 2015 statistical data from the International Energy Information
Agency, the global technically recoverable shale gas reserves have reached 214 trillion cubic meters.
Compared with other conventional oil and gas resources, shale gas is stored in the shale developed with
micron-sized mineral grains and nanoscale pores, presenting an overall tight structure. This poses
significant challenges for measuring fundamental mineral content and characterizing the pore structure
of shale reservoirs. In shale gas production practices worldwide, considering measurement resolution,
operation generality and result reliability, two methods are widely used:
— scanning electron microscopy (SEM) with energy dispersive spectrometer (EDS);
— focused ion beam – scanning electron microscopy (FIB-SEM) with EDS.
These two methods allow for direct observation and quantification of the mineral composition of shale at
the two-dimensional scale, and nano scale pore structure in both two and three dimensions.
This document aims to improve the accuracy and consistency of analyses, standardize shale evaluation
practices and promote global data comparability to facilitate international cooperation among researchers,
laboratories, exploration and production companies (E&P companies) and other stakeholders in the natural
gas industry.
This document facilitates precise, multi-tier quantitative assessment of shale pores, crucial for reservoir
and resource evaluation, as well as optimizing drilling targets and fracturing designs. Such precision is
paramount for effective exploration and development of shale gas resources.

v
International Standard ISO 24832-1:2026(en)
Natural gas upstream area — Determination of pore structure
and mineral content for shale —
Part 1:
Scanning electron microscopy with energy dispersive
spectrometer
IMPORTANT — The electronic file of this document contains colours which are considered to be
useful for the correct understanding of the document. Users should therefore consider printing this
document using a colour printer.
1 Scope
This document describes the principles, equipment, materials, testing procedures, quality control and test
reports for determining shale pore structure and mineral content using scanning electron microscopy
(SEM) with energy dispersive spectrometer (EDS).
This document is applicable to the analysis of pore structure by field emission SEM and mineral content of
shale samples by SEM with EDS in shale gas exploration and development.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 5725-2, Accuracy (trueness and precision) of measurement methods and results — Part 2: Basic method for
the determination of repeatability and reproducibility of a standard measurement method
ISO 5725-6, Accuracy (trueness and precision) of measurement methods and results — Part 6: Use in practice of
accuracy values
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
image
two-dimensional representation of the specimen surface generated by scanning electron microscopy
[SOURCE: ISO 16700:2016, 3.2, modified — Note 1 to entry has been deleted.]
3.2
charging effect
due to the lack of sufficient conductive pathways, the phenomenon of charge accumulation occurs on the
surface of the sample when it is bombarded by an incident electron beam

3.3
working distance
distance between the specimen surface and the bottom plane of the objective lens of the scanning electron
microscopy
[SOURCE: ISO 16700:2016, 3.10]
3.4
organic matter
matter consisting of organic materials derived from organisms (including, but not limited to plants, animals,
algae and microorganisms) and the conversion products of those materials, appearing as black porous/non-
porous medium under scanning electron microscopy observation
[SOURCE: ISO 14055-1:2017, 3.2.8, modified — "plant and/or animal" has been replaced by "organic materials
derived from organisms (including, but not limited to plants, animals, algae and microorganisms)". The
second half of the definition (from "appearing as.") has been added.]
3.5
organic pores
pores developed within the organic matter of shale
3.6
inorganic pores
pores developed within or between inorganic minerals in shale
3.7
surface porosity
ratio of the pore area of the scanned sample to the overall area of the scanned sample
Note 1 to entry: Surface porosity is expressed as a percentage.
3.8
T
SEM
ratio of the total area of organic matter to the entire visual area under scanning electron microscopy
observation
3.9
pore size distribution
incremental surface porosity of each classified range shale pore size obtained by scanning electron
microscopy
3.10
sample
shale selected from drilling cores, drilling cuttings or field outcrop for pore structure and mineral content
determination by scanning electron microscopy with energy dispersive spectrometer
3.11
resolution
minimum distance between two points that can be distinguished by naked eyes in scanning electron
microscopy images
4 Principle
Scan the prepared sample using an SEM to trigger different electron signals to obtain SEM images. Perform
threshold segmentation on different images to identify organic matter, inorganic minerals and pores.
Calculate the T , surface porosity and pore size distribution. Use an energy spectrometer to obtain X-ray
SEM
signal and energy spectra. Compare the energy spectra of different minerals with the mineral standard
da
...