ISO/PRF 24835-1

Natural gas upstream area — Determination and calculation of shale brittleness index — Part 1: Determination of shale mineral characteristics based on X-ray diffraction method

This document establishes the methods and principles, instruments, sampling, composition analysis, calculation and result reporting requirements and procedures for the calculation of shale brittleness index based on X-ray diffraction method for determining the shale mineral characteristics. This document is applicable to the testing and calculation of shale brittleness index in the assessment of reservoirs and selection of areas for marine shale gas exploration and development.

Titre manque — Partie 1: Titre manque

General Information

• Status: Not Published
• ICS: 75.060 - Natural gas
• Technical Committee: ISO/TC 193/SC 3 - Upstream area
• Drafting Committee: ISO/TC 193/SC 3 - Upstream area
• Current Stage: 5020 - FDIS ballot initiated: 2 months. Proof sent to secretariat
• Start Date: 30-Sep-2025
• Completion Date: 16-Oct-2025

Standards Content (Sample)

International
Standard
ISO 24835-1
First edition
Natural gas upstream area —
Determination and calculation of
shale brittleness index —
Part 1:
Determination of shale mineral
characteristics based on X-ray
diffraction method
PROOF/ÉPREUVE
Reference number
ISO 24835-1:2025(en) © ISO 2025

ISO 24835-1:2025(en)
© ISO 2025
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
PROOF/ÉPREUVE
ii
ISO 24835-1:2025(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principles . 2
5 Apparatus and materials . 4
5.1 Apparatus .4
5.2 Materials and tools .5
6 Sampling and sample preparation . 5
6.1 Sampling .5
6.2 Sample preparation .6
7 Composition analysis . 6
7.1 X-ray diffractometer testing .6
7.2 Data processing.7
7.3 Reference intensity analysis .7
7.4 Composition calculation .7
8 Calculation of shale mineral brittleness index . 8
9 Precision . 8
9.1 Repeatability .8
9.2 Reproducibility .8
10 Test report . 8
Annex A (normative) X-ray diffraction data . 9
Annex B (normative) Reference intensity testing and calculation method .20
Bibliography .23
PROOF/ÉPREUVE
iii
ISO 24835-1:2025(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 193, Natural gas, Subcommittee SC 3,
Upstream area.
A list of all parts in the ISO 24835 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
PROOF/ÉPREUVE
iv
ISO 24835-1:2025(en)
Introduction
This document has been developed to address the need for evaluating shale brittleness in the production
of shale gas. In order to boost shale gas production, , it is essential to create flow paths within shale gas
reservoirs through hydraulic fracturing. The shale brittleness index, serving as a crucial parameter for
forecasting the complexity of hydraulic fracturing cracks, is a vital benchmark for identifying high-quality
shale gas reservoirs. Therefore, a standardized approach for calculating the shale brittleness index can assist
stakeholders (e.g. oil companies, oilfield service providers, investment firms and governments) to accurately
pinpoint "sweet spots" within shale gas reservoirs, select promising areas with development potential, and
facilitate efficient shale gas development.
In the global shale gas production industry, two types of optimal methods for characterizing shale
brittleness index are preferred: the mineral composition method and the rock mechanics method. This is
due to their theoretical effectiveness, operational generality and result reliability. The ISO 24835 series has
been developed on the basis of these two methods.
PROOF/ÉPREUVE
v
International Standard ISO 24835-1:2025(en)
Natural gas upstream area — Determination and calculation
of shale brittleness index —
Part 1:
Determination of shale mineral characteristics based on X-ray
diffraction method
1 Scope
This document specifies the principles, instruments, materials, experimental conditions and the sampling
and composition analysis steps required for testing mineral composition using the X-ray diffraction method,
as well as the method and precision requirements for calculating shale brittleness index based on mineral
composition.
This document is applicable to reservoir quality evaluation and sweet spot identification in shale gas
production.
2 Normative references
The following documents are essential to the application of the standard. For dated references, only the
edition cited applies. For undated references, their latest edition of the referenced document (including any
amendments) applies.
ISO 3310-1, Test sieves — Technical requirements and testing — Part 1: Test sieves of metal wire cloth
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
ISO 14532, Natural gas — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions in ISO 14532 and the following 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
brittle mineral
mineral that exhibits virtually no plastic deformation prior to fracturing under external forces
Note 1 to entry: Brittle minerals are typically found in global shale gas reservoirs, include quartz, plagioclase,
kalifeldspar, calcite, dolomite and pyrite (see References [2] to [9]) and can also include ankerite and siderite.
Note 2 to entry: Adapted from ISO 18684:2020, 3.4.
PROOF/ÉPREUVE
ISO 24835-1:2025(en)
3.2
shale brittleness index
index derived from a particular brittleness characterization principle and algorithm among various options,
used for comparing the brittleness levels of different shales
3.3
shale mineral brittleness index
shale brittleness index derived through calculation based on the mineral composition of the shale
4 Principles
Each crystal mineral features a specific X-ray diffraction pattern. The intensity of characteristic peaks is
functionally proportional to the specific mineral content. The reference intensity of single mineral is tested
by means of mixed comparison. Shale mineral brittleness index is calculated from brittle mineral content.
The brittle mineral content is obtained from the X-ray diffraction pattern of shale powder sample and
Formula (1).
I  n I 
i i
X = / (1)
i
∑ 
i=1
K K
 
i i
where
X is the mass percentage content of mineral i, %;
i
I is the integral intensity of the selected diffraction peak of mineral i, counts per second;
i
K is the reference intensity of mineral i, dimensionless;
i
i is a specific mineral in shale, such as quartz and calcite;
n is the total number of mineral categories in shale.
The process for determining and calculating the shale mineral brittleness index is shown in Figure 1.
PROOF/ÉPREUVE
ISO 24835-1:2025(en)
Figure 1 — Flowchart of shale mineral brittleness index determination and calculation
PROOF/ÉPREUVE
ISO 24835-1:2025(en)
5 Apparatus and materials
5.1 Apparatus
5.1.1 X-ray diffractometer (see Figure 2), which shall meet the following requirements:
a) X-ray source shall select CuKα.
b) Absolute value of current and voltage stability deviation shall not exceed 0,005 %.
c) X-ray tube power shall be equal to or higher than 2 kW.
d) Monochromator efficiency shall be at least 25 %.
e) Resolution of X-ray diffraction receiver shall be better than 0,05°.
f)
...

ISO/DISPRF 24835-1:2025(en)
ISO/TC 193/SC 3/WG 9
Secretariat: SAC
Date: 2025-07-31
Natural gas upstream area — Determination and calculation of shale
brittleness index —
Part 1:
Determination of shale mineral characteristics based on X-ray
diffraction method
PROOF
ISO/DISPRF 24835-1:2024（2）2025(en)
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication
may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying,
or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO
at the address below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: + 41 22 749 01 11
EmailE-mail: [e-mail]
Website: www.iso.org
Published in Switzerland
© ISO/DIS 24835-1:2024(1)– 2025 – All rights reserved
ii
ISO/DISPRF 24835-1:2025(en)
Contents
Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principles . 2
5 Apparatus and materials . 4
5.1 Apparatus . 4
5.2 Materials and tools . 6
6 Sampling and sample preparation . 6
6.1 Sampling . 6
6.2 Sample preparation . 7
7 Composition analysis . 7
7.1 X-ray diffractometer testing . 7
7.2 Data processing . 8
7.3 Reference intensity analysis . 9
7.4 Composition calculation . 9
8 Calculation of shale mineral brittleness index. 9
9 Precision . 9
9.1 Repeatability . 9
9.2 Reproducibility . 9
10 Test report . 10
Annex A (normative) X-ray diffraction data . 11
Annex B (normative) Reference intensity testing and calculation method . 21
Bibliography . 24

iii
ISO/DISPRF 24835-1:2024（2）2025(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of
ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights
in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s)
which may be required to implement this document. However, implementers are cautioned that this may not
represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 193, Natural gas, Subcommittee SC 3, Upstream
area.
A list of all parts in the ISO 24835 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
© ISO/DIS 24835-1:2024(1)– 2025 – All rights reserved
iv
ISO/DISPRF 24835-1:2025(en)
Introduction
This document has been developed to address the need for evaluating shale brittleness in the production of
shale gas. In order to boost shale gas production, , it is essential to create flow paths within shale gas reservoirs
through hydraulic fracturing. The shale brittleness index, serving as a crucial parameter for forecasting the
complexity of hydraulic fracturing cracks, is a vital benchmark for identifying high-quality shale gas reservoirs.
Therefore, a standardized approach for calculating the shale brittleness index can assist stakeholders,
including (e.g. oil companies, oilfield service providers, investment firms and governments, in) to accurately
pinpointingpinpoint "sweet spots" within shale gas reservoirs, selectingselect promising areas with
development potential, and facilitatingfacilitate efficient shale gas development.
In the global shale gas production industry, two types of optimal methods for characterizing shale brittleness
index are preferred: the mineral composition method and the rock mechanics method. these methods are
preferredThis is due to their theoretical effectiveness, operational generality and result reliability. The ISO
24835 series has been developed on the basis of these two methods.
v
ISO/DIS 24835-1:2025(en)
DRAFT International Standard
Natural gas upstream area — Determination and calculation of shale
brittleness index — —
Part 1:
Determination of shale mineral characteristics based on X-ray
diffraction method
1 Scope
This document specifies the principles, instruments, materials, experimental conditions and the sampling and
composition analysis steps required for testing mineral composition using the X-ray diffraction method, as
well as the method and precision requirements for calculating shale brittleness index based on mineral
composition.
This document is applicable to reservoir quality evaluation and sweet spot identification in shale gas
production.
2 Normative references
The following documents are essential to the application of the standard. For dated references, only the edition
cited applies. For undated references, their latest edition of the referenced document (including any
amendments) applies.
ISO 3310--1, Test sieves — Technical requirements and testing — Part 1: Test sieves of metal wire cloth
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
ISO 14532, Natural gas — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions in ISO 14532 and the following 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 3.1
brittle mineral
mineral that exhibits virtually no plastic deformation prior to fracturing under external forces
ISO/DISPRF 24835-1:2024（2）2025(en)
Note 1 to entry: Brittle minerals are typically found in global shale gas reservoirs, include quartz, plagioclase,
kalifeldspar, calcite, dolomite and pyrite (see References [2 [2]] to [9 [9])]) and can also include ankerite and siderite.
Note 2 to entry: Adapted from ISO 18684:2020, 3.4.
3.2 3.2
shale brittleness index
index derived from a particular brittleness characterization principle and algorithm among various options,
used for comparing the brittleness levels of different shales
3.3 3.3
shale mineral brittleness index
shale brittleness index derived through calculation based on the mineral composition of the shale
4 Principles
Each crystal mineral features a specific X-ray diffraction pattern. The intensity of characteristic peaks is
functionally proportional to the specific mineral content. The reference intensity of single mineral is tested by
means of mixed comparison. Shale mineral brittleness index is calculated from brittle mineral content. The
brittle mineral content is obtained from the X-ray diffraction pattern of shale powder sample and
Formula (1)Formula (1). .
n
𝐼𝐼 𝐼𝐼
𝑖𝑖 𝑖𝑖
𝑋𝑋 = /[� ] (1)
𝑖𝑖
𝐾𝐾 𝐾𝐾
𝑖𝑖 𝑖𝑖
𝑖𝑖=1
where
𝑋𝑋 is the mass percentage content of mineral i, %;
𝑖𝑖
𝐼𝐼 is the integral intensity of the selected diffraction peak of mineral i, counts per second;
𝑖𝑖
𝐾𝐾 is the reference intensity of mineral i, dimensionless;
𝑖𝑖
𝑖𝑖 is a specific mineral in shale, such as quartz and calcite;
n is the total number of mineral categories in shale.
The process for determining and calculating the shale mineral brittleness index is shown in Figure 1Figure 1.
© ISO/DIS 24835-1:2024(1)– 2025 – All rights reserved
ISO/DISPRF 24835-1:2025(en)
Start
Shale sampling
X-ray diffraction sample preparation
X-ray diffraction testing
Identi�ication of shale mineral composition and
their characteristic peak integral intensity
NO
Has the reference
Aluminum oxide powder + quartz and other
intensity data table
mineral standard sample
been established?
X-ray diffraction sample preparation
YES
Typical mineral reference strength
X-raw diffraction testing
data table
Integral intensity of characteristic peaks of
mineral standards such as aluminium oxide and
quartz
Reference intensity of common minerals
Calculation of shale mineral composition
content
Shale mineral brittleness index
End
ISO/DISPRF 24835-1:2024（2）2025(en)

Figure 1 — Flowchart of shale mineral brittleness index determination and calculation
5 Apparatus and materials
5.1 Apparatus
5.1.1 5.1.1 X-ray diffractometer (see Figure 2Figure 2),), which shall meet the following requirements:
a) a) X-ray source shall select CuKα.
© ISO/DIS 24835-1:2024(1)– 2025 – All rights reserved
ISO/DISPRF 24835-1:2025(en)
b) b) Absolute value of current and voltage stability deviation shall not exceed 0,005 %.
c) c) X-ray tube power shall be equal to or higher than 2 kW.
d) d) Monochromator efficiency shall be at least 25 %.
e) e) Resolution of X-ray diffraction receiver shall be better than 0,05°.
f) f) Lower limit of narrow-angle diffraction angle testing range shall be equal to or less than 3°.
Testing range of wide-angle shall cover 5° to 90°.
g) g) For verification of main peak using standard substances (5.2.5(5.2.5), ), 𝜃𝜃 deviation shall
double
be equal to or less than 0,05°.

Key
1 X-ray generator
2 an
...