National foreword

This British Standard is the UK implementation of ISO 24835‑2:2025.

The UK participation in its preparation was entrusted to Technical Committee CPI/30/2, Differential pressure methods.

A list of organizations represented on this committee can be obtained on request to its committee manager.

Contractual and legal considerations

This publication has been prepared in good faith, however no representation, warranty, assurance or undertaking (express or implied) is or will be made, and no responsibility or liability is or will be accepted by BSI in relation to the adequacy, accuracy, completeness or reasonableness of this publication. All and any such responsibility and liability is expressly disclaimed to the full extent permitted by the law.

This publication is provided as is, and is to be used at the recipient’s own risk.

The recipient is advised to consider seeking professional guidance with respect to its use of this publication.

This publication is not intended to constitute a contract. Users are responsible for its correct application.

Compliance with a British Standard cannot confer immunity from legal obligations.

This British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 November 2025.

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.

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, which serves 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 help 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.

1 Scope

This document specifies the principles, instruments, materials and experimental conditions for testing Young’s modulus and Poisson’s ratio using triaxial testing method. It also specifies the sampling and mechanical testing procedures, as well as the method and precision requirements for calculating shale mechanical brittleness index based on Young’s modulus and Poisson’s ratio.

This document is applicable to reservoir quality evaluation and sweet spot identification in shale gas production.

2 Normative references

3 Terms and definitions

4 Principles

5 Apparatus, tools and materials

5.1 Apparatus

5.2 Tools and materials

6 Sample preparation

6.1

6.2

6.3

6.4

6.5

6.6

6.7

6.8

7 Triaxial testing

7.1 Procedure

7.2 Stress and strain calculation

7.3 Calculation of Young’s modulus and Poisson’s ratio

8 Calculation of shale mechanical brittleness index

8.1

8.2

9 Precision

9.1 Repeatability

9.2 Reproducibility

10 Test report

Bibliography

BS ISO 24835-2:2025

Natural gas upstream area — Determination and calculation of shale brittleness index - Determination of shale mechanical characteristics based on triaxial testing method

Current

Published:

30 Nov 2025