Foreword

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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.

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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