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.

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

During the exploitation and transportation of high-sulfur natural gas, elemental sulfur in the gas can be deposited in reservoirs, wellbores and pipelines. In reservoirs, sulfur deposits can reduce permeability significantly, which hinders fluid flow and lowers the production efficiency and capacity of gas wells. In pipelines, sulfur deposits can cause blockage, which in severe cases can lead to ruptures and leaks and increase safety risks. Additionally, sulfur deposits on equipment and pipelines accelerate corrosion, shorten their service life and increase maintenance costs. Therefore, sulfur deposition not only results in direct economic losses to oil and gas operations but also poses safety and environmental risks that require urgent and effective management measures.

Determining the solubility of sulfur is crucial for addressing sulfur deposits. A comprehensive understanding of sulfur dissolution characteristics can be achieved by experimentally studying sulfur solubility under various pressure and temperature conditions. This enables the assessment of the risk of sulfur precipitation under specific conditions. This knowledge allows engineers to optimize the operation system of sulfur-containing gas wells and pipelines, e.g. by adjusting pressure and temperature to reduce its precipitation and deposition. Additionally, determining sulfur solubility can aid in developing models to predict sulfur deposition. These models quantitatively describe sulfur precipitation patterns, which helps identify potential deposition issues early so that appropriate preventive measures can be implemented. Through these preventive measures, sulfur deposits in gas production and transportation can be controlled in a scientific and effective way, thus minimizing their impact on operations.

The samples tested in this document include sour gas collected from downhole, wellhead or separator by using a sampler, or sour gas prepared in the laboratory. This document does not involve the natural gas sampling process, for which the procedure and safety requirements should follow existing standards.

Currently, there are various methods to determine elemental sulfur solubility, but no unified standard has been established. Consistent methods are essential for comparable results. This document will ensure valid data and high-quality analysis. Therefore, a unified solubility determination method is crucial for oil and gas developers, service companies, investors, governments and other stakeholders. This document aims to provide a simple and reliable method for determining the elemental sulfur solubility in sour gas fields.

1 Scope

This document specifies the instruments and equipment, reagents and materials, preparation, measurement procedure, calculations and precision for determining the solubility of elemental sulfur using the saturated dissolution method.

This document covers the determination of sour gas samples collected from downhole, wellhead or separator using a sampler, or sour gas prepared in the laboratory, the sampling process of which is not involved.

2 Normative references

3 Terms and definitions

4 Principle

5 Instrument and apparatus

5.1 Apparatus

5.1.19

5.1.20

5.1.21

5.2 Verification/calibration requirements

6 Reagents and materials

6.1

6.2

6.3

6.4

7 Preparation

7.1 Recording of ambient temperature and pressure

7.2 Inspection of sour gas sample

7.3 Inspection of apparatus (5.1) for airtightness

7.4 Sample preparation

7.5 Addition of absorbent liquid

7.6 Addition of desulfurizer (6.4)

8 Testing procedure

8.1 Saturated dissolution

8.2 Release of gas

8.3 Absorption of elemental sulfur

8.4 Measurement of gas volume

8.5 Treatment of tail gas

8.6 Collection of elemental sulfur

8.7 Weighing

9 Calculation

9.1

9.2

9.3

10 Precision

10.1 Repeatability limit

10.2 Reproducibility limit

11 Report

12 Practices of safe operation

Bibliography