The intention of this publication is to:

- Provide a basic guide for the health and safety hazard analysis for offshore management of CO2 pipelines and platforms, where CO2 will be present as a part of carbon capture and storage (CCS) installations; communicate existing knowledge on pipeline and offshore facility design and operation; and identify areas of uncertainty where existing knowledge cannot be applied with sufficient confidence, considering the scale and nature of expected CCS operations in the future.

- Allow engineers and project managers involved in CCS projects to widen their knowledge base to ensure that procurement of equipment and operational guidelines are using current knowledge.

- Supplement the Technical Guidance on hazard analysis for onshore carbon capture installations and onshore pipelines which has previously been published.

However, this publication purposely does not include CO2 storage, nor does it address in the same level of detail, the possible environmental hazards.

It is appreciated that work is continuing in a number of areas to extend the understanding of the properties and behaviour of impure CO2 in dense phase and as a gas. This publication is intended to represent a summary of current knowledge and good practice.

The publication initially provides an understanding of the thermodynamics of pure CO2, particularly liquid CO2 (dense phase), since the majority of offshore applications will involve CO2 in this state. In dense phase conditions, typical of those that would be expected in offshore pipelines and on platforms, the thermodynamic and physical properties of CO2 are affected by impurities, and the implications of these impurities on the underlying properties are therefore addressed.

The impact of the different properties of CO2 on the hazards associated with carbon capture and storage applications are described. Some are hazards associated with CO2 itself, whereas others are associated with impurities found within CCS CO2 streams. However, designers can draw upon the considerable experience of both the offshore oil and gas industries worldwide to understand these hazards, and to minimise their impact. This publication provides guidance and references to assist with this.

There is an introduction to hazard analysis, and some of the hazards associated with CO2 for offshore CCS applications are presented, together with how these can be used in conjunction with a hazard analysis. The potential hazards to personnel, both from CO2 and the possible impurities likely to be found from the capture processes, are described. These are set in the context of how they might apply to offshore CO2 transport and injection facilities. There is an example of the composition of captured CO2, and the risks associated with operating outside of the limits described are outlined.

The publication includes simplified examples of release modelling from a number of different possible offshore scenarios to demonstrate the use of an integral programme. The scenarios chosen are low-probability high-impact events, which demonstrate the capabilities of dispersion modelling. Overall, the majority of the release scenarios chosen indicate that the potential could exist for some degree of adverse impact either for persons on the platform deck or for those close to sea level (for example, ships or rescue vessels), but they also highlight the need for additional work to be carried out in some areas.

To enable the reader to understand typical design considerations for ensuring safe offshore CO2 systems and the risk potential with respect to failure modes, some of the main system components associated with CO2 transport, injection, offshore EOR processing of CO2, and re-injection are described. This document also describes some typical mitigation techniques available to minimise the potential for failure.

This publication should supplement rather than substitute regulatory requirements, many of which are referenced within the text. The intention is to allow project developers and designers to meet their statutory obligations with increased certainty.

The existing Energy Institute (EI) documents relating to Good plant design and operation for onshore carbon capture installations and onshore pipelines should be reviewed and, if appropriate, updated, in view of the information assembled in the production of this publication. It is also recommended that some of the conclusions from the dispersion modelling exercise should be brought to the attention of the vendors so that issues discovered during the work can be considered in future releases of their programmes.