Practical Qualitative and Quantitative Models in Ccus Risk Assessment

The risks associated with CCUS require to be assessed and managed such that decisions can be made about, for example, the design, operation, monitoring and acceptability of a potential project. As with existing industrial activities, a number of approaches exist for assessing risks ranging from qualitative through to quantitative. This paper will present several approaches that have been derived from existing tools and techniques used with the process industries, adapted to meet the novel challenges of CO₂ storage projects.

There are a wide range of possible stakeholders involved in CO₂ storage projects, all of whom will require assurance that the risks are being effectively managed throughout the lifecycle. These will include the operating company, partners, shareholders, regulators, the public, insurance companies, etc. All these stakeholders will have differing information requirements for the level and depth of information provided, and each project will have to take this into account. The key steps of any risk management plan (e.g. ISO 31000) require to be met, and met in a proportionate way, taking into account the amount and certainty of information available and the end-user’s needs.

Whilst there are undoubtedly unique aspects to the risks from geological storage of CO₂, several of the existing tools that have been proven in process safety applications have been successfully repurposed in recent regulatory submissions to allow qualitative and quantitative information to be obtained and used for decision-making.

The presentation will present several approaches that can be applied to assist with decision making during the lifetime of a project.

• HAZID to assist with the identification of scenarios of concern, which can be coupled with
• Risk matrices to allow for an estimation of the risk level, together with its acceptability.
• Qualitative bowties to evaluate and communicate (internally and externally) the risk controls present.
• A Layers of Protection Analysis (LOPA) style approach has been found to be useful, when combined with bowties, to allow scenario comparison.
• Use of event trees to provide an indication of leakage risks from legacy wells.

The presentation will present the methods employed, together with a discussion of the possible applications and also limitations to each approach. It is concluded that a range of approaches is necessary, considering the available data, the uncertainties present and the requirements of end-users.