In this post, we recommend a workflow for generating an estimate of Peak Risk. The starting point is a storage complex for which the Identification stage has been completed. The data in this simplified example were derived from published information for a potential offshore CO₂ storage site. The steps in the workflow are as follows:

1. Decide on the duration of the timeframes to be used. These are generally tied to the agreed stages of the project (e.g., Identification, Appraisal, Injection and Monitoring)
2. Define the quantitative event frequency scales and build a set of financial impacts characterized on the scale; for example, Incidental, Minor, Moderate, Major, Severe and Catastrophic (see the Table below). As the financial impacts are inherently uncertain, we recommend using a lognormal distribution for each category, with the distribution defined by a P90 (low) and P10 (high) value.
3. Define and refine the list of Features, Events and Processes (FEPs) that are relevant to the particular project.
4. Proceed to evaluate, as an expert team, each FEP systematically, including the impact if the FEP should fail, and the annual chance of failure in each of the stages. An example of a simple user interface to record these discussions is presented in the Figure below illustrating the FEP “Additional Seals”.  As each FEP is evaluated the results are stored in a separate worksheet and the cumulative frequency for all FEPs is calculated and aggregated.

Our next post will feature the results of applying this workflow to the potential offshore CO₂ storage site. The Table and Figure in this post, as well as those in the next two posts are screenshots from our CarbonSureRA tool which has been built using the workflow described herein. The P90 to P10 ranges shown are user-defined variables.