The initial subsurface risk assessment of SCS sites is similar to petroleum exploration. The focus is on quantifying the characteristics of a potential storage reservoir and the chance that it will be discovered. We classify these as current risks, which can be evaluated by drilling a well today.
Beyond these are future risks impacting whether we can store some contracted volume of CO2 over a multi-decade project life. Assessment of these risks requires the use of dynamic models calibrated to seismic surveys, injection rates, and other data. Although these models are periodically updated, they are unlikely to provide a complete and accurate view of subsurface behavior, especially beyond the timeframe for typical production operations. As such, they are insufficient for a full risk assessment.
There are multiple risk assessment techniques that have been adapted from other industries and applied to SCS projects. Many of these techniques have been published and demonstrated via case studies. However, due to the complexity, long timeframes, and uniqueness of each SCS project, no single existing published risk assessment technique will be universally suitable. Therefore, we advocate defining a robust framework that acknowledges learnings from past projects, utilizes the best combination of existing risk assessment methods for each project, and enables the understanding of project risk to evolve as the project progresses.
A key purpose for such a framework is to quantify the risk profile of a project through time, including a determination of those periods of Peak Risk when the system is close to maximum stress and the risk of an event occurring is highest. In developing such a framework, we incorporate the following elements which will be discussed in succeeding posts:
- Application of a staged approach
- Defining risking scales
- The quantitative risking scale
- Comprehensive event and hazard identification
- Linking events and hazards to impacts
- Quantifying the frequency of long-term events
- Changes in the risk profile over time and peak risk
- The peak risk workflow and results
- Review and refinement of risks