Calibrating and Quantifying Subsurface Risk in CO2 Storage Projects
Abstract:
While large-scale subsurface carbon storage is relatively new, the process of storing injected fluids underground is not. As an industry, we have decades of experience in natural gas storage, waterflooding, and EOR gas injection projects. These operations provide insights into the types and frequencies of sub-surface failures that might be expected for CO2 storage projects.
Failure types include 1) a low seal capacity of the overlying caprock, 2) the migration of injected fluids along fractures or across faults, 3) an overestimate of the volume available for storage, 4) the migration of fluids away from the injector in an unanticipated direction, 5) induced seismicity, 6) poor wellbore integrity creating conduits for injected fluids and 7) well pressure interference.
Failure frequencies are normally quite low on an annual basis, but if the goal is to retain 99% of the injected CO2 for hundreds of years, then an annual failure rate of just 1% per year means that a failure over the life of the project is certain. As such, operators and regulators need to focus on data gathering and analyses that reduce risk associated with long-term CO2 storage.
It is also important to note that risk exposure is not constant throughout the life of a project. For example, a period of “peak risk” may exist towards the end of injection when the reservoir pressure is greatest. The recognition of such periods is important so that critical monitoring and mitigation can be planned.
To quantify risk, we’ve developed a rigorous workflow grounded in the principles of the Storage Resources Management System (SRMS) coupled with our experience in risking petroleum projects. The workflow begins with questions about the project scope and characteristics followed by Monte Carlo simulation to 1) develop an annual chance-weighted risk profile and 2) quantify the capital at risk across the project stages.
Oil and gas companies accept that there will be project failures and use the portfolio effect to ensure the value of successful projects exceeds total program costs. However, given that CCUS is in its infancy, investors, regulators and the public may have little tolerance for unexpected CO2 releases into shallow water aquifers, the seabed, or atmosphere. As such, it’s important to fully characterize the risk profile of these projects in order to recognize, avoid and mitigate potential adverse events.
Speaker: Creties Jenkins, Rose Subsurface Assessment.
Join us on Friday 20 September at 8:00 AM (CDT)