State of Stress Analysis Tool

Comprehensively assessing subsurface stress conditions

3d image of sediment layers with screenshot images of the state of analysis tool

Conceptual and visual outputs from the State of Stress Analysis Tool (SOSAT) showing geomechanical risk estimation at a geological carbon storage site. SOSAT enables users to evaluate and predict potential geomechanical risks, ensuring safe and effective CO₂ sequestration by analyzing the state of stress within the geological formations.

(Illustration by Nathan Johnson | Pacific Northwest National Laboratory)

About the State of Stress Analysis Tool

Pressure changes induced by CO₂ injection operations alter the state of stress at geological carbon storage sites. These changes in the pre-injection geomechanical conditions can potentially lead to the formation or reactivation of fractures, which could also provide pathways for CO₂ leakage or trigger induced seismicity. Therefore, it is critical to understand the baseline conditions of the sites and to assess the expected increased risks associated with CO₂ injection to proactively prevent any potential unsafe operations.

National Risk Assessment Partnership (NRAP) scientists recognized years ago the need for a tool to aid industry partners with decision-making on such a potential risk.

The NRAP State of Stress Analysis Tool (SOSAT), led by Pacific Northwest National Laboratory (PNNL), is designed to comprehensively assess subsurface stress conditions in a given area. It leverages a wide array of readily available characterization data, including well logs, well test data (such as leakoff and minifrac tests), regional geological insights, and constraints imposed by the presence of faults and fractures. With its intuitive interface, it empowers users to conduct detailed evaluations of potential geomechanical risks within a specified geographic region, in the context of planned geological carbon storage operations.

Over the last few years, SOSAT has assisted operators and regulators in enhancing their capabilities and fostering safe operations while also contributing significantly to expanding knowledge on this critical topic to promote a deeper understanding and implementation of best practices.

How does SOSAT work?

The State of Stress Analysis Tool (SOSAT) comprehensively assesses subsurface stress conditions in a given area. It leverages a wide array of readily available characterization data, including well logs, well test data, regional geological insights, and constraints imposed by the presence of faults and fractures. With its intuitive interface, SOSAT empowers users to conduct detailed evaluations of potential risks within a specified geographic region, in the context of planned geological carbon storage operations. (Pacific Northwest National Laboratory)

Within the area of interest, SOSAT takes available field measurements, quantifies parameter uncertainty, and constrains the initial conditions referred to as the state of stress. Subsequently, based on the uncertainty of each parameter, SOSAT generates millions of random stress samples to determine the probability of fault activation and hydraulic fracturing resulting from the pore pressure increase associated with CO₂ injection. The calculated probability of geomechanical risks empowers operators to formulate effective execution plans. These plans may involve conducting additional field tests to minimize uncertainty, opting for a site with lower risk, and devising an injection plan that aligns with the identified risks. These strategic approaches guided by SOSAT allow operators to navigate potential challenges and optimize decision-making for successful geological carbon storage operations.