National Risk Assessment Partnership (NRAP)
The National Risk Assessment Partnership (NRAP) is an effort that harnesses the breadth of capabilities across the U.S. Department of Energy (DOE) into a mission-focused platform to develop a defensible, science-based quantitative methodology for determining risk profiles at CO2 storage sites.
NRAP includes five national labs executing collaborative research for DOE-Fossil Energy's Carbon Sequestration Program. While developing this risk-profile methodology, NRAP is also collaborating on key research needed to quantify the residual risk associated with long-term stewardship at a CO2 storage site. The five national labs are:
- Lawrence Berkeley National Laboratory (LBNL)
- Lawrence Livermore National Laboratory (LLNL)
- Los Alamos National Laboratory (LANL)
- National Energy Technology Laboratory (NETL)
- Pacific Northwest National Laboratory (PNNL)
Ensuring that large-scale CO2 storage is safe and effective requires predicting the long-term integrity of storage sites as well as demonstrating the comprehensive consideration of potential site-specific risks. The scale of storage sites makes science-based prediction challenging, and the complexity and heterogeneity of natural systems imparts a degree of uncertainty to any predictions, necessitating a stochastic component to the methodology. Integration of strategic monitoring with the predictions, however, can help to reduce these uncertainties while verifying that a site is performing as anticipated.
A quantitative methodology for predicting a site’s long-term performance is essential to the successful deployment of CCS at a commercial scale, where each storage project will represent significant capital investment and will require sound, quantitative assessments of potential long-term liabilities. Calculation of risk profiles is a common approach to assessing the predicted performance of large-scale projects, serving as an important tool for:
- Comparison of potential site options;
- Quantification of long-term project costs and potential liabilities;
- Ensuring that sites are characterized and operated in a manner that minimizes key uncertainties and maximizes performance.
Risk profiles for CO2 storage sites have been conjectured to track with CO2 injection, peaking at the end of site operations and decaying over time as the CO2 plume, pressure front, and reservoir equilibrate (Benson, 2007). However, this presumed evolution of risk profiles has yet to be confirmed. Furthermore, there is currently no quantitative methodology for determination of site-specific risk profiles, posing a barrier to rapid deployment of CCS at a commercial scale. (Addressing this barrier is the primary focus of NRAP.)
Schematic risk profile for a CO2 storage project. (Benson, 2007; WRI presentation)
Quantification of risk profiles requires predicting the behavior of the entire engineered natural system (reservoir to potential receptor). Tools for reservoir simulation and monitoring are under development at numerous institutions as part of DOE’s Carbon Sequestration Program. These tools can form the basis for calculation of risk profiles. However, integration of reservoir processes with site-specific behavior outside of the reservoir is central to calculation of risk profiles, particularly with respect to the time-evolution of key components of the storage system (e.g., well-sealing capability) and assessment of potential impacts outside of the reservoir. These non-reservoir factors necessitate coupling reservoir behavior to other components of the system via integrated assessment models.
Comparison of the predictive methods against observations is critical to demonstrate reliability and accuracy as well as to reduce uncertainties. Data from Regional Partnership field demonstrations provide critical observations for early stages of operation. Observations relevant to long-term stewardship will require analog field sites (e.g., industrial sites and natural sites like CO2 reservoirs, CO2-rich gas reservoirs, etc.).
To provide the scientific underpinning for risk assessment with respect to the long-term storage of CO2, including assessment of residual risk associated with a site post-closure.
The primary focus of NRAP is to develop a science-based quantitative methodology for determining risk profiles at storage sites. Such a methodology provides the scientific basis for assessing residual risks associated with long-term stewardship.
In addition, NRAP will develop a strategic, risk-based monitoring protocol, such that monitoring at all stages of a project effectively minimizes uncertainty in the predicted behavior of the site, thereby increasing confidence in storage integrity.
Why NRAP is the Best Approach
- Need for DOE-Developed Methodology: A DOE-developed risk-profile methodology will accelerate CCS deployment by providing a common basis for assessing potential factors associated with long-term stewardship. Although a CCS project can be designed with the goal to ensure storage integrity, a complete assessment of specific projects will require quantification of factors related to potential long-term costs.
- Need for Mission-Focused Effort: The complexity and scale of CO2 storage sites pose a significant challenge to the development of a quantitative risk-profile methodology, making the effort intractable without a rigorous mission-focused approach. NRAP will use a mission-focused philosophy to direct fundamental research strategically toward achieving the overall goal.
Leverage of DOE Investments: NRAP leverages the extensive investment that DOE has made across the national lab complex in key science/technology for predicting the performance of underground systems.
- Basic-Science Integration: Quantification of risk profiles touches all aspects of the storage system, so NRAP’s gap assessments provide focal points for interfacing mission need with basic science, guiding research needs both within NRAP and beyond.
NRAP's Technical Approach
- Modular Integrated Assessment Model (IAM): NRAP’s approach is to develop a flexible methodology that does not rely on a single, specific model. Instead, NRAP will approach the description of the system using an IAM to interface with multiple platforms that can simulate process-level detail while capturing key sub-system couplings within the overall storage system.
- Stochastic: The complexity, heterogeneity, and potential uncertainties in site-specific parameters require a stochastic treatment of the system. Initial calculations of profiles will rely largely on Monte Carlo methods using existing tools developed for geologic systems but appropriately adapted to CCS needs. The NRAP team has developed many of these tools already.
- Deterministic: Coupling of deterministic models with the IAM (e.g., in a Monte Carlo approach) will allow detailed physics and chemistry to be addressed when appropriate. The NRAP team has an extensive suite of detailed tools that have been developed and honed by DOE investments (including heavy institutional investments via LDRD initiatives).
- Iterative: NRAP is calculating initial quantitative risk profiles in year one, but these profiles are expected to have large uncertainties that will guide key research needs in subsequent years. An initial gap assessment (already completed by NRAP) will also guide research prioritization on lowering uncertainties and/or plugging gaps. Annual re-assessment of both uncertainties and key gaps/needs will refine the research focus as risk profiles are updated based on the previous year’s research.
- Confirmation: Confirmation of predictive methodologies is essential to demonstrate that key physical aspects are represented accurately. Confirmation of the risk-profile methodology will be achieved through comparison with experimental and field data (e.g., RCSP data to confirm near-term aspects and analog sites for long-term aspects). Methodology will be assessed through a combination of strategic field-data collection targeted at uncertainties in system key components coupled with application to case-study sites.
How Long will NRAP Take?
With a concerted effort, NRAP can deliver a defensible quantitative methodology over a 5-year period, which includes several years of focused field and lab research. This compressed time frame is critical to accelerate rapid deployment by 2020 by providing a methodology that can be tested during the early demonstration stages of CCS while serving as a basis for critical decision frameworks.
Technical Working Groups and Key Technical Elements:
The Technical Working Groups (WGs),are comprised of researchers from the technical teams at each of the national laboratories. WGs will be responsible for identifying key research needs to meet NRAP goals and coordinating research across national laboratories. WGs will communicate these research needs back to the technical teams, and will be used in development of each national laboratories' annual field work proposals (FWPs).
WGs are structured around key technical elements associated with risk assessment at a potential storage site (additional WGs will be established as necessary to address specific technical challenges as NRAP activities evolve. For example, a mitigation WG may be required as mitigation strategies are integrated into the risk-profile calculations):
Reservoir Performance focuses on phenomena associated with processes in the storage reservoir, including the physical and chemical response of the system to fluid flow. Key elements of this WG are to: (1) investigate the long-term trapping mechanisms in the reservoir; (2) predict quantitatively the response of the reservoir to stresses resulting from CO2 injection; (3) assess key features of the reservoir that would have an impact on capacity and injectivity, including interactions between multiple injections in the same basin; and (4) (working with the System/Risk Modeling WG) develop protocols for using predictions from reservoir simulators to quantify the pressures and CO2 saturations (and associated uncertainties) at the boundaries of the storage reservoir (principally at the base of the caprock).
Wellbore Integrity focuses on predicting the performance of wellbores, including their response to physical and chemical processes. A key element of this WG is to quantify the probability and associated uncertainties of CO2 release from wellbores over time.
Natural Seal Integrity focuses on predicting the performance of various types of seals, including analysis of fault reactivation and development of fracture pathways for CO2 movement out of the storage reservoir. A key element of this WG is to quantify the probability and associated uncertainties of CO2 release from seals over time.
Groundwater Protection focuses on predicting potential impacts to groundwater systems that could occur as a result of CO2 storage. A key element of this WG is to quantify potential changes over time to groundwater chemistry (as related to groundwater quality) as a function of the introduction of fluids (principally, CO2, and/or brine).
System/Risk Modeling focuses on system-level (probabilistic) modeling strategies for quantifying the performance and risk at a site. A key element of this WG is to develop the platform for integrating the process-level predictions from other WGs as necessary to quantify the risk profiles and the propagated uncertainties.
Strategic Monitoring focuses on the identification of factors and/or signals that could be monitored at a site to verify predictions of site performance, to lower uncertainties in predicting the performance of a site, and/or to minimize potential consequences identified in the risk assessment. A key element of this WG is to develop and validate protocols for integrating monitoring with the risk-profile calculations.