Quantifying Risks for Geologic Carbon Storage Sites

Jenny Bowman
Feb. 2, 2018, 9:51 a.m.

Geologic systems are inherently variable and often poorly characterized, and the scarcity of appropriate data make it difficult to know with certainty how a system will respond to large-scale perturbation from human activity, such as resource extraction, fluid injection and storage activities.

Within the National Energy Technology Laboratory’s (NETL) Geological & Environmental Systems (GES) directorate, researchers investigate critical behavior of engineered-geologic systems associated with fossil energy resource extraction and utilization to improve their safety, security, and effectiveness. NETL GES research leverages expertise in geology, engineering, geochemistry, geospatial data analysis, geophysics, and field monitoring to enable robust, science-based assessments that support decision making about resources and their efficient development.

The research includes work to characterize, observe, and analyze important attributes and mechanisms related to the physical, chemical, and biological behavior of complex subsurface environments from the field scale down to the molecular level, and over time spans from seconds to millennia.  That information is used to better predict and improve behavior of coal, oil, and gas extraction, resource storage, and related byproduct management.

One area of technology focus for NETL is geologic storage of human-made carbon dioxide (CO2).  Use of the world’s abundant supply of fossil energy resources–coal, oil, and natural gas–is expected to continue, and increase, for decades to meet the world’s growing demand for affordable energy, fuel economic development, and improve the quality of life for people in developed and developing nations, alike. At the same time, market demand for low-carbon energy alternatives continues to grow. Geologic formations found deep underground offer promising repositories for safe and effective storage of large volumes of human-made CO2, and geologic carbon storage (GCS) is one technology alternative that can enable continued and sustainable use of abundant fossil energy resources to supply low-carbon energy. To enable the large-scale implementation of this promising technology, it is necessary to assure key stakeholders - industry, regulators, and the public – that system behavior is well understood and can be effectively managed.

Collaboration drives innovation

NETL leads the U.S. Department of Energy’s (DOE) National Risk Assessment Partnership (NRAP), a unique collaboration that leverages the technical capabilities and expertise of five national labs: NETL, Los Alamos National Laboratory (LANL), Lawrence Berkeley National Laboratory (LBNL), Lawrence Livermore National Laboratory (LLNL), and Pacific Northwest National Laboratory (PNNL). The collaboration benefits from the perspective of a stakeholder group consisting of technical experts from industry, academia, regulatory agencies, non-governmental agencies, and insurance companies.

NETL Technical Lead for NRAP, Robert Dilmore, Ph.D., said the consortium was started to develop defensible, science-based methodologies that quantify risks and better inform decision making regarding carbon storage sites, amidst system uncertainties.

“Geological storage of CO2 is an important part of our nation’s strategy for managing CO2 emissions, but there remain uncertainties and potential liabilities inherent in owning a GCS operation that must remain safe and secure for hundreds, if not thousands, of years. To overcome that hurdle, investors require confidence that the potential environmental risks are acceptable, and can be managed.” Dilmore explained. “NRAP is delivering robust, science-based tools, methods, and key insights to quantify those risks, and clear the way for large-scale, long-term geologic carbon storage.”

The team’s pinnacle success is the NRAP Toolset, a first-of-its-kind software suite of 10 tools to predict environmental risk performance of geologic carbon storage (GCS) sites. The tools span important components of engineered geologic systems related to potential fluid leakage in the subsurface and potential for induced seismicity (minor earthquakes that could be induced by large-volume CO2 injection).

The NRAP Toolset is the only product suite that allows rapid, site-specific quantitative and probabilistic risk performance evaluation of the whole GCS system, from storage reservoir to overlying receptors (i.e., groundwater and the atmosphere). While other tools currently exist for characterizing risk of specific geologic formations, the NRAP Toolset is the only comprehensive toolset that covers all critical aspects of GCS risk performance, including both leakage risk and potential induced seismicity, with robust uncertainty quantification.

Tools for success  

The NRAP Toolset fills a gap in functionality between detailed and computationally expensive numerical simulations of individual components of a CO2 storage site, and more generalized risk assessment frameworks that often treat the engineered geologic system as a “black box” with respect to important physical and chemical phenomena. By coupling computationally efficient reduced-order models built from sets of detailed numerical models in a comprehensive integrated assessment framework, the NRAP Toolset allow for fast prediction of whole-system and system component performance that considers important physics and chemistry and maintains suitable geologic complexity, while enabling quantitative assessment of uncertainties through Monte-Carlo-type simulation. The ability to estimate uncertainty in these predictions helps to better understand alternatives and improve planning.  The individual tools and their applications are:

  • NRAP Integrated Assessment Model-Carbon Storage (NRAP-IAM-CS) simulates long-term full system behavior (from storage reservoir to aquifer/atmosphere). This tool provides results that can be used to compute risk profiles (time-lapse probability of leakage and groundwater impacts) and quantitative estimates of long-term containment effectiveness, in the context of system uncertainty.
  • The Aquifer Impact Model (AIM) tool gives a rapid probabilistic estimation of aquifer volume impacted by a potential leak of injected CO2 or saline water pushed out of the CO2 storage reservoir. This tool distinguishes between CO2 and saline water leaks and is used to determine impacted groundwater relative to selected regulatory or detection threshold criteria.
  • The Designs for Risk Evaluation and Management (DREAM) tool evaluates and selects the optimal monitoring design for a GCS site, estimating the earliest times for detection and probability of leakage detection given site- and technology-specific constraints.
  • The Multiple Source Leakage Reduced-order model (MSLR) rapidly predicts the probability that the concentration in an atmospheric plume of CO2 will exceed a defined critical concentration, given known leakage rates from one or more sources.
  • NRAP Seal Reduced-Order model (NSealR) estimates migration of brine and supercritical CO2through an imperfect (fractured or perforated) seal barrier above the injection horizon using stochastically defined parameters and Monte Carlo analyses, useful for estimating containment effectiveness.
  • The Reservoir Evaluation & Visualization (REV) tool distills key information from raw numerical reservoir simulations on reservoir pressure change and CO2 plumes sizes over time, helping to assess the portion of the site that may be subject to regulation of monitoring and site care.
  • The Reservoir Reduced-Order Model- Generator (RROM-Gen) tool generates reservoir look-up table reduced-order models (ROMs) from established reservoir simulations, which can be incorporated into NRAP Integrated Assessment Model-Carbon Storage (NRAP-IAM-CS) for site-specific risk assessment.
  • The Well Leakage Analysis Tool (WLAT) allows rapid evaluation of leakage risk from existing wells at CO2 storage sites. It models potential migration of brine and/or CO2 from the storage reservoir as a function of well disposition and reservoir conditions.
  • The Ground Motion Prediction for Induced Seismicity (GMPIS) tool estimates shaking intensity at the surface that could result from potential induced earthquakes at CO2 storage sites, providing useful information during the project planning and permitting stages.
  • The Short-Term Seismic Forecasting (STSF) tool performs a probabilistic analysis that considers the site’s previously recorded seismic history and new injection data to forecast expected seismicity rate over the next few days.

Taken together, these 10 tools represent the most complete suite of models ever assembled to assess the geological integrity and environmental risk performance of CO2 storage sites related to potential fluid leakage and ground motion. Dilmore explained that, since its release, the Toolset has served the geologic carbon storage RD&D community as a credible science-based resource for evaluating, developing, and managing geologic storage of CO2.

“The NRAP Toolset is being used by industry and fills a critical need that stakeholders from the international carbon capture and storage community have acknowledged. Specifically, the tools are providing a unique platform for rapidly analyzing and communicating environmental risk performance at planned or active carbon storage sites. The Toolset’s release marks a significant accomplishment in the Energy Department’s efforts to build stakeholder confidence that well-designed GCS operations can safely and effectively store CO2,” Dilmore said.

The NRAP Toolset has been freely distributed to researchers, regulators, developers, operators, and insurers, and it’s finding practical application for a number of proposed and active geologic storage demonstrations. The experiences of the Toolset’s diverse user base are yielding critical feedback to inform further tool development and refinement.

Now in its second phase, NRAP is applying and extending its predictive capabilities to consider active management and mitigation of GCS risks and strategic design of monitoring to reduce related uncertainties. Learning from continued field testing of NRAP tools and methods at GCS demonstration sites will help to build confidence in their predictive validity. These efforts are geared toward addressing critical questions related to assessment and management of environmental risk at CO2 storage sites, and building stakeholder confidence to proceed with industrial-scale implementation of GCS technology.

NRAP conducts risk and uncertainty analysis in the areas of reservoir performance, natural leakage pathways, wellbore integrity, groundwater protection, and systems-level monitoring.

By Jenny Bowman, Technical Writer, National Energy Technology Laboratory

R&D 100 Award Winner

The National Risk Assessment Partnership Toolset from National Energy Technology Laboratory (NETL) was a 2017 R&D 100 Award Winner. It was co-developed by Los Alamos National Laboratory, Lawrence Berkeley National Laboratory, Lawrence Livermore National Laboratory, and Pacific Northwest National Laboratory. The winners were announced at The R&D 100 Awards Gala held in Orlando, Florida on Nov. 17. The R&D 100 Awards have served as the most prestigious innovation awards program for the past 55 years, honoring R&D pioneers and their revolutionary ideas in science and technology.

See the full list of 2017 R&D 100 Award Winners here: https://www.rd100conference. com/awards/winners-finalists/year/2018/

Submissions for the 2018 R&D 100 Awards are now being accepted. Any new technical product or process that was first available for purchase or licensing between January 1, 2017 and March 31, 2018, is eligible for entry in the 2018 awards. Entries for the R&D 100 Awards can be entered under five general product categories— Mechanical Devices/ Materials, IT/Electrical, Analytical/Test, Process/Prototyping, and Software/Services. To apply visit: https://www.rd100conference.com/how-enter-rd-100-awards/