National Risk Assessment Partnership
The Need for Quantitative Risk Assessment for Carbon Utilization and Storage
Carbon utilization and storage—the injection of carbon dioxide (CO2) into permanent underground and terrestrial storage sites—is an important part of our nation’s strategy for managing CO2 emissions. Several pilot- to intermediate-scale carbon storage projects have been performed in the U.S. and across the world. However, some hurdles still exist before carbon storage becomes a reality in the U.S. at a large scale.
From a technical point of view, carbon storage risk analysis is complicated by the fact that all geologic storage sites are not created equally. Every potential site comes with an individual set of characteristics, including type of storage formation, mineral makeup, caprock characteristics, potential natural and artificial CO2 migration pathways, and history of tectonic activity. In addition, the characteristics of a site change over time, as do the risks associated with it. Most risks will increase or decrease with time.
Of particular relevance to making a business case for large-scale, long-term storage feasibility is the development of quantitative science-based methods for estimating long-term risks. Such methods and the tools derived from them will help address two of the more important challenges for full scale carbon storage: long-term liability and cost of monitoring, particularly for post-injection site care.
The National Risk Assessment Partnership Initiative
The National Risk Assessment Partnership (NRAP) is a DOE initiative that harnesses core capabilities developed across the National Laboratory complex, in the science-based prediction of the critical behavior of engineered-natural systems.
This core DOE capability is unique within the federal government and can support key decisions and technological solutions tied to many energy challenges, including CO2 capture, utilization and storage (CCUS), shale-gas production, production of deepwater resources, and engineered geothermal systems.
NRAP is fostered by the National Energy Technology Laboratory (NETL) Strategic Center for Coal (SCC) and is a consortium consisting of national laboratories’ research capabilities spanning DOE’s Office of Fossil Energy (NETL-RUA), DOE’s National Nuclear Security Administration (Lawrence Livermore National Laboratory and Los Alamos National Laboratory) and DOE’s Office of Science (Lawrence Berkeley National Laboratory, and Pacific Northwest National Laboratory).
The NRAP initiative is currently focused in support of the business case for commercial deployment of CCUS. In particular, the goal of this work is to develop defensible, science-based methodologies and platforms for quantifying risk and reducing uncertainties in order to guide decision-making and risk-management strategies that efficiently achieve DOE’s goal of 99 percent storage permanence. NRAP will also develop monitoring and mitigation protocols to reduce uncertainty in the predicted long-term behavior of a site.
The NRAP program receives input from industry, government, non-government organizations, and academia regarding research needs for large-scale CO2 storage deployment. The NRAP collaborative also keeps abreast of international developments by participating in collaborations like the International Energy Agency Greenhouse Gas Research and Development Programme’s Risk Assessment Network.
To assist in effective site characterization, selection, operation, and management, NRAP is considering potential risks associated with key operational concerns, as well as those associated with long-term liabilities. Operational issues include the management of reservoir pressure and stress to avoid conditions that might induce seismic activity. Issues associated with long-term liabilities include groundwater protection and storage permanence to avoid CO2 leakage.
Figure 1. Risk profile curve, similar to Benson, 2004, describing the risks
and associated uncertainties of a storage project over time.
NRAP Products, Expected Benefits, and Accomplishments
The NRAP project will be executed in three phases, each of which improves the science-based platform. Phase I is underway for the FY10–FY14 timeframe and focuses on quantification of risk profiles, trapping mechanisms, and associated uncertainties.
Phase II is ongoing and runs to FY15. Phase II focuses on the identification and development of risk management approaches that include strategic monitoring to verify system performance and lower uncertainty.
Phase III addresses a potential need for additional data from field test(s). An integral component of the NRAP approach is to utilize laboratory and field data to calibrate and validate models. NRAP’s strategy in Phase I is to exploit existing data and ongoing field efforts to the extent possible, augmenting these data through the use of targeted laboratory-data and field-data efforts. Consequently, a Phase III field effort may be proposed for FY14 and FY15.
NRAP products for carbon utilization and storage include:
Simulation toolsets and protocols for quantifying storage performance and potential risks. Primary toolsets include integrated assessment models (IAMs), supported by associated reduced-order models (ROMs). The first generation NRAP toolset was completed during FY12, and is currently being beta tested by the NRAP community. The second and third generation toolsets will add functionality and detail, as well as providing improved efficiency. Once completed and tested, these toolsets (IAMs, ROMs) will be made accessible publically through the Energy Data eXchange (EDX), with the first being made available in 2013.
Broadly applicable quantitative models for predicting the behavior of specific components at a storage site (such as changes in wellbore permeability due to chemical reaction). Descriptions of the protocols and models (both detailed process models and ROMs) are being made available through the production of a publically available technical report series (TRS).
A web-accessible database of critical parameters for calibrating models needed to predict CO2 storage and potential risks. Calibration and validation data developed in the course of laboratory and field studies will be made available both through the TRS mechanism and through the EDX (as detailed datasets). First releases are expected by second quarter FY13.
Comprehensive technical assessments of key storage security relationships and issues. These assessments will be made broadly available as part of the technical report series.
Expected results and benefits of NRAP’s efforts include:
Achieving the goal 99 percent storage retention across a range of variable factors at a storage site.
Reducing barriers to CCUS deployment by lowering uncertainties in liability valuation studies through quantitative, science-based predictions through development of a robust methodology and platform (computational tools) for quantifying risks (and associated uncertainties).
Guidelines and management strategies for the effective and efficient operation of storage sites (informed by a common, quantitative framework and by comprehensive technical evaluations on key issues developed by a multi-organizational team).
Confidence in setting storage-security metrics by providing a science-based ability to identify safe operational envelopes that minimize potential risks across a range of storage environments.
The tools and improved scientific base developed by the collaborative will help operators design and apply monitoring and mitigation strategies. They will help regulators and their agents quantify risks and perform cost-benefit analyses for specific Carbon Capture and Storage (CCS) projects. Finally, financiers and regulators will be able to invest in and approve CCS projects with greater confidence because costs of long-term liability can be estimated more easily and with less uncertainty.
NRAP has completed its first generation toolset, which includes:
First versions of integrated assessment models (and underpinning process models) for predicting potential for CO2 release to the atmosphere, potential for CO2 or brine impact on groundwater, and ground-motion due to fluid injection at a site.
ROMs for brine- and gas-filled reservoir types, which were based on detailed sensitivity analyses using research and commercial simulators and based on both look-up tables and sophisticated artificial intelligence algorithms.
Detailed process models for fluid release along a wellbore with various completion characteristics (including open wells, wells with poor cement, and wells with good cement) or along a discrete fault whose properties were predicted with coupled geomechanics simulator.
Figure 2. Preliminary results of quantitative assessment of IPCC Storage Goal
of 99 percent retention for a particular site type.
ROMs for two end-member groundwater aquifers based on detailed hydrogeochemical simulations coupled to uncertainty-quantification software (PSUADE).
Additionally, NRAP has performed an initial quantitative analysis to address the Intergovernmental Panel on Climate Change (IPCC) goal of 99 percent storage retention at certain sites, and determining that the likelihood of achieving that goal is much higher than 99 percent at certain sites. NRAP is in the process of completing detailed, publically releasable reports on each of its products as well as providing web access to the underpinning models and calibration data to date. In addition, NRAP will be using results from the first generation to assess the accuracy and efficiency of various approaches to ROM development.