CO2 storage efficiency is a metric that expresses the portion of the pore space of a subsurface geologic formation that is available to store CO2. Estimates of storage efficiency for large-scale geologic CO2 storage depend on a variety of factors including geologic properties and operational design. These factors govern estimates on CO2 storage resources, the longevity of storage sites, and potential pressure buildup in storage reservoirs. This study employs numerical modeling to quantify CO2 injection well numbers, well spacing, and storage efficiency as a function of geologic formation properties, open-versus-closed boundary conditions, and injection with or without brine extraction. The set of modeling runs is important as it allows the comparison of controlling factors on CO2 storage efficiency. Brine extraction in closed domains can result in storage efficiencies that are similar to those of injection in open-boundary domains. Geomechanical constraints on downhole pressure at both injection and extraction wells lower CO2 storage efficiency as compared to the idealized scenario in which the same volumes of CO2 and brine are injected and extracted, respectively. Geomechanical constraints should be taken into account to avoid potential damage to the storage site.

High-resolution, spatially distributed ground water flow models can prove unsuitable for the rapid, interactive analysis that is increasingly demanded to support a participatory decision environment. To address this shortcoming, we extend the idea of multiple cell (Bear 1979) and compartmental (Campana and Simpson 1984) ground water models developed within the context of spatial system dynamics (Ahmad and Simonovic 2004) for rapid scenario analysis. We term this approach compartmental-spatial system dynamics (CSSD). The goal is to balance spatial aggregation necessary to achieve a real-time integrative and interactive decision environment while maintaining sufficient model complexity to yield a meaningful representation of the regional ground water system. As a test case, a 51-compartment CSSD model was built and calibrated from a 100,0001 cell MODFLOW (McDonald and Harbaugh 1988) model of the Albuquerque Basin in central New Mexico (McAda and Barroll 2002). Seventy-seven percent of historical drawdowns predicted by the MODFLOW model were within 1 m of the corresponding CSSD estimates, and in 80% of the historical model run years the CSSD model estimates of river leakage, reservoir leakage, ground water flow to agricultural drains, and riparian evapotranspiration were within 30% of the corresponding estimates from McAda and Barroll (2002), with improved model agreement during the scenario period. Comparisons of model results demonstrate both advantages and limitations of the CCSD model approach.

Summary Subsurface storage of carbon dioxide (CO2) has geologic and economic uncertainties that must be addressed as part of a performance assessment. A model presented herein links uncertainty in geologic heterogeneity and associated well injectivity to variability in costs. This includes a novel averaging scheme for CO2 injectivity using geostatistical realizations of petrophysical properties and a systems-level model that includes costs of drilling and completion of injection wells. Using the Mount Simon Formation in the Illinois basin, USA, as a test case, this analysis demonstrates how the underlying costs of CO2-subsurface-storage projects can be highly sensitive to geologic heterogeneity.

The Water, Energy, and Carbon Sequestration Simulation Model (WECSsim) is a national dynamic simulation model that calculates and assesses capturing, transporting, and storing CO 2 in deep saline formations from all coal and natural gas-fired power plants in the U.S. An overarching capability of WECSsim is to also account for simultaneous CO 2 injection and water extraction within the same geological saline formation. Extracting, treating, and using these saline waters to cool the power plant is one way to develop more value from using saline formations as CO 2 storage locations.WECSsim allows for both one-to-one comparisons of a single power plant to a single saline formation along with the ability to develop a national CO 2 storage supply curve and related national assessments for these formations. This report summarizes the scope, structure, and methodology of WECSsim along with a few key results. Developing WECSsim from a small scoping study to the full national-scale modeling effort took approximately 5 years. This report represents the culmination of that effort.The key findings from the WECSsim model indicate the U.S. has several decades' worth of storage for CO 2 in saline formations when managed appropriately. Competition for subsurface storage capacity, intrastate flows of CO 2 and water, and a supportive regulatory environment all Sandia National Laboratories (SNL) and the authors would like to thank the National Energy Technology Laboratory (NETL), and Andrea McNemar and the Existing Plants, Emissions & Capture (EPEC) program in particular, for funding and guiding the research in the areas of Energy-Water Program Management and Research. Thanks also go to Lynn Brickett, Jared Ciferno, Andrea Dunn, and Tom Feeley of NETL for their guidance and support of this project. Additionally, the authors wish to thank Mike Hightower from SNL for his initial insights, Malynda Cappelle of the University of Texas at El Paso for her contributions to this work by providing insights to the water treatment engineering and cost analyses, as well as Jim Krumhansl, Sean A. McKenna, and La Tonya Walker for their contributions.

No abstract