Project Evaluation: Phase II: Optimal Geological Environments for Carbon Dioxide Disposal in Brine- Bearing Formations (Aquifers) in the United States GCCC Digital Publication Series #00-01 S. D. Hovorka M. L. Romero R. H. Trevino A. G. Warne W. A. Ambrose P. R. Knox T. A. Tremblay Keywords: CO2 Storage- Brine Formations, Brine Formation Identification, Geographic Information System (GIS), Data Digitization and Integration, CO2 Storage- Site Parameters Cited as: Hovorka, S. D., Romero, M. L., Treviño, R. H., Warne, A. G., Ambrose, W. A., Knox, P. R., and Tremblay, T. A., 2000, Technical summary: optimal geological environments for carbon dioxide disposal in brine-bearing formations (aquifers) in the United States: The University of Texas at Austin, Bureau of Economic Geology, final report prepared for U.S. Department of Energy, National Energy Technology Laboratory, under contract no. DE-AC26-98FT40417, 232 p. GCCC Digital Publication Series #00-01. TECHNICAL SUMMARY Brine-bearing formations have great potential for long-term storage and disposal of greenhouse gases, especially the large volumes of CO2 produced as a byproduct of combustion of fossil fuels. Extensive industry experience in underground injection for enhanced oil recovery (EOR), gas storage, and deep-well waste injection demonstrates that disposal into geologic environments is feasible by using existing technology. It is also feasible that residence time for injected CO2 would be adequate to prevent significant negative impact on overlying potable water or the atmosphere. One underway and several planned projects show that underground-injection technologies are transferable to injection of CO2 for the purpose of reduction of greenhouse gas emissions. However, brine formations are generally unused; therefore, documentation of the properties of the subsurface are generally not compiled in easy-to-access format. Realistic and quantitative information about the relevant characteristics of the subsurface is needed to assess feasibility, costs, and risks of various types of options for CO2 disposal in brine formations. In this study, we have compiled and integrated a data base of realistic properties of brine formations. This data base is designed with a geographic structure in a geographic information system (GIS) so that it can be use to match CO2 emitters with prospective sinks. Brine formations are an attractive option as CO2 sinks because (1) brine formations underlie many parts of the U.S., reducing costs and infrastructure associated with pipeline construction; (2) assuming a hydrodynamic trapping mechanism, with structural closure not required (Bachu and others, 1994), storage volumes are adequate for almost any greenhouse-gas scenario; (3) residence times are long, and accounting for volumes sequestered is straightforward; (4) scenarios for negative impacts and unintended consequences are limited; and (5) brine formations are largely unused and subsurface rights should be available. Benefits of selecting disposal into brine formations as a greenhouse-gas-reduction method are limited by costs implicit in this method. Unlike biomass storage and various iii reuse scenarios, costs of CO2 extraction and injection into brine formations cannot be offset by any derived benefit. Therefore, one of the critical issues to consider in the brine- disposal option is cost. This data base provides input to model or assess a number of potential costs. For example, distance between emitter and injection well, which leads to pipeline costs, can be assessed for various sites. Distribution of exiting pipeline right-of- way may be a practical as well as a financial consideration, and the GIS format is ideal for this type of assessment. Formation injectivity, which controls the rate at which CO2 can be pumped into a well, impacts construction costs. Low injectivity might require property acquisition and construction costs for more wells. Site-assessment studies are smaller but more immediate costs; basin-scale characterization provides an indication of the site-specific issues that would need to be addressed in site assessment. Brine disposal has the potential to provide the longest residence times, as compared with other sequestration methods, on geologic time scales. However, various scenarios for leakage through the low-permeability seal above the injection horizon must be included in evaluating a candidate injection site. Leakage scenarios include (1) catastrophic escape of CO2, producing an asphyxiation hazard; (2) high fluxes of CO2 from the injection site to the atmosphere, reducing the benefit of the injection; (3) displacement of large volumes of displaced brine upward, impacting potable water; and (4) other unintended negative consequences. Evaluation at a site-specific scale is required to determine seal integrity, although the basin-scale evaluation provides data for preliminary evaluation of issues involving seals. Comparison of brine-formation properties shows that although they are present over large areas of the onshore U.S., sinks vary considerably in geological properties. Quantitative data in this data base permit future assessment of real variability impact on costs and the effectiveness of injection selection of one formation as compared with another. The GIS data base quantitatively describes some of the important geological properties of saline water-bearing formations in the U.S. and where geological conditions promote the greatest probability for success of pilot CO2-sequestration projects. This data base can be queried to match geologic saline-formation resources with critical economic iv and infrastructure variables to determine the optimal locations for subsequent demonstration phases and full-scale projects. We see this data base as a proactive response to the rapid evolution of knowledge about the technologies that can be applied to CO2 sequestration because the data-base format facilitates experiments and improvement of conceptual models. Furthermore, it allows stakeholders to assess multiple variables to produce a best-fit plan that unifies all land-surface variables with properties of the underlying geologic host formation. In our phase I pilot project (Hovorka, 1999), we identified significant geological attributes that impact the feasibility of injection and containment of CO2 (depth, permeability, sand-body thickness, net sand thickness, percent shale, sand-body continuity, top-seal thickness, continuity of top seal, hydrocarbon production from interval, fluid residence time, flow direction, CO2 solubility in brine [P, T, and salinity], rock/water reaction, and porosity) that can be determined for saline formations by using a variety of approaches. In well-known formations in hydrocarbon-producing areas, many variables have been determined by previous researchers and can be extracted from oil and gas data sets and from previous deep-well injection studies. For other areas, more limited, direct information can be acquired from studies of basin evolution, inventories of fresh-water and brine resources, and from deep-well injection studies. The phase I pilot project determined that data sets can be compiled to determine the range of engineering characteristics of brine-bearing formations. In this study, we compiled available quantitative and spatially indexed data for 21 onshore basins. We have been seeking venues that let us distribute these data. Identification of high-quality targets may spark interest from stakeholders in using geologic storage to reduce emissions. Stakeholders who have expressed interest in receiving the data base include oil and chemical companies, research groups and “think tanks,” and power- generation-equipment manufacturers. We expect demand to increase following release of this data base. v CONTENTS Technical summary ............................................................................................................iii Abstract ............................................................................................................................... 1 Introduction......................................................................................................................... 2 Methods............................................................................................................................... 3 Task 1. Brine-Formation Identification..................................................................... 3 Task 2. Literature and File Search for Geological Attributes of Regional Brine-Bearing Formations ............................................................................ 7 Task 3. Data Digitization and Integration ................................................................. 8 Task 4. Geographic Information System Construction............................................. 9 Task 5. Brine-Formation Evaluation....................................................................... 14 Task 6. Reporting .................................................................................................... 14 Results – Target Formations ............................................................................................. 14 Results – Limits of Study.................................................................................................. 17 Results – Data Base........................................................................................................... 17 Results – Geologic Parameters.........................................................................................