Program Background and Project Benefits
The overall goal of the Department of Energy’s (DOE) Carbon Storage Program is to develop and advance technologies that will significantly improve the effectiveness of geologic carbon storage, reduce the cost of implementation, and prepare for widespread commercial deployment between 2020 and 2030. Research conducted to develop these technologies will ensure safe and permanent storage of carbon dioxide (CO2) to reduce greenhouse gas (GHG) emissions without adversely affecting energy use or hindering economic growth.
Geologic carbon storage involves the injection of CO2 into underground formations that have the ability to securely contain the CO2 permanently. Technologies being developed for geologic carbon storage are focused on five storage types: oil and gasreservoirs, saline formations, unmineable coal seams, basalts, and organic-rich shales. Technologies being developed will work towards meeting carbon storage programmatic goals of (1) estimating CO2 storage capacity +/- 30 percent in geologic formations; (2) ensuring 99 percent storage permanence; (3) improving efficiency of storage operations; and (4) developing Best Practices Manuals. These technologies will lead to future CO2 management for coal-based electric power generating facilities and other industrial CO2 emitters by enabling the storage and utilization of CO2 in all storage types.
The DOE Carbon Storage Program encompasses five Technology Areas: (1) Geologic Storage and Simulation and Risk Assessment (GSRA), (2) Monitoring, Verification, Accounting (MVA) and Assessment, (3) CO2 Use and Re-Use, (4) Regional Carbon Sequestration Partnerships (RCSP), and (5) Focus Area for Sequestration Science. The first three Technology Areas comprise the Core Research and Development (R&D) that includes studies ranging from applied laboratory to pilot-scale research focused on developing new technologies and systems for GHG mitigation through carbon storage. This project is part of the Core R&D GSRA Technology Area and works to develop technologies and simulation tools to ensure secure geologic storage of CO2. It is critical that technologies are available to aid in characterizing geologic formations before CO2-injection takes place in order to predict the CO2 storage resource and develop CO2 injection techniques that achieve optimal use of the pore space in the reservoir and avoid fracturing the confining zone (caprock). The program’s R&D strategy includes adapting and applying existing technologies that can be utilized in the next five years, while concurrently developing innovative and advanced technologies that will be deployed in the decade beyond. This project seeks to develop an enhanced analytical simulation tool for simplified reservoir models to predict pressure impact on CO2 injectivity and reservoir-storage capacity of geologic formations.
Through integration of rock mechanics, brine evaporation, salt precipitation, and brine-management, a science-based, simulation tool will be made available to major stakeholders. Analysis of brine extraction for pressure relief could be a technique that would improve pressure management, improve storage capacity, and help meet the Carbon Storage Programmatic goal of improving CO2 storage efficiency. Improving CO2 storage capacity estimates in regions that were previously considered unsuitable for storage (because of small size of reservoirs) could provide more potential sites for geologic CO2 storage; some of which could be in proximity to anthropogenic CO2. In addition, NPV-based analysis is designed to ensure maximization of stakeholders’ profits by optimizing the number of injection/extraction wells need to conduct carbon storage operations. In many numerical simulation packages, managing uncertainty of results is difficult because of the computationally expensive calculations. The EASiTool benefits include fast calculations and minimal input requirements from the user, allowing efficient uncertainty-quantification methods to be integrated into the EASiTool. Such an array of features would attract nontechnical, as well as technical, users to the EASiTool as a resource for the evaluation of carbon storage reservoirs.
The overall objective of this project is to develop the EASiTool for simplified reservoir modeling to predict pressure impact on CO2 injectivity and reservoir-storage capacity of geological formations. In addition, the EASiTool will be used to consider brine management as an option to control pressure elevation and provide uncertainty analysis of model prediction. An NPV-based estimation of the number of required injection/extraction wells is also being developed. Specific project objectives include the following:
Development of Analytical Solutions for Pressure Buildup: Researchers will develop analytical and semianalytical models for pressure-buildup calculations for open- and closed-boundary formations, incorporating brine evaporation around the injecting well and salt precipitation. These models will allow calculation of reservoir capacity and local injectivity and estimation of the number of required injection wells for any given geological formation.
Rock Geomechanics Impact on Pressure Buildup and Capacity Estimation: Researchers will couple the analytical and semianalytical models with geomechanical models to make new estimates of the capacity and injectivity of geological formations. Rock deformation at the reservoir scale due to increased reservoir pressure will be studied. In addition, limitation dictated by rock geomechanics based on maximum allowable injection rates will be integrated into the models. Uncertainty-quantification concepts developed in the previous task will be updated to incorporate new geomechanical parameters.
Brine-Management Impact on CO2 Injectivity and Storage Capacity: Researchers will include brine-management (extraction of brine in the formation to relieve pressure buildup) into the models developed during this project to provide a means to assess potential additional storage capacity and reduced formation pressure. Uncertainty quantification concepts, like the costs of drilling and brine handling, are being developed from the project and will be updated as new input parameters.