The University of Wyoming (UW) is using a combination of past and current research results to further investigate the most promising target for geologic storage of CO2 in the state of Wyoming, the Rock Springs Uplift (RSU). Within the RSU are saline formations, which are the focus of this study. Saline formations are deep sedimentary rock formations that contain brine (groundwater that is not considered potable because it contains more than 10,000 parts per million total dissolved solids) in pore spaces. Saline formations suitable for geologic storage of CO2 are typically overlain by low-permeability rock that prevents upward movement of CO2 by effectively sealing the top of the saline formation. Saline formations are promising geologic storage formations because they are quite extensive throughout North America and represent an enormous potential for CO2 geologic storage. However, due to the lack of characterization data for saline-bearing formations, relatively little is known about them when compared to oil and gas reservoirs and coal seams. Therefore, there is a greater amount of uncertainty regarding the suitability of saline formations for CO2 storage.
The project includes experimental and numerical modeling of the carbon storage process to aid in understanding the migration and storage mechanisms related to injecting mixed supercritical CO2 (mixed scCO2) into the RSU’s saline formations. Mixed scCO2 is CO2 that contains small amounts of other chemicals (sulfur compounds, nitrogen oxides, and hydrochloric acid) and exists at temperatures and pressures that give it the properties of both a gas and liquid. Capturing and storing mixed scCO2 is beneficial because the CO2 stream does not need additional purification to remove co-contaminants, which saves energy and reduces overall costs. The investigation will combine reservoir-condition core flooding experimental studies (Figure 1), numerical pore- and storage formation-scale modeling, and high-performance computing to investigate various large-scale storage schemes with the goal of understanding the permanent trapping characteristics for maximizing CO2 storage in saline formations. The results of the investiga tion are being used to inform reservoir-scale simulations utilizing detailed and realistic geologic models of RSU formations in order to identify schemes that maximize permanent trapping of mixed scCO2 released from Wyoming coal power plants. An existing and unique experimental facility will be used to perform core flooding experiments (Figure 2). The chemical and physical characteristics of injected mixed scCO2 must be understood in order to maximize CO2 storage in saline formations.
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 gas reservoirs, 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 these 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 study is designing a software model that will help determine and predict how injected CO2 migrates and is stored and trapped in the saline formations found in southwestern Wyoming.
This research will increase the understanding of the effects of injecting mixed scCO2 into deep saline aquifers. This contributes to the Carbon Storage Programmatic goals by estimating CO2 storage capacity +/- 30 percent in geologic formations and ensuring 99 percent storage permanence; Mixed scCO2 capture and storage is more efficient than other storage methods because it does not require additional treatment to remove cocontaminants. This reduces the energy needed for treatment and provides an overall cost savings. Additionally, the RSU is located in the region where coal-fired power plants produce 36 percent of the CO2 emissions in Wyoming. The ability to utilize this formation for CO2 storage will provide a cost-effective local mechanism for preventing a significant amount of CO2 from entering the atmosphere.
The goal of this project is to develop a dynamic model that will aid in understanding mixed scCO2 storage in the RSU. This improved understanding will help maximize CO2 storage. This goal will be accomplished by achieving the following objectives:
Laboratory measurement of relative permeabilities under conditions similar to those within the storage formation.
Measurement of the delayed effects that mixed scCO2 injection will have on relative permeability within the storage formation (hysteresis of permeability within the formation).
Characterization of the ability of mixed scCO2 to spread over the solid surface areas within the saline formation (the wettability of the formation).
Development of a pore-scale model for rock samples from the RSU. The model will be validated against the permeability/wettability data obtained to provide improvements to the existing model.
Conducting an optimization analysis of long term permanent trapping of mixed scCO2 through high-resolution numerical experiments taking into account storage formation heterogeneity, saturation history, dissolution, capillary trapping, geomechanical deformation due to injection of massive quantities of mixed scCO2, well location, and injection pattern.
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