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This pilot will investigate CO2 storage in saline formations in the Colorado Plateau region which underlies the 2250 MW coal-fired Navajo Generating Station, located in Northern Arizona. The Navajo Generating Station is operated by the Salt River Project (SRP). Estimated CO2 emissions for 2002 were approximately 19.9 million tons. The magnitude of the annual CO2 emissions in this area, the large storage potential of the saline formations of the Colorado Plateau and operator cooperation makes this an outstanding opportunity for assessing geologic storage options associated with large sources of CO2 in the West.
LBNL’s role in these two pilots will be to provide overall technical leadership for carryout the projects, perform modeling and monitoring and to extrapolate the results from these studies to assess the regional storage potential of these area. We will provide technical input to the development of NEPA documents for the field projects, and provide technical input for the obtaining permits from the appropriate regulatory agencies. Our approach to modeling, monitoring and verification of the pilot tests is based on the experience we gained as a result of our participation in the Frio Brine Pilot Injection Test, the Lost Hills (California) CO2 EOR pilot test and the Weyburn Project. To ensure that project goals, permitting requirements, and safety controls are achieved, we will use the process outlined in Figure 1. At the heart of our approach, is a careful requirements definition phase, followed by the repeated use of detailed simulations of flow and transport processes, coupled to a geophysical imaging code. The repeated use of these tools over the project phases – requirements definition, pre-permitting, permitting and operations – allows us meet project goals, while minimizing costs, by optimizing the injection and observation well spacing, the quantity of CO2 injected and the suite of monitoring techniques used for the pilot tests.
Simulation of the CO2 injection and storage will begin with a detailed, site-specific hydrogeological model of the pilot test site. After assembling the hydrogeological model from all of the available data, subsurface flow and transport simulations will be carried out with TOUGH2 and TOUGHREACT. The output of the flow and transport model is then imported to a geophysical simulator. The geophysical simulator allows us to calculate the geophysical response for seismic techniques, electrical and electromagnetic methods and gravity – and to evaluate whether or not the have sufficient detection limits to meet the project objectives.
For each pilot test, a comprehensive set of monitoring techniques will be evaluated and deployed as part of the tests, aimed at monitoring CO2 movement in the storage formation as well as checking for any leakage outside the primary storage formation. A combination of surface seismic reflection, Vertical Seismic Profiling (VSP) and cross-well seismic imaging will be the primary techniques used to track migration of CO2 and detect leakage from the storage formation. Injection rates will be monitored continuously. Wellhead and formation pressures will be monitored to assure that injection pressures remain within the permitting guidelines. Fluid and gas composition will be monitored using samples collected during the CO2 injection. To ensure the safety of workers on the site, surface CO2 sensors and an alarm system will be positioned at the well heads, near the injection pumps, and any other location where leakage from the surface facilities may occur. Additional subsurface and surface measurements will also be evaluated on a site-specific basis to determine which will be most effective for tracking CO2 movement before deciding which methods and monitoring configurations to deploy.
After the tests are completed, simulations will be performed using TOUGH2 and TOUGHREACT to extrapolate these results on a regional basis for the purpose of estimating overall CO2 storage capacity.