A subsurface air injection at the Hanford Site's Deep Vadose Zone Monitoring Test Bed was completed to realize a change in subsurface hydrologic conditions in accordance with a soil desiccation remedy. The injection mimicked a previous injection at the site that was performed in accordance with a vadose zone treatability study. Unlike the previous test which relied on electrical methods only, the change in hydrologic conditions during the recent test was also monitored using cross-hole seismic sensing methods to assess the ability of the seismic methods to evaluate changes in moisture conditions of desiccated sediment at the field scale. Data from in situ neutron probes indicates a reduction of soil moisture in the vicinity of the injection well due to the air injection. Similar changes were observed in the time-lapse electrical resistivity and seismic data, which indicates a loss of soil moisture over time. Tomographic inversions of the time-lapse geophysical data illustrate the 2D and 3D features of the soil moisture distribution over time. Time-lapse electrical resistivity tomography (ERT) results show a reduction in the electrical conductivity of the subsurface in the vicinity of the injection well, with most changes occurring within the screened interval. Similar patterns are observed in the seismic tomography results, with both methods illustrating two lobe-shaped features of reduced soil moisture. Use of seismic and ERT technologies in tandem takes advantage of two complementary geophysical monitoring technologies, providing increased sensitivity to specific hydrologic conditions. The multiphysics approach, therefore, has the potential to improve the ability to estimate subsurface moisture conditions from sensor-based and remotely sensed geophysical data that will ultimately improve the ability of remediation contractors to evaluate remedy performance.
Geophysical methods are useful tools for characterizing near-surface stratigraphy and monitoring changes in subsurface properties that control the efficacy of groundwater remediation technologies. Given the sensitivity of geophysical methods to subsurface properties, they are often employed to characterize complex earth systems prior to, during, and after remediation efforts. Several geophysical methods are particularly useful for understanding complex subsurface environments within an environmental remediation framework. For example, reflection seismic and electrical resistivity data can be used to characterize deep bedrock layers as well as complex overburden deposits from cataclysmic ice-age floods present at the site. Stratigraphic information provided by these methods can be reconciled with current geologic framework models to improve the site conceptual model and guide well placement to confirm important hydrogeologic features. Long-term monitoring of remedy performance can also benefit from time-lapse measurements with ground-penetrating radar, electrical resistivity, and electromagnetic induction. Utilizing these tools for both short and long-term monitoring enables a graded monitoring approach and easily scalable data collection depending on site conditions. Time-lapse electrical resistivity data can also be used to provide near real-time information on the impacts of hyporheic groundwater exchanges and the efficacy of injected amendments to inform treatability studies, which are important in final remedy decision frameworks. The U.S. Department of Energy has been operating a cleanup mission at the Hanford Superfund Site for over 30 years, utilizing geophysical technologies to support characterization and remediation monitoring of contaminated sites. Multi-modal or multi-physics methods that take advantage of sensitivities across different geophysical methods (e.g. seismic and resistivity) are approaches that may continue to be explored at Hanford. Additionally, research that focuses on how to catalog and integrate geophysical data into site repositories, conceptual models, and predictive models, will provide the technical support needed for use of these data in decision making processes. Paramount to all these efforts is the honest and forward communication of the capability of geophysical methods, including both their limitations and associated uncertainty.
Our Progress Report No. 11, RME-3145, of October 1, 1956 gave a short outline of the field work of the summer, the observations, and Impressions which were collected at the different deposits. An invited paper with the title "The Where and Why of Uranium in Sedimentary Rocks," which was read at the Western Mining Conference at Denver on February 9, 1957, incorporated some of these impressions. They are, therefore, omitted here as the paper above mentioned is being published by the Mines Magazine, Denver. Part I of this report is the "Mineralogy of the Ambrosia Lake Uranium Deposits in McKinley County, New Mexico" by James A. Knox who did most of the microscopic work and John W. Gruner. Considering the relatively small amount of field material available to us during this study, we think it a fairly detailed report and hope that it will not need much revision when other properties of the district are opened up for inspection. The remarkable feature of these Ambrosia Lake ores is their great similarity or "sameness" with respect to mineralogy, petrography, and stratigraphy over a large area. What helpful conclusions can be drawn from these observations? Do they have any bearing on origin and ore finding criteria? Part II of the report consists of additional experiments on the solubility of U and V compounds in bicarbonate solutions. More quantitative data than in last year's reports are supplied to round out our knowledge on the behavior of U and V in sedimentary environments. Part III is an additional compilation of minerals identified from properties in Arizona, Colorado, Montana, New Mexico, South Dakota, Texas, Utah, and Wyoming. Only those properties and claims are listed which were sampled in 1956 or in which new minerals were discovered since publication of our last annual report of April 1, 1956 (RME-3137, Pt. II). Numerous specimens of those identified were sent to us by the Atomic Energy Commission staff members in Denver, Qasper, Rapid City, and Austin. Individual reports were made to them as soon as identification could be made. Part IV is a short experimental study to show the improbability of reduction and precipitation of uranous oxide, UO2, by pyrite and marcasite. This reduction had been claimed by R. C. Vickers in a paper read at the Convention of the Geological Society of America in Minneapolis in November 1956. All our experiments gave negative results which should be a relief to workers in this field. For if ferrous iron could reduce U02++ at room temperature, much of the theorizing up to now would have been at fault.
Fracture systems are important pathways for fluid and solute transport and exert a critical influence on the hydraulic properties of aquifers and reservoirs. Therefore, detailed knowledge of fracture locations, connections, and evolution is crucial for both groundwater and energy applications (e.g., enhanced geothermal, oil and gas recovery, carbon sequestration, and wastewater injection). The innovative combination of distributed acoustic sensing (DAS) and ambient seismic noise techniques has the potential to detect and characterize fracture systems at high-spatial and temporal resolution without an active source. To test this, we conducted a multiphysics field experiment at Blue Canyon Dome, New Mexico. A novel energetic material developed by Sandia National Laboratories was used to generate fractures in two separate stimulations. Ambient noise was recorded before and after each stimulation using fiber-optic cables installed in the outer annulus of four boreholes surrounding the stimulation hole at a radius of 1.2 m. The Python package MSNoise was used to compute crosscorrelations and measure changes in velocity between each time period relative to the initial (prestimulation) time period. The majority of channel pairs showed a velocity reduction (average −3% relative velocity change) following both stimulations. We used a 3D Bayesian tomography approach to resolve spatial variations by utilizing differences between channel pairs. Results showed that the greatest velocity reduction was concentrated near the center of the test area and suggested the presence of a near-vertical fracture, oriented northeast to southwest for depths >19 m below ground surface and extending slightly to the southwest corner. These results were generally consistent with crosshole seismic tomography time-lapse images. DAS technology provides valuable sensing capability and — when used with a passive seismic approach — shows great promise for monitoring and characterization of fractured-rock systems.
The goal of this Laboratory Directed Research and Development (LDRD) project was to develop a borehole seismic source and sensor array to enable real-time seismic imaging at scales and conditions relevant to the energy industry including both fossil-energy and geothermal. In FY21 and FY22, we designed, built, and tested both a prototype impulse source module for generating seismic energy and a sensing module for recording ground motions generated by the source module array. A pneumatically driven vibratory source was also designed. The source modules were fabricated with all high temperature components and the team has worked to incorporate the current RT-SEISMIC electronics design into a commercially available, high temperature silicon-on-insulator chip integrated circuit. Several issues were identified during fabrication and lab testing that led to redesign of several system components and subsequent retesting. The final round of testing showed that while metal/graphite-based seals worked quite well for static seals, they were unable to provide an adequate gas seal for dynamic, reciprocating part movements which necessitated a final redesign using Kalrez. This change will result in a continuous temperature rating of approximately 275 degrees C for the system. While a field test of the RT-SEISMIC system was targeted in FY22, due to the extended lab testing and redesign efforts, field testing was not achieved. As a result of this LDRD investment, several sponsors have expressed interest in RT-SEISMIC and we expect to continue towards a field demonstration of the full system in the future.
During the initial phase of this SubTER project, we conducted a series of high resolution seis- mic imaging campaigns designed to characterize induced fractures. Fractures were emplaced using a novel explosive source, designed at Sandia National Laboratories, that limits damage to the borehole. This work provided evidence that fracture locations could be imaged at inch scales using high-frequency seismic tomography but left many fracture properties (i.e. per- meability) unresolved. We present here the results of the second phase of the project, where we developed and demonstrated emerging seismic and electrical geophysical imaging tech- nologies that characterize 1) the 3D extent and distribution of fractures stimulated from the explosive source, 2) 3D fluid transport within the stimulated fracture network through use of a contrasting tracer, and 3) fracture attributes through advanced data analysis. Focus was placed upon advancing these technologies toward near real-time acquisition and processing in order to help provide the feedback mechanism necessary to understand and control frac- ture stimulation and fluid flow. Results from this study include a comprehensive set of 4D crosshole seismic and electrical data that take advantage of change detection methodologies allowing for perturbations associated with the fracture emplacement and particulate tracer to be isolated. During the testing the team also demonstrated near real-time 4D electri- cal resistivity tomography imaging and 4D seismic tomography using the CASSM approach with a temporal resolution approaching 1 minute. All of the data collected were used to develop methods of estimating fracture attributes from seismic data, develop methods of as- similating disparate and transient data sets to improve fracture network imaging resolution, and advance capabilities for near real-time inversion of cross-hole tomographic data. These results are illustrated here. Advancements in these areas are relevant to all situations where fracture emplacement is used for reservoir stimulation (e.g. Enhanced Geothermal Systems (EGS) and tight shale gases).
