24 Matching Results

Search Results

Advanced search parameters have been applied.

Borehole-to-borehole geophysical methods applied to investigations of high level waste repository sites

Description: This discussion focuses on the use of borehole to borehole geophysical measurements to detect geological discontinuities in High Level Waste (HLW) repository sites. The need for these techniques arises from: (a) the requirement that a HLW repository's characteristics and projected performance be known with a high degree of confidence; and (b) the inadequacy of other geophysical methods in mapping fractures. Probing configurations which can be used to characterize HLW sites are described. Results from experiments in which these techniques were applied to problems similar to those expected at repository sites are briefly discussed. The use of a procedure designed to reduce uncertainty associated with all geophysical exploration techniques is proposed; key components of the procedure are defined.
Date: January 1, 1983
Creator: Ramirez, A.L.
Partner: UNT Libraries Government Documents Department

New developments in measurements technology relevant to the studies of deep geological repositories in bedded salt

Description: This report presents new developments in measurement technology relevant to the studies of deep geological repositories for nuclear waste disposal during all phases of development, i.e., site selection, site characterization, construction, operation, and decommission. Emphasis has been placed on geophysics and geotechnics with special attention to those techniques applicable to bedded salt. The techniques are grouped into sections as follows: tectonic environment, state of stress, subsurface structures, fractures, stress changes, deformation, thermal properties, fluid transport properties, and other approaches. Several areas that merit further research and developments are identified. These areas are: in situ thermal measurement techniques, fracture detection and characterization, in situ stress measurements, and creep behavior. The available instrumentations should generally be improved to have better resolution and accuracy, enhanced instrument survivability, and reliability for extended time periods in a hostile environment.
Date: October 22, 1980
Creator: Mao, N. & Ramirez, A.L.
Partner: UNT Libraries Government Documents Department

Preliminary numerical modeling results - cone penetrometer (CPT) tip used as an electrode

Description: Figure 1 shows the resistivity models considered in this study; log10 of the resistivity is shown. The graph on the upper left hand side shows a hypothetical resisitivity well log measured along a well in the upper layered model; 10% Gaussian noise has been added to the well log data. The lower model is identical to the upper one except for one square area located within the second deepest layer. Figure 2 shows the electrode configurations considered. The ''reference'' case (upper frame) considers point electrodes located along the surface and along a vertical borehole. The ''CPT electrode'' case (middle frame) assumes that the CPT tip serves as an electrode that is electrically connected to the push rod; the surface electrodes are used in conjuction with the moving CPT electrode. The ''isolated CPT electrode'' case assumes that the electrode at the CPT tip is electrically isolated from the pushrod. Note that the separate CPT push rods in the middle and lower frames are shown separated to clarify the figure; in reality, there is only one pushrod that is changing length as the probe advances. Figure 3 shows three pole-pole measurement schemes were considered; in all cases, the ''get lost'' electrodes were the leftmost and rightmost surface electrodes. The top frame shows the reference scheme where all surface and borehole electrodes can be used. The middle frame shows two possible configurations available when a CPT mounted electrode is used. Note that only one of the four poles can be located along the borehole at any given time; electrode combinations such as the one depicted in blue (upper frame) are not possible in this case. The bottom frame shows a sample configuration where only the surface electrodes are used. Figure 4 shows the results obtained for the various measurement schemes. The white lines ...
Date: December 19, 2006
Creator: Ramirez, A L
Partner: UNT Libraries Government Documents Department

Electromagnetic experiment to map in situ water in heated welded tuff: Preliminary results

Description: An experiment was conducted in Tunnel Complex G at the Nevada Test Site to evaluate geotomography as a possible candidate for in situ monitoring of hydrology in the near field of a heater placed in densely welded tuff. Alterant tomographs of 200 MHz electromagnetic permittivity were made for a vertical and a horizontal plane. After the 1 kilowatt heater was turned on, the tomographs indicated a rapid and strong drying adjacent to the heater. Moisture loss was not symmetric about the heater, but seemed to be strongly influenced by heterogeneity in the rock mass. The linear character of many tomographic features and their spatial correlation with fractures mapped in boreholes are evidence that drying was most rapid along some fractures. When the heater was turned off, an increase in moisture content occurred around the heater and along the dry fractures. However, this process is much slower and the magnitude of the moisture increase much smaller than the changes observed during heating of the rock. The interpretation of the tomographs is preliminary until they can be processed without the restrictive assumption of straight ray paths for the signals through the highly heterogeneous rock mass. 15 refs., 4 figs.
Date: March 16, 1987
Creator: Ramirez, A.L. & Daily, W.D.
Partner: UNT Libraries Government Documents Department

Geophysical tomography for imaging water movement in welded tuff

Description: Alterant tomography has been evaluated for its ability to delineate in-situ water flow paths in a fractured welded-tuff rock mass. The evaluation involved a field experiment in which tomographs of electromagnetic attenuation factor (or attenuation rate) at 300 MHz were made before, during, and after the introduction to the rock of two different water-based tracers: a plain water and dye solution, and salt water and dye. Alterant tomographs were constructed by subtracting, cell by cell, the attenuation factors derived from measurements before each tracer was added to the rock mass from the attenuation factors derived after each tracer was added. The alterant tomographs were compared with other evidence of water movement in the rock: borescope logs of fractures, and post experiment cores used to locate the dye tracer on the fractured surfaces. These comparisons indicate that alterant tomography is suitable for mapping water flow through fractures and that it may be useful in inferring which of the fractures are hydrologically connected in the image plane. The technique appears to be sensitive enough to delineate flow through a single fracture and to define fractures with a spatial resolution of about 10 cm on an imaging scale of a few meters. 9 refs., 3 figs.
Date: September 1, 1986
Creator: Daily, W.D. & Ramirez, A.L.
Partner: UNT Libraries Government Documents Department

Preliminary evaluation of alterant geophysical tomography in welded tuff

Description: The ability of alterant geophysical tomography to delineate flow paths in a welded tuff rock mass has been preliminarily evaluated based on the results of a field experiment. Electromagnetic measurements were made before, during and after a water-based, dye tracer flowed through the rock mass. Alterant geophysical tomographs were generated and compared with independent evidence - borescope logs, neutron logs and dyed rock samples. Anomalies present in the tomograph match the location and orientation of fractures mapped with a borescope. The location of tracer-strained fractures coincides with the location of some image anomalies; other geophysical anomalies exist where tracer-strained fractures were not observed, perhaps due to poor core recovery. Additional drilling to locate stained flow paths and other experiments are planned so that the applicability of the technique can be further evaluated. 7 refs., 5 figs.
Date: February 1, 1985
Creator: Ramirez, A.L. & Daily, W.D.
Partner: UNT Libraries Government Documents Department

New developments in measurement technology relevant to the studies of deep geological repositories in domed salt and basalt

Description: This report briefly describes recent geophysical and geotechnical instrumentation developments relevant to the studies of deep geologic repositories. Special emphasis has been placed on techniques that appear to minimize measurement problems associated with repositories constructed in basalt or domed salt. Included in the listing are existing measurement capabilities and deficiencies that have been identified by a few authors and instrumentation workshops that have assessed the capabilities of existing instrumentation with respect to repository applications. These deficiencies have been compared with the reported advantages and limitations of the new developments described. Based on these comparisons, areas that merit further research and development have been identified. The report is based on a thorough literature review and on discussions with several instrumentation specialists involved in instrumentation development.
Date: May 21, 1980
Creator: Ramirez, A.L. & Mao, N.H.
Partner: UNT Libraries Government Documents Department

Brief overview of geophysical probing technology

Description: An evaluation of high-resolution geophysical techniques which can be used to characterize a nulcear waste disposal site is being conducted by the Lawrence Livermore National Laboratory (LLNL) at the request of the US Nuclear Regulatory Commisson (NRC). LLNL is involved in research work aimed at evaluating the current capabilities and limitations of geophysical methods used for site selection. This report provides a brief overview of the capabilities and limitations associated with this technology and explains how our work addresses some of the present limitations. We are examining both seismic and electromagnetic techniques to obtain high-resolution information. We are also assessing the usefulness of geotomography in mapping fracture zones remotely. Finally, we are collecting core samples from a site in an effort to assess the capability of correlating such geophysical data with parameters of interest such as fracture continuity, orientation, and fracture density.
Date: February 1, 1982
Creator: Ramirez, A.L. & Lytle, R.J.
Partner: UNT Libraries Government Documents Department

Accuracy tests of the tessellated SLBM model

Description: We have compared the Seismic Location Base Model (SLBM) tessellated model (version 2.0 Beta, posted July 3, 2007) with the GNEMRE Unified Model. The comparison is done on a layer/depth-by-layer/depth and layer/velocity-by-layer/velocity comparison. The SLBM earth model is defined on a tessellation that spans the globe at a constant resolution of about 1 degree (Ballard, 2007). For the tests, we used the earth model in file ''unified{_}iasp.grid''. This model contains the top 8 layers of the Unified Model (UM) embedded in a global IASP91 grid. Our test queried the same set of nodes included in the UM model file. To query the model stored in memory, we used some of the functionality built into the SLBMInterface object. We used the method get InterpolatedPoint() to return desired values for each layer at user-specified points. The values returned include: depth to the top of each layer, layer velocity, layer thickness and (for the upper-mantle layer) velocity gradient. The SLBM earth model has an extra middle crust layer whose values are used when Pg/Lg phases are being calculated. This extra layer was not accessed by our tests. Figures 1 to 8 compare the layer depths, P velocities and P gradients in the UM and SLBM models. The figures show results for the three sediment layers, three crustal layers and the upper mantle layer defined in the UM model. Each layer in the models (sediment1, sediment2, sediment3, upper crust, middle crust, lower crust and upper mantle) is shown on a separate figure. The upper mantle P velocity and gradient distribution are shown on Figures 7 and 8. The left and center images in the top row of each figure is the rendering of depth to the top of the specified layer for the UM and SLBM models. When a layer has zero thickness, its ...
Date: July 20, 2007
Creator: Ramirez, A L & Myers, S C
Partner: UNT Libraries Government Documents Department

Monitoring six-phase ohmic heating of contaminated soils using electrical resistance tomography

Description: Electrical resistance tomography (ERT) was used to monitor six-phase ohmic heating used for the insitu remediation of volatile organic compounds from subsurface water and soil at the Savannah River Site, near Aiken, South Carolina. The changes in electrical conductivity caused by six-phase ohmic-heating in a clay layer located in the vadose zone were monitored during a period of approximately 2 months, before, during and after heating. From an array of electrodes located in 4 boreholes, we collected electrical resistivity data between five pairs of adjacent holes pairs. This data was used to calculate tomographs which showed the electrical conductivity changes along five vertical planes. The difference tomographs show the combined effects of moisture redistribution and heating caused by six-phase heating and vapor extraction. The tomographs show that most of the clay layer increased in electrical conductivity during the first 3 weeks of the 4 week long heating phase. At this time, the electrical conductivities near the center of the heating array were twice as large as the pre-heat conductivities. Then the electrical conductivity started to decrease for portions of the clay layer closest to the vapor extraction well. We propose that the conductivity decreases are due to the removal of moisture by the heating and vacuum extraction. Parts of the clay layer near the extraction well reached electrical conductivities as low as 40% of the pre-heating values. We propose that these regions of lower than ambient electrical conductivities are indicators of regions where the vapor removal by vacuum extraction was most effective. At the end of the heating phase, our estimates suggest that the clay saturation may have dropped to as low as 10% based on the observed conductivity changes.
Date: September 1, 1994
Creator: Ramirez, A.L. & Daily, W.D.
Partner: UNT Libraries Government Documents Department

In-situ fracture mapping using geotomography and brine tracers

Description: The Lawrence Livermore National Laboratory is currently assessing the capabilities of high resolution geophysical methods to characterize geologic sites for the disposal of high level nuclear waste. A successful experiment has recently been performed in which salt water tracers and high frequency electromagnetic waves were utilized to map rock mass fracture zones in-situ. Multiple cross-borehole EM transmissions were used to generate a tomographic image of the fractured rock region between two boreholes. The tomographs obtained correlate well with conventional wireline geophysical logs which can be used to infer the location of fractured zones in the rock mass. This indirect data suggests that the geotomography and brine tracer technique may have merit in mapping fractured zones between boreholes.
Date: January 1, 1981
Creator: Deadrick, F.J.; Ramirez, A.L. & Lytle, R.J.
Partner: UNT Libraries Government Documents Department

Reconciling data using Markov Chain Monte Carlo: An application to the Yellow Sea - Korean Peninsula region

Description: In an effort to build seismic models that are most consistent with multiple data sets, we have applied a new probabilistic inverse technique. This method uses a Markov Chain Monte Carlo (MCMC) algorithm to sample models from a prior distribution and test them against multiple data types to generate a posterior distribution. While computationally expensive, this approach has several advantages over a single deterministic model, notably the reconciliation of different data types that constrain the model, the proper handling of uncertainties, and the ability to include prior information. We also benefit from the advantage of forward modeling rather than inverting the data. Here, we use this method to determine the crust and upper mantle structure of the Yellow Sea and Korean Peninsula (YSKP) region. We discuss the data sets, parameterization and starting model, outline the technique and its implementation, observe the behavior of the inversion, and demonstrate some of the advantages of this approach.
Date: August 30, 2004
Creator: Pasyanos, M E; Franz, G A & Ramirez, A L
Partner: UNT Libraries Government Documents Department

In situ changes in the moisture content of heated, welded tuff based on thermal neutron measurements

Description: Thermal neutron logs were collected to monitor changes in moisture content within a welded tuff rock mass heated from a borehole containing an electrical heater which remained energized for 195 days. Thermal neutron measurements were made in sampling boreholes before, during and after heating. The results generally corroborated our conceptual understanding of hydrothermal flow as well as most of the numerical modeling conducting for this study. Conceptual models have been developed in conjunction with the numerical model calculations to explain differences in the drying and re-wetting behavior above and below the heater. Numerical modeling indicated that the re-wetting of the dried-out zone was dominated by the binary diffusion of water vapor through fractures. Saturation gradients in the rock matrix resulted in relative humidity gradients which drove water vapor (primarily along fractures) back to the dried-out zone where it condensed along the fracture walls and was imbibed by the matrix. 4 refs., 28 figs.
Date: July 1, 1991
Creator: Ramirez, A.L.; Carlson, R.C. & Buscheck, T.A.
Partner: UNT Libraries Government Documents Department

Temperature measurements from a horizontal heater test in G-Tunnel

Description: A horizontal heater test was conducted in G-Tunnel, Nevada Test Site, to study the hydrothermal response of the rock mass due to a thermal loading. The results of the temperature measurements are reported here. The measured temperatures agree well with a scoping calculation that was performed using a model which investigates the transport of water, vapor, air, and heat in fractured porous media. Our results indicate that the temperature field might be affected by the initial moisture content of the rock, the fractures in the rock, the distance from the free surface of the alcove wall, and the temperature distribution on the heater surface. Higher initial moisture content, higher fracture density, and cooling from the alcove wall tend to decrease the measured temperature. The temperature on top of the horizontal heater can was about 30{degrees}C greater than at the bottom throughout most of the heating phase, causing the rock temperatures above the heater to be greater than those below. Along a radius from the center of the heater, the heating created a dry zone, followed by a boiling zone and condensation zone. Gravity drainage of the condensed water in the condensation zone had a strong effect on the boiling process in the test region. The temperatures below and to the side of the heater indicated a region receiving liquid drainage from an overlying region of condensation. We verified that a thermocouple in a thin-wall tubing measures the same temperature as one grouted in a borehole.
Date: October 1, 1991
Creator: Lin, Wunan; Ramirez, A.L. & Watwood, D.
Partner: UNT Libraries Government Documents Department

Electrical resistivity tomography at the DOE Hanford site

Description: Recent work at the DOE Hanford site has established the potential of applying Electrical Resistivity Tomography (ERT) for early leak detection under hazardous waste storage facilities. Several studies have been concluded to test the capabilities and limitations of ERT for two different applications. First, field experiments have been conducted to determine the utility of ERT to detect and map leaks from underground storage tanks during waste removal processes. Second, the use of ERT for long term vadose zone monitoring has been tested under different field conditions of depth, installation design, acquisition mode/equipment and infiltration chemistry. This work involves transferring the technology from Lawrence Livermore National Laboratory (LLNL) to the Resource Conservation and Recovery Act (RCRA) program at the DOE Hanford Site. This paper covers field training studies relevant to the second application for long term vadose zone monitoring.
Date: January 1, 1996
Creator: Narbutovskih, S.M.; Halter, T.D.; Sweeney, M.D.; Daily, W. & Ramirez, A.L.
Partner: UNT Libraries Government Documents Department

Status report on the geology of the Lawrence Livermore National Laboratory site and adjacent areas. Volume I. Text and appendices A-E

Description: In April, 1979, geoscience personnel at Lawrence Livermore National Laboratory (LLNL) initiated comprehensive geologic, seismologic, and hydrologic investigations of the LLNL site and nearby areas. These investigations have two objectives: 1. to obtain data for use in preparing a Final Environmental Impact Report for LLNL, pursuant to the National Environmental Policy Act; 2. to obtain data for use in improving the determination of a design basis earthquake for structural analysis of LLNL facilities. The first phases of these investigations have been completed. Work completed to date includes a comprehensive literature review, analyses of three sets of aerial photographs, reconnaissance geophysical surveys, examination of existing LLNL site borehole data, and the logging of seven exploratory trenches, segments of two sewer trenches, a deep building foundation excavation, a road cut, and an enlarged creek bank exposure. One absolute age date has been obtained by the /sup 14/C method and several dates of pedogenic carbonate formation have been obtained by the /sup 230/Th//sup 234/U method. A seismic monitoring network has been established, and planning for a site hydrologic monitoring program and strong motion instrument network has been completed. The seismologic and hydrologic investigations are beyond the scope of this report and will be discussed separately in future documents.
Date: October 1, 1980
Creator: Carpenter, D.W.; Puchlik, K.P.; Ramirez, A.L.; Wagoner, J.L.; Knauss, K.G. & Kasameyer, P.W.
Partner: UNT Libraries Government Documents Department

Development of a Stochastic Inversion Tool To Optimize Agreement Between The Observed And Predicted Seismic Response To CO2 Injection/Migration in the Weyburn-Midale Project

Description: During Phase 1 of the Weyburn Project (2000-2004), 4D reflection seismic data were used to map CO{sub 2} migration within the Midale reservoir, while an extensive fluid sampling program documented the geochemical evolution triggered by CO{sub 2}-brine-oil-mineral interactions. The aim of this task (3b.11) is to exploit these existing seismic and geochemical data sets, augmented by CO{sub 2}/H{sub 2}O injection and HC/H{sub 2}O production data toward optimizing the reservoir model and thereby improving site characterization and dependent predictions of long-term CO{sub 2} storage in the Weyburn-Midale reservoir. Our initial project activities have concentrated on developing a stochastic inversion method that will identify reservoir models that optimize agreement between the observed and predicted seismic response. This report describes the technical approach we have followed, the data that supports it, and associated implementation activities. The report fulfills deliverable D1 in the project's statement of work. Future deliverables will describe the development of the stochastic inversion tool that uses geochemical data to optimize the reservoir model.
Date: December 2, 2009
Creator: Ramirez, A L; Hao, Y; White, D; Carle, S; Dyer, K; Yang, X et al.
Partner: UNT Libraries Government Documents Department

Coupled THM analysis of the single-heater test at yucca mountain

Description: This paper presents a summary of results from the Single-Heater Test (SHT) at Yucca Mountain, Nevada. In the SHT, a horizontal, 5-m-long, line-heat source was used to heat a rock pillar for nine months. Moisture movement was monitored during and after heating using electrical-resistance tomography (ERT) and neutron-logging techniques. Results indicate drying in regions of the rock where temperature reached 60°C and above. The drying zone is asymmetric and is not centered on the heater, but has lobes extending above and to the sides of the heater. Predicted temperatures agreed well with observations. A cold- trap effect was predicted, in the heater borehole, that efficiently transfers heat along the heater borehole to the excavation wall. A simple thermomechanical analysis of the SHT shows that shear zones predicted for vertical fractures coincide with regions of increased moisture content derived from ERT measurements.
Date: January 25, 1999
Creator: Blair, S. C.; Buscheck, T. A.; Daily, W. D.; Lin, W. & Ramirez, A. L.
Partner: UNT Libraries Government Documents Department

Prototype Engineered Barrier System Field Test (PEBSFT); Final report

Description: This final report represents a summary of data and interpretations obtained from the Prototype Engineered Barrier System Field Test (PEBSFT) performed in G-Tunnel within the Nevada Test Site. The PEBSFT was conducted to evaluate the applicability of measurement techniques, numerical models, and procedures developed for future field tests that will be conducted in the Exploratory Studies Facilities (ESF) at Yucca Mountain. The primary objective of the test was to provide a basis for determining whether tests planned for the ESF have the potential to be successful. Chapter 1 on high frequency electromagnetic tomography discusses the rock mass electromagnetic permittivity and attenuation rate changes that were measured to characterize the water distribution in the near field of a simulated waste container. The data are used to obtain quantitative estimates of how the moisture content in the rock mass changes during heating and to infer properties of the spatial variability of water distribution, leading to conclusions about the role of fractures in the system. Chapter 2 discusses the changes in rock moisture content detected by the neutron logging probe. Chapter 3 permeability tests discusses the characterization of the in-situ permeability of the fractured tuff around the borehole. The air permeability testing apparatus, the testing procedures, and the data analysis are presented. Chapter 4 describes the moisture collection system installed in the heater borehole to trap and measure the moisture volumes. Chapter 5 describes relative humidity measurements made with the thermocouple psychrometer and capacitance sensors. Chapter 6 discusses gas pressure measurements in the G-Tunnel, addressing the calibration and installation of piezoresistive-gaged transducers. Chapter 7 describes the calibration and installation of thermocouples for temperature measurements. Chapter 8 discusses the results of the PEBSFT.
Date: August 1, 1991
Creator: Ramirez, A.L.; Buscheck, T.; Carlson, R.; Daily, W.; Lee, K.; Lin, Wunan et al.
Partner: UNT Libraries Government Documents Department

Prototype Engineered Barrier System Field Tests; Progress report

Description: This paper presents selected preliminary results obtained during the first 54 days of the Prototype Engineered Barrier System Field Tests (PEBSFT) that are being performed in G-Tunnel within the Nevada Test Site. The test described is a precursor to the Engineered Barrier Systems Field Tests (EBSFT). The EBSFT will consist of in situ tests of the geohydrologic and geochemical environment in the near field (within a few meters) of heaters emplaced in welded tuff to simulate the thermal effects of waste packages. The PEBSFTs are being conducted to evaluate the applicability of measurement techniques, numerical models, and procedures for future investigations that will be conducted in the Exploratory Shaft Facilities of the Yucca Mountain Project (YMP). The paper discusses the evolution of hydrothermal behavior during the prototype test, including rock temperatures, changes in rock moisture content, air permeability of fractures, gas pressures, and rock mass gas-phase humidity. 10 refs., 12 figs.
Date: July 26, 1989
Creator: Ramirez, A.L.; Beatty, J.; Buscheck, T.A.; Carlson, R.; Daily, W.; LaTorre, V.R. et al.
Partner: UNT Libraries Government Documents Department

Prototype heater test of the environment around a simulated waste package

Description: This paper presents selected results obtained during the 301 day duration of the Prototype Engineered Barrier System Field Test (PEBSFT) performed in G-Tunnel within the Nevada Test Site. The test described is a precursor to the Engineered Barrier Systems Field Tests (EBSFT) planned for the Exploratory Shaft Facility in Yucca Mountain. The EBSFT will consist of in situ tests of the geohydrologic and geochemical environment in the near field (within a few meters) of heaters emplaced in welded tuff to simulate the thermal effects of waste packages. The paper discusses the evolution of hydrothermal behavior during the prototype test, including rock temperatures, changes in rock moisture content, air permeability of fractures and gas-phase humidity in the heater borehole.
Date: December 31, 1991
Creator: Ramirez, A.L.; Buscheck, T.A.; Carlson, R.; Daily, W.; Latorre, V.R.; Lee, K et al.
Partner: UNT Libraries Government Documents Department