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Electromagnetic scattering by a two-dimensional inhomogeneity due to an oscillating magnetic dipole

Description: A numerical method of computing the electromagnetic response of two-dimensional earth models to an oscillating magnetic dipole is presented. The generalized electromagnetic variational integral is reduced to a sum of two-dimensional variational integrals by Fourier transformation. Discretization of each two-dimensional integral is carried out in terms of the secondary electric fields by using the finite element method. Following the variational principle, each harmonic integral is reduced to a set of simultaneous equations. From each set of electric field solutions obtained by solving the simultaneous equations, the secondary magnetic fields are computed numerically. After inversely Fourier transforming the secondary electric and magnetic fields, the total fields are finally obtained by adding the analytically calculated primary fields. Because of the systematically implied continuity of the electric field in the finite element solution, the given discontinuous conductivity is modified to a continuous one across internal boundaries. The quality of the solution for the horizontal magnetic dipole is found to be relatively poor compared to that for the vertical magnetic dipole. It is not possible to perform an absolute numerical check of the solution due to the lack of another independently developed solution against which it can be checked. As an alternative the solutions for two-dimensional models were compared to those for some elongated three-dimensional models whose cross sections correspond to the two-dimensional models. 23 figures, 1 table.
Date: September 1, 1978
Creator: Lee, K.H.
Partner: UNT Libraries Government Documents Department

Progress report on pre-test calculations for the large block test

Description: The U.S. Department of Energy`s (DOE) Yucca Mountain Site Characterization Project (YMP) is investigating the suitability of the Topopah Spring tuff in the thick vadose zone at Yucca Mountain, Nevada, as a host rock for permanent disposal of high-level radioactive waste. As part of the YMP, a group of field tests, referred to as the Large Block Test (LBT), will be conducted on a large electrically heated block of Topopah Spring tuff, isolated at Fran Ridge, Nevada Test Site. The block, which will be 3 x 3 m in horizontal dimensions and 4.5 m in height, will be heated by electrical heaters. The goals of the LBT axe to gain information on the coupled thermal-mechanical-hydrological-chemical processes active in the near-field environment of a repository; to provide field data for testing and calibrating models; and to help the development of measurement systems and techniques. This progress report presents results of on-going numerical modeling calculations carried out in support of the LBT design. An equivalent continuum model with an upper boundary temperature of 60{degrees}C was used to simulate the hydrothermal response of the block to heating over a one-year period. The total heating power was started at 1500 W and later reduced to maintain an approximately uniform temperature of 138-140{degrees}C. For a homogeneous bulk permeability case, the results show the formation of a distinct dry-out zone in and around the heater plane, and well-developed condensation zones above and below the heater plane. For a heterogeneous permeability distribution, the condensation zone above the heater plane was not well developed. This difference in results suggests that water saturation changes might be sensitive to changes in bulk permeability distribution. Rock temperatures were almost unaffected by permeability distribution. Heat flow was dominated by conduction. No liquid flow through the top of the block was predicted.
Date: January 20, 1995
Creator: Lee, K.H.
Partner: UNT Libraries Government Documents Department

Analysis of vadose zone tritium transport from an underground storage tank release using numerical modeling and geostatistics

Description: Numerical and geostatistical analyses show that the artificial smoothing effect of kriging removes high permeability flow paths from hydrogeologic data sets, reducing simulated contaminant transport rates in heterogeneous vadose zone systems. therefore, kriging alone is not recommended for estimating the spatial distribution of soil hydraulic properties for contaminant transport analysis at vadose zone sites. Vadose zone transport if modeled more effectively by combining kriging with stochastic simulation to better represent the high degree of spatial variability usually found in the hydraulic properties of field soils. However, kriging is a viable technique for estimating the initial mass distribution of contaminants in the subsurface.
Date: September 1, 1997
Creator: Lee, K.H.
Partner: UNT Libraries Government Documents Department

Second progress report on pre-test calculations for the large block test

Description: The US Department of Energy`s (DOE) Yucca Mountain Site Characterization Project (YMP) is investigating the suitability of the Topopah Spring tuff in the thick vadose zone at Yucca Mountain, Nevada, as a host rock for permanent disposal of high-level radioactive waste. As part of the YMP, a group of field tests, called the Large Block Test (LBT), will be conducted on a large electrically heated block of Topopah Spring tuff. The block will be heated by electrical heaters. The goals of the LBT are to gain information on the coupled thermal-mechanical-hydrological-chemical processes that will be active in the near-field environment of a repository; to provide field data for testing and calibrating models; and to help in the development of measurement systems and techniques. In this second progress report, we present results of the final set of numerical modeling calculations performed in support of the LBT design. The results include block temperatures and heat fluxes across the surfaces. The results are applied primarily to the design of guard heaters to enforce adiabatic conditions along the block walls. Conduction-only runs are adequate to estimate the thermal behavior of the system, because earlier calculations showed that heat transfer in the block is expected to be dominated by conduction. In addition, conduction-only runs can be made at substantially shorter execution times than full hydrothermal runs. We also run a two-dimensional, hydrothermal, discrete fracture model, with 200-{mu}m vertical fractures parallel to the heaters and occurring at a uniform spacing of 30 cm. The results show the development of distinct dryout and recondensation zones. The dryout zones are thickest at the fractures and thinnest in the matrix midway between the fractures.
Date: November 15, 1995
Creator: Lee, K.H.
Partner: UNT Libraries Government Documents Department

Multifrequency crosshole EM imaging for reservoir characterization. FY 1994 annual report

Description: Electrical conductivity of sedimentary rocks is controlled by the porosity, hydraulic permeability, temperature, saturation, and the pore fluid conductivity. These rock parameters play important roles in the development and production of hydrocarbon (petroleum and natural gas) resources. For these reasons, resistivity well logs have long been used by geologists and reservoir engineers in petroleum industries to map variations in pore fluid, to distinguish between rock types, and to determine completion intervals in wells. Reservoir simulation and process monitoring rely heavily on the physical characteristics of the reservoir model. Over a period of three years (1991-1993) there was an initial phase of crosshole EM technique development via an informal partnership between LLNL and LBL. Researchers developed field instrumentation to apply to oil field for monitoring EOR thermal processes. Specifically, a prototype single-frequency instrumentation was developed and with this system we have conducted field surveys in four separate locations. Theory and software were developed to interpret these data by providing subsurface images of the electrical conductivity. In spite of our initial success in developing practical EM techniques, we still had severe instrumentation limitations and shortcomings in interpretation for other than simple structures. The field equipment was designed to work only at a single frequency at a time and the transmitter must be opened to change frequencies. The equipment was also significantly noiser at higher frequencies. For high-resolution applications we need to take full advantage of the resolution inherent in the data. The development of a high-resolution subsurface conductivity imaging methods would have benefits far beyond the petroleum application. Such techniques would be very useful in environmental applications, mineral and geothermal exploration and for civil engineering applications.
Date: June 1, 1995
Creator: Lee, K.H.
Partner: UNT Libraries Government Documents Department

2-1/2-dimensional numerical solution for the electromagnetic scattering using a hybrid technique

Description: The use of the electromagnetic method for geothermal reservoir exploration and delineation was studied. A number of techniques were developed to provide high quality field data. The remaining problem of interpreting these data in regions of complex geologic structure was overcome by the development of a numerical solution based on the hybrid technique, making use of both the finite element and the integral equation techniques. The major improvement is in the computing speed. (ACR)
Date: March 1, 1983
Creator: Lee, K.H. & Morrison, H.F.
Partner: UNT Libraries Government Documents Department

A SOLUTION FOR TM-MODE PLANE WAVES INCIDENT ON A TWO-DIMENSIONAL INHOMOGENEITY

Description: A solution for the electromagnetic fields scattered from a two-dimensional inhomogeneity in a conducting half space has been obtained for an incident TM mode plane wave; the magnetic field is polarized parallel to the strike of the inhomogeneity. The approach has been to determine the scattering currents within the inhomogeneity using an integral equation for the electric fields. This solution is similar in concept to earlier studies of TE mode scattering from two-dimensional inhomogeneities, and it completes the analysis of the scattering of arbitrary plane waves using the integral equation approach. For simple bodies in the earth integral equation solution offers significant computational advantages over alternate finite element or finite difference methods of solution.
Date: March 1, 1980
Creator: Lee, K.H. & Morrision, H.F.
Partner: UNT Libraries Government Documents Department

Air-injection field tests to determine the effect of a heat cycle on the permeability of welded tuff

Description: As part of a series of prototype tests conducted in preparation for site characterization of the potential nuclear-waste repository site at Yucca Mountain, Nevada, air-injection tests were conducted in the welded tuffs in G-Tunnel at the Nevada Test Site. The objectives were to characterize the permeability of the highly fractured tuff around a horizontal heater emplacement borehole, and to determine the effect of a heating and cooling cycle on the rock-mass permeability. Air was injected into packed-off intervals along the heater borehole. The bulk permeability of the rock adjacent to the test interval and the aperture of fractures intersecting the interval were computed from the air-flow rate, temperature, and pressure at steady state. The bulk permeability of intervals along with borehole varied from a minimum of 0.08 D to a maximum of over 144 D and the equivalent parallel-plate apertures of fractures intersecting the borehole varied from 70 to 589 {mu}m. Higher permeabilities seemed to correlate spatially with the mapped fractures. The rock was then heated for a period of 6.5 months with an electrical-resistive heater installed in the borehole. After heating, the rock was allowed to cool down to the ambient temperature. The highest borehole wall temperature measured was 242{degree}C. Air injection tests were repeated following the heating and cooling cycle, and the results showed significant increases in bulk permeability ranging from 10 to 1830% along the borehole. 8 ref., 6 figs., 3 tabs.
Date: October 1, 1991
Creator: Lee, K.H. & Ueng, Tzou-Shin
Partner: UNT Libraries Government Documents Department

Field air injection tests to determine the effect of a heat cycle on the permeability of welded tuff

Description: As part of a series of prototype tests conducted in preparation for site characterization at Yucca Mountain, air-injection tests were conducted in the welded tuffs in G-Tunnel at the Nevada Test Site. The objectives were to characterize the permeability of the highly fractured tuff around a horizontal heater emplacement borehole, and to determine the effect of a heating and cooling cycle on the rock-mass permeability. Air was injected into packed-off intervals along the heater borehole. The bulk permeability of the rock adjacent to the test interval was computed from the air-flow rate, temperature, and pressure at steady state. The permeability varied from a minimum of 0.08 D to a maximum of over 144 D. Higher permeabilities seemed to correlate spatially with the mapped fractures. The rock was then heated for a period of 6.5 months with an electrical-resistive heater installed in the borehole. After heating, the rock was allowed to cool down to the ambient temperature. the highest borehole wall temperature measured was 242{degrees}C. Air injection tests were repeated following the heating and cooling cycle, and the results showed significant increases in bulk permeability ranging from 10 to 1830% along the borehole.
Date: October 1, 1991
Creator: Lee, K.H. & Ueng, Tzou-Shin
Partner: UNT Libraries Government Documents Department

Catalogue of magnetotelluric apparent resistivity pseudo-sections over two-dimensional models

Description: As part of the program on geothermal exploration technique evaluation and development, the magnetotelluric method was evaluated in a Basin and Range environment (Beyer et al., 1976). One developement from this effort is an improved two-dimensional magnetotelluric resistivity computer algorithm, called TEM, capable of calculating the transverse electric (TE) and transverse magnetic (TM) soundings over an arbitrary two-dimensional body. Using this program a series of magnetotelluric pseudosections was generated over a set of two-dimensional models which in a gross sense typify structure and resistivities of northern Nevada. This catalogue may be used for qualitative evaluation of existing MT data or for planning future surveys.
Date: August 1, 1978
Creator: Lee, K. H.; Labson, V.; Wilt, M. & Goldstein, N.
Partner: UNT Libraries Government Documents Department

Magnetotelluric studies in Grass Valley, Nevada

Description: A program of detailed magnetotelluric soundings was initiated in 1974 in Green Valley, Nevada, as part of the Lawrence Berkeley Laboratory's major study of techniques for geothermal exploration in north central Nevada. The magnetotelluric program had three main goals; the determination of resistivity distribution at depths greater than that conveniently measured with other techniques; a comparison of the interpreted resistivity at shallow depth with the results of the other techniques; and the evaluation of the SQUID or Josephson effect magnetometer in practical field surveys. In addition, new numerical models were developed so that interpretation could be carried out in terms of fairly complex two-dimensional models.
Date: January 1, 1979
Creator: Morrison, H.F.; Lee, K.H.; Oppliger, G. & Dey, A.
Partner: UNT Libraries Government Documents Department

Measurements of electrical conductivity for characterizing and monitoring nuclear waste repositories

Description: The detection of major fractures is one topic of this study but another equally important problem is to develop quantitative relationships between large scale resistivity and fracture systems in rock. There has been very little work done on this central issue. Empirical relations between resistivity and porosity have been derived on the basis of laboratory samples or from well logging, but there are no comparable 'laws' for rock masses with major fracture or joint patterns. Hydrologic models for such rocks have been recently been derived but the corresponding resistivity models have not been attempted. Resistivity due to fracture distributions with preferred orientation could be determined with such models, as could quantitative interpretation of changes as fracture aperature varies with load. This study is not only important for the assessment of a repository site, but has far ranging implications in reservoir studies for oil, gas, and geothermal resources. The electrical conductivity can be measured in two ways. Current can be injected into the ground through pairs of electrodes and corresponding voltage drops can be measured in the vicinity with other pairs of electrodes. The electrical conductivity can also be measured inductively. Instead of injecting current into the ground as described in the dc resistivity method, currents can be induced to flow by a changing magnetic field. In these inductive or electromagnetic (em) methods the interpretation depends both on transmitter-receiver geometry and frequency of operation. In principle the interpretation should be more definitive than with the dc resistivity methods. Rigorous confirmation of this statement in inhomogeneous media awaits the development of generalized inversion techniques for em methods.
Date: November 1, 1986
Creator: Morrison, H.F.; Becker, A. & Lee, K.H.
Partner: UNT Libraries Government Documents Department

High-frequency electric field measurement using a toroidal antenna

Description: In this paper the author describes an innovative method of measuring high-frequency electric fields using a toroid. For typical geophysical applications the new sensor will detect electric fields for a wide range of spectrum starting from 1.0 MHz. This window, in particular the lower frequency range between 1.0 to 100 MHz, has not been used for existing electromagnetic or radar systems to detect small objects in the upper few meters of the ground. Ground penetrating radar (GPR) can be used successfully in this depth range if the ground is resistive but most soils are, in fact, conductive (0.01 to 1.0 S/m) rendering GPR inefficient. Other factors controlling the resolution of GPR system for small objects is the spatial averaging inherent in the electric dipole antenna and the scattering caused by soil inhomogeneities of dimensions comparable to the wavelength (and antenna size). For maximum resolution it is desirable to use the highest frequencies but the scattering is large and target identification is poor. Time-varying magnetic fields induce an emf (voltage) in a toroid. The electric field at the center of the toroid is shown to be linearly related to this induced voltage. By measuring the voltage across a toroid one can easily and accurately determine the electric field. The new sensor will greatly simplify the cumbersome procedure involved with GPR measurements with its center frequency less than 100 MHz. The overall size of the toroidal sensor can be as small as a few inches. It is this size advantage that will not only allow easy fabrication and deployment of multi-component devices either on the surface or in a borehole, but it will render greatly improved resolution over conventional systems.
Date: January 1, 1997
Creator: Lee, K.H.
Partner: UNT Libraries Government Documents Department

Electromagnetic method for analyzing the property of steel casing

Description: It has been shown that electromagnetic (EM) imaging, in particular in borehole applications, can be effective in characterizing and monitoring subsurface processes involved in improved oil recovery operations and production management. In this report the authors present an innovative EM method for extracting information about a steel casing in terms of its electrical conductivity, magnetic permeability, and the casing thickness. The method is based on accurate evaluation of magnetic fields near the transmitting loop in a steel-cased borehole, and the least squares inversion of thus measured data. The need to make measurements close to the source stems from the two related considerations. One reason is that by making measurements close to the transmitter one can keep the formation response from entering the measurement to a minimum. The other reason concerns with the practical consideration involved in fabricating a borehole tool. The measurement accuracy in terms of PPM to the primary field can best be achieved when the transmitter and receiver are close to each other. To facilitate this requirement one can consider a single loop acting as the source and the receiver operating in time domain, or a closely coupled frequency-domain system with the source-receiver separation of just a few inches apart. Results are discussed.
Date: February 1, 1998
Creator: Lee, K.H.; Kim, H.J. & Song, Y.
Partner: UNT Libraries Government Documents Department

Electromagnetic Fields Due to a Loop Current in a CasedBorehole Surrounded by Uniform Whole Space

Description: Precise evaluation of electromagnetic (EM) response in steel-cased borehole is an essential first step towards developing techniques for casing parameter evaluation, which would ultimately help evaluating the formation response. In this report we demonstrate a numerical scheme for accurately computing EM responses in cased borehole environment. For improved numerical accuracy we use explicit representations of the electromagnetic spectra inside the borehole, in the casing, and in the formation. Instead of conventional Hankel transform, FFT is used to improve the numerical accuracy. The FFT approach allows us to compute fields at positions very close to the source loop, including the center of the transmitter loop.
Date: January 1998
Creator: Lee, K. H. & Song, Y.
Partner: UNT Libraries Government Documents Department

Controlled-source magnetotellurics: source effects

Description: In this paper we evaluate the CSMT impedance in the wavenumber domain, and compare the result with the full EM impedance obtained from the exact solution over the layered earth. Preliminary results show that we can find a pair of wavenumbers that reproduces the full EM impedance over the frequency range affected by source effects. This observation suggests that it is now possible to obtain the electrical resistivity using the low-frequency EM impedance data that can be represented by a pair of wavenumbers, thereby greatly simplifying the computational requirements. The process will involve a non-linear inversion of near-source impedance data for a pair of wavenumbers and a layered-earth resistivity structure.
Date: April 1, 1999
Creator: Smith, T. & Lee, K.H.
Partner: UNT Libraries Government Documents Department

Subsurface electromagnetic measurement through steel casing

Description: Numerical calculations show that useful information can be obtained in an electromagnetic crosswell survey where one of the wells is cased in steel. Our simple model is based on the assumption of an infinitely long uniform casing embedded in a homogeneous full space. Nevertheless the results indicate that if the pipe characteristics are independently known then the formation signal can be accurately recovered. This is best done at a single frequency where the pipe attenuation is modest. In fact we show that the optimal frequency for formation signal recovery is defined mainly by the pipe parameters and is largely independent of the formation conductivity.
Date: November 1998
Creator: Becker, A. B.; Wang, B. & Lee, K. H.
Partner: UNT Libraries Government Documents Department

Application of geophysical methods for fracture characterization

Description: One of the most crucial needs in the design and implementation of an underground waste isolation facility is a reliable method for the detection and characterization of fractures in zones away from boreholes or subsurface workings. Geophysical methods may represent a solution to this problem. If fractures represent anomalies in the elastic properties or conductive properties of the rocks, then the seismic and electrical techniques may be useful in detecting and characterizing fracture properties. 7 refs., 3 figs.
Date: January 1, 1990
Creator: Lee, K.H.; Majer, E.L.; McEvilly, T.V. & Morrison, H.F.
Partner: UNT Libraries Government Documents Department

High frequency electromagnetic impedance measurements for characterization, monitoring and verification efforts. 1998 annual progress report

Description: 'Non-invasive, high-resolution imaging of the shallow subsurface is needed for delineation of buried waste, detection of unexploded ordinance, verification and monitoring of containment structures, and other environmental applications. Electromagnetic measurements at frequencies between 1 and 100 MHz are important for such applications, because the induction number of many targets is small due, and the ability to determine the dielectric permittivity in addition to electrical conductivity of the subsurface is possible. Earlier workers were successful in developing systems for detecting anomalous areas, but no quantifiable information was accurately determined. For high resolution imaging, accurate measurements are necessary so the field data can be mapped into the space of the subsurface parameters. The authors are developing a non-invasive method for accurately imaging the electrical conductivity and dielectric permittivity of the shallow subsurface using the plane wave impedance approach, known as the magnetotelluric (MT) method at low frequencies. Electric and magnetic sensors are being tested in a known area against theoretical predictions, thereby insuring that the data collected with the high-frequency impedance (HFI) system will support high-resolution, multi-dimensional imaging techniques. The summary of the work to date is divided into three sections: equipment procurement, instrumentation, and theoretical developments. For most earth materials, the frequency range from 1 to 100 MHz encompasses a very difficult transition zone between the wave propagation of displacement currents and the diffusive behavior of conduction currents. Test equipment, such as signal generators and amplifiers, does not cover the entire range except at great expense. Hence the authors have divided the range of investigation into three sub-ranges: 1--10 MHz, 10--30 MHz, and 30--100 MHz. Results to date are in the lowest frequency range of 1--10 MHz. Even though conduction currents dominate in this range, as in traditional electromagnetic exploration methods, little work has been done by the geophysical community above ...
Date: June 1, 1998
Creator: Lee, K.H.; Pellerin, L. & Becker, A.
Partner: UNT Libraries Government Documents Department

Electrical and electromagnetic methods for reservoir description and process monitoring. Annual report, October 1, 1992--September 30, 1993

Description: It is well known that electrical conductivity of rock is closely related to the porosity, hydrologic permeability, saturation, and the type of fluid in it. These rock parameters play important roles in the development and production of hydrocarbon (petroleum and natural gas) resources. For these reasons, resistivity well logs have long been used by geologists and reservoir engineers in petroleum industries to map variations in pore fluid, to distinguish between rock types, and to determine completion intervals in wells. Reservoir simulation and process monitoring rely heavily on the physical characteristics of the reservoir model. At the beginning of FY-91 a coordinated electrical and electromagnetic (EM) geophysical research program for petroleum reservoir characterization and process monitoring was initiated. Parties involved in this program include Lawrence Berkeley Laboratory (LBL), Lawrence Livermore Laboratory (LLNL), Sandia National Laboratory (SNL), and University of California at Berkeley (UCB). The overall objectives of the program were: to integrate research funded by DOE for hydrocarbon recovery into a focused effort to demonstrate the technology in the shortest time with the least cost; to assure industry acceptance of the technology developed by having industry involvement in the planning, implementation, and funding of the research; to focus the research on real world problems that have the potential for solution in the near term with significant energy payoff. Specific research activities conducted have been in the following areas: (1) EM modeling development; (2) data interpretation methods development; (3) hardware and instrumentation development; (4) EOR and reservoir characterization; (5) controlled field experiments. The primary focus of these activities was in the development of reliable inversion and imaging schemes that could yield conductivity distributions from measured electrical and EM field data.
Date: July 1, 1995
Creator: Morrison, H.F.; Lee, K.H. & Becker, A.
Partner: UNT Libraries Government Documents Department

Electrical resistivity for detecting subsurface non-aqueous phase liquids: A progress report

Description: Soils and groundwater have been contaminated by hazardous substances at many places in the United States and many other countries. The contaminants are commonly either petroleum products or industrial solvents with very low solubility in water. These contaminants are usually called non-aqueous phase liquids (NAPLs). The cost of cleaning up the affected sites in the United States is estimated to be of the order of 100 billion dollars. In spite of the expenditure of several billion dollars during the last 15 years, to date, very few, if any major contaminated site has been restored. The presence of NAPL pools in the subsurface is believed to be the main cause for the failure of previous cleanup activities. Due to their relatively low water solubility, and depending on their volume, it takes tens or even hundreds of years to deplete the NAPL sources if they are not removed from the subsurface. The intrinsic electrical resistivity of most NAPLs is typically in the range of 10{sup 7} to 10{sup 12}{Omega}-m, which is several orders of magnitude higher than that of groundwater containing dissolved solids (usually in the range of a few {Omega}-m to a few thousand {Omega}-m). Although a dry soil is very resistive, the electrical resistivity of a wet soil is on the order of 100 {Omega}-m and is dependent on the extent of water saturation. For a given soil, the electrical resistivity increases with decrease of water saturation. Therefore, if part of the pore water is replaced by a NAPL, the electrical resistivity will increase. At many NAPL sites, both the vadose and phreatic zones can be partially occupied by NAPL pools. It is the great contrast in electrical resistivity between the NAPLs and groundwater that may render the method to be effective in detecting subsurface NAPLs at contaminated sites. The ...
Date: June 1, 1995
Creator: Lee, K.H.; Shan, C. & Javandel, I.
Partner: UNT Libraries Government Documents Department

Time-Resolved Sequence Analysis on High Density Fiberoptic DNA Probe

Description: A universal array format has been developed in which all possible n-mers of a particular oligonucleotide sequence can be represented. The ability to determine the sequence of the probes at every position in the array should enable unbiased gene expression as well as arrays for de novo sequencing.
Date: November 19, 2002
Creator: Walt, D. R. & Lee, K-H
Partner: UNT Libraries Government Documents Department

NUFT USNT Thermal Input Parameters

Description: This document describes the thermal input parameters required to run the USNT module of the NUFT code. The USNT module handles multi-component transport of multiple fluid phases and heat through porous and fractured media. The thermal input parameters required to model the heat transport by conduction, convection, and radiation are summarized, and the relevant mixing rules outlined. This is followed by a table that describes the thermal input parameters in a typical NUFT input file used for YMP thermal-hydrological calculations. Most of the material presented here is summarized from the user's manual of the USNT module of NUFT (Nitao, 2000).
Date: September 1, 2000
Creator: Lee, K.H.
Partner: UNT Libraries Government Documents Department

Cross-borehole and surface-to-borehole electromagnetic induction for reservoir characterization

Description: Audio-frequency cross-borehole and surface-to-borehole electromagnetics (EM) are interesting alternatives to existing techniques for petroleum reservoir characterization and monitoring. With these methods signals may be propagated several hundreds of meters through typical sand/shale reservoirs and data may be collected at high accuracy with a high sensitivity to the subsurface resistivity distribution. Field systems for cross-borehole and surface-to-borehole EM measurements have been designed and built by Lawrence Livermore and Lawrence Berkeley Laboratories for reservoir evaluation and monitoring. The cross-borehole system utilizes vertical axis induction coil antennas for transmission and detection of sinusoidal signals. Data are collected in profiles with the source coil moving continuously while its signal is detected by a stationary receiver coil located in a separate well. Subsequent profiles are collected using a different receiver depth and the same transmitter span until a suite of profiles is obtained that cover the desired interval in the borehole. The surface-to-borehole system uses a large diameter surface loop transmitter and a vertical axis borehole receiver. Due to its high signal strength this system operates using a sweep frequency transmitter waveform so that data may be simultaneously collected over several decades of frequency. Surface-to-borehole profiles are equally repeatable and although this data is less sensitive than cross-borehole EM, it can be fit to a resistivity section consistent with the borehole log. 8 refs., 14 figs.
Date: August 1, 1991
Creator: Wilt, M.J.; Morrison, H.F.; Becker, A. & Lee, K.H.
Partner: UNT Libraries Government Documents Department