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Ground penetrating radar surveys of peatlands for oilfield pipelines in Canada
362A
SITE INVESTIGATIONS:BOREHOLES
magnetic field intensity and vector potential. (English summary)
968200
Research on determination of surface area of ore body by limiting electric current strength of polarization curve reaction (in Chinese) Huang Xingwan, Kuangwu YanshilJournal of Mineralogy & Petrology, 15(3), 1995, pp 76-81. The principles of determination of the surface area of an orebody by polarization curve reaction limiting electric current strength are introduced. Experimental method and results obtained on monomineralic and polymineralic deposits are presented. (English summary)
968201 A numerical evaluation of electromagnetic methods in geothermal exploration L. Pellerin, J. M. Johnston & G. W. Hohmann, Geophysics, 61(l), 1996, pp 121-130. The size and low resistivity of the clay cap associated with a geothermal system create a target well suited for electromagnetic (EM) methods and also make electrical detection of the underlying geothermal reservoir a challenge. Using 3-D numerical models, four EM techniques are evaluated for use in geothermal exploration: magnetotellurics (MT), controlled-source audio magnetotellurics (CSAMT), long-offset time-domain EM (LGTEM), and short-offset time-domain EM (TEM). The results show that all of these techniques can delineate the clay cap, but none can be said to unequivocally direct the reservoir. However, the EM anomaly from a deep, conductive reservoir overlain by a larger, more conductive clay cap is caused by the presence of the electric charge of conductivity boundaries rather than electromagnetic induction. This means that, for detection of the reservoir, methods such as MT’, which rely on electric field measurements, are superior to those where only the magnetic field is measured. (from Authors)
968202 A new method for geoelectrical investigations underwater Ti t;umgartner, Geophysical Prospecting, 44(l), 1996, pp - . A new electrical method is proposed for determining the apparent resistivity of multi-earth layers located underwater. The method is based on direct current geoelectric sounding principles. A layered earth model is used to simulate the stratigraphic target. The measurement array is of pole-pole type; it is located underwater and is orientated vertically. The calculated apparent resistivity shows a substantial quality increase in the measured signal caused by the underwater targets, from which little or no response is measured using conventional surface electrode methods. A case study is presented, where field surveys carried out on Lake Geneva were interpreted using the calculated apparent resistivity master-curves. (from Author)
968203
Msgnetic susceptibility and beavy metals in the surroundings of the VSZ Kosice dry refuse beap 0. Durxa, Acta Universitatis Carolinae - Geologica, 38(l), 1994, pp 65-71. A new nonconventional way of utilizing magnetic susceptibility - a soil kappa-measurement - was applied to the heavy metals studv in the surroundings of the VSZ Kosice drv refuse heap. HeaG metals contents i’l the soil generally co&pond to magnetic susceptibility values. These values decrease with their distance from the refuse heap. (author)
968204 Regional geophysical studies applied to mineral resource assessment of the Hailey 1” x 2” quadrangle and the western part of the Idaho Falls 1” x 2” quadrangle, southcentral Idaho M. D. Kleinkopf, A. E. McCafferty & G. A. Abrams, US Geological Survey Bulletin, 2064-A-R, 1995, pp Rl-R12. Interpretations of aeromagnetic and gravity anomaly data for the Hailey 1” x 2” quadrangle and the western part of tbe Idaho Falls 1” x 2” quadrangle south-central Idaho were used to delineate buried intrusive complexes, major geologic structures, and areas of possible volcanic subsidence that may relate to hydrothermally altered and mineralized areas. Interpretation of the aeromagnetic and gravity anomaly data suggests a number of areas for follow-up studies to identify possible new mineral deposits. These include: 1) areas interpreted to be underlain by igneous intrusive rocks, 2) northeast-trending belts of high magnetic gradient reflecting possible faulting parallel with the Trans-Challis fault system, 3) areas of crossfaulting along the proposed Atlantic Great Rift shear zones, and 4) aeromagnetic and gray anomalies that correlate with geochemical anomalies. (from Authors) 968205 Ground penetrating radar surveys of peatlands for oilfield pipelines in Canada H. M. Jol & D. G. Smith, Journal of Applied Geophysics, 34(2), 1995, pp 109-123. Placement of buried pipelines in thick peat deposits is difficult because of the low bearing strength and high water content of the material for support of heavy construction equipment. Field experiments were conducted in the Mitsue oilfield located immediately southeast of Lesser Slave Lake in northcentral Alberta Province, Canada. Surficial deposits consist of Holocene, linear, sandy beach ridges separated by peatlands underlain by sand. Several GPR surveys assessed the thickness of the peat along two oil pipeline right-of-ways. Results show the peat-sand contact as irregular and undulating, ranging from 0 to 3.7 m deep. Each survey, 460 and 550 m long, was completed in two hours. Such results from 1 m station spacings can considerably reduce the uncertainties in planning and placement of oil, gas, and water pipelines crossing peatlands. (from Authors) 968206 A study of energy absorption buildup factors in tive different soils G. S. Brar & G. S. Mudahar, Nuclear Geophysics, 9(6), 1995, pp 629-641. An interpolation method has been used to generate energy absorption geometric-progression fitting parameters and buildup factors for five different types of soil in the energy range 0.015-15.0 MeV up to a penetration depth of 40 mean free paths. The generated buildup factor data has been studied as a function of the incident photon energy and the effective atomic number of the soils. (Authors)
Borehole and core logging 968207 Influence of inductive effect on measurements of resistivity through casing A. A. Kaufman, A. D. Karinsky 8c W. E. Wightman, Geophysics, 61(l), 1996, pp 34-42. A conventional theory of electrical logging through casing, using an altematina field. is develooed. Eauations for the elect& field and iis derivative on-the borehole axis are derived and their dependence on the resistivity of the medium and parameters of the casing are studied. It is established that within the low-frequency part of the spectrum, formation resistivity can be determined using the theory of the transmission line. Measurements within the intermediate range of frequencies also give information about the forma-
SITE INVESTIGATIONS:BOREHOLES
magnetic field intensity and vector potential. (English summary)
968200
Research on determination of surface area of ore body by limiting electric current strength of polarization curve reaction (in Chinese) Huang Xingwan, Kuangwu YanshilJournal of Mineralogy & Petrology, 15(3), 1995, pp 76-81. The principles of determination of the surface area of an orebody by polarization curve reaction limiting electric current strength are introduced. Experimental method and results obtained on monomineralic and polymineralic deposits are presented. (English summary)
968201 A numerical evaluation of electromagnetic methods in geothermal exploration L. Pellerin, J. M. Johnston & G. W. Hohmann, Geophysics, 61(l), 1996, pp 121-130. The size and low resistivity of the clay cap associated with a geothermal system create a target well suited for electromagnetic (EM) methods and also make electrical detection of the underlying geothermal reservoir a challenge. Using 3-D numerical models, four EM techniques are evaluated for use in geothermal exploration: magnetotellurics (MT), controlled-source audio magnetotellurics (CSAMT), long-offset time-domain EM (LGTEM), and short-offset time-domain EM (TEM). The results show that all of these techniques can delineate the clay cap, but none can be said to unequivocally direct the reservoir. However, the EM anomaly from a deep, conductive reservoir overlain by a larger, more conductive clay cap is caused by the presence of the electric charge of conductivity boundaries rather than electromagnetic induction. This means that, for detection of the reservoir, methods such as MT’, which rely on electric field measurements, are superior to those where only the magnetic field is measured. (from Authors)
968202 A new method for geoelectrical investigations underwater Ti t;umgartner, Geophysical Prospecting, 44(l), 1996, pp - . A new electrical method is proposed for determining the apparent resistivity of multi-earth layers located underwater. The method is based on direct current geoelectric sounding principles. A layered earth model is used to simulate the stratigraphic target. The measurement array is of pole-pole type; it is located underwater and is orientated vertically. The calculated apparent resistivity shows a substantial quality increase in the measured signal caused by the underwater targets, from which little or no response is measured using conventional surface electrode methods. A case study is presented, where field surveys carried out on Lake Geneva were interpreted using the calculated apparent resistivity master-curves. (from Author)
968203
Msgnetic susceptibility and beavy metals in the surroundings of the VSZ Kosice dry refuse beap 0. Durxa, Acta Universitatis Carolinae - Geologica, 38(l), 1994, pp 65-71. A new nonconventional way of utilizing magnetic susceptibility - a soil kappa-measurement - was applied to the heavy metals studv in the surroundings of the VSZ Kosice drv refuse heap. HeaG metals contents i’l the soil generally co&pond to magnetic susceptibility values. These values decrease with their distance from the refuse heap. (author)
968204 Regional geophysical studies applied to mineral resource assessment of the Hailey 1” x 2” quadrangle and the western part of the Idaho Falls 1” x 2” quadrangle, southcentral Idaho M. D. Kleinkopf, A. E. McCafferty & G. A. Abrams, US Geological Survey Bulletin, 2064-A-R, 1995, pp Rl-R12. Interpretations of aeromagnetic and gravity anomaly data for the Hailey 1” x 2” quadrangle and the western part of tbe Idaho Falls 1” x 2” quadrangle south-central Idaho were used to delineate buried intrusive complexes, major geologic structures, and areas of possible volcanic subsidence that may relate to hydrothermally altered and mineralized areas. Interpretation of the aeromagnetic and gravity anomaly data suggests a number of areas for follow-up studies to identify possible new mineral deposits. These include: 1) areas interpreted to be underlain by igneous intrusive rocks, 2) northeast-trending belts of high magnetic gradient reflecting possible faulting parallel with the Trans-Challis fault system, 3) areas of crossfaulting along the proposed Atlantic Great Rift shear zones, and 4) aeromagnetic and gray anomalies that correlate with geochemical anomalies. (from Authors) 968205 Ground penetrating radar surveys of peatlands for oilfield pipelines in Canada H. M. Jol & D. G. Smith, Journal of Applied Geophysics, 34(2), 1995, pp 109-123. Placement of buried pipelines in thick peat deposits is difficult because of the low bearing strength and high water content of the material for support of heavy construction equipment. Field experiments were conducted in the Mitsue oilfield located immediately southeast of Lesser Slave Lake in northcentral Alberta Province, Canada. Surficial deposits consist of Holocene, linear, sandy beach ridges separated by peatlands underlain by sand. Several GPR surveys assessed the thickness of the peat along two oil pipeline right-of-ways. Results show the peat-sand contact as irregular and undulating, ranging from 0 to 3.7 m deep. Each survey, 460 and 550 m long, was completed in two hours. Such results from 1 m station spacings can considerably reduce the uncertainties in planning and placement of oil, gas, and water pipelines crossing peatlands. (from Authors) 968206 A study of energy absorption buildup factors in tive different soils G. S. Brar & G. S. Mudahar, Nuclear Geophysics, 9(6), 1995, pp 629-641. An interpolation method has been used to generate energy absorption geometric-progression fitting parameters and buildup factors for five different types of soil in the energy range 0.015-15.0 MeV up to a penetration depth of 40 mean free paths. The generated buildup factor data has been studied as a function of the incident photon energy and the effective atomic number of the soils. (Authors)
Borehole and core logging 968207 Influence of inductive effect on measurements of resistivity through casing A. A. Kaufman, A. D. Karinsky 8c W. E. Wightman, Geophysics, 61(l), 1996, pp 34-42. A conventional theory of electrical logging through casing, using an altematina field. is develooed. Eauations for the elect& field and iis derivative on-the borehole axis are derived and their dependence on the resistivity of the medium and parameters of the casing are studied. It is established that within the low-frequency part of the spectrum, formation resistivity can be determined using the theory of the transmission line. Measurements within the intermediate range of frequencies also give information about the forma-