119 documents found in 237ms
# 1
KTB, WG Geophysics
Abstract: In the laboratory, the gamma radiation is measured by a sodium iodtite (NaI) scintillation detector (cores and cuttings) and by a germanium (Ge) semiconductor detector (cuttings). The cuttings are measured in air tight Marinelli-beakers with a volume of 250 cm3. For the core measurements a special, automatically operating equipment with three NaI detectors is used. A description of this apparatus is given in Wienand et al. (1989). The principle of measurements with the Ge-detector is described by Bücker et al. (1991).The measured spectra are calibrated by a standard of Luvarovite (NIM-L, South African Bureau of Standards). The influence of the local terrestrial radiation on the measurements has been corrected. Especially for the core measurements a calibration procedure has been performed for geometric corrections (core diameter and length). In general, a measuring time of 12 h for the NaI-detector and 2 h for the Ge-detector was chosen.
# 2
KTB, WG Geophysics
Abstract: The thermal conductivity on cores is measured in two steps (see Pribnow 1994). First, one face end of the core is sawed and polished. The half space line source is pressed against this preparated face (without further contact medium like water) by a computerized device. The position of the heat source is varied in 15 degree intervals around one semicircle. At each position, 3 repeating measurements are performed. The line source azimuth of the lowest measured thermal conductivity is the strike of the foliation plane. On the other hand, the thermal conductivity is maximal parallel to that direction. This apparent paradox can be explained by the experimental method, because the measurement plane is perpendicular to the orientation of the line source (Pribnow 1994).In a second step a calotte plane perpendicular to the strike of foliation is prepared. A second series of thermal conductivity measurements in 15 degree intervals ...
# 3
KTB, WG Geophysics
Abstract: The thermal conductivity on cores is measured in two steps (see Pribnow 1994). First, one face end of the core is sawed and polished. The half space line source is pressed against this preparated face (without further contact medium like water) by a computerized device. The position of the heat source is varied in 15 degree intervals around one semicircle. At each position, 3 repeating measurements are performed. The line source azimuth of the lowest measured thermal conductivity is the strike of the foliation plane. On the other hand, the thermal conductivity is maximal parallel to that direction. This apparent paradox can be explained by the experimental method, because the measurement plane is perpendicular to the orientation of the line source (Pribnow 1994).In a second step a calotte plane perpendicular to the strike of foliation is prepared. A second series of thermal conductivity measurements in 15 degree intervals ...
# 4
KTB, WG Geophysics
Abstract: In general, four-electrode devices are used to measure the resistivity on original (unprepared) cores and on mini cores drilled from these original cores. The in-phase and the out-of-phase signal is measured and therefore the complex resistivity is determined. All measurements are performed under surface conditions (room temperature and atmospheric pressure). Four point like electrodes are situated at the core surface along a semicircle in a plane perpendicular to the core axis. The two current electrodes are opposite to each other. The electrodes are in contact to the sample by a porous plastic material soaked with 0.1 molar NaCl solution. Voltage and current is measured by a lock-in-amplifier at 120 Hz frequency. Due to high contact resistances, only the magnitude of complex resistivity is used. By computer controlled rotating of the core and moving of the electrode arrangement along the cores z axis, resistivity as a function of azimuth and length is measured.
# 5
KTB, WG Geophysics
Abstract: In the KTB field laboratory, porosity, internal surface and permeability were determined on identical mini cores with 25.4 mm in diameter and approximately 50 mm in length. These samples were drilled either axial or radial with respect to the drill core, or parallel or perpendicular with respect to the foliation. In the KTB field laboratory, the stationary sArcy method was used with nitrogen gas as the streaming medium. The measurements were made at a constant confining pressure of 5 MPa to 6.5 MPa. The nitrogen pressure gradient was up to 2 MPa at the inflow side minus atmospheric pressure at the outflow side of the sample. Because of the low pore pressures during the measurements (max 2 MPa) the data had to be corrected for the effect of gas friction along the matrix wall, the so called Klinkenberg effect (Huenges et al. 1990). Further details, regarding equipment and evaluation are given by Pusch et al. (1986).
# 6
KTB, WG Geophysics
Abstract: In general, four-electrode devices are used to measure the resistivity on original (unprepared) cores and on mini cores drilled from these original cores. The in-phase and the out-of-phase signal is measured and therefore the complex resistivity is determined. All measurements are performed under surface conditions (room temperature and atmospheric pressure). Mini cores of 25.4 mm diameter and approximately 50 mm length are drilled from original cores. Anisotropy information is obtained by different core orientations. The complex resitivity is measured in an 4-electrode elctrolytic cell by use of a lock-in-amplifier. The applied frequency ranges from 0.5 Hz to 120 kHz. The samples are first evacuated and back-saturated with destilled water. In this case, mainly sigmas and sigmam contribute to the rock resistivity. A second cycle of evacuating and back-saturating with 0.1 molar NaCl solution leads to sigmav (Rauen 1994).
# 7
KTB, WG Geophysics
Abstract: Ultrasonic wave propagation through core samples is studied in a water tank to insure good signal transmission between transducer, rock specimen and receiver and to avoid time - consuming mechanical preparations. A specifically designed instrumentation was used, which allows to measure the radial p-wave velocity in the plane normal to the core axis and, if the core sample is long enough, also the axial p- and s-wave velocities by common mid-point (CMP) refraction experiments, with water as the upper and the core as the lower layer. By rotating the cores, all measurements are performed for variable azimuths. Computer control of all mechanical and electronical operations, digital 10-bit data aquisition, signal stacking and interactive seismogram evaluation are essential features of the system. Data are available from the few cores taken below 4000 m. The investigations were carried out on the longest core sample of each cored interval (16 specimens).
# 8
KTB, WG Geophysics
Abstract: The magnetic susceptibility is measured by an inductive AC device (BARTINGTON). The sample is placed inside a coil which generates an alternating magnetic field. The applied frequency is 460 Hz (cuttings, 25.4 mm mini cores), 565 Hz (cores) or 1470 Hz (15 mm mini cores) respectively. A shift in the oscillator frequency is a measure for the magnetic susceptibility of the sample. The applied magnetic field strength is 80 A/m (RMS) and appr. 2 times the total earth magnetic field strength in the KTB area (=38 A/m). The measurement field is lower than the field which is necessary for magnetic saturation and allows therefore to measure the initial susceptibility. The used sensors are insensitive to the electrical conductivity of the samples. Except the determination of the temperature dependent susceptibility, all measurements are done under surface conditions (room temperature and atmospheric pressure).
# 9
KTB, WG Geophysics
Abstract: Ultrasonic wave propagation through core samples is studied in a water tank to insure good signal transmission between transducer, rock specimen and receiver and to avoid time - consuming mechanical preparations. A specifically designed instrumentation was used, which allows to measure the radial p-wave velocity in the plane normal to the core axis and, if the core sample is long enough, also the axial p- and s-wave velocities by common mid-point (CMP) refraction experiments, with water as the upper and the core as the lower layer. By rotating the cores, all measurements are performed for variable azimuths. Computer control of all mechanical and electronical operations, digital 10-bit data aquisition, signal stacking and interactive seismogram evaluation are essential features of the system. Data are available from the few cores taken below 4000 m. The investigations were carried out on the longest core sample of each cored interval (16 specimens).
# 10
KTB, WG Geophysics
Abstract: The magnetic susceptibility is measured by an inductive AC device (BARTINGTON). The sample is placed inside a coil which generates an alternating magnetic field. The applied frequency is 460 Hz (cuttings, 25.4 mm mini cores), 565 Hz (cores) or 1470 Hz (15 mm mini cores) respectively. A shift in the oscillator frequency is a measure for the magnetic susceptibility of the sample. The applied magnetic field strength is 80 A/m (RMS) and appr. 2 times the total earth magnetic field strength in the KTB area (=38 A/m). The measurement field is lower than the field which is necessary for magnetic saturation and allows therefore to measure the initial susceptibility. The used sensors are insensitive to the electrical conductivity of the samples. Except the determination of the temperature dependent susceptibility, all measurements are done under surface conditions (room temperature and atmospheric pressure).
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