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The target of this study is to correlate the logging data with the lithological and structural characteristics of the drilled volcanic sequences; in particular to extract information which are important to better understand alteration processes as well as the hydrogeological and hydrogeochemical situation. The specific targets of this study are: core-log comparisons and detailed reconstruction of the lithological profile with individual lithological units , evaluation of the BHTV data with regard to stereoscopic analysis of structural elements, calculation of porosity profiles using resistivity and sonic logs, determination of variations of petrophysical in-situ parameter with depth(increasing age); in particular mapping the distribution and extent of alteration and possible fluid path way zones. All log analysis will be closely correlated with petrographical and geochemical core analysis.
The target of this study is to correlate the logging data with the lithological and structural characteristics of the drilled volcanic sequences; in particular to extract information which are important to better understand alteration processes as well as the hydrogeological and hydrogeochemical situation. The specific targets of this study are: core-log comparisons and detailed reconstruction of the lithological profile with individual lithological units , evaluation of the BHTV data with regard to stereoscopic analysis of structural elements, calculation of porosity profiles using resistivity and sonic logs, determination of variations of petrophysical in-situ parameter with depth(increasing age); in particular mapping the distribution and extent of alteration and possible fluid path way zones. All log analysis will be closely correlated with petrographical and geochemical core analysis.
The temperature pattern is attributed to a superposition of thermal and hydraulic processes. In the deeper borehole (HSDP-2, depth 3.1 km) detailed temperature monitoring was performed. Temperature measurements reveal two different thermal regimes. The upper part is characterised by cold temperatures and a negative temperature gradient similar to those observed in the shallow pilot borehole. Below 1100 m, increasing temperatures are observed. Different processes, such as topographically driven groundwater flow, ingress of salt water and conductive previous termheatnext term flow are investigated by numerical modeling. A pure conductive scenario fails to match the temperature measurements, implying that both borehole sections are overprinted by advective conditions. Coupled fluid and previous termheatnext term flow modeling with solute transport yield results that agree with observed temperatures. These data were taken at 07/02/1999 from 09.45 a.m. to 10.00 p.m.
The target of this study is to correlate the logging data with the lithological and structural characteristics of the drilled volcanic sequences; in particular to extract information which are important to better understand alteration processes as well as the hydrogeological and hydrogeochemical situation. The specific targets of this study are: core-log comparisons and detailed reconstruction of the lithological profile with individual lithological units , evaluation of the BHTV data with regard to stereoscopic analysis of structural elements, calculation of porosity profiles using resistivity and sonic logs, determination of variations of petrophysical in-situ parameter with depth(increasing age); in particular mapping the distribution and extent of alteration and possible fluid path way zones. All log analysis will be closely correlated with petrographical and geochemical core analysis.
The target of this study is to correlate the logging data with the lithological and structural characteristics of the drilled volcanic sequences; in particular to extract information which are important to better understand alteration processes as well as the hydrogeological and hydrogeochemical situation. The specific targets of this study are: core-log comparisons and detailed reconstruction of the lithological profile with individual lithological units , evaluation of the BHTV data with regard to stereoscopic analysis of structural elements, calculation of porosity profiles using resistivity and sonic logs, determination of variations of petrophysical in-situ parameter with depth(increasing age); in particular mapping the distribution and extent of alteration and possible fluid path way zones. All log analysis will be closely correlated with petrographical and geochemical core analysis.
The GFZ Potsdam started a log interpretation study in cooperation with the Technical University of Aachen. As a first result, the logged profile allows for a subdivision of the lithological profile into at least two major zones: (1) a subaerial zone (1900-3600ft) and (2) a submarine zone (3600-6100ft). In addition, the geophysical measurements indicate a further subdivision into the Log Units 1-4 , each unit distinguished by different geophyshical log responses: (Fig.2) (Fig.4) The basaltic lava flows of the first unit (Log Unit1), consisting of Aa-and Pahoehoe-Lavas, show high total GR and low resistivity values in general. These flows do not only reveal large variations in resistivity and gamma ray activity between different flow types but also within single lava flows. This internal variation seems to be controled by vesicularity and alteration of the single lava flows. High total GR values appear in rocks with low olivine content and sparse vesicularity.
The temperature pattern is attributed to a superposition of thermal and hydraulic processes. In the deeper borehole (HSDP-2, depth 3.1 km) detailed temperature monitoring was performed. Temperature measurements reveal two different thermal regimes. The upper part is characterised by cold temperatures and a negative temperature gradient similar to those observed in the shallow pilot borehole. Below 1100 m, increasing temperatures are observed. Different processes, such as topographically driven groundwater flow, ingress of salt water and conductive previous termheatnext term flow are investigated by numerical modeling. A pure conductive scenario fails to match the temperature measurements, implying that both borehole sections are overprinted by advective conditions. Coupled fluid and previous termheatnext term flow modeling with solute transport yield results that agree with observed temperatures.
A quasi-continuous magnetic log has been obtained in the Hawaii Scientific Drilling Project 2 (HSDP-2) between 600 m and 1800 m, which corresponds to a time interval of approximately 350 ka to 480 ka. A tri-axial borehole magnetometer was employed to measure the horizontal and vertical magnetic fields. Measurements were taken in downhole and uphole runs, with a good correlation between the two. In a first step the logs were corrected for the transfer function of the employed low-pass filter and then for the logging depths. To calculate rock magnetizations from magnetic components, we used a multidisk cylindrical model for the penetrated rocks. The disk thickness corresponds with 0.1 m to the logging sampling rate. Magnetic borehole logging in the HSDP-2 hole has established the following: Massive lava flows can be distinguished from those with prevailing hyaloclastites and enables us to supplement the lithology, especially in depth intervals with poor core recovery.
A quasi-continuous magnetic log has been obtained in the Hawaii Scientific Drilling Project 2 (HSDP-2) between 600 m and 1800 m, which corresponds to a time interval of approximately 350 ka to 480 ka. A tri-axial borehole magnetometer was employed to measure the horizontal and vertical magnetic fields. Measurements were taken in downhole and uphole runs, with a good correlation between the two. In a first step the logs were corrected for the transfer function of the employed low-pass filter and then for the logging depths. To calculate rock magnetizations from magnetic components, we used a multidisk cylindrical model for the penetrated rocks. The disk thickness corresponds with 0.1 m to the logging sampling rate. Magnetic borehole logging in the HSDP-2 hole has established the following: Massive lava flows can be distinguished from those with prevailing hyaloclastites and enables us to supplement the lithology, especially in depth intervals with poor core recovery.
A quasi-continuous magnetic log has been obtained in the Hawaii Scientific Drilling Project 2 (HSDP-2) between 600 m and 1800 m, which corresponds to a time interval of approximately 350 ka to 480 ka. A tri-axial borehole magnetometer was employed to measure the horizontal and vertical magnetic fields. Measurements were taken in downhole and uphole runs, with a good correlation between the two. In a first step the logs were corrected for the transfer function of the employed low-pass filter and then for the logging depths. To calculate rock magnetizations from magnetic components, we used a multidisk cylindrical model for the penetrated rocks. The disk thickness corresponds with 0.1 m to the logging sampling rate. Magnetic borehole logging in the HSDP-2 hole has established the following: Massive lava flows can be distinguished from those with prevailing hyaloclastites and enables us to supplement the lithology, especially in depth intervals with poor core recovery.
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