Distributed temperature sensing as a down-hole tool in hydrogeology

Distributed Temperature Sensing (DTS) technology enables down-hole temperature monitoring to study hydrogeological processes at unprecedentedly high frequency and spatial resolution. DTS has been widely applied in passive mode in site investigations of groundwater flow, in-well flow, and subsurface thermal property estimation. However, recent years have seen the further development of the use of DTS in an active mode (A-DTS) for which heat sources are deployed. A suite of recent studies using A-DTS down-hole in hydrogeological investigations illustrate the wide range of different approaches and creativity in designing methodologies. The purpose of this review is to outline and discuss the various applications and limitations of DTS in down-hole investigations for hydrogeological conditions and aquifer geological properties. To this end, we first review examples where passive DTS has been used to study hydrogeology via down-hole applications. Secondly, we discuss and categorize current A-DTS borehole methods into three types. These are thermal advection tests, hybrid cable flow logging, and heat pulse tests. We explore the various options with regards to cable installation, heating approach, duration, and spatial extent in order to improve their applicability in a range of settings. These determine the extent to which each method is sensitive to thermal properties, vertical in well flow, or natural gradient flow. Our review confirms that the application of DTS has significant advantages over discrete point temperature measurements, particularly in deep wells, and highlights the potential for further method developments in conjunction with other emerging fiber optic based sensors such as Distributed Acoustic Sensing. This article is protected by copyright. All rights reserved

Grundlagenforschung zur Entwicklung und Anwendung von Sensoren fuer die Erfassung und Weiterleitung seismischer Aktivitaeten Abschlussbericht

Up to now there are no seismic sensors for long time high temperature applications available because of the failure of electronics by temperatures above 450 Kelvin. The aim of this project is to search for sensor principles suitable for seismic measurements in extreme environments especially in deep boreholes. A first test model of a mechanical oscillator of such a seismic sensor was developed and investigated. The dynamical behaviour of the oscillator is simulated by use of the finite element program ANSYS. A fiber optic Fabry-Perot-Interferometer represents a suitable principle for single transforming. The project was finished untimely because the institute is closed down. (orig.)Gegenwaertig sind keine seismischen Sensoren, die fuer den Einsatz bei hohen Temperaturen ueber lange Zeitraeume geeignet sind, verfuegbar. Der wesentliche Grund dafuer liegt im Versagen der Elektronik bei Temperaturen ueber 450 Grad Kelvin. Das Ziel dieses Projektes ist die Suche nach Prinziploesungen fuer seismische Sensoren fuer den Einsatz unter extremen aeusseren Bedingungen, speziell in tiefen Bohrloechern. Ein erstes Muster des mechanischen Empfaengers eines solchen seismischen Sensors wurde entwickelt und getestet. Das dynamische Verhalten des mechanischen Schwingers wird mit Hilfe des FEM-Programms ANSYS simuliert. Als geeignetes Prinzip fuer die Signalwandlung erweist sich ein faseroptisches Fabry-Perot-Interferometer. Das Projekt musste vorzeitig auf Grund der Schliessung des Instituts beendet werden. (orig.)Available from TIB Hannover: F94B0327+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman

Faseroptischer Lasersensor zur on-line Diagnostik von PAK- und BTX-Schadstoffen. PAK-Teilvorhaben: Felderprobung des Messsystems Abschlussbericht

Available from TIB Hannover: F00B776 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung und Forschung (BMBF), Bonn (Germany)DEGerman