One of the issues with multilateral wells is determining the contribution of each lateral to the total production that is measured at the surface. Also, if water is detected at the surface or if the multilateral well performance declines, then it is difficult to identify which lateral or laterals are causing the production decline. One way to estimate the contribution from each lateral is to run production Logging Tools (PLT). Unfortunately, PLT jobs are expensive, time-consuming, labor-intensive and involve operational risks. An alternative way to measure the production from each lateral is to use Distributed Temperature Sensing (DTS) technology. Recent advances in DTS technology enable measuring the temperature profile in horizontal wells with high precision and resolution. The changes in the temperature profile are successfully used to calculate the production profile in horizontal wells. In this research, we develop a computer program that uses a multilateral well model to calculate the pressure and temperature profile in the motherbore. The results help understand the temperature and pressure behaviors in multilateral wells that are crucial in designing and optimizing DTS installations. Also, this model can be coupled with an inversion model that can use the measured temperature and pressure profile to calculate the production from each lateral. Our model shows that changing the permeability or the water cut produced from one lateral results in a clear signature in the motherbore temperature profile that can be measured with DTS technology. However, varying the length of one of the lateral did not seem to impact the temperature profile in the motherbore. For future work, this research recommends developing a numerical reservoir model that would enable studying the effect of lateral inference and reservoir heterogeneity. Also recommended is developing an inversion model that can be used to validate our model using field data.

In recent years, wireline temperature profiling methods have evolved to offer new insight into fractured rock hydrogeology. An important advance in temperature logging makes use of boreholes temporarily sealed with flexible impervious fabric liners so that the water column is static and effects of cross-connection are eliminated. For this project a characterization technique was developed based on combining fibre optic distributed temperatures sensing (DTS) with active heating within boreholes sealed with underground liners. DTS systems provide a temperature profiling method that offers improved temporal resolution when compared with wireline trolling based techniques. The ability to collect temperature profiles rapidly in time can improve understanding of transient processes. In this study the advantage of a sealed borehole environment for temperature investigations is demonstrated. Evidence for identifying active groundwater flow under natural gradient conditions using DTS heat pulse testing is presented through a comparison with high resolution geologic logging and hydraulic datasets.

Distributed Temperature Sensing (DTS) has been used in a variety of different applications. Its ability to detect temperature fluctuations along fiber optic lines that stretch for several kilometers has made it a popular topic in various fields of science, engineering, and technology. From pre-fire detection to ecological monitoring, DTS has taken a vital role in scientific research. DTS uses the principle of backscattering by three different spectral components, e.g., Rayleigh scattering, Brillouin scattering, and Raman scattering. Although there have been various improvements to DTS, its slow response time and poor spatial resolution have been hard to overcome. Its repetition rate is low because the pulse must travel the distance of the fiber optic line and return to the detector to record the temperature change along the fiber. A spatial resolution of 7.4 cm with a response time as low as 1 second and a temperature resolution of the 0.196 ℃ is achieved from the current Raman-based DTS system. This research proves that high-spatial resolution can be obtained with the use of a Silicon Avalanche Photodetector with a 1 GHz bandwidth. / MS

Infiltration and inflow (I/I) are common problems in the foul sewer system. A method to detect I/I that is not commonly used in Sweden is DTS, Distributed Temperature Sensing. DTS is based on continuous measurements of temperature over a predetermined distance in the sewer system. The I/I is detected as temperature differences in the temperature data that is registered in the sewer system. The measurements often take place over a couple of weeks or months in the sewer system. The aim of this project was to review previous studies where DTS was used to detect I/I in foul sewers.  Data from a wastewater treatment plant in Umeå together with meteorological data were analysed to be able to visualize the problem of I/I and then suggest how DTS can be applied in Sweden. Both automated and visual analyses was performed to find if there were any relationships between wastewater temperature, wastewater flow and precipitation.   The outcome was that it is possible to apply DTS in the foul sewages to detect I/I. DTS seemed to be able to detect I/I in all types of sewage material, however it is dependent on that the I/I temperature differs from the temperature of the foul sewage water. It is an expensive technique but if it is meant to be used many times to analyse bigger areas it can be worth the costs. If larger areas are to be investigated, the costs for DTS and current methods are approximately the same.  At the wastewater treatment plant in Umeå, a slight relationship between wastewater temperature, wastewater flow and precipitation could be detected. The degree of dilution was calculated to 1,34 which means that about 25% of the sewage water is I/I. The conclusion from this was that I/I exists in the foul sewers in Umeå. The leakage points could not be located with this analysis. DTS could be a possible method to detect the leakage points of I/I in foul sewers. Unlike smoke tests, colouring and video-inspection of the sewers, DTS might be able to detect smaller leakage points. / Tillskottsvatten är ett vanligt problem i spillvattenledningsnätet. DTS, Distributed Temperature Sensing är en metod som inte är vanlig i Sverige för kontroll av spillvattenledningar. Tekniken bygger på kontinuerliga temperaturmätningar under en tidsperiod över en förutbestämd sträcka och registrerar temperaturavvikelser som kan uppstå i samband med inläckage av tillskottsvatten. Syftet med projektet var att granska tidigare utförda studier med DTS för att ta reda på hur tekniken kan användas för att lokalisera inläckage i spillvattenledningar. För att vidare illustrera problematiken med tillskottsvatten i spillvattennätet samt föreslå hur DTS kan appliceras i Sverige genomfördes en analys av mätdata på inkommande vatten till reningsverket på Ön, Umeå. Både visuella och automatiserade analyser genomfördes där tolkningar gjordes utifrån mätdata från reningsverket tillsammans med nederbörds- och lufttemperaturdata. En regressionsanalys genomfördes som automatiserad analys för att undersöka eventuella samband mellan spillvattentemperatur, spillvattenflöde och nederbörd. Projektet inleddes med en litteraturstudie där det utreddes hur DTS fungerar teoretiskt och praktiskt. Litteraturstudien visade att DTS är praktiskt möjligt att applicera i spillvattenledningsnätet för att leta inläckagepunkter för tillskottsvatten. Inläckage kan registreras som ökningar eller sänkningar i spillvattentemperaturen beroende på lufttemperaturen. Den är inte beroende av material på ledningarna men däremot är DTS beroende av att tillskottsvattnet är av annan temperatur än spillvattnet. Det är en dyr teknik men kan vara värt investeringskostnaderna om mätningar tänkt ske många gånger under längre perioder. Vid kontroll av större områden med hjälp av röktest kombinerat med färgning av vatten och filmning är kostnaderna ungefär de samma. Utifrån mätdatan från reningsverket och nederbördsdatan från Umeå universitet kunde vissa samband påvisas mellan spillvattentemperatur, spillvattenflöde och nederbörd. Ett visst samband kunde även urskiljas mellan spillvattentemperatur och spillvattenflöde. Utspädningsgraden av spillvattnet beräknades till 1,34 vilket innebär att cirka 25% av vattnet i spillvattenledningarna är tillskottsvatten. Slutsatsen som kunde dras utifrån detta var att tillskottsvatten existerar i spillvattenledningsnätet som leder till reningsverket på Ön i Umeå. Däremot kunde inga slutsatser dras för att säga var inläckage av tillskottsvatten sker. DTS skulle kunna appliceras i ledningsnäten för att undersöka närmare var inläckagepunkterna är och tillskillnad från rökning, färgning av vatten och filmning som används idag kan DTS sannolikt upptäcka fler typer av inläckage.

Soil cover systems are an integral part of a mine reclamation program and are increasing in area. Knowledge of temperatures and thermal properties in the cover system provide important information regarding the energy balance, thermal regime, as well as preliminary insight into soil water content. Cover system temperatures and thermal properties are measured at a small number of vertically intensive profiles. Current methods do not provide any information as to the spatial variation of temperatures and thermal properties at scales other than the point scale. The objective of this study was to investigate the spatial scaling of thermal properties in reclamation cover systems. A distributed temperature sensing (DTS) system was installed in three cover systems of various textures and configurations. Semivariogram analysis demonstrated that on a 40 m slope consisting of mineral soil over sand (Site #1) soil temperatures did not exhibit any spatial structure, due to the presence of vegetation. A 100 m cover system comprised of a structureless sand (Site #2) was confirmed to be spatially uniform through semivariogram analysis. Semivariograms at Site #2 displayed secondary structure that corresponded to the 65 m plateau and 35 m slope. Site #3 consisted of a uniform peat and a 2% slope. Spatial structure was non-existent at Site #3 and was attributed to the unique thermal properties of peat that magnified the effect of microtopography on the surface energy balance. A method to estimate apparent thermal inertia (ATI) using DTS measurements at the soil surface was developed. Apparent thermal inertia was found to be less uncertain than the current standard apparent thermal diffusivity. The ATI method was determined to be the preferred method as it was related to soil water content and not prone to estimation errors due to imprecise depth measurement. The spatial scaling properties of a 236 m cover system (Site #3) were investigated using estimations of ATI. Measurements were taken every meter along the transect for bulk density, elevation, air-dried thermal conductivity and air-dried volumetric heat capacity. The dominant scale of variation in ATI was not related to physical or thermal properties, which tended towards the 3 m scale (bulk density and thermal conductivity) or the 108 m and field scale trend (elevation and volumetric heat capacity). The dominant scale of variation in ATI shifted between 30 m and the field scale trend and was related to water content as represented by the soil matric potential. A dry cover system tended to homogenize thermal property distribution, leading to a dominance of the 108 m and field scale trend. Wetter days led to a shift to the 30 m scale, with intermediate days showing a mix in scale dominance. Information on thermal property spatial scaling properties of cover systems can be used to optimally design monitoring systems that measure at the same scale as that which the cover is performing. Characterizing the spatial variability of the system will lead to better cover system designs and ultimately a more sustainable system.

abstract: Underground transmission cables in power systems are less likely to experience electrical faults, however, resulting outage times are much greater in the event that a failure does occur. Unlike overhead lines, underground cables are not self-healing from flashover events. The faulted section must be located and repaired before the line can be put back into service. Since this will often require excavation of the underground duct bank, the procedure to repair the faulted section is both costly and time consuming. These added complications are the prime motivators for developing accurate and reliable ratings for underground cable circuits. This work will review the methods by which power ratings, or ampacity, for underground cables are determined and then evaluate those ratings by making comparison with measured data taken from an underground 69 kV cable, which is part of the Salt River Project (SRP) power subtransmission system. The process of acquiring, installing, and commissioning the temperature monitoring system is covered in detail as well. The collected data are also used to evaluate typical assumptions made when determining underground cable ratings such as cable hot-spot location and ambient temperatures. Analysis results show that the commonly made assumption that the deepest portion of an underground power cable installation will be the hot-spot location does not always hold true. It is shown that distributed cable temperature measurements can be used to locate the proper line segment to be used for cable ampacity calculations. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2015

This thesis is based on a research project to monitor the temperature profile along a power cable using the fibre optic Distributed Temperature Sensing (DTS) technology. Based on the temperature measured by a DTS system, real time condition monitoring of power cables can be achieved. In this thesis, there are three main research themes. 1. Develop a DTS system for industrial applications. The entire hardware system and measuring software are developed to be an industrial product. Multiple functions are provided for the convenience of users to conduct temperature monitoring, temperature history logging and off-line simulation. 2. Enhance the robustness of the DTS system. An algorithm for signal compensation is developed to eliminate the signal fluctuation due to disturbance from the hardware and its working environment. It ensures robustness of the system in industrial environments and applicability to different system configurations. 3. Improve the accuracy of the DTS system. A calibration algorithm based on cubic spline fitting is developed to cope with non-uniform fibre loss in the system, which greatly improved the accuracy of the temperature decoding in real applications with unavoidable nonlinear characteristics. The developed DTS system and the algorithms have been verified by continuous experiments for about one year and achieved a temperature resolution of 0.1 degree Celsius, a spatial resolution of 1 meter, and a maximum error of 2 degree Celsius in an optic fibre with the length of 2910 metres.

From the monitoring of deep ocean conditions to the imaging and exploration of the vast universe, optical sensors are playing a unique, critical role in all areas of scientific research. Optical fiber sensors, in particular, are not only widely used in daily life such as for medical inspection, structural health monitoring, and environmental surveillance, but also in high-tech, high-security applications such as missile guidance or monitoring of aircraft engines and structures. Measurements of physical parameters are required in harsh environments including high pressure, high temperature, highly electromagnetically-active and corrosive conditions. A typical example is fossil fuel-based power plants. Unfortunately, current optical fiber sensors for high-temperature monitoring can work only for single point measurement, as traditional fully-distributed temperature sensing techniques are restricted for temperatures below 800°C due to the limitation of the fragile character of silica fiber under high temperature. In this research, a first-of-its-kind technology was developed which pushed the limits of fully distributed temperature sensing (DTS) in harsh environments by exploring the feasibility of DTS in optical sapphire waveguides. An all sapphire fiber-based Raman DTS system was demonstrated in a 3-meters long sapphire fiber up to a temperature of 1400°C with a spatial resolution of 16.4cm and a standard deviation of a few degrees Celsius. In this dissertation, the design, fabrication, and testing of the sapphire fiber-based Raman DTS system are discussed in detail. The plan and direction for future work are also suggested with an aim for commercialization. / Ph. D.

Der Zustrom von Grundwasser zu Seen (lacustrine groundwater discharge, LGD) kann signifikante Auswirkungen auf Qualität und Quantität des Seewassers haben. Viele Ansätze zur Identifikation und Quantifizierung von LGD basieren auf Temperaturunterschieden zwischen Grund- und Seewasser und der Messung des damit einhergehenden Wärmetransports. Ziel der Doktorarbeit ist es, Signalfortpflanzung und -ausbreitung des Grundwasserzustroms von der Punktskala an der Sediment-Wasser-Grenzfläche über den Wasserkörper bis zur Grenzfläche Wasseroberfläche-Atmosphäre zu untersuchen. Getestet wird die Hypothese, dass das im Verhältnis zum Umgebungswasser wärmere und daher leichtere Grundwasser in der kalten Wassersäule aufsteigt und die Detektion von LGD an der Wasseroberfläche mit thermalen Infrarot Aufnahmen (TIR) erlaubt. Zunächst wird mit der hierarchical patch dynamics ein Konzept entwickelt, das eine angemessene Kombination multipler Techniken zur Erfassung von Wärme- und Wasserflüssen anbietet (Kap. 2). Dabei werden verschiedene räumliche Skalen und ökohydrologische Grenzflächen abgedeckt. Darauf basierend werden in einem Mesokosmos-Experiment unterschiedliche LGD-Raten durch den Zustrom von warmem Wasser am Grund eines Outdoor-Pools simuliert (Kap. 3 und 4). Ein Glasfaserkabel (fibre-optic distributed temperature sensing, FO-DTS) wird in verschiedenen Tiefen installiert, um das Wärmesignal des Grundwasserzustroms unter verschiedenen Bedingungen zu verfolgen. Mit einer TIR-Kamera wird die Temperatur des Oberflächenwassers aufgezeichnet. Die Aufnahmen werden mit FO-DTS-Temperaturen von 2 cm unter der Wasseroberfläche validiert. Die Anwendung von TIR und FO-DTS ermöglicht die Detektion von LGD in der Wassersäule und an der Grenzfläche Wasseroberfläche-Atmosphäre. Wolkenbedeckung und der Tagesgang der Netto-Strahlung kontrollieren den Auftrieb von LGD und die Zuverlässigkeit der TIR-Ergebnisse. Die besten Ergebnisse werden bei Bewölkung und nachts erzielt. / Lacustrine groundwater discharge (LGD) can have significant impacts on lake water quantity and quality. There is a need to understand LGD mechanisms and to improve measurement methods for LGD. Approaches to identify and quantify LGD are based on significant temperature differences between GW and lake water. The main goal of this PhD thesis is to trace heat signal propagation of LGD from the point scale at the sediment-water interface across the overlying water body to the water surface-atmosphere interface. The PhD thesis tests the hypothesis that the positive buoyancy of warm GW causes upwelling across the cold water column and allows detection of LGD at the water surface by thermal infrared imaging (TIR). First, a general conceptual framework is developed based on hierarchical patch dynamics (HPD). It guides researchers on adequately combining multiple heat tracing techniques to identify and quantify heat and water exchange over several spatial scales and ecohydrological interfaces (Chapter 2). Second, the conceptual framework is used for the design of a mesocosm experiment (Chapters 3 and 4). Different LGD rates were simulated by injecting relatively warm water at the bottom of an outdoor mesocosm. A fiber optic distributed temperature sensing (FO-DTS) cable was installed in a 3D setup in the water column to trace the heat signal of the simulated LGD under different weather conditions and over entire diurnal cycles. Finally, a TIR camera was mounted 4 meters above the mesocosm to monitor water surface temperatures. TIR images were validated using FO-DTS temperature data 2 cm below the water surface (Chapter 4). The positive buoyancy of relatively warm LGD allows the detection of GW across the water column and at the water surface-atmosphere interface by FO-DTS and TIR. Cloud cover and diurnal cycle of net radiation strongly control the upwelling of simulated LGD and the reliability of TIR for detection of LGD at the water surface-atmosphere interface. Optimal results are obtained under overcast conditions and during night.

Die Untersuchung von Klimaszenarien ergab, dass die Grundwasserneubildung in Nordostdeutschland abnehmen könnte. Um Süßgewässer zu erhalten müssen neue Strategien entwickelt werden. Im Gebiet des Lietzengrabens wird Klarwasser eingeleitet, um Feuchtgebiete und Seen zu erhalten. Diese Strategie wurde durch eine Szenarioanalyse erarbeitet, die sich auf das hydrologische iterative Modell ArcEGMO-ASM stützte. In dieser Arbeit wurde das voll integrierte Modell HydroGeoSphere genutzt, um den Fluss von Wasser an der Oberfläche und im Untergrund zu simulieren. Basierend auf dieser Simulation wurden Fließpfade und Aufenthaltszeiten abgeschätzt. Die Ergebnisse beider Modelle wurden analysiert und verglichen. Mit beiden Modellen war es möglich, die Abfluss- und Grundwasserdynamiken im Einzugsgebiet zu reproduzieren. Bei der Anwendung von HydroGeoSphere fehlten Möglichkeiten zur Berücksichtigung von z.B. Schneefall und Wehren, welche in ArcEGMO-ASM vorhanden sind. Die Kalibrierung des Modells lieferte Parameterwerte, die eine Reproduktion der Dynamiken erlaubten. Allerdings könnte HydroGeoSphere nur eingeschränkt nutzbar sein, da die Werte teils unrealistisch waren. HydroGeoSphere ermöglichte aber die Abschätzung von unterirdischen Fließpfaden und Aufenthaltszeiten. Weiter wurde der Austritt von Grundwasser in einen Bachabschnitt durch Messungen bestimmt und mit Simulationsergebnissen verglichen. Keines der Modelle war geeignet, die räumlichen Muster auf dieser Skala zu reproduzieren. Die simulierten Exfiltrationsraten wichen von den beobachteten ab. Der Vergleich von ArcEGMO-ASM und HydroGeoSphere zeigte die Vorteile und Grenzen der Modelle auf. Der Einsatz von HydroGeoSphere bei Untersuchungen von Bewirtschaftungsstrategien macht sich noch nicht bezahlt, vergleicht man den Aufwand mit den Vorteilen. Da HydroGeoSphere weiterentwickelt wird und die Rechenkapazitäten zunehmen, könnte das Modell in der nahen Zukunft in der Praxis nutzbar sein. / Analysis of climatic scenarios for North-East Germany showed that groundwater recharge could decline. In order to sustain freshwaters, new strategies must be developed. At the Lietzengraben catchment treated wastewater is discharged to sustain wetlands and lakes in the catchment. This management strategy was developed previously by scenario analysis, performed by the hydrological iterative model ArcEGMO-ASM. In this work, the fully integrated model HydroGeoSphere was used to simulate the surface and subsurface water flow in the catchment. Based on the simulation results, flow paths and residence times were estimated. The results of the simulations by both models were investigated and compared. It was possible to reproduce the catchment dynamics regarding discharge and groundwater heads reasonably well with both models. The application of HydroGeoSphere was limited due to the inability of the model to represent features like snowfall and weirs, which are represented in ArcEGMO-ASM. The calibrated parameter values enabled the model to reproduce the catchment dynamics reasonably well. HydroGeoSphere may be limited in its use since the obtained values are partially unrealistic. HydroGeoSphere allowed the approximation of subsurface flow paths and residence times. The exfiltration of groundwater to a stream reach was estimated by measurements and compared to simulation results. Both models were not able to reproduce the spatial patterns on a sub-reach scale and the calculated exfiltration rates did not match the observed rates. The comparison of ArcEGMO-ASM and HydroGeoSphere showed the advantages and limitations of both models. Comparing the overall additional effort to the benefits, however, the application of HydroGeoSphere to investigations regarding management strategies or scenario analyses may not pay off. Since HydroGeoSphere is under steady development and computational resources improve, the use of HydroGeoSphere may be applicable in the near future.