Distributed Temperature Sensing as a downhole tool in hydrogeology

Abstract

Distributed Temperature Sensing (DTS) technology enables downhole 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 downhole 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 downhole 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 downhole 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 hydrogeophysical tools.

Fiber‐Optic Sensing for Environmental Applications: Where We Have Come From and What Is Possible

“…Fiber-optic distributed temperature sensing (DTS or FO-DTS) is the most widely used fiber-optic sensing method for environmental applications (especially hydrologic applications; Bense et al, 2016;Briggs et al, 2012;Schneider et al, 2011;Sebok et al, 2015). Although FO-DTS (Hartog & Gamble, 1991).…”

Scaling, similarity, and the fourth paradigm for hydrology

“…In particular, there are exciting developments in mesoscale (i.e., hillslope to catchment) observations, which are critical for testing hypotheses about scaling (REA, RH, REW) by connecting point measurements, hydrological models, and remote sensing observations. Examples include recent advances in cosmic ray neutron sensors (Franz et al, 2015;Köhli et al, 2016;Zreda et al, 2008), distributed temperature sensing (DTS; Steele-Dunne et al, 2010;Bense et al, 2016;Dong et al, 2016), soil moisture observations, the use of crowdsourcing (de Vos et al, 2016) and microwave signal propagation from telecommunications towers for precipitation (Leijnse et al, 2007), to the rise in the use of unmanned autonomous vehicles to characterize the landscape on centimeter scale (Vivoni et al, 2014). These alternative data sources enhance our ability to observe, understand, and simulate the hydrological cycle.…”

FBG-Based Monitoring of Geohazards: Current Status and Trends

“…While interesting works have been reported on the use of FBG sensors for soil moisture measurement [59,60], its applications in geohazard monitoring have still been rare. It is noteworthy that, using ROTDR or BOTDA technologies, distributed temperature sensing (DTS) optical fiber cables have been successfully applied to monitor soil moisture or seepage [61,62,63]. …”