High-Resolution Wellbore Temperature Logging Combined with a Borehole-Scale Heat Budget: Conceptual and Analytical Approaches to Characterize Hydraulically Active Fractures and Groundwater Origin

Abstract

This work aims to provide an overview of the thermal processes that shape wellbore temperature profiles under static and dynamic conditions. Understanding of the respective influences of advection and conduction heat fluxes is improved through the use of a new heat budget at the borehole scale. Keeping in mind the thermal processes involved, a qualitative interpretation of the temperature profiles allows the occurrence, the position, and the origin of groundwater flowing into wellbores from hydraulically active fractures to be constrained. With the use of a heat budget developed at the borehole scale, temperature logging efficiency has been quantitatively enhanced and allows inflow temperatures to be calculated through the simultaneous use of a flowmeter. Under certain hydraulic or pumping conditions, both inflow intensities and associated temperatures can also be directly modelled from temperature data and the use of the heat budget. Theoretical and applied examples of the heat budget application are provided. Applied examples are shown using high-resolution temperature logging, spinner flow metering, and televiewing for three wells installed in fractured bedrock aquifers in the St-Lawrence Lowlands, Quebec, Canada. Through relatively rapid manipulations, thermal measurements in such cases can be used to detect the intervals or discrete positions of hydraulically active fractures in wellbores, as well as the existence of ambient flows with a high degree of sensitivity, even at very low flows. Heat budget calculations at the borehole scale during pumping indicate that heat advection fluxes rapidly dominate over heat conduction fluxes with the borehole wall. The full characterization of inflow intensities provides information about the distribution of hydraulic properties with depth. The full knowledge of inflow temperatures indicates horizons that are drained from within the aquifer, providing advantageous information on the depth from which groundwater originates during pumping.

Review: Hydrogeology of weathered crystalline/hard-rock aquifers—guidelines for the operational survey and management of their groundwater resources

“…The role of weathering in creation of the fractured layer is also directly or indirectly confirmed by the data sets of most of the authors working on HRA. See for instance Davies et al (2014) and the countries cited previously, as well as Chilton and Smith-Carington (1984), Chilton and Foster (1995), Howard (1999, 2000), Chirindja et al (2017), Dickson et al (2018), Muchingami et al (2019) and Vassolo et al (2019) for Africa; Chambel (2014) for Portugal; Comte et al (2012) for Ireland; Tan et al (2017) for Denmark; Riber et al (2017) for Sweden; Francés et al (2014) for Spain; Krasny (1996) for Central Europe; Baiocchi et al (2014Baiocchi et al ( , 2016 for the Mediterranean Europe; Chou et al (2014) and Chuang et al (2016) for Taiwan; David et al (2014) for Australia; Riber et al (2017), Jahns (1943, Hart (2016), Sanford (2017), Meyzonnat et al (2018) and Setlur et al (2019) for North America, etc. Even if several authors have not attributed the fractures to weathering processes, some others keep an ambiguity on this genetic relationship, while others do not challenge or discuss this issue at all, at least for the uppermost crust (0-2 km; Achtziger-Zupancic et al 2017;Ingebritsen and Gleeson 2017).…”

Borehole Heat Budget Calculator: A New Tool for the Quick Exploitation of High-Resolution Temperature Profiles by Hydrogeologists

“…The seasonal variation of the temperature at the surface of the soil propagates until 15 m depth and is followed by a reverse geogradient to the bottom of the well. More detailed information about the shape of the geogradient in the context of the Canadian is provided in Gosselin and Mareschal [6] and Meyzonnat et al [20].…”

“…Among other borehole logging techniques, depth-temperature profiling presents the advantages of being a very robust and quick measurement collected with no costly equipment [16]. High resolution temperature logging specifically appears to be extremely sensitive at very low flow [20], which makes this technique one of the most efficient to sharply characterize very low transmissivity fractures, hydraulic properties distribution in wellbore even at low pumping rate, or to identify very low flow (i.e. passive flows).…”

“…To deal with these limitations, the objective of this article is to provide a quantitative analytical software that allows the quick interpretation and exploitation of these usually complex distributed depth-temperature profiles in wellbores. Principles implemented in the software calculation rely on a heat budget applied at the scale of the borehole [20], which is dedicated to the quantification of water fluxes within long screened wellbores. The heat budget is very signifi- The following abbreviations are used throughout the text for brevity purpose:…”

Depth–Sequential Investigation of Major Ions, δ18O, δ2H and δ13C in Fractured Aquifers of the St. Lawrence Lowlands (Quebec, Canada) Using Passive Samplers

“…In the context of heterogeneous aquifers (implicitly including fractured aquifers), sequential passive sampling would benefit by being preceded by physical borehole investigations [23,41]. This allows addressing the distribution of the productive zones (Equation (1)), as well as to identify the occurrence of ambient flows, if any.…”