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Distributed temperature sensing is known to provide sharp signals which are very efficient for mapping hydraulically active fractures in wellbores. High-resolution temperature sensing has specifically demonstrated its capacity to characterize very low flows in wellbores. But as sharp as they can be, temperature profiles are often difficult to decipher. The aim of the present work is to provide and to test the “Borehole Heat Budget Calculator” (BHB Calculator), which is implemented as a fast and easy to use tool for the quantitative analysis of depth-temperature profiles. The Calculator is suitable for most pumping and draining configurations, as the heat budget is generalized for modelling multidirectional flow systems within the same wellbore. The formatted worksheet allows the quick exploitation of temperature logs, and is applicable for the characterization of distributed fractures in long screened wellbores. Objectives of the heat modelling are to enhance the readability of complex depth-temperature data, as well as to quantify distribution of inflow intensities and temperatures with depth. The use of heat budget helps to clearly visualize how heat conduction and heat advection contributions are distributed along wellbores profiles. Calculations of inflow temperatures and their evolution through pumping duration is a prerequisite to infer about the nature of aquifer properties (i.e. conduits, distributed or discrete fractures, porous media), as well as to give insight information about the mapping of effective flow paths draining the aquifer. The efficiency and limitations of the BHB Calculator are being tested through high-resolution temperature logging, along with complementary flowmetering and televiewing logging in fractured aquifers located in the St-Lawrence Lowlands, Quebec, Canada.

International audience; This work aims to provide an overview of the thermal processes that shape wellbore temperature profiles under static and dynamicconditions. Understanding of the respective influences of advection and conduction heat fluxes is improved through the useof a new heat budget at the borehole scale. Keeping in mind the thermal processes involved, a qualitative interpretation of thetemperature profiles allows the occurrence, the position, and the origin of groundwater flowing into wellbores from hydraulicallyactive fractures to be constrained.With the use of a heat budget developed at the borehole scale, temperature logging efficiency hasbeen quantitatively enhanced and allows inflow temperatures to be calculated through the simultaneous use of a flowmeter. Undercertain hydraulic or pumping conditions, both inflow intensities and associated temperatures can also be directly modelled fromtemperature 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 wellsinstalled 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 inwellbores, as well as the existence of ambient flows with a high degree of sensitivity, even at very low flows. Heat budget calculationsat the borehole scale during pumping indicate that heat advection fluxes rapidly dominate over heat conduction fluxes with theborehole wall. The full characterization of inflow intensities provides information about the distribution of hydraulic propertieswith depth. The full knowledge of inflow temperatures indicates horizons that are drained from within the aquifer, providingadvantageous information on the depth from which groundwater originates during pumping.1. Introduction