A shallow geothermal experiment in a sandy aquifer monitored using electric resistivity tomography

Groundwater resources are increasingly used around the world for geothermal exploitation systems. To monitor such systems and to estimate their governing parameters, we rely mainly on borehole observations of the temperature field at a few locations. Bulk electric resistivity variations can bring important information on temperature changes in aquifers. We have used surface electric resistivity tomography to monitor spatially temperature variations in a sandy aquifer during a thermal injection test. Heated water (48°C) was injected for 70 hours at the rate of [Formula: see text] in a 10.5°C aquifer. Temperature changes derived from time-lapse electric images were in agreement with laboratory water electric conductivity-temperature measurements. In parallel, a coupled hydrogeologic saturated flow and heat transport model was calibrated on geophysical data for the conceptual model, and on hydrogeologic and temperature data for the parameters. The resistivity images showed an upper flow of heated water along the well above the injection screens and led to a new conceptualization of the hydrogeologic source term. The comparison between the temperature models derived from resistivity images and from the simulations was satisfactory. Quantitatively, resistivity changes allowed estimating temperature changes within the aquifer, and qualitatively, the heated plume evolution was successfully monitored. This work demonstrates the ability of electric resistivity tomography to study heat and storage experiments in shallow aquifers. These results could potentially lead to a number of practical applications, such as the monitoring or the design of shallow geothermal systems.

Download Full-text

Time lapse electric resistivity tomography to portray infiltration and hydrologic flow paths from surface to cave

Journal of Hydrology ◽

10.1016/j.jhydrol.2020.125810 ◽

2021 ◽

Vol 593 ◽

pp. 125810

Author(s):

Matthias Leopold ◽

Conrad Gupanis-Broadway ◽

Andy Baker ◽

Stuart Hankin ◽

Pauline Treble

Keyword(s):

Time Lapse ◽

Electric Resistivity ◽

Flow Paths ◽

Resistivity Tomography

Download Full-text

Time-Lapse 3D Electric Tomography for Short-time Monitoring of an Experimental Heat Storage System

Geosciences ◽

10.3390/geosciences9040167 ◽

2019 ◽

Vol 9 (4) ◽

pp. 167 ◽

Cited By ~ 1

Author(s):

Cesare Comina ◽

Nicolò Giordano ◽

Giulia Ghidone ◽

Federico Fischanger

Keyword(s):

Thermal Energy ◽

Heat Storage ◽

Quantitative Estimation ◽

Time Lapse ◽

Electric Resistivity ◽

Local Temperature ◽

Alluvial Deposits ◽

Resistivity Tomography ◽

Living Lab ◽

Geophysical Surveys

A borehole thermal energy storage living lab was built nearby Torino (Northern Italy). The aim of this living lab is to test the ability of the alluvial deposits of the north-western Po Plain to store the thermal energy collected by solar panels. Monitoring the temperature distribution induced in the underground and the effectiveness of the heat storage in this climatic context is not an easy task. For this purpose, different temperature evolution strategies are compared in this paper: Local temperature measurements, numerical simulations and geophysical surveys. These different approaches were compared during a single day of operation of the living lab. The results of this comparison allowed to underline the effectiveness of time-lapse 3D electric resistivity tomography as a non-invasive and cost-effective qualitative heat monitoring tool. This was obtained even in a test site with unfavorable thermo-hydrogeological conditions and high-level anthropic noise. Moreover, the present study demonstrated that, if properly calibrated with local temperature values, time-lapse 3D electric resistivity tomography also provides a quantitative estimation of the underground temperature.

Download Full-text

Laboratory Studies Using Electrical Resistivity Tomography and Fiber Optic Techniques to Detect Seepage Zones in River Embankments

Geosciences ◽

10.3390/geosciences11020069 ◽

2021 ◽

Vol 11 (2) ◽

pp. 69

Author(s):

Azadeh Hojat ◽

Maddalena Ferrario ◽

Diego Arosio ◽

Marco Brunero ◽

Vladislav Ivov Ivanov ◽

...

Keyword(s):

Electrical Resistivity ◽

Electrical Resistivity Tomography ◽

Fiber Optic ◽

Time Lapse ◽

Electrode Spacing ◽

Short Delay ◽

Resistivity Tomography ◽

Temperature Changes ◽

Pros And Cons ◽

Wenner Array

We present the results of laboratory experiments on a down-scaled river levee constructed with clayey material collected from a river embankment where a permanent resistivity instrument has operated since 2015. To create potential seepages through the levee, two zones (5 × 4 cm and 10 × 2 cm) were filled with sand during the levee construction. Electrical resistivity tomography (ERT) technique and Fiber Bragg Grating (FBG) technology were used to study time-lapse variations due to seepage. The ERT profile was spread on the levee crest and the Wenner array with unit electrode spacing a = 3 cm was used. Six organic modified ceramics (ORMOCER) coated 250 μm-diameter fibers were deployed in different parts of the levee. Time-lapse measurements were performed for both techniques from the beginning of each experiment when water was added to the river side until the water was continuously exiting from the seepage zones. The results showed that ERT images could detect seepages from the early stages. Although with a short delay compared to ERT, fiber optic sensors also showed their ability to detect water infiltrations by measuring temperature changes. Both technologies being successful, a discussion about respective peculiarities and pros and cons is proposed to suggest some criteria in choosing the proper technique according to the specific needs.

Download Full-text

Application of time-lapse ERT imaging to watershed characterization

Geophysics ◽

10.1190/1.2907156 ◽

2008 ◽

Vol 73 (3) ◽

pp. G7-G17 ◽

Cited By ~ 115

Author(s):

Carlyle R. Miller ◽

Partha S. Routh ◽

Troy R. Brosten ◽

James P. McNamara

Keyword(s):

Reference Model ◽

Time Lapse ◽

Data Sets ◽

Data Set ◽

Resistivity Tomography ◽

Practical Applications ◽

Data Inversion ◽

Time Periods ◽

The Difference ◽

Base Data

Time-lapse electrical resistivity tomography (ERT) has many practical applications to the study of subsurface properties and processes. When inverting time-lapse ERT data, it is useful to proceed beyond straightforward inversion of data differences and take advantage of the time-lapse nature of the data. We assess various approaches for inverting and interpreting time-lapse ERT data and determine that two approaches work well. The first approach is model subtraction after separate inversion of the data from two time periods, and the second approach is to use the inverted model from a base data set as the reference model or prior information for subsequent time periods. We prefer this second approach. Data inversion methodology should be consideredwhen designing data acquisition; i.e., to utilize the second approach, it is important to collect one or more data sets for which the bulk of the subsurface is in a background or relatively unperturbed state. A third and commonly used approach to time-lapse inversion, inverting the difference between two data sets, localizes the regions of the model in which change has occurred; however, varying noise levels between the two data sets can be problematic. To further assess the various time-lapse inversion approaches, we acquired field data from a catchment within the Dry Creek Experimental Watershed near Boise, Idaho, U.S.A. We combined the complimentary information from individual static ERT inversions, time-lapse ERT images, and available hydrologic data in a robust interpretation scheme to aid in quantifying seasonal variations in subsurface moisture content.

Download Full-text