Use of ISY EXO¹ probe for borehole resistivimetry

Geoscience Research Reports 49, 2016, pages 253–256

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Published online: 30 September 2016

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Abstract

The groundwater resistivity logging is one of the most useful methods for the applied hydrogeology research. This method provides information about the occurrence of hydraulically active fractures, the spots of groundwater inflow/outflow, and the direction of groundwater flow in the studied borehole.
The commonly used logging device is a complex and quite large equipment usually mounted on automotive chassis and therefore it is difficult to transport such device to poorly accessible sites like underground galleries. For this reason, the hydrochemical sonde ISY EXO¹ was experimentally used for conductivity logging in S-8 borehole (depth 50 m, diameter 57 mm). This borehole is located on the 12^th level of the uranium mine Rožná, 600 m below the surface where the underground research facility has been built.
The hydrochemical sonde ISY EXO¹ has a length of 650 mm, and 47 mm in diameter. It can measure up to 7 parameters using 4 coupled digital sensors (Fig. 1). It is suitable for boreholes with maximal water column height of 250 m. All measured data are stored in the internal memory or can be directly read via the cable connection. The conductivity sensor of ISY EXO¹ sonde was used for resistivity logging. The conductivity and resistivity have linear inverse relationship and these parameters can be easily recalculated vice versa. The device has an integrated pressure sensor and all measured values are paired with depth and time, so there is no need to measure the depth on a wireline. One second logging interval was set during the measurements in S-8 borehole.
The resistivity logging in borehole S-8 was performed under natural conditions as well as with induced pumping. The water level was lowered by maximum 1.2 m. Four sections with groundwater inflow were identified in borehole S-8 at depths 39.0, 42.1-42.7, 46.4, and 48.0 m. Two additional ones occur at depths 39.7 and 43.7 m, induced by pumping.
The results of resistivity logging and data from HiRAT sonde (High-Resolution Acoustic Televiewer) show good conformity of fracture localization (Fig. 2).
The experiment proved that ISY EXO¹ sonde can be used as an alternative to traditional resistivity logging devices. It brings an advantage of simple and easily transportable device in comparison to traditional equipment. Technical properties of this sonde are sufficient for measurements of the majority of hydrogeological boreholes.
This work was supported by RAWRA research project "Complex geological characterization of the URF Bukov". The HiRAT sonde was supported by project LO1406 "Institute of the clean technology of mining and use of energy raw materials".