Electrical Resistivity Imaging technique to delineate coal seam barrier thickness and demarcate water filled voids

Abstract

Exploration and exploitation of coal seams is one of the major resources for the energy sector in any country but at the same time water filled voids/water logged areas in the old workings of these seams are very critical problems for the coal mining industry. In such situations, disasters like inundation, landslides, collapsing of the old seams may occur. In this regard, it is necessary to find out the water saturated/water filled voids and zones in the mining areas. Since no established technique is available to find such zones, an experimental study using Electrical Resistivity Imaging (ERI) has been carried out in one of the coal mining areas near Dhanbad, to find out the feasibility of finding the barrier thickness and the water logged area in underground coal mines. The area under study forms part of Jharia coalfield in Dhanbad district, Jharkhand state. The coal bearing rocks of Barakar Formation of Lower Permian age (Gondwana period) occur in the area under a thin cover (10 m to15 m) of soil and or alluvium. Coal bearing Barakar Formations consist mainly of sandstone of varying grain size, intercalation of shale and sandstone, grey and carbonaceous-shale and coal seams.Since the water saturation reduces the resistivity of a formation to a large extent, water filled voids and old coal workings are expected to have significant resistivity contrast with the surrounding host rock. Hence, ERI technique was applied in such an environment as this technique uses high-density data acquisition both laterally and vertically by using multiple number of electrodes. Along with ERI, mise-à-la-masse (also called charged body) technique was also employed at one of the promising sites to find out the connectivity of water logged areas and also detection of these old workings from the surface measurements was analyzed. The interpreted 2D resistivity sections have clearly indicated the water bearing zone(s) along the profile which was well confirmed with the existing water level in the nearby borewells. On the other hand, this technique did not identify the size of the coal pillar and gallery (air filled voids), which might be due to the small size of the voids (i.e. about 2 m x 2 m) below a depth of 15m and more but have indicated altogether as a high resistive zone ranging from 600-1000 Ohm-m.

Comparative study of Wenner and Schlumberger electrical resistivity method for groundwater investigation: a case study from Dhule district (M.S.), India

“…The application of resistivity is also used in coal and mineral exploration, but commonly, the method is used for groundwater exploration (Zohdy et al 1974;Ayolabi 2005;Krishnamurthy et al 2009;Kumar et al 2011;Swartz 1937; Udaya Laxmi and Ramadass 2009). Studies on dykes have been carried out to classify the dykes as carrier or barrier for groundwater flow (Erram et al 2010;Singh and Jamal 2002;GSDA 2001).…”

Integrated Geophysical and Geochemical Analyses for Assessment of Potential Coal Prospects in Tirah Area, Khyber Pakhtunkhwa, Pakistan

“…Every material has its own resistivity values, and variations in resistivity values are used to interpret the lithology. Electrical resistivity imaging (ERI) has been proven to be a reliable and helpful method in coal exploration and, afterwards, the exploitation of coal deposits [42][43][44]. From the published data, it is concluded that the coal seams have a resistivity value ranging from 100 Ωm to 800 Ωm [45][46][47].…”

The use of Geoelectrical Methods for Delineation of Lead-Zinc Mineralization: A Case Study of Eziama Village, Abia State, South- East, Nigeria

“…In this study, electrical resistivity method of geophysics is used to delineation of zinc deposit in complex geological environments, and has been adopted by several authors such as: Krishnamurthy [3], Nthaba [4]. This is because it find its usefulness in mapping out vertical and the lateral extents of the zinc deposit with estimated overburden thickness.…”