The capability of detailed study of coal- and orebearing structures using electrical resistivity tomography (ERT) by means of “well boresurface” observation system

Abstract

Coal open-cuts of Khabarovsk and Primorskii krai are characterized by multiple coal beds of small thickness. Important is the task to evaluate structural architecture of landslide blocks distinguishing insecure beds of small thickness. In detailed study of ore deposits it is also needed to distinguish thin beds and rock-fracture zones. Therefore, in order for detailed study of such structures, it is proposed to develop a ERT technology with the use of “well bore-surface” observation system. On this stage, only theoretical justification of proposed technology is given. In order to ascertain the technology capability, the calculation of apparent resistivities for three-layer structures with various correlations of geometrical and electrical parameters was conducted. Calculations were performed with uniform spacing of 20 electrodes in a well bore and 40 of them on the surface with polling of Wenner and Schlumberger fourelectrode arrays, axial array and their three-electrode designs. Regularities of electrical field for three fragments of apparent resistivity section were established based upon the analysis of modeling results: electrodes only on the surface (horizontal profile), electrodes in the well bore (vertical profile), electrodes in the well bore and on the surface (mixed profile). Outstanding interest is represented by anomalous areas of mixed profile which are described by new regularities of the field and criteria of distinguishing beds of small thickness. Theoretically it has been demonstrated that new technology is effective with distinguishing beds of small thickness on different depths of geological section.