Geoelectrical model of geothermal spring in Ie Jue Seulawah deriving from 2D VLF-EM and DC resistivity methods

Abstract

Seulawah Agam is one of the volcanic areas in Aceh province, Indonesia, which planned for a powerplant constriction with an energy capacity expected to be approximately 230 MWe. This volcano has seven manifestations in the form of craters, hot water, and heated soil. The hydrothermal system in this volcano is controlled by a fault system which acts as a medium for the entry and exit of fluids. Therefore, understanding the local geology is required for geothermal power plant development, especially for the determination area for injection and production wells. In this research, we use the Very Low-Frequency Electromagnetic (VLF-EM) methods combined with electrical resistivity tomography data on the Ie Jue manifestation area to determine the shallow structure related to the manifestation. The VLF was made for 4 profiles with 700 m length for each VLF-EM profile and 300 m for electrical resistivity lines. We utilized the Karous Hjelt filter for qualitative interpretation, while Occam's algorithm was applied for 2D inversion of data for quantitative analysis of VLF-EM data. Based on the current density model, several vertical conductive anomalies can be well demonstrated at a distance of 300-400 m from the four VLF profiles. The conductive anomaly can also be seen in the resistivity data from the electrical resistivity. The results of the Occam model show that the depth of faults and fractures is seen at 30 m depth with low resistivity (below 100 Ωm). This anomaly is generally associated with outcrops in the field, such as fumarole and warm ground on the east side of the manifestation area. In addition, the 2D inversion model of VLF also shows the contrast of several fracture zones as a place for fluid to enter and exit the Seulawah volcano. Therefore, based on our result, it can be summed up that this method is effectively applied to geothermal in high terrain areas such as in Indonesia and can be used to suggest safe locations for injection wells and production of geothermal drilling.

Applying Deep Electrical-Resistivity Tomography Techniques for the Exploration of Medium- and Low-Geothermal Energy Resources

“…In the case of high-and medium-enthalpy geothermal systems, these present great variations in their resistivity/conductivity structure, usually associated with the occurrence of fluids but also with the presence of anomalous concentrations of hydrothermal minerals. The existence of particular fluids, such as saline fluids or meteoric water in rocks, results in enhanced electrical conductivity to a greater or lesser extent, depending on the characteristics of this fluid [33][34][35]. In these cases, ERT methods are an important source of information, but they also constitute a great help in those surveys where the initial thermal evidence is not so clear, but a possible state of fracturing or structural disposition could indicate the potentiality of geothermal exploitation at different scales.…”

Identifying the structure as a hot water outflow path using gravity in Jatimulyo, South Lampung

“…To tap into this remarkable resource, geophysicists employ advanced techniques to image and characterize subsurface layers. Geophysical methods such as magnetotellurics [9], gravity [10], magnetic [6,8] , and direct current (DC) resistivity and very low frequency (VLF) [11]serve as the critical first step in identifying and characterizing geothermal systems. In this discussion, we'll delve into the fascinating world of geophysical exploration, unveiling the ingenious techniques that reveal the hidden, underground pathways of scalding water.…”

Unveiling Subsurface Characteristics of Cliff Land in Sibang, Bali Through Geoelectric Investigation

“…By employing advanced geophysical techniques such as electrical resistivity tomography (ERT) and electromagnetic induction (EMI). An investigation will be carried out to map the subsurface structure, moisture distribution, and lithological variations along the cliff face [15][16] [8][17] [18]. Therefore, conducting geoelectrical studies in Sibang can provide better insights into subsurface soil characteristics on cliffs, which is crucial for infrastructure development and environmental conservation in the region.…”