The Blawan-Ijen volcanic complex is located in Bondowoso regencies, East Java province. The complex is expected to have geothermal system which is indicated by the occurrence of Blawan hotspring, acid lake on Ijen Crater and alterations. In 2017, measurements of gravity and magnetic methods have been conducted for the first time through the PITTA 2017 program. In 2018, further measurements are carried out to infill the previous data in order to strengthen the interpretation results. There are 151 stations obtained from each method until 2018. In this study, gravity method is used to detect the contrast density of an anomalous body while magnetic method is applied to discover the location of demagnetization zone. This paper presents the integration of both methods in geothermal exploration to determine the geothermal prospect area. The result of CBA and residual gravity indicated the existence of high gravity anomaly in the center to the southwest of the study area. Moreover, after processing RTP on magnetic data, there is the presence of low magnetic anomaly usually associated with demagnetization zone. Generally, the overall results supported one each other and pointed out the occurrence of the geothermal prospect possibly around the center of the study area.
Nowadays geothermal exploration in Indonesia is beginning to reach small islands, most of which have a prospect in the coastal area. This has influences on the MT data modelling due to the distortion of the electric field component caused by the extreme contrast of resistivity between land and sea. In these conditions, it is necessary to apply the correction of the coast effects. The seawater resistivity (0.3 Ωm) must be included in the 3-D MT modelling. A simulation was conducted to observe coast effects on 3-D MT modelling. Forward 3-D MT modelling is done to obtain synthetic data to compare homogeneous model and coast effects model. The simulation results show that the presence of seawater affects all MT data frequencies, but the most significant distortion occurs in the low frequency. The affected frequency range correlates with the distance between the MT station and seawater. If the distance of MT station to the sea is getting closer, then the disturbed frequency range is greater, and vice versa. The results of 3-D inversion of MT real data with the coast effects model are used to construct a conceptual model for geothermal systems in East Flores. The interpretation shows that the geothermal prospect area in the field is around Mount Anging. This research is expected to be a consideration for drilling recommendations and further development.
Integrated measurements of magnetic and gravity methods were carried out over Blawan-Ijen Geothermal Prospect area to discover the indication of prospect zone location more convincing. The acquisition was first conducted in 2017, followed by recent measurement in 2018 with a total of 151 stations for each method. In this research, Reduce to Pole for magnetic data was applied to identify the distribution of demagnetized rock which associated with reservoir zone. The prospect zone is usually indicated by low magnetic susceptibility value. Furthermore, to support the interpretation of prospect zone which usually located overlying the heat source, then 3D inversion of gravity data was conducted. Thus, by applying 3D inversion of gravity method, the distribution of density variation beneath the earth surface which represents the location of heat source can be obtained. The result of Reduce to Pole of magnetic data shows demagnetized zone with low magnetic susceptibility value located in the centre to the southeast at the study area. Moreover, 3D gravity data inversion delineates the existence of heat source indicated by high gravity anomaly which corresponds with demagnetized zone shown from magnetic data.
Blawan-Ijen geothermal prospect area is placed at Bondowoso, East Java. Geologically, the presence of geothermal system in this field is controlled by the huge ancient Kendeng caldera complex structure. The heat source of the geothermal system is predicted to be situated at the base of Kendeng caldera. Geomagnetic method was used for detecting the presence of the heat source. The high temperature zone as the main target of geothermal exploration mostly situated around the heat source location. The geomagnetic method was applied because of its ability to identify the magnetic variation of rocks such as the demagnetized zone which is caused by the high temperature condition in geothermal area especially in the center of geothermal reservoir. Geomagnetic survey was conducted in 2017 and 2018 with the total of 151 stations. The 3-D inversion of geomagnetic data was then carried out to image the subsurface magnetic variation which is representing the complex structure of geothermal system in this area. The subsurface magnetic variation structure revealed by 3-D inversion showed the distribution of demagnetization reservoir rock inside the Kendeng caldera which has low magnetic susceptibility. In the upper part of this layer that is a higher magnetic susceptibility layer which may associated with the clay alteration that is overlaying the geothermal reservoir in this area. Moreover, the very low magnetic susceptibility anomaly can be observed start from -1000 m elevation, which is interpreted as the heat source of the geothermal system in this area.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.