KARAKTERISASI RESERVOAR MELALUI PEMODELAN STRUKTUR RESISTIVITAS MENGGUNAKAN INVERSI 2D DATA MAGNETOTELLURIK PADA DAERAH PROSPEK PANASBUMI DI LAPANGAN “G”-TELOMOYO, JAWA TENGAH; RESERVOIR CHARACTERIZATION BASED ON MODELLING RESISTIVITY STRUCTURE USING 2D INVERSION OF DATA MAGNETOTELLURIC AT PROSPECT AREA GEOTHERMAL “G” FIELD, TELOMOYO, CENTRAL JAVA

Striyuni, Nentis, Mochammad Nukman

2015 | Skripsi | FMIPA

“G” field, Telomoyo geothermal system is one of the Indonesia geothermal field that formed in basaltic magma environment. In the study area, hydrothermal alterations are found in quite wide area. These alteration rocks indicate geothermal potensial potential in this area. However, there is no advance investigation to find out how big is the geothermal potential in the study area. Thus, it is needed to do more research, such as using magnetotellurics (MT). MT method is one of the geophysical methods for mapping sub surface resistivity structures. In this study, 2D inversion of MT modelling were used. The inversion results were then integrated with geological and geochemical data to get the best conceptual model of Telomoyo geothermal system. Eleven measurements site were used in this experiment, divided into two lines, the first line oriented northwest – southeast and the second line oriented southwest – northeast. Based on the result of the 2D resistivity modelling, the low resistivity zone (? 21 ?m), found until 2500 m depth is identified as a cap rock. The middle apparent resistivity zone (21 ? 100 ?m), at the depth of 800 ? 4000 m, is identified as a reservoir. Thus, it can be concluded that MT method can be used to identify the reservoir of “G” field Telomoyo geothermal system.

Kata Kunci : magnetotelluric; geothermal system; 2D inversion; Telomoyo