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"[ABSTRAKTelah diakukan penelitian guna mendelineasi zona prospek sistem panasbumi Daerah „P‟ menggunakan pemodelan multi dimensi data magnetotelurik terintegrasi data geologi dan geokimia. Daerah panasbumi „P‟ secara fisiografi termasuk pada Busur Banda Dalam tak bergunungapi disusun oleh komplek batuan malihan sekis berumur Perm-Trias. Gejala adanya sistem panasbumi pada daerah penelitian ditandai dengan kemunculan manifestasi permukaan berupa enam mata air panas bersuhu (37-67oC), pH (6-7) dan bertipe klorida-bikarbonat. Pembentukan sistem panasbumi diduga berkaitan dengan aktivitas tektonik kuat akibat tumbukan lempeng Pulau Seram dengan Lempeng Benua Australia (Plate Collision) yang memicu pembentukan batuan intrusi di kedalaman sebagai sumber panas. Guna mengetahui informasi subsurface daerah penelitian, dilakukan survei magnetotelurik. Selanjutnya hasil dari data MT akan diintegrasikan data geologi dan geokimia. Pengolahan data MT dimulai dari time-series data hingga mendapatkan kurva resistivitas-frekuensi dan fase, lalu dilakukan filtering noise, rotasi arah strike dan koreksi static shift untuk mendapatkan kualitas kurva MT baik. Selanjutnya dilakukan pemodelan inversi 1D, 2D dan 3D. Temperatur reservoir diduga sekitar 160-180oC termasuk temperatur sedang. Hasil penelitian ini memperlihatkan lapisan konduktif (<15 Ωm) dengan ketebalan ± 500-1000 m diindikasikan sebagai Clay Cap dari sistem panasbumi. Zona resistivitas tinggi (>300 Ωm) dan berbentuk updome, berada di bawah area kemunculan manifestasi (MAP1, MAP2, MAP3, MAP4, dan MAP5) mengindikasikan heat source berada di utara kemudian menerus ke arah tenggara membentuk updome. Model konseptual terpadu sistem panasbumi dibentuk dari integrasi data geologi, geokimia, dan geofisika. Sistem panasbumi daerah penelitian merupakan hidrotermal heat sweep plate collision dengan temperatur sedang, luas area prospek dan rekomendasi titik pemboran diperkirakan ± 3 km2 di sekitar zona Upflow, potensi sumber daya hipotetik dengan metode volume lump parameter menggunakan binary cycle ± 34 MWe.

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ABSTRACTA study for delineating geothermal system of prospect area “P” has been done by using multi-dimensional modeling of magnetotelluric data. Physiographycally, geothermal prospect of “P” area is located at non-volcanic Banda inner arc hosted by Malihan Sekis rock complex with Perm-Trias age. The existance of geothermal system in this area is indicated by the presence of thermal manifestations in form of 6 chloride-bicarbonate hot springs with temperature in the the range of 37 – 67oC, and pH of 6-7. The development of geothermal system is most probably associated with strong tectonic activity caused by the collision between Seram island plate and Australian plate that ignite the occurence of intrussive body as heat source. In order to know the subsurface information of prospect area, magnetotelluric (MT) survey has been done. The processing of MT data was started from time-series data, continued by noise filtering, rotation of strike orientation and static shift correction to obtain better MT curve. The data were then being inversed by means of 1-Dimensional, 2-Dimensional and 3-Dimensional inversion methods. Reservoir temperature is estimated to be around 160-180 oC and classified as moderate temperature. The result of MT data inversions shows the presence of conductive layer (<15 Ωm) with 500 – 1000 m thickness that is interpreted as clay cap og geothermal system. High resistivity zone (>300 Ωm) with updome shape appears underneath the manifestations occurence (MAP1, MAP2, MAP4, and MAP5), indicating that the heat source is located in northern part and elongate to souteast direction. The conceptual model of geothermal system was built based on integrated interpretation of geological, geochemical and geophysical data. The prospect area and recommendation of drilling location is estimated to be ± 5 km2 around upflow zone. Potential hypothetical resource with volume lump parameters method using binary cycle ± 34 MWe., A study for delineating geothermal system of prospect area “P” has been done by using multi-dimensional modeling of magnetotelluric data. Physiographycally, geothermal prospect of “P” area is located at non-volcanic Banda inner arc hosted by Malihan Sekis rock complex with Perm-Trias age. The existance of geothermal system in this area is indicated by the presence of thermal manifestations in form of 6 chloride-bicarbonate hot springs with temperature in the the range of 37 – 67oC, and pH of 6-7. The development of geothermal system is most probably associated with strong tectonic activity caused by the collision between Seram island plate and Australian plate that ignite the occurence of intrussive body as heat source. In order to know the subsurface information of prospect area, magnetotelluric (MT) survey has been done. The processing of MT data was started from time-series data, continued by noise filtering, rotation of strike orientation and static shift correction to obtain better MT curve. The data were then being inversed by means of 1-Dimensional, 2-Dimensional and 3-Dimensional inversion methods. Reservoir temperature is estimated to be around 160-180 oC and classified as moderate temperature. The result of MT data inversions shows the presence of conductive layer (<15 Ωm) with 500 – 1000 m thickness that is interpreted as clay cap og geothermal system. High resistivity zone (>300 Ωm) with updome shape appears underneath the manifestations occurence (MAP1, MAP2, MAP4, and MAP5), indicating that the heat source is located in northern part and elongate to souteast direction. The conceptual model of geothermal system was built based on integrated interpretation of geological, geochemical and geophysical data. The prospect area and recommendation of drilling location is estimated to be ± 5 km2 around upflow zone. Potential hypothetical resource with volume lump parameters method using binary cycle ± 34 MWe.]"

"Telah dilakukan penelitian guna mendelineasi zona reservoir daerah prospek geothermal "I" berdasarkan data audio magnetotellurik dan gravity, yang dipadu dengan data geologi dan geokimia. Penelitian ini difokuskan pada analisa zona reservoir menggunakan data geofisika audiomagnetotelurik dan gravity. Analisa geologi menggunakan metode remote sensing untuk memetakan struktur di permukaaan. Analisis geokimia digunakan untuk mengistimasi temperatur reservoir, jalannya fluida, dan karakteristik fluida pada sistem geothermal.Berdasarkan analisis remote sensing menggunakan ASTER DEM dan Landsat 8 dilakukan penarikan lineament secara pengamatan manual maka diketahui bahwa arah utama dari kelurusan yang berkembang di daerah prospek geothermal "I" adalah Barat Laut ndash; Tenggara 135 degrees. Kelurusan ini berkorelasi dengan kemunculan manifestasi mata air panas. Analisis data geokimia menunjukkan bahwa manifestasi manifestasi yang muncul di KMP-1, KMP-2, KMP-3, KMP-4,KMP-5, dan KP-2 memiliki pH netral. Geotermometer liquid menunjukan temperatur reservoar sekitar 180 C.Analisis data geofisika menggunakan 31 data titik ukur audio magnetotellurik dan 198 titik ukur gravitasi. Berdasarkan inversi 3D data AMT dan forward modelling gravitasi terdapat lapisan penudung cap rock dengan nilai resistivitas rendah le; 20 ?m dan densitas 2.2 gr/cc. Batuan cap rock sudah terlihat mulai dari permukaan dan menebal ke arah manifestasi mata air panas KH dan KM dengan kedalaman sekitar 500 meter dengan ketebalan 500 meter hingga 1000 meter. Di bawah batuan cap rock terdapat batuan reservoir dengan nilai resistivitas sedang >20 s.d 65 ?m dan densitas 2,67 gr/cc. Batuan ini diinterpretasikan sebagai respon dari Jatiluhur shale. Lapisan heat source berada di bawah reservoir dengan nilai resistivitas >100 ?m. Top of Reservoir TOR diperkirakan berada pada kedalaman 800 m dari permukaan yang teridentifikasi pada elevasi 0 meter. Luas zona prospek sebesar 0.5 km2 yang berada tepat di bawah Gunung "I".

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The research had been conducted to delineate reservoir zone in geothermal prospect area ldquo I rdquo based on audio magnetotelluric and gravity data supported by geology and geochemistry data. This research used audiomagnetotelluric and gravity method to analize reservoir zone. Geology analisys using remote sensing method are used to map the structure on the surface. Geochemical analysis are used to estimate reservoir temperature, fluid flow, fluid chraracteristic fluid in the geothermal system.Based on the remote sensing analysis by using ASTER DEM and Landsat 8 map in manual observation, the main direction of lineament developed in area ldquo I rdquo is West North ndash East South 135 degrees. This lineament is corelated to the appearance of hot springs. The geochemical data analysis shows that hot spring manifestation is the outflow type manifestation which appear in KMP 1,KMP 2, KMP 3, KMP 4, KMP 5, and KP 2 have neutral pH. Liquid geothermometer shows that the reservoir temperature is about 180 C.The analysis of geophysics data uses 31 audio magnetotelluric stations and 198 gravity stations.

Based on 3D AMT data inversion and gravity forward modelling, there is cap rock layer with low resistivity le 20 m and density 2.2 gr cc. The Cap rock layer finds in the surface and thickened toward hotspring KH and KM manifestation with depth about 500 meters with thickness 500 meters up to 1000 meters. Under cap rock layer, there is reservoir rock layer with medium resistivity 20 s.d 65 m and density 2,67 gr cc. This rock is interpreted as the response from Jatiluhur shale. Heat source layer is located underneath reservoir rock layer with resistivity value 100 m. Top of Reservoir TOR is estimated in depth of 800 m from the surface and identified at elevation 0 meter. The prospect area is about 0.5 km2 which located below ldquo I rdquo Mountain."

"Eksplorasi pada daerah prospek geothermal bertujuan untuk mencari zona reservoir, kriteria zona reservoir yang baik yaitu memiliki temperatur, tekanan dan permeabilitas yang tinggi. Penentuan zona reservoir perlu dilakukan kegiatan survei terpadu 3G meliputi survei geologi, geokimia dan geofisika. Pada lapangan geothermal daerah "F" menggunakan metode remote sensing untuk memetakan struktur dan alterasi di permukaaan. Analisis geokimia digunakan untuk mengetahui karakteristik sistem geothermal dan analisis geofisika digunakan untuk memetakan kondisi sistem geothermal di bawah permukaan. Berdasarkan analisis remote sensing dengan menggunakan teknik band combination secara pengamatan manual diketahui bahwa arah utama dari kelurusan daerah penelitian "F" adalah Barat Laut ndash; Tenggara. Kelurusan ini berkorelasi dengan kemunculan manifestasi permukaan. Analisis data geokimia menunjukkan bahwa pemetaan zona upflow di tunjukkan oleh kemunculan manifestasi Kaipohan dan hot spring tipe sulfat SO4 , sedangkan zona outflow di tinjukkan dengan kemunculan manifestasi hot spring dengan tipe fluida bikarbonat HCO3 . Data geofisika menggunakan 46 data titik ukur magnetotellurik yang selanjutnya di analisis melalui pola kurva splitting, arah elongasi polar diagram serta melakuian inversi 3D. Berdasarkan analisis tersebut maka diketahui struktur lapisan bawah permukaan dari clay cap dengan nilai resistivitas rendah, reservoir dan heat source. Hasil akhir dari penelitian ini juga akan memberikan implikasi terhadap upaya peningkatan Drilling Success Ratio DSR dalam pemboran dan mengurangi risiko pada tahapan eksplorasi.

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Exploration in the geothermal prospect area aims to find the reservoir zone, a good reservoir zone criterion are has high temperature, pressure, and permeability. Determination of reservoir zones needs to be carried out by a 3G integrated survey activity covering geological, geochemical and geophysical surveys. In the geothermal field 39 F 39 , survey is conducted using a remote sensing method to map the structure and alteration on the surface. Geochemical analysis is used to determine the characteristics of geothermal systems and geophysical analysis used to map the condition of geothermal systems beneath the surface. Based on remote sensing analysis by using band combination technique by manual observation, it is known that the main direction of research area ldquo F rdquo straightness is Northwest Southeast. This straightness correlates with the appearance of surface manifestations.

Analysis of geochemical data showed that upflow zone mapping was demonstrated by the emergence of kaipohan and hot spring type sulfate manifestations SO4 , while the outflow zone was presented by the appearance of hot spring manifestation with bicarbonate fluid type HCO3 . Geophysical data uses 46 data of magnetotellurik measuring point which then analyzed by splitting curve pattern, direction of polar diagram elongation, and 3D inversion. Based on these analyzes, it is known that the subsurface structure of clay cap has low resistivity value, reservoir, and heat source. The final results of this study will also provide implications for improving Drilling Success Ratio DSR in drilling and reducing risks at the exploration stage."

"Telah dilakukan penelitian guna delineasi zona prospek sistem panasbumi daerah ldquo;Z rdquo; menggunakan permodelan tiga Dimensi magnrtotellurik didukung data terpadu berupa geologi dan geokimia serta terintegrasi data gravitasi. Daerah panasbumi ldquo;Z rdquo; dalam tatanan tektoniknya termasuk pada jalur backarc Sumatera, tepat pada salah satu segmen sesar Sumatera bagian selatan, disusun oleh batuan vulkanik dan sedimen klastik yang berumur Tersier hingga Kuarter Andesit-Basalt . Gejala adanya sistem panasbumi pada daerah penelitian ditandai dengan kemunculan manifestasi permukaan berupa alterasi dan lima mata air panas bersuhu 44,4 - 92,5 oC, pH 8,19 - 9,43 dan bertipe bikarbonat, sulfat-bikarbonat, serta sulfat-klorida. Pembentukan sistem panasbumi dipengaruhi oleh aktivitas tektonik menyerong oblique antara lempeng Samudera India dan Lempeng Kontinen Eurasia searah dengan pola sesar Sumatera. Berdasarkan analisis air panasbumi temperatur reservoir diambil melalui perhitungan geothermomether SiO2 Fournier 1977 , Na-K Giggenbach 1988 , Na-K-Ca, diagram Na-K-Mg serta diagram Enthalphy - Cloride Mixing Model berkisar 145 - 155oC, termasuk dalam sistem panas bumi bertemperatur sedang. Berdasarkan inversi tiga dimensi data MT didapatkan kedalaman Top of Reservoar TOR sistem panasbumi daerah ldquo;Z rdquo; sekitar 400 m elevasi 50 mdpl sedangkan berdasarkan forward modeling data gravitasi lintasan 2 dimensi diperkirakan sumber panas berupa cooling instrusion diperkirakan batuan gabro ; resistivitas ge; 450 ?m ; densitas 2,95 - 3,15 gr/cc dan reservoar berupa batupasir resistivitas 50 - 250 ?m ; densitas 2,60 gr/cc . Sistem panasbumi daerah penelitian termasuk jenis tektonik fracture zone dengan temperatur sedang dengan luas daerah prospek sekitar 7,5 km2.

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A study for delineating geothermal system of prospect area ldquo Z rdquo has been done by using tree dimension modeling of magnetotelluric supported unified data just like geological and goechemical and integrated gravity data. Geothermal area ldquo Z rdquo in tectonic setting included in Sumatra volcanic backarc, right on one of the southern part of Sumatra fault segment. Compodes by volcanic and clastic sendimentary rock are Tertiary to Quarternary Andesite Basalt. The existance of goethermal system in this area is indicated by the presence of thermal manifestation in form of alteration and five hot springs temperature in the ranges 44.4 ndash 92.5 oC, and pH 8.19 ndash 9.43 and type of fluida are bicarbonate, sulphate bicarbonate, and sulfate chloride. The development of geothermal system is affected by tectonic oblique between the Indian Ocean plate and the Eurasian Contenent Plate direction of the Sumatra fault patterns.

Based on the analysis of geothermal water reservoir temperature are taken through the calculation geothermometer SiO2 Fournier 1977, Na K Giggenbach 1988 , Na K Ca, Na K Mg diagram and Enthalpi Mixing Cloride Model range 145 ndash 155 oC, classified as intermediate temperature. Base on a three dimensional inversion of the magnetotelluric data obtained depth Top of Reservoir TOR geothermal system area ldquo Z rdquo about 400 m elevation 50 meters above sea leavel , while based on the two dimensional of the gravity data predicted heat sources such as cooling instrusion estimated gabbro density 2,95 ndash 3,15 gr cc and reservoar such as sandstone resistivity 50 ndash 250 m density 2,60 gr cc . The Geothermal systems of research area classified as the type of intermediate temperature tectonic fracture zone with prospect area about 7,5 km2."

"Telah dilakukan penelitian guna mendelineasi sistem panas bumi lapangan geothermal ldquo;H rdquo;. Penelitian ini menggunakan metode remote sensing untuk memetakan struktur dan alterasi di permukaan. Analisis geokimia digunakan untuk mengetahui karakteristik sistem panas bumi dan analisis geofisika digunakan untuk memetakan kondisi sistem panas bumi di bawah permukaan. Berdasarkan analisis remote sensing dengan teknik band combination secara pengamatan manual menunjukkan bahwa arah utama dari kelurusan - kelurusan yang berkembang di daerah penelitian ldquo;H rdquo; adalah Barat Laut - Tenggara dan Barat Daya - Timur Laut sesuai dengan Peta Geologi Regional yang berkorelasi dengan kemunculan beberapa manifestasi. Analisis remote sensing juga menemukan 1 lokasi yang diduga merupakan alterasi di permukaan. Analisis data geokimia dilakukan terhadap 12 manifestasi menunjukkan bahwa mata air panas SL-1, SL-2, SLM-1, SLM-2, HTS-1, HTS-2, HTS-3, TBK, TLH-1, TLH -2, TLH-3 dan TLH- 4 merupakan manifestasi tipe outflow. Berdasarkan diagram segitiga ternary Na - K - Mg, diagram Na-K/Mg-Ca, diagram Enthalpy - Chloride Mixing Model, geothermometer Na/K menunjukkan temperatur reservoar adalah sekitar 210 C - 240 C dan dapat dikategorikan ke dalam sistem geothermal moderate to high temperature. Analisis Inversi 3-D Data MT menggunakan 66 data titik ukur. Berdasarkan inversi 3-D Data MT diketahui bahwa lapisan clay cap dengan nilai resistivitas rendah le; 10 ?m tersebar di Selatan dengan ketebalan 500 meter hingga 1000 meter. Lapisan reservoar terletak di bawah clay cap dengan nilai resistivitas >10 - 65 ?m. Base of Conductor BOC diperkirakan berada pada kedalaman 700 meter dengan updome berada di antara Sesar Wairutung dan Sesar Banda. Berdasarkan peta BOC diperoleh luas area prospek geothermal sekitar 16.5 km2.

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The study of ldquo H rdquo geothermal field has been conducted to delineate their geothermal system. This study uses remote sensing method for mapping structure and alteration on the surface. Geochemical analysis is used to determine the characteristics of geothermal system and geophysical analysis is used to interpret the condition of geothermal system of sub surface. Based on remote sensing analysis using band combination technique with manual observation indicates that the main direction of the developed lineaments in the research area H is Northwest Southeast and Southwest Northeast in accordance with Regional Geological Map correlated with the appearance of several manifestations. The remote sensing analysis also found 1 suspected alteration site on the surface. Analysis of geochemical data was performed on 12 manifestations shows that hot springs SL 1, SL 2, SLM 1, SLM 2, HTS 1, HTS 2, HTS 3, TBK, TLH 1, TLH 2, TLH 3 and TLH 4 are outflow manifestations type.

Based on the diagram of the ternary triangle Na K Mg, Na K Mg Ca diagram, Enthalpy Chloride Mixing Model diagram, Na K geothermometer estimates the reservoir temperature is about 210 C 240 C and can be categorized into the moderate to high temperature geothermal system. Analysis of inversion 3 D MT data using 66 data points measurement. Based on 3 D inversion MT data is known that clay cap layer with low resistivity value le 10 m spread in South with thickness 500 meter to 1000 meter. The reservoir layer is located under clay cap with resistivity value 10 m 65 m. Base of Conductor BOC is estimated to be at depth of 700 meters with an updome located around Wairutung Fault Banda Fault. Based on BOC, the prospectable area of geothermal system is about 16.5 km2."

"Dalam beberapa dekade, akuisisi MT biasanya dilakukan dalam bentuk profil lintasan 2D. Namun pemodelan inversi 2D memiliki kekurangan terutama terkait dengan keberadaan struktur yang lebih kompleks 3D strike . Ambiguitas ini termasuk dalam pemilihan mode yang digunakan TE atau TM . Ambiguitas ini dapat menyebabkan kesalahan dalam interpretasi. Ambiguitas data seperti yang terjadi pada inversi 2D dapat diatasi dengan menggunakan program inversi 3D.Inversi MT 3D dilakukan dengan menggunakan dengan menggunakan perangkat lunak Mod3DEM dengan algoritma NLCG Non Linear Conjugate Gradient dan sudah memasukkan faktor topografi. Data input yang digunakan dalam inversi 3D adalah sebanyak 92 titik, dengan range frekuensi 320 ndash; 0.01 Hz. Pengolahan data menggunakan rotasi principal axis dan koreksi statik menggunakan data TDEM. Selain itu, data pendukung lain yang digunakan dalam penelitian ini adalah data geokimia dan data geologi. Berdasarkan hasil inversi 3D MT, Karakteristik sistem geothermal lapangan ldquo;INARA rdquo; terlihat dengan batuan penudung memiliki resestivitas rendah 80 ohm-m. Top of reservoir berada di ketinggian 500 meter dari MSL dengan heat source berada di bawah puncak gunung WL. Dari hasil perhitungan geothermometer silika dan diagram entalphy-Cloride mixing, diperoleh temperatur reservoir daerah prospek panas bumi ldquo;INARA rdquo; adalah 200 oC. Sedangkan berdasarkan geothermometer CO2, temperatur reservoir daerah prospek panas bumi ldquo;INARA rdquo; adalah 260 oC dan masuk dalam kategori high temperature >225 oC.

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Within a few decades, MT acquisition is used to be done in a 2D track profile. However 2D inversion modeling has its drawbacks mainly related to the existence of the existence of complex structures 3D strike . This will bring ambiguity that can lead to errors in interpretation. Data ambiguity as occurs in 2D inversion can be overcome by using 3D inversion program.The software used in MT 3D Inversion is Mod3DEM with NLCG Non Linear Conjugate Gradient algorithm and has included topography factor. The input data used in 3D inversion is 92 points, with frequency range 320 0.01 Hz. The data processing used principal axis rotation and static corrected by TDEM data. The other supporting data used in this study are geochemical data and geological data.

Based on the 3D MT inversion results, the characteristics of the INARA geothermal field system are seen with low residence rocks 80 ohm m. Top of the reservoir is at an altitude of 500 meters from MSL with the heat source is under the peak of WL mountain. From the calculation of silica geothermometer and entalphy cloride mixing diagram, it is known the reservoir temperature of geothermal prospect region INARA is 200 oC. While based on CO2 geothermometer, the reservoir temperature of geothermal prospect region INARA is 260 oC and included in high temperature 225 oC."

"Lapangan geotermal X berada di area gunung A yangmana berdasarkan data geologi ditemukan adanya manifestasi berupa hot spring dan fumarole. Pengukuran MT dilakukan untuk mengetahui persebaran resistivity batuan di bawah permukaan. Pengolahan data MT dilakukan dari analisis time series dan filtering noise kemudian dilakukan Transformasi Fourier dan Robust Processing. Setelah itu baru dilakukan crosspower untuk menyeleksi data sehingga output dari proses ini berupa kurva MT. Setelah didapatkan kurva MT dilakukan koreksi statik dikarenakan kurva TE dan TM terjadi shifting. Untuk proses akhirnya baru dilakukan inversi 2D dan inversi 3D. setelah itu dilakukan perbandingan antara 2D dan 3D. Wilayah interest lapangan X berada di lintasan AA dan lintasan AB. Berdasarkan analisis 3D diidentifikasi bahwa zona alterasi menipis di wilayah upflow dan menebal ke arah outflow yangmana sesuai dengan teori. Wilayah upflow dapat diketahui dengan melihat manifestasi berupa fumarole.

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The geothermal field X is located in the area of Mount A which based on geological data found the presence of hot spring and fumarole manifestations. MT measurements were carried out to determine the distribution of rock resistivity in the subsurface. MT data processing is starts from time series analysis and noise filtering then Fourier Transform and Robust Processing are performed. After that, crosspower is done to select data so that the output of this process is an MT curve. After got the MT curve then a static correction is done because the TE and TM curves are shifting. For the final process are 2D inversion and 3D inversion. After that make a comparison between 2D and 3D. The area of interest in field X is on the line AA and line AB. Based on the 3D analysis, it was identified that alteration zones thinned in the upflow region and thickened towards the outflow which is make sense with the theory."

"Fase eksplorasi geotermal masih memiliki resiko yang tinggi dan rintangan yang besar bagi industri geotermal. Tujuan utama dari eksplorasi adalah penentuan lokasi pemboran. Kriteria kesuksesan target pemboran adalah area yang memiliki temperatur dan permeabilitas yang tinggi. Temperatur berasosiasi dengan keberadaan sumber panas (heat source) menjadi target dalam penelitian ini dan jumlah energi termal yang tersimpan, sedangkan permeabilitas berhubungan dengan keberadaan struktur geologi baik patahan maupun kekar yang terisi fluida yang dapat menjadi media perpindahan energi panas. Pada penelitian sebelumnya gambaran dari boundary bawah permukaan masih belum tergambar dengan jelas dikarenakan keterbatasan data MT, dan belum dilakukannya analisis data gravity. Untuk mendapatkan informasi tersebut, penelitian ini dilakukan dengan analisis First Horizontal Derivative (FHD) dan Second Vertical Derivative (SVD) serta hasil inversi 3-Dimensi Magnetotelluric (MT) diaplikasikan pada penelitian ini untuk memetakan struktur resistivitas bawah permukaan, juga diketahui daerah reservoir dari Base of Conductor (elevasi BOC di 2000m). Selanjutnya diintegrasikan hasil dari Fault Fracture Density (FFD) untuk melihat sejauh mana pengaruh manifestasi terhadap struktur di permukaan serta gravity untuk mengindentifikasi zona permeabel, agar dapat membantu dalam pembangunan model konseptual serta deliniasi prospek area. Dari hasil analisis terpadu kemudian dapat ditentukan rekomendasi target pemboran. Terdapat 2 titik sumur rekomendasi dibagian utara dan barat Gunung W. Hasil akhir penelitian akan memberikan informasi atas upaya mengurangi risiko pada fase eksplorasi dan meningkatan rasio kesuksesan dalam pemboran. 

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The geothermal exploration phase still has a high risk and a large obstacle for the geothermal industry. The main objective of exploration is to determine the location of the drilling. Success criteria for drilling targets are areas that have a high temperature and permeability. The temperature associated with the presence of heat sources is the target in this study and the amount of thermal energy stored, while permeability is related to the presence of geological structures, both fractures and burly filled with fluid which can be a medium of heat energy transfer. In previous studies, the picture of the subsurface boundary was not clearly drawn due to the limitation of MT data, and gravity data analysis had not been carried out. To obtain this information, this study was conducted with First Horizontal Derivative (FHD) and Second Vertical Derivative (SVD) analysis and the results of 3-Dimensional Magnetotelluric (MT) inversion were applied in this study to map the subsurface resistivity structure, also known the reservoir area of the base. of Conductor (BOC elevation at 2000m). Furthermore, the results of the Fault Fracture Density (FFD) are integrated to see the extent of the influence of manifestations on the structure on the surface and gravity to identify the permeable zone, in order to assist in the construction of a conceptual model and delineation of prospect areas. From the results of the integrated analysis can then be determined by drilling target targets. There are 2 recommended well points in the north and west of Mount W. The results of the study will provide information on efforts to reduce risk in the exploration phase and increase the success ratio in drilling. "

"Daerah prospek Geotermal Gunung ST merupakan tipe gunungapi strato yang berada pada lingkungan vulkanik kuarter dan memiliki manifestasi berupa fumarol dan mata air panas sebagai indikasi sistem geotermal. Pengolahan data MT dilakukan untuk mengetahui distribusi resistivitas batuan di bawah permukaan dalam menentukan komponen sistem geotermal. Proses akhir dari pengolahan data adalah dilakukan pemodelan MT inversi 3D. Daerah interest untuk pembuatan model konseptual berada pada lintasan 1. Berdasarkan analisis integrasi dengan berbagai data diidentifikasi bahwa zona konduktif menipis di wilayah upflow yaitu di puncak Gunung ST dan menebal menuju outflow yaitu di bagian relatif utara dan selatan dari Gunung ST. Struktur geologi yang mengontrol sistem geotermal di Gunung ST adalah sesar St berarah barat daya – timur laut yang letaknya memotong daerah prospek. Karakteristik sistem geotermal daerah penelitian dapat teridentifikasi, yang meliputi: clay cap sebagai lapisan penudung terletak pada kedalaman 400 m dengan ketebalan bervariasi mencapai 3000 m, reservoir di kedalaman 1000 m dengan ketebalan 1000 – 1600 m, dan heat source pada kedalaman lebih dari 4000 m dari permukaan tanah.

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The geothermal prospect area of Mount ST is a stratovolcanic type located in a quarter volcanic environment and has manifestations in the form of fumaroles and hot springs as an indication of the geothermal system. MT data processing is carried out to determine the distribution of rock resistivity below the surface in determining the components of the geothermal system. The final process of data processing is 3D inversion MT modelling. The area of interest for conceptual modelling is on track 1. Based on the integration analysis with various data, it is identified that the conductive zone is thinning in the upflow area, namely at the top of Mount ST and thickens towards outflow, namely in the relatively north and south of Mount ST. The geological structure that controls the geothermal system on Mount ST is the southwest-northeast trending St fault which intersects the prospect area. The characteristics of the geothermal system in the study area can be identified, which include: clay cap as a covering layer located at a depth of 400 m with a thickness varying up to 3000 m, a reservoir at a depth of 1000 m with a thickness of 1000 – 1600 m, and a heat source at a depth of more than 4000 m from ground level."

"Pada kondisi pemanfaatan geotermal yang sedang direncanakan untuk meningkat, tahap eksplorasi menjadi tahap yang sangat penting dan dilakukan di banyak lokasi. Daerah prospek geotermal “X” belum banyak pihak yang melangsungkan tahap eksplorasi. Dalam penelitian ini, struktur daerah penelitian yang kemungkinan menjadi jalur bagi fluida geotermal didelineasi menggunakan data gravitasi darat dan juga data gravitasi satelit. Penggunaan dua jenis data ini bertujuan untuk mengetahui perbedaan yang dimiliki oleh kedua jenis data dan untuk mengetahui data gravitasi mana yang memilki akurasi paling tinggi. Dilakukan pemisahan anomali pada data gravitasi darat dan satelit menggunakan metode Polynomial TSA orde 1 dan orde 2 serta Spectrum Analysis Bandpass Filter. Kemudian data gravitasi juga diterapkan filter First Horizontal Derivative (FHD) dan Second Vertical Derivative (SVD) untuk delineasi struktur. Inversi 3 dimensi juga diterapkan pada data gravitasi darat dan gravitasi satelit karena inversi 3 dimensi lebih objektif dalam menampilkan kondisi vertikal dan lateral suatu daerah. Dari penerapan berbagai metode tersebut didapatkan kondisi daerah penelitian berupa struktur graben dengan litologi aluvium yang dikelilingi oleh batuan berdensitas tinggi seperti granit, diorite, dan metasedimen. Data gravitasi darat diintegrasi dengan data MT, data geologi, dan geokimia karena data gravitasi darat memiliki akurasi yang lebih tinggi dibandingkan dengan data gravitas satelit, yang dibuktikan dengan kesesuaian sesar geologi dengan pola anomali gravitasi yang ada. Dari hasil integrasi, didapatkan zona resistif terduga heat source pada bagian barat daya daerah penelitian diindikasikan sebagai batuan diorit karena berdasarkan inversi 3 dimensi zona tersebut memiliki anomali gravitasi tinggi. Selain itu, zona konduktif yang berada di tengah daerah penelitian merupakan lapisan aluvium karena memiliki anomali gravitasi rendah. Dari analisis FHD dan SVD didapatkan sesar yang membatasi lapisan beranomali gravitasi tinggi dengan anomali gravitasi rendah yang mengindikasikan keberadaan graben, serta sesar tersebut menjadi jalur fluida geothermal karena terdapat manifestasi air panas di ujung sesar.

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Under the conditions of geothermal utilization that is being planned to increase, the exploration stage becomes a very important stage and is carried out in many locations. The geothermal prospect area "X" haven’t carried out by many parties for the exploration stage. In this study, the structure of the study area that is likely to be a pathway for geothermal fluids was delineated using ground gravity data and also satellite gravity data. The use of these two types of data aims to find out the differences between the two types of data and to find out which gravity data has the highest accuracy. Anomaly separation for ground and satellite gravity data were performed using the Polynomial TSA method of order 1 and order 2 and spectrum analysis bandpass filter. Then the First Horizontal Derivative (FHD) and Second Vertical Derivative (SVD) filters is applied to the gravity data for structural delineation. 3-dimensional inversions are also applied to ground gravity and satellite gravity data because 3-dimensional inversions are more objective in displaying the vertical and lateral conditions of an area. From the application of these various methods, the condition of the research area was obtained in the form of graben structures with alluvium lithology surrounded by high-density rocks such as granite, diorite, and metasedic. Ground gravity data is integrated with MT data, geological data, and geochemistry because ground gravity data have higher accuracy compared to satellite gravitas data, which is evidenced by the suitability of geological faults with existing gravitational anomalous patterns. From the integration results, a suspected heat source resistive zone in the southwestern part of the study area was indicated as a diorite rock because based on the 3-dimensional inversion the zone had a high gravitational anomaly. In addition, the conductive zone in the middle of the study area is an alluvium layer because it has a low gravity anomaly. From the analysis of FHD and SVD, it was found that faults limit the high-gravity patterned layer with low gravity anomalies indicating the presence of grabens, and the fault became a geothermal fluid path because there was a manifestation of hot water at the end of the fault."