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"Terdapat dua prospek panas bumi di sekitar Gunung Slamet, yaitu prospek Guci di sebelah barat laut dan prospek Baturaden di sebelah selatan dari Gunung Slamet. Menjadi sangat menarik untuk mengetahui hubungan kedua prospek tersebut, apakah prospek tersebut merupakan dua daerah prospek yang dipisahkan oleh tinggian low permeability barrier sehingga tidak akan terjadi interferensi diantara kedua prospek? Dengan melakukan deliniasi zona permeabel berdasarkan analisis data magnetotelurik dan data gravity dikorelasikan dengan data struktur geologi permukaan dan data manifestasi permukaan yang ada, diharapkan dapat mengetahui hubungan diantara kedua prospek tersebut. Dalam penelitian ini dilakukan pemrosesan dan pemodelan data geofisika menggunakan metode magnetotelurik inversi 2-D dan metode gravity 2-D forward. Pemodelan ini sangat efektif dalam mendeteksi zona-zona dengan kontras resistivitas tinggi untuk mendeliniasi zona permeabel lapangan panas bumi. Daerah prospek panas bumi Gunung Slamet dapat terdeliniasi dengan jelas berdasarkan beberapa penampang lintasan yang dibuat, yang menunjukkan daerah prospek berada di sisi sebelah barat Gunung Slamet dengan luas berdasarkan peta BOC sekitar 13 km2, dan berdasarkan peta resistivitas pada elevasi 0 meter yang dikombinasikan dengan peta struktur geologi luas daerah prospek sekitar 22 km2. Dan hasil akhir dari penelitian ini adalah memberikan rekomendasi dalam menentukan lokasi pemboran, dengan sebelumnya membuat model konseptual prospek panas bumi Gunung Slamet.

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There are two geothermal prospects in the vicinity of Mount Slamet, the prospect of Guci in northwest and prospects Baturaden in the south of Mount Slamet. Be very interesting to know the relationship between the two prospects, whether the prospect of two regions separated by low permeability barrier heights so that there will be no interference between the two prospects?

By doing permeable zone delineation based on data analysis magnetotelluric and gravity, correlated with surface geological structural data and existing surface manifestations, are expected to know the relationship between the two prospects.

In this research, processing and modeling of geophysical data using magnetotelluric inversion method 2-D and 2-D method of gravity forward. Modeling is very effective in detecting zones with high resistivity contrast to delineate the permeable zone geothermal field. Geothermal prospect areas of Mount Slamet can be delineated clearly based on some of the tracks that made cross-section, showing the prospect area is located on the west side of Mount Slamet with broad based map BOC about 13 km2, and resistivity maps based on elevation of 0 meters, combined with the structure geological maps, the prospect area about 22 km2.

And the end result of this study is to provide recommendations in determining the location of drilling, with previous a conceptual model of geothermal prospects Mount Slamet."

"[Daerah prospek panas bumi Gunung Arjuno dan Gunung Welirang berada pada jalur vulkanik yang dikenal dengan jalur ring of fire, yaitu rentetan gunung api, baik yang aktif, maupun gunung api yang tidak aktif. Gunung tersebut berasosiasidengan pembentukan sistem panas bumi yang ditandai dengan kemunculan manifestasi yang terdiri dari mata air panas Padusan, Coban dan Cangar serta adanya fumarol yang terdapat di komplek Gunung Welirang. Dari hasil perhitungan geothermometer daerah prospek panas bumi Gunung Arjuno danGunung Welirang memiliki temperatur 250o C dan masuk dalam kategori high temperature (>225 oC). Untuk mengetahui batas, kedalaman, dan geometri dari reservoir yang ada, dilakukan pengukuran dengan metode Magnetotellurik (MT), Time Domain Electromagnetic (TDEM) dan gaya berat. Dari hasil pengukurantersebut, dilakukan pemodelan pada 138 data MT, 103 data TDEM dan 253 data gaya berat. Selanjutnya hasil pemodelan dianalisa dengan menggunakan penampang 1 dimensi, 2 dimensi dan visualisasi 3 dimensi. Karakteristik reservoir berada pada kisaran 10-30 Ohm-m dengan nilai densitas rata-rata 2.2gr/cc dan menghasilkan prospek panas Gunung Arjuno dan Gunung Welirang sekitar 40 km2 dengan potensi yang dapat dikembangkan untuk pembangkit tenaga listrik sebesar 140 MWe, rekomendasi penentuan titik bor eksplorasi berada di 2 km baratlaut dari komplek Gunung Welirang.

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The geothermal prospect areas Mount Arjuno and Mount Welirang is on track which is known as volcanic ring of fire, which is a series of volcanoes, both active and inactive volcanoes. The mountain is associated with the formation of geothermal systems that are characterized by the appearance of manifestations consisting of Padusan, Coban and Cangar hot springs and their fumaroles located

in Mount Welirang complex. From the calculation geothermometer, the geothermal prospect areas Mount Arjuno and Welirang has a temperature of 250°C and in the category of high temperature (190 oC-236 oC). To determine the

boundary, the depth, and the geometry of the existing reservoir, measured by the method of magnetotelluric (MT), Time Domain Electromagnetic (TDEM) and gravity. From the results of these measurements, modeling performed on the 138

MT data, 103 TDEM data and 253 gravity data. Furthermore, the modeling results were analyzed using 1 dimensional cross-section, 2 dimensional and 3 dimensional visualization. The position of the reservoir is in the range of 10-30 Ohm-m with an average density value 2.2 g/CC3 to generate hot prospects Mt.Arjuno and Mount Welirang approximately 40 km2. with potential developed for power plants of 140 MWe, recommendations exploration drill point

determination located at 3km north-west of the mountain complex Mount Welirang.;The geothermal prospect areas Mount Arjuno and Mount Welirang is on track

which is known as volcanic ring of fire, which is a series of volcanoes, both active

and inactive volcanoes. The mountain is associated with the formation of

geothermal systems that are characterized by the appearance of manifestations

consisting of Padusan, Coban and Cangar hot springs and their fumaroles located

in Mount Welirang complex. From the calculation geothermometer, the

geothermal prospect areas Mount Arjuno and Welirang has a temperature of

250°C and in the category of high temperature (190 oC-236 oC). To determine the

boundary, the depth, and the geometry of the existing reservoir, measured by the

method of magnetotelluric (MT), Time Domain Electromagnetic (TDEM) and

gravity. From the results of these measurements, modeling performed on the 138

MT data, 103 TDEM data and 253 gravity data. Furthermore, the modeling results

were analyzed using 1 dimensional cross-section, 2 dimensional and 3

dimensional visualization. The position of the reservoir is in the range of 10-30

Ohm-m with an average density value 2.2 g / CC3 to generate hot prospects

Mt.Arjuno and Mount Welirang approximately 40 km2. with potential developed

for power plants of 140 MWe, recommendations exploration drill point

determination located at 3km north-west of the mountain complex Mount

Welirang.;The geothermal prospect areas Mount Arjuno and Mount Welirang is on track

which is known as volcanic ring of fire, which is a series of volcanoes, both active

and inactive volcanoes. The mountain is associated with the formation of

geothermal systems that are characterized by the appearance of manifestations

consisting of Padusan, Coban and Cangar hot springs and their fumaroles located

in Mount Welirang complex. From the calculation geothermometer, the

geothermal prospect areas Mount Arjuno and Welirang has a temperature of

250°C and in the category of high temperature (190 oC-236 oC). To determine the

boundary, the depth, and the geometry of the existing reservoir, measured by the

method of magnetotelluric (MT), Time Domain Electromagnetic (TDEM) and

gravity. From the results of these measurements, modeling performed on the 138

MT data, 103 TDEM data and 253 gravity data. Furthermore, the modeling results

were analyzed using 1 dimensional cross-section, 2 dimensional and 3

dimensional visualization. The position of the reservoir is in the range of 10-30

Ohm-m with an average density value 2.2 g / CC3 to generate hot prospects

Mt.Arjuno and Mount Welirang approximately 40 km2. with potential developed

for power plants of 140 MWe, recommendations exploration drill point

determination located at 3km north-west of the mountain complex Mount

Welirang.;The geothermal prospect areas Mount Arjuno and Mount Welirang is on track

which is known as volcanic ring of fire, which is a series of volcanoes, both active

and inactive volcanoes. The mountain is associated with the formation of

geothermal systems that are characterized by the appearance of manifestations

consisting of Padusan, Coban and Cangar hot springs and their fumaroles located

in Mount Welirang complex. From the calculation geothermometer, the

geothermal prospect areas Mount Arjuno and Welirang has a temperature of

250°C and in the category of high temperature (190 oC-236 oC). To determine the

boundary, the depth, and the geometry of the existing reservoir, measured by the

method of magnetotelluric (MT), Time Domain Electromagnetic (TDEM) and

gravity. From the results of these measurements, modeling performed on the 138

MT data, 103 TDEM data and 253 gravity data. Furthermore, the modeling results

were analyzed using 1 dimensional cross-section, 2 dimensional and 3

dimensional visualization. The position of the reservoir is in the range of 10-30

Ohm-m with an average density value 2.2 g / CC3 to generate hot prospects

Mt.Arjuno and Mount Welirang approximately 40 km2. with potential developed

for power plants of 140 MWe, recommendations exploration drill point

determination located at 3km north-west of the mountain complex Mount

Welirang.;The geothermal prospect areas Mount Arjuno and Mount Welirang is on track

which is known as volcanic ring of fire, which is a series of volcanoes, both active

and inactive volcanoes. The mountain is associated with the formation of

geothermal systems that are characterized by the appearance of manifestations

consisting of Padusan, Coban and Cangar hot springs and their fumaroles located

in Mount Welirang complex. From the calculation geothermometer, the

geothermal prospect areas Mount Arjuno and Welirang has a temperature of

250°C and in the category of high temperature (190 oC-236 oC). To determine the

boundary, the depth, and the geometry of the existing reservoir, measured by the

method of magnetotelluric (MT), Time Domain Electromagnetic (TDEM) and

gravity. From the results of these measurements, modeling performed on the 138

MT data, 103 TDEM data and 253 gravity data. Furthermore, the modeling results

were analyzed using 1 dimensional cross-section, 2 dimensional and 3

dimensional visualization. The position of the reservoir is in the range of 10-30

Ohm-m with an average density value 2.2 g / CC3 to generate hot prospects

Mt.Arjuno and Mount Welirang approximately 40 km2. with potential developed

for power plants of 140 MWe, recommendations exploration drill point

determination located at 3km north-west of the mountain complex Mount

Welirang., The geothermal prospect areas Mount Arjuno and Mount Welirang is on track

which is known as volcanic ring of fire, which is a series of volcanoes, both active

and inactive volcanoes. The mountain is associated with the formation of

geothermal systems that are characterized by the appearance of manifestations

consisting of Padusan, Coban and Cangar hot springs and their fumaroles located

in Mount Welirang complex. From the calculation geothermometer, the

geothermal prospect areas Mount Arjuno and Welirang has a temperature of

250°C and in the category of high temperature (190 oC-236 oC). To determine the

boundary, the depth, and the geometry of the existing reservoir, measured by the

method of magnetotelluric (MT), Time Domain Electromagnetic (TDEM) and

gravity. From the results of these measurements, modeling performed on the 138

MT data, 103 TDEM data and 253 gravity data. Furthermore, the modeling results

were analyzed using 1 dimensional cross-section, 2 dimensional and 3

dimensional visualization. The position of the reservoir is in the range of 10-30

Ohm-m with an average density value 2.2 g / CC3 to generate hot prospects

Mt.Arjuno and Mount Welirang approximately 40 km2. with potential developed

for power plants of 140 MWe, recommendations exploration drill point

determination located at 3km north-west of the mountain complex Mount

Welirang.]"

"Eksplorasi panasbumi yang dilakukan pada daerah prospek panasbumi bertujuan untuk mencari zona reservoir. Zona reservoir yang baik bisa dilihat dari 2 faktor yaitu, batuan reservoir memiliki permeabilitas yang tinggi dan fluida reservoir memiliki suhu yang tinggi. Berdasarkan faktor pertama, permeabilitas batuan reservoir yang tinggi memungkinkan reservoir untuk memiliki kandungan fluida panasbumi yang banyak. Pada umumnya batuan memiliki permeabilitas lebih besar disebabkan oleh batuan tersebut memiliki permeabilitas sekunder yang berasal dari struktur geologi berupa patahan. Metode geofisika seperti metode Magnetotellurik (MT) dan Gravitasi diaplikasikan pada penelitian ini untuk memetakan zona reservoir sistem panasbumi. Metode MT digunakan untuk mendeteksi struktur resistivitas bawah permukaan. Analisis metode gravitasi yang melibatkan data anomali bouguer lengkap dan anomali residual dapat digunakan untuk memetakan struktur densitas bawah permukaan. Faktor kedua yaitu temperatur yang didapatkan dari data sumur yang ada. Selanjutnya, proses interpretasi terintegrasi dilakukan dengan melibatkan data penunjang lainnya berupa data geologi, geokimia, dan data sumur yang menghasilkan model konseptual panasbumi.

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The objective of geothermal exploration which was concluded at geothermal prospects area is to find the reservoir zone. Good reservoir zones can be seen from two factors, reservoir rocks which have high permeability and reservoir fluid has high temperature. Under the first factor, high permeability of reservoir rocks allows the reservoir to contain much geothermal fluids. In general, great permeability of the rock is caused by secondary permeability derived from geological structures like faults. Geophysical methods such as magnetotelluric (MT) and gravity were applied in this study to delineate the reservoir zone. MT method was used to detect subsurface resistivity structure. Analysis of gravity data to complete bouguer anomaly map (CBA) and residual anomaly can figure subsurface density structures. Under the second factor, the temperature can be obtained from well data. Furthermore, the integrated interpretation is done by involving other supporting data such as geological, geochemical, and well data which produces geothermal conceptual model."

"Sistem panas bumi Baturraden berasosiasi dengan aktivitas vulkanik yang berkembang akibat tektonik Jawa pada Kala Paleosen. Pada Kala ini mulai terbentuk struktur geologi yang intensif. Hal ini memicu magma andesitis untuk keluar pada Zaman Kuater. Intensitas aktivitas vulkanisme Gunung Slamet yang tinggi pada Kala Holosen mengakibatkan material vulkanik muda menutupi data permukaan seperti struktur geologi dan alterasi. Padahal data tersebut sangat membantu dalam mengidentifikasi zona permeable dan zona reservoir. Penelitian ini dilakukan untuk memastikan zona permeable dan zona reservoir dengan mengkorelasikan data struktur geologi dan magnetotelluric (MT). Korelasi ini diperoleh melalui analisis komperhensif berdasarkan litologi, struktur permukaan, karakteristik dan model MT 3D. Selain itu juga untuk meningkatkan tingkat keyakinan terhadap korelasi, pada penelitian ini mengaplikasikan metode gravity. Hasil penelitian dari penelitian ini menunjukan adanya korelasi antara struktur geologi dengan data MT antara lain inversi 3D MT, polar diagram, induction arrow, splitting curve, nilai tipper dan nilai ellipticity. Korelasi tersebut memperlihatkan adanya kontol struktur NE-SW terhadap hadirnya zona main conductor dan zona deformasi. Struktur NE-SW yang bersifat ekstensional mengontrol vulkanisme komplek Gunungapi Slamet dan zona permeable dari sistem panas bumi Baturraden sehingga zona pemboran diorientasikan NE-SW dengan target pemboran berarah NW-SE.

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Baturraden geothermal system associated by volcanic activity which grown by Paleocene tectonic in Java. At the time, initial geological structure was established intensively thus it triggered andesitic magma to flow out in Quaternary Period. High intensity of Mt. Slamet volcanism in Holocene Epoch affected younger volcanic material could covered surface data such as geological structure and alteration. Whereas those data are very helpful to identify permeable zone and reservoir zone.

This study will be conducted to ensure the presence of the permeable zone and reservoir zone by correlating geological structure and magnetotelluric (MT). The correlations are acquired through a comprehensive analysis of lithology, surface structure, MT data characterization and MT 3D model. Furthermore, to improve confidence level of the correlation, the study applies gravity method.

The result of this study shows that there are any correlations between geological structure and MT data including 3D MT inversion, polar diagram, induction arrow, splitting curve, tipper value and ellipticity value. The Correlations present the influence NE-SW structure to the existence of main conductor and deformation zone. Extensional NE-SW structure triggered volcanism of Slamet Volcano Complex and permeable zone of Baturraden geothermal system thus drilling zone should be oriented NE-SW direction with well targeting should be pointed to NW-SE direction."

"Tahapan eksplorasi masih menyimpan tantangan terbesar dan memiliki resiko yang tinggi bagi para pelaku industri bidang geothermal. Oleh karena itu, diperlukan pemahaman yang baik mengenai kondisi bawah-permukaan dengan mengintegrasikan data geosains yang memiliki kualitas yang bagus. Target utama dari eksplorasi yaitu penentuan lokasi pemboran dengan tingkat kepastian yang lebih tinggi. Pemboran diarahkan pada area yang memiliki temperatur dan permeabilitas yang tinggi. Distribusi temperatur bawah permukaan dapat didekati dari nilai resistivitas yang diperoleh dari data MT. Sementara zona dengan permeabilitas yang tinggi, berasosiasi dengan struktur geologi. Pemetaan geologi hanya dapat menggambarkan struktur geologi di permukaan, sementara kemenerusannya di bawah-permukaan menjadi kesulitan tersendiri untuk dideteksi. Penelitian ini difokuskan pada identifikasi struktur geologi bawah-permukaan menggunakan data Magnetotellurik (MT) dan Gravitasi. Analisis pola spliting kurva, arah elongasi polar diagram, serta pencitraan struktur di bawah-permukaan dengan melihat hasil inversi 3-dimensi, yang diperoleh dari data MT, serta didukung oleh hasil pemodelan data Gravitasi, merupakan metodologi yang digunakan dalam penelitian ini. Data geologi dan geokimia, dilibatkan sebagai data pendukung untuk membuat analisis keberadaan struktur geologi bawah-permukaan ini menjadi lebih komprehensif. Tahap akhir dari penelitian ini adalah memberikan rekomendasi dalam menentukan lokasi pemboran, dengan sebelumnya membuat model konseptual dan mendelineasi daerah prospek. Hasil analisis struktur, model konseptual, dan delineasi daerah prospek, menghasilkan rekomendasi tiga buah sumur eksplorasi. Dua sumur mengarah pada upflow di Gunung ?X?, dan satu sumur mengarah pada upflow di scoria cone.

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Exploration stage still holds the biggest challenges and have a high risk for the geothermal industry. Therefore, required a good understanding of subsurface conditions by integrating the geoscientific data that has a high quality. The main target of exploration is the determination of drilling trajectory. The subsurface drilling target is actually directed to high temperature and high permeability zone. Subsurface temperature distribution can be approximated from the resistivity values obtained from the data MT. While the zones with high permeability, associated with geological structures. Geological mapping could only figure out geological structures indicated at the surface. However, continuation of the geological structure into the subsurface is difficult to detect. This study focused on the identification of subsurface geological structure using Magnetotelluric (MT) and gravity data. Splitting pattern analysis from MT curve, the elongation of orientation of polar diagrams, as well as imaging of subsurface structures by looking at the results of 3-dimensional inversion, the data obtained from MT, and supported by the results of Gravity data modeling, a methodology used in this study. Geological and geochemical data, were included as supporting data to make the analysis of the presence of subsurface geological structure has become more comprehensive. And the final stage of this research is to provide recommendations in determining the location of drilling, by first making a conceptual model of the geothermal system and delineating the prospect area. The result of structure analysis, conceptual model, and prospect delineation, provide three exploration wells for recommendation. The first two will be directed to upflow at Mount ?X?, and the other one to upflow at scoria cone."

"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. "

"ABSTRAKAnalisis dimensionalitas merupakan parameter yang kuat untuk memilih pemodelan mana yang sesuai disetiap kondisi bawah permukaan. Hal ini karena sudah dikembangkannya teknologi inversi 1-D, 2-D dan 3-D. Selain itu analisis dimensionalitas dapat digunakan untuk mengetahui arah dari struktur utama. Pada penelitian ini digunakan dua parameter analisis dimensionalitas untuk dipelajari sebagai tahapan awal penelitian analisis dimensionalitas. Parameter diagram polar dan impedansi skew digunakan untuk menganalisis kondisi dimensionalitas model sintetik dan data riil lapangan panas Bumi. Selain itu juga dilakukan pembandingan inversi 1-D, 2-D dan 3-D pada setiap kondisi dimensionalitas bawah permukaan. Perbandingan menunjukkan inversi 3-D dapat menggambarkan kondisi dimensionalitas ideal 1-D, 2-D dan 3-D dengan baik sehingga analisis dimensionalitas untuk memilih pemodelan mana yang tepat tidak perlu lagi dilakukan. Namun, analisis dimensionalitas masih efektif untuk dilakukan dalam mengidentifikasi struktur bawah permukaan dan menentukan arah dari struktur sesuai dengan hasil yang telah ditunjukkan pada data sintetik dan data riil dari penelitian ini.

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ABSTRAKDevelopment of 1-D, 2-D and 3-D inversion has causing dimensionality analysis as a powerful parameter that select which type of approach is more suitable to accomplish modeling, or interpretation : one dimensionality, two dimensionality and three dimensionality. It because 1-D, 2-D and 3-D inversion already developed. Moreover, dimensionality analysis can be used to know the path of geoelectrical strike. This thesis use two parameters of dimensionality analysis as the beginning of dimensionality analysis research. Polar Diagram and impedance skew parameter are used for analizing the dimensionality condition from syntetic model and real data of geothermal field. In this thesis, comparison of 1-D, 2-D and 3-D inversion has been made in each subsurface dimensionality condition. The comparison result show 3-D inversion could imaged the proper condition of ideal dimensionality 1-D, 2-D and 3-D, so the dimensioanlity analysis is not strictly necessary for selecting the more suitable inversion modeling. Otherwise, dimensionality analysis is still recommended in order to identify the subsurface structure, as likes the application of syntethic data and real data in this thesis."

"Penelitian ditujukan untuk mendapatkan perbandingan model inversi 1-D dan Inversi 2-D di 7 titik dalam 1 lintasan pengukuran. Pemodelan data magnetotelurik dilakukan dengan menggunakan dua metode inversi, yaitu metode inversi 1-Dimensi Occam dan inversi 2-Dimensi Non Linier Conjugate Gradient (NLCG). Data-data yang mendukung di lintasan ini adalah penampang seismik dan data sumur. Berdasarkan model penampang yang didapatkan, permodelan data magnetotelurik (MT) dengan metode inversi Occam satu dimensi tidak memperlihatkan model yang sesuai dengan data pendukung, sehingga tidak dapat didekati dengan pemodelan satu dimensi. Sedangkan pemodelan data MT dengan metode inversi NLCG dua dimensi, memperlihatkan kesesuaian dengan data pendukung sehingga metode tersebut lebih tepat digunakan.

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Research is done to get comparison of model 1-D inversion and 2-D inversion in 7 points in 1 line measurement. Modelling of Magnetotelluric (MT) data is done by using two inversion method, those are method of 1-Dimensional Occam inversion and 2-Dimensional NLCG inversion. The supporting datas in this line of measurement are seismic section and well log data. Based on the result of MT model, modeling of MT data using 1-Dimensional Occam inversion does not show model matching with supporting datas, so that with modeling of MT data could not use 1-Dimensional inversion modeling. Meanwhile modeling of MT data using 2-Dimensional NLCG inversion show model matching with supporting datas so that the method more [is] precise used."

"Tingkat kesuksesan pemboran geotermal di Indonesia masih menjadi kendala utama dalam upaya pengembangan geothermal. Lapangan geotermal ?X? merupakan salah satu daerah prospek di Indonesia yang belum dilakukan pengeboran oleh pihak pengembang. Manifestasi yang muncul ke permukaan berupa mata air panas dan alterasi batuan, dengan tidak adanya manifestasi fumarol maka menjadi tantangan tersendiri dalam melakukan kegiatan eksplorasi geotermal di daerah penelitian. Penelitian ini difokuskan pada penentuan target pemboran di zona prospek. Adapun metode yang digunakan yaitu: remote sensing citra Landsat 7, 3D-MT serta geokimia. Analisis struktur permukaan lapangan geotermal "X" menggunakan citra satelit DEM dan Landsat 7. Teknologi citra dalam hal ini remote sensing sangat membantu dalam memetakan sebaran manifestasi aktivitas geothermal di suatu wilayah. Sedangkan untuk analisis struktur bawah permukaan dapat dilakukan dengan bantuan metode geofisika magnetotelluric (MT) didukung dengan data geologi dan data geokimia. Analisis data 3-D magnetotelluric (MT) dapat membantu mengintepretasikan resistivitas batuan bawah permukaan. Hasil Intepretasi data pada penelitian ini yaitu model konseptual dan luasan wilayah prospek. Mengacu pada model konseptual, dimana terdapat zona upflow yang ditandai adanya alterasi batuan dan adanya pola dome pada penampang resistivitas 3-D magnetotelluric (MT) di dekat struktur utama yang mengontrol aktivitas geotermal daerah penelitian, sedangkan zona outflow berarah ke barat dan timur daerah penelitian, sehingga penelitian ini merekomendasikan titik pemboran di zona upflow yang diharapkan berada pada zona dengan permeabilitas serta temperatur yang tinggi.

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Drilling success ratio of geothermal in Indonesia is still a major constraint in the development of geothermal. Geothermal field "X" is one of the unexploited, prospected field in Indonesia. Manifestations of a possible geothermal field are hot springs and rock alteration; the lack of fumarole manifestation has become a challenge in conducting geothermal exploration in the study area.

This research is focused on determining the drilling target of the prospected zone. The methodes used for this research are Landsat 7 image remote sensing, 3D-MT and geochemistry. The structure of geothermal field ?X??s surface is analyzed with DEM satellite image and Landsat 7. The imaging technology of remote sensing is very helpful in mapping the distribution of geothermal activity manifestation in a region. Meanwhile, analysis of subsurface structures can be done with the help of geophysical methods magnetotelluric (MT) is supported by geological and geochemistry data. The data analysis of 3-D magnetotelluric (MT) resistivity can help interpretation in sub-surface rocks.

Interpretation of data resulted in this research is the conceptual model and measuring the prospected region of the research areas. Based on the conceptual model, in which there?s an upflow zone marked with rock alterations and dome patterns on ressistivity of 3-D MT section near the main structure that controls the geothermal activities in the study area; while the outflow zone pointing west and east of the study area, allowing this research to recommend drilling target at the upflow zone expected to be at the high permeability and high temperature."

"ABSTRAKPenelitian di daerah prospek geothermal ldquo;X rdquo; bertujuan untuk mendelineasi zona permeable berdasarkan data audio magnetotellurik dan gravitasi yang dipadu dengan data geologi dan geokimia. Analisis data geologi dengan teknik remote sensing diidentifikasi dua struktur utama yang mengarah dari Utara - Selatan dan Barat Laut ndash; Tenggara dan terdapat satu lokasi alterasi yang berkorelasi dengan kemunculan manifestasi permukaan. Analisis data geokimia menunjukkan bahwa manifestasi fumarol merupakan manifestasi tipe upflow dan manifestasi air panas AP X1 dan AP X2 merupakan tipe manifestasi outflow. Geotermometer gas menunjukan temperatur reservoar adalah sekitar 290 C. Analisis data geofisika menggunakan 35 data titik ukur audio magnetotellurik dan 194 titik ukur gravitasi. Berdasarkan inversi 3D data AMT dan forward modelling gravitasi terdapat lapisan penudung cap rock dengan nilai resistiviatas rendah le; 10 ?m dan densitas 2.1 gr/cc yang diduga merupakan batuan produk Gunung BA Muda yang mengalami alterasi. Batuan cap rock sudah terlihat mulai dari permukaan dan menebal ke arah manifestasi AP X1 dengan kedalaman sekitar 500 meter dengan ketebalan 500 meter hingga 1000 meter Di bawah batuan cap rock terdapat batuan reservoar dengan nilai resistivitas sedang >10 s.d 65 ?m dan densitas 2,6 gr/cc. Batuan ini diinterpretasikan sebagai respon dari batuan Lava BU. Lapisan heat source berada di bawah reservoar dengan nilai resistivitas >100 ?m yang diduga merupakan satuan batuan aktivitas vulkanik Gunung BA. Top of Reservoir TOR diperkirakan berada pada kedalaman 500 m dari permukaan yang teridentifikasi pada elevasi 0 meter. Analisis kurva splitting diperoleh bahwa zona permeable kemungkinan berada di sebelah Timur Gunung BA dikarenakan area tersebut cenderung naik dibandingkan dengan area sekitarnya. Analisis kurva splitting ini memberi penguatan terhadap interpretasi struktur terpadu interpretasi struktur berdasarkan Geologi, FHD, peta resistivitas 3D AMT per elevasi . Luas zona prospek sebesar 1.5 km2 yang berada disebelah Timur Gunung BA.

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ABSTRACTThe research in ldquo X rdquo geothermal prospect area aimed to delineate permeable zone based on audio magnetotelluric and gravity data integrated with geology and geochemistry data. Geological analysis with remote sensing technique identified two main structures that lead from North ndash South and Northwest ndash Southeast and found one altered location which correlate with the appearance of surface manifestation. Geochemical analysis shows that fumarole is the upflow zone and manifestations which appear in AP X1 and AP X2 are the outflow zone. Gas geothermometer shows that the reservoir temperature is about 290 C. The analysis of geophysics data used 35 audio magnetotelluric points and 194 gravity points. Based on 3D AMT data inversion and gravity forward modelling, there is cap rock layer with low resistivity le 10 m and density 2.1 gr cc expected as product rocks of young AB Mountain that altered. Cap rock finds in the surface and thickened toward AP X1 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 10 s.d 65 m and density 2,6 gr cc. This rock is interpreted as the response from Lava BU rocks. Heat source layer is located underneath reservoir rock layer with resistivity value 100 m which is interpreted as BA vulcanic rock. Top of Reservoir TOR is estimated in depth of 500 m from the surface and identified at elevation 0 meter. Analysis of curve splitting is obtained that permeable zone possibly located at East BA Mountain because the area were tending to increase compared with the surrounding area. Analysis of curve splitting strengthen integrated interpretation structure interpretation structure based on Geology, FHD, Map of 3D AMT resistivity per elevation . The prospect area is about 1.5 km2 which located in East BA Mountain."