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"Telah dikembangkan program inversi dan program forward-modeling data MT 2D. Program inversi telah dites menggunakan data sintetik (dari program forward-modeling) dan data lapangan (daerah geotermal Sibayak) dengan hasil terbukti mampu memetakan bawah permukaan. Program inversi yang dibuat digunakan untuk menginversi data MT lapangan geotermal Sibayak, Sumatra Utara. Hasil inversi tersebut digunakan untuk membuat penampang 2-D distribusi resistivitas bawah permukaan. Model yang diperoleh kemudian diinterpretasi dengan bantuan data sumur dan data geologi. Hasil interpretasinya adalah zona up-flow terdapat di sebelah utara, dekat Gunung Sibayak, sedang zona out-flow berada di sebelah selatan. Rekomendasi pengeboran diberikan untuk daerah di sebelah utara. Rekomendasi reinjeksi fluida diberikan untuk daerah di sebelah selatan.

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A 2-D MT Software for inverse and forward-modeling has been developed. The inversion program was tested using both synthetic data (from forward-modeling software) and real data (from Sibayak geothermal area) resulting conclusion that the inversion program was capable reconstructing subsurface model. The inversion program was used to invert Sibayak geothermal MT data. The inversion result was used to produce cross-section model of subsurface resistivity distribution. The model derived was then interpreted by incorporating borehole and geology data. Interpretation results are: up-flow zone is situated in the northern side near Mount Sibayak, while out-flow zone is situated in the southern side. Drillings are recommended to be located in northern area. Geothermal brine reinjection is recommended to be located in southern area."

"[Kegiatan eksplorasi geothermal bertujuan mengetahui sistem geothermal daerah penyelidikan yang meliputi model dan batas prospek, karakteristik dan potensial reservoir dan hidrogeologi, untuk penentuan target pemboran, dilanjutkan dengan pemboran eksplorasi.Hasil inversi 3-dimensi data MT akan menyajikan distribusi struktur resistivitas bawah permukaan.Pemboran eksplorasi geothermal bertujuan untuk membuktikan adanya sumber daya geothermal dan menguji model sistem geothermal yang telah dibuat. Kriteria target pemboranadalah area yang memiliki temperature dan permeabilitas yang tinggi. Pada waktu pemboran sumur panas bumi ditembusnya zona bertemperatur tinggi yang disertai atau diikuti dengan terjadinya loss of circulation sangat diharapkan (permeabilitas tinggi), karena merupakan suatu indikasi telah ditembusnya rekahan-rekahan yang diharapkan merupakan zona produksi (feed zone).Untuk menguji model sistem yang dibuat dilakukan korelasi antara data hasil pemboran dengan inverse 3D data MT, khususnya nilai resistivity lapisandengan data temperatur, kandungan mineral alterasi, geokimia dari data pemboran.Dari hubunganantar parameter akan terlihat karakteristik sistem geothermal di daerah penyelidikan, yang memperlihatkan zona prospek yang berhubungan dengan temperature dan permeabilitas yang tinggi. Dari hasil evaluasi akan dilakukan rekonstruksi system geothermal daerah penyelidikan, yang lebih mendekati kondisi bawah permukaan dan dapat dipergunakan untuk membuat rekomendasi pemboran selanjutnya dan arah pengembangan di masa yang akan datang;Geothermal exploration activities aimed at knowing the geothermal system that includes model and boundary the prospects, potential and reservoir characteristics and also hydrological system. By using 3D inversion of MT data, subsurface resistivity distribution structure can be obtained and with the addition of other geosciences data, LumutBalai geothermal system can be constructed. Futhermore, drilling targets zone can be identified from geothermal system which then followed by exploration drilling .Geothermal exploration drilling is carried out to verify the existence of geothermal resources and test the geothermal systems which previously has been made. Drilling target criteria is the area which consist of high temperature and permeability. During geothermal drilling, it is expected that high temperature zone shall be encountered. It will be followed by loss circulation zone which indicates that fractures have already been penetrated and confirm that feed zone has been discovered.In order to test constructed model, correlation between drilling data and 3D MT inverse is carried out, particularly values of resistivity layer with temperature data, alteration mineralcomposition, and geochemical data derived from drilling.Parameter correlation will explain geothermal system characteristics in study area which delineates prospect zones and its association with high temperature and permeability. The evaluation results of this study will reconstruction geothermal system the investigation area, which can be used to develop a recommendation of subsequent drilling and further development direction;Geothermal exploration activities aimed at knowing the geothermal system that includes model and boundary the prospects, potential and reservoir characteristics and also hydrological system. By using 3D inversion of MT data, subsurface resistivity distribution structure can be obtained and with the addition of other geosciences data, LumutBalai geothermal system can be constructed. Futhermore, drilling targets zone can be identified from geothermal system which then followed by exploration drilling .Geothermal exploration drilling is carried out to verify the existence of geothermal resources and test the geothermal systems which previously has been made. Drilling target criteria is the area which consist of high temperature and permeability. During geothermal drilling, it is expected that high temperature zone shall be encountered. It will be followed by loss circulation zone which indicates that fractures have already been penetrated and confirm that feed zone has been discovered.In order to test constructed model, correlation between drilling data and 3D MT inverse is carried out, particularly values of resistivity layer with temperature data, alteration mineralcomposition, and geochemical data derived from drilling.Parameter correlation will explain geothermal system characteristics in study area which delineates prospect zones and its association with high temperature and permeability. The evaluation results of this study will reconstruction geothermal system the investigation area, which can be used to develop a recommendation of subsequent drilling and further development direction, Geothermal exploration activities aimed at knowing the geothermal system that includes model and boundary the prospects, potential and reservoir characteristics and also hydrological system. By using 3D inversion of MT data, subsurface resistivity distribution structure can be obtained and with the addition of other geosciences data, LumutBalai geothermal system can be constructed. Futhermore, drilling targets zone can be identified from geothermal system which then followed by exploration drilling .Geothermal exploration drilling is carried out to verify the existence of geothermal resources and test the geothermal systems which previously has been made. Drilling target criteria is the area which consist of high temperature and permeability. During geothermal drilling, it is expected that high temperature zone shall be encountered. It will be followed by loss circulation zone which indicates that fractures have already been penetrated and confirm that feed zone has been discovered.In order to test constructed model, correlation between drilling data and 3D MT inverse is carried out, particularly values of resistivity layer with temperature data, alteration mineralcomposition, and geochemical data derived from drilling.Parameter correlation will explain geothermal system characteristics in study area which delineates prospect zones and its association with high temperature and permeability. The evaluation results of this study will reconstruction geothermal system the investigation area, which can be used to develop a recommendation of subsequent drilling and further development direction]"

"Lapangan geothermal Awibengkok, juga dikenal dengan nama Salak, berlokasi sekitar 60 km dari selatan Jakarta di pulau Jawa, Indonesia. Awibengkok merupakan lapangan dengan reservoir penghasil energi geothermal terbesar di Indonesia. Area reservoir terbukti yaitu 18 km2 dengan sumber potensial sebesar 377 MWe. Untuk mengeksploitasi energi tersebut maka dibuat sumur-sumur produksi serta sumur injeksi guna meningkatkan kelangsungan reservoir dalam menghasilkan uap panas yang nantinya dikonversi menjadi tenaga listrik. Aktivitas dari sumur-sumur tersebut memicu terjadinya gempa mikro (mikroseismik). Pengamatan mikroseismik dilakukan menggunakan SMART-24D. Selanjutnya data mikroseismik hasil pengamatan ini diolah ke dalam software Seisplus sehingga diperoleh data berupa waktu, koordinat, elevasi, dan magnitudo gempa yang telah terjadi. Setelah data-data tersebut diperoleh maka dibuat peta episenter menggunakan software WinGLink, dimana posisi gempa diproyeksikan ke dalam bidang datar horisontal. Pada software tersebut juga dibuat persebaran gempa mikro dalam tampilan 2 dimensi yaitu berupa penampang melintang (cross section). Untuk hasil interpretasi dalam tampilan 3-dimensi digunakan software Geoslicer-X, sehingga diperoleh model persebaran mikroseismik di lapangan Awibengkok. Dari model persebaran mikroseismik tersebut terlihat adanya delineasi zona rekahan yang digambarkan dengan even mikroseismik yang berkumpul membentuk suatu kelompok (cluster) di sebelah barat lapangan Awibengkok. Sehingga dapat disimpulkan bahwa mekanisme gempa yang dominan terjadi di lapangan Awibengkok banyak dipengaruhi oleh adanya aktivitas injeksi dan produksi.

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The Awibengkok geothermal field which is also known as Salak,is located in Java island, 60 km southern Jakarta. This place is the largest producer of geothermal power in Indonesia. The proven reservoir in this place is about 18 km2 with 377 MWe potential source. In order to exploring that area, people make many production and injection wells. They made it in order to enduring the reservoir performance in producing hot vapor, which will be converted into electric supply. The activity from those wells triggering the microseismic event to happen. The observation of the microseismic is carried out using SMART-24D. Then, the data result of the observation is processed in Seisplus software, so there will be new datas such as time, position, elevation, and magnitude of the microseismic event which had been occured. After those datas are collected, the epicenter map is ready to be made by using WinGLink. In WinGLink the microseismic position is projected in the horizontal flat surface and also the view of microseismic spreading in 2-dimensional view which have cross section shaped. For the interpretation result in 3-dimensional view, Geoslicer-X software is used here, so that the spreading model of microseismic in Awibengkok field is obtained. From the spreading model, the delineation fracture zone is seen in western Awibengkok which is described with microseismic event. In conclusion, the mechanism of the microseismic event which always happens in Awibengkok is caused by injection and production activities."

"Lapangan geothermal Sibayak terletak di kawasan utara Great Sumatra Fault Zone (GSFZ) yang memiliki topografi yang tinggi di dalam kaldera Singkut. Ditinjau dari kondisi geologinya, lapangan ini memiliki prospek geothermal yang ditandai dengan keberadaan manifestasi panas berupa solfatara, fumarole, chloride springs dan silica sinters. Untuk menginvestigasi struktur bawah permukaan secara lebih detail, maka dilakukan reinterpretasi data magnetotellurik dan gravitasi. Dari pemodelan 2-Dimensi MT yang menggunakan software MT2Dinv dan 3-Dimensi MT menggunakan software GeoSlicer-X maka dapat diketahui clay cap mempunyai nilai resistivitas 5-10 Ωm. Zona reservoir diindikasikan dengan harga resistivitas 50- 200 Ωm yang terdapat di bawah zona clay cap dan berada pada kedalaman sekitar 1600m. Pusat reservoir terdapat pada daerah yang meliputi Gunung Sibayak dan Gunung Pratektekan dengan luas yang diperkirakan sekitar 4 km². Pemodelan data gravitasi mendukung gambaran stuktur utama yang berupa kaldera Singkut dan sesarsesar yang berarah barat laut-tenggara. Berdasarkan studi ini dapat direkomendasikan sumur produksi diarahkan pada pusat reservoir, sedangkan reinjeksi ditempatkan di daerah dekat reservoir tetapi yang diduga memiliki hubungan permeabilitas, yaitu di sekitar batas kaldera sebelah selatan.

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Sibayak geothermal field is situated in the northern Great Sumatra Fault Zone (GSFZ), which has high topography inside Singkut caldera. From the geological point of view, Sibayak field is a potential geothermal area supported by the occurrence of surface manifestations such as solfataras, fumaroles, chloride springs and silica sinters. To investigate subsurface geological structure, reinterpretation of the Magnetotelluric and gravity data were carried out. Two-dimensional modeling of MT data using MT2Dinv software and 3-D visualization of the MT data using GeoSlicer-X have delineated clay cap with resistivity of 5-10 ohm. Reservoir zone is indicated by slightly higher resistivity (50 - 200 ohm-m) below the clay cap located in the depth of about 1600m. Center of reservoir is probably located in the area between Mt Sibayak and Mt Pratektekan covering about 4 km². The gravity data modeling supports the existence of main structures, those are Singkut caldera and faults zone oriented in the northwest - southeast direction. Based on this study, it is recommended that the production wells shoud be located to the central of reservoir and reinjection wells should be sited to the area close to the main reservoir which has permeability connection, that is in the southern caldera boundary."

"The Cinnamon Geothermal prospect is located in the northeastern ofMayonnaise Island, Indonesia. It is located in quaternary volcanic terrainabout 750 m asl. The various types of surface manifestations e.g. solfatara,fumarole, steaming ground, mud pools and hotsprings are concentrated nearCinnamon village. Few reconnaissance surveys had been conducted sinceyear 1977. To model the Geothermal Prospect of Cinnamon, one can useMagnetotelluric and Gravity method.Magnetotelluric method uses telluric current as natural source toidentify the resistivity properties of subsurface rocks. This resistivity sectioncan be used to identify the occurrence of clay cap. Gravity method can beused to map the density response from the subsurface to detect a massivedensity contrast that match the geological condition.The integrated model of Cinnamon combining geophysical,geochemical and geological data can be used to locate the reservoir, outflow,and upflow for further drilling purpose and exploitation."

"Gunung Arjuno-Welirang merupakan gunung api yang berada di Provinsi Jawa Timur yang memiliki potensi energi panas bumi. Secara geologi, batuan penyusun pada umumnya berjenis andesit-basaltik yang berasal dari beberapa pusat erupsi seperti gunung Arjuno, Welirang, Kembar I – II, gunung Bakal, gunung Pundak dan gunung Bulak. Untuk mengetahui keberadaan struktur patahan di bawah permukaan, dilakukan analisis data gayaberat. Zona struktur patahan dapat diketahui dari peta kontur anomali residual, yang ditunjukkan dari adanya nilai anomali positif dan negatif yang dibatasi dengan kontur yang rapat. Identifikasi daerah panas bumi dengan data gaya berat perlu dilakukan untuk mengestimasi kedalaman sekitar 4400 m menggunakan analisis spektrum. Berdasarkan hasil pemodelan 2 dimensi yang telah dikorelasikan dengan data geologi, penampang inversi 3D Magnetotellurik dan hasil analisis second vertical derivative digunakan untuk mengidentifikasi keberadaan serta jenis patahan dan struktur naik yang kemungkinan ada di daerah Padusan dan patahan turun yang berada pada struktur kaldera Arjuno-Welirang. Sistem panas bumi dicirikan dengan munculnya manifestasi berupa air panas dengan temperatur sekitar 50ºC, pH netral, solfatara dan fumarol dengan temperatur hingga 137 ºC dan alterasi batuan.

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Arjuno-Welirang Mountain, the volcanoes which located in East Java, had the potential of geothermal energy. In geology, rocks constituents in general had basaltic andesite type that derived from several eruption centers, such as mountain Arjuno, Welirang, Kembar I–II, Bakal mountain, Bulak mountain and Pundak mountain. To identify the presence of a fault under surface, gravity data analysis was done. Fault zone structures can be seen from the residual anomaly contour map, that show the presence of positive and negative anomalous values that constrained by a tight contours. Identification of geothermal areas with gravity data was important to be done in order to estimate depth around 4400m by using spectrum analysis.

Based on Two-dimensional modeling results that has been correlated with geological data, the cross-sectionals 3D magnetotelluric inversion and vertical second derivative analysis was used to identify the presence and type of fracture and also the ascended stuctures that could be exist on Padusan area and the descended faults that exist in Caldera’s stucture on Arjuno-Welirang. Geothermal system was characterized by the existance of hot water’s manifestations with temperature about 50º C, neutral acidity, Solfatara and Fumaroles that have temperature up to 137 º C and rock alteration."

"Keberadaan struktur geologi merupakan salah satu parameter penting dalam menentukan zona permeabel pada suatu sistem geotermal. Penelitian ini dilakukan di salah satu area prospek geotermal di zona Sistem Sesar Sumatera (GSF) yang termasuk dalam segmen Angkola dan Barumun yang bertujuan untuk mengidentifikasi kemenerusan fitur permukaan hingga bawah permukaan terutama struktur geologi yang berkaitan erat dengan zona permeabel dengan mengintegrasikan data geologi, geokimia, dan geofisika. Teknologi remote sensing digunakan untuk mengidentifikasi struktur geologi yang terobservasi di permukaan yang dikorelasikan dengan persebaran manifestasi permukaan. Namun, tidak semua struktur geologi yang terobservasi di permukaan dapat diamati dan kemenerusannya dari permukaan hingga bawah permukaan dilakukan dengan pendekatan geofisika menggunakan data magnetotelurik (MT) dan gravitasi. Interpretasi struktur geologi permukaan berdasarkan analisis remote sensing dan persebaran manifestasi permukaan memiliki korelasi yang positif dengan hasil gravitasi adanya struktur graben dari zona GSF yang memiliki orientasi baratlaut-tenggara. Kelurusan dan karakteristik (arah dan kemiringan) struktur ditandai dengan adanya kontras nilai gravitasi, nilai Horizontal Gradient Magnitude (HGM) maksimum, dan nilai zero Second Vertical Derivative (SVD) serta analisis Multi Scale-Second Vertical Derivative (MS-SVD). Hasil interpretasi struktur bawah permukaan gravitasi berkorelasi positif dengan analisis parameter MT (splitting curve MT) yang dapat mengindikasi zona struktur bawah permukaan. Gabungan interpretasi struktur permukaan dan bawah permukaan teridentifikasi adanya 5 struktur (F1, F2, F3, F4, dan F5) yang diklasifikasikan sebagai Struktur Pasti (F1, F2, F3, dan F4) dan Struktur Diperkirakan (F5) yang memiliki orientasi baratlaut-tenggara. Struktur F3 yang berorientasi baratlaut-tenggara merupakan struktur utama yang berperan sebagai fluid conduit (zona permeabel) yang dibuktikan dengan adanya manifestasi mata airpanas bertipe klorida. Berdasarkan hasil pemodelan inversi 3-D MT dan pemodelan kedepan 2-D gravitasi dapat mendelineasi zona reservoir pada kedalaman 1500 – 2000-meter yang dikontrol oleh struktur F3 dan zona reservoir berasosiasi dengan batuan metasediment yang nantinya dapat menentukan lokasi sumur pengeboran. Untuk memvisualisasikan sistem geotermal secara komprehensif, maka dikembangkan model konseptual dengan mengintegrasikan model geofisika yang memiliki kualitas data optimum dengan data geologi dan geokimia yang saling berkorelasi, sehingga dapat dijadikan dasar dan acuan dalam menentukan lokasi pengembangan sumur produksi dan reinjeksi dan menurunkan resiko kegagalan dalam well targeting.

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The existence of geological structures is one of the important parameters in determining the permeability zone in a geothermal system. This study was conducted in one of the geothermal prospect areas in the Sumatera Fault System (GSF) zone included in the Angkola and Barumun segments which aims to identify the continuity of surface to subsurface features, especially geological structures that are closely related to permeability zones by integrating geological, geochemical, and geophysical data. Remote sensing technology is used to identify geological structures observed at the surface that are correlated with the distribution of surface manifestations. However, not all surface-observed geological structures can be observed and their continuity from the surface to the subsurface is done with a geophysical approach using magnetotelluric (MT) and gravity data. Interpretation of surface geological structures based on remote sensing analysis and the distribution of surface manifestations has a positive correlation with the gravity results of the graben structure of the GSF zone which has a northwest-southeast orientation. The alignment and characteristics (direction and slope) of the structure are characterized by the contrast of gravity values, maximum Horizontal Gradient Magnitude (HGM) values, and zero Second Vertical Derivative (SVD) values as well as Multi Scale-Second Vertical Derivative (MS-SVD) analysis. The results of gravity subsurface structure interpretation are positively correlated with MT parameter analysis (splitting curve) which can indicate subsurface structure zones. The combined interpretation of surface and subsurface structures identified 5 structures (F1, F2, F3, F4, and F5) classified as Certain Structures (F1, F2, F3, and F4) and Estimated Structure (F5) that have a northwest-southeast orientation. The northwest-southeast oriented F3 structure is the main structure that acts as a fluid conduit (permeability zone) as evidenced by the manifestation of chloride-type hot springs. Based on the results of 3-D MT inversion modeling and 2-D gravity forward modeling, it can delineate the reservoir zone at a depth of 1500 - 200 meters controlled by the F3 structure and the reservoir zone is associated with metasedimentary rocks which can later determine the location of drilling wells. To visualize the geothermal system comprehensively, a conceptual model was developed by integrating geophysical models that have optimum data quality with geological and geochemical data that are correlated, so that it can be used as a basis and guide in determining the location of production well development and reinjection and reduce the risk of failure in drilling targets."

"Daerah Gunung Pancar merupakan daerah prospek geotermal yang didominasi oleh batuan sedimen, batuan beku berumur kuartener dan intrusi andesit. Sistem geotermal pada daerah ini ditandai dengan keberadaan manifestasi outflow berupa hotsprings yang memiliki temperatur berkisar 45-66°C. Dari data geokimia yang ada, reservoir pada daerah ini diperkirakan memiliki temperatur sekitar 180-215°C sehingga diklasifikasikan sebagai sistem geotermal dengan suhu yang rendah hingga menengah. Penelitan ini menggunakan metode magnetik untuk mengidentifikasi batuan yang mengalami demagnetisasi akibat terjadi proses alterasi hidrotermal yang diasosiasikan dengan batuan reservoir pada sistem geotermal.Dari data magnetik, dilakukan koreksi data dengan koreksi IGRF dan koreksi diurnal untuk menhasilkan peta kontur anomali magnetik total yang bersifat dipol. Proses reduction to pole (RTP) dan upward continuation dengan ketinggian sebesar 50 m, 100 m, dan 250 m untuk melihat nilai anomali rendah akibat demagnetisasi. Pemodelan secara forward 2 dimensi menunjukkan reservoir memiliki suseptibilitas yang rendah dengan nilai 0.000013 cgs pada kedalaman 500-1400 m di bawah permukaan laut. Kemudian, pemodelan secara inversi 3 dimensi menunjukan nilai suseptibilitas sekitar -0.003 hingga 0.035 cgs sebagai reservoir yang berada pada kedalaman 500-1300 m di bawah permukaan laut. Hasil pemodelan forward 2 dimensi dan inversi 3 dimensi dikorelasikan dengan model inversi 3 dimensi data AMT dan forward 2 dimensi data gravity. Dari hasil interpretasi terpadu, reservoir terletak di sekitar zona outflow pada kedalaman 500-1300 m di bawah permukaan laut.

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The Gunung Pancar area is a geothermal prospect area dominated by sedimentary rocks, quaternary igneous rocks and andesite intrusion. The geothermal system in this area is characterized by the presence of outflow manifestations in the form of hotsprings which have temperatures ranging from 45-66 °C. From existing geochemical data, the reservoir in this area is estimated to have a temperature of around 180-215 °C so that it is classified as a geothermal system with low to medium temperatures. This research uses magnetic methods to identify rocks that have demagnetized due to hydrothermal alteration processes associated with reservoir rocks in geothermal systems. From magnetic data, data correction is done with IGRF correction and diurnal correction to produce a dipole total magnetic anomaly contour map. Reduction to pole (RTP) and upward continuation processes with a height of 50 m, 100 m, and 250 m to see the low anomaly values ​​due to demagnetization. 2-dimensional forward modeling shows the reservoir has a low susceptibility with a value of 0.000013 cgs at a depth of 500-1400 m below sea level. Then, 3-dimensional inversion modeling shows the susceptibility value around -0.003 to 0.035 cgs as a reservoir at a depth of 500-1300 m below sea level. The results of 2-dimensional forward modeling and 3-dimensional inversion are correlated with the 3-dimensional inversion model of AMT data and forward 2 dimensional gravity data. From the results of integrated interpretation, the reservoir is located around the outflow zone at a depth of 500-1300 m below sea level."

"ABSTRAKDaerah di sekitar kawasan X merupakan kawasan yang berupa dataran tinggi yang berada di kawasan kompleks vulkanik. Di kawasan ini terdapat kawah panas yang menunjukkan aktivitas hidrotermal, dimana manifestasi utamanya muncul di kawasan X berupa fumarol Cd. Salah satu sasaran dalam eksplorasi panas bumi adalah menemukan titik-titik pemboran yang berkorelasi dengan zona suhu tinggi dan zona yang memiliki kriteria permeabilitas tinggi, dimana zona tersebut berkorelasi dengan struktur geologi. Berdasarkan analisis kurva pemisahan dan diagram kutub, terdapat sesar Wp 1, Ga, Wp 2, Pk, Dg, Cd, dan Jm yang umumnya berarah barat laut-tenggara. Sistem panas bumi wilayah X terutama dikendalikan oleh sesar Cd. Adanya struktur sesar memungkinkan fluida dari kawasan timur Jm, Kaipohan Wp, dan sekitar kawasan Pk mengalir sebagai imbuhan. Selain itu, berdasarkan hasil inversi 3 dimensi, data magnetotelurik menunjukkan bahwa zona alterasi sebagian besar terkonsentrasi pada kedalaman sekitar 1500 m hingga 1000 m dengan indikasi bahwa batas zona konduktor (BOC) sudah mulai terlihat. pada ketinggian sekitar 1000 m dan zona reservoir berada pada kedalaman dibawah 1000. m yang ditunjukkan dengan nilai resistivitas sedang antara 20 - 63 Ωm. Zona resistif basement pada kedalaman -3000 m ditunjukkan dengan sebaran nilai resistivitas yang tinggi, dengan sumber utama didominasi oleh pegunungan Dm, Al, dan Jm dengan satuan litologi dominan berupa lahar andesit. Zona upflow kemungkinan terletak di sekitar prospek zona Cd atau di sekitar titik MT-37, dengan arah outflow ke barat daya. Berdasarkan pengukuran panas bumi, temperatur prospek utama diperkirakan 270 0C. Lokasi sasaran pemboran dapat ditarik di sekitar geothermal Cd dengan kedalaman pemboran yang dapat ditarik sekitar 1000 m sampai 1500 m di bawah permukaan.ABSTRACTThe area around area X is an area in the form of a plateau located in a volcanic complex area. In this area there are hot craters showing hydrothermal activity, where the main manifestation appears in region X in the form of fumarole Cd. One of the targets in geothermal exploration is to find drilling points that are correlated with zones of high temperature and zones that have high permeability criteria, where these zones are correlated with geological structures. Based on the analysis of the separation curve and polar diagram, there are faults Wp 1, Ga, Wp 2, Pk, Dg, Cd, and Jm which generally run northwest-southeast. The X region geothermal system is mainly controlled by the Cd fault. The existence of a fault structure allows fluid from the eastern region of Jm, Kaipohan Wp, and around the Pk area to flow as a recharge. In addition, based on the results of the 3-dimensional inversion, the magnetotelluric data shows that the alteration zone is mostly concentrated at a depth of about 1500 m to 1000 m with an indication that the conductor zone boundary (BOC) is already visible. at an altitude of about 1000 m and the reservoir zone is at a depth below 1000. m which is indicated by a moderate resistivity value between 20 - 63 Ωm. The basement resistive zone at a depth of -3000 m is indicated by the distribution of high resistivity values, with the main source being dominated by mountains Dm, Al, and Jm with the dominant lithological unit in the form of andesite lava. The upflow zone is likely located in the vicinity of the prospect zone Cd or around the point MT-37, with the outflow direction to the southwest. Based on geothermal measurements, the temperature of the main prospect is estimated to be 270 0C. The drilling target location can be drawn around the geothermal Cd with a drilling depth that can be drawn from about 1000 m to 1500 m below the surface."

"Potensi energi geotermal Indonesia merupakan yang terbesar di dunia, namun kini baru diutilisasi sekitar 4% dari potensi tersebut. Penelitian ini bertujuan mengoptimalkan penempatan sumur produksi geotermal di lapangan X agar risiko aktivitas pengembangan skema produksi dapat diminimalisasi. Pada penelitian ini dilakukan pemodelan dan simulasi reservoir dengan menggunakan data 3G (Geologi, Geofisika dan Geokimia) dari lapangan X dan data dari sumur yang telah ada. Dengan menggunakan TOUGH2, PETRASIM dan GeoSlicer-X, pemodelan forward yang mencakup adjustment dari litologi dan posisi sources dilakukan hingga model reservoir mencapai kondisi natural state. Data hasil simulasi reservoir kemudian diregresi menggunakan MATLAB serta dilakukan optimasi numerik guna mendapatkan titik-titik penempatan sumur produksi yang diajukan untuk penambahan kapasitas terpasang di lapangan X. Didapatkan hasil penelitian titik optimum penempatan sumur produksi pada koordinat x 3276 m dan y 4262 m dengan nilai entalpi spesifik maksimum 1529,9 kJ/kg; serta 6 titik penempatan sumur produksi dengan nilai entalpi spesifik 1500, 1450 dan 1400 kJ/kg. Dengan demikian, penambahan kapasitas terpasang dari skema produksi tambahan ini diestimasi dapat mencapai 43,5 MWe.

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Indonesia has the biggest estimated geothermal energy reserve in the world, but only 4% of that reserve currently utilized to generate electricity. The purpose of this research is to optimize the production well placements at X field to minimize the failure risk of production scheme development. In the research, reservoir modelling and simulation is conducted based on 3G (Geological, Geophysical and Geochemical) data and existing wells data. Forward modelling process, which covers the lithology and sources position adjustment, is executed with TOUGH2, PETRASIM and GeoSlicer-X to validate the reservoir model towards natural state condition.

Using MATLAB, the resulting data is regressed and used to numerically optimize the production well placement decision based on the fluid specific enthalpy. The new production scheme is proposed to further increase the installed capacity in X field. The final result is the optimal point of well placement; which is 3276 m in x coordinate and 4262 m in y coordinate with the maximum specific enthalpy value of 1529,9 kJ/kg and 6 (six) other points with specific enthalpy of 1500, 1450 or 1400 kJ/kg. Thus, the improvement of the installed capacity with the proposed production scheme is estimated to reach 43,5 MWe."