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"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."

"ABSTRAKLapangan geotermal Sibayak berada di Sumatera Utara dengan ketinggian antara 1400 sampai 2200 m dengan keberadaan tiga vulkano aktif. Potensi dari lapangan geotermal Sibayak mencapai 40 MWe, namun saat ini kapasitas yang dieksplorasi baru mencapai 12 MWe. Area pemboran yang produktif berasosiasi dengan zona reservoir memiliki ciri yaitu area dengan temperatur dan permeabilitas tinggi. Daerah dengan permeabilitas tinggi ini biasanya disebabkan oleh banyaknya rekahan-rekahan. Pengukuran resistivitas dengan metode mise-a-la-masse merupakan cara yang dapat digunakan untuk mengetahui zona rekahan dengan permeabilitas tinggi. Data pendukung juga diperlukan seperti data geologi, geokimia, dan data sumur. Pembuatan model menggunakan metode inversi smoothness constrained least squares. Nilai resistivitas rendah menunjukkan adanya rekahan-rekahan bawah permukaan. Hasil yang diperoleh menunjukkan tiga zona permeabel yaitu high permeability di bagian utara sumur SBY-4 atau sekitar Gunung Sibayak, moderate permeability dekat sumur SBY-3 dan SBY-4, dan low permeability di bagian selatan dekat kaldera. Rekomendasi potensi lokasi sumur pemboran produksi berada di daerah upflow yang bertemperatur tinggi dan permeabilitas tinggi, yaitu di sebelah utara sumur SBY-4.

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ABSTRACT

Sibayak geothermal field located in Sumatera Utara with elevation around 1400 until 2200m and surround by three active volcanoes. The potential of the Sibayak geothermal field reaches 40 MWe, but currently the explored capacity has only reached 12 MWe. Productive drilling areas associated with reservoir zones are characterized by areas with high temperature and permeability. This area with high permeability is usually caused by many fractures. Resistivity measurement using the mise-a-la-masse method is a method that can be used to determine the zone of fracture with high permeability. Supporting data is also needed such as geological, geochemical and well data. Modeling uses the smoothness constrained least squares inversion method. Low resistivity values ​​indicate the existence of subsurface fractures. The results obtained showed three permeable zones which is high permeability in the northern part of the SBY-4 well or around Mount Sibayak, moderate permeability near the SBY-3 and SBY-4 wells, and low permeability in the southern part near the caldera. The recommendation for the potential location of the production drilling well is in the high temperature and high permeability upflow area, which is to the north of the SBY-4 well."

"Geothermal System Modeling has been illustrates Using Magnetotelluric Method. This method utilize a natural source Waves which are come from solar Wind, or the other Electromagnetic Waves in an ionosphere. Earlier data has been process with frequency sorting for gets the right signal points and remove noises. Then the Cokriging method utilized to remove the distortion effect With Static shift correction. After Data processing phases are finished, 2D Inversion, and 3D visualization of MT data are needed. And then for illustrates good geothermal system modeling, We must integrated MT and the others data, like geology or geochemistry data.

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Dilakukan pemodelan sistem geothermal dengan menggunakan metode Magnetotelluric (MT). Metode ini menggunakan sumber alami gelombang (natural Source) yang berasal dari solar Wind, ataupun gelombang elektromagnetik lainnya yang ada di ionosfer. Pengolahan data dilakukan dengan melakukan pemilahan frekuensi yang tepat untuk mendapatkan sinyal yang dapat merepresentasikan keadaan subsurface serta untuk menghilangkan noise. Dilakukan pula koreksi pergeseran static menggunkan metode cokriging untuk menghilangkan efek distorsi. Setelah tahap pengolahan data selesai dilakukan proses inversi data MT, Visualisasi 3-Dimensi, serta dilakukan integrasi terpadu terhadap data-data yang lain, baik geologi ataupun geokimia guna mendapatkan pemodelan dari suatu system geothermal."

"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."

"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.

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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 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."

"Sistem panasbumi lapangan "D" merupakan sistem panasbumi tipe kaldera yang terbentuk karena aktivitas tektonik dan vulkanik. Formasi batuannya merupakan formasi sedimen berumur tersier di bagian bawah, dengan formasi batuan beku berumur kuarter di bagian atasnya. Manifestasi permukaan yang ada berupa fumarol di atas Gunung Taf dan Gunung "D" serta mata air panas pada arah tenggara dari pusat sistem. Data MT menunjukkan adanya up-dome shape sedangkan data gravity menunjukkan keberadaan reservoar yang ditandai dengan anomali gravitasi rendah. Untuk memahami karakteristik reservoar, letak sumber panas, serta hidrogeologi, dilakukan pemodelan sistem panasbumi lapangan "D". Pemodelan dilakukan secara forward dengan software TOUGH2 dan inversi dengan software iTOUGH2. Input pemodelan forward dibuat berdasarkan data geologi, geofisika, geokimia, dan data sumur. Output yang dihasilkan digunakan sebagai input untuk proses inversi dengan tujuan optimalisasi model Natural State yang ingin dicapai. Ketercapaian kondisi natural state ditunjukkan dengan adanya kesesuaian antara profil temperatur sumur dengan hasil pemodelan. Hasil pemodelan menunjukkan bahwa sumber panas berada di bawah Gunung Taf dan Gunung "D", dengan outflow ke arah tenggara, serta keberadaan zona recharge di sebelah barat daya dari sistem. Top reservoar diperkirakan berada pada elevasi 0 m. Dari profil temperatur juga diberikan rekomendasi wilayah yang tepat sebagai sumur produksi dan sumur reinjeksi.

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Geothermal system at field "D" is a caldera-type system which was developed by volcanism and tectonism activities. The "D" area composed of pre-Tertiary-Tertiary sedimentary formation in the lower part, and unconformably covered by Quaternary volcanic rock formation. Surface manifestations present in this area are fumaroles right above Mount Taf and Mount "D" and hot-springs in north east and south east direction from the center of the system. MT data inform the present of up-dome shape, while gravity data show the reservoir location with low gravity anomaly. For understanding the characteristic of reservoir, heat source location, and hydrogeology, the modeling of geothermal system at field "D" was conducted using TOUGH2 and iTOUGH2 simulator in forward and inverse modeling respectively. Input for forward modeling were composed based on geological, geophysical, geochemical and well-bore data.

The calculated output from forward modeling was then used as input data for inversion process in order to optimize the Natural State condition being obtained. Natural State condition is reached when the temperature profiles of the model show relatively good agreement with measured temperature from wells. The result indicates that the heat source is located beneath Mount Taf and Mount "D", with present outflow to the south east and north east direction outward the system, while recharge zones are located at south west and north west from the system. Top of reservoir was estimated to be 200 m above sea level. Recommendation for production and reinjection wells is also given based on measured temperature profiles."

"Area prospek geothermal Tawau, Sabah, Malaysia salah satu daerah prospek di Malaysia yang terbentuk karena proses tektonik di daerah Sulu, dengan formasi batuan kuarter. Area prospek geothermal ini memiliki mata air panas tipe klorida, mata air panas tipe steam-heated, dan mata air panas tipe bikarbonat yang keseluruhannya tersebar di sekitar area prospek. Dari hasil perhitungan geotermometri diperoleh area prospek geothermal Tawau memiliki temperatur 190-236 0C, yang dapat dikategorikan sebagai moderate to high temperature geothermal system. Untuk mengetahui mengenai batas, kedalaman, dan geometri dari reservoir yang ada, dilakukan pengukuran dengan metode Magnetotellurik (MT) dan Time Domain Electromagnetic (TDEM). Pengukuran dilakukan dengan desain gridding agar dapat diketahui penyebaran resistivitas dari arah Utara-Selatan maupun Barat-Timur. Data MT tersebut dikoreksi terlebih dahulu terhadap efek statik dan noise dengan menggunakan TDEM dan Remote Reference sebelum nantinya siap diinterpretasi. Pemodelan sistem geothermal dari data magnetotellurik dengan menggunakan analisa 2-dimensi dan visualisasi 3-dimensi. Diperoleh hasil area prospek geothermal ini memiliki luas reservoir sekitar 15 km2, dan potensi untuk dikembangkan menjadi pembangkit listrik mencapai 84 MW, dengan rekomedasi pengeboran yang berada di dekat gunung Maria di bagian Utara Tawau.

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Geothermal prospect area in Tawau, Sabah, Malaysia is one of the prospect area developed by tectonic process in Sulu, with quaternary formation. This geothermal prospect area has chloride, steam-heated, and bicarbonate hot springs. Based on geothermometry calculation the geothermal prospect area of Tawau has temperature 190-236 0C which is categorized as a moderate to high temperature geothermal system. To estimate the boundary, depth, and geometry of the reservoir, Magnetotelluric (MT) and Time Domain Electromagnetic (TDEM) methods were used. Data acquisition was designed gridding method to delineated resistivity distribution in North-South or West-East orientation. MT data was then corrected for static effect and possible noise using TDEM and remote reference before comprehensive interpretation. Modeling of the geothermal system was carried out by using 2-dimensional MT resistivity and 3-dimensional visualization. As a result we could delineated the geothermal prospect area is about 15 km2 with its potential of up to 84 MWe. In addition, the with drilling recommendation is proposed is the promising zone (close to Mt. Maria flank)."

"Pemahaman kondisi reservoir merupakan salah satu aspek penting dalam aktivitas monitoring proses produksi fluida dalam sistem panas bumi. Langkah awal manajemen reservoir bagi Lapangan Panas Bumi FR yang baru berproduksi sejak tahun 2014 perlu dilakukan. Penelitian ini bertujuan mendelineasi reservoir khususnya fasa uap menggunakan metode tomografi waktu tunda. Penelitian ini menggunakan data seismogram yang diukur selama 95 hari yang direkam oleh 11 stasiun perekaman. Hasil picking waktu tiba mendapatkan 215 kejadian gempa mikro dengan minimal terekam oleh 3 stasiun perekaman. Distribusi hiposenter awal menunjukkan posisi episenter cenderung mengkluster pada sumur produksi akan tetapi dari segi kedalaman hiposenter masih terdapat fix depth pada elevasi 1170 masl, oleh sebab itu masih diperlukan proses relokasi hiposenter. Relokasi hiposenter dilakukan dengan dua metode secara kombinasi yaitu menggunakan metode Joint Hypocenter Determination (JHD) dan metode double difference. Selanjutnya dilakukan proses tomografi waktu tunda menggunakan perangkat lunak simulsp12. Hasil distribusi relokasi hiposenter menunjukkan satu cluster di sekitar sumur produksi utama yaitu sumur B dan C. Sedangkan dari segi kedalaman hiposenter terdistribusi cluster disekitar trajectory sumur produksi B dan C dari elevasi 1000 sampai 0 masl dengan residual waktu tempuh antara 0.2 sampai 0.4 detik. Hasil tomogram menunjukkan bahwa pada elevasi sekitar 2000 sampai 1000 masl diduga sebagai zona batuan yang mengandung air dengan tingkat alterasi yang cukup besar yaitu zona clay cap dengan nilai VP/VS berkisar 1.73. Sedangkan dugaan zona uap berada pada elevasi 1000-500 masl dengan nilai VP/VS berkisar 1.67-1.7 melampar sepanjang Kawah Ciwidey dengan Kawah Putih. Selanjutnya dilakukan rekonstruksi model konseptual sederhana Lapangan Panas Bumi FR Jawa Barat dengan mengintegrasikan antara data utama penelitian yaitu tomografi microearthquake dan distribusi hiposenter yang sudah terelokasi dengan data pendukung berupa line penampang metode MT 2-D, section vertikal geologi berdasarkan data cutting sumur, profiling sumur temperatur serta lokasi sumur ekstraksi untuk memberikan arah fluida.

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Understanding reservoir conditions is one of the important aspects in fluid production monitoring activity in geothermal systems. The initial step of reservoir management in the FR Geothermal Field which has only been producing since 2014 needs to be done. The object of this study to delineate the reservoir elemen especially the vapor phase using the tomography delay time method. This research used seismogram data measured for 95 days recorded by 11 seismometers. Arrivals time picking results get 215 micro earthquake events with a minimum recorded by 3 recording seismometers. The initial hypocenter distribution shows that the position of the epicenter tends to cluster in production wells but in terms of hypocenter depth there still fix depth at 1170 masl, therefore hypocenter relocation is still needed. Hypocenter relocation is done by two methods in combination. The first use Joint Hypocenter Determination (JHD) and second Double difference relocation method. Then the delay time tomography invers is using simulsp12 software.

The results of the hypocenter relocation distribution show one cluster around the main production wells that are wells B and C. While in terms of hypocenter depth distributed clusters around the trajectory of production wells B and C from elevations 1000 to 0 masl with a residual travel time of 0.2 to 0.4 seconds. The tomogram results show that at an elevation arround elevation 2000 to 1000 masl it is prediction that the zone containing water with a considerable alteration rate or usually calls of clay cap zone with a value of Vp / Vs ranging from 1.73. While the prediction steam zone is at an elevation of 1000-500 masl with a value of Vp / Vs ranging from 1.67-1.7 on the part between Ciwidey Crater and Putih Crater. The reconstruction of a simple conceptual model of West Java FR Geothermal Field by integrating the main data likes hypocenter distribution that has been relocated and microearthquake tomography with supporting data in the form of cross section MT 2-D method, geological vertical section based on well cutting data, profiling temperature wells and location of extraction wells to provide fluid direction."