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Vertical Electrical Sounding Exploration of Groundwater in Kertajati, Majalengka, West Java, Indonesia Nugraha, Gumilar Utamas; CSSSA, Boy Yoseph; Nur, Andi Agus; Pranantya, Pulung Arya; Handayani, Lina; Lubis, Rachmat Fajar; Bakti, Hendra
Indonesian Journal on Geoscience Vol 8, No 3 (2021)
Publisher : Geological Agency

Continuously increasing population and progressive infrastructural development in the region of Kertajati International Airport, Indonesia, emphasize the need to develop a sustainable water supply network. Airport facilities require sufficient water resources, which can be obtained from surface water and groundwater. Groundwater exploration can provide necessary information for assessing water resources. The purpose of this study is to analyze the configuration of aquifers in the studied area. A Schlumberger array was used to carry out twelve vertical electrical soundings (VES) with AB/2 electrode spacing ranging from 1.5 m to 150 m. IPI2win software was used to qualitatively interpret the VES results and it suggested the presence of three distinct lithological units interpreted as clay, alluvial sand, and a Lower Quaternary formation. In general, resistivity values in the studied area can be divided into five resistivity categories: very low resistivity with values ranging from 1 Î©m to 10 Î©m, low resistivity with values ranging from 10 Î©m to 50 Î©m, medium resistivity with values ranging from 50 Î©m to 100 Î©m, high resistivity with values ranging from 100 Î©m to 200 Î©m, and very high resistivity with values > 200 Î©m. The geo-electric interpretation revealed three geo-electric layers: topsoil (1 - 144 â„¦ m), sand (1 - 298 â„¦ m), and clay (1 - 82 â„¦ m). Aquifers in the studied area are lithologically composed of sand. Clay is the dominant lithology in the studied area, so the presence of aquifers in this area is very limited, and thus the supply of groundwater is also limited. The exploitation of groundwater must be limited and controlled to maintain the sustainability of groundwater in the studied area.

Vertical Electrical Sounding Exploration of Groundwater in Kertajati, Majalengka, West Java, Indonesia Nugraha, Gumilar Utamas; CSSSA, Boy Yoseph; Nur, Andi Agus; Pranantya, Pulung Arya; Handayani, Lina; Lubis, Rachmat Fajar; Bakti, Hendra
Indonesian Journal on Geoscience Vol 8, No 3 (2021): in-press
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.8.3.359-369

Continuously increasing population and progressive infrastructural development in the region of Kertajati International Airport, Indonesia, emphasize the need to develop a sustainable water supply network. Airport facilities require sufficient water resources, which can be obtained from surface water and groundwater. Groundwater exploration can provide necessary information for assessing water resources. The purpose of this study is to analyze the configuration of aquifers in the studied area. A Schlumberger array was used to carry out twelve vertical electrical soundings (VES) with AB/2 electrode spacing ranging from 1.5 m to 150 m. IPI2win software was used to qualitatively interpret the VES results and it suggested the presence of three distinct lithological units interpreted as clay, alluvial sand, and a Lower Quaternary formation. In general, resistivity values in the studied area can be divided into five resistivity categories: very low resistivity with values ranging from 1 Î©m to 10 Î©m, low resistivity with values ranging from 10 Î©m to 50 Î©m, medium resistivity with values ranging from 50 Î©m to 100 Î©m, high resistivity with values ranging from 100 Î©m to 200 Î©m, and very high resistivity with values > 200 Î©m. The geo-electric interpretation revealed three geo-electric layers: topsoil (1 - 144 â„¦ m), sand (1 - 298 â„¦ m), and clay (1 - 82 â„¦ m). Aquifers in the studied area are lithologically composed of sand. Clay is the dominant lithology in the studied area, so the presence of aquifers in this area is very limited, and thus the supply of groundwater is also limited. The exploitation of groundwater must be limited and controlled to maintain the sustainability of groundwater in the studied area.

PENCITRAAN TAHANAN JENIS BAWAH PERMUKAAN DI AREA PROSPEK PANAS BUMI GUNUNG SLAMET BERDASARKAN DATA MAGNETOTELURIK Dadan Dani Wardhana; Johanes Hutabarat; Andi Agus Nur; Karit Lumban Gaol
JURNAL RISET GEOLOGI DAN PERTAMBANGAN Vol 27, No 1 (2017)
Publisher : Indonesian Institute of Sciences

Magnetotelluric (MT) method has been applied to identify subsurface structures in Guci Geothermal Area, Mount Slamet. The objective of this research is to analyze the subsurface configuration based on the resistivity value beneath the Bojong district, Tegal regency, Central Java province. Stages of data processing started with transforming the data from the time domain to the frequency domain, and then graphing resistivity apparent to frequency and graph phase versus frequency, smoothing the graph and the last, inversion modeling with final result of 2D resistivity cross section. The results of data processing magnetotelluric (MT) revealed three groups of rock resistivity value. The high resistivity value (> 1000 Ω.m) represented the basement as a heat source. Low resistivity value (<10 Ω.m) is interpreted as alterated rocks that became cap rock. The resistivity value between 10-225 Ωm assosiaed with the porous and permeable rocks that store thermal fluids as the geothermal reservoir. The other layer with resistivity value 225-1000 Ωm might be as Tertiary sediment. Base on MT resistivity crosss section, the location that may have geothermal prospects, namely in the area of Guci depression, with a reservoir thickness of 600-1000m and at 750-1600m depth that covered by alterated rocks as cap rocks. AbstrakPenelitian geofisika dengan menggunakan metode magnetotellurik (MT) telah dilakukan untuk mengidentifikasi struktur bawah permukaan kawasan panas bumi Guci, Gunung Slamet. Tujuan penelitian untuk menganalisis struktur bawah permukaan berdasarkan distribusi nilai tahanan jenis ini dilakukan di kawasan yang terletak di Kecamatan Bojong, Kabupaten Tegal, Provinsi Jawa Tengah. Tahap pengolahan data dimulai dengan mengubah data dari domain waktu ke domain frekuensi, kemudian pembuatan grafik tahanan jenis semu terhadap frekuensi dan grafik fase terhadap frekuensi, smoothing grafik dan terakhir pemodelan inversi dengan hasil akhir berupa penampang tahanan jenis 2D. Hasil pengolahan data magnetotelurik (MT), menunjukkan ada tiga kelompok nilai tahanan jenis batuan. Nilai tahanan jenis tinggi (>1000 Ω.m) berkaitan dengan batuan dasar sebagai sumber panas. Nilai tahanan jenis rendah (<10 Ω.m) ditafsirkan sebagai batuan ubahan yang menjadi batuan penudung. Nilai tahanan jenis antara 10-225 Ωm berasosiasi dengan lapisan batuan yang bersifat poros dan permeabel yang menyimpan fluida panas, dapat berperan sebagai reservoir panas bumi. Lapisan lain dengan nilai tahanan jenis antara 225-1000 Ωm kemungkinan sebagai batuan sedimen Tersier. Dari kajian penampang tahanan jenis MT, lokasi yang kemungkinan mempunyai prospek panas bumi, yaitu di daerah depresi Guci, dengan ketebalan reservoir 600- 1000 m pada kedalaman 750-1600 m yang ditutupi oleh lapisan penudung berupa batuan ubahan.

Vertical Electrical Sounding Exploration of Groundwater in Kertajati, Majalengka, West Java, Indonesia Gumilar Utamas Nugraha; Boy Yoseph CSSSA; Andi Agus Nur; Pulung Arya Pranantya; Lina Handayani; Rachmat Fajar Lubis; Hendra Bakti
Indonesian Journal on Geoscience Vol 8, No 3 (2021)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.8.3.359-369

DOI:10.17014/ijog.8.3.359-369Continuously increasing population and progressive infrastructural development in the region of Kertajati International Airport, Indonesia, emphasize the need to develop a sustainable water supply network. Airport facilities require sufficient water resources, which can be obtained from surface water and groundwater. Groundwater exploration can provide necessary information for assessing water resources. The purpose of this study is to analyze the configuration of aquifers in the studied area. A Schlumberger array was used to carry out twelve vertical electrical soundings (VES) with AB/2 electrode spacing ranging from 1.5 m to 150 m. IPI2win software was used to qualitatively interpret the VES results and it suggested the presence of three distinct lithological units interpreted as clay, alluvial sand, and a Lower Quaternary formation. In general, resistivity values in the studied area can be divided into five resistivity categories: very low resistivity with values ranging from 1 Ωm to 10 Ωm, low resistivity with values ranging from 10 Ωm to 50 Ωm, medium resistivity with values ranging from 50 Ωm to 100 Ωm, high resistivity with values ranging from 100 Ωm to 200 Ωm, and very high resistivity with values > 200 Ωm. The geo-electric interpretation revealed three geo-electric layers: topsoil (1 - 144 Ω m), sand (1 - 298 Ω m), and clay (1 - 82 Ω m). Aquifers in the studied area are lithologically composed of sand. Clay is the dominant lithology in the studied area, so the presence of aquifers in this area is very limited, and thus the supply of groundwater is also limited. The exploitation of groundwater must be limited and controlled to maintain the sustainability of groundwater in the studied area.

Tectonic Control of the Nanggulan Formation Based on Morphometric Analysis in Kulon Progo, Indonesia Winarti Winarti; Emi Sukiyah; Ildrem Syafri; Andi Agus Nur
Indonesian Journal on Geoscience Vol 9, No 2 (2022)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.9.2.147-157

DOI:10.17014/ijog.9.2.147-157Outcrop of Nanggulan Formation, surrounded by Old Andesite Formation (OAF) in the eastern part of Kulon Progo Dome, is very limited. Tectonic control is interpreted as a contributing factor. Tectonic activity can be shown by a morphometric aspect. The research purpose was to calculate the valley floor - valley height ratio, stream gradient index, and drainage density of Nanggulan and Old Andesite Formations. The method used is field survey and Shuttle Radar Topography Mission analysis. The field survey focused on Clumprit, Klepu, and Kalisonggo Rivers. The total number of valley segments for the Nanggulan Formation is 223 with the valley length of 4.62 km, while OAF is 101 with a valley length of 3.55 km. SRTM analysis showed that the valley segment in OAF was 55, and valley length was 1.48 km. The valley floor - valley height ratio measured in the Nanggulan Formation is ten valleys and OAF is eight valleys. In Nanggulan Formation, the valley floor - valley height ratio value is from 1.00 to 5.46 (low uplift), whilst in OAF, the results vary: as 1.35 to 4.58 (low uplift), 0.59 (medium uplift), and 0.43 (high uplift). The stream gradient index value of the Nanggulan Formation is 460.47 (medium tectonic), while OAF is 723.84 (high tectonic). The drainage density value of the Nanggulan Formation is 10.35 km/km2 (very smooth landscape texture) and OAF is 10.35 km/km2 (somewhat smooth landscape texture). Morphometry proves that Nanggulan Formation tectonic activity is more active, causing the Nanggulan Formation to be exposed to the surface.

Kontak Formasi Nanggulan dan Andesit Tua di G. Mujil, Kulon Progo-Yogyakarta Winarti Winarti; Emy Sukiyah; Ildrem Syafri; Andi Agus Nur
KURVATEK Vol 6 No 1 (2021): April 2021
Publisher : Institut Teknologi Nasional Yogyakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.33579/krvtk.v6i1.2086

Penyebaran Formasi Nanggulan di sisi timur Pegunungan Kulon Progo sangat terbatas. Di sekitar G. Mujil, Formasi Nanggulan dijumpai berada di bawah Formasi Andesit Tua. G. Mujil membentuk morfologi menonjol yang dinamakan sebagai tumor Nanggulan. Formasi Nanggulan dapat tersingkap di permukaan disebabkan oleh 2 (dua) faktor yaitu pertama breksi yang bersifat kaku dan berat menekan batuan sedimen yang plastis, serta kedua adanya sesar naik. Hipotesis dalam penelitian ini adalah kontak antara Formasi Nanggulan dan Andesit Tua dapat sebagai kontak stratigrafi atau sesar. Tujuan penelitian adalah untuk mengidentifikasi pola kontak antara Formasi Nanggulan dengan Andesit Tua, khususnya di G. Mujil dengan pendekatan data permukaan dan bawah permukaan. Metode yang dipergunakan adalah studi geologi dan pengukuran gayaberat. Pengukuran gayaberat menggunakan sistem looping, dengan jumlah titik sebanyak 19. Alat yang dipergunakan terdiri dari Gravitimeter LaCoste & Romberg G-118 MVR serta Global Positioning System (GPS) Trimble Navigations 4600 LS. Data lapangan menunjukkan jika kontak antara Formasi Nanggulan dengan Andesit Tua berupa kontak stratigrafi secara vertikal, dengan batas kontak formasiergelombang. Nilai densitas Formasi Nanggulan sebesar 2,5 gr/cm3, sedangkan Formasi Andesit Tua sebesar 2,7 gr/cm3. Anomali yang muncul di G. Mujil disebabkan karena berbedaan litologi, sehingga kontak antara Formasi Nanggulan dan Andesit Tua merupakan kontak stratigrafi. Kata kunci: Kontak formasi, Gayaberat, G. Mujil, Tumor

A SUCCESS CASE OF WIDURI AREA REJUVENATION, ASRI BASIN, OFFSHORE SE SUMATRA BLOCK, INDONESIA Dwandari Ralanarko; Ildrem Syafri; Abdurrokhim Almabrury; Andi Agus Nur
BULLETIN OF THE MARINE GEOLOGY Vol 36, No 2 (2021)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.32693/bomg.36.2.2021.704

INTA/B Field is one of the most producing mature fields in Widuri Area, Asri Basin, Offshore SE Sumatera, Indonesia, therefore it is subjected to rejuvenation to enhance hydrocarbon production. INTA/B Field is distinguished from other fields from its featured anticlinal structures that have the northeast-southwest trending. This structure is heavily faulted mainly in the up-thrown south side of a major normal fault. Two structural configurations with various oil-water contact have successfully been identified within the field. The most of oil reserves are preserved in the western lobe in which Intan-1 sands. One of the most important reservoirs in this field is Talangakar (TAF) sand deposited as a meandering river system that streamed from the northwest to the southeast within the basin. Two main reservoirs, Gita-34A and Gita-34B are correlated throughout the field and interpreted as Miocene fluvio-channel sands. These two channels are thickened moderately from southwest to northeast which has descriptions as follows: fine- to-coarse grains, unconsolidated to friable, and low cementing materials.INTA/B Field has been produced for 25 years and currently undergoing a watered-out phase. Therefore, an integrated study is subjected to overcome this issue for mature field rejuvenation. The integrated study ranged from geology (e.g., depositional environment and facies analysis), geophysics (e.g., revisiting and reprocessing of seismic attributes), petrophysical calculation, and reservoir engineering (e.g., water conformance plot and volumetric calculation).This integrated study has successfully rejuvenated a mature field resulting and added a significant number in oil production with an average of 300 BPOD/well. The extended project is estimated to have a similar result to the forward pilot.

DISTRIBUTION OF SUBSURFACE QUATERNARY SEDIMENT IN SOUTH BINTAN ISLAND WATERS AS A POTENTIAL HEAVY MINERAL PLACER OR RARE EARTH ELEMENT DEPOSIT BASED ON SEISMIC INTERPRETATION Muhammad Zulfikar; Nazar Nurdin; Noor Cahyo Dwi Aryanto; Ildrem Syafri; Budi Muljana; Andi Agus Nur
BULLETIN OF THE MARINE GEOLOGY Vol 36, No 1 (2021)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.32693/bomg.36.1.2021.705

Bintan Island is one of the areas traversed by the Southeast Asian granitoid belt which is known to have the potential for heavy mineral placer deposits. Due to the dwindling presence of heavy mineral placer deposits in land areas, it is necessary to look for the potential presence of heavy mineral placer deposits in water areas. Searching for placer heavy mineral deposits accomodation in these waters requires subsurface mapping.The method used in this subsurface mapping is a single channel seismic method with a total of 179 lines in the direction of northeast – southwest and west – east. The results of this seismic recording are then interpreted the boundaries of the seismic facies unit and distributed using the kriging method. Furthermore, the thickness calculates by using the assumption velocity 1600 m/s.Based on the facies unit boundaries that have been interpreted, the quaternary sediments that formed in the study area are divided into 2 types of units, namely: Unit 2 which is estimated to be fluvial – transitional sediment, and Unit 1 which is estimated to be transitional sediment – shallow sea. There is also a difference in thickness patterns in these two units, where unit 2 shows a pattern of sediment thickening that resembles a paleochannel trending northeast – southwest, while unit 1 is relatively uniform.From the results of this study, it can be said that the area that has potential for heavy mineral placer deposits is in the west - center of the southern waters of Bintan Island. Where the potential for heavy mineral placer deposits should be in the paleochannel deposits that are part of Unit 2.

Study of Granitoid Distribution at Toboali Waters, Bangka Belitung Province: Seismic data interpretation approach Muhammad Zulfikar; Noor Cahyo Dwi Aryanto; Andi Agus Nur; Ildrem Syafri
BULLETIN OF THE MARINE GEOLOGY Vol 35, No 2 (2020)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.32693/bomg.35.2.2020.681

Bangka Island is one of the islands in Indonesia which is traversed by Southeast Asia granitoid belt. This belt stretches from Burma (Myanmar) to Bangka Belitung. This granitoid has potential as a source rock of mineral that carrying tin and rare earth element. At present, mapping of granitoid rocks to the waters area is rarely published, so acoustic basement mapping is necessary to do in order to determine the distribution of granitoids in Toboali waters. The research method used is a single channel seismic with an energy source of 300 joules. The sound source uses a single plate boomer, so it has a high enough resolution but the penetration is not deep enough. Acoustic basement in Toboali waters varies in depth from 15 - 75 ms or getting deeper south. When viewed from the continuity of the acoustic basement, it is estimated that the granitoid is 7 km from the nearest coastline.Key words: single channel seismic, seismic interprtation, granitoid distribution, Toboali Waters, Bangka Belitung ProvincePulau Bangka merupakan salah satu pulau di Indonesia yang dilalui oleh jalur granitoid Asia Tenggara. Jalur ini membentang dari Burma (Myanmar) hingga Bangka Belitung. Granitoid ini memiliki potensi sebagai batuan sumber pembawa mineral timah dan unsur tanah jarang. Pada saat ini pemetaan batuan granitoid pada daerah perairan jarang dipublikasikan, sehingga pemetaan batuan dasar akustik perlu dilakukan dalam rangka mengetahui sebaran granitoid di Perairan Toboali. Metode penelitian yang digunakan yaitu seismik single channel dengan sumber energi yang dikeluarkan sebesar 300 joule. Sumber suaranya menggunakan boomer single plate, sehingga memiliki resolusi yang cukup tinggi akan tetapi penetrasinya tidak cukup dalam. Batuan dasar akustik di Perairan Toboali memiliki kedalaman bervariasi mulai dari 15 – 75 ms atau semakin ke selatan semakin dalam. Jika dilihat dari kemenerusan batuan dasar akustiknya diperkirakan granitoid tersebut berada 7 km dari garis pantai terdekat.Kata kunci: Seismik single channel, interpretasi seismik, distribusi granitoid, Perairan Toboali, Provinsi Bangka Belitung

Application of Spectral Decomposition and RGB Blending for Delineation of “S” Channel At Asri Basin Swasty Aninda Piranti; Shaska Zulivandama; Noor Cahyo Dwi Aryanto; Andi Agus Nur; Ildrem Syafri
BULLETIN OF THE MARINE GEOLOGY Vol 35, No 2 (2020)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.32693/bomg.35.2.2020.688

Gita member is part of Talang Akar Formation is known as hydrocarbon reservoir at Asri Basin, eastern part of South Sumatra. This formation consists of several depositional systems such as braided channel, meandering channel, fluvial-deltaic, and estuarine system. A channel system was an interesting system developed in the Asri Basin, however, to get the channel distribution in Asri Basin is quite challenging because the thickness of the channels caused its appearance is generally close or under seismic resolution, the existence of coal below our target also affects the impression of “S” sand on seismic data. In this study, spectral decomposition and RGB Blending have been successful to identify “S” sand. RGB Blending map is extracted from 15 Hz as low frequency, 45 Hz as middle frequency, and 75 Hz as high frequency. Our interpretation was applied at RGB Blending map and reveal the “S” sand is classified as a meandering channel depositional system with the main direction of the channel is Northeast – Southwest.Keywords: spectral decomposition, RGB Blending, Gita reservoir, Asri Basin: Anggota Gita merupakan bagian dari Formasi Talang Akar yang dikenal sebagai reservoar hidrokarbon di Cekungan Asri, Sumatra Selatan bagian timur. Formasi ini terdiri dari beberapa sistem pengendapan seperti sistem sungai teranyam, meander, fluvial-delta, dan estuari. Sistem pengendapan sungai purba di Cekungan Asri merupakan sistem yang menarik untuk dieksplorasi namun untuk mendapatkan persebaran sungai tersebut merupakan hal yang menantang dikarenakan tipisnya ketebalan sungai yang mengakibatkan kenampakannya pada data seismik berada disekitar atau bahkan dibawah resolusi seismik, keberadaan lapisan batubara dibawah target turut mempengaruhi kenampakan pasir “S” pada data seismik. Dekomposisi spektral serta RGB Blending yang diaplikasikan pada penelitian ini dapat mengidentifikasi pasir “S”. Peta RGB Blending diekstraksi dari beberapa frekuensi, yaitu frekuensi 15 Hz yang diambil sebagai frekuensi rendah, 45 Hz sebagai frekuensi tengah, dan 75 Hz sebagai frekuensi tinggi. Selanjutnya dilakukan interpretasi pada peta hasil RGB Blending dan menunjukkan pasir “S” diklasifikasikan sebagai sungai dengan sistem meander dengan arah utama sedimentasi adalah Timurlaut - Baratdaya.Kata kunci: dekomposisi spektral, RGB Blending, reservoar Gita, Cekungan Asri

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