Publications of Research Center for Geotechnology, Indonesian Institute of Sciences
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Wireline logs vs drilling events: Which one to believe in implying subsurface pressure?
Full text linkAs generally known, subsurface pressure can be implied using both wireline logs and drilling events. However, there may be a case where wireline logs and drilling events do not indicate the same subsurface pressure. Data from four vertical wells located in the South Sumatra Basin, Indonesia, were analyzed as a case study. Two wells, Wells A and D, encountered high overpressured zones, confirmed by drilling events and wireline logs data. The two others, Wells B and C, only encountered low overpressured zones, inferred by the relatively low mudweight used during the drilling. However, the wireline logs of Wells B and C show a reversal as Wells A and D. There are two hypotheses to explain the condition in Wells B and C. First, the wireline logs reversal is due to shallow carbonate cementation. Second, Wells B and C were drilled in an unintentional underbalanced condition. The method used includes XRD, SEM, and titration analysis. The results show that the first hypothesis is false, while the second is true. It may be due to some missing information related to drilling events in the final well report of Wells B and C
CHARACTERIZATION OF ROCK LAYERS BASED ON REFRACTION SEISMIC METHOD: A CASE STUDY OF MENTARANG’S HYDRO-POWER PLANT, MALINAU REGENCY, NORTH KALIMANTAN
No full textNorth Kalimantan Province is a new province that is dynamic in development in order to prosper the inhabitants. The research and exploration to make a plan to develop new renewable energy are one of their main programs. The hydro-power plant of Mentarang, Malinau Regency, Kalimantan Utara is a plan program in 2020. The research study of hydro-power plants is essential as a reference in the development plan and avoids the hazard, miss calculation due to human error, etc. Seismic refraction is used in the feasibility study and detailed engineering study (FS DED) of Mentarang's Hydro-power plant. Analysis from the Seismic refraction method can be used as an input parameter for deciding the feasibility of Mentarang's hydro-power plant. This study aims to characterize the sub-surface layers, structure, and sub-surface layer thickness within this area. The seismic refraction method uses the intercept time or travel-time versus distance and processed using the reciprocal method, then it is modelled using inversion and resulted in a 2D profile. This research study was used the seismic refraction method with geometry acquisition of 14 sources with two spread and 5 meters of geophone interval. The analysis result of the 2D inversion profile model, in general, is classified as four strata layers. These strata are categorized as weathered layers with 5-15 meters of thickness, clay, and Sandstone about 5-20 meter of layer thickness, Sandstone with the layer thickness of about 20-50 meters, and lastly, granite, lava rocks, or limestone with depth more than 70 meters below the subsurface. There is a possibility of a structure at an offset of 70 meters, but this method's limitation will overestimate the conclusion. Therefore, it is necessary to bring another method that more sensitive to work further in research study evaluation of hydro-power plant Mentarang, Malinau Regency, North Kalimantan.
BIOSTRATIGRAPHY ANALYSIS OF BARBATOS-1 EXPLORATION WELL IN TOMORI BLOCK, BANGGAI BASIN, EAST ARM OF SULAWESI
Full text linkA biostratigraphic analysis was carried out on 60 samples taken from the Barbatos-1 Well, located within the Tomori Block, Banggai Tertiary Basin, East Arm of Sulawesi. The Barbatos-1 well was selected for this study because it is composed of rock sequences which are the main reservoir in the Tomori Block. Biostratigraphic analysis was conducted to determine the relative age and depositional environment of the sample. The age of the sample is determined based on the interval zone. The depositional environment is estimated basedon the ratio of plankton (P/B ratio) and fossil facies. The results revealed that the rock formations studied were deposited in the Miocene to Holocene age. The lowest layer is the Orbulina bilobata-Zone which was deposited at N10 – N12 (lower Middle Miocene) in the bathyal environment. The layer above is a biozonation of Globorotalia menardii, deposited at N12 – N14 (upper Middle Miocene) in a neritic environment. The next layer is the biozonation of Sphaeroidinella subdehiscens – Globigerina praebulloides which wasdeposited at N14 – N17 (Middle Miocene – Late Miocene) in the bathyal environment. The topmost layer is the biozonation of Orbulina universa – Globigerinoides immaturus which was deposited at N17 –N23 or Pliocene – Holocene in the bathyal environment. In the top two layers, there are fossil fragments that come from older rock layers (Early Tertiary).
EVALUASI POTENSI LIKUIFAKSI DI WILAYAH CEKUNGAN BANDUNG BERDASARKAN METODE ANALISIS MULTI-SENSOR GELOMBANG PERMUKAAN
Full text linkSecara geologi, wilayah Cekungan Bandung tersusun oleh endapan danau Bandung purba yang terdiri atas lapisan lempung dengan sisipan lapisan pasir sehingga rentan terhadap likuifaksi akibat gempa bumi. Metode analisis multi-sensor gelombang permukaan (MASW) adalah salah satu metode geofisika yang menghasilkan model satu dimensi kecepatan gelombang geser (Vs) terhadap kedalaman. Makalah ini menyajikan hasil analisis potensi likuifaksi menggunakan data profil Vs di 5 lokasi yang tersebar di wilayah Cekungan Bandung. Data Vs diperoleh dengan menggunakan 24 geophone yang tersebar dengan spasi 4 meter di setiap lokasi penelitian. Hasil analisis data menggunakan metode MASW menghasilkan profil Vs dan Vs30 di setiap lokasi yang menunjukkan bahwa lapisan tanah di wilayah Cekungan Bandung dapat diklasifikasi dalam kelas situs E dan D. Sedangkan berdasarkan hasil analisis potensi likuifaksi menggunakan profil Vs, dengan mempertimbangkan percepatan tanah puncak yang dihasilkan oleh Sesar Lembang (Mw 6,5), mengindikasikan bahwa lapisan pasir di dalam endapan danau purba mempunyai potensi likuifaksi pada kedalaman dan ketebalan yang bervariasi. Lapisan pasir dengan nilai Vs < 175 m/detik yang menyebabkan potensi likuifaksi di daerah Bojongemas lebih tinggi dibandingkan dengan daerah lainnya. Hasil penelitian ini menunjukkan kesesuaian dengan hasil analisis likuifaksi berdasarkan metode uji penetrasi standar dari hasil penelitian terdahulu. ABSTRACT - The Evaluation of Liquefaction Potential in Bandung Basin Area Based on Multi-sensor Analysis of Surface Wave. The Bandung Basin region is composed of ancient Bandung lake sediment deposits consisting of thick clay layers intercalated with sand layers, which is vulnerable to liquefaction due to earthquakes. The multi-sensor surface wave (MASW) analysis method is a geophysical method that produces a one-dimensional model of shear wave velocity (Vs) against depth. . This paper presents the results of an analysis of the potential for liquefaction using Vs profile data at 5 locations spread across the Bandung Basin. using 24 geophones with 4-m spacing. The results of data analysis using the MASW method produce Vs and Vs30 profiles at each location which indicate that the soil layers in the Bandung Basin area can be classified into E and D site classes. Meanwhile, based on the results of the analysis of potential liquefaction using the Vs profile, taking into account the peak soil acceleration produced by the Lembang Fault (Mw 6.5), indicates that the sand layer in ancient lake sediment deposits has the potential for liquefaction at varying depths and thicknesses. Sand layer with a value of Vs <175 m / sec which causes the potential for liquefaction in the Bojongemas area is higher than in the other areas. The results of this study confirm liquefaction analysis based on the standard penetration test method from the previous stud
INVERSI GEOSTATISTIK MENGGUNAKAN ANALISA MULTI-ATRIBUT STEPWISE REGRESSION UNTUK KARAKTERISASI RESERVOIR
Full text linkEksplorasi dan produksi pada reservoir tight sand sampai saat ini masih memiliki tantangan tersendiri karena karakterisitik porositas dan permeabilitas yang rendah. Penelitian ini dilakukan untuk menganalisis karakteristik reservoir tight sand berdasarkan peta persebaran properti log menggunakan inversi impedansi akustik (IA) dan analisis multi-atribut. Analisis multi-atribut stepwise regression adalah suatu metode yang menggunakan atribut-atribut yang paling baik untuk memprediksi log target dengan melalui proses trial and error. Pemilihan atribut seismik yang tepat dapat memberikan penggambaran zona target yang lebih baik. Penelitian ini dilakukan untuk memperoleh peta struktur geologi bawah permukaan, volume impedansi akustik. Kemudian dilakukan analisis multi-atribut untuk mendapatkan prediksi volume property log yang mencakup pseudo gamma-ray, densitas, dan porositas dengan menggunakan metode stepwise regression. Hasil inversi seismik IA dan analisis multi-atribut stepwise regression menunjukkan reservoir dengan fluida berupa gas, serta litologi tight sand yang memiliki rentang nilai IA sebesar 22.000 ((ft/s)*(g/cc)) sampai dengan 45.000 ((ft/s)*(g/cc)), densitas 2,25 g/cc sampai dengan 2,6 g/cc, dan porositas 5% sampai 12%. Peta densitas dan porositas yang diperoleh dari analisa multi-atribut menunjang tahap eksplorasi dan produksi jangka panjang. Hal tersebut terkait upaya untuk meningkatkan pemahaman tentang perangkap stratigrafi, dan kemenerusan lapisan reservoir. ABSTRACT – Geostatistical Inversion Using Multi-attribute Stepwise Regression for Reservoir Characterization. Exploration and production of tight sand reservoirs are still challenging due to their low porosity and permeability characteristics. This study used acoustic impedance inversion and multi-attribute analysis to analyze the tight sand reservoir characteristics based on the log property distribution map. Stepwise regression multi-attribute analysis is a method that uses the best attributes to predict the target log, which is carried out through a trial and error process. The ability to select a correct seismic attribution can provide a better depiction of the target zone. This research was conducted to obtain a subsurface geological structures map, acoustic impedance volumes. The multi-attribute analysis was performed to predict volume log properties such as pseudo-gamma-ray, density, and porosity, by using the stepwise regression method. The results of acoustic impedance seismic inversion and stepwise regression multi-attribute analysis show that the reservoir contains gas fluid with tight sand lithology, which has a range of acoustic impedance values of 22,000 ((ft/s)*(g/cc)) to 45,000 ((ft/s)*(g/cc)), the density of 2.25 g/cc to 2.6 g/cc, and porosity of 5% to 12%. The density and porosity maps obtained from the multi-attribute analysis can support the long-term exploration and production stages. The aims are to improve the primary recovery and tertiary recovery, understanding the stratigraphic traps, and the continuity of reservoir layers
SEISMIC HAZARD MICROZONATION BASED ON PROBABILITY SEISMIC HAZARD ANALYSIS IN BANDUNG BASIN
Full text linkThe geological and seismic-tectonic setting in the Bandung Basin area proliferates the seismicity risk. Thus, it is necessary to investigate the seismic hazards caused by the foremost seismic source that affects the ground motions in the bedrock. This research employed Probability Seismic Hazard Analysis (PSHA) method to determine the peak ground acceleration value. It considers the source of the earthquakes in the radius of 500 km with a return period of 2500 years. The analysis results showed that the Peak Ground Acceleration (PGA) in this region varies from 0.46 g to 0.70 g. It correlates with the magnitude and hypocentre of the dominant earthquake source of the study locations. The PGA value on the bedrock was used as an input to develop the seismic hazard microzonation map. It was composed using the Geographic Information System (GIS) to visualise the result. This research provides a scientific foundation for constructing residential buildings and infrastructure, particularly as earthquake loads in the building structure design calculations. ABSTRACT - Mikrozonasi Bahaya Seismik Berdasarkan Probability Seismic Hazard Analysis di Cekungan Bandung. Kondisi geologi dan seismik-tektonik di Cekungan Bandung meningkatkan risiko kegempaan di wilayah tersebut. Oleh karena itu, perlu dilakukan penelitian tentang bahaya seismik yang disebabkan oleh sumber-sumber gempa di sekitarnya yang mempengaruhi gelombang gempa di batuan dasar. Penelitian ini menggunakan metode Probability Seismic Hazard Analysis (PSHA) untuk menentukan nilai percepatan gelombang gempa di batuan dasar. Lebih lanjut penelitian ini menggunakan sumber gempa dalam radius 500 km dengan periode perulangan 2500 tahun. Hasil analisis menunjukkan bahwa Peak Ground Acceleration (PGA) di wilayah ini bervariasi dari 0,46 g hingga 0,70 g. Hal ini berkorelasi dengan magnitudo dan jarak hiposenter sumber gempa dominan terhadap lokasi penelitian. Nilai PGA di batuan dasar digunakan sebagai input data dalam pembuatan peta mikrozonasi bahaya seismik. Peta mikrozonasi bahaya seismik disusun dan divisualisasikan menggunakan Sistem Informasi Geografis (SIG). Luaran penelitian ini menghasilkan landasan ilmiah pada konstruksi bangunan tempat tinggal dan infrastruktur, khususnya sebagai pembebanan gempa dalam perhitungan desain struktur bangunan
PELINDIAN BIJIH NIKEL LATERIT KADAR RENDAH MENGGUNAKAN METODE ATMOSPHERIC ACID LEACHING DALAM MEDIA ASAM KLORIDA (HCL)
Full text linkEkstraksi nikel laterit menggunakan metode hidrometalurgi lebih efisien dari segi konsumsi energi dengan lebih sedikit gas buang dibandingkan dengan metode pirometalurgi. Hal ini menyebabkan nikel laterit berkadar rendah dapat diekstraksi lebih banyak menggunakan metode hidrometalurgi. Salah satu metode hidrometalurgi dalam mengekstraksi nikel dari bijih nikel laterit adalah Atmospheric Acid Leaching. Penelitian ini bertujuan untuk memperoleh data persentase perolehan nikel, menentukan variabel yang paling berpengaruh dan menentukan kondisi optimum dalam proses pelindian. Pada penelitian ini dilakukan variasi pada faktor-faktor yang berpengaruh dalam proses leaching yakni temperatur, konsentrasi asam dan waktu pelindian. Analisis kandungan nikel hasil pelindian dilakukan menggunakan Atomic Adsorbtion Spectroscopy (AAS). Hasil penelitian menunjukkan bahwa persentase perolehan nikel terendah adalah 9,40% Ni dan tertinggi 75,76% Ni. Perhitungan ANOVA digunakan untuk menentukan faktor paling berpengaruh pada proses pelindian nikel laterit. Faktor yang paling berpengaruh dalam penelitian ini adalah temperatur (B), diikuti konsentrasi asam (A), waktu pelindian (C), interaksi konsentrasi-temperatur (AB), interaksi temperatur-waktu (BC), interaksi konsentrasi-waktu (AC) dan interaksi konsentrasi-temperatur-waktu (ABC). Kondisi optimum pelindian diperoleh pada kondisi temperatur 75°C, konsentrasi asam 2,9-3 Molar dalam waktu 69-70 menit dengan perolehan nikel >70%. ABSTRACT - Leaching of Low-Grade Nickel Laterite Ore Using Atmospheric Acid Leaching Method in Hydrochloric Acid. Nickel laterite extraction using the hydrometallurgical method is more efficient in energy consumption with less exhaust gas than the pyrometallurgical method. This method causes the extraction of low-grade nickel laterite ore using hydrometallurgy could be more effective. One of the hydrometallurgical methods to extract nickel from its ore is atmospheric acid leaching. This research aims to determine the percentage of nickel recovery through the leaching process, determine the most influenced leaching factor, and determine the optimum leaching condition. The main factors that influence the leaching process are temperature, acid concentration, and leaching time. Atomic adsorption spectroscopy was chosen to analyze the leaching solution. This research showed that the lowest recovery of nickel leaching was 9,40% of Ni, and the highest was 75,76% of Ni. Analysis of variance (ANOVA) was used to determine the most influenced factor of leaching. The most influenced factor was the temperature (B), followed by acid concentration (A), duration (C), the interaction of acid concentration-temperature (AB), the interaction of temperature-duration (BC), the interaction of acid concentration-duration (AC), and interaction of acid concentration-temperature-duration (ABC). The optimum leaching condition is at 75°C of temperature, 2,9-3 molar of acid concentration, in 69-70 minutes of duration, which has >70% of Ni recovery
GEOLOGI DAN PETROKIMIA ENDAPAN ZEOLIT DAERAH BAYAH DAN SUKABUMI
Full text linkZeolit dijumpai pada batuan piroklastik di daerah Cikembar (Sukabumi) dan Bayah (Banten) dari zona fisiografi pegunungan Bogor dan Bayah. Karakteristik, genesa batuan, dan tipe zeolit di kedua lokasi tersebut belum dijelaskan, terutama kaitannya dengan potensi pengkayaan unsur tanah jarang (UTJ) pada batupasir tufan di daerah Cikembar dan tuf teralterasi di daerah Swakan. Metode yang digunakan pada studi ini terdiri dari pengamatan geologi lapangan, petrografi, difraksi sinar-X (XRD), dan kimia batuan (whole rock) menggunakan XRF dan ICP-MS. Tujuannya adalah untuk mengungkap genesa pembentukkan zeolit dan UTJ di Swakan dan Cikembar. Batupasir tufan dari Cikembar dan tuf dari Swakan menunjukkan kehadiran zeolit bertipe mordenit dan klinoptilolit. Zeolit di daerah Cikembar terdapat sejajar perlapisan, sedangkan di daerah Swakan berasosiasi dengan kumpulan mineral alterasi. Pengendapan zeolit Cikembar dipengaruhi oleh air meteorik yang dicirikan oleh anomali negatif Ce pada pola diagram laba-laba yang di normalisasi terhadap kondrit. Total (∑UTJ) pada batupasir tufan dari Cikembar 82– 94 ppm dan pada tuf Swakan 71–83 ppm. Perbedaan kandungan ∑UTJ tersebut lebih mencerminkan komposisi UTJ pada batuan asal.ABSTRACT – Geology and petrochemistry of zeolite deposits of Bayah and Sukabumi areas. Zeolites are found in pyroclastic rocks in Cikembar (Sukabumi) and Bayah (Banten) from the Bogor and Bayah mountainous physiographic zones. The characteristics, rock genesis, and types of zeolites from these two locations have not been explained, especially in relation to the potential of REEs (Rare Earth Elements) enrichment in Cikembar tuffaceous sandstone and Swakan altered tuff. The method used in this study consists of field geological observations, petrography, X-ray diffraction (XRD), and whole rock geochemistry using XRF and ICP-MS. The aim is to uncover the formation of zeolites and REEs in Swakan and Cikembar. The Cikembar tuffaceous sandstones and the Swakan tuffs show the presence of mordenite and clinoptilolite types of zeolites minerals. The zeolites in Cikembar area are parallel to the bedding plane, while in Swakan area are associated with alteration mineral assemblages. The deposition of Cikembar zeolite was influenced by meteoric water which is characterized by the negative Ce anomalies in chondrite-normalized spider diagram pattern. The total (∑REEs) concentration in Cikembar tuffaceous sandstones are 82–94 ppm and Swakan tuffs are 71–83 ppm. The difference in the ∑REE content more likely reflects the parent’s rock REEs composition