RISET Geologi dan Pertambangan
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Comparing Numerical Methods for Infiltration Estimation: A Statistical Approach to Accuracy and Efficiency
Full text linkThis study evaluates four numerical methods—Euler, Heun, Runge-Kutta 4th order (RK4), and Adams-Bashforth—in terms of their accuracy and computational efficiency for solving the Horton infiltration model, which is crucial for hydrological studies. The methods were applied to simulate soil infiltration and cumulative recharge, with a focus on determining the most suitable method for practical applications in water resource management, agriculture, and soil conservation. An ANOVA (Analysis of Variance) test was conducted to assess the statistical significance of differences in the results obtained from the methods. The test revealed no significant differences between the methods (p-value = 0.9995), indicating that despite differences in computational complexity and accuracy, the methods produced similar results. The Euler method, being the simplest and fastest, provided acceptable results for shorter simulations or less critical applications, while RK4 and Heun, though more computationally expensive, yielded more accurate estimates. Adams-Bashforth offered a reasonable balance between accuracy and efficiency. This study highlights the importance of selecting the appropriate numerical method based on both accuracy and computational cost, particularly for real-time applications and large-scale simulations in hydrology. The findings suggest that simpler methods like Euler can be used for less critical tasks, while more accurate methods like RK4 should be employed for high-precision modeling in complex hydrological scenarios
Tectonic Geomorphology Analysis in Natural Hydrogen Exploration: A Case Study from Tanjung Api, Sulawesi
Full text linkNatural hydrogen exploration has been proven to be a challenging endeavor due to many factors. In this paper we present a new insight to hydrogen exploration by using tectonic geomorphology to identify key target area based on its tectonic activity in relation to the occurrence of active fault. Tectonic geomorphology analysis is performed using 3 morphometric indices such as mountain front sinuosity, basin shape index and drainage density to determine the index of relative tectonic activity in this region. Field observation shows that hydrogen seeps occurred in the area with high to very high tectonic activity (Class 1 – 2) that correlate with the present of active faults in this area. Tectonic geomorphology can be used to narrow down the potential area by identify active tectonic region which corelated to active faults in this area
Petroleum System Risk Quantification for PSC Investment in Indonesia’s LNG Sector
Full text linkInvestment decisions in upstream oil and gas sector of Indonesia often involve acquiring stakes in existing Production Sharing Contract (PSC) areas. Such decisions require careful assessment of geological uncertainty, economic viability, and regulatory constraints. For investors evaluating PSC blocks, a robust understanding of regional geological risk within the petroleum system is critical. This study introduces a practical and scalable geological risk quantification framework to support upstream investment decisions in the LNG sector in Indonesia. The framework is designed for application under the current fiscal regime and can be effectively implemented even when data availability is limited, such as when relying on information from the Migas Data Repository (MDR). Recognizing that early-stage opportunities often involve significant geological uncertainty, we developed a tailored petroleum system risk metric comprising five parameters: source rock, trap, dynamic factors, reservoir conditions, and subsurface issues. The framework was applied to five PSC blocks using Multi-Attribute Utility Theory (MAUT), integrating operator-specific economic indicators (Net Present Value, Internal Rate of Return, Payout Time, and Profitability Index) alongside CO₂ emission intensity. Monte Carlo simulations were conducted to evaluate investment rankings under uncertainty. A key finding is that the proposed risk quantification approach is simple enough to be implemented with limited MDR data, yet robust enough to support investment strategy. Furthermore, the framework builds upon and complements existing standardization efforts by the regulator, SKK Migas, offering a practical tool for upstream investors in an evolving regulatory landscape
Microzonation of Soil Resistance Based on Shear Wave Velocity Variation: Case Study of Kampung Melayu District, Bengkulu City
Full text linkThis research presents a unique microzonation map based on shear wave variations, specifically Vs10, Vs20, Vs30, Vs40, and Vs50. Microzonation is dividing a region into smaller zones based on specific characteristics, such as soil resistance to seismic waves. The method used in this research includes secondary data collection of shear wave velocity values and soil layers in the District of Kampung Melayu, then producing shear wave velocity distribution at various depths, soil site class distribution map, and Ground Amplification Factor (GAF) distribution map. The results of this study indicate that the variation in shear wave velocity at different depths provides an overview of the soil type resistance in Kampung Melayu District, Bengkulu City. The resulting microzonation map, a novel approach in this context, indicates an increase in the Vs value with increasing depth. Additionally, the Ground Amplification Factor (GAF) distribution reveals that areas with low soilspecific resistance exhibit higher amplification values, thereby increasing their susceptibility to seismic vibrations. These findings provide valuable and novel information for earthquake risk mitigation and the planning of safer infrastructure in this area, significantly contributing to civil engineering and urban planning
Study of Subsurface Structures for the Sungai Lilin, Coal Prospect Area, South Sumatra using Active Seismic Multichannel Analysis of Surface Waves
Full text linkIndonesia’s dependency on coal, which powered ~47% of its electricity in 2018, highlights the need to optimize exploration amid rising energy demands and volatile fuel prices. This study aims to characterize subsurface structures in the Sungai Lilin coal prospect area, South Sumatra, within the coal-bearing Muara Enim Formation employing the Multichannel Analysis of Surface Waves (MASW) method. We carried out field seismic data collection using a PASI 16S24-P seismograph equipped with 24 geophones, spacing of 4 m. After having dispersion processes, which result in phase velocities (or group velocity) against frequency, we inverted phase velocities to extract subsurface structures through shear wave velocity (Vs) and density. By analyzing Vs variations, we mapped coal deposits at depths of 5–40 m with Vs values of 250–450 m/s, alongside soil, sand, claystone, and siltstone layers. Our subsurface structures derived MASW approach, integrated with borehole data, provided high-resolution 2-D models of young, shallow coal seams varying in thickness and depth. These findings highlight MASW’s efficacy for cost-effective, non-invasive coal exploration, offering insights into resource delineation that support energy security for Indonesia and sustainable coal exploration in similar geological settings
Earthquake Hazard Evaluation Study on the Central Area of Selebar District, Bengkulu City, based on Seismic Response Analysis
Full text linkThe Selebar District, a developing area in Bengkulu City, has been the site of at least two significant earthquakes with a magnitude of Mw 7.0 in the past two decades. This study, which presents a seismic hazard assessment for the central area of the Selebar District, is of paramount importance. The study commences with field investigations at three strategically chosen points in the central area of Selebar District, Bengkulu City, including the airport, educational center, and toll road. The analysis, which involves the propagation of seismic waves, aims to comprehend the seismic behavior during an earthquake. The potential impact of seismic waves on structures and the environment is a serious concern. Seismic response analyses, a critical component of this study, were constructed based on a one-dimensional wave propagation model using a non-linear method. These analyses offer valuable insights into the potential impact of seismic waves on structures and the environment, a matter of serious concern. The results of the field investigations were also examined for seismic response analysis. The PGA, spectral response acceleration, and amplification factors are presented in this study and analyzed to determine the seismic hazard. Based on the PGA values, two earthquake sources can cause very high damage to buildings, and one earthquake source has a high potential. The generated spectral acceleration has exceeded the design spectral acceleration, especially at short periods. Therefore, using local spectra in building structure design can be a recommendation for local engineers to consider the impact of earthquakes on the central area of Selebar District, Bengkulu City
Geochemical characteristic of volcanic rocks in the Karaha – Talagabodas fields related to Galunggung Volcano
No full textThe Karaha-Talagabodas field is located on the east side of the ancient Bandung-Garut caldera and adjacent to the Galunggung volcano in West Java, Indonesia. Karaha-Talagabodas are two distinct locations separated by approximately 10 km. Geochemical analysis including major, trace and rare earth elements has been done using Fusion ICP-MS to find out how the different composition of volcanic rocks in the two regions (Karaha and Talagabodas). The volcanic rocks of the Karaha-Talagabodas field were composed of pyroxene andesite, andesite basaltic, basalt, highly altered pyroclastic and tuff breccia. The identified alteration minerals are indicated by the presence of kaolinite, halloysite, silica, sericite and chlorite. Geochemically, these volcanic rocks contain SiO2 variable (49.94%-62.27%), Na2O (3.02%-3.83%) and K2O (0.46%-1.78%). Based on the major element diagram of rock chemistry (Na2O+K2O vs SiO2). It shows rocks consisting of calc-alkaline for andesite from Karaha basalt, basaltic andesite and andesite formed in tholeiitic environments on Talagabodas volcanic rocks. Trace element data for host volcanic rocks are provided by this study to identify the magmatic arc system and distribution of subduction components. The normalized REE diagram of N-Morb shows the similarity of the pattern of all Talagabodas volcanic rocks, only Karaha andesite rocks show slight REE enrichment and europium depletion
A SYSTEMATIC REVIEW OF GEOLOGICAL RESOURCE CONTAINING NICKEL : RESOURCE, DISTRIBUTION, MINING, EXTRACTION AND ADVANCED MATERIAL SYNTHESIS
Full text linkNickel ore is the main source of nickel, an important metal used in many modern materials. This paper gives a brief overview of different aspects of nickel ore, such as its history, types, distribution, demand, and the technology used for mining and processing it. The two main types of nickel ore are nickel sulfide ore and laterite ore. Indonesia has significant nickel ore deposits, primarily in the form of laterite, due to its tropical climate with high temperatures and rainfall. Nickel is essential for making various important materials like stainless steel, special alloys, plating, and batteries. Laterite also contains other valuable elements like iron, magnesium, silicon, and oxygen, found in compounds such as goethite, nickel oxide, magnesium silicate, and quartz. Laterite ore can be processed to produce nickel matte, ferronickel, and nickel pig iron. The paper also discusses advanced materials made from laterite ore, including photocatalysts and batteries. Mining and processing activities have both positive and negative effects on local communities. To minimize negative impacts, it is important to consider the satisfaction of both the local community and the government in the initial planning of mining and processing projects
DENSITY DISTRIBUTION OF SHEAR WAVE VELOCITY, CONE RESISTANCE AND CORRECTED SPT IN THE DOMINANT SOILS OF BENGKULU CITY, INDONESIA
Full text linkThis research is of significant importance as it discusses the modelling of a two-dimensional map of soil parameters in Bengkulu City, Bengkulu Province, Indonesia. The two-dimensional modelling was conducted to show the distribution of soil parameter values based on the research points strategically distributed throughout Bengkulu City. These research points were chosen to represent the diverse soil conditions in the city, making the modelled soil parameters particularly helpful for engineers and construction consultants when planning construction in the study area. The parameters to be discussed include shear wave velocity, cone resistance, and corrected standard penetration test. This modelling applies Inverse Distance Weighting as an interpolation method from 215 research points. Inverse Distance Weighting is used because it supports knowing the value of soil parameters around the review point, especially in two-dimensional modelling. The results showed that the distribution of the highest value of shear wave velocity of the clay layer is dominated in the Teluk Segara sub-district. The distribution of the highest value of cone resistance of the clay layer is dominant in the Kampung Melayu Sub-district. The distribution of the highest value of corrected standard penetration test of the clay layer is also dominated in Kampung Melayu Sub-district
LANDSLIDE SUSCEPTIBILITY ZONATION USING WEIGHT OF EVIDENCE METHOD IN MERTELU AND TEGALREJO, GEDANGSARI, GUNUNGKIDUL, SPECIAL REGION OF YOGYAKARTA, INDONESIA
Full text linkMertelu and Tegalrejo are situated in the Gedangsari Subdistrict, Gunungkidul Regency, Special Region of Yogyakarta, Indonesia. Located in the northern Baturagung Range, Southern Mountains Zone of East Java, with much hilly topography and mountainous areas with steep slopes, Mertelu and Tegalrejo are prone to landslides. The purpose of this research is to produce a landslide susceptibility zone using the weight of evidence (WoE) method. There were 73 landslide data taken from December 2022 to January 2023. As much as 80% of the data were used as a training dataset for weighting and generating the model map, while the remaining 20% were used as a test dataset. Parameters used in this research include slope angle, lithology, distance to faults, distance to rivers, and land use. Each parameter was weighted using the WoE method, and then the map of each parameter was overlaid to produce a map of landslide susceptibility zones. The accuracy of the map was calculated using the area under curve (AUC) method, including the success rate curve (SRC) and prediction rate curve (PRC). Based on the research results, the landslide susceptibility zone in the research area can be categorized: (1) very low, covering 6.34% of the total research area, (2) low, covering 24.15% of the total research area, (3) moderate, covering 44.46% of the total research area, and (4) high, covering 25.05% of the total research area. The landslide susceptibility map shows that the research location is predominantly characterized by areas with medium to high susceptibility to landslides. The medium and high susceptibility zones are close to the rivers that serve as the alignment of the faults. The accuracy calculations result in an SRC value of 0.753 and a PRC value of 0.780, both can be classified as “good” performance