Reservoir characterization is a critical component of hydrocarbon exploration and development. Seismic wave attenuation, which is closely linked to the physical properties of rocks, has emerged as an effective tool for this purpose. The Scaled Qp and Qs (SQp and SQs) methods represent advanced attenuation-based technique capable of discriminating lithology and fluid content through analysis of P-wave and S-wave attenuation. This study applies SQp and SQs attributes to characterize lithology and fluid distribution within the Plover Formation of the Poseidon Field, using 3D partial angle stack seismic data and well logs from three wells: Kronos-1, Poseidon-1, and Poseidon-2. Crossplot analysis indicate that low SQp values (0.02–0.2) are associated with sandstone, whereas higher SQp values (0.2–0.7) correspond to shale. In terms of fluid discrimination, high SQs values (0.55–0.7) identify gas-bearing zones, while lower SQs values (0.4–0.55) indicate brine-saturated interval. SQp and SQs volumes derived from simultaneous inversion reveal that gas-saturated sandstone reservoirs — characterized by low SQp and high SQs — are distributed along a southwest to northeast trend, consistent with the location of all three wells. These results demonstrate that SQp and SQs attributes effectively distinguish reservoir from non-reservoir lithology and delineate hydrocarbon-bearing zones, providing a reliable attenuation-based workflow for reservoir characterization in similar geological settings.
This study investigates the volumetric calculation of hydrocarbon reserves in tight sandstone reservoirs by integrating pre-stack seismic inversion and static modeling. The research focuses on the Penobscot Field in the Scotian Basin, Nova Scotia, Canada, specifically the Middle Mississauga Formation, which contains tight sandstone. The study aims to estimate hydrocarbon reserves in tight sandstone, which has distinct characteristics compared to typical sandstone. The static modeling approach integrates seismic and well data to construct a structural model, allowing the spatial estimation of volume shale (), effective porosity (), water saturation (), and net to gross (NTG). Pre-stack seismic inversion is applied to generate detailed subsurface models, utilizing seismic data before the stacking process for more comprehensive information. By using data from various angles of incidence, this method improves resolution and enhances the ability to detect complex subsurface layers, producing a model with physical rock parameters like density and P-wave velocity. The study uses pre-stack seismic inversion to obtain an acoustic impedance profile, which is then applied in facies and petrophysical property simulation using geostatistical methods SGS and SIS to align simulation trends with inversion results. This integration is expected to produce a reliable model for hydrocarbon reserve volume calculation. Results indicate that the tight sandstone zones contain hydrocarbon reserves, primarily gas, due to the low porosity of the sandstone and the lower viscosity of gas compared to oil, enabling gas to move more easily into narrow pores. The simulated effective porosity, ranges from 0.01 to 0.18, volume shale from 0.01 to 1, water saturation from 0.64 to 1, and net to gross (NTG) values from 0.7 to 1.00, resulting in a GIIP volume of 4494 sm³. These findings demonstrate that integrating these methods effectively calculates hydrocarbon reserves in tight sandstone.
Tehoru Village, Tehoru District, Central Maluku Regency, has significant geothermal potential. This study aims to examine Bouguer anomalies, reduced-Bouguer density, sediment thickness estimation, and shallow structures using TOPEX gravity data and SRTM DEM in an area of ±191.70 km². The processing results show Complete Bouguer Anomaly (CBA) values ranging from 6.80 to 73.60 mGal, with Bouguer densities of 1.77 to 1.79 g/cm³, indicating the dominance of alluvial sediments. Anomaly separation using the Moving Average method yields residual anomalies ranging from -4.60 to 47.70 mGal, with low anomalies dominant in the southwest of the geothermal manifestation. Spectral analysis shows an average sediment thickness of ±246.07 m. In contrast, SVD analysis, lineament maps, and rose diagrams indicate that geothermal manifestations develop in tight fault-related zones with a dominant northeast–southwest orientation. Although effective for regional analysis, TOPEX gravity data interpretation has limitations for imaging shallow structures and sediment thickness variations, as small anomalies are often obscured by its relatively low spatial resolution. Overall, the Tehoru geothermal system is controlled by several local fault-related zones and significant sediment thickness, which influence its response to tectonic activity.
The coastal area of Teluk Sepang, Bengkulu City, Sumatra, Indonesia, is dominated by young alluvial and marine sediments that are highly susceptible to seismic wave amplification due to tectonic activity along the Indo-Australian–Eurasian subduction zone. This research aims to characterize local seismic response and map soil dynamic properties using microtremor data analyzed with the Horizontal to Vertical Spectral Ratio (HVSR) method. Microtremor measurements were conducted at several observation points with a sampling interval of 5 ms capable of and a recording duration of 30 minutes at each site. The recorded data were processed using the HVSR method through windowing, Fourier transform, and spectral ratio analysis to obtain the dominant frequency (f₀), amplification factor (A₀), and seismic vulnerability index (Kg). The results show that low f₀ values are associated with thick soft sediments, while high A₀ values indicate stronger amplification potential. High Kg values are identified in areas where low f₀ coincides with high A₀, reflecting greater seismic vulnerability. These results reveal significant spatial variability in local seismic response across the study area. This study provides new site-specific insights into seismic vulnerability in coastal environments and contributes to improving seismic hazard assessment and coastal development planning in Bengkulu City.
Accuracy in identifying the distribution zone of iron ore mineral resources in the Pelaihari area, Tanah Laut Regency, is very important for exploration activities. This study aims to identify the presence of iron ore using magnetic data based on Analytical Signal maps from residual processing and modeling 2D subsurface results to see iron ore mineralization zones. The magnetic method used in this study is a geophysical exploration technique based on measurements of variations in magnetic anomaly intensity in rocks caused by the Earth's magnetic field. Magnetic data underwent magnetic correction, daily correction, and correction according to the International Geomagnetic Reference Field (IGRF) standard to determine the Total Magnetic Intensity (TMI). Based on the results of the study, iron ore mineralization zones were identified at a depth of approximately 10–40 m from the surface with a high susceptibility value of around 0.2 SI. The high residual anomaly response and Analytic Signal values between 23.4–36.0 nT/m indicate a shallow magnetic source localized by ultramafic rocks as the bedrock with a susceptibility value of approximately 0.097 SI at a depth of up to ±150 m, forming a prominent upward bulge. These characteristics indicate significant potential for laterite mineralization.
This study applies a machine learning approach to classify lithology using well log data from 14 wells in Ford County, Kansas, United States, to address the limitations of conventional interpretation, which is time-consuming and subjective due to overlapping log responses. Reference lithology labels were generated using predefined well-log interpretation criteria and grouped into four classes: sandstone, limestone, shale/clay, and coal. Two supervised learning algorithms, K-Nearest Neighbors (KNN) and Artificial Neural Networks (ANN), were evaluated and compared. The preprocessing stages included data cleaning by removing null values and inconsistencies, Z-score normalization, class balancing using SMOTE on the training data to prevent data leakage, and feature selection based on Pearson correlation. Model performance was evaluated using Classification Accuracy (CA), Area Under the Curve (AUC), Logarithmic Loss (Log Loss), and 5-fold cross-validation. The results indicate that ANN consistently outperformed KNN in lithology classification. ANN achieved classification accuracies above 95%, AUC values approaching 1.00, and low Log Loss, whereas KNN achieved testing accuracies of approximately 75-80% but exhibited lower cross-validation performance, indicating reduced robustness in intervals characterized by overlapping lithological responses. The optimal ANN architecture consisted of three hidden layers with 100-100-100 neurons and 100 training iterations. Visual evaluation of four test wells showed good agreement between the predicted and reference lithology distributions. These findings suggest that machine learning, combined with appropriate preprocessing techniques, can support lithology classification from well log data. Among the evaluated models, ANN demonstrated superior capability in capturing nonlinear relationships between well log responses and lithological variations within the study area.
The Indo-Pacific Warm Pool significantly influences global atmospheric circulation, with tropical rainfall patterns highly sensitive to glacial–interglacial climate changes. During the Last Glacial Maximum (LGM), approximately 26,500 years before present, lower insolation, expanded ice sheets, and reduced sea levels weakened the Australian–Indonesian Monsoon (AIM) due to a southward shift of the Intertropical Convergence Zone (ITCZ). In contrast, the Holocene period experienced intensified monsoon systems and increased precipitation. However, high-resolution hydroclimate reconstructions from the western Savu Strait remain scarce. This study reconstructs rainfall variability from the LGM to the Holocene using geochemical proxies from sediment core ST10 (at 1 cm interval), located in the western Savu Strait. Three elemental ratios (Ti/Ca, K/Ca, and Rb/Sr) from X-ray fluorescence (XRF) core scanning were used to indicate terrigenous input, chemical weathering, and fluvial discharge. The age model was established using radiocarbon dating and stable isotope alignment with the Greenland ice core δ¹⁸O record. Log-transformed elemental ratios reveal four intervals of increased rainfall: the LGM, Heinrich Event 1 (HE1), Younger Dryas to Early Holocene, and the Late Holocene. These periods are characterized by elevated Ti/Ca, K/Ca, and Rb/Sr values, suggesting enhanced monsoonal rainfall and continental runoff. Conversely, lower proxy values during the Early Deglaciation, Bølling–Allerød, and Mid-Holocene indicate drier climatic conditions. These patterns align with regional proxy records from southwest Sumba and the Timor Sea, confirming the reliability of elemental ratios in reconstructing past hydroclimate variability. This study provides the first continuous record of rainfall shifts in the western Savu Strait from the LGM to Holocene and contributes to understanding long-term monsoon dynamics in southeastern Indonesia, highlighting the complex response of tropical hydroclimate to global climate forcing.
The Sangon area is located in Kulonprogo Regency, which physiographically has landforms in the form of hills and mountains. Steep slope angles of the hills and weathered surface rock conditions increase the potential for landslides hazard in the Sangon area. This study aims to identify unstable layers that are prone to landslides in the Sangon, Kokap, and Kulonprogo areas. Information regarding the potential characteristics of landslides can significantly impact reducing losses caused by landslides hazard. Conceptual modelling of weathered layers that have the potential to trigger landslides has been carried out in the research area using resistivity distribution data of subsurface rocks using the geoelectrical method. Geoelectrical data from five measurement lines with a length of 290 m each line with a southeast-northwest orientation can delineate an image of the distribution of weathered layers in the subsurface. Based on the results of two-dimensional (2D) subsurface resistivity inversion modelling, it is known that the weathered layer as soil form andesite rock has a low resistivity value with a range of 7 m – 246 m with a depth of 0 - 12 meters in the subsurface. The distribution of resistivity value of the weathered layer is depicted in the 3D model to determine the distribution of the weathered layer, which is then made into a conceptual model that can describe the characteristics of landslides. The description of the 3D resistivity model of subsurface rocks produces a conceptual model of landslides in the research area, where the potential for landslides that may occur has characteristics in the form of debris flow or translational. The unstable layer volume was 947,000 m³, with a slope gradient ranging from 19% to 35%, with a moderate to steep slope.
Mount Slamet, located in Central Java, Indonesia, is one of the promising geothermal prospect areas due to its active volcanic system and distinct surface manifestations such as hot springs and altered grounds. This study aims to identify potential geothermal zones around Mount Slamet by integrating geochemical analysis and remote sensing data. Geochemical measurements from hot springs show temperatures ranging from 48–89 °C, pH values between 6.2–7.1, and elevated concentrations of SiO₂ (90–145 mg/L) and Cl⁻ (18–42 mg/L), indicating high-temperature fluid interaction. Remote sensing techniques, including thermal anomaly detection and alteration mineral mapping using multispectral and hyperspectral satellite imagery, were employed to delineate surface manifestations and hydrothermal alteration zones. The results indicate that the most prospective geothermal area is located in the southwestern part of Mount Slamet, characterized by strong thermal anomalies and geochemical signatures consistent with a high-enthalpy geothermal system. The integration of these methods provides a comprehensive assessment of geothermal potential, revealing key prospect areas with significant thermal anomalies and geochemical signatures indicative of a high-enthalpy geothermal system. These findings enhance understanding of Mount Slamet’s geothermal potential and offer valuable.
Building damage caused by earthquakes is more prevalent in the sedimentary areas of Yogyakarta City compared to the hilly regions of Wonosari and Kulonprogo, which have harder soil layers. The campus of Universitas Sarjanawiyata Tamansiswa (UST) is one of the campuses located in Yogyakarta City, where the regional geology is dominated by the Merapi Young Volcanic Deposits Formation. The UST campus area is vulnerable to earthquakes due to its proximity to an active seismic zone, making earthquake vulnerability mapping based on microseismic data an important necessity to support disaster mitigation efforts. The microseismic method was used in this study, while data analysis employed the Horizontal-to-Vertical Spectral Ratio (HVSR). Microseismic measurements were chosen because they have the advantage of not damaging the surface conditions of the ground, thus preserving the environment, and are easy to use in urban areas. The research method stages include survey design, field data collection, data processing and interpretation, and the creation of earthquake vulnerability maps. Data points were collected from 7 locations covering the Universitas Sarjanawiyata Tamansiswa campus area. The research results indicate that the study area has a dominant frequency value ranging from 1.10 to 2.74 Hz. Meanwhile, the amplification value ranges from 1.25 to 2.2. The sediment thickness of the study area ranges from 32 to 79 meters. The Seismic Vulnerability Index (Kg) of the study area ranges from 0.57 to 4 on a low to high scale. Based on the dominant frequency values, amplification, and seismic vulnerability index, the areas of the UST campus that are more vulnerable to earthquakes are the northern, eastern, and central parts, while the southern part is relatively safer.
The spatial variation of b-values in seismically active regions provides critical insight into the stress state and rupture potential of fault systems. This study focuses on the Java region and surrounding subduction zones, where detailed mapping of b-values remains uncertain despite high seismic risk. A Voronoi-based ensemble modelling framework is implemented, incorporating the Ogata-Katsura 1993 (OK1993) formulation and spatial sampling via Sobol sequences to ensure uniform partitioning. Earthquake data from 1995 onward were compiled and harmonized into moment magnitude (Mw) using conversion equations from the Indonesian Earthquake Source and Hazard Map 2017. The OK1993 model enables estimation of b-values optimized via trust-constr and initialized with maximum likelihood estimates. The results reveal that high b-values (b > 1.2) dominate offshore southwest Lampung and south of Bali, whereas low b-values (b < 0.8) appear parts of the Sumatra fault near the Sunda Strait, faults across Java, and thrusts north of Bali and Lombok. Moderate b-values (0.8–1.0) extend along the southern Java trench and may represent partially coupled megathrust segments. Interestingly, the low b-value zones may indicate locked asperities and potential seismic gap segments, especially along southern Java, where large ruptures have not occurred in recent decades. This study demonstrates the utility of spatially adaptive, data-driven approaches in capturing complex tectonic segmentation and supports their integration into future seismic hazard assessments in Indonesia, particularly in Java and its surrounding regions.
Cisarua, which contains a geothermal hot spring, is an intriguing area to investigate due to its location far from any known heat source or volcanic activity. Using the HVSR technique, this study aims to characterize the local site effects based on key parameters: natural frequency (fo), amplification factor (Ao), and average shear-wave velocity down to 30 meters depth (Vs30). Microtremor measurements were conducted at 25 locations across the Cisarua hot spring area, with an average spacing of 300 meters. Each site was recorded for 40–50 minutes, and the data were processed using Geopsy software to extract the HVSR curves, along with the fo and Ao values. The HVSR curves were then inverted using the Particle Swarm Optimization (PSO) algorithm to derive Vs30 values. The results show that fo values range from 0.6 to 1.1 Hz, and Vs30 values are generally below 175 m/s. These two parameters exhibit minimal spatial variation, indicating the presence of thick, soft, and relatively homogeneous sedimentary layers across most of the study area. The Ao values range from 2 to 5, with values below 3 dominating near the geothermal manifestation zone. The spatial distribution of fo and Ao reveals a northwest–southeast trend, which is strongly correlated with the presence of the Lampung–Panjang Fault that likely controls sediment accumulation and layer thickness in the area. Around point T13, Vs30 drops to 125–150 m/s, suggesting localized softening of the soil due to hydrothermal alteration processes. These findings emphasize the interplay between site effects, regional geological structures, and geothermal activity in shaping the dynamic properties of the subsurface in this area.
The Kawatuna area has a complex geological structure and lithological condition of metamorphic rock, which is estimated to be a weak zone for hydrothermal solutions to rise and then accumulate as mineralization of veins in the metamorphic rock. Based on this, it makes this area interesting to research. This research aims to identify metal ore minerals and the mineralization characteristics of ores in the research area. The method used is a geological survey of the surface and laboratory analysis through ore microscopic as well as mineral chemistry tests. Based on the results of the research study, it was found that in metamorphic rocks in the Kawatuna area, sulfide metal ore minerals were found including argentite (Ag2S), pyrite (FeS2), chalcopyrite (CuFeS2), sphalerite (ZnS), galena (PbS), and covelite minerals (CuS), Native elements ore minerals include gold (Au), silver (Ag), electrum (Au, Ag), and Oxide ore minerals in the form of hematite (Fe2O3). The mineralization formed is controlled by structures that produce fractures in the rock, which then produces mineralization as the veins of metamorphic rocks. The ore mineralization in the research area occurs through a hypogene process (the formation of a formation zone from primary ore minerals) and a supergene process stage (the formation of a formation or enrichment zone from secondary ore minerals).
Bathymetric mapping is crucial for understanding seabed conditions, especially in maritime countries like Indonesia. This study evaluates the quality of bathymetric data acquired using Multibeam Echosounder (MBES) in Jakarta waters. The acquired data was processed and analyzed based on the international standard IHO S-44. The results show that most acquired bathymetric data met the specified accuracy standard. However, some data did not meet the standard, especially in areas with varying depths. Bathymetric maps and seabed slope classification maps were successfully produced. The bathymetric map shows the complex morphology of the seabed, while the slope classification map indicates the dominance of flat areas. This research contributes significantly to efforts to improve the quality of bathymetric data in Indonesia.
Kotaagung Timur region, Tanggamus Regency, Lampung, is the focus area of this research. In general, the area has a unique and complex geological setting such as the variety of volcanic rocks, granite, and the Sumatran Fault System that through this area. Geological research aims to obtain geology dynamics about stratigraphy and geology structure in the research area. Two analyses have been done to achieve these goals, i.e., field observation, petrography analysis, and structural geology analysis. The stratigraphy units of the study area are composed of volcanic rocks, plutonic rocks, and surface deposits and can be divided into eleven lithostratigraphic units. The stratigraphy of the research area can be grouped into 5 groups, i.e., the Mount Gisting volcanic group, the granitoid pluton group, the Cawang Haro Mountains volcanic group, the Mount Tanggamus volcanic group, and the alluvial deposit. Geological structures are well developed, and the research area is cut by ten faults, such as dextral strike-slip faults, sinistral strike-slip faults, and reverse faults. Based on these things, the geological history of the study area started in the Late Oligocene with three episodes of volcanism. The first episode was Mount Gisting’s volcanism during the Late Oligocene-Early Miocene, followed by the granitoid intrusion. The volcanic products of the Cawang Haro Mountains in the Middle Miocene mark the second episode. The last volcanic episode occurred in the Holocene, it came from Mount Tanggamus’s volcanism. The development of the structural geology happened before the previous volcanism episode.
Batugamping atau batukapur adalah batuan yang secara umum berwarna keputihan, berbutir halus, tersusun oleh kalsium karbonat, dan terbentuk di bawah permukaan air laut. Wilayah Sumatera khususnya pada Daerah Sumatera Selatan memiliki potensi sumber daya mineral berupa batugamping yang terletak di kabupaten Ogan Komering Ulu. Pada Daerah penelitian ini termasuk kedalam formasi Baturaja (Nmb) dengan satuan batugamping baturaja dan formasi Gumai (Nmg) dengan satuan batugamping gumai yang secara stratigrafi terendapkan secara selaras. Bentukan asal pada daerah penelitian terbagi menjadi 2 yaitu bentuk asal struktural yang terdiri dari bentuk lahan lembah struktural (S1), dan bentuk asal antropogenik yang terdiri dari bentukan lahan bukan tambang (A1), bentukan lahan lereng tambang (A2) dan bentukan lahan sump (A3). Pada daerah penelitian secara pengamatan dilapangan terdapat struktur geologi yaitu berupa sesar mendatar kanan. Dengan pengamatan dilapangan dan keterdapatan sumberdaya batugamping di daerah penelitian dapat dilakukan penambangan di daerah tersebut. Dalam penambangan batugamping, diperlukan estimasi untuk dapat menghitung sumber daya sebelum proses penambangan berlangsung. Pada penelitian ini kedalaman lapisan batugamping dimodelkan dengan model blok dengan tujuan agar dapat melihat sebaran lapisan yang akan di estimasi kan. Untuk estimasi sumberdaya batugamping menggunakan metode Inverse Distance Weighting (IDW) dengan menaksir nilai pada area yang tidak memiliki sampel endapan batugamping berdasarkan data sekitar atau data terdekat.
Pekanbaru City is one of the cities appointed as a National Strategic Area. Therefore, urbanization and changes in land use occur in Pekanbaru City. This study aims to decide on land-use changes, obtain information on the direction of physical development in Pekanbaru City, and decide the suitability between physical development and the Pekanbaru City spatial planning plan. The method used in this study is quantitative descriptive, digitizing on screen to make land use maps and overlaying in 2017 and 2023 to see changes in land use. The direction of physical development is obtained using a standard deviational ellipse. The suitability of land use with RTRW was obtained using the intersect overlay method. The results of this study are 1) Changes in land use between 2017 and 2023 are dominated by settlements, industrial areas, and trade and services. For other land uses, there are also changes but not too significant. 2) The direction of physical development from the city center to the suburbs with a south and southwest direction. 3) The suitability between physical development and the Pekanbaru City Spatial Plan 2020 - 2040, as much as 33,6% is by the RTRW. Areas that are not following the RTRW are 63%. For areas that do not follow the RTRW, the figure is 3,4%. The conclusion of this study shows that most areas in Pekanbaru City have not been realized by the Pekanbaru City RTRW 2020-2040. With the increase in population, it is hoped that development will be achieved through the established development plan.
