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Implementation of the Poisson Impedance Inversion to Improve Hydrocarbon Reservoir Characterisation in the Poseidon Field, Browse Basin, Australia Hartagung, Riky Tri; Rosid, Mohammad Syamsu
Jurnal Penelitian Fisika dan Aplikasinya (JPFA) Vol. 12 No. 2 (2022)
Publisher : Universitas Negeri Surabaya

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.26740/jpfa.v12n2.p102-114

Abstract

The prediction process of lithology and fluid content is the most important part of reservoir characterization. One of the methods used in this process is simultaneous seismic inversion. In the Poseidon field, Browse Basin, Australia, the parameters generated through simultaneous seismic inversion cannot accurately characterize the reservoir because of the overlapping impedance values between hydrocarbon sand, water sand, and shale, which cause a high level of ambiguity in the interpretation. The Poisson impedance (PI) inversion provides a solution to this problem by rotating the impedance a few degrees through coefficient c. Coefficient c is obtained through the target correlation coefficient analysis by finding the optimum correlation coefficient between the PI and the target log, namely, gamma rays, effective porosity, and resistivity. The results show that the PI gives better outcomes in separating hydrocarbon-saturated reservoir zones. Based on the results of the lithology impedance–gamma rays, the ϕI-effective porosity cross-plot, and the fluid impedance-water saturation (Sw) cross-plot, with optimum correlations of 0.74, 0.91, and 0.82, respectively. The lithology of hydrocarbon-saturated porous sand is at values of LI ≤ 2800 (m/s)(g*cc), ϕI ≤ 5500 (m/s)(g*cc) and FI ≤ 4000 (m/s)(g*cc). The presence of low values for LI, ϕI and FI correlates accurately with the presence of hydrocarbons in the well. Each value of c is then applied to the seismic data. The results show that this method can determine the distribution of gas-saturated porous sand on the seismic inversion section in the northeast–southwest direction.
Penentuan Model Kecepatan Seismik 1-D di Pulau Lombok Bunaga, I Gusti Ketut Satria; Rosid, Mohammad Syamsu; Anggono, Titi; Septiadhi, Ardhianto
Jurnal Penelitian Pendidikan IPA Vol 9 No 12 (2023): December
Publisher : Postgraduate, University of Mataram

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29303/jppipa.v9i11.6023

Abstract

The interpretation of local geology structure can be done effectively by using an appropriate local seismic velocity model. It is suitable to implement in Lombok Island that the local fault activity near Mount Rinjani caused the 2019 East Lombok Earthquake. This study determines and updates the 1-D seismic velocity model using the VELEST by applying the Coupled Hypocenter-Velocity method. The 2010-2022 earthquake data from the catalog of BMKG is used for this study. A total of about 166 events (M ≥ 4) and 20 seismic stations in Lombok and surrounding areas are utilized in this study. The local model (Koulakov) and global (AK-135) are selected as the initial model. The double-difference method is also used to test both velocity models refining the hypocenter location. The results show that the updated Koulakov model has a high relevance in representing the crustal structure of Lombok Island according to the parameters of RMS value, uncertainties hypocenter, and seismic interpretation. It demonstrates not only the local geology condition but also a more reliable seismic velocity model in the region of Lombok Island. This model can be used as a reference for interpreting the better geological structure.
Distribusi Kerentanan Seismik di Wilayah Pusat Kota Surabaya Akbar, Dzikrullah; Rosid, Mohammad Syamsu; Darmanto, Aina Najwa
Jurnal Penelitian Pendidikan IPA Vol 10 No 3 (2024): March
Publisher : Postgraduate, University of Mataram

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29303/jppipa.v10i3.6761

Abstract

Surabaya is the second major city of Indonesia and the economic capital of eastern Indonesia. The city’s central area is the governmental center of East Java Province. This area is traversed by the Surabaya section of the Kendeng Fault which could potentially generate a maximum M6.5 earthquake. The East Java megathrust zone also threatens this area with a potential maximum magnitude of M8.9 earthquake. The rock geology of this region is dominated by soft alluvial soil which could amplify earthquake shaking. This study aims to identify the distribution of seismic vulnerability index in Surabaya’s central area. Therefore, microtremor measurements were carried out at 61 points in this area. The results were then analyzed using the Horizontal to Vertical Spectral Ratio (HVSR) method to determine the amplification factor values and seismic vulnerability index. The results of the HVSR analysis show that the amplification factor value and seismic vulnerability index are in the low to medium category ranging from 0.8370 - 3.8298 and 0.6041 - 14.6268, respectively. The distribution of the results shows that the northern area is more vulnerable than the southern part. This is verified by the geological conditions of the northern part which is dominated by alluvial soil.
Perbandingan Hasil Data Gravitasi Permukaan Tanah dan Satelit GGMPlus (Studi Kasus: Cekungan Kalibening) Wiguna, I Putu Arix Putra; Rosid, Mohammad Syamsu; Saputra, Frilla Renty Tama
Jurnal Penelitian Pendidikan IPA Vol 10 No 8 (2024): August
Publisher : Postgraduate, University of Mataram

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29303/jppipa.v10i8.7318

Abstract

As technology develops, many satellite gravity data with world coverage and high resolution have become available, one of which is GGMPlus. However, the quality of the resulting satellite gravity data is still doubtful, because the GGMPlus satellite data is the result of calculations. This research will compare satellite data with land surface data in the Kalibening Basin area to see the precision and correlation of satellite data with land surface data. Land surface data was obtained from field measurements using Scintrex CG-5 with a grid between stations of 500-1000m and GGMPlus satellite gravity data with a distance between points of 600m. The results obtained show that the residual anomaly maps have many similarities, while the regional anomalies provide quite significant differences between the two data. The slicing results show a density contrast that is similar to the two data and matches the geological boundaries of the Kalibening Basin. Based on the results obtained, GGMPlus data can be an alternative to fill the gaps in field data or as supporting data in disaster mitigation and exploration in general. The correlation between land surface data and GGMPlus is quite rational with a value of R2 = 0.95 and RMSE = 6.89mGal.
Multi-Station ULF Geomagnetic Analysis for Enhanced Earthquake Precursor Identification Winata, Eresia Nindia; Syamsu Rosid, Mohammad; Febriani, Febty
Journal of Engineering, Technology, and Applied Science (JETAS) Vol 7 No 3: December 2025
Publisher : Lamintang Education and Training Centre, in collaboration with the International Association of Educators, Scientists, Technologists, and Engineers (IA-ESTE)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.36079/lamintang.jetas-0703.931

Abstract

Western Java’s ongoing seismic hazard highlights the need for understanding earthquake precursor mechanisms. Recent studies have increasingly focused on ultra-low-frequency (ULF) signals that may carry information related to pre-seismic phases. However, a key difficulty persists: isolating faint, localized lithospheric signals from the stronger ionospheric activity. Most previous investigations in Western Java have relied on single-sensor measurements, a limitation that complicates the detection of true anomalies. This study addresses this limitation by examining daily ULF variations before the 2023 Banten earthquake sequence (M5.4 and M5.1), using a multi-point setup to distinguish lithospheric signals from stronger background ionospheric noise. Continuous three-component geomagnetic data from two primary stations near the epicenter, Serang (SRG) and Sukabumi (SKB), and a distant reference station (TRD) in East Kalimantan were analyzed. The Z/G spectral density ratio was calculated in the 0.01–0.09 Hz range, using only data from quiet nighttime intervals (15:00–21:00 UTC) and magnetic storm-free days (Dst > -50 nT). The results identified and filtered false positive anomalies by correlating them with signals at the TRD reference station. Two distinct, validated pre-seismic anomalies were identified, concentrated in the 0.04–0.08 Hz band: a multi-station anomaly at H-20 (at SRG and SKB) and a localized, broadband anomaly at H-15 (at SRG). Both emissions were absent at TRD, confirming their lithospheric origin. These results highlight the importance of a multi-station approach for reliably identifying lithospheric ULF anomalies. However, this study is limited to a specific event sequence. Future investigations should focus on integrating broader sensor networks and ionospheric models across multiple seismic events to validate these findings globally and enhance false positive rejection methods.
Identification of Natural Recharge Characteristics Based on Time-Lapse Microgravity Data for Sustainability Utilization at Lahendong Geothermal Field, Indonesia Agung, Lendriadi; Syamsu Rosid, Mohammad; Tofan Sastranegara, Mochamad; Lolla Riandari, Baiq
Indonesian Journal on Geoscience Vol. 13 No. 1 (2026)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.13.1.13-29

Abstract

The sustainable utilization of geothermal resources heavily relies on maintaining the fluid mass balance within the reservoir. Excessive fluid extraction without sufficient natural recharge can cause significant declines in reservoir pressure, thus threatening the long-term sustainability of geothermal energy production. This study specifically addresses the challenge of accurately characterizing natural recharge dynamics in the Lahendong Geothermal Field, where ongoing exploitation activities have led to considerable fluid mass deficits. To tackle this issue, time-lapse microgravity monitoring was conducted annually from 2015 to 2023 across 118 gravity benchmark stations strategically distributed throughout the reservoir area. The collected microgravity data were analyzed using Gauss's theorem to quantify the changes in reservoir mass balance over time. The calculated reservoir mass changes based on microgravity data were validated against mass balance estimates derived from actual well flow rate measurements. The findings indicate that natural recharge in Lahendong varies significantly, ranging from 0 to 3 M ton/year, exhibiting a clear cyclical pattern with approximately three-year intervals. On the average, natural recharge supplies approximately 1 M ton/year to the reservoir. The results validate time-lapse microgravity monitoring as a robust tool for detecting reservoir mass changes, offering critical insights into adaptive fluid injection strategies.
Developing 1-D velocity model along Matano Fault Zone, Sulawesi, Indonesia Madona, Madona; Rosid, Mohammad Syamsu; Handoko, Djati; Sianipar, Dimas Salomo Januarianto
Journal of Physics and Its Applications Vol 8, No 1 (2026): February 2026
Publisher : Diponegoro University Semarang Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.14710/jpa.v8i1.29859

Abstract

The Matano Fault, with a slip rate of ~ 20 mm/year, is the most active strike-slip fault in Sulawesi after the Palu-Koro Fault. As a result, this region exhibits a high level of seismicity. Unfortunately, a number of studies that have been conducted only involve a less dense network of stations and global velocity models. This study aims to obtain an optimum velocity model using the VELEST program, which reliably represents the actual condition of the study area. The data used in this study consists of hypocenter, origin times, and P-wave arrival times from earthquakes (Mw ≥ 3), each containing at least six clearly identified P-wave phases. These data were obtained from 317 events that occurred within the region bounded by 120.10°E – 122.20°E and 2.99°S – 1.66°S during the period from January 2022 to March 2025. To determine the optimum 1-D velocity model, four initial models were tested, namely Koulakov, Arimuko, Crust, and Bunaga. These models were evaluated based on RMS, the stability test of the updated velocity model, uncertainty assessment using bootstrap test, and their consistency with previous studies. The evaluation results indicate that the Arimuko Model is the most reliable, as it provides the lowest RMS value, stable hypocenter relocations (±6–7 km), bootstrap results showing narrow uncertainty intervals, and consistency with earlier studies that identified a low-velocity zone at depths of 0–3 km. The result of this study is expected to serve as a reference for earthquake relocation and seismicity analysis at the Matano Fault Zone.