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Riza Rahardiawan
Kementerian ESDM
Earth & Planetary Sciences

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INTERPRETASI LAPISAN SEDIMEN DASAR LAUT DI PERAIRAN UTARA JAWA (LEMBAR PETA 1310) MENGGUNAKAN SUB BOTTOM PROFILE Stephanie, Stephanie; Widada, Sugeng; Rahardiawan, Riza
Journal of Oceanography Vol 3, No 4 (2014)
Publisher : Program Studi Oseanografi, Jurusan Ilmu Kelautan, Universitas Diponegoro

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (611.847 KB)

Abstract

Sedimen dasar laut dapat mendeskripsikan kondisi geologi yang terjadi di masa lampau hingga masa kini. Penelitian ini bertujuan untuk mengetahui kondisi lapisan-lapisan sedimen dasar laut Perairan Utara Jawa (Lembar Peta 1310) berdasarkan profil penampang seismik Sub Bottom Profile. Pengambilan data lapangan dilakukan pada bulan September 2013 menggunakan kapal Geomarin I milik Pusat Penelitian dan Pengembangan Geologi Kelautan, Kementerian Energi dan Sumber Daya Mineral,analisa sedimen dilkukan pada bulan November, 2013 di Laboratorium Geologi P3GL, Cirebon. Metode penelitian yang digunakan bersifat deskriptif denganmateri yang diteliti berupa data pemeruman dasar laut, sampel sedimen dasar dan data rekaman seismik Sub Bottom Profile. Hasil interpretasi menunjukansedimen dasar pada daerah penelitian dkelompokan dalam 4 lapisan pengendapan yang terdiri dari Unit 1 adalah lapisan terluar sedimen berumur resen dengan fraksi butir halus. Unit 2 merupakan bidang batas sekuen erosional truncation yang mengidentifikasikan terjadinya erosi.Unit 3 adalah lapisan sedimen yang sebagian telah terkikis karna berbatasan dengan bidang erosi dan basemen akustik.Unit 4 adalah lapisan akustik basemen yang telah mengalami deformasi.Berdasarkan hasil analisa sampel sedimen dasar pada daerah penelitian berupa lempung dan lanau pasiran.
GRAVITY MODELING OF SUBSURFACE STRUCTURES AND RESERVOIR CHARACTERIZATION USING SEISMIC INVERSION IN THE NIAS BASIN Wibowo, Ramadhana; Setiadi, Imam; Firdaus, Yulinar; Rahardiawan, Riza
BULLETIN OF THE MARINE GEOLOGY Vol 39, No 2 (2024)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.32693/bomg.39.2.2024.890

Abstract

The development of interpretation techniques opens new exploration opportunities in the forearc basins of western Indonesia, such as the Nias Basin which show signs of oil and gas seepage. Gravity and seismic inversion analysis were used to look into the Nias Basin in order to evaluate its subsurface structure, the location of sedimentary sub-basins, and the possible presence of hydrocarbon reservoirs. After filtering the data for the Complete Bouguer Anomaly (CBA), a residual anomaly was obtained. This allowed for the quantitative interpretation of structures below the surface using 2D gravity forward modelling. Seismic and well data interpretation includes sensitivity analysis, a well-seismic tie, picking horizons, and acoustic impedance (AI) inversion. The residual gravity anomaly reveals eight sub-basin patterns spread out in the Nias Basin with a relative continuity direction of northwest-southeast following the lineaments of basement highs. The subsurface geological model identified four rock formations. From deepest to shallowest, these units are metamorphic bedrock (2.7 g/cc), Lelematua Formation (2.5 g/cc), Gomo Formation (2.4 g/cc), and Gunungsitoli Formation with an overlying alluvium (2.25 g/cc). Interpretation of well and seismic suggests a target zone at a 2,017 – 2,101 meters depth. Using a model-based hard constraint for AI inversion in this zone indicates possible carbonate reservoirs. Based on sensitivity analysis with an interval of 34,000 - 47,000 (ft/s)*(g/cc), an AI cutoff value of more than 34,000 (ft/s)*(g/cc) was obtained. The carbonate is estimated to be a tight carbonate in the limestone of the Gomo Formation.
GEOCHEMISTRY OF SEABED AND COASTAL SEDIMENTS IN LIMAU WATERS AREA Zulfikar, Muhammad; Saputro, Eko; Albab, Ali; Rahardiawan, Riza
BULLETIN OF THE MARINE GEOLOGY Vol 40, No 2 (2025)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.32693/bomg.40.2.2025.953

Abstract

Sediment provenance and weathering history are used to understand sedimentary processes and to explore mineral potential in coastal–marine systems in the Limau Waters. Therefore, the characteristics of seabed and coastal sediments need to be determined. This study aims to identify the source rocks, paleoweathering signatures, and sediment maturity of both seabed and coastal sediments through a geochemical approach. A geochemical approach that integrates major oxide and rare earth element (REE) analyses, the paleoweathering, and sediment maturity indices, is used to identify the source rocks of these sediments. Major oxides elements were measured using X-ray fluorescence (XRF) and REE concentrations were determined using inductively coupled plasma - optical emission spectrometry (ICP-OES) and inductively coupled plasma optical - mass spectrometry (ICP-MS). Geochemical discrimination diagrams indicate that seabed sediments are mainly derived from intermediate to felsic igneous rocks with higher compositional maturity, whereas coastal sediments are influenced by mafic volcanic rocks and are comparatively immature in composition. Both sediment types exhibit weak chemical weathering (CIA < 70), suggesting limited alteration of young volcanic sources. The CIA–ICV relationships portray contrast sediment transport and depositional processes between the coastal and marine environments. This study is expected to provide a geochemical-based framework for provenance analysis and to support the development of insights for future marine mineral exploration in the Limau Waters area.
HYDROCARBON POTENTIAL OF THE OFFSHORE AKIMEUGAH BASIN FROM MESOZOIC-PALEOZOIC BASED ON GEOLOGICAL AND GEOPHYSICAL ANALYSIS Setiadi, Imam; Rasyid, Faris N; Zulivandama, Shaska Ramadhan; Firdaus, Yulinar; Santy, Lauty D.; Saleh, Hanif M.; Rachman, Muhammad G.; Djaja, Andrian W.; Nurdin, Nazar; Rahardiawan, Riza; Subarsyah, Subarsyah
BULLETIN OF THE MARINE GEOLOGY Vol 40, No 2 (2025)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.32693/bomg.40.2.2025.954

Abstract

Akimeugah Basin is one of the basins with discovery status, however hydrocarbon production has not yet been established. One of potential petroleum play type for further investigation, estimated to contain hydrocarbon reserves in the offshore Akimeugah Basin, is the Mesozoic–Paleozoic sedimentary play, interpreted to have originated from the Australian passive margin. This study aims to analyze geological and geophysical data to delineate the sub-basin pattern and characterize petroleum system elements. The analysis integrates gravity data interpretation, geochemical evaluation of source rocks, and subsurface interpretation based on seismic and well data. Results indicate that source rocks in the Kola-1 well are primarily composed of Type III (gas-prone) and secondarily of Type II (oil/gas-prone) kerogen. Thermal maturity analysis shows that the Woniwogi, Aiduna, and Modio Formations have reached the oil window. Reservoir potential has been identified in the Tipuma Formation (Triassic), Aiduna Formation (Permian), and Modio Dolomite (Devonian–Silurian). Seal rocks consist of regional and intraformational units composed of tight siltstone and shale. Trapping mechanisms in this area include a combination of structural traps such as fault-bounded anticlines and stratigraphic traps represented by sub-unconformities. Identified exploration leads include seven within the Modio Dolomite structural play, six within the Permian Aiduna Sandstone play, and four within the Triassic Tipuma Sandstone play.
ACOUSTIC FACIES AROUND THE INTRUSIVE COMPLEX OF SALAHNAMA AND PANDANG ISLANDS, MALACCA STRAIT , S.Si., MT., Subarsyah; Albab, Ali; Zulivandama, Shaska Ramdhan; Saputro, Eko; Ali, Arif; Setiadi, Imam; Zulfikar, Muhammad; Nauval, Faris; Rahardiawan, Riza
BULLETIN OF THE MARINE GEOLOGY Vol 40, No 2 (2025)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.32693/bomg.40.2.2025.938

Abstract

Salahnama and Pandang Islands lie on the main range of the granite province; both islands are located in the Sunda Shelf, Malacca Straits. These islands are composed of intrusive rocks from Berhala. The rock’s existence will offer a significant contribution to the distribution of surface sediments in the surroundings. The sea dynamics and the geometry of the Malacca Strait will also have an impact on the seabed. Apart from that, global factors such as sea level changes will lead to transformation of the depositional environment and subsurface geology in the strait. Geological conditions of the seabed surface and subsurface can be understood and interpreted based on the acoustic characteristics and reflector patterns of a seismic section. Then, based on the acoustic character and reflector pattern, an acoustic facies can be defined. Seismic data measurements have been carried out around Salahnama and Pandang Islands in 2024. Based on the results of the seismic section, the acoustic facies in the study area are classified into 6 (six), which include AF I – AF VI. Seabed morphological features in the form of sand dunes were identified in the first acoustic facies (AF I); this feature is formed due to geometric aspects, surface currents, and bottom current's which may or may not be triggered by tidal vortices. Acoustic Facies II (AF II) is characterized by sandwave or ripple marks formed by strong seabed currents. AF III was formed after the Last Glacial Maximum (LGM) ended and the depositional environment returned to a shallow marine environment, characterized by a transparent pattern in the seismic section. The erosional truncation at the upper boundary of AF IV indicates a change in the depositional environment from shallow marine to coastal or terrestrial environments during the Last Glacial Maximum period. AF V is acoustic bedrock, and AF VI is characterized by a chaotic pattern, which is interpreted as granitic intrusive rocks.
Co-Authors , S.Si., MT., Subarsyah Albab, Ali arif ali, arif Djaja, Andrian W. Eko Saputro, Eko Imam Setiadi, Imam Muhammad Zulfikar Nauval, Faris Nazar Nurdin Rachman, Muhammad G. Rasyid, Faris N Saleh, Hanif M. Santy, Lauty D. Stephanie Stephanie Subarsyah Subarsyah Sugeng Widada Wibowo, Ramadhana Yulinar Firdaus, Yulinar Zulivandama, Shaska Ramadhan Zulivandama, Shaska Ramdhan