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MULTI-MODEL VARIATION OF THE ENHANCED ASIAN RAINFALL AND CONTINENT-OCEAN THERMAL GRADIENT FROM PRE-INDUSTRIAL TO MID-HOLOCENE
Get PDFRainfall over the Asian continent during the mid-Holocene was higher than today as shown by the rainfall proxy records. During the mid-Holocene, increased rainfall over the Asian Continent has been suggested to be associated with the strengthening of the Asian Summer Monsoon (ASM) following a sharper continent-ocean thermal gradient. This study examined multi-model variation between changes of the continent-ocean thermal gradient and the increased rainfall over Asia during the mid-Holocene as compared to the pre-Industrial. We analyzed surface temperature, precipitation, and wind at 850mb from nine Global Climate Models (GCMs) which are all obtained from the database of the Paleoclimate Modeling Intercomparison Project Phase-3 (PMIP3). Multi-model analysis shows that changes in a continent-ocean thermal gradient has a positive correlation with ASM wind. However, a negative correlation occurs between changes in the continent-ocean thermal gradient with Asian rainfall. Models that simulate large changes in the continent-ocean thermal gradient produced the smallest increase in the Asian rainfall and vice versa. Such inverse relation is likely due to the cooling of Indian Ocean SST since its correlation scores with Asian rainfall is much higher than the one with the warming of the Asian continent. Thus, multi-model variation of the increased rainfall over the Asian continent between mid-Holocene and today is mainly related to the multi-model variation of the cooling in the Indian Ocean SST
KARAKTERISTIK INTRUSI AIR LAUT SERTA HUBUNGANNYA DENGAN KETINGGIAN DAN KEMIRINGAN LERENG
Get PDFWilayah pesisir merupakan daerah yang memiliki banyak potensi, namun terdapat banyak permasalahan di dalamnya, salah satunya intrusi air laut. Intrusi air laut merupakan permasalahan yang belum mendapatkan perhatian, baik dari masyarakat maupun pemerintah. Didukung dengan bentuk topografi daerah pesisir berupa dataran, sehingga semakin mempercepat terjadinya intrusi air laut. Penelitian dilakukan di daerah pesisir Kecamatan Kalianda, lebih tepatnya di Desa Way Urang, Desa Way Lubuk dan Kelurahan Kedaton. Tujuan penelitian ini untuk mendeskripsikan karakteristik intrusi air laut serta hubungan terhadap perubahan ketinggian dan kemiringan lereng. Data yang digunakan berupa data salinitas yang dikumpulkan menggunakan teknik purposive sampling. Data lainnya berupa SRTM yang diekstraksi menghasilkan data ketinggian dan kemiringan lereng. Data tersebut dilakukan analisis regresi polinomial untuk melihat hubungan intrusi air laut terhadap ketinggian dan kemiringan lereng. Berdasarkan hasil analisis, hubungan intrusi air laut terhadap ketinggian memiliki nilai R2 = 0,2334 sedangkan terhadap kemiringan lereng dengan nilai R2 = 0,317. Dari hasil penelitian, disimpulkan bahwa besarnya intrusi air laut memiliki hubungan yang lemah terhadap ketinggian dan kemiringan lereng
SEDIMENTATION RATES AND CALCAREOUS NANNOFOSSIL BIOSTRATIGRAPHY OF THE NANGGULAN FORMATION, KULON PROGO, INDONESIA
Get PDFThe Nanggulan Formation is the oldest sedimentary rock of Paleogene age that was deposited in the eastern part of the Southern Central Java Basin. A total of 103 nannofossil samples were taken from two traverses in the study area, i.e., the Watupuru and Jetis Routes. Based on the biodatum identified from the nannofossil samples, the biostratigraphy of the rock formation is divided into five zonations, namely the upper part of Zone NP16, Zone NP17, the lower part of Zone NP18, the upper part of Zone NP22, and the lower part of Zone NP23, expanding from 41.1 Ma to 32.2 Ma of age (Middle Eocene to Early Oligocene). Only Zone NP17 is identified as a complete zone, whereas the other four are observed as partial. The fluctuation of global sea level is believed to be an influence on the deposition of the Nanggulan Formation. The sedimentation rate and the change of nannofossil species shows a decrease of oligotrophic (Sphenolithus) and an increase of eutrophic (Reticulofenestra) taxa, especially in small reticulofenestrids (Reticulofenestra spp.). This occurrence suggests a shift in the environmental conditions from an oligotrophic condition around 41.1 Ma to a eutrophic one, particularly after 40.40 Ma. The enhanced eutrophication in the Watupuru and Jetis Routes was caused by an increasing terrigenous input in 40.40 Ma and after, consequently providing nutrient availability on the water surface. This interpretation is supported by the increase in the sedimentation rate when sea level slightly decreased in 40.40 Ma
REVIEW: SEDIMENTASI DAN PENYEMPITAN MIXING ZONE DI PERAIRAN PESISIR MUARA TAWAR, KABUPATEN BEKASI - JAWA BARAT
Get PDFKajian geologi kelautan berdasarkan data citra satelit resolusi tinggi dan data hidro-oseanografi regional Teluk Jakarta yang dipublikasikan, menunjukan adanya perubahan lingkungan eksternal di sekitar tapak PLTGU Muara Tawar secara signifikan. Perubahan tersebut berupa penyempitan dan pendangkalan perairan di daerah Mixing Zone seluas kurang lebih 90-an Ha dalam kurun waktu sepuluh tahun terakhir. Situasi seperti ini menunjukan penurunan mutu lingkungan di area mixing zone, yaitu tempat bercampurnya air bahang dari kondensor melalui outfall dengan airlaut baku yang masuk melalui saluran intake. Kajian ini mensiratkan perlunya usulan pengendalian alih lahan di pesisir perairan Muara Tawar serta adanya pemeliharaan dan pendalaman area mixing zone terutama di dekat mulut outfall agar cukup memberi waktu bagi proses pendinginan air bahang dari pembangkit.
PETROPHYSICAL ANALYSIS AND SEISMIC STRATIGRAPHY INTERPRETATION TO DETERMINE HYDROCARBON RESERVOIR IN TARAKAN BASIN, BUNYU ISLAND WATERS
Get PDFTarakan Basin area of Bunyu Island Waters is known to have hydrocarbon potential with complex geological structures. This study aims to determine reservoir characterization and to obtain prospect of hydrocarbon reservoir zones based on petrophysical and seismic stratigraphy analysis with reference to Well DDS-1 and 2D seismic Line S88. Petrophysical analysis results 3 zones that have potential as hydrocarbon reservoirs. Based on petrophysical quantitative analysis, Zone 1 has values of 52.25% for shale volume, 18.48% for effective porosity, 39.84% for water saturation and 13.03 mD for permeability. Zone 2 has values of 54.66% for shale volume, 10.27% for effective porosity, 40.9% for water saturation and 1.14 mD for permeability. Zone 3 has values of 49.22% for shale volume, 9.33% for effective porosity, 56.33% for water saturation and 0.22 mD for permeability. Out of these three reservoir zones in Well DDS- 1, Zone 1 has the prospect of hydrocarbons which is supported by the net pay value. Based on seismic stratigraphy interpretation, the reservoir zone is correlated to the Tabul Formation, which comprises calcareous clay and limestone
QFL AND LITHO FACIES: PREDICTING RESERVOIR QUALITY OF THE MIDDLE MIOCENE DEEP-WATER FACIES AT KUTEI AND NORTH MAKASSAR BASINS
Get PDFAs we may all be aware the oil and gas wellbores offshore Kutei and North Makassar have not optimally penetrated the objective strata, which is the Middle Miocene’s deep-water reservoirs. Therefore, evaluating the quality of these reservoirs with onshore dataset then comparing them with the proven Late Miocene’s deep-water producing reservoirs had been very fundamental. The study focuses on the assessment of QFL and sandstones litho-facies based on the rock samples from conventional-core and side-wall core, and well-logs data from forty wells onshore and offshore. These rock samples are bounded by the key biostratigraphy intervals of M40M33, M45M40, M50M45 (Middle Miocene), and M65M50, M66M65, M70M66, M80M70 (Late Miocene). Subdivisions of the reservoirs considered the sandstone litho facies, NTG ratio, sorting, and grain size, to come up with five groups in the Middle Miocene deltaic facies: FLU_SX, DC_SX, DC_SM, DC_SM, and DF_SC; and four groups in the Late Miocene deep-water facies: SSWS, MSWS, SSPS, and MSPS. Core-based porosity and permeability further explain the relationship between the reservoir quality with the sandstones’ composition and litho facies, and concluded that high-energy depositional system is mainly associated with the FLU_SX, DC_SX, SSWS and MSWS being the reservoir with best quality. Oppositely, the DF_SC, SSPS, and MSPS are classified the reservoir with worst to none quality. A cross plot between core-based porosity and maximum burial depth is able to postulate the relational trend of decreasing reservoir quality with deeper depth
STUDI IDENTIFIKASI PERANGKAP HIDROKARBON PALEOGEN - NEOGEN DI PERAIRAN WOKAM ARU UTARA, PAPUA BARAT: DATA UTAMA HASIL SURVEI GEOMARIN III
No full textABSTRAKPerairan Wokam Aru Utara, Papua Barat merupakan bagian tepi utara passive margin Mesozoik Arafura – Australia. Hasil survei dengan KR. Geomarin III di perairan Wokam 2014 diperoleh lintasan seismik Multi Kanal 1.182 km, dan pemeruman batimetri/sub bottom profiles (SBP) 1.510 km. Metode dilakukan interpretasi penampang seismik hasil survei, pengikatan sumur pemboran dan seismik, analisis petrofisika dan pemetaaan geologi bawah permukaan. Pada penampang seismik telah dilakukan interpretasi aspek struktur geologi dan perlapisan sedimen yang sebelumnya telah diikat dengan data sumur ASA-1X, ASM-1X dan ASB-1X untuk tiga horizon yaitu Top Neogen, Top Paleogen dan Base PaleogenPeta bawah permukaan Paleogen – Neogen menunjukan beberapa klosur yang berpotensi di bagian batas paparan dengan palung Aru serta bagian barat. Pada bagian Tenggara terdapat kenampakan onlapping sedimentasi Tipe struktural yang berkembang sebagai perangkap secara dominan berupa graben – half graben dan tilted faul. Onlaping sedimentasi yang mebaji juga dapat berpotensi.Struktur geologi pada area penelitian secara umum dikontrol oleh sesar utama Zona Sesar Palung Aru Utara di tepian paparan sampai lereng, mengarah utara - timur laut ke selatan - barat daya. Struktur ikutan yaitu sesar-sesar normal mengarah utara - timur laut ke selatan - barat daya di paparan sebelah timur zonar sesar utama.Studi awal potensi migas ini teridentifikasi empat lokasi potensi perangkap hidrokarbon dari umur Paleogen - Neogen, yaitu satu lokasi dari Peta Base Paleogen, dua lokasi Top Paleogen dan satu lokasi Top Neogen. kata kunci: Wokam, Aru, migas, seismik, struktur, interpretasi, jebakan, Geomarin III ABSTRACTThe waters of Wokam North Aru, West Papua are part of the northern edge of the Mesozoic passive margin of Arafura - Australia. Survey results with KR. Geomarin III in the waters of Wokam 2014 obtained a multi-channel seismic trajectory of 1,182 km, and bathymarism/sub bottom profiles (SBP) 1,510 km. The method is to interpret the seismic cross-section of the survey results, tie drilling and seismic wells, petrophysical analysis and mapping the subsurface geology. In the seismic section, an interpretation of the structural aspects of the geology and sediment layers has been carried out previously tied to data from the ASA-1X, ASM-1X and ASB-1X wells for three horizons, namely Top Neogen, Top Paleogene and Base Paleogene.The subsurface map of the Paleogene - Neogeneous surface shows several potential closures in the exposure boundary with the Aru Trench as well as the western part. In the Southeast, there is the appearance of sedimentation onlapping. Structural types that develop as traps are predominantly graben - half graben and tilted fault. The onlaping sedimentation also has potential. The geological structure in the study area is generally controlled by the main fault of the North Aru Trench Zone on the edge of the exposure to the slope, heading north - northeast to south - southwest. Follow-up structures are normal faults pointing north - northeast to south - southwest on the eastern exposure of the main fault zone.This preliminary study of oil and gas potential identified four potential locations for hydrocarbon traps from the Paleogene - Neogene age, namely one location from the Paleogene Base Map, two Top Paleogene locations and one Top Neogen location.Keyword: Wokam, Aru, oil and gas, seismic, structure, interpretation, traps, Geomarin II
STUDI IDENTIFIKASI DASAR LAUT DALAM PENDETEKSIAN PIPA BAWAH LAUT (STUDI KASUS PIPA PERTAMINA BALIKPAPAN)
No full textPada tanggal 31 Maret 2018 telah terjadi pencemaran laut yang diakibatkan oleh tumpahnya minyak bumi di perairan Balikpapan. Hasil survei ditemukan bahwa tumpahan minyak di perairan tersebut terjadi karena patahnya pipa bawah laut milik Pertamina. Dalam upaya identifikasi pipa tersebut, digunakan 3 peralatan survei bawah laut yakni Multibeam echosunder (MBES), Side Scan Sonar (SSS) dan Magnetometer. Peralatan survei yang digunakan, berbeda pada tahap akusisi maupun tahap analisis dalam memperoleh informasi yang akan disajikan, oleh karena itu, diperlukan metode serta analisis tertentu untuk mempercepat identifikasi suatu objek dibawah laut. Selain menyediakan informasi batimetri, MBES memiliki fitur informasi hambur balik (backscatter) yang dapat digunakan untuk memperoleh nilai intensitas akustik yang dapat digunakan untuk mengidentifikasi jenis sedimen (substrat dasar laut) dan objek dasar laut lain berdasarkan tingkatan nilai intensitas akustik. Dengan nilai intensitas akustik tersebut suatu objek bawah laut dapat segera diidentifikasi di lapangan. Hasil identifikasi dengan nilai intensitas akustik di area perairan Balikpapan diperoleh material pipa bawah laut memiliki intensitas akustik sebesar 24,1 dB dan sedimensi berupa Lanau sedang (Medium Silt) dan Pasir sangat halus (Very Fine Sand)