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INDONESIA
BULLETIN OF THE MARINE GEOLOGY
Published by Marine Geological Institute of Indonesia
ISSN : 14106175     EISSN : 25278843     DOI : -
Core Subject : Science,
Earth & Planetary Sciences
Bulletin of the Marine Geology is a scientific journal of Marine geoscience that is published periodically, twice a year (June and December). The publication identification could be recognized on the ISSN 1410-6175 (print) and e-ISSN: 2527-8843 (on-line) twice a year (June & December) and it has been accredited by Lembaga Ilmu Pengetahuan Indonesia (Indonesian Institute of Sciences) by Decree Number: 818/E/2015. As an open access journal, thus all content are freely available without any charge to the user. Users are allowed to download, and distribute the full texts of the articles without permission from the publisher.
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Articles 5 Documents
 1 
Search results for , issue "Vol 34, No 1 (2019)" : 5 Documents clear
Seabed Characterization through Image Processing of Side Scan Sonar Case Study: Bontang and Batam Subarsyah Subarsyah; Lukman Arifin
BULLETIN OF THE MARINE GEOLOGY Vol 34, No 1 (2019)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (10200.514 KB) | DOI: 10.32693/bomg.34.1.2019.590

Abstract

Acoustic waves propagate through a medium meet the Snell’s Law, its energy is reflected and some are scattered back at certain angle. The Side Scan Sonar (SSS) methods use this principle to identify seabed character. The intensity of the backscatter greatly depends on the morphology and sediments texture or rocks distributed on seabed.The intensity of backscatter waves is a representation of the morphology, sediments texture, and types of rock that distributed on the seabed, therefore it is possible to estimate sedimentary texture and identify the presence of rocks or coral reefs based on this information. In this publication authors estimate sediments texture, rocks or coral reefs based on backscatter intensity through the image processing on the Side Scan Sonar (SSS) image. Intensity will be converted into pixel values on the image with range value 1-255 (gray scale image) and entropy values which are statistical measures of randomness. Entropy value is maximum when most of pixel value image is in the middle of the colour spectrum range (between very dark to very bright), in contrast, it is minimum when pixel value is in the spectrum of very dark or very bright. Based on both parameters, classification is conducted. The classification is carried out on the SSS image at Bontang and Batam that have very different seabed characters.The classification results using an image processing shows that the distribution of sediment textures consist of 4 (four) classes for either Batam or Bontang. In the Bontang area, very fine sediments were identified which are associated with low value of both intensity and entropy - dark zones in gray scale images, and coarse sediments associated with high value of both intensity and entropy - bright zone in the gray scale image. Similar characteristic is observed in Batam area, which are identified fine sediment (associated to low intensity) - coarse sediments (high intensity). In contrast to Bontang, in Batam the entropy exhibit the opposite value, high value are correlated to fine sediment and vice versa. This might be due to the presence of rocks and sedimentary structures.Keywords: Side Scan Sonar, Intensity, Backscatter and entropy.Gelombang akustik sebagian besar energinya dipantulkan memenuhi prinsip snellius dan sebagian kecil dihamburkan balik dengan sudut. Metode Side Scan Sonar (SSS) memanfaatkan prinsip hambur-balik gelombang untuk mengidentifikasi permukaan dasar laut. Intensitas gelombang dari karakter hambur-balik akan sangat tergantung morfologi dan tekstur sedimen atau batuan dari permukaan dasar lautnya. Intensitas gelombang hambur-balik merupakan representasi dari morfologi, tekstur sedimen, dan jenis batuan yang tersebar di permukaan dasar laut, sehingga sangat memungkinkan untuk melakukan estimasi tekstur sedimen dan identifikasi keberadaan batuan maupun terumbu karang berdasarkan informasi tersebut. Pada publikasi ini akan dilakukan estimasi tekstur sedimen atau batuan berdasarkan intensitas hambur-balik melalui image yang dihasilkan oleh Metode Side Scan Sonar (SSS). Intensitas akan dikonversi ke dalam nilai pixel dalam image dengan rentang nilai 1-255 (gray scale image) dan nilai entropi yang merupakan ukuran statistik ketidakteraturan dari image. Entropi akan maksimum ketika nilai pixel kebanyakan di tengah dari rentang spektrum warna dan sebaliknya akan minimum ketika nilai pixelnya berada di spektrum warna sangat gelap atau sangat terang. Berdasarkan kedua parameter tersebut, kemudian dilakukan klasifikasi. Klasifikasi dilakukan pada data SSS Bontang dan Batam yang memiliki karakter permukaan dasar laut yang sangat berbeda.Hasil klasifikasi dengan image processing memperlihatkan pola sebaran tekstur sedimen masing-masing terdiri dari 4 (empat) kelas baik untuk Batam atau Bontang. Pada area Bontang teridentifikasi sedimen sangat halus yang berasosiasi dengan intensitas dan entropy rendah - zona gelap pada gray scale image dan sedimen kasar yang berasosiasi dengan intensitas dan entropy tinggi - zona terang pada gray scale image. Karakter yang sama juga teramati pada area Batam, yaitu teridentifikasi sedimen halus (berasosiasi dengan intensitas rendah) - sedimen kasar (intensitas tinggi). Namun, berbeda dengan di Bontang, di Batam nilai entropi menunjukkan nilai yang sebaliknya, yaitu nilai tinggi berkorelasi dengan sedimen halus, dan sebaliknya. Hal ini diperkirakan akibat keberadaan batuan dan struktur sedimen.Kata Kunci: Side Scan Sonar, Intensitas, Hambur balik dan Entropi.
Reservoir Characterization Using Acoustic Impedance Inversion and Multi-Attribute Analysis in Nias Waters, North Sumatra Fathkhurozak Yunanda Rifai; Tumpal Bernhard Nainggolan; Henry Munandar Manik
BULLETIN OF THE MARINE GEOLOGY Vol 34, No 1 (2019)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (3136.168 KB) | DOI: 10.32693/bomg.34.1.2019.637

Abstract

Seismic method is one of the most frequently applied geophysical methods in the process of oil and gas exploration. This research is conducted in Nias Waters, North Sumatra using one line 2D post-stack time migration seismic section and two wells data. Reservoir characterization is carried out to obtain physical parameters of rocks affected by fluid and rock lithology. Seismic inversion is used as a technique to create acoustic impedance distribution using seismic data as input and well data as control. As final product, multi-attribute analysis is applied to integrate of inversion results with seismic data to determine the lateral distribution of other parameters contained in well data. In this research, multi-attribute analysis is used to determine the distribution of NPHI as a validation of hydrocarbon source rocks. In that area, there is a gas hydrocarbon prospect in limestone lithology in depth around 1450 ms. Based on the results of sensitivity analysis, cross-plot between acoustic impedance and NPHI are sensitive in separating rock lithology, the target rock in the form of limestone has physical characteristics in the form of acoustic impedance values in the range of 20,000-49,000 ((ft/s)*(g/cc)) and NPHI values in the range of 5-35 %. While the results of the cross-plot between the acoustic impedance and resistivity are able to separate fluid-containing rocks with resistivity values in the range about 18-30 ohmm. The result of acoustic impedance inversion using the model based method shows the potential for hydrocarbons in the well FYR-1 with acoustic impedance in the range 21,469-22,881 ((ft/s)*(gr/cc)).
Delineation of Sedimentary Subbasin and Subsurface Interpretation East Java Basin in the Madura Strait and Surrounding Area Based on Gravity Data Analysis Imam Setiadi; Budi Setyanta; Tumpal Bernhard Nainggolan; Joni Widodo
BULLETIN OF THE MARINE GEOLOGY Vol 34, No 1 (2019)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (8350.009 KB) | DOI: 10.32693/bomg.34.1.2019.621

Abstract

East Java basin is a very large sedimentary basin and has been proven produce hydrocarbons, this basin consists of several different sub-basins, one of the sub-basin is in the Madura Strait and surrounding areas. Gravity is one of the geophysical methods that can be used to determine geological subsurface configurations and delineate sedimentary sub-basin based on density parameter. The purposes of this study are to delineate sedimentary sub-basins, estimate the thickness of sedimentary rock, interpret subsurface geological model and identify geological structures in the Madura Strait and surrounding areas. Data analysis which used in this paper are spectral analysis, spectral decomposition filter and 2D forward modeling. The results of the spectral analysis show that the thickness of sedimentary rock is about 3.15 Km. Spectral decomposition is performed at four different wave numbers cut off, namely (0.36, 0.18, 0.07 and 0.04), each showing anomaly patterns at depth (1 Km, 2 Km, 3 Km and 4 Km). The sub-basins that can be delineated from the gravity data analysis are 10 sedimentary sub-basins, while the structural patterns identified are basement high, graben and fault. 2D modeling results indicate that the basement is a continental crust with a mass density value of 2.7 gr/cc. Sedimentary rock from modeling result consecutively from the bottom to up, the first is Paleogene sedimentary rock with mass density value of 2.4 gr/cc and above this layer is Neogene sedimentary rocks with mass density values of 2.25 gr/cc. The results of the subsurface geological modeling analysis show that based on the graben pattern and the basement high of the East Java basin in the Madura Strait and surrounding areas there are many structural patterns that support the development of petroleum systems like at the western part of the East Java basin that have already produced hydrocarbon.Keywords : Gravity, spectral analysis, spectral decomposition filter, 2D Modeling, East java basin Cekungan Jawa Timur merupakan cekungan sedimen yang sangat besar dan telah terbukti memiliki kandungan minyak dan gas bumi. Cekungan ini terdiri atas beberapa sub-cekungan yang berbeda-beda, salah satunya adalah sub-cekungan yang ada pada wilayah selat Madura dan sekitarnya. Gayaberat merupakan salah satu metoda geofisika yang dapat digunakan untuk mengetahui konfigurasi bawah permukaan serta mendelineasi sub-cekungan sedimen berdasarkan parameter rapat massa (densitas). Tujuan dari penelitian ini adalah untuk mendelineasi sub-cekungan sedimen, memperkirakan ketebalan sedimen, menginterpretasi geologi bawah permukaan serta mengidentifikasi struktur yang ada pada wilayah selat madura dan sekitarnya. Analisis data yang digunakan yaitu analisis spektral, filter spektral dekomposisi serta pemodelan maju (forward modeling) 2D. Hasil analisis spektral menunjukaan bahwa tebal batuan sedimen rata-rata adalah sekitar 3.15 Km. Spektral dekomposisi dilakukan pada empat bilangan gelombang cuttoff yang berbeda beda yaitu (0.36, 0.18, 0.07 dan 0.04) yang masing-masing menunjukkan pola anomali pada kedalaman (1 Km, 2 Km, 3 Km dan 4 Km). Sub-cekungan yang dapat didelineasi dari analisis data gayaberat ini adalah sebanyak 10 sub-cekungan sedimen, sedangkan pola struktur yang teridentifikasi yaitu berupa tinggian, graben dan patahan. Hasil pemodelan 2D menunjukkan bahwa batuan dasar adalah berupa kerak kontinen dengan nilai rapat massa 2.7 gr/cc. Batuan sedimen hasil pemodelan secara berturut turut dari bawah ke atas yang pertama yaitu batuan sedimen yang berumur Paleogen dengan nilai rapat massa 2.4 gr/cc dan di atasnya adalah batuan sedimen berumur Neogen yang mempunyai nilai rapat massa 2.25 gr/cc. Hasil analisis model bawah permukaan menunjukkan bahwa berdasarkan pola graben dan tinggian cekungan Jawa Timur segmen selat Madura dan sekitarnya cukup banyak terdapat pola struktur yang mendukung berkembangnya petroleum system seperti pada wilayah sebelah barat cekungan Jawa Timur yang sudah berproduksi hidrokarbon.Kata Kunci : Gayaberat, spektral analisis, filter spektral dekomposisi, pemodelan 2D, Cekungan Jawa Timur
Combined Multiple Attenuation Methods and Geological Interpretation : Seram Sea Case Study 2D Marine Seismic Data Tumpal Bernhard Nainggolan; Said Muhammad Rasidin; Imam Setiadi
BULLETIN OF THE MARINE GEOLOGY Vol 34, No 1 (2019)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (6771.046 KB) | DOI: 10.32693/bomg.34.1.2019.622

Abstract

Multiple often and always appear in marine seismic data due to very high acoustic impedance contrasts. These events have undergone more than one reflection. This causes the signal to arrive back at the receiver at an erroneous time, which, in turn, causes false results and can result in data misinterpretation. Several types of multiple suppression have been studied in literature. Methods that attenuate multiples can be classified into three broad categories: deconvolution methods; filtering methods and wavefield prediction subtraction methods. The study area is situated on Seram Sea in between 131°15’E – 132°45’E and 3°0’S – 4°0’S, Seram Trough which is located beneath Seram Sea at northern part of the Banda-Arc – Australian collision zone and currently the site of contraction between Bird’s Head and Seram. This research uses predictive deconvolution and FK-filter to attenuate short period multiple from their move out, then continued by SRME method to predict multiple that cannot be attenuated from previous method, then followed by Radon transform to attenuate multiple that still left and cannot be attenuated by SRME method. The result of each method then compared to each other to see how well multiple attenuated. Predictive deconvolution and F-K filter could not give satisfactory result especially complex area where multiple in dipping event is not periodic, SRME method successfully attenuate multiple especially in near offset multiple without need subsurface information, while SRME method fails to attenuate long offset multiple, combination of SRME method and Radon transform can give satisfactory result with careful selection of the Radon transform parameters because it can obscure some primary reflectors. Based on geological interpretation, Seram Trough is built by dominant structural style of deposited fold and thrust belt. The deposited fold and thrust belt has a complexly fault geometry from western zone until eastern of seismic line.
A First Record of Metal Fractionation in Coastal Sediment from Ambon Bay, Moluccas, Indonesia Lestari Lestari; Fitri Budiyanto; Corry Yanti Manullang
BULLETIN OF THE MARINE GEOLOGY Vol 34, No 1 (2019)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (1392.32 KB) | DOI: 10.32693/bomg.34.1.2019.570

Abstract

Five metals in sediment samples at seven sites from the Ambon Bay were analyzed with BCR sequential extraction procedure to determine chemical fractionation of metals and to assess bioavailability of metals with Risk Assessment Code (RAC). The result showed that the percentages of cadmium (100%), lead (82.6-97.08%) and zinc (41.68-76.33%) were mostly accumulated in the non-residual (F1+F2+F3) fraction of the total concentrations. While the copper percentages (44.74-78.91%) and nickel (59.71-74.16%) were mostly accumulated in residual (F4) fraction of the total concentrations. The Risk Assessment Code (RAC) reveals that cadmium, copper, nickel and zinc at locations exist in acid soluble (exchangeable) fraction and therefore, they are in low until very high risk category meanwhile there is no Pb at locations exist in acid soluble (exchangeable) fraction. 

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