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INDONESIA
Bulletin of Geology
ISSN : 25800752     EISSN : 25800752     DOI : 10.5614/bull.geol.
Bulletin of Geology is a research-based periodical scientific open access journal published by Faculty of Earth Sciences and Technology, Institut Teknologi Bandung (ITB). The published article in Bulletin of Geology covers all geoscience and technology fields including Geology, Geophysics, Geodesy, Meteorology, Oceanography, Petroleum, Mining, and Geography. The submitted abstract must be written in English and Bahasa Indonesia, but the article content is English or Bahasa Indonesia.
Articles 5 Documents
Search results for , issue "Vol 1 No 2 (2017): Bulletin of Geology" : 5 Documents clear
ANALYZING SURFACE ROUGHNESS MODELS DERIVED BY SAR AND DEM DATA AT GEOTHERMAL FIELDS Tahjudil Witra; Asep Saepuloh; Agung Budi Harto; Ketut Wikantika
Bulletin of Geology Vol 1 No 2 (2017): Bulletin of Geology
Publisher : Fakultas Ilmu dan Teknologi Kebumian (FITB), Institut Teknologi Bandung (ITB)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/bull.geol.2017.1.2.1

Abstract

Surface roughness is a physical property which is used in many applications such as hydrological analyses, erosivity of rocks, and identification of geothermal surface manifestations. In this study, the surface roughness was calculated by a pin-meter. This tool is expected be able to measure the fragmental size at ground surface. However, there is a possibility that the tool still has some errors from the effect of topography undulation. In previous research, detrending method was used to minimise the topographical effect in the measured surface roughness. In this paper, we used Synthetic Aperture Radar (SAR) data from Sentinel-1A, and Digital Elevation Model (DEM) SRTM to evaluate the effectiveness of detrending method of pin-meter. Therefore, the measured surface roughness originated solely from fragmental materials. The selected research areas were Wayang Windu and Patuha geothermal field in Indonesia. Modelling the surface roughness by Sentinel-1A image was conducted by utilising backscattering coefficient and local incidence angle. While surface roughness model from DEM is formed by the Root mean square (RMS) for each grid with the optimum size 19×19 pixels. Both models were compared to pin-meter data which have been detrended. Then, the comparison was analyzed based on determination correlation value (R2). Surface roughness model derived by Sentinel-1A produced R2 about 0.1130 higher than DEM about 0.060. It might indicate that the surface roughness measured by the pin-meter following detrending process is free from the effect of topography undulation. Then, surface roughness model derived by Sentinel-1A data was used to identify surface manifestation. Analysis was performed based on pH measurement at field and scatter plot pattern. According to the selected model, the surface roughness at geothermal surface manifestation zones are inversely proportional to the soil pH.
ANALISIS MEKANISME TERJADINYA TEKANAN-LUAP DAN PREDIKSI TEKANAN PORI PADA LAPANGAN BD, CEKUNGAN JAWA TIMUR Ryan Surjaudaja; Agus Mochamad Ramdhan; Indra Gunawan
Bulletin of Geology Vol 1 No 2 (2017): Bulletin of Geology
Publisher : Fakultas Ilmu dan Teknologi Kebumian (FITB), Institut Teknologi Bandung (ITB)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/bull.geol.2017.1.2.2

Abstract

The East Java Basin is one of the sedimentary basins with proven petroleum system and very prospective as an exploration target. However, drilling in this basin is a risky operation because of the presence of overpressure, which is shown by kick and lost during exploration wells drilling in BD Field as an example. Drilling problems and drilling risks can be reduced by doing overpressure study, including overpressure generating mechanism, pore pressure prediction, and estimation top of overpressure. The temperature in this field can reach 80°C at the depth around 1500 m SSTVD. However, the Dutta-Katahara crossplot does not indicate any diagenesis of smectite to illite. It is also confimed by XRD data in one of the well, which shown domination of kaolinitic clay mineral. Based on the vitrinite reflectance data, there is no transformation of kerogene to hydrocarbon in this field. The burial history plot shows rapid sedimentation with the rate of 1723 m/million years. Based on those criterias, the main overpressure generating mechanism is interpreted to be loading mechanism. High sedimentation rate is related to the peak inversion in Plio-Pleistocene time, providing abundant of sediment supply into the basin. Pore pressure in this field can be estimated by using sonic data with Eaton’s method. Both direct and indirect pressure measurements, combine with drilling data are used to support this estimation. Based on well data, top of overpressure in this field is located at the depth around 1500-1600 m SSTVD. The top of overpressure is located within Lidah Formation.
TEKTONOSTRATIGRAFI DAN SIKUEN STRATIGRAFI ENDAPAN LISU BLOK DUYUNG, CEKUNGAN NATUNA BARAT Ariyani Rachmad; Djuhaeni Djuhaeni; Prihadi Sumintadireja
Bulletin of Geology Vol 1 No 2 (2017): Bulletin of Geology
Publisher : Fakultas Ilmu dan Teknologi Kebumian (FITB), Institut Teknologi Bandung (ITB)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/bull.geol.2017.1.2.3

Abstract

Duyung Block is located in the Natuna Sea and geologically is the part of West Natuna Basin. The area of research is the 3D seismic area, part of Duyung Block, covering approximately 412 square kilometers. This study aims to determine the stratigraphy of syn-rift deposition in Duyung Block to understand the distribution and seismic facies at the depth interval of syn-rift. Seismic facies map is generated based on seismic geomorphology analysis using stratal slice method with displaying CWT (Continuous Wavelet Transform) seismic attribute. Based on lithostratigraphy correlation and the information from AA-1X and Forel-2 wells, syn-rift sediment were deposited within a supratidal, fresh water, predominantly lacustrine. The analysis of seismic geomorphology with stratal slices in the area of research encountered three depositional systems in the area of syn-rift, i.e., fluvial deltaic, shallow lacustrine and deep lacustrine. Rift depositional system in the study area can be divided into four tectonostratigraphy phases, i.e., Early Rift, Middle Rift, Late Rift and Early Post-rift. The boundary between tectonostratigraphy phases is determined from the analysis of seismic expression. Based on the analysis of seismic-sequence stratigraphy, syn-rift depositional system can be divided into 3 sequence packages, i.e., Sequence-1 (interval SB0-SB1), Sequence-2 (interval SB1-SB2) and Sequence-3 (interval SB2-SB3). Generally in the area of research, the tectonostratigraphy boundaries are relatively coincide with the sequence boundaries, but toward bonding fault-rift, the difference between those two are increasingly visible.
PREDIKSI TEKANAN PORI DENGAN DATA SEISMIK 3D DAN DATA LOG SUMUR MENGGUNAKAN METODE EATON (STUDI KASUS DI CEKUNGAN BONAPARTE UTARA) Tatang Juhatta; Agus Mochamad Ramdhan; Fatkhan Fatkhan
Bulletin of Geology Vol 1 No 2 (2017): Bulletin of Geology
Publisher : Fakultas Ilmu dan Teknologi Kebumian (FITB), Institut Teknologi Bandung (ITB)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/bull.geol.2017.1.2.4

Abstract

Pore pressure prediction has important implications in determining the success of drilling activities. This thesis discusses pore pressure prediction in the northern Bonaparte Basin using wireline log data and 3D seismic interval velocity. The Eaton method is used to predict pore pressure in wells and to construct 3D model of pore pressure. Eaton method is used for pore pressure prediction, overpressure mechanism in the well and 3D model of pore pressure. Pore pressure prediction is determined by effective stress value that is obtained by the analysis of interval check-shot velocity, hydrostatic pressure is assumed to follow the gradient of 0.43 psi/ft and overburden pressure is obtained from density log data. Pore pressure prediction in 3D model is determined from 3D model of effective stress that is generated from average NCT of interval velocity of each well, the hydrostatic pressure is assumed to follow the gradient of 0.43 psi/ft and 3D model of pressure overburden generated from the 3D model density that is obtained from model 3D interval velocity by the result of Gardner transformation. The analyses of pore pressure in the well and 3D model indicate that overpressure occurs in Wangarlu Formation at the depth interval of 2000-2300 m, then it gradually reaches hydrostatic pressure in the Plover Fm. at the depth interval of 3750-3900m. Overpressure is generated by disequilibrium compaction meaning that sediments fail to compact because the expulsion of pore water is inhibited. Compression tectonic activity that occurred in the late Miocene in the north, probably contributes to increase in lateral stress that produces overpressure that spreading laterally to the south of the study area. The results of this study can be applied in the planning of drilling wells including casing design and estimation of mud weight in each depth interval that will be used during drilling.
METODE SEISMIC PORE PRESSURE UNTUK PENYEBARAN TEKANAN LUAP DI BLOK ARU, CEKUNGAN SUMATRA UTARA Jihan Cessar H. Gurning; Agus Mochamad Ramdhan
Bulletin of Geology Vol 1 No 2 (2017): Bulletin of Geology
Publisher : Fakultas Ilmu dan Teknologi Kebumian (FITB), Institut Teknologi Bandung (ITB)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/bull.geol.2017.1.2.5

Abstract

The North Sumatra Basin is one of the Tertiary back-arc basins which has been explored since the colonial era. The existence of overpressured zone has already been recognized. This is due to the existence of shale or claystone sequence that is capable to generate overpressure condition. Therefore, the understanding and knowledge of pore pressure and the mud weight used to counter the pressure are of paramount importance. The approach used to define pore pressure value with Eaton empirical method is generally done on wells only. In this research, determination of lateral pore pressure distribution is done with the seismic image and seismic interval velocity data. Wireline log and seismic interval velocity data are both being integrated to generate the pore pressure estimation and the distribution of overpressured zone in the North Sumatra Basin. The overpressure in this research area is caused by non-loading mechanism with the transformation of smectite into illite. The top of overpressure generally follows stratigraphic layer and sometimes it crosses the stratigraphic layer.

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