46 research outputs found
Application of Spectral Decomposition and RGB Blending for Delineation of “S” Channel At Asri Basin
Get PDFGita member is part of Talang Akar Formation is known as hydrocarbon reservoir at Asri Basin, eastern part of South Sumatra. This formation consists of several depositional systems such as braided channel, meandering channel, fluvial-deltaic, and estuarine system. A channel system was an interesting system developed in the Asri Basin, however, to get the channel distribution in Asri Basin is quite challenging because the thickness of the channels caused its appearance is generally close or under seismic resolution, the existence of coal below our target also affects the impression of “S” sand on seismic data. In this study, spectral decomposition and RGB Blending have been successful to identify “S” sand. RGB Blending map is extracted from 15 Hz as low frequency, 45 Hz as middle frequency, and 75 Hz as high frequency. Our interpretation was applied at RGB Blending map and reveal the “S” sand is classified as a meandering channel depositional system with the main direction of the channel is Northeast – Southwest.Keywords: spectral decomposition, RGB Blending, Gita reservoir, Asri Basin: Anggota Gita merupakan bagian dari Formasi Talang Akar yang dikenal sebagai reservoar hidrokarbon di Cekungan Asri, Sumatra Selatan bagian timur. Formasi ini terdiri dari beberapa sistem pengendapan seperti sistem sungai teranyam, meander, fluvial-delta, dan estuari. Sistem pengendapan sungai purba di Cekungan Asri merupakan sistem yang menarik untuk dieksplorasi namun untuk mendapatkan persebaran sungai tersebut merupakan hal yang menantang dikarenakan tipisnya ketebalan sungai yang mengakibatkan kenampakannya pada data seismik berada disekitar atau bahkan dibawah resolusi seismik, keberadaan lapisan batubara dibawah target turut mempengaruhi kenampakan pasir “S” pada data seismik. Dekomposisi spektral serta RGB Blending yang diaplikasikan pada penelitian ini dapat mengidentifikasi pasir “S”. Peta RGB Blending diekstraksi dari beberapa frekuensi, yaitu frekuensi 15 Hz yang diambil sebagai frekuensi rendah, 45 Hz sebagai frekuensi tengah, dan 75 Hz sebagai frekuensi tinggi. Selanjutnya dilakukan interpretasi pada peta hasil RGB Blending dan menunjukkan pasir “S” diklasifikasikan sebagai sungai dengan sistem meander dengan arah utama sedimentasi adalah Timurlaut - Baratdaya.Kata kunci: dekomposisi spektral, RGB Blending, reservoar Gita, Cekungan Asri
A SUCCESS CASE OF WIDURI AREA REJUVENATION, ASRI BASIN, OFFSHORE SE SUMATRA BLOCK, INDONESIA
Get PDFINTA/B Field is one of the most producing mature fields in Widuri Area, Asri Basin, Offshore SE Sumatera, Indonesia, therefore it is subjected to rejuvenation to enhance hydrocarbon production. INTA/B Field is distinguished from other fields from its featured anticlinal structures that have the northeast-southwest trending. This structure is heavily faulted mainly in the up-thrown south side of a major normal fault. Two structural configurations with various oil-water contact have successfully been identified within the field. The most of oil reserves are preserved in the western lobe in which Intan-1 sands. One of the most important reservoirs in this field is Talangakar (TAF) sand deposited as a meandering river system that streamed from the northwest to the southeast within the basin. Two main reservoirs, Gita-34A and Gita-34B are correlated throughout the field and interpreted as Miocene fluvio-channel sands. These two channels are thickened moderately from southwest to northeast which has descriptions as follows: fine- to-coarse grains, unconsolidated to friable, and low cementing materials.INTA/B Field has been produced for 25 years and currently undergoing a watered-out phase. Therefore, an integrated study is subjected to overcome this issue for mature field rejuvenation. The integrated study ranged from geology (e.g., depositional environment and facies analysis), geophysics (e.g., revisiting and reprocessing of seismic attributes), petrophysical calculation, and reservoir engineering (e.g., water conformance plot and volumetric calculation).This integrated study has successfully rejuvenated a mature field resulting and added a significant number in oil production with an average of 300 BPOD/well. The extended project is estimated to have a similar result to the forward pilot
The origin of Cihara granodiorite from South Banten
Get PDFhttp://dx.doi.org/10.17014/ijog.vol3no2.20085Petrographical and geochemical characteristics of the Late Oligocene Cihara Granodiorite from South Banten are presented. Data show that the rock was originated from magma of a continental origin formed at a subduction zone environment. Fractional crystallization involving plagioclase, hornblende, pyroxene, and magnetite was the main process responsible for the geochemical variation of the rocks from the Cihara Granodiorite. There are two possibilities of parental magmas to the Cihara Granodiorite, i.e. the basaltic/ or andesitic magma of the Cikotok Formation or crustal melting magma from a subduction process. Some trace element data of the basaltic rocks from the Cikotok Formation are needed to support the first interpretation. Alternatively, heating of the Jawa lower crust by magma from either mantle or subducted slab melting caused the crustal melting to produce intermediate parent magma. Some degree of mixing between those two differ- ent magma sources during the fractionation may be involved in the petrogenesis. </p
Characterization of Basement Fracture Reservoir in Field ‘X', South Sumatera Basin, Based on the Analysis of Core and FMI Log
Get PDFBasement reservoir is a reservoir that is located in the basement rock, comprised of either igneous rock or metamorphic rock that has secondary porosity, resulting in its capability to store oil and gas. The research was conducted at field 'X' that is located at South Sumatra basin and it is a part of Jambi Sub-Basin. The study was focused on discussing hydrocarbon potential in Fields 'X', particularly at the basement metamorphic rock. The study was conducted at two wells in the field. The secondary porosity system of the basement is fracture porosity. Fracture analysis as secondary porosity system was performed on two wells, HA-1 and HA-2, by using FMI log interpretation. Based on the analysis of fracture on HA-1 well, the trend of fracture system is Northeast - Southwest (NE-SW) with a fracture porosity of 1.49%. On a different note, the trend of fracture system on HA-2 wells is East Northeast - West Southwest (ENE-WSW) with a fracture porosity of 0.888%. The effect of rock properties itself has little influence on the number of fractures as opposed to the effect of surrounding tectonic forces. The fractures are controlled by geological structures following Jambi pattern that has an orientation of Northeast - Southwest (NE-SW). Although the fracture porosity is relatively small, it is enough to storing hydrocarbons in economical quantity
The Transitional Gabbroic Rocks in Bayah Geological Complex, Western part of Java, Indonesia, Inferred from XRF, ICP-MS, and Microprobe Analysis
Get PDFGabbro, is a fossil remnant of oceanic crust in western part of Java, found at Bayah Geological Complex (BGC) and Ciletuh Melange Complex (CMC), Indonesia. It has been studied by using petrographic, X-Ray Fluorescence (XRF), and inductively coupled plasma-mass spectrometry (ICP-MS) and mineralogical (microprobe) analyses. Mineral and geochemical composition of these rocks provide important clues to their origins since the rocks have been deformed and gone through auto metamorphism, beside they contain the economic mineral and or rare earth elements (REE). Gabbroic rocks in these two areas generally shows phaneritic to porphyritic texture, granular texture. These rocks in CMC are dominated by plagioclase (oligoclase to albite), hornblende, pyroxene, partly altered to tremolite, actinolite, chlorite, epidote, and sericite; meanwhile those of BGC dominantly consist of plagioclase, pyroxene, hornblende, some present of chlorite, actinolite, epidote and biotite as secondary minerals. In multi-element diagrams, gabbroic rocks in CMC show strong negative Sr and Zr, but positive Nb anomaly, while those of BGC show strong negative anomaly of Nb and Zr. In addition, based on rare earth elements (REE) diagrams, gabbroic rocks in CMC show depleted of light rare earth elements (LREE) with negative Eu anomaly, while gabbro’s in BGC show enrichment of LREE. These characteristics indicate that GBC’s and CMC’s gabbroic rocks came from different magma sources, one was formed by partial melting of depleted upper mantle reservoir while the other one was formed by partial melting of mantle wedge with active participation of subducted slab in an arc tectonic setting, suprasubduction zone which were formed at started Upper Cretaceous to Paleogene, and they had retrograde metamorphism to epidote amphibolite facies
Petrology, Geochemistry and K-Ar Dating of Metamorphic Rock in Ciletuh Mélange Complex, West Java Indonesia
Get PDFThe Ciletuh Mélange Complex in West Java, Indonesia, provides evidence of early Cenozoic subduction. This study aims to investigate the stratigraphic position, geological structure, metamorphic facies, and protoliths of the metamorphic rock units. The research methods employed geological mapping, petrology, and geochemical analysis. The samples collected exhibit different facies, including zeolites, greenschist, and epidote amphibolite. Protoliths consist of metasedimentary rocks such as metapellites, metapsammitics, meta-calcilates, and ortho-metamorphs such as metagabbro and metabasalt. Retrograde metamorphism, indicated by epidote, chlorite, and calcite in amphibolite schists, suggests lower temperature stress conditions. Hydrothermal changes are evidenced by some samples’ occurrence of quartz and calcite veins. Geochemical analysis reveals that the provenance of metasedimentary rocks originated from a volcanic arc, while the metabasalt rock originated from an island arc tectonic environment. K-Ar dating indicates an age range of 55.2 - 37.8 million years ago, corresponding to the Early to Late Eocene. These metamorphic rocks are believed to have formed through regional metamorphism due to island arc subduction and the formation of accretionary prisms. Retrograde metamorphism signifies uplift or accretion processes after tectonic activit
SEBARAN PASIR LAUT SEBAGAI BAHAN GALIAN DI LEPAS PANTAI SELAT RIAU
Get PDFDaerah penelitian terletak di perairan antara Pulau Batam dan Pulau Bintan (Selat Riau), termasuk ke dalam wilayah Kotamadya Batam dan Kabupaten Bintan, Provinsi Kepulauan Riau. Metode penelitian yang dilakukan adalah pengambilan posisi (navigasi), pengukuran kedalaman dasar laut, pengamatan dan pengambilan contoh sedimen pantai, pengambilan contoh sedimen dasar laut, serta analisis laboratorium. Tujuan penelitian adalah untuk mengetahui sebaran pasir pasir laut, serta ketebalannya berdasarkan karakteristik ukuran butirannya, agar potensi bahan galian tersebut dapat diketahui. Berdasarkan analisis ukuran butir sedimen di pantai Pulau Batam dan Pulau Bintan diketahui berukuran pasir, kerikil pasiran, pasir kerikilan dan lanau pasiran, sedangkan sebaran sedimen dasar laut terdiri dari: kerikil pasiran, pasir kerikilan, pasir, pasir lanauan dan lanau pasiran. Kedalaman sedimen pasir di pantai Pulau Batam antara 1 meter sampai 2,6 meter, sedangkan ketebalan sedimen pasir di Pulau Bintan antara 0,6 meter sampai 2 meter. Kata Kunci: sedimen, ukuran butir, pasir, bahan galian, Selat RiauThe study area is located in offshore area between Batam and Bintan Islands (Riau Strait), including of Batam and Bintan regency, Kepulauan Riau Province. The research methods carried out were position taking (navigation), depth of seabed measurement (bathymetry), observation and coastal sediments sampling, seabed sediments sampling, and laboratory analysis. The objectives of the study is to know the sand beach and sea sand distribution and its thickness based on characteristics of grain size, as well as to know those construction materials. Based on sediment grain size analysis on the Batam and Bintan islands, sand beach consists of: sand, sandy gravel, gravelly sand and sandy silt, while seafloor surficial sediments distribution consist of sandy gravel, gravelly sand, sand, silty sand and sandy silt. The depth of sand sediment on Batam beach is between 1 to 2.6 meters, while the depth of sand sediment in Bintan Island coastal is between 0.6 meters to 2 meters. Keywords: sediment, grain size, sands, substrate material, Riau Strai
The Characteristics of Lahar in Merapi Volcano, Central Java as the Indicator of the Explosivity during Holocene
Get PDFDOI: 10.17014/ijog.v6i2.116Merapi Volcano in Central Java has been the most active volcano during Holocene time. As a strato volcano, Merapi exhibits alternating volcanic activities of effusive and explosive characters and self destruction. The explosivity index has evolved during the last ten thousand years. The effusive activities were characterized by the occurrence of lava flows, the development of lava dome, and the production of the “nuee ardente d’avalanche” called Merapi type. The explosive stage is frequently accompanied by the occurence of pyroclastic flows. The present investigation is attempted to reveal the relationship between the characteristics of lahar and the evolution of the activity of Merapi Volcano. The quantitative analysis was focused on the size and shape of the lahar components particularly that of pumice as the main indicators in 73 measured stratigraphic columns of lahar deposits. In addition, the main chemical element rim structures of hornblende identified in lahar components indicate the different lahar units. There are five lahar units and five groups of Merapi activities which can be distinguished. It can be concluded that the characteristics of lahar reflect the evolution of the activities in the past. The risk analyses of Merapi Volcano therefore can be enlarged to cover the possible hazard based on the lahar characteristics.</p
Gumuk gunung api purba bawah laut di Tawangsari - Jomboran, Sukoharjo - Wonogiri, Jawa Tengah
Get PDFhttp://dx.doi.org/10.17014/ijog.vol3no1.20084This paper discusses the study on the basalt volcanic rocks and the volcano morphology indicating the existence of an ancient submarine volcano in Tawangsari-Jomboran sub-regency, Sukoharjo- Wonogiri, Central Java. In general, this basalt volcanic rocks were identified as andesite breccia which might be grouped into the Mandalika Formation of Oligosen-Miosen age (Surono et al., 1992). The origin of the Mandalika Formation in relation to the classic sedimentation process and the submarine volcanism is still needed to be evaluated. The present study was based on the detailed descriptions of the rocks both in the field and in the laboratory. The autoclastic basalt outcrops consisting of breccias show the characteristics of the igneous rock fragment component embedded in the groundmass with the same composition, namely igneous rock, dark grey to black in colour; porphyritic texture, rough surface, brecciated; pillow structures, massive, fine vesicularities, amygdaloidal filled with calcite, and radial fractures; calk-alkaline andesite composition ( SiO = 54.71% , K O = 1.15% ). This rock body attains the dimension of 2 - 5 m length, and 40 cm - 1 m in diameter with the direction of the deposition varies following the direction of the eruption source. Brecciated structures on the surface was controlled by the high cooling rate and the low flow, while the interior of the rock is massive because it was not in a direct contact to the cooler mass outside. Autoclastic basalt breccias and or the pillow basalt lava was interpreted to be formed by the undulating low gradient of morphology with the average angle of <10o. On the other hand, the low basaltic magma viscosity produced the effusive eruption related to the formation of the low angle morphology. The distance between the hills generally composed of pillow basalt is between 500 m - 1 km. The typical pillow structure of the igneous rock as described above is interpreted to be the product of the lava flow related to the effusive eruption from a submarine volcano located under or close to the seawater surface. </p
PENGARUH TEMPERATUR DAN UKURAN BUTIR TERHADAP KELARUTAN KALIUM PADA BATUAN LEUSITIK GUNUNG MURIA JAWA TENGAH
No full textMineral yang berpotensi di bidang pertanian sebagai sumber unsur hara (pupuk) yang dibutuhkan tanaman adalah dolomit, batuan fosfat, dan mineral silikat seperti leusit, muskovit dan ortoklas. Leusit mengandung kalium dan aluminium tektosilikat K(AlSi2O6). Mineral ini dijumpai di Kabupaten Jepara, Pati dan Kudus. Di Medani, Jepara potensinya sebanyak 190.400.000 ton, kandungan K2O antara 1,92-8,77 %. Mineral leusit untuk penelitian ini mempunyai kadar K20 antara 7,68-7,98 %; Al2O3 19,62-20,73 % dan SiO2 48,62-49,93 %. Hasil analisis petrografi menunjukkan adanya fenokris yang terdiri dari leusit, sanidin dan mineral opak. Unsur kalium di dalam leusit sulit larut, sehingga perlu diupayakan peningkatan kelarutannya dengan cara memanaskan batuan mengandung leusit tersebut pada suhu 600-1000 °C dan penghalusan ukuran butiran dari -70 sampai -200 mesh. Sebagai pembanding digunakan percontoh tanpa pemanasan. Dari hasil uji coba, kelarutan tanpa pemanasan relatif rendah antara 0,22-0,49 %; semakin halus butiran kelarutan leusit cenderung semakin meningkat, tetapi pada suhu 600 °C terjadi peningkatan cukup signifikan antara 1,55-2,30 %, pada suhu 700 °C kelarutan relatif tetap yaitu antara 1,44-2,40 %, sedangkan pada suhu 850 °C mulai terjadi penurunan kelarutan menjadi 1,20-1,95 % dan pada suhu lebih tinggi 1000 °C, kelarutan menurun menjadi 0,31-0,45 %. Percobaan peningkatan kelarutan kalium cukup signifikan sampai 10 kali, diharapkan kegunaan untuk pupuk lebih baik
